AP Biology Unit 4: Cell Communication and Cell Cycle

Paracrine signaling

Paracrine signaling

signaling to a cell nearby

Autocrine signaling

cell signaling to itself

Endocrine signaling

-longest distance cell signaling

Endo = within

signaling between cells in different parts of the organism

juxtacrine signaling

cell signaling to a cell that is close/next to or touching

Cell cycle/Mitosis

cell division of somatic cells - makes an exact copy of original cell (diploid/2n —> diploid/2n)

grow, develop, repair

IPMATC

Interphase: G1, S, G2

Prophase, Metaphase, Anaphase, Telophase, Cytokineses

Interphase

G1: cell growth - cell does most of its growth , gets bigger in size, proteins/RNAs made

S: synthesis of DNA —> DNA replication (2n—> 2n)

G2: preparation for mitosis - growth/preparation for cell division

Prophase

chromosomes condense

spindle fibers forming

nuclear envelope dissolves

Metaphase

chromosomes align at the metaphase plate

Anaphase

sister chromatids are pulled apart to opposite ends of the cell

Telophase

chromosomes decondense

new nuclear membrane forms around each set of chromosomes

cell begins to divide

Cytokinesis

2 identical somatic diploid cells

G0 (mitosis)

resting, cells may get signal to leave this phase if organism needs to grow/repair

G1 checkpoint

check for nutrients, growth factors, DNA damage

G2 checkpoint

check for cell size, DNA replication

Metaphase checkpoint

checks for spindle attachment so that when sister chromatids separate, each new cell gets a copy of a chromosome

Negative feedback loop

goal is to bring system back to set point(restore homeostasis)

stimulus is decreased

-ex. increase in blood glucose level

positive feedback loop

amplifies the effects of an event when something needs to happen quickly

stimulus is increased

-ex. childbirth, ethylene release for fruit ripening

CDK(cycling dependent kinase)

a kinase, can activate target proteins by phosphorylating(adding phosphate group) to them

CDK levels stay constant through interphase and mitosis

Cyclin

help to regulate the cell cycle

help to control progression through cell cycle checkpoints

cycling levels fluctuate(peak right before mitosis)

Maturation Promoting factor (MPF)

stimulates mitosis

“mitosis” promoting factor

cancer

unregulated cell growth/division

mutated tumor suppressor

no brake - no cell growth regulation - no stopping —> cancer cells

mutated proto-oncogene —> oncogene

too much gas - cell growth continues to be stimulated even when it isn’t supposed to be —> tumors/cancer

proto-oncogene

genes involved in normal cell growth

stimulate cell growth

tumor suppressor gene

encode proteins that regulate cell division and keep it in check

normal p53

DNA damage/abnormalities —> cell cycle arrest, DNA repair, cell cycle restart or initiate apoptosis

mutated p53

cell cycle continues despite damages, cells can become cancerous

signal amplification

ligand binds to a receptor —> receptor interacts with enzyme, which will activate 2nd messenger(cAMP) —> cAMP activates(phosphorylates) many proteins, which in turn activate many other proteins = large cell response

quorum sensing

used by bacteria to determine population density

plasmodesmata

plant cells can communicate by sending signals to other cells via plasmodesmata(channels) that directly connect the cells

signal transduction pathway

1) reception: target cells detect signaling molecule(ligand binds to receptor)

2) transduction: signal converted to different forms

3) response: response to signal is produced