Cells and proteins - 4

Question 1

where are the prosthetic group retinals found?

Answer 1

in bacteriorhodopsin molecules in membrane

Question 2

what do retinals do?

Answer 2

absorb energy

Question 3

what is the energy absorbed by retinals used to do?

Answer 3

used to pump protons through the bacteriorhodopsin

Question 4

how is a proton gradient generated across the membrane?

Answer 4

by protons being pumped through the bacteriorhodopsin

Question 5

how is ATP generated?

Answer 5

by hydrogen ions diffusing back through membrane through ATP synthase

Question 6

how is chemical energy produced in plants?

Answer 6

converting light energy through photosynthesis

Question 7

in plants, what does the absorbed energy drive?

Answer 7

drives a flow of electrons along the electron transport chain

Question 8

what are protons pumped across in plants?

Answer 8

across the thylakoid membrane into the stroma

Question 9

what is a retinal?

Answer 9

a prosthetic group which is covalently bound to a polypeptide called opsin

Question 10

where is opsin found?

Answer 10

embedded in membranes inside photoreceptor cells

Question 11

what are the two classes of photoreceptor cells?

Answer 11

rods and cones

Question 12

describe a rod

Answer 12

• contains rhodopsin

- adapted to detect low levels of light

Question 13

describe a cone

Answer 13

• contains photopsin

- allows colour vision

Question 14

what is rhodopsin connected to?

Answer 14

connected to hundreds of G-proteins

Question 15

what amplifies a photon signal?

Answer 15

a cascade of proteins

Question 16

what causes a conformational change in rhodopsin?

Answer 16

a photons of light being absorbed

Question 17

what catalyses the breakdown of cGMP?

Answer 17

the hundreds of enzymes activated by hundreds of G-proteins

Question 18

when cGMP has been broken down into GMP what happens to the sodium channel?

Answer 18

sodium channel closes

Question 19

what happens if there a sufficient build up of Na?

Answer 19

membrane becomes hyper polarised and a nerve impulse is generated

Question 20

why are cones less sensitive than rods?

Answer 20

there are fewer photoreceptor cells

Question 21

in humans, how many photopsin does each cone cell have?

Answer 21

three photopsin

Question 22

what does each photopsin have a maximal sensitivity to?

Answer 22

a specific wavelength of light - red, green or blue

Question 23

how are different photopsin made?

Answer 23

made by combining retinal with different forms of opsin

Question 24

what do cells use to communicate?

Answer 24

• extra-cellular signalling molecules

- complimentary receptor proteins

Question 25

what are the main forms of coordination?

Answer 25

hormonal and nervous

Question 26

what is a target cell?

Answer 26

a cell that receives the signal

Question 27

how does a response come about in a cell?

Answer 27

- receptor molecules on target cell binds with a specific signal molecule - changes conformation of receptor cells - changes behaviour of target cells

Question 28

can hydrophilic signalling molecules pass through the membrane?

Answer 28

no

Question 29

where are the receptors in hydrophilic signalling molecules?

Answer 29

receptors are at the membrane not inside the cell

Question 30

name two types of hydrophilic signalling molecules?

Answer 30

- neurotransmitters | - peptide hormones (e.g insulin)

Question 31

what does hydrophilic signalling often involve?

Answer 31

- cascades activated my G-proteins | - phosphorylation by kinase enzymes

Question 32

how does hydrophilic signalling molecules move across the membrane?

Answer 32

signal is transduced across the membrane

Question 33

what is insulin?

Answer 33

a peptide hormone produced by pancreas

Question 34

name the glucose transporter

Answer 34

GLUT-4

Question 35

what is GLUT-4 triggered by?

Answer 35

triggered by phosphorylation events

Question 36

what is diabetes mellitus?

Answer 36

- deficiency in the effect of insulin | - loss of control of blood glucose levels

Question 37

what is type 1 diabetes?

Answer 37

failure to produce insulin

Question 38

what is type 2 diabetes?

Answer 38

loss of receptor function

Question 39

why can exercise help reduce the impact of type 2 diabetes?

Answer 39

triggers the recruitment of GLUT-4

Question 40

what is ADH?

Answer 40

peptide hormone

Question 41

when is ADH released?

Answer 41

released by pituitary gland in response to low blood water concentration

Question 42

what is the receptor protein for ADH?

Answer 42

G-protien

Question 43

where is G-protein found?

Answer 43

found in kidney nephron tubule (inside collecting ducts)

Question 44

what does ADH trigger?

Answer 44

triggers the recruitment of the channel protein aquaporin 2 (AQP2)

Question 45

what do aquaporins enable the cells to do?

Answer 45

- provides an efficient route for water to move across membranes - allows control of water balance in terrestrial vertebrates

Question 46

what does a failure to produce ADH lead to?

Answer 46

diabetes insipidus

Question 47

can hydrophobic signalling molecules pass through the membrane?

Answer 47

yes the molecules can diffuse through the membrane

Question 48

what hormone is released from the thyroid?

Answer 48

thyroxine

Question 49

what is the role of the thyroxine?

Answer 49

to control the metabolism

Question 50

what a thyroid hormone binds to a receptor protein what happens to the metabolic rate?

Answer 50

metabolic rate increases

Question 51

when is the transcription of Na/K ATPase inhibited?

Answer 51

when the receptor protein is bound to DNA in the absence of thyroxine

Question 52

in the absence of thyroxine, what happens to the metabolic rate?

Answer 52

metabolic rate decreases

Question 53

what are some examples of steroids?

Answer 53

- testosterone | - oestrogen

Question 54

when a steroid hormone passes through the membrane what acts as a transcription factor?

Answer 54

activated receptor proteins

Question 55

when a steroid hormone passes through the membrane what does it attach to and activate?

Answer 55

activates a receptor protein