Chapter 5 Study Questions (Part 1)

Question 1

how do cells communicate locally? (3)

Answer 1

• via gap junctions formed by connexons
• contact-dependent signaling
• autocrine and paracrine signaling

Question 2

how do cells communicate long-distance?

Answer 2

• endocrine/hormones
• signaling molecules/signaling pathways

Question 3

explain the difference between autocrine, paracrine, and endocrine

Answer 3

autocrine: source = target
paracrine: source ≠ target, close
endocrine: source ≠ target, far

Question 4

what is the source of histamine and how does it function as a paracrine signaling molecule?

Answer 4

histidine. causes capillary to dilate, gaps to increase, and increases blood flow to that area.

Question 5

signaling molecules can be either lipophilic or lipophobic. how does this affect the way a signaling molecule is synthesized?

Answer 5

LIPOPHILIC:
can’t be stored, has to be made on demand

LIPOPHOBIC:
stored in vesicles

Question 6

signaling molecules can be either lipophilic or lipophobic. how does this affect the way a signaling molecule is stored?

Answer 6

LIPOPHILIC:
carrier protein

LIPOPHOBIC:
stored in vesicles

Question 7

signaling molecules can be either lipophilic or lipophobic. how does this affect the way a signaling molecule is circulated in the body?

Answer 7

LIPOPHILIC:
attached to a carrier protein

LIPOPHOBIC:
in bloodstream, no problem

Question 8

signaling molecules can be either lipophilic or lipophobic. how does this affect its half life ?

Answer 8

LIPOPHILIC:
longer cause carrier protein hides it

LIPOPHOBIC:
can be filtered out or degraded, decreases half life

Question 9

what’s the difference between a neurotransmitter and a neurohormone?

Answer 9

T: goes to target with direct contact with source

H: into bloodstream for long distance

Question 10

list some examples of autocrine signaling

Answer 10

T cells (immune response)

Cardiac hypertrophy

Tumor cell growth is thought to be autocrine signaling gone wrong

Question 11

histamine binding to endothelial cell H1 receptors increases vessel permeability. how so? (2)

Answer 11

1) decreases the endothelial barrier by disrupting endothelial cell-cell junction contact areas

2) stimulates nitric oxide (NO) synthesis; causes vasodilation to increase blood flow

Question 12

what are the four forms of estrogen?

Answer 12

estrone
estradiol
estriol
estetrol

Question 13

why are lipophobic signaling molecules referred to as fast acting?

Answer 13

receptors are on the outside of the cell

water soluble

can’t get through lipid membrane

Question 14

why are lipophilic signaling molecules considered slow acting?

Answer 14

receptors are inside the cell, gets in no problem.

moves into nucleus. binds to DNA to start transcription, activates gene expression and translation, gets modified, but now you have the protein and can keep cloning it.

Question 15

describe the difference between fast ligand-gated ion channels and G protein-coupled receptors

Answer 15

fast: lots of them, rapid, short lived, specific. receptor and channel are same structure.

G: allows you to make lots of outputs with one input

Question 16

what are examples of 2nd messenger signaling molecules?

Answer 16

ATP becoming cAMP

Question 17

what does the phrase fast ligand-gated ion channel refer to?

Answer 17

receptor and channel are same structure

Question 18

describe secondary messenger signaling

Answer 18

small molecules and ions that relay signals received by cell-surface receptors to effector proteins

Question 19

what is the advantage of secondary messenger signaling?

Answer 19

allows for signal amplification

Question 20

what are connexons? what are they composed of?

Answer 20

small openings that let small molecules pass through.

composed of combinations of 6 connexin proteins

Question 21

what is contact-dependent signaling?

aka what does it involve?
how does it work?
when is it very important?

Answer 21

involves a receptor on the cell surface

surface molecules on one cell bind to surface molecules on an adjacent cell

very important during embryonic development where the circulatory and nervous systems haven’t developed yet

Question 22

signaling molecules can be either lipophilic or lipophobic. how does this affect its half life ?

Answer 22

LIPOPHILIC:
longer cause carrier protein hides it

LIPOPHOBIC:
can be filtered out or degraded, decreases half life

Question 23

signaling molecules can be either lipophilic or lipophobic. how does this affect its function ?

Answer 23

LIPOPHILIC:
tied up with a protein, only 1% available to be used

LIPOPHOBIC:
fully functional