Unit 1: Cell Biology
1.1 Introduction to Cells
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Cell theory - all organisms are made up of >1 cells, the smallest unit of life
○ Individual cell can perform all functions of life; anything w/o cells (viruses) not living
○ Cells can only come from pre-existing cells
○ Fungi = exception, made of threads called hyphae, muscle fibers
Functions of life: metabolism, growth, response, homeostasis, nutrition, reproduction, excretion
Single celled organisms: Paramecium and Chlorella
Electron microscopes use a beam of electrons, not light, to produce an image
Magnification = image size/object size
Specialized structures, like folds/microvilli provide a larger surface area to increase activity
Differentiation: when cells take on specific functions. Involves certain gene expression
Cells form tissues, which form organs, which form organ systems, which work together
Stem cells are unspecialized, can divide and differentiate into several cell types (pluripotent)
Stargardt’s Disease = leads to macular degen., stem cells can become retina cells to help
1.2 Ultrastructure of Cells
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Living things are either eukaryotic or prokaryotic (smaller + simpler)
All bacteria = prokaryotes, prokaryotes thought to be first cells to have evolved
Prokaryotes have no nucleus or organelles, divide by binary fission
○ Cell wall of peptidoglycan, plasma memb. controls material movement, cytoplasm has
enzymes + genetic material, plasmid = DNA circle w/ no proteins, 70S ribosomes
(smaller) make proteins, flagellum movement, pili genetic exchange
Eukaryotes have a nucleus, have organelles (compartmentalization)
○ Nuclear envelope covers chromosome-housing nucleus, nucleolus makes ribosomes,
rough endoplasmic reticulum has ribosomes and makes proteins, which go to the golgi
apparatus in vesicles which package them. Smooth endoplasmic reticulum makes
phospholipids for membrane and lipids, mitochondria = site of aerobic respiration, 80S
ribosomes. Glycogen stored
○ Plant cells: cellulose/lignin/pectin cell wall, central vacuole, chloroplasts (site of phot.).
Chloroplasts and mitochondria have their own DNA. Starch stored
1.3 Membrane Structure
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Fluid mosaic model: 2 layers of phospholipids, which form a bilayer. Embedded in bilayer is
cholesterol makes membrane more rigid
○ Singer and Nicolson model
Integral proteins (embedded in bilayer), peripheral proteins (surface): many are glycoproteins like
binding sites
Phospholipids are made up of a polar, hydrophilic phosphate group+glycerol (head), and a
non-polar, hydrophobic fatty acid (tail)
1.4 Membrane Transport
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Simple diffusion through plasma membrane: passive, no energy, down a concentration gradient
Channel proteins (some gated/some open) allow large/charged particles to move through
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○ Interior is hydrophilic
Facilitated diffusion: carrier/channel proteins, down gradient, passive transport
Osmosis: type of diffusion of water across a partially permeable membrane to an area of higher
solute concentration
○ Hypotonic: low solute concentration outside cell, isotonic: equal, hypertonic: high conc.
Active transport: transporters use energy, up gradient
Exocytosis (export)/endocytosis (uptake) both use energy to transport molecules in bulk
○ Vesicle fuses w/ membrane vs pinching off to make vesicle
1.5 Origin of Cells
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Endosymbiotic theory explains how eukaryotic cells could have developed from a simple
cell/prokaryote
○ Organelles within eukaryotic cells were once prokaryotes, until engulfed by larger cells
○ Mitochondria and chloroplasts share many characteristics w/ prokaryotes
■ Both have ribosomes smaller than those of eukaryotes
■ Both have small circular pieces of DNA resembling plasmids
■ Both have their own envelope and replicate by binary fission
1.6 Cell Division
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Cell cycle:
○ Interphase (G1 phase, S phase - DNA replication, G 2 phase). Most of a cell’s life
○ Mitosis - separation and division of the chromosomes
■ Prophase: chromosomes condense + become visible (supercoiling), each
chromosome has two identical sister chromatids that are attached at the
centromere. Centrioles move to opposite sides/spindles form.
■ Metaphase: nuclear envelope breakdown, chromosomes line up in middle
■ Anaphase: sister chromatids pulled apart, each S.C. is a chromosome
■ Telophase: nuclear envelope forms, chromosomes uncoil
○ Cytokinesis - division of the cell into two daughter cells
Reproduction from mitosis = asexual reproduction
Cyclins = compounds that control cell cycle
○ G1 cyclins coordinate cell growth + start of a new cell cycle
○ G1/S cyclins start initial processes of DNA replication, promote centrosome duplication
○ S cyclins induce DNA replication
○ M cyclin influences formation of mitotic spindle + alignment of sister chromatids
Apoptosis: intentional cell death
Oncogenes = special genes with the potential to cause cancer (when cells from a primary tumor
migrate to other tissues and form a secondary tumor and genetic material is damaged)
Unit 2: Molecular Biology
2.1 Molecules to Metabolism
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4 most common elements in living organisms: carbon, hydrogen, oxygen, nitrogen
○ All in the four organic molecules: proteins, carbohydrates, nucleic acids, lipids
Any compound w/o carbon = inorganic
Carbohydrates - most abundant, source of energy, structural for plants also
○ Monosaccharides, disaccharides, polysaccharides
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Lipids are insoluble in water, and are energy storage molecules, higher energy content than carbs.
○ All lipids consist of fatty acids, which can be saturated (all C’s bonded to H) or
unsaturated (double/triple bonds + bent)
○ Types: triglycerides - glycerol + 3 fatty acids energy sources, phospholipids membranes, tail from 2 fatty acids + head from phosphate group & glycerol, steroids ring structure, some are hormones/membrane support
Protein - built from amino acids
Nucleic acids - DNA and RNA, vital to inheritance & development, built from nucleotides
(pentose sugar, organic nitrogenous base, phosphate group)
Anabolic reactions like condensation combine monomers → macromolecules, uses enzyme +
makes water
Digestion uses hydrolysis reactions, catabolic reactions break down
2.2 Water
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Water = polar, hydrogen bonds bc of H more + and O more Cohesion (network of water, xylem, surface tension) + adhesion (attraction to walls)
Lot of energy needed to breakdown H bonds, high specific heat capacity good for temp regulation
Water = universal solvent for other polar molecules
2.3 Carbohydrates and Lipids
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Monosaccharides: glucose, galactose, fructose; disaccharides: maltose, lactose, sucrose;
polysaccharides: starch + glycogen (storage), cellulose
Unsaturated fatty acids: cis (bent, missing H on same side) or trans (straight, opposite sides)
Saturated fat diet → coronary heart disease
2.4 Proteins
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Polypeptides synthesized by ribosomes in cytoplasm, 20 amino acids
Primary structure: sequence of amino acids in polypeptide chain, secondary structure (DNA):
folded amino acid chain, tertiary structure: 3D folding pattern, quaternary structure: ≥1 AA
chain
Heat/extreme pH disturbs protein bonds + destroys complex structure - denaturation
○ Protein primary structure remains, but secondary/tertiary/quaternary are lost
2.5 Enzymes
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Enzyme = proteins that are biological catalyst, speeds up chemical reactions
Remain unchanged after process, specific shape allows catalyzation of specific rxn
Active site of enzyme bonds w/ substrate (“lock and key”), enzyme-substrate complex
Enzyme activity affected by temperature, pH, substrate concentration
2.6 Structure of DNA and RNA
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DNA bases: adenine, guanine, cytosine, and thymine; RNA: A, G, uracil, thymine
DNA sugar + phosphate backbone, H bonds btwn bases
RNA has 5-carbon sugar ribose, instead of deoxyribose like in DNA
2.7 DNA Replication, Transcription, and Translation
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DNA replication takes place in the nucleus during interphase
○ DNA helicase unzips DNA double helix, breaking H bonds
○ Unpaired nucleotides = template for new strands, C w/ G and A w/ T
○ DNA polymerase link new nucleotides into place
Protein synthesis divided into transcription and translation (transcr. in nucleus + transl. in cyto)
Translation:
○ RNA polymerase unzips DNA
○ Free nucleotides move into place along one of the two strands
○ RNA polymerase places the free nucleotides, a strand of mRNA is formed, copying one
section (a gene)
○ RNA polymerase zips up DNA, mRNA separates from DNA + moves to cytoplasm
Transcription: process by which mRNA’s coded information is used to make proteins, carried out
by ribosomes and tRNA
○ Each sequence of three bases (codon) corresponds to a specific AA
○ Ribosome binds to mRNA and then draws in tRNA molecules w/ anticodons that match
the RNA codons
○ Each of the two tRNA molecules carries an amino acid
○ Anticodon + codon bind, amino acids bond (dipeptide)
○ First tRNA detaches, ribosome moves along mRNA to next codon, ends w/ stop codon
2.8 Cell Respiration
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The breakdown of nutrient molecules in a series of rxns that release energy in the form of ATP
Glycolysis: C6H12O6 (glucose) + 6O2 → 6CO2 + 6H2O + 38 ATP
○ Glucose (six-C sugar) present in cytoplasm is broken down by enzymes to produce 2
pyruvate (3-C sugar) and 2 ATP
If oxygen is present: aerobic respiration, anaerobic respiration without oxygen
○ Aerobic (mitochondria): link reaction - pyruvate lose CO2 & become acetyl CoA, Krebs
Cycle - acetyl CoA releases more CO 2, NAD + FAD reduced (NADH + FADH2), ATP
made, oxaloacetate = starting binding
○ Anaerobic (cytoplasm): pyruvate → lactate in animals, pyruvate → ethanol and CO2 in
yeast (fermentation)
2.9 Photosynthesis
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6CO2 + 6H2O → C6H12O6 + 6O2
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Chlorophyll, a green pigment in chloroplasts. Rate of photosynthesis lowest w/ green, high w/ red
& blue
Light-dependent reactions: chlorophyll absorbs light energy, ATP produced to split water into
hydrogen and oxygen (photolysis)
○ Oxygen = waste product, ATP/H +/electrons used in next stage
Light-independent reactions: CO2 from environment combines w/ hydrogen & ATP to form
organic molecules
Limiting factors on rate of photosynthesis: temperature, light intensity, carbon dioxide
concentration
Unit 3: Genetics
3.1 Genes
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Gene - a particular DNA section that, when transcribed + translated, forms a specific polypeptide
Allele - an alternate form of a gene found at a specific locus on a chromosome
Triplet of DNA bases → transcribed into mRNA codon → translated into a specific AA
Mutagens cause gene mutations
○ Insertion of an incorrect nucleotide is a base substitution mutation
Sickle-cell anemia caused from a single base substitution mutation in the gene for hemoglobin
3.2 Chromosomes
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Chromosomes are made of DNA molecules
Prokaryotic DNA: plasmids, no proteins; Eukaryotic: enclosed in nucleus, histone proteins
Homologous pairs: same length, carry same sequence of genes at the same locations (alleles can
be different). Diploid somatic cells have 23 homologous pairs
Coiled chromosomes from nuclei of dividing cells taken to see in a karyogram, autosome/sex ch
3.3 Meiosis
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Cell division that produces haploid gametes, reduction division from diploid
○ Prophase I: in interphase chromosomes are replicated, which now supercoil, homologous
pairs may exchange alleles during crossing over. Spindle microtubules form + nuclear
envelope breakdown
○ Metaphase I: chromosomes line up at equator, spindle attaches to centromeres, random
alignment of chromosomes
○ Anaphase I: microtubules contract towards opposite poles, homologous pairs separate,
chromosome number is halved from diploid to haploid
○ Telophase I: spindle breakdown, nuclear envelope forms, cytokinesis splits cells to have
one chromosome with two sister chromatids
○ Prophase II: spindle forms, chromosomes re-coil, nuclear envelope breaks down
○ Metaphase II: chromosomes line up at equator, spindle attaches to centromeres
○ Anaphase II: sister chromatids separate
○ Telophase II: nuclear envelopes form around the 4 haploid nuclei, chromosomes uncoil,
cytokinesis
Nondisjunction: failure of homologous pairs to separate properly, trisomy 21=Down syndrome
3.4 Inheritance
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Monohybrid crosses, dominant/recessive factors, Punnett squares
Codominance: both alleles have an effect on the phenotype - blood type
Sex-linked/X-linked characteristics, men can’t be carriers
Huntington’s disease - caused by a dominant allele (genetic disease)
Environmental factors like ionizing radiation, UV light, X-rays, and mutagenic chemicals are
mutagens which increase mutation rate
3.5 Genetic Modification and Biotechnology
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Polymerase chain reaction - makes millions of copies of tiny amounts of DNA to make a profile
Gel electrophoresis separates DNA fragments by applying an electric current. DNA is slightly
negative, so moves forward
○ Smaller fragments move further
Dolly the sheep = first successful clone
Unit 4: Ecology
4.1 Species, Communities and Ecosystems
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Ecosystem - all the groups of organisms living in an area, plus the nonliving environment with
which they interact
Species - a group of organisms that is able to interbreed and produce fertile offspring
Population - a group of organisms of the same species who live in the same area at the same time
Populations of different species that live together in the same ecosystem form a larger group
known as a community
Abiotic (nonliving) factors in the environment that affect the community
○ Ex: pond water pH, amount of sunlight, wind, temperature
Autotrophs are species that make their own food from basic inorganic materials, including all
photosynthesizing plants (light energy → sugars/vitamins)
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Heterotrophs are consumers - species that obtain their food from organic matter, including
herbivorous and carnivorous animals
○ Detritivores and saprotrophs feed on dead organic matter. Detritivores like earthworms
ingest dead organic material like dead animal bodies. Saprotrophs like fungi/bacteria
secrete digestive enzymes onto organic matter and then absorb their nutrients.
○ Saprotrophs are thus called decomposers for their decomposition of organic matter
4.2 Energy Flow
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Food chain - the sequence of organisms that provide food for one another
Producers produce food (photosynthesis), consumers eats its food
Autotrophic plants start food chains bc they capture sunlight and are eaten
Arrows in a food chain point to the direction in which energy + nutrients flow
Trophic level - the position of an organism in the food chain
○ Green plants (producers) at the lowest trophic level, then primary consumers
(herbivores), then secondary and tertiary consumers (carnivores)
Food web = a series of interconnected food chains
In each step of the food chain, energy is lost from cell respiration, digestion, death
Energy pyramid = transfer of energy between trophic levels
Nutrients are recycled, and decomposers are responsible for a lot of it
4.3 Carbon Recycling
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Carbon cycle - carbon is recycled as carbon dioxide gas, in aquatic environments
In anaerobic conditions, methane is produced from organic matter by methanogenic bacteria, and
diffuses into the atmosphere or accumulates in the ground
4.4 Climate Change
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Greenhouse effect: shortwave solar radiation passes through the atmosphere → longwave
(infrared) solar radiation is reflected back by the Earth → some longwave radiation is absorbed
and re-emitted by greenhouse molecules in the atmosphere. This warms the Earth’s surface
Increased CO2 from industrial production and methane from rice paddies + cattle farming
Unit 5: Evolution and Biodiversity
5.1 Evidence for Evolution
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Variation within a species is a result of both genetic and environmental factors. Selection
pressures act on individuals, and some may be better suited to their env than others
Evolution - the cumulative change in the heritable characteristics of a population
People have altered certain domesticated species by breeding selected individuals in artificial
selection
Homologous structures - anatomical features that are similar in shape, not necessarily in
function, in different organisms. Suggests common ancestry
○ Vertebrate pentadactyl limb in bats, whales, humans
Continuous variation - variation in a species controlled by genes, producing diff features
5.2 Natural Selection
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Charles Darwin + Alfred Wallace’s theory of evolution, natural selection
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○ Populations are generally stable despite large numbers of offspring
○ Better adapted individuals have a competitive advantage
○ There is heritable variation within species
○ Advantageous heritable traits become more frequent over generations
Darwin’s finches’ beak adaptations, industrial melanism in moths, antibiotic resistance in bacteria
5.3 Classification of Biodiversity
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Classification of living organisms in order to organize them into groups to show
similarities/differences
Taxonomy - the study of identifying, naming, and grouping organisms. From Carolus Linnaeus
Two names: genus name + species name
Domain (archaea, bacteria, eukarya) → kingdom (archaebacteria, eubacteria, plantae, animalia,
fungi, protista) → phylum → class → order → family → genus → species
Phyla of the plant kingdom:
○ Bryophyta: simplest land plants (mosses + liverworts), no vascular system to carry
water, reproduce by spores, no roots, rhizoids to absorb water on surface
○ Filicinophyta: have roots, stems, and leaves; reproduce by spores
○ Coniferophyta: shrubs and trees, produce pollen instead of spores, produce seeds (found
in cones), needle-like leaves to reduce water loss
○ Angiospermophyta: flowering plants which are pollinated by wind/animals, all have
flowers which produce pollen, all produce seeds
Phyla of the animal kingdom:
○ Porifera: sponges, no nerves or muscular tissue
○ Cnidaria: sea anemones, corals and jellyfish; marine; sting animals with nematocysts
and trap them in their tentacles
○ Platyhelminthes: body cavity w/ a mouth & anus, can be parasites, flatworms/tapeworm
○ Annelida: segmented worms, simple gut w/ a mouth and anus, burrowing aerates soil
○ Mollusca: slugs/snails/squid/octopus, many have outer shell for protection
○ Arthropoda: crustaceans, insects, spiders; all have a chitin exoskeleton; segmented
bodies w/ jointed limbs
○ Chordata: humans + vertebrates, a dorsal nerve cord, rod of cartilage supporting the
nerve cord, a post-anal tail, pharyngeal slits
Dichotomous key: a series of steps to identify unknown organisms
5.4 Cladistics
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All organisms have evolved from a common ancestor; look at universality of DNA
Cladograms show how species are related to each other
Analogous structures - structurally different features that perform a similar function, cannot be
used to establish a relationship between two species, unlike homologous structures
Unit 6: Human Physiology
6.1 Digestion and Absorption
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The digestive system contains a long tube called the alimentary canal, which works with glands
to move, break down, and absorb food
Digestion = hydrolysis, breaks down large, insoluble molecules to small, soluble ones
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Enzyme types: amylase (salivary, starch → maltose + pancreatic, maltose → glucose), protease
(pepsin, protein → polypeptides + endopeptidase, polypeptides → amino acids), and lipase
(pancreatic, triglycerides → fatty acids and glycerol )
○ Mouth: food is broken down by chewing + salivary amylase, which digests starch
○ Peristalsis moves food through the esophagus to the stomach, where gastric glands in
the stomach wall secrete pepsinogen, which is activated by HCl. Goblet cells secrete
mucus to cover the stomach lining. Food is now chyme
○ Small intestine: circular muscle layer contracts to make peristalsis, and
carbohydrates/polypeptides/lipids are absorbed here. The inner surface of the small
intestine has many villi (simple columnar epithelial cells), which have networks of
capillaries. Glucose and amino acids are cotransported with Na+ using a symporter,
hydrophilic monosaccharides use channel proteins, water travels through osmosis, and
lipids directly pass through to get to blood vessels. Fatty acids and glycerol are taken into
the lacteals and travel in the lymphatic system.
○ Large intestine: reabsorption of water and mineral ions like Na+ and Cl-, rest is egested
6.2 The Blood System
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Arteries carry blood away from heart ventricles, and have thick collagen outer walls and elastic
fibers to withstand high blood pressure. Narrow lumen
Capillaries are one cell thick, movement of RBCs
Veins carry blood back towards the atria, have thinner walls, have valves to prevent blood
backflow
Right side of heart receives deoxygenated blood and pumps it to the lungs via the pulmonary
artery
Left side receives oxygenated blood via the pulmonary vein and pumps it to body cells
Double circulation
Ventricles are more muscular to pump blood
Atria are separated from ventricles by atrioventricular valves, which prevent backflow
Semilunar valves in the aorta and pulmonary artery
Coronary arteries provide oxygen to the heart
Cardiac muscle is myogenic, which means it contracts w/o the nervous system
○ The sinoatrial node (SAN) in the right atrium sets heart rate. It produces an impulse that
stimulates both atria to contract.
○ Then, the atrioventricular node (AVN) in the right atrium is stimulated. It delays the
impulse briefly until the atrial contraction finishes and transmits it along the bundle of
His to the Purkinje fibers, causing ventricular contraction
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Stretch receptors in aorta and various arteries pick up on an increased heart rate or slowed
down heart rate and send impulses to medulla
○ Medulla interprets information and sends impulses via sympathetic (speeds up) and
parasympathetic (slows down) nerves
○ Epinephrine (adrenaline) hormone from adrenal glands released during stress and
increased activity level travels to pacemaker to cause it to increase heart rate
Blockage in the coronary arteries is coronary thrombosis, can cause a heart attack
Atherosclerosis is the buildup of plaque in arteries, which restricts blood flow, can cause
coronary heart disease (CHD)
Blood is made of RBCs to carry oxygen, buffy coat (WBC + platelets) to fight infections + clot
wounds, and plasma (nutrients, antibodies, CO2, hormones, oxygen, urea, heat)
6.3 Defense Against Infectious Disease
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Pathogen - a living organism/virus that invades the body and causes disease
First line of defense: skin, mucous membranes, second line: phagocytic cells, inflammatory
response, natural killer cells (both innate immunity - rapid responses to broad range of microbes)
Blood clotting: if a small blood vessel is damaged, platelets release clotting factors, which cause
platelets to stick to the area. These factors activate prothrombin → thrombin, an enzyme that
catalyzes the reaction of fibrinogen → fibrin, which covers the area
Phagocytes destroy pathogens in non-specific immunity
Antigens are proteins on the surface of bacteria, and antibodies are molecules produced by
lymphocytes in response to foreign antigens. Antibodies are specific to antigens
After an infection has passed, some of the lymphocytes remain as memory cells, acquired
immunity
○ A lymphocyte binds to its specific antigen, and activated lymphocytes divide by mitosis
to produce clones. Some are memory b cells, while others are plasma cells, which secrete
antibodies
B cell can be indirectly activated after binding to a helper T cell which was activated by a
macrophage (cell of the body) that ingested a whole cell such as a bacteria
○ Macrophage ingests pathogens and presents antigen, to which helper T-cell binds to. It
then divides into memory cells and active helper T-cells. B cell ingests pathogens, and
are activated by the active helper T-cell, and clone into memory + plasma cells.
Antibiotics have no effect on viruses because they’re not living and have no metabolic pathways
HIV infects helper T cells
6.4 Gas Exchange
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Occurs in the alveoli of the lungs where oxygen from the air diffuses into blood capillaries, and
CO2 passes in the opposite direction
Air → trachea → one of the bronchi → bronchioles → alveoli. Spirometers measure the amount
of air that’s exchanged when breathing
Lungs can’t move by themselves, so intercostal muscles contract to cause breathing
○ Contractions increase volume of chest cavity + lower lung pressure = inhalation
○ External and internal intercostal muscles = antagonistic
Alveoli are made of pneumocyte cells, and are wrapped in capillaries. Oxygen diffuses through
the alveolus and capillary into the blood, CO2 = opposite.
○ Walls of alveoli have 2 types of cells. Type 1 pneumocytes cover most of the surface and
are responsible for gas exchange. Type 2 pneumocytes are larger, rounder, and produce
surfactant, a liquid that reduces surface tension and prevents the alveolus’ sides from
sticking to each other.
6.5 Neurons and Synapses
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The nervous system uses neurons, or nerve cells, to transmit information in the form of impulses
The central nervous system is the neurons of the brain and spinal cord. The CNS receives info
from sensory receptors
Peripheral nerves are the network of neurons that carry information to and from the CNS.
Includes sensory neurons, which carry information to the CNS, and motor neurons, which
transmit impulses from the CNS to muscles and glands
Dendrites receive information from relay neurons, and a long axon carries the impulse. The axon
is covered by a myelin sheath formed from Schwann cells, which allows for saltatory
conduction at node of Ranvier
Electrical impulses occur as Na+ and K+ ions move in and out through the plasma membrane
Resting potential: -70 mV, the inside of the axon is negatively charged with respect to the outside
Depolarization down an axon = action potential
○ When a neuron is stimulated, gated Na+ channels open and sodium flows in.
○ As a result, the inside of the axon becomes positively charged. So, the sodium channels
close
○ Gated K+ channels open and potassium ions flow out to reestablish the resting potential,
aka repolarization
○ Both sodium and potassium channels close, and sodium-potassium pumps move ions
back across the membrane, 3Na+ out, 2K+ in (refractory period)
Threshold potential = -55 mV, needed for an action potential
Synapse = where two neurons meet, neurotransmitters are released into the synaptic cleft to
transmit impulses across neurons
○ When a nerve impulse reaches the end of the axon, a calcium channel opens, and Ca2+
enters.
○ Acetylcholine (ACh) is released through the exocytosis of synaptic vesicles
○ ACh binds to sodium channel receptors, causing depolarization. ACh is broken down into
acetate & choline by acetylcholinesterase
○ Choline reabsorbed
6.6 Hormones, Homeostasis, and Reproduction
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Homeostasis - controlling the internal environment of the body, controlled by the endocrine and
nervous systems
A system of ductless endocrine glands, which secrete hormones into the bloodstream
Blood glucose level
○ When high, beta cells from Islets of Langerhans in the pancreas secrete insulin to
stimulate the liver to convert glucose to stored glycogen and muscle cells to take in
glucose
○ When low, alpha cells produce glucagon to stimulate the liver’s hydrolysis of glycogen to
glucose
Type I Diabetes: beta cells don’t produce insulin, Type II: body cells fail to respond to produced
insulin
Metabolic rate
○ When low, the hypothalamus releases thyrotropin releasing hormone, which
stimulates the release of thyroid stimulating hormone by the anterior pituitary
○ TSH stimulates the thyroid to secrete thyroxine and triiodothyronine
Body temperature
○ Hypothalamus - control center
○ When hot, arterioles dilate to allow for heat to radiate off, sweat glands activate
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○ When low, arterioles narrow and muscle shiver
Appetite
○ Leptin is secreted from fat cells and acts on hypothalamus receptor cells to inhibit
appetite
Sleep
○ Melatonin is secreted by the pineal gland
○ The optic nerve detects a lack of light → suprachiasmatic nucleus in the hypothalamus
→ pineal gland makes melatonin
Testes produce testosterone
Ovaries produce estrogen and progesterone, pituitary gland produces luteinizing hormone
(LH) and follicle stimulating hormone (FSH)
○ FSH stimulates the development of follicles, which secretes estrogen and builds the
endometrium. LH stimulates ovulation and the formation of the corpus luteum (which
releases estrogen + progesterone)
○ Corpus luteum disintegrates, + endometrium sheds
Unit 7: Nucleic Acids
7.1 DNA structure and replication
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3’-5’ carbon linkages
Antiparallel DNA strands, one goes 5’-3’, other goes 3’-5’
Cytosine and thymine = pyrimidines, adenine and guanine = purines
○ A pyrimidine always pairs with a purine, since pyrimidines are smaller
A eukaryotic chromosome is composed of a double strand of DNA combined w/ proteins
○ Some, called histones, combine 9 into a nucleosome, which help supercoil chromosomes
DNA replication = semiconservative, and goes from the 5’ to 3’ end
○ The enzymes helicase unwinds the two DNA strands
○ Two strands, a leading strand and lagging strand. Since it goes 5’-3’, the leading strand
will continuously move down while the DNA is unwound. The lagging strand goes in
small sections away from the replication fork.
Leading strand:
○ First, RNA Primase adds a short length of RNA, attached by complementary base
pairing to the DNA template. This acts as a primer, allowing DNA Polymerase III to
bind, which adds free building units called deoxynucleoside triphosphates (dNTPs) to the
3’ end of the primer and then to the forming strand of DNA
○ The RNA primer is removed by DNA polymerase I
Lagging strand:
○ RNA primase synthesizes a short RNA primer, and DNA Polymerase III starts replication
by attaching at the 3’ end of the RNA primer and adding dNTPs from 5’-3’
○ DNA polymerase replaces RNA primer, short lengths of new DNA = okazaki fragments
○ DNA ligase seals up each break between okazaki fragments
Regulator genes are present in DNA to control the expression of one or more other genes
Introns are sequences of nucleotides within genes. The corresponding sequences in the mRNA
transcribed from these genes are removed in the nucleus before translation in the cytoplasm
Once introns have been removed by RNA splicing, the remaining RNA is mature RNA, which
contains exons, the sequences that will be translated.
Telomeres are at the ends of chromosomes and get shorter as u get older
7.2 Transcription and gene expression
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In transcription, RNA polymerase separates the DNA into two strands, and binds to the DNA
RNA polymerase builds the RNA molecule (uracil instead of thymine)
Promoter + terminator region
Gene expression is controlled by:
○ Transcriptional regulation (mechanisms that prevent transcription) - nucleosomes are
important because they can either inhibit or allow transcription by controlling whether the
necessary molecules can bind to DNA.
○ Post-transcriptional modification (mechanisms that control/regulate mRNA after it’s
produced) - introns are sections of DNA that are transcribed but not translated. Exons are
left and expressed.
○ Translational regulation (mechanisms that prevent translation)
7.3 Translation
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tRNA is made of a single strand of nucleotides, and has a triplet of bases, an anticodon, that pairs
with a codon on the mRNA strand
An activating enzyme attaches an amino acid to the specific tRNA molecule that has its
corresponding anticodon
Ribosomes are the site of protein synthesis, and are composed of two subunits, one large and one
small built from protein and ribosomal RNA (rRNA).
Two charged tRNA molecules can bind to a ribosome at one time
Translation takes place in the cytoplasm and has four stages:
○ Initiation: begins at a start codon (AUG) near the 5’ end of the mRNA. This codes for
methionine. mRNA binds to the small subunit of the ribosome, and an activated tRNA
molecule moves into position at site 1 in the ribosome. Its anticodon binds with the AUG
codon, and a large ribosomal subunit moves into place.
○ Elongation: tRNA molecules bring amino acids to the mRNA strand in the order
specified by the codons. A second tRNA brings another AA to site 2, The ribosome
catalyzes the formation of a peptide bond between the two AAs. The ribosome moves
along the mRNA and the first tRNA is released.
○ Translocation: the movement of the ribosome along the mRNA strand one codon at a
time. The unattached tRNA moves into the exit site and is released to the cytoplasm, to
pick up another AA.
○ Termination: translocation and elongation continue until one of the three “stop” codons
aligns with site 2, which is a signal to end translocation.
Protein production: sequence of AA linked by peptide bonds, primary structure
Secondary structure occurs when the polypeptide chain takes up a permanent folded/twisted
shape (alpha helix/pleated sheets)
Tertiary structure occurs as the molecule folds further due to interactions between the R groups
of the AAs. The protein takes up a 3D shape
Quaternary structure linked two or more polypeptide chains to form a single, large, complex
protein (collagen, hemoglobin, antibodies, myosin)
Proteins can be fibrous (long, narrow, insoluble, secondary structure) or globular (round, 3D,
soluble, tertiary or quaternary)
Polar (hydrophilic) and nonpolar (hydrophobic) amino acids
Unit 8: Metabolism, Cell Respiration, and Photosynthesis
8.1 Metabolism
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Metabolic pathways consist of chains or cycles of rxns that are catalyzed by enzymes
Enzymes lower the activation energy of a reaction
Induced-fit model: the shape of an enzyme is changed slightly as a substrate binds to its active
site. The substrate causes a slight change in the active site’s shape so it can fit
Enzyme inhibitor is a molecule that disrupts the normal reaction pathway between an enzyme
and a substrate
○ Competitive inhibitor: molecule other than substrate (but structurally similar) bonding
to enzyme’s active site. Increasing substrate concentration helps
○ Noncompetitive inhibitor: molecule that binds to an allosteric site (other than active
site) causes change to active site. Increasing substrate concentration does nothing
End-product inhibition: when an enzyme in a pathway is inhibited by the product of that pathway
to prevent overproduction
8.2 Cell Respiration
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Cell respiration is the controlled breakdown of food molecules such as glucose or fat to release
energy, often in the form of ATP. There are four stages:
○ Glycolysis: in the cytoplasm, and is anaerobic (oxygen-independent). A hexose glucose
molecule is phosphorylated, and two phosphate groups from ATP bind to the glucose,
which splits into two triose phosphates (lysis). The triose phosphates are oxidized, while
NAD+ are reduced to NADH + H+. The two phosphate groups on each molecule form
ATP, net plus of +2 ATP, 2 NADH + H +, and 2 molecules of pyruvate.
○ Link Reaction: aerobic and in mitochondrial matrix. Converts pyruvate into acetyl CoA
using coenzyme A. A carbon is removed from pyruvate to create CO 2 in a
decarboxylation reaction, and the pyruvate reduces NAD+ into NADH + H+.
○ Krebs Cycle: Acetyl CoA from the link reaction enters, and forms a six carbon
compound, citrate. The molecule is decarboxylated to form 2CO2 and reduces more
NAD+. 1 ATP is formed, and FAD + is reduced to FADH2. In total: 8NADH + H+, 2
FADH2, 2 ATP, 6 CO 2.
○ Electron Transfer Chain and Chemiosmosis: ATP production, takes place on the inner
mitochondrial membrane of the cristae. Electron carriers pick up electrons and move
down the chain, losing energy to the proton pumps. At the end of the chain, the electrons
are combined w/ protons and oxygen to make water, oxidative phosphorylation.
Electron carriers cause H+ to be pumped into the intermembrane space, until the
accumulation of a concentration gradient makes them diffuse back in, through ATP
synthase, making ADP + P i into ATP. Total ATP produced in cell respiration: 36.
8.3 Photosynthesis
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The process by which light energy is harvested and stored as chemical energy, occurring in
autotrophs
Two parts, which both take place in the chloroplasts:
○ Light-dependent reactions: in the stacks of thylakoid membranes, where light is
absorbed by photosynthetic pigments like chlorophyll (photoactivation). First,
photosystem II absorbs light energy and the excited electrons are accepted by a carrier
protein molecule. Water is also split (photolysis) by the light energy to replace lost
electrons. Excited electrons move along the electron transport chain into photosystem I,
losing energy. This lost energy is used to pump protons into the thylakoid interior, which
diffuse out, forming ATP from ATP Synthase in photophosphorylation. A photon is
absorbed again at photosystem I, and forms NADPH + H+ from NADP+.
○ When ATP is produced using energy from electrons, the process is called non-cyclic
photophosphorylation. Cyclic photophosphorylation is an alternative pathway that
involves the use of only PS I and does not produce NADPH. When light is absorbed by
Photosystem I, the excited electron may enter into an electron transport chain to produce
ATP. Following this, the de-energised electron returns to the photosystem, restoring its
electron supply (hence: cyclic). As the electron returns to the photosystem, NADP+ is not
reduced and water is not needed to replenish the electron supply.
○ Light-independent reactions: in the stroma, ATP and NADPH + H+ from the first stage
are used. Calvin cycle: ribulose bisphosphate (RuBP) combined with CO2 to form
glycerate 3-phosphate (GP) in a process called carbon fixation. This is catalyzed by
Rubisco. The NADPH + H+ and ATP convert the GP into triose phosphate (TP), which
leaves the cycle to produce glucose/amino acids.
Unit 9: Plant Biology
9.1 Transport in the Xylem of Plants
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Transpiration: the loss of water vapor from the leaves and stems of plants
○ Water is absorbed into the roots, travels up the stem in the xylem vessels in the vascular
bundles to the leaves, and is lost by evaporation through stomata
Cohesion-tension theory:
○ Loss of water vapor from the stomata results in negative pressure (tension) in the xylem
vessels
○ Water vapor enters the air spaces in the leaf from the xylem vessels to replace water lost
○ Continuous columns of water are drawn up the xylem due to cohesion + adhesion, lignin
support
○ Tension caused by transpiration causes water to be drawn into the roots from the soil
Guard cells control the opening of stomata: when they take up water and become turgid, stoma
open. When they have no water, flaccid shape closes stoma
○ When the plant has little water, abscisic acid (ABA) binds to the guard cells. This makes
Ca2+ enter, and, more importantly, K+ leave, so that water follows by osmosis. This makes
the guard cells flaccid and the stoma close
Factors affecting transpiration: light (causes stomata to open), temperature (more water
evaporation), humidity (concentration gradient outside stomata reduced), wind speed (blows
away outside water vapor)
Xerophytes: plants that live in arid climates, which have evolved to survive water shortages
○ Marram grass leaves have a waxy cuticle and roll up, and hairs trap moisture. CAM, or
crassulacean acid metabolism, plants open stomata at night time and close during the day
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Halophytes are plants in salty areas. They actively absorb salt into their roots so that the
concentration is higher in root tissue than the water, making water follow by osmosis
Roots’ adaptations for water uptake:
○ Root hairs along epidermis of root to increase water absorption surface area
○ Extensive branching network to increase number of roots for absorption
○ Symbiotic, mutualistic relationship with mycorrhizae fungi. This fungi attaches to roots,
absorbs water through its hyphae then delivers water and minerals to roots
Mineral root uptake:
○ Fertile soil typically contains negatively charged clay particles to which positively
charged mineral ions (cations) may attach
○ Minerals that need to be taken up from the soil include Mg2+, nitrates, Na+, K+
○ Mineral ions may passively diffuse into the roots, but will more commonly be actively
uploaded by indirect active transport using a cotransporter
○ Root cells contain proton pumps that actively expel H+ ions into the surrounding soil. The
H+ ions displace the positively charged mineral ions from the clay, allowing them to
diffuse into the root along a gradient. Negatively charged mineral ions (anions) may bind
to the H+ ions and be reabsorbed along with the protons.
Water follows the minerals through osmosis into the roots
○ From the root, water will either move towards the xylem via the cytoplasm (symplastic)
or the cell wall (apoplastic). In the symplastic pathway, water moves continuously
through the cytoplasm of cells (connected via plasmodesmata).In the apoplastic pathway,
water cannot cross the Casparian strip and is transferred to the cytoplasm of the
endodermis
9.2 Transport in the Phloem of Plants
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Translocation is the movement of organic molecules through the phloem tissue of plants, which
have two types of cells: perforated sieve tube cells and companion cells (to provide ATP).
The xylem carries water and minerals in one direction, the phloem (made of living tissue)
transports materials in either direction, from a source to a sink. Ex: sugars from photosynthesis
moved to growing root tissue
Translocation happens in 3 steps:
○ Phloem loading: sucrose is loaded into the phloem in one of two ways: apoplast loading
(requires H+ pump and use of ATP, active transport) or symplast loading (passive
movement through plasmodesmata). Water (from the xylem) enters the phloem by
osmosis once the sucrose concentration is high.
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Mass Flow: Once sucrose and water mix (sap), the material moves via mass flow, the
passive transport of material with water sap moves from high hydrostatic pressure to low
hydrostatic pressure towards sink.
Phloem Unloading: as the sugar is unloaded into sink cells, this creates a hypotonic
solution in phloem, which causes water to move back to xylem. This allows for the lower
hydrostatic pressure here for mass flow
9.3 Growth in Plants
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Meristems are the growing parts of a flowering plant where cells divide by mitosis
○ Apical meristem: tissues at the tip of the root and shoot that enable plant to grow in
length (primary growth)
○ Lateral meristem: cylinders of dividing cells located throughout stems and roots of
woody plants where primary growth has stopped and causes growth in girth (secondary
growth)
■ Vascular cambium – cells that add layers of vascular tissue called secondary
xylem (wood) and secondary phloem
■ Cork cambium – cells which replace epidermis with periderm
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Monocot plant - plant with one cotyledon in seed, dicot plant - plant with two cotyledons in seed
Micropropagation: a technique which uses meristems of plants to grow whole plants. Meristems
are used because they are undifferentiated (can turn into any cell type)
Phototropism influenced by auxin hormones. Auxin efflux pumps pump auxins in one direction,
typically down the stem.
9.4 Reproduction in Plants
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Pollination is the transfer of pollen (which has male gametes) from the anther to the stigma
Cross-pollination: when pollen travels from one plant’s anther to another’s stigma
Self-pollination: when pollen is deposited on the stigma of the same plant (less gen. variation)
Fertilization occurs in ovule
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Seeds are fertilized ovules that have developed over time
Seed dispersal mechanisms:
○ Seed pods can dry out then snap releasing the seeds (pea plants)
○ Edible fruits around seeds are eaten along with the seeds. Seeds are tough to digest so
they come out in waste
○ Nuts like the acorns are buried in the ground
Seed parts:
○ Cotyledon - “Seed leaves” which store food reserves needed for germination
○ Testa - hard, protective coating
○ Micropyle - pore through which water is absorbed to begin the process of germination
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Germination - the development of the seed into a new plant. The three factors are: temperature
(suitable for enzymes), water (rehydrates the seed and initiates gibberellin release), and oxygen
(essential for aerobic respiration)
○ Germination begins when a seed absorbs water in a process called imbibition. The
embryo plant releases a growth hormone called gibberellin, which stimulates the
synthesis of amylase, a digestive enzyme, by the cells in the outer aleurone layer. The
amylase digests starch molecules, converting them to food
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Phototropism - plant’s growth responses to relative periods of darkness/light.
○ Long-day plants flower when days are long/nights are short.
○ Short-day plants flower as nights become longer/days are shorter. Require a continuous
period of darkness before flowering. Can’t flower if darkness if interrupted by a pulse of
artificial light
○ Flowering is controlled by the leaf pigment called phytochrome, which can be inactive
Pr and active Pfr .
○ Pr absorbs red light and is converted to Pfr.
○ In long-day plants this increase in Pfr promotes flowering. Pfr reverts back to Pr in
darkness with far red light
○ In short-day plants Pfr inhibits flowering but during long nights sufficient Pfr is removed
to allow them to flower.
Unit 10: Genetics and Evolution
10.1 Meiosis
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Genetic variety occurs from:
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During prophase I, chromosomes shorten and coil. Homologous pairs of chromosomes
(which have the same genes but different alleles because they're from diff parents) come
together to form a bivalent. When they line up, crossing over may happen at chiasmata
○ During metaphase I, the bivalents line up on the equator and attach to spindles. There’s
random assortment of the bivalents here
Mendel’s Law of Independent Assortment: when gametes are formed, the separation of one
pair of alleles into the new cells is independent of the separation of any other pair of alleles. (if
Aa is crossed with Bb, A has an equal chance of being paired with B or b)
10.2 Inheritance
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Any two genes on the same chromosome are said to be linked. Linked genes are usually passed
on together, and the genes on any chromosome form a linkage group.
○ Linked genes don’t follow Mendel’s Law of independent assortment--they aren’t
inherited independently
Recombinant - offspring in which the genetic information has been rearranged by crossing over
so phenotypes that are different from the parents are produced
Variation
○ Discrete (or discontinuous) variation: clearly distinguishable categories that can’t be
measured. Ex: blood groups, left vs right handedness. These are controlled by alleles and
not affected by environmental factors
○ Continuous variation: possible to make a range of measurements. Ex: height, hand span,
skin color. Controlled by genes but also affected by environmental factors
Most characteristics are controlled by a group of genes, or polygenes. Like skin color
10.3 Gene Pools and Speciation
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Evolution is the cumulative change in the heritable characteristics of a population
The “heritable characteristics” are all the alleles in the gene pool
○ Stabilizing selection: if a population is well adapted to its environment, the same alleles
will be selected, maintaining a stable population
○ Directional selection: if there is a change in environment and some alleles are more
favorable, they will survive and reproduce, shifting the population.
○ Disruptive selection: natural selection results in the formation of two new forms
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Speciation is the formation of new species from an existing population. Speciation can only
occur if there is a barrier dividing the population
○ Allopatric speciation: occurs in different geographic locations, a physical barrier
separates a species into two geographically isolated populations, which then develop
independently under different conditions (and eventually unable to interbreed).
○ Sympatric speciation: occurs in the same geographic location.
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Temporal and behavioral isolation: when the time of reproduction or behavior
of members of one population of a species is incompatible with that of the other
Polyploidy: a polyploid organism has more than two sets of chromosomes,
which happens when chromosomes are not completely separated during cell
division. A diploid and tetraploid species can’t mate, so it’s a barrier
Unit 11: Animal Physiology
11.1 Antibody Production and Vaccination
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Immunity - resistance to an infection, acquired from infancy onwards as the body is exposed to
pathogens
Certain leukocytes (WBCs) can recognize antigens, proteins on the surface of a pathogen
1st line of defense: non-specific phagocytic leukocytes
2nd line of defense: specific response to antigens, involving antibodies (producing them requires
macrophages, B-lymphocytes, and helper T-lymphocytes)
Clonal selection
○ When a pathogen enters the bloodstream, a macrophage ingests it and antigen
presentation
○ Helper T-cells bind to the macrophage + antigen and are activated. The activated T-cells
then divide into clones, some of active helper T-cells and some of memory cells
○ B-cells take in an process antigen proteins form the pathogen, and present them
○ Active helper T-cells bind to the B-cells, activating them. B-cells divide into plasma cells
(which secrete antibodies) and memory cells
○ Antibodies destroy pathogen
Active immunity: when an individual is exposed to an antigen and produces antibodies.
Passive immunity: when antibodies are transferred from one person to another. Ex: passing
antibodies from mother to child through the placenta
When microorganisms enter the body, an inflammatory response may occur
○ Mast cells and basophil cells release histamine at the site of invasion
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Histamine - chemical which relaxes arteriole walls for increased blood flow and loosens
the cells in the capillary walls so they allow more plasma to flow through to infected area
This increased blood flow brings heat, oxygen, and nutrients and incidentally swelling
(oedema) to the infected/injured area.
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Allergic Reaction
○ Allergies are excessive immune response against antigens
○ These antigens stimulate plasma cells to create a specific antibody called a reagin (IgE
antibody)
○ Reagins bind to mast cells and after subsequent exposure to the same antigen, will
produce histamine and cause allergic responses like increased mucus production,
swelling, itchiness
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Monoclonal antibodies are artificially produced to target one specific antigen. Mice are injected
with an antigen, which stimulates the production of plasma cells. These are combined with tumor
cells to create a hybridoma cell, which creates many antibodies
○ Used in pregnancy tests. HCG from a pregnant woman’s urine binds to mobile
monoclonal antibodies, which travel down the stick. These bind to immobilized
anti-HCG antibodies, which are colored. Then, unbound antibodies bind to a control
antibody.
Humoral immune response – activation and clonal selection of B cells, resulting in production
of secreted antibodies
Cell Mediated Immune Response – activation and clonal selection of cytotoxic T cells, which
directly destroy certain target cells (like cancer cells)
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Vaccination: introduction of a weakened pathogen or a piece of that pathogen to a person to build
up memory B cells against future exposure of the antigen
○ Secondary response afterwards results in faster antibody production
11.2 Movement
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Joint: where two or more bones meet; bones: provide support for the body, protecting organs;
ligaments: attach bones to one another at a joint; tendons: attach muscles to bones, forms of
tissue from collagen fibers; muscles: provide force needed for movement, and occur in
antagonistic pairs (movement of one causes other to move in opposite direction), motor neurons:
stimulate muscle contraction
Synovial fluid: lubricates joints during movement, cartilage: slippery covering that reduces
friction
Insect and arthropod muscles aren’t attached to bones but an exoskeleton
Muscles consists of bundles of muscle fibers (cells)
Each fiber contains myofibrils, which contain myofilaments (called thick and thin filaments)
○ Thin filaments consist of two strands of actin and two regulatory proteins called
tropomyosin and troponin complex
○ Thick filaments are staggered arrays of myosin molecules
Myofilaments are staggered causing light and dark pattern (striated muscle)
Myofibrils are divided into repeating units called sarcomeres - the basic contractile unit of the
muscle
Each sarcomere contains repeating units of thin and thick filaments
Sarcomeres are divided up by areas
○ I bands (light band): area of thin filaments only in non-contracting muscle
○ A bands (dark band): area of thick and thin filament overlap
○ Z lines: structure to which thin filaments are attached.
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Tropomyosin - protein that blocks the binding of myosin head
Troponin complex - protein that binds to Ca2+, which causes tropomyosin to change shape and
thus expose myosin head binding site
Sliding filament theory:
○ Nerve impulses travel along the muscle fiber, down T-tubules. They then spread along
the membrane of the sarcoplasmic reticulum, causing Ca2+ ions to be released
○ Binding sites for myosin heads on actin filaments are covered by troponin and
tropomyosin. The Ca2+ makes tropomyosin change shape and allows binding
○ ATP changes myosin head into an erect position, so it can bind to the actin filament. A
phosphate is released, the myosin head bends towards the center of the sarcomere, pulling
the actin. New ATP binds, starting over cycle.
11.3 The Kidney and Osmoregulation
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Excretion: removal of waste products (nitrogenous waste) and excessive concentrations of
metabolites (products of metabolism - chemical reactions of the body)
Proteins and nucleic acids get broken down in a process called deamination into ammonia, which
is toxic to cells if it accumulates.
○ Ammonia will be synthesized into urea by the liver, which gets transported to kidneys by
circulatory system, which will then be excreted as urine.
○ Since ammonia is very soluble in water, aquatic organisms can flush it easily out of
system (since a lot of water is absorbed by these organisms), therefore they synthesize
ammonia
○ Terrestrial animals have less access to water so need to flush from system in less toxic
form (urea or uric acid)
Osmoregulation: control of the water potential in the body (water and solute concentrations)
○ Osmoconformers maintain internal conditions that are equal to their external environment
(without using energy), thus minimize water movement in and out of cells (so their
internal conditions are isotonic with the outside environment)
○ Osmoregulators keep internal osmolarity constant with changing environment (does use
energy)
The kidneys act as filters, removing waste molecules from the blood. Functional unit of the
kidney = nephron
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Ultrafiltration at the glomerulus: the incoming afferent arteriole is wider than the
outgoing efferent arterioles, so the hydrostatic pressure is high. This makes blood plasma
filter through three layers: fenestrations in the capillary endothelium, basement
membrane, and podoote of the Bowman’s capsule. Water, salts, glucose, amino acids,
and small proteins can pass through
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Reabsorption at the proximal tubule: useful materials are reabsorbed.
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Osmoregulation at the Loop of Henle: at the descending loop of Henle, water passes
via osmosis out of tubules into interstitial fluid then capillaries since this fluid is
hypertonic to the filtrate. This fluid is more hypertonic because Interstitial Na+ and Cldiffuses into medulla at the ascending loop of Henle. This makes the medulla maintain
the higher solute concentration so water can diffuse out at the descending tubule.
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Reabsorption at the distal tubule: Na+ and Cl- are reabsorbed; water follows by osmosis
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Collecting duct: NaCl actively transported out again into medulla which allows water to
follow. Release of ADH (antidiuretic hormone) from posterior pituitary gland
(produced in hypothalamus) causes this membrane to become more permeable to water
because it causes more aquaporin proteins to be created to allow for more transport of
water into capillaries. ADH is released when water level in blood is low.
11.4 Sexual Reproduction
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Spermatogenesis: the production of mature sperm cells (spermatozoa) in the seminiferous
tubules of the testis
○ Germinal epithelial cells (spermatogonia) divide by mitosis to produce primary
spermatocytes
○ These divide by meiosis into secondary spermatocytes and then spermatids
○ Developing sperm attach to Sertoli cells, which differentiate spermatids into spermatozoa
○ These mobile sperm then travel to the epididymis
FSH stimulate meiosis in spermatocytes, testosterone stimulates the maturation of secondary
spermatocytes into mature sperm cells, and LH stimulates the secretion of testosterone by the
testis
Sperm mature in the epididymis. Seminal vesicles (70% of semen, fructose-rich) and the prostate
(alkaline fluid protects sperm against acidic vagina) gland produce semen to move sperm through
the vas deferens and out the urethra
Oogenesis: production of ova, the female gamete. Begins in the ovaries when a female is a fetus.
○ Oogonia, the germinal epithelium, divides by mitosis to produce primary oocytes.
○ Primary oocytes undergo meiosis but stop during prophase I, continuing during puberty
from FSH. This forms a secondary oocyte and polar body, but stops at prophase II.
○ Finishes meiosis II when a sperm fertilizes, creates a fertilized egg and polar body
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Fertilization: nucleus of sperm unites with nucleus of egg, occurs in fallopian tube
○ When a sperm approaches the zona pellucida, an acrosomal reaction releases digestive
enzymes to reach the plasma membrane, which the sperm fuses with
○ Then, a cortical reaction by cortical granules fuses with the plasma membrane to prevent
polyspermy (multiple sperm entering the egg’s nucleus)
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A zygote divides into a blastocyst, an attaches in the endometrium, developing into an embryo
Once the blastocyst is in the endometrium, it secretes human chorionic gonadotropin (HCG),
which maintains the corpus luteum, to produce estrogen and progesterone (to support the
endometrium lining)
○ After the first trimester, the placenta takes over for hormonal production
The embryo grows into a fetus, which is connected to the placenta by the umbilical cord. The
placenta is responsible for gas and waste exchange between the mother + fetus
Labor: endometrium secretes prostaglandins, which initiate uterine contractions. The
hypothalamus then releases oxytocin, secreted by the posterior pituitary
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