Unit 4

Autocrine Signaling

Autocrine Signaling

A form of signaling where a cell sends a signal to itself.

Direct Contact

Type of cell-to-cell communication that occurs at cell junctions.

• EG: Plasmodesmata, gap junctions

Local Communication

Cell-to-cell communication that occurs over short distance (usually targeting adjacent cells).

Paracrine Signaling

Type of local signaling that has a cell release messengers that diffuse across the extracellular membrane and attach to a nearby cell’s receptor.

Synaptic Signaling

Type of local signaling that has a neuron release a neurotransmitter to travel across the synaptic cleft and be received at the axon terminal.

Endocrine Signaling

A type of long distance communication that uses hormones that travel throughout the bloodstream and are received by different organs across the body.

EG: Insulin

Reception

The detection and receiving of a ligand by the receptor.

G-Protein Coupled Receptor

A receptor that works with the help of a G protein that serves a variety of roles. They are the largest class of known membrane receptors.

G-Protein

A protein that binds to GDP/GTP (a molecule similar to ATP).

Ligand-Gated Ion Channel

A receptor with a region that acts as a “gate” for ions whenever the receptor has its shape changed by a ligand attaching.

Transduction

The conversion of an extracellular signal to an intracellular signal that will bring a cellular response.

Kinase

Protein responsible for turning ATP into ADP by taking a phosphate group and transferring the phosphate group to another molecule

• Can form cascades

Phosphatase

Protein responsible for taking a phosphate group from a molecule and giving it to an ADP molecule, turning ADP into ATP.

Response

A cell process is triggered or altered in some way

Homeostasis

Values for various physiological conditions that the body tries to maintain

• EG: Blood sugar, water, wtc

Transduction

The conversion of an extracellular signal to an intracellular signal that will bring a cellular response.

Cell Cycle

The life and growth cycle of a cell.

Local Communication

Cell-to-cell communication that occurs over short distance (usually targeting adjacent cells).

S Phase

DNA replication and chromosome duplication occurs.

• A chromosome makes a copy of itself, and this copy forms sister chromatids attached by a centromere.

• Centrosomes are also duplicated during this stage.

  • Note: Plants do not have centrosomes.

G₂ phase

The conversion of an extracellular signal to an intracellular signal that will bring a cellular response.

Endocrine Signaling

Products of mitosis

Prophase

• Chromatin condenses and forms the chromosome shapes we are familiar with. 

• Nucleolus disappears.

• Duplicated chromosomes appear as sister chromatids.

• Mitotic spindle begins to form.

Prometaphase

• Nuclear envelope fragments.

• Microtubules enter the nuclear area and some begin to attach to kinetochores.

Kinetochore

• Protein complex on the sides of centromeres

• Is where the mitotic spindle attaches to

Metaphase

• Mitotic spindle at opposite poles of the cell.

• Chromosomes line up at the metaphase plate. 

• Microtubules (the mitotic spindle) are attached to each kinetochore.

Anaphase

• Sister chromatids separate and move to opposite ends of the cell due to the microtubules shortening

• Cell elongates

Telophase

• Two daughter nuclei form

• Nucleoli reappear

• Chromosomes become less condensed. 

Cytokinesis in animal cells

A cleavage furrow appears due to the contractile ring of the actin filaments, essentially “pinching” the cell to split it.

Cytokinesis in plant cells

• Protein complex on the sides of centromeres

• Is where the mitotic spindle attaches to

Centrosomes

The organelle centrioles are stored in when they are not in use.

G₀ checkpoint

• Some cells stay in this phase forever (muscle/nerve cells). 

• Some cells can be called back into the cell cycle.

• In this phase, a cell will not be actively preparing to divide.

G₂ checkpoint

• Checks for completion of DNA replication and DNA damage during the S Phase.

• The cell passing this checkpoint would have the cell proceed to the mitosis stage.

M checkpoint

• Checks for microtubule attachment to chromosomes at the kinetochores at metaphase

Cyclins

• Regulatory enzymes that activate CDKs

• Vary in concentration

Cyclin-dependent Kinases

• CDKs for short

• Protein complexes that have a constant concentration

• Each CDK has its own regulatory effect.

Metastasis

When cells separate from the tumor and spread elsewhere in the body.

Diploid

An cell with two copies of a chromosome.