Transcript
CELL CYCLE
INTERPHASE
G1 - Cells undergo majority of growth
S - Each chromosome replicates (Synthesizes) to produce sister chromatids
G2 - Chromosomes condense - Assemble machinery for division such as centrioles
G2 OF INTERPHASECentrosomes(with centriole pairs) Chromatin
(duplicated)
Nucleolus Nuclearenvelope
Plasmamembrane
MITOSIS
is the process of forming (generally) identical daughter cells by replicating and dividing the original chromosomes, in effect making a cellular xerox. Commonly the two processes of cell division are confused. Mitosis deals only with the segregation of the chromosomes.
FUNCTIONS OF CELL DIVISION
20 µm100 µm 200 µm
(a) Reproduction. An amoeba, a single-celled eukaryote, is dividing into two cells. Each new cell will be an individual organism (LM).
B. Growth and development. This micrograph shows a sand dollar embryo shortly after the fertilized egg divided, forming
C. C. Tissue renewal. These dividing bone marrow cells (arrow) will give rise to new blood cells (LM two cells (LM).
PROPHASE
•The chromosomes condense and become visible•The centrioles form and move toward opposite ends of the cell ("the poles")•The nuclear membrane dissolves•The mitotic spindle forms (from the centrioles in animal cells)•Spindle fibers from each centriole attach to each sister chromatid at the kinetochore.
PROPHASE
Early mitoticspindle
Aster
Centromere
Chromosome, consistingof two sister chromatids
METAPHASE
The Centrioles complete their migration to the poles
The chromosomes line up in the middle of the cell ("the equator")
METAPHASE
Spindle
Metaphaseplate
Centrosome at one spindle pole
ANAPHASE
Spindles attached to kinetochores begin to shorten.
This exerts a force on the sister chromatids that pulls them apart.
Spindle fibers continue to shorten, pulling chromatids to opposite poles.
This ensures that each daughter cell gets identical sets of chromosomes
ANAPHASE
Daughter chromosomes
TELOPHASE AND CYTOKINESIS
• Two daughter nuclei begin to form in the cell.
• Nuclear envelopes forms.
• The chromosomes become less condensed.
• Mitosis, the division of one nucleus into two genetically identical nuclei, is now complete.
CYTOKINESIS
the process of splitting the daughter cells apart. Whereas mitosis is the division of the nucleus, cytokinesis is the splitting of the cytoplasm and allocation of the golgi, plastids and cytoplasm into each new cell.
TELOPHASE AND CYTOKINESIS
Nucleolusforming
Cleavagefurrow
Nuclear envelopeforming
MITOSIS IN A PLANT CELL
1 Prophase. The chromatinis condensing. The nucleolus is beginning to disappear.Although not yet visible in the micrograph, the mitotic spindle is staring to from.
Prometaphase.We now see discretechromosomes; each consists of two identical sister chromatids. Laterin prometaphase, the nuclear envelop will fragment.
Metaphase. The spindle is complete,and the chromosomes,attached to microtubulesat their kinetochores, are all at the metaphase plate.
Anaphase. Thechromatids of each chromosome have separated, and the daughter chromosomesare moving to the ends of cell as their kinetochoremicrotubles shorten.
Telophase. Daughternuclei are forming. Meanwhile, cytokinesishas started: The cellplate, which will divided the cytoplasm in two, is growing toward the perimeter of the parent cell.
2 3 4 5
NucleusNucleolus
ChromosomeChromatinecondensing
CYTOKINESIS IN ANIMAL AND PLANT CELLS
Daughter cells
Cleavage furrow
Contractile ring of microfilaments
Daughter cells
100 µm1 µmVesicles
forming cell plate
Wall of patent cell Cell plate
New cell wall
(b) Cell plate formation in a plant cell (SEM)
PROKARYOTIC CELL DIVISION
MEMBRANE STRUCTURE AND FUNCTION
TRANSPORT MECHANISMS
The movement of materialsacross membranes takesmany routes but the mechanism’s are categorized as either passive or active transport mechanisms
PASSIVE TRANSPORT
moves molecules along a concentration gradient
no cellular energy required
Concentration Gradient: When a solute in a cell is in high concentration on one side of a membrane compared to the other.
PASSIVE TRANSPORT MECHANISM
Outside of cell
Inside of cell (cytoplasm)
Lipid Bilayer
Proteins
Transport Protein Phospholipids
Carbohydratechains
Structure of the Cell Membrane
Go to Section:
Animations of
membrane structure
SIMPLE DIFFUSION
• the movement of a substance from higher concentration to lesser concentration
• occurs across the lipid bilayer
OSMOSIS
the diffusion of water (solvent) across a membraneinfluenced by total solute concentration Water always moves toward the side with a greater
concentration of solute
Tonicity: the ability of a solution to move water Hypertonic: Greater ability to move H2O; gains water
Hypotonic: Lesser ability to move H2O; loses water
Isotonic: equal ability to move H2O; no net water movement
ACTIVE TRANSPORT
moves molecules against a concentration gradient
requires cellular energy
top related