Discoveries
1. Robert Hooke:
a. Compound microscope and examined thin slices of cork
b. Credited with first discovering and naming cells.
c. Observed the cell walls of dead plant cells
2. Anton van Leeuwenhoek
a. Microscope maker
b. Observed living cells under a microscope
c. Observed algae, protozoa, bacteria, red blood cells, and other cells
3. Matthias Schleiden/Theodor Schwann:
a. Schleiden
i.
Helped form the cell theory
ii.
Studied plant cells-- identified plant cell nuclei and said all plants are made of cells
b. Swann
i.
Studied animal nerve and muscle tissue
ii.
Work extended Schleiden’s to eventually become the cell theory (all living things are
made of cells.
4. Rudolf Virchow
a. Father of modern cellular pathology
b. Every cell comes from a preexisting cell
Modern Cell Theory
1. Cell Theory
a. All living things are made of one or more cells
b. The cell is the basic unit of structure and function in a living organism
c. All cells come from preexisting cells
2. Common characteristics of ALL living things
a. Made of one or more cells.
b. Reproduce
c. Grow and develop
d. Universal genetic code
e. Obtain material and use the energy from it
f. Maintain a stable environment
g. Respond to change
h. Change over time
Prokaryotic and Eukaryotic
1.
Prokaryotic
Cells
Eukaryotic
Cells
Average Cell Size
1-10
micrometers
10-100
micrometers
Cell wall
Yes
Some
Cell membrane
yes
yes
Nuclear membrane/ nucleus
no
yes
cytoplasm
Yes
Yes
DNA
Yes, in the
cytoplasm
Yes, nucleus
Ribosomes
Yes
Yes
Membrane enclosed
organelles (mitochondria,
chloroplasts, endoplasmic
reticulum, Golgi apparatus,
a cytoskeleton of
microtubules and
microfilaments)
No
Yes
Mode of locomotion
(movement)
Flagella
Flagella and
cilia
Found
Bacteria
Fungi, protist,
plants,
animals
*To help remember that eukaryotes make up most organisms (humans) this of eu=you as in humans
Cell Organelles
1. Cell membrane
a. Composed of a phospholipid bilayer (double layer of phosphate heads and lipid tails) proteins,
and cholesterol.
b. Semi-permeable/selective permeable-- allow certain substances to pass through
2. Cell wall
a. Found in plant and fungus cells
b. Made of cellulose/chitin
c. Provides extra shape and support for the cell
d. Protects plants from expanding under pressure
3. Nucleus
a. Eukaryotic cells
b. Control house of cells
c. DNA (info to form chromosomes)
i.
Direct cell activity by giving instructions on which protein to make and when
ii.
Makes up chromatin-- carries hereditary (genetic) info
1. Coils up into chromosomes when the cell is ready to divide
a. Chromosomes are only visible when a cell is preparing for division
4. Nuclear membrane (envelope)
a. Double-layered, selectively permeable
b. Surrounds fluid portion of the nucleus
c. Allows ribosomes and ions to leave the nucleus
5. Nucleolus
a. Found in nuclei
b. Produces ribosomes
6. Endoplasmic Reticulum (ER)
a. Produce and transport materials such as proteins
b. 2 Types
i.
Rough ER-- responsible for protein production; ribosomes attached
1. Ribosomes: build proteins through protein synthesis
a. Found in the cytoplasm and attached to ER
ii.
Smooth ER: Makes and stores lipids (no ribosomes attached)
7. Golgi Apparatus (Complex/Bodies)
a. “Manufacturing, packaging, and shipping center for cells”
i.
Specialized enzymes that help change, package, sort, and distribute proteins and lipids
outside of the cell.
ii.
Found in abundance in cells that secrete such as glands
8. Vesicles. Vacuoles, Lysosomes
a. Vesicles: store and transport cellular products
i.
Vacuoles: stores water, salts, and wastes; provides support
ii.
Lysosomes: found in animal cells; store digestive enzymes used to break down lipids,
carbohydrates, proteins and remove waste; enzymes can remove old organelles and
engulf viruses or bacteria
9. Mitochondria (powerhouse of the cell)
a. Uses chemical energy from food (glucose) to produce ATP for cellular work through cellular
respiration.
i.
Cellular respiration produces CO₂ as a byproduct
1. Cellular respiration: Process used in cells to break down glucose and produce
ATP
a. Aerobic respiration: glycolysis, Kreb cycle, and electron transport chain
i.
Glycolysis (cytoplasm): First step; one molecule of glucose is
converted into two three-carbon molecules called pyruvate. A net
gain of two ATP molecules are produced during this step
1. Glycolysis Summary
C6H12O6(glucose) →
Chemical reactions requiring
ATP, ADP, and Phosphate →
Net 2 ATP + Pyruvate
ii.
iii.
2. Aerobic vs. Anaerobic Respiration Pathways
3. Is Oxygen Present?
a. Yes (Aerobic Respiration):
i.
Must have oxygen to occur
ii. Takes place in mitochondria
iii. Produces approximately 34 ATP molecules
from one glucose molecule (not including
glycolysis)
b. No (Anaerobic Respiration)
i.
No oxygen needed
ii. Takes place in cytoplasm
iii. Produces 2 ATP molecules from one
glucose molecule
Kreb Cycle (citric acid cycle): the part of aerobic respiration that
takes place in the mitochondria and produces two molecules of
ATP for every one molecule of glucose
1. Takes place in the mitochondrial matrix
2. Produces a net gain of 2 more ATP
3. Citric acid is made in the beginning
Electron Transport Chain: The part of the aerobic respiration
that occurs in the mitochondria after the Krebs Cycle and produces
a net of 32 more ATP molecules for every one molecule of
glucose.
1. Most efficient at producing ATP; water is also produced
b. Anaerobic respiration: glycolysis and fermentation
i.
Anaerobic respiration: process that does not require oxygen and
produces a net of 2 molecules of ATP for every one molecule of
glucose
1. Produce less energy; 2 ATP produced when fermentation
occurs
ii.
Alcoholic Fermentation: anaerobic cellular respiration that occurs
in plants and other microorganisms such as yeast.
Factors that Affect the Rate of Fermentation
● The concentration of fermenting agent (yeast or
bacteria)
● Type of sugar being fermented
● The concentration of nutrients/sugar
● Temperature
● pH
1.
b. Eukaryotic cells
c. Possess their own DNA and ribosomes
10. Chloroplast
a. Plant cells and algae
b. Possess own DNA
c. Contains chlorophyll (a green pigment that chloroplasts use to convert light energy to chemical
energy (glucose)
d. Carries out photosynthesis which produces oxygen as a byproduct
i.
Uses light energy, carbon dioxide, and water to produce oxygen and glucose-monosaccharide(simple sugar)
ii.
Used by autotrophs
iii. Process of photosynthesis
iv.
v.
Light-dependent Reactions: light must be present for the reaction to occur
Light Independent Reaction (Calvin Cycle):
Light Dependent Reaction
●
●
●
●
●
Require light
Electrons in the chlorophyll photosystems absorb the light energy
Energy from electrons convert ADP to ATP
Water molecules are split to form oxygen, hydrogen ions, and electrons
Hydrogen ions attach to carrier molecules to be used in later steps of
photosynthesis. (NADP+ becomes NADPH)
Light Independent Reaction
● This stage does not require light
● Carbon dioxide and hydrogen ions combine to form simple sugars
● Simple sugars can be stored as complex carbohydrates, such as cellulose and
starch
CO₂ + H+ → C6H12O6 (glucose)
1. Plants use the glucose made in photosynthesis for energy. The glucose is also
converted into more complex carbohydrates (starch and cellulose) needed for
development and growth.
2. Heterotroph eats the plant, the organism breaks it down through cellular
respiration.
11. Centrioles
a. Made of microtubules (hollow tubes of protein
b. Important in mitosis in forming the spindle apparatus and the cleave furrow.
i.
Comes in pairs and form centrosomes.
12. Cytoplasm (cytosol)
a. Cell’s metabolic processes
Types of Eukaryotic Cells
1. 6 Kingdoms
a. Protist: Algae, protozoa, slime molds
i.
Contractile vacuole: pumps excess water out of a cell
ii.
Locomotion: flagella(Euglena), cilia (paramecium), pseudopod (amoeba)
b. Fungi: Mold, mushroom, yeast
c. Plant: mosses, ferns, grasses, veggie plants, trees
d. Animals: sponges, jellyfish, worms, snails, insects, fish, frogs
2. Similarities and Differences
Fungi
Plant
Animal
Cell membrane,
nucleus, mitochondria,
ribosomes
Yes
Yes
Yes
ER and Golgi App.
Most
Yes
Yes
Type of Cell
Uni/Multicellular
Multicellular
Multicellular
Cell Wall
Yes (chitin)
Yes (cellulose)
No
Lysosomes
No
No
Yes
Vacuoles
Some
Yes (large)
None
Chloroplast
No
Yes
No
Cellular respiration(
oxygen is used to help
break down glucose to
release energy and CO₂
Yes
Yes
Yes
3. Plant Cell vs. Animal Cell
Cell Differentiation and Organization
1. Cellular differentiation: process that creates different types of specialized cells
2. Stem cells: cells that can change into different types
3. Hierarchy of organization
a. Cell → tissues → organs → organ systems → organisms
Homeostasis and Cellular Transport
1. Homeostasis: the need for living organisms to maintain a stable internal environment in order to
survive.
a. Must be maintained at the cellular level
b. Cellular transport: movement of material in and out of the cell
Importance of the Cell Membrane
c. Semi-permeable: allows some substances in but keep others out
d. Made of a phospholipid bilayer ( 2 layers arranged tail to tail)
i.
Phosphate head is polar and hydrophobic-- attract water
ii.
Fatty acid tail is nonpolar and repels water
e. Fluid mosaic model
i.
Developed by Singer and Nicolson
ii.
Phospholipid and fatty acid tails provide fluidity by only allowing certain substances to
cross the membrane
iii. Protein and cholesterol molecules embedded to contribute to the mosaic nature of the
membrane and provide structure and stability
iv.
Proteins create protein channels, pores, or gates that allow hydrophilic substances and
ions to cross the membrane.
v.
Carbohydrate chains play a crucial role in cell to cell recognition and the manner of
bacteria, viruses, or other pathogens gain entry into the host cell.
2. Cellular Transport
a. Materials move in and out of the cell by way of passive or active transport; helps maintain
homeostasis
i.
Passive transport: The cell does not use any of its own energy.
1. Osmosis: similar to diffusion EXCEPT
a. Only involves the movement of water molecules
b. Moves water molecules across a semipermeable membrane through which
the solute (dissolved particle) cannot cross.
c. This occurs when the concentration of a solute is greater on one side of a
membrane than on the other side of the membrane, BUT the solute cannot
diffuse through the membrane.
d. Hypertonic Solution: The solution outside of the cell membrane contains
more solute and less water than the solution inside the cell membrane.
i.
Water rushes out of the cell through the membrane causing the cell
to shrink
ii. Ex: A CELL WITH A 10% SOLUTE SOLUTION IS PLACED IN
A WATER SOLUTION THAT IS 30% SOLUTE. THE WATER
FROM THE INSIDE OF THE CELL WITH MOVE FROM
LOWER SOLUTE CONCENTRATION TO HIGHER SOLUTE
CONCENTRATION.
e. Hypotonic: solution outside the cell membrane has a lower solute
concentration than the solution inside the cell. Water will move at a
greater rate into the cell, causing it to swell.
i.
Ex: A cell with 30% solute is placed in a solution that contains
10% solute. The water will move across the membrane to dilute
the side with the higher solute concentration.
ii. HINT: Will a cell shrink or swell if placed in a hypotonic solution?
It will swell. A simple word association may help you to
remember this answer. Associate “hypo” with an o with hippo.
Hippos are large animals. Remember that cells in a hypotonic
solution will swell like a hippo
f. Isotonic: solute concentration inside and outside are equal. No change in
size.
g. Effects of Osmosis on Animal Cell/Plant Cell
i.
Plant cell
1. Hypertonic: plant cell loses water.
a. Contents of the cell will shrink
b. Highly Hypertonic solution- ex: if a plant is put into
saltwater, the contents of the cell will completely
shrink away from the rigid cell wall by way of
plasmolysis
2. Isotonic: a plant cell may not have enough water in it to
fully fill the cell wall cavity. The plant appears wilt or
flaccid (limp)
3. Hypotonic: The plant takes in water, but the rigid walls
keep them from bursting.
a. Cell allows pressure to build up within the cell.
b. Pressure = osmotic pressure, osmosis stops.
c. Turgor pressure gives plants turgor, rigidity so that
they can “stand up” and not wilt
d. Plants prefer hypotonic solutions
2. Diffusion: movement of molecules from an area of higher concentration (perfume
inside of a bottle) to an area of lower concentration (perfume outside of the bottle)
a. Difference in concentration in two areas is a concentration gradient
i.
Molecules always move WITH the gradient from higher to lower
concentration.
b. Some materials can move across the cell membrane into or out of the cell
using simple diffusion
i.
Dynamic(continuous) equilibrium: when net concentrations of
molecules on both sides of the cell membrane are equal.
1. Molecules will continue to move, the rate of movement is
equal in both directions in and out.
2. No net gain. Carbon dioxide and oxygen moves through SD
3. Facilitated Diffusion: movement of particles through a transport protein from an
area of high concentration to an area of lower concentration (in the same direction
as the concentration gradient)
a. Transport proteins aids in the movement of particles (such as ions and
water) not able to penetrate the phospholipid bilayer without using energy
b. Protein channel act as a pore embedded into the membrane allowing
specific particles to move with the concentration gradient across the
membrane
i.
Water through aquaporins; ions through ion channels
c. Carrier proteins have a specific shape that binds to a specific type of
molecule and moves it across the cell membrane.
i.
Molecules include ions, glucose, and other macromolecules
ii.
Active transport: the cell has to use some of its own energy to move the materials from
an area of lower concentration to an area of higher concentration
1. Moves against concentration gradient
2. Ex. animal cells need for potassium and sodium
3. ATP (adenosine triphosphate)
a. Metabolism: set of chemical reactions needed to maintain life
b. Adenosine Triphosphate (ATP): Main source of energy for cells. Living
organisms use to store and release energy.
i.
Made when organisms break down food such as glucose and starch
(carbohydrates).
ii. The potential energy stored in the food can then be converted to
chemical energy stored in and released from molecules of ATP
iii. 3 main parts: Adenine, ribose sugar, and three phosphate groups.
iv.
v.
●
●
●
●
●
Special molecule because energy can be stored when the third
phosphate group is added.
Although ATP is great for storing energy, most cells don’t have
very much because it does not store a lot of energy over a longer
period of time. Cells have more ADP
ATP Uses
Energy for Active Transport
Moving organelles inside the cell
Transmit nerve impulses
Muscle contractions
Used by plants during photosynthesis to make glucose
vi.
4. Transport Proteins called protein pumps
a. Energy-requiring protein motors that can change the shape of the protein
to allow specific solutes to stick to receptors.
5. Endocytosis, exocytosis, and receptor-mediated endocytosis
a. Endocytosis: the cell takes in a larger particle by surrounding it with cell
material and taking the particle into the cell.
i.
Pinocytosis (cell drinking): cell takes in dissolved molecules
ii. Phagocytosis: cell takes in a large particle, such as food or bacteria
b. Exocytosis: cells way of getting rid of large particles such as undigested
food, waste products, or releasing a hormone that a cell makes.
i.
Particle is released in a vesicle. Once the vesicle meets the
membrane of the cell, the vesicle membrane breaks open and fuses
with the cell membrane. In the process
Cellular Reproduction
The Cell Cycle and Mitosis
1. Somatic cells: the cells that makeup tissues and organs.
a. Diploid—> contains the full number of chromosomes; have a 2n number of chromosomes
i.
EX: humans somatic cells have 23 pairs of chromosomes for a total of 46 chromosomes
b. Ex: blood cells, liver cells, nerve cells, skin cells etc.
c. New somatic cells are made when one parent cell divides into two identical daughter cells.
i.
EX: to repair a skin cut, the skin cells around the cut divide until the cut is repaired.
2. The Cell Cycle
a. The process that somatic cells go through in order to grow and to reproduce.
b. Divided into two main parts: one part for cell growth and one part for cell division.
i.
Interphase: growth stage where cells increase their size and copy their genetic material
and centrioles.
1. Cell grows, transport of materials into and out of the cell becomes less efficient
2. Longest part of the cell cycle —> 90% of cell cycle
3. Centrioles: cell organelles found in animal cells that are shaped like a cylinder
and plays a role in spindle formation and cytokinesis. Made of microtubules and
moves chromosomes during mitosis.
4. Divided into 3 parts:
a. G1 and G2 —> Gap phases where cell size increases
b. S phase —> chromosomes are replicated
i.
G1 Phase (first gap): As the cell grow, many proteins necessary
for continued growth and DNA replication are synthesized (made)
ii. G0 Phase: Resting phase in the cell cycle. Cells are in a dormant
(inactive) state.
iii. S Phase (synthesis(make)): the DNA replicates in the nucleus to
form a new set of identical chromosomes.
1. When the cell divides, each new cell will have the correct
number of chromosomes.
iv. G2 Phase (second gap): Last part of interphase.
1. The cell continues to grow, synthesize all other organelles,
and make a variety of proteins needed for mitosis and
spindle formation, including centrioles.
5. The division stage (M phase) includes both mitosis and cytokinesis
a. Mitosis (PMAT): The part of the cell cycle when the nucleus divides.
i.
The purpose of mitosis is to equally divide the contents of the
nucleus and to ensure a normal number of chromosomes in new
cells.
1. Prophase
a. Chromatin (genetic material) coils up, shortens
and thickens.
b. Each X like structure is made up of sister
chromatids (the result of DNA replication during
the S phase) that are held together by a centromere.
c. Nucleolus and nuclear envelope disappears
d. 2 pairs of centrioles move to opposite sides of the
cells. Microtubules, hollow rod-like structures,
form a spindle fiber, which will help move the
chromosomes to the new cells.
2. Metaphase:
a. 2nd stage
b. Chromatids attach to the spindle fibers by the
centromere.
c. Chromatids line up along the center of the cell.
d. Alignment allows each new cell to receive an
identical set of chromosomes.
3. Anaphase:
a. Chromosomes are pulled apart by the spindle fibers.
(Chromosome are separated chromatids)
4. Telophase:
a. Chromosomes are on the opposite end of the cells
and unwind.
b. Spindles disappear and a new nuclear envelope
forms around each set of chromosomes to form two
new nuclei.
b. Cytokinesis: Last stage of the cell cycle, evenly divides the cytoplasm and
creates two new genetically identical daughter cells.
i.
Plant cells:
1. cell plate forms midway between two new nuclei and
grows out to the edges of the cell.
2. Cell plate divides the cell in half.
3. A cell membrane then forms around each new cell, and a
cell wall forms on each side of the cell plate.
ii. Animal Cell:
1. Cell membrane begins to pinch in at the end of telophase
and gradually separate the cytoplasm.
2. Pinching is called cleavage furrow.
3. When the two new identical cells are separated, the cell
cycle is complete and will begin again with interphase.
Cell Cycle Regulation and Cancer
1. Regulating the Cell
a. Proper function of the cell cycle depends on instructions in the DNA.
i.
Genes give cells instructions for making proteins.
b. External Signals
i.
Growth factors can signal a cell to divide (Go signals) that initiate the cell to divide.
1. Can be produced by cells or be released from damaged cells.
2. Cells come into contact with other cells by binding to receptors on the surface of
the cell to multiply
c. Internal Checkpoints
i.
Ensure that cells divide properly.
ii.
Checkpoint: a control point in the cell cycle where a “stop” signal can prevent cellular
defects.
iii. Found in eukaryotic cells and have 3 main stages during the cell cycle
1. If there is a problem at any of the checkpoints, the cell cycle will be interrupted
until cellular conditions are more favorable or DNA repairs are made.
2. Checkpoints are managed by cyclins (specialized proteins) and kinase
(specialized enzymes) that function near the end of G1, G2/M transition, and
during metaphase.
d. Apoptosis: Programmed cell death (occurs when a cell becomes damaged or worn)
i.
Ex: If a cell encounters a problem at the internal checkpoint, proteins may signal
apoptosis.
ii.
Occurs when inside and outside factors signal for genes to produce self-destructive
enzymes
iii. Plays an important role in the development of tissues and organs
1. EX: developing a human embryo has webbed fingers and toes. Apoptosis is
responsible for the disintegration of the webbing of the fingers and toes.
e. Mutation: a permanent change in the DNA sequence of a gene
i.
Cancer
2. Cell Cycle Checkpoints
a. G1 Checkpoint
i.
Determines if the cell has reached an appropriate size and has adequate energy reserved
and nutrients to proceed through the cell cycle.
1. If neither is sufficient, the cell will not go to the S phase.
2. DNA is checked for damages to ensure that the cell is receiving signals for growth
factors to indicate the cell should divide.
b. G2 Checkpoint
i.
2nd gatekeeper that can prevent a cell’s entry into mitosis if certain conditions are not
met.
ii.
Place to make sure all chromosomes are duplicated correctly
1. Any DNA mutation found the cell cycle will stop in an attempt to repair the
mutated or damaged DNA.
2. If the DNA is correctly duplicated, the cyclin-dependent kinases starts mitosis
iii. M Checkpoint (spindle assembly checkpoint):
1. Last cell cycle checkpoint and happens near the end of metaphase.
2. Ensures that all sister chromatids are attached to the spindle microtubules
3. Will stop if the chromatids are not connected to the spindle fibers.
Cellular
Reproduction
1. Reproduction
a. The
production of
offspring from one
or two-parent organisms.
i.
Offspring: children; organisms produced or born to one or two-parent organisms
2. Asexual reproduction
a. Type of reproduction that occurs when only one parent organism
reproduces itself to form a genetically identical offspring
b. Takes place through mitosis
c. Larger number of organisms can be produced quickly
3. Asexual Reproduction in single-celled organisms
a. Binary fission: form of asexual reproduction that forms in singlecelled organisms.
i.
Bacteria and paramecium —> all prokaryotic cells
ii.
The organism grows, replicates its DNA, and splits in half.
4. Asexual reproduction in a multicellular organism (mitosis)
a. Budding: when a group of cells grows on a parent organism and
eventually detaches to become a separate organism.
i.
Fungi, hydra, sea anemones, yeast
b. Vegetative propagation: new plant from a parent plant
c. Regeneration: regrowing of a missing body part
i.
Starfish
d. Fragmentation: growing a new organism from a broken piece. Species will identical to parent.
5. Meiosis: the process that forms the sex cells called gametes (ova and sperm cells)
a. Gametes (sex cells)
b. Occurs only in the reproductive cells to form egg and sperm cells.
c. Produce haploid cells —> sex cells that contains half the number of chromosomes for that
organism; have an n number of chromosomes
i.
Human egg and sperm cells —> 23 chromosomes. When one egg is fertilized by one
sperm with 23 chromosomes, the offspring will have 46 chromosomes (23 pairs)
d. Homologous chromosomes: the two chromosomes that make up each pair of human somatic
cells.
i.
1 cell from the mother’s egg and 1 cell from the father’s sperm.
6. Summary of cell cycle of gametes.
a. Meiosis I
i.
Prophase I
1. Chromatins shortens and thickens into chromosomes. Each chromosome is made
of a pair of chromatids connected by a centromere. The chromosomes pair with
their homologous chromosomes to form a tetrad ( 2 chromosomes that are made
of two chromatids each equal 4 chromatids)
2. Because the homologous chromosomes are so close, crossing over (exchanging
of DNA in the homologous chromosomes) causing more genetic variation as
it causes new combinations of genes.
ii.
Metaphase I:
1. Nuclear membrane has disappeared and the spindle has formed. The
chromosomes are still in homologous pairs as they line up on the equator.
iii. Anaphase I:
1. Homologous chromosomes are pulled apart so that each group of chromosomes at
the pole can have a different “mix” of homologs
iv.
Telophase I:
1. Cluster of chromosomes at each pole and a nuclear membrane starts to form
around each cluster. Sister chromatids are not identical anymore because of
crossing over.
v.
Cytokinesis I:
1. Cytoplasm divides
b. Meiosis II
i.
4 new cells are formed with haploid number of chromosomes.
ii.
Males —> 4 genetically unique sperm cells are produced.
iii. Females —> the unequal division of cytoplasm resulting in only one viable egg and 3
polar bodies. Polar bodies cannot undergo fertilization and disintegrate.
Comparing Mitosis and Meiosis
Mitosis
Meiosis I
Meiosis II
Prophase
Chromosomes become Homologous
The DNA has not
visible. They are diploid, chromosomes pair
replicated, so the cells are
2n
together closely.
haploid, n
Crossing over may occur.
The cells are diploid at
this stage, 2n
Metaphase
The diploid number of
individual chromosomes
line up at the equator
The tetrads (4
chromatids) become
visible and line up along
the equator
A haploid number of
individual chromosomes
line up at the equator
Anaphase
Chromosomes split and
sister chromatids are
pulled to opposite sides
Homologous
chromosomes separate,
and one of each pair is
pulled to each pole
Chromosomes split and
sister chromatids are
pulled to opposite poles.
Two new nuclei are
formed, and the cell
divides to form two
genetically identical
diploid cells.
Two new nuclei are
formed, and the cell
divides to form two
haploid cells that are not
genetically identical
Two new nuclei are
formed from each of the
two daughter cells, and
the cells divide and form
four haploid cells.
Telophase/Cytokinesis
Studying Human Chromosomes
7. Karyotype: a type of chromosomal analysis that photographs and arranges chromosomes so that they
can be visually inspected for defects.
8. Chromosomes can be classified into two types:
a. Autosomes: contain genes for traits other than gender
b. Sex chromosomes: determines genders, male or female.
i.
Humans have 23 pairs of chromosomes (46 total) in their somatic cells. 22 are autosomal
and one pair contains the sex chromosome.
9. Sexual Reproduction, Fertilization, and Development
a. Formation of Sperm and Egg
i.
Gametes (sex cells) are the product of meiosis.
ii.
Production of the egg cell (ova) —> oogenesis
1. After the first phase of meiosis, the immature diploid egg cell divides, but almost
all of the cytoplasm and cell organelles go to one cell. As a result one cell is
larger than the other.
2. The larger egg receives everything and become the viable egg.
iii. Production of sperm cell (spermatozoa) —> spermatogenesis
1. The immature diploid sperm cell divides equally after the first phase of meiosis to
produce two cells that are equal is size.
2.
Each of the two cells divides again after the second phase of
meiosis so that four spermatozoa, all equal is size are produced.
3.
Fertilization
a.
Sexual reproduction: occurs whenever a haploid sperm fuses to a
haploid egg to form a diploid cell. This union is known as fertilization.
b.
In plants, sexual reproduction occurs when the sperm in a grain of
pollen fertilizes an egg cell and results in a seed. The transfer of pollen
from the male reproductive organ to the female reproductive organ in
plants called pollination.
4.
Conjugation- a type of sexual reproduction in which two parent
organisms, usually bacteria, exchange genetic material; no offspring
produced but new combination of genes are formed that can be passed to
future offspring
5. Development
10. Sexual Reproduction vs. Asexual Reproduction
Advantages
Asexual Reproduction (mitosis)
Sexual Reproduction (meiosis
● Produces large number of
offsprings which increase
survival in a favorable and
stable environment
Offsprings are genetically different
from either parent, which may help
the organism adapt and survive a
changing environment
Disadvantages
Offsprings are identical to the
parent organism, which may limit
their ability to survive a changing
environment
It produces a smaller number of
offspring more slowly, so fewer
offspring may survive. It usually
requires two parents, one male and
female