BIG IDEA #2
B i o logic al
s y s te ms ut i l iz e
e n e rg y a n d
m o l ec ular
bui l di ng bl o c ks to
g row, to
re pro duc e , a n d to
m a i nt ain
h o m eost asis.
FREE ENERGY
 Growth, reproduction and maintenance of the organization of
living systems require free energy and matter.
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Energy moves through all biological organisms and systems
Cells use energy in the form of organic molecules
Energy is stored in and released from chemical bonds
Cells utilize cellular energy in the form of ATP (easy to form and easy
to break to access the stored energy.
CATABOLIC VS. ANABOLIC
 Catabolic reactions break down molecules and release energy
 Anabolic reactions build larger molecules and require energy
input
IMPORTANCE OF WATER
 Properties of Water
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Polarity
Hydrogen Bonding
Adhesion
Cohesion
High specific heat
Universal solvent
 Solute
 Solvent
 Solution
 High heat of vaporization
CELL SIZE LIMITATION
 Cells require a high surface area to volume ration. This limits
their size
 Examples of cellular structures designed to maximize
exchange of materials by increasing surface area to volume
ratio:
 Root hairs
 Alveoli
 Villi and microvilli
METABOLIC STRATEGIES
 Ectothermic vs. Endothermic
 Ectothermic = cold blooded. Cell environment fluctuates with
the environment
 Endothermic = warm blooded. Maintain consistent cell
environment that is dif ferent than environment. High
metabolic rate.
 Osmoconformers = aquatic animals that maintain internal
conditions to fluctuate with the environment
 Osmoregulators= aquatic animals that maintain internal
conditions that are dif ferent from the outside environment.
Metabolic activity is necessary to maintain these conditions.
CAPTURING AND STORING FREE ENERGY
 Autotrophs = capture free energy from environment
“make their own food”
Phototroph (Photosynthetic) = use sunlight as energy source
Chemotroph (Chemosynthetic) = use inorganic molecules as
energy source
 Heterotroph = captures free energy by consuming other
organisms.
“make their own food”
Phototroph (Photosynthetic) = use sunlight as energy source
Chemotroph (Chemosynthetic) = use inorganic molecules as
energy source
ANAEROBIC RESPIRATION
 Without oxygen: Yields 2 ATP
 Two stages: Glycolysis and fermentation (alcoholic or lactic
acid)
 Glycolysis: Happens in cytosol. Glucose converted to two molecules
of pyruvate. Yields 2 ATP and 2 NADH
 Alcoholic Fermentation: two pyruvates are converted to ehtanol:
NADH is converted back to NAD+ to keep glycolysis going.
 Lactic Acid Fermentation: two pyruvates are converted to lactic acid.
NADH is converted back to NAD+ to keep glycolysis going.
AEROBIC (CELLULAR) RESPIRATION
 Occurs in Cells
 Four stages
 Glycolysis: Occurs in cytosol. Glucose is converted to two molecules
of pyruvate, 2 ATP, and 2 NADH
 Pyruvate oxidation: two pyruvates enter the mitochondrial matrix.
They are converted to 2 Acetyl CoA which go on to the Krebs Cycles;
and 2 NADH which go on to oxidative phosphorylation.
 Krebs Cycle: Occurs in mitochondrial matrix. Two turns of the cycle
convert the 2 Acetyl CoA molecules into: 6NADH, 2FADH2, and 2 ATP
 Oxidative Phosphorylation (electron transport and chemiosmosis):
happens in the cristae. The NADH and FADH2 molecules donate
electrons to the electron transport chain. As they move through the
chain their energy is used to pump H+ ions into the innermembrane
space. The H+ ions then move down their concentration gradient
through ATP synthase to make 34 ATP molecules (chemiosmosis)
SUMMARY OF ATP GENERATED FROM
CELLULAR RESPIRATION
PHOTOSYNTHESIS
 Energy from sun is converted into chemical energy of sugar
 Occurs in autotrophs (mostly in chloroplasts)
 Stages:
 Light Reactions: Occurs in the thylakoid membranes
 Light energy is absorbed by chlorophyll molecules in Photosystems I and II
which are embedded in the thylakoid membranes.
 Electrons become excited and move down an electron transport chain
from photosystem I to photosystem II. Their energy is used to pump H+
ions into the stroma.
 Electrons lost from Photsystem II are replaced from the electrons lost by
the splitting of water molecules. Electrons lost from Photosystem I are
replaced by electrons lost from Photosystem II.
 H+ ions build up in the stroma and move down their concentration
gradient through ATP synthase to generate ATP ( chemiosomsis)which will
go on to the Calvin Cycle.
 NADPH is also generated through the use of the enzyme NADP reductase.
It will also go onto the Calvin Cycle.
CALVIN CYCLE
 Most common pathway for Carbon fixation (taking CO2 and
converting it into organic molecules)
 Does not require light
 Happens in the stroma of the chloroplasts
 The enzyme Rubisco and the energy from ATP and NADPH is
used to bind CO2 to organic molecules. It is a multi -step
process in which G3P is produced. This molecule can be
converted into various types of molecule including glucose.
CELL MEMBRANES
 Cell membranes play a critically important role in maintaining
dynamic homeostasis.
 Selectively permeable
 Constant movement of molecules in and out
 Membrane itself is a fluid mosiac
 Membrane Structure
 Phospholipid bilayer: Hydrophilic, polar heads (phosphate group);
hydrophobic, nonpolar tails (fatty acids).
 Peripheral proteins: Lie on inside or outside
 G-proteins that relay signals (inside)
 Receptor or signal proteins (outside)
 Integral embedded proteins: bridge both layers
 Amphipathic
 Types: channel, receptor, recognition, membrane pumps
 Cholesterol molecules: maintain fluidity and prevent freezing
 Oligosaccharides: short carbohydrate chains attached to proteins: act
as signals
IDENTIFY THE PARTS OF THE CELL
MEMBRANE
MEMBRANES ALLOW FOR CELLULAR
DIFFUSION AND OSMOSIS TO OCCUR
 The membrane’s structure facilitates easy dif fusion of small,
nonpolar, or uncharged molecules into and out of the cell.
(Simple dif fusion)
 Polar molecules or charge molecules (ions) will only pass
through protein channels. (Facilitated dif fusion)
 In both processes, molecules move from high to low
concentration.
 Osmosis is the movement of water from high to low
concentration or high to low water potential. Most water
moves through proteins known as aquaporins.
 Hypotonic solutions= water moves in
 Isotonic solutions= water is in equilibrium
 Hypertonic solutions= water moves out
IDENTIFY THE T YPE OF TONICIT Y
ACTIVE TRANSPORT, ENDOCY TOSIS AND
EXOCY TOSIS
 Active Transport moves molecules through membranes from
low to high concentration and requires the input of ATP
 Example: Sodium/Potassium Pump
 Endocytosis: type of Active Transport involving the uptake of
very large molecules or particles
 Types: Phagocytosis, Pinocytosis, Receptor-mediated endocytosis
 Exocytosis: type of Active Transport involving the release of
very large molecules or particles
SODIUM POTASSIUM PUMP
CELL WALLS HAVE A STRUCTURAL AND
FUNCTIONAL PURPOSE
 Cell walls are found in plant cells, bacterial cells and fungal
cells
 Plants = cellulose
 Bacteria = Peptidoglycan
 Fungi = Chitin
EUKARYOTIC CELLS HAVE INTERNAL
MEMBRANES AROUND ORGANELLES
 Endomembrane
system:
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Nucleus
Rough ER
Smooth ER
Golgy
Lysosome
Vesicles
Vacuole
SEVERAL ORGANELLES ARE NOT PART OF THE
ENDOMEMBRANE SYSTEM
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Mitochondria
Chloroplasts
Ribosomes
Flagella
Cilia
Centriole
FEEDBACK MECHANISMS HELP TO MAINTAIN
DYNAMIC HOMEOSTASIS
 Positive Feedback= cellular processes increase the rate of
chemical reaction or cellular processes. This often leads to a
greater degree of instability.
 Examples: Labor Contractions(Oxytocin production)
Fruit ripening (Ethylene production)
 Negative Feedback = when a condition or chemical inhibits
some cellular process and often maintains stability
 Examples: Insulin regulation
RESPONDING TO ENVIRONMENTAL
CHANGES
 Plants:
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Photoperiodism= effect of the length of day and night on plant growth.
Phototropism= direction of plant growth is towards the light
Annual reproduction = complete life cycle in one growing season
Biennial= entire life cycle in two years
Perennial= grow and bloom every year
 Animals
 Kinesis= random movement in response to a stimulus
 Taxis= directional movement towards or away from a stimulus
 Chemotaxis
 Phototaxis
 Gravitaxis
 Circadian Rhythms= daily behavioral responses (internal clock)
 Chemotaxis
 Phototaxis
 Gravitaxis
HOW THE ENVIRONMENT AFFECTS DYNAMIC
HOMEOSTASIS IN LIVING SYSTEMS
 All living systems are af fected by biotic and abiotic factors.
 Biotic = living
 Abiotic = nonliving
 Energy flows through trophic levels (feeding patterns in a
community that are involved in energy transfer)
 Food Chains= simple feeding relationships
 Food Webs= complex feeding relation ships
ENERGY PYRAMIDS
 Only 10% of
available energy
passes from one
trophic level to the
next.
ECOLOGICAL SUCCESSION
 Ecological succession refers to the gradual changes that occur
to the structure and energy demands of an ecosystem
 Types:
 Primary succession= when life begins to form in an area that is
devoid of life or soil. (Ex: following volcanic eruption or in an abandon
parking lot)
 Secondary succession= occurs when change happens to an existing
community or a new community grows where there is intact soil with
seeds in the seed bank. Often follows fire, flood, tornadoes,
earthquakes, etc.
COMMUNIT Y INTERACTIONS
 Interspecific competition= two species compete for limited
resource
 Competitive Exclusion principle= theory that one population
will always be a better competitor and will outcompete the
other to the point of extinction in that area.
 Resource partitioning= can allow dif ferent populations of
animals to share a limited resource by utilizing that resource
in a dif ferent way.
 Symbiotic Relationships
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Commensalism
Mutualism
Parasitism
Predation
MECHANISMS TO EXCHANGE NUTRIENTS
AND WASTES WITH ENVIRONMENT
 Plants: exchange gas through stomata
 Animals:
 Aquatic: exchange gas through gills using a countercurrent exchange
system. Gills are a good example of increased surface area
 Terrestrial: exchange gas through skin or lungs (another good
example of increased surface area)
 Excretion in aquatic animals : secrete ammonia
 Excretion in terrestrial animals: urine (hyperosmotic urine
prevents dehydration.
 Birds and reptile secrete uric acid to allow for more water
retention.
VARIATIONS IN CIRCULATORY SYSTEMS
 Fish: two chambered heart and a single loop pathway for
circulating blood.
 Amphibians: three chambered heart and a double loop
circulation pathway.
 Mammals: four chambered heart and a double loop
circulation pathway. Most ef ficient
IMMUNE RESPONSE CONTAINS NONSPECIFIC
AND SPECIFIC MECHANISMS TO MAINTAIN
HOMEOSTASIS
 Nonspecific
immunity: physical
barriers, cilia, mucus,
pH of skin and body
fluids, leukocytes,
inflammation, natural
killer cells, fever.
 Specific immunity:
humoral (B cells,
plasma cells,
antibody production);
cell mediated (T cells:
cytotoxic and helper)
REGULATION AND TIMING OF CELLULAR
EVENTS CONTROL DEVELOPMENT
 Cell dif ferentiation is regulated by gene expression and cell
signaling
 Transcription regulated by transcription factors
 Homeotic genes control the pattern of body formation of an
embryo
 Embryonic induction is controlled by tissue development
 Apoptosis (cell suicide) is controlled by extracellular or
intracellular signals
 Seed germination is controlled by hormones ( gibberillin,
abscisic acid and ethylene
REGULATION AND TIMING ALSO CONTROL
POPULATION INTERACTIONS
 Hibernation (winter) and estivation (summer) are periods of
reduced metabolic activity
 Pheromones are chemical signals that trigger specific social
responses.
 Visual displays important for reproduction in many species
 Quorum sensing important for bacteria