Cell Communications

Question 1

where can cellular communication occur?

Answer 1

between cells
-chemical
-electrical

within cells

Question 2

describe how electrical transmission happens between cells?

Answer 2

direct contact via gap junctions

Question 3

what do gap junctions allow?

Answer 3

flow of current to go from cell to cell

Question 4

describe features of electrical transmission between cells.

Answer 4

-rapid transmission in both directions
-linked cells can act as 1 unit (syncytium)
eg. cardiac and some smooth muscle

Question 5

describe 3 types of chemical transmission.

Answer 5

cell to cell = synapse
cell to many cells = paracrine
many cells to many cells = endocrine

Question 6

describe 3 types of chemical transmission.

Answer 6

cell to cell = synapse
cell to many cells = paracrine
many cells to many cells = endocrine

Question 7

describe cell to cell chemical transmission through a synapse.

Answer 7

-effect depends on transmitter and the receptor it acts on
-one way transmission
-common in nervous system

Question 8

describe the sequence of events in cell to cell chemical transmission through a synapse.

Answer 8

1. impulse arrives at terminal of presynaptic cell
2. trfansmittwe released from storage vesicle
3. transmitter diffuses in synaptic cleft
4. transmitter binds to receptor on postsynaptic cell
5. alters post synaptic cell

Question 9

what happens in cell to cell chemical transmission when the transmitter alters the post synaptic cell?

Answer 9

‘excitatory’ eg. impulse generated; muscle contracts; gland secretes

‘inhibitory’ cell is switched off

Question 10

describe paracrine communication.

Answer 10

• one cell communicates with several cells locally
• often used by defence cells (inflammation)
• can be part of ‘cascade’ of reactions

Question 11

describe autocrine communication.

Answer 11

chemical acts on cell releasing it (feedback)

Question 12

describe endocrine transmission.

Answer 12

chemical sent to all parts of body via blood stream

hormone acts only on cells with correct membrane receptor protein (target cells)

Question 13

which is better for communication in organisms, nerves or hormones?

Answer 13

not have advantages and disadvantages depending on circumstances.

Question 14

describe communication by nerves.

Answer 14

actions specific or localised.
quick impulse transmission.
suitable for rapid responses.

Question 15

give examples of communication by nerves.

Answer 15

• control of voluntary muscle contraction
• sensory systems
• salivary gland response
• control of blood pressure

Question 16

describe communication by hormones.

Answer 16

affect many cells in different parts of body.
coordinated, body-wide actions.
slow to act by effect persists.

Question 17

give examples of communication by hormones.

Answer 17

• gastro-intestinal gland responses
• control of metabolism and growth
• regulation of menstrual cycle

Question 18

what is the first messenger in intracellular communication?

Answer 18

chemical transmitter which acts on receptor protein.

Question 19

how do first messengers act on receptors in intracellular communication?

Answer 19

passes through the target cell membrane and acts on receptors inside target cell.

Question 20

can first messengers enter the cell in intracellular communication?

Answer 20

not all but some can

Question 21

what are second messengers in intracellular communication?

Answer 21

various intracellular signalling molecules and pathways

Question 22

what is transcription?

Answer 22

RNA converted to protein

Question 23

what is translation?

Answer 23

translates DNA to mRNA to protein

Question 24

what are steroid transmitters?

Answer 24

lipids that can pass through outer cell membrane

Question 25

describe the process of steroid transmitters?

Answer 25

1. act on receptors inside the target cell 2. steroid-receptor complex acts on the DNA in nucleus to initiate protein synthesis 3. protein then alters cell function 4. these hormones have delayed action

Question 26

can peptide transmitters pass through cell membrane?

Answer 26

no

Question 27

out of steroid and peptide transmitters which one can pass through cell membrane?

Answer 27

steroid

Question 28

how to peptide hormones work on receptors?

Answer 28

- bind to plasma membrane receptors and set up series of reactions controlled by 'G proteins' - these activate 2nd messenger systems eg. cyclic AMP calcium ions

Question 29

describe the process of g-protein and cyclic AMP.

Answer 29

1. transmitter binds to membrane receptor 2. g-protein is activated by GTP 3. ATP (in cytosol) is converted to cyclic AMP bye enzyme adenyl cyclase 4. cAMP activates enzyme called protein kinase 5. this activates specific enzymes which catalyses chemical reaction 6. results in formation of molecule

Question 30

describe the process of calcium as a 2nd messenger.

Answer 30

1. transmitter binds to membrane receptor 2. this activates g-protein which activates enzyme: phospholipase C 3. this causes opening of Ca2+ channels and it enters by diffusion 4. Ca2+ binds to protein in the cytosol, here it is calmodulin 5. this regulates an enzyme which regulates a chemical reaction

Question 31

name a Ca binding protein? what is it involved in?

Answer 31

troponin involved in muscle contractions