Unit 4: Cell Communication and the Cell Cycle #1

Question 1

What are the three ways that cells communicate with each other?

Answer 1

Direct contact, local signaling, long-distance signaling.

Question 2

What is direct contact?

Answer 2

Communication through cell junctions in cells that are touching, material can pass freely between adjacent cells

Question 3

What are the two types of direct contact?

Answer 3

Gap junctions in animal cells and plasmodesmata in plant cells

Question 4

What is local signaling?

Answer 4

Local regulators will release chemical messages that travel a short distance through the fluid and trigger a response in the target cell

Question 5

What are the two types of local signaling?

Answer 5

Paracrine and synaptic signaling

Question 6

What is paracrine signaling?

Answer 6

When secretory cells release local regulators (can be hormones) via exocytosis to an adjacent cells (uses energy)

Question 7

What is synaptic signaling?

Answer 7

It occurs in the nervous systems, and neurons secrete neurotransmitters which diffuse across a synaptic cleft (space between the nerve and target cell) to reach the target cell (also uses energy)

Question 8

What is long distance signaling?

Answer 8

Animals and plants use hormones for long distance signaling

Question 9

How do plants use long distance signaling?

Answer 9

Plants release hormones that travel in the plant vascular tissue (xylem and phloem) or through the air to reach target tissues

Question 10

How do animals use long distance signaling?

Answer 10

Animals use endocrine signaling. Specialized cells release hormones into the circulatory system where they reach target cells. (cells that release are called glands.

Question 11

What are the three stages of cell signaling?

Answer 11

Reception (ligand binds to receptor), transduction (signal is converted), and response (a cell process is altered)

Question 12

What happens in the reception stage of cell signaling?

Answer 12

The ligand is received by a receptor in the target cell by binding to it, the receptors uses its area that interacts with other proteins to send a signal to another protein to initiate transduction

Question 13

What is a receptor?

Answer 13

A macromolecule that binds to a ligand (specific binding between the ligand and the receptor)

Question 14

Where are the two places that receptors can be found?

Answer 14

The plasma membrane and the intracellular space (including nucleus and cytoplasm)

Question 15

What are plasma membrane receptors?

Answer 15

The most common type of receptors that bind to ligands that are polar, water-soluble, and large (so they cannot slip through the membrane) and two examples are G protein coupled receptors (GPCRs) and Ligand-gated ion channels.

Question 16

What are intracellular receptors?

Answer 16

They are found in the cytoplasm or nuclear membrane, bind to ligands that are hydrophobic and can pass through the plasma membrane like steroids and thyroid hormones or glasses like nitric oxide (SO HORMONES!!!!)

Question 17

What happens in transduction?

Answer 17

The extracellular signal is converted to an intracellular signal that will bring about a cellular response, and it requires a sequence of changes in a series of proteins known as a signal transduction pathway.

Question 18

What are the two types of enzymes that phosphorylate in the signal transduction pathway?

Answer 18

One type of enzyme are protein kinases and they do phosphorylation (they put a phosphate on the protein) which amplifies signal in cell and protein phosphatases do dephosphorylation (taking a phosphate away) which shuts off pathways

Question 19

How is transduction amplified?

Answer 19

From each protein to the next, there are thousands of more created, amplifying the signal, AND there are second messengers which are small, non-protein molecules/ions that help relay the message and amplify the response.

Question 20

What is one second messenger?

Answer 20

Once common second messenger is cyclic AMP (remember that not all reactions have a second messenger)

Question 21

What happens in the response stage?

Answer 21

The final molecule in the signaling pathway converts the signal to a response that will alter a cellular process

Question 22

What are the three responses that could happen after a signal?

Answer 22

A protein that can alter membrane permeability, an enzyme that will change a metabolic process, or a protein that turns genes on or off.

Question 23

What are the two main categories of cell membrane receptors?

Answer 23

G protein coupled receptors (GPCRs) or ion channels

Question 24

What are GPCRs?

Answer 24

The largest category of cell surface receptors (IMPORTANT IN animal sensory systems)

Question 25

How to GPCRs work?

Answer 25

The GPCR is close to a G protein which can bind to GDP (like ATP), and there is also in enzyme and these are all INACTIVE until the ligand binds to the GPCR outside the cell, which changes the shape of the intracellular side which lets the G protein bind to the GPCR, and GDP becomes GTP, THEN part of the activated G protein will bind to the inactive enzyme which becomes active and uses the GTP to amplify the signal and start transduction and this leads to a cellular response.

Question 26

What are ion channels?

Answer 26

Ligand gated ion channels are located in the plasma membrane and are important in the nervous system

Question 27

How do ion channels work?

Answer 27

The receptors act like a gate for ions, so when a ligand binds to the receptor, it either opens or closes, allowing the diffusion of specific ions, and this initiates a series of events that lead to a cellular response (think neurotransmitters)