Cell communication

Question 1

Ligand

Answer 1

a signaling molecule

Question 2

receptor protein

Answer 2

binds to ligand

Question 3

what can “sneak through” the membrane

Answer 3

a non-polar (hydrophobic) ligand

Question 4

direct contact

Answer 4

molecules on the surface of 1 cell are recognized by receptor son adjacent cell

Question 5

paracrine contact

Answer 5

signal released from a cell has an effect on neighboring cells

Question 6

endocrine signaling

Answer 6

hormones released from a cell affect other cells throughout the body

Question 7

a cell’s response to a signal often involves

Answer 7

activating or inactivating proteins

Question 8

phosphorylation

Answer 8

adding a phosphate onto a molecule

Question 9

protein kinase

Answer 9

enzyme that adds a phosphate onto a protein

Question 10

phosphatase

Answer 10

enzyme that removes a phosphate from a protein

Question 11

steroid hormones

Answer 11

• have a non-polar, lipid soluble structure
• cross the plasma membrane to steroid receptor
• usually affect regulation of gene expression

Question 12

intracellular response sequence

Answer 12

1. hormones cross plasma membrane and bind to cytoplasmic receptors
2. hormone binding alters receptor conformation so it no longer binds to receptor
3. hormone receptor complex translocate to nucleus
4. hormone receptor complex binds to DNA
5. cellular response is a change in gene expression

Question 13

membrane receptor types

Answer 13

• channel linked
• enzymatic
• G-protein coupled

Question 14

channel linked receptors

Answer 14

ion channel that opens in response to a ligand

Question 15

enzymatic receptor

Answer 15

receptor is an enzyme that is activated by the ligand

Question 16

G-protein coupled receptor

Answer 16

a G-protein assists in transmitting the signal

Question 17

G-protein

Answer 17

protein bound to GTP

Question 18

GPCR sequence

Answer 18

1. ligand binds to the GPCR
2. activates G-protein (and separates)
3. separation requires energy in the form GTP
4. trigger enzyme

Question 19

Once GPCR is activated

Answer 19

effector protein produces a 2nd messenger that triggers the cell response

Question 20

signaling by neurons

Answer 20

changes in the membrane potential are changes in the degree of polarization

Question 21

depolarization

Answer 21

cell membrane less polarized, less negative (relative to surrounding solution)

Question 22

hyperpolarization

Answer 22

cell membrane more polarized, more negative

Question 23

voltage gated

Answer 23

open and close to change membrane potential (sodium is positive so depolarizes gate)

Question 24

sodium acts —- while potassium acts —

Answer 24

fast, slower

Question 25

when potassium leaves it

Answer 25

repolarizes

Question 26

bacteria gives messages about

Answer 26

- nutrient availability - favorable environment - growing/dividing/dormant

Question 27

advantage to hyperpolarization

Answer 27

regulation - needs bigger stimulus to get next action potential

Question 28

if has multiple neurons firing

Answer 28

maintains muscle contraction (only happens in skeletal muscles)

Question 29

phototropism

Answer 29

growth in response to light

Question 30

cells that face away from light,

Answer 30

are growing

Question 31

gravitropism

Answer 31

response of a plant to the gravitational field of earth

Question 32

if plant is getting eaten by herbivore,

Answer 32

it will drop a leaf or send chemical signals to attract predators to eat the herbivore