AP Bio Unit 4: Cell Communication & Cell Cycle

autocrine signaling

cell secretes ligand

ligand binds to receptors on the cell that secreted the ligand

“auto” = self

juxtacrine signaling

direct contact between cell that is sending ligand and cell that’s receiving ligand

paracrine signaling

ligand travels a short distance to receptor (ex: neurotransmitters)

endocrine signaling

special ligands “hormones” travel a long distance

ligands interact with specific ______ cells

target cells

hydrophilic ligands bind to the receptor found ON… what does this do

membrane; triggers chemical reactions in cell

hydrophobic ligand pathway

1. goes THRU membrane

2. binds to intracellular receptors in cytosol

3. ligand crosses nuclear membrane

4. binds to DNA - changes expression of genes

3 major steps of signal transduction pathway

1. reception

2. transduction

3. response

signal amplification

type of transduction

signaling cascades (series of chemical reactions), amplifying cell’s response to signal

kinases

type of transduction

transfer phosphate groups - activates those molecules

molecules that activate other molecules by phosphorylation

phosphatases

type of transduction

remove phosphate groups; inactivates those molecules

response

result generated by ligand

negative feedback

returns system to its original condition and helps maintain homeostasis (ex: sweat when hot)

stimulus UP response DOWN

positive feedback

magnifies cell processes (ex: oxytocin - uterine wall childbirth contractions)

stimulus UP response UP

phases of the cell cycle

1. G1

2. S

3. G2

4. M (mitosis)

G1 phase

call grows, prepares for replication

S phase

DNA replication; now each chromosome has 2 identical chromatids held together by centromere

G2

growth; prepare for mitosis

mitosis goes from___n —> ___n or ___ploid to ___ploid

2n —> 2n (diploid —> diploid)

phases of mitosis

1. prophase

2. metaphase

3. anaphase

4. telophase

5. cytokinesis

prophase

• spindle fibers form

• centromeres move to opposite poles of cells

• chromosomes condense

• nuclear envelope disinigrates

metaphase

• nucleus is gone

• chromosomes line up along “equator”

• spindles attach to centromeres

anaphase

chromosomes are pulled to opposite sides of cell

telophase

chromosomes are on opposite sides of the cell, new nuclei form

cytokinesis

cytoplasm splits between the 2 nuclei, creating 2 new daughter cells

the result of mitosis is how many cells and what type

2 genetically identical, diploid somatic cells

centriole

where spindle fibers come out

kinetochore

center of chromosome, where the spindles attach

cyclin

internal regulator of the cell, the binding of cyclins and CDKs signals for new phases of the cell cycle to start and end, their abundance depends on the abundance onf CDKs

molecule whose concentration rises and falls throuhgout the cell cycle

CDK (cycling-dependent kinase)

internal regulator of the cell cycle, their activation helps progress the cell cycle; always present

kinases that respond to rising/falling cyclin levels

Explain how the interactions between cyclins and cyclin-dependent kinases (CDKs) control the cell cycle.

high cycling levels —> cycling binds with CDKs forming MPF (maturation promoting factor). cell passes G2 checkpoint and move onto M phase

During M phase, cycling is broken down. Process repeats in each daughter cell

G0

phase where cells never divide once they’ve fully matured or due to environmental conditions (nerve cells, muscle cells)

cAMP (cyclic AMP)

secondary messenger

what does a secondary messenger do?

relay the signals from reception