AP Biology The Cell Cycle Part 1

One cell becoming two

Binary Fission in Prokaryotes Cell wall Origin of replication Plasma membrane E. coli cell Bacterial chromosome Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell. Two copies of origin Origin Origin Replication continues. One copy of the origin is now at each end of the cell. Replication finishes. The plasma membrane grows inward, and new cell wall is deposited. Two daughter cells result.

Chromatin vs. Chromosomes appearance within the cell.

Coiling up of Chromatin using histones

Somatic cells vs. Germ cells The egg surrounded by sperm.

Sister Chromatids

Mitosis (1 Division) vs. Meiosis (2 Divisions)

AP Biology The Cell Cycle Part 2

Centrioles

Interphase

Before and after the S phase

Interphase cell (Look at the chromatin in the blue nucleus and the yellow cytoskeleton.)

Start of Mitosis

Cell in Prophase

Mitosis “Division of the nucleus”

Cell in Metaphase

Cell in Anaphase

Cell in Telophase and starting Cytokinesis

One cell becoming two

Motor Protein and the Spindle Fibers Chromosome movement Kinetochore Tubulin subunits Motor protein Microtubule Chromosome

Animal vs. Plant

LE 12-10 Chromatin condensing Nucleus Chromosomes Cell plate 10 µm Nucleolus Prophase. The chromatin is condensing. The nucleolus is beginning to disappear. Although not yet visible in the micrograph, the mitotic spindle is starting to form. Prometaphase. We now see discrete chromosomes; each consists of two identical sister chromatids. Later in prometaphase, the nuclear envelope will fragment. Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at the metaphase plate. Anaphase. The chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of the cell as their kinetochore micro- tubules shorten. Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.

Microscopic view of Mitosis in Onion root tips Microscopic view of Mitosis in Onion root tips. Can you identify the stages?

Checkpoints (Is all going according to plan?)

Chapter 12: The Cell Cycle AP Biology Chapter 12: The Cell Cycle

Checkpoints (Is all going according to plan?)

Relative concentration . M G1 S G2 M G1 S G2 M MPF activity Cyclin Relative concentration Time Fluctuation of MPF activity and cyclin concentration during the cell cycle

Molecular mechanisms that help regulate the cell cycle . G1 Cyclin S Cdk Degraded cyclin M G2 accumulation G2 checkpoint Cdk Cyclin is degraded Cyclin MPF Molecular mechanisms that help regulate the cell cycle

Chromosome movement Kinetochore Tubulin subunits Motor Microtubule . Chromosome movement Kinetochore Tubulin subunits Motor protein Microtubule Chromosome

Cells anchor to dish surface and divide (anchorage dependence). When cells have formed a complete single layer, they stop dividing (density-dependent inhibition). If some cells are scraped away, the remaining cells divide to fill the gap and then stop (density-dependent inhibition). 25 µm Normal mammalian cells

Cancer cells do not exhibit anchorage dependence . Cancer cells do not exhibit anchorage dependence or density-dependent inhibition. 25 µm Cancer cells

Malignant cancer cells from the breast (See the ABNORMAL “crab” shape of the cells.)

Mutations and Cancer MUTATION Cell cycle-stimulating pathway NUCLEUS Growth factor MUTATION Hyperactive Ras protein (product of oncogene) issues signals on its own G protein Cell cycle-stimulating pathway Receptor Protein kinases (phosphorylation cascade) NUCLEUS Transcription factor (activator) DNA Gene expression Protein that stimulates the cell cycle Cell cycle-inhibiting pathway Protein kinases MUTATION Defective or missing transcription factor, such as p53, cannot activate Active form of p53 UV light DNA damage in genome DNA Protein that inhibits the cell cycle

Cell Communication (Signaling) Part 1 AP Biology Cell Communication (Signaling) Part 1

Direct Contact

Local and Long Distance within an organism.

Phermones

Earl Sutherland

Step 1: Reception

Step 2: Transduction

Step 3: Response

See the CONFORMATION SHAPE CHANGE by the receptor protein caused by the ligand binding. Signal molecule (ligand) Gate closed Ions Plasma membrane Ligand-gated ion channel receptor Gate open Cellular response Gate closed

Cell Communication (Signaling) Part 2 AP Biology Cell Communication (Signaling) Part 2

Phosphorylation and Hydrolysis

Receptor Protein

G protein Receptor

Tyrosine – Kinase Receptor

Ion Channel Receptors Signal molecule (ligand) Gate closed Ions Plasma membrane Ligand-gated ion channel receptor Gate open Cellular response Gate closed

Intracellular receptors

Secondary Messenger cAMP Adenylyl cyclase Phosphodiesterase Pyrophosphate H2O P P i ATP Cyclic AMP AMP

First messenger (signal molecule such as epinephrine) Adenylyl cyclase G protein G-protein-linked receptor GTP ATP Second messenger cAMP Protein kinase A Cellular responses

Secondary Messenger Calmodulin EXTRACELLULAR FLUID Signal molecule (first messenger) G protein DAG GTP G-protein-linked receptor PIP2 Phospholipase C IP3 (second messenger) IP3-gated calcium channel Cellular re- sponses Various proteins activated Endoplasmic reticulum (ER) Ca2+ Ca2+ (second messenger) CYTOSOL

Cell Communication (Signaling) Part 3 AP Biology Cell Communication (Signaling) Part 3

Kinases “turn on” processes Phosphotases “turn off” processes

Small signal produces a BIG response

The Big picture Growth factor Reception Receptor Phosphorylation cascade Transduction CYTOPLASM Inactive transcription factor Active transcription factor Response P DNA Gene NUCLEUS mRNA

Scaffolding Proteins Signal Plasma molecule membrane Receptor Three different protein kinases Scaffolding protein

Tyrosine – Kinase Receptor (Evolution – Change over TIME)