Unit 4

Direct contact communication

Communication by cell-cell contact

Cell-cell recognition

Complementary cell-surface molecules between adjacent cells can interact and bind to each other

Long-distance signaling

Using hormones that produce a response in target cells that may be far from the signaling cell (Plants use vascular tissue or through air. Animals use the endocrine system.)

Paracrine signaling

A signaling cell will release chemical messages like local regulators and ligands that travel short distance through the extracellular fluid and cause a response in a nearby target cell

Synaptic signaling

Occurs in animal nervous systems where neurons secrete neurotransmitters that diffuse across the synaptic cleft and bind to receptors

Autocrine signaling

A cell signals to itself by releasing a ligand that binds to receptors on the same cell to initiate signaling (regulation via feedback)

Cell surface receptors

Most common type of receptor involved in signal pathways that work with ligands outside of the cell and sends signal down to the nucleus.

Ligand-binding domain

Area that interacts with the ligand

Transmembrane domain

Hydrophobic region that spans the plasma membrane

Intracellular domain

Region inside the cell that transmits a signal

Second messengers

Small, non-protein intracellular molecules or ions that rapidly relay and amplify signals from cell-surface receptors.

Protein kinase

Enzymes that relay and amplify the message by transferring a phosphate group from ATP to a protein = temporary

Protein phosphatase

Enzymes that remove phosphate groups from proteins

Intracellular receptors

Found in the cytoplasm or nucleus of the target cell. Binds to ligands that can pass through the plasma membrane.

Cross talk

A protein kinase in one pathway, may phosphorylate proteins in another pathway as well.

Negative feedback

Most common feedback mechanism that reduces the effect of the stimulus.

Positive feedback

This type of feedback increases the effect of a stimulus.

Kinetochore

Proteins attached to the centromere that link each sisters to the mitotic spindle.

Interphase

Where cells spend 90% of their time. The cell is growing and getting ready for division.

G1 phase

The cell is metabolically active and carries out normal functions. Duplicates organelles and cytosolic components

S phase

DNA replication takes place. DNA is in the form of chromatin and replicates to form two sister chromatids connected at a centromere

G2 phase

Final growth and preparation for mitosis. Protein synthesis occurs, and ATP is produced in large quantities.

Prophase

Chromosome condenses, nucleoli disappear, mitotic spindle begins to form, and centrosomes move away from each other.

Prometaphase

Chromosomes condense further, nuclear envelope breaks down, mitotic spindle grows and microtubules enter nuclear area with some attaching to kinetochores.

Metaphase

Centrosomes are at opposite poles, microtubules are attached to each kinetochore, and chromosomes line up at the metaphase plate

Anaphase

Paired sister chromatids separate and move to opposite ends of the cell due to the microtubules shortening, and cell elongates.

Telophase

Mitotic spindle breaks down, and two daughter nuclei forms.

Cytokinesis

The division of the cytoplasm. For animals, cleavage furrow appears, and for plants, vesicles produced by the Golgi travel to the middle of the cell and form a cell plate.

Checkpoints

Control points that regulate the cell cycle. G1, G2, and M.

Cyclins

Proteins that are synthesized and degraded at specific stages of the cell cycle

Cyclin-dependent kinases (CDK)

Enzymes that are only active when its specific cyclin is present