AP Bio Unit 4: Cell Communication and Cell Cycle

Autocrine

This type of cell communication is when a cell sends signals to itself (maturation, or some response or change)

Paracrine

This type of cell communication is when a Cell sends signals to a nearby cell

Juxtactine

This type of cell communication is when a cell sends signals to another cell that it is physically connected to

Endocrine

This type of cell communication is when a cell signals from one type of tissue to another across long distances via the blood stream

Gap Junction Channel

Cells have physical contact. Through this, they may send and receive signals from each other.

Homeostasis

Stability or equilibrium

Quorum Sensing

 Bacteria release signals that allow them to activate when there are enough of them (ie activate pathogenicity)

Transduction and Amplification

The second step in a signal transduction pathway: After reception, a signal travels through a cell and is converted into multiple pathways

Cellular response

Step 3 in a signal transduction pathway

Intracellular Receptors

Not membrane proteins. When signal molecules are hydrophobic / nonpolar, they bind to these inner proteins.

Membrane proteins

These proteins receive polar signals that cannot diffuse through the phospholipid bilayer

Genome

 A cell’s genetic information / DNA

Chromosomes

DNA is packaged into these

Chromatin

Complex of DNA and proteins with chromosome building material

Sister chromatids

After DNA replication, a chromosome becomes densely folded into 2 _________

Centromere

• Each chromosome has a _______ (region containing specific DNA sequences)

Mitosis

Division of genetic material in a nucleus

Cytokinesis

 Division of the cytoplasm

Interphase

90% of the cell cycle → Dividing and growing chromosomes in preparation for division

G1

 “First Gap Phase”

Cell comes out of mitosis and grows in preparation for DNA replication

Checkpoints:

-Growth Factors stimulate signals inside cells, rising cyclin concentration 

-p53 protein: if DNA is damaged, p53 stops progression by inhibiting CDK-cyclin.

S

 “Synthesis”

Cell replicates DNA. At the end of this phase, a cell has 2 sets of chromosomes.

Checkpoint: DNA is monitored for replication errors

-Once the S-phase cyclins reach a threshold, CDK-cyclin signals the cell to duplicate DNA.

-Breaks in DNA strands activate the ATM protein. This stops the cycle and activates repairing proteins.

G2

 “Second Gap Phase”

Cell continues to grow and prepare for division. All chromosomes have to be fully replicated w/o dmg.

Checkpoint:

-If there is no DNA damage, CDK-cyclin activates

-If there is DNA damage, p53 protein will stop the cell cycle. If damage is impossible to fix, p53 can initiate cell death.

Mitosis

 the process of splitting a cell into two daughter cells

It is used for growth, reproduction, and healing (replace + repair)

Checkpoint: Check if all sister chromatids attached to the mitotic spindle

- M-phase cyclins and CDKs activate a protein complex called the anaphase-promoting complex / cyclosome (APC/C). THis is activated when all chromosomes are attached to the mitotic spindle. APC/C breaks the centromeres of the chromosomes

- WHen chromosomes are not properly attached, MAD proteins inhibit the APC/C and prevent entry into anaphase

IPMAT

Order of Mitosis

Prophase

Step 1 of mitosis

-  Chromatin fibers become tightly coiled

- Duplicated chromosome sister chromatids

- Nuclear envelope fragments

Metaphase

Step 2 of mitosis

- Chromosomes line up in cell center

- Each sister chromatid is attached to a spindle fiber

Anaphase

The third and shortest phase of mitosis

- Sister chromatids part

- Cell elongates: 2 ends have complete chromosomes 

Telophase

The fourth and last phase of mitosis

- 2 daughter nuclei in cell

- Mitosis is done

- Chromosomes are less condensed

Tumor supression proteins

These proteins stop the cell cycle if needed at various checkpoints

Apoptosis

Programmed cell death

G0

A cell can enter this phase when it no longer divides 

• Can re enter cell cycle from appropriate cues

• May be held in specific stage in cell cycle

• Performs specific structural functions