Cells and proteins - 3

Question 1

what makes up the fluid mosaic model?

Answer 1

• phospholipid bilayer

- globular protein

Question 2

what does the hydrophobic centre of a membrane allow?

Answer 2

allows oxygen and carbon dioxide to pass through since they are small non-polar molecules

Question 3

what does the hydrophobic centre act as a barrier to?

Answer 3

acts as a barrier to the passage of charged ions and most polar molecules

Question 4

what are integral proteins?

Answer 4

proteins embedded in the bilayer

Question 5

what type of interactions do integral proteins form?

Answer 5

form strong hydrophobic interactions

Question 6

what type of integral proteins span across the width of the membrane?

Answer 6

transmembrane proteins

Question 7

what are peripheral proteins?

Answer 7

proteins that are not embedded in the bilayer

Question 8

what type of bonds do peripheral proteins form?

Answer 8

form weak bonds to the surface of the membrane

Question 9

whereabouts on the membrane do peripheral proteins bond to?

Answer 9

• heads of phospholipids

- integral proteins

Question 10

what is a ligand?

Answer 10

any substance that can bind to a protein

Question 11

what does a binding of a ligand cause?

Answer 11

• conformational change (change in shape)

- change in function

Question 12

what does protein folding produce?

Answer 12

ligand-binding sites on the surface if the protein

Question 13

what are ligand-binding sites complementary to?

Answer 13

complementary shape and chemistry to their ligand

Question 14

what is DNA tightly coiled around?

Answer 14

histone proteins to form nucleosomes

Question 15

how does DNA act as a ligand?

Answer 15

DNA binds since the negative-charged phosphates of DNA interact with positive-charged R groups on outside of histone

Question 16

the active site of an enzyme is an example of what?

Answer 16

a ligand-binding site

Question 17

when enzymes bind to the substrates is there a high or low affinity?

Answer 17

high affinity

Question 18

what is a modulator?

Answer 18

molecules that bind to secondary sites of enzyme

Question 19

what is a negative modulator?

Answer 19

inhibits enzyme activity

Question 20

what is a positive modulator?

Answer 20

activates enzyme activity

Question 21

how do modulators occur?

Answer 21

by altering the affinity to a substrate

Question 22

what is co-operativity?

Answer 22

when binding of a molecule to a subunit increases affinity for the other subunits until saturated

Question 23

explain haemoglobin as an example of co-operativity

Answer 23

• as oxygen binds to one subunit
• affinity of the other subunits change
• increases number of oxygen collected

Question 24

what does addition/removal of a phosphate cause?

Answer 24

causes a reversible conformational change

Question 25

what is the addition/removal of a phosphate carried out by?

Answer 25

carried out by enzymes

Question 26

what is the addition/removal of a phosphate important for?

Answer 26

important in regulation of activity of proteins

Question 27

what do kinases do?

Answer 27

- catalyse phosphorylation | - adds phosphates

Question 28

what do phosphates do?

Answer 28

- catalyse dephosphorylation | - removes phosphates

Question 29

what are ATPases?

Answer 29

enzyme that releases a phosphate from ATP

Question 30

how to ATPases work?

Answer 30

by phosphorylating themselves

Question 31

during muscle contraction, what forms the cross bridges?

Answer 31

binding of myosin head to actin

Question 32

during muscle contraction, what does the binding of ATP cause?

Answer 32

causes a conformational change

Question 33

during muscle contraction, what causes the third conformational change?

Answer 33

the myosin head rebinding to actin

Question 34

during muscle contraction, when the ADP + Pi is released from myosin, what does the myosin do?

Answer 34

myosin head swings back dragging actin filament along

Question 35

what are the two types of transmembrane proteins?

Answer 35

- channel proteins | - transporter proteins

Question 36

what is the purpose of transmembrane proteins?

Answer 36

needed to allow movement of molecules into and out of the cell

Question 37

is ATP required to move molecules through channel proteins?

Answer 37

no it is passive transport

Question 38

what are aquaporins?

Answer 38

ungated channel proteins which allow the free movement of water molecules

Question 39

what allows ions to move through a ligand gated channel?

Answer 39

when a protein or ligand attaches to the channel causing conformational change

Question 40

when will a voltage-gated channel open?

Answer 40

opens if there is an ion concentration difference on the inside and outside of cell

Question 41

if a transporter protein is active it requires what?

Answer 41

ATP

Question 42

what are the functions of the sodium potassium pump?

Answer 42

- maintenance of osmotic balance in cells | - generates an ion gradient in kidney tubules and neurons

Question 43

in the sodium potassium pump what changes the conformation to allow the Na ions to be released out of the cell?

Answer 43

a phosphate from hydrolysis of ATP binding to the pump

Question 44

how many sodiums bind to the sodium potassium pump?

Answer 44

3 Na

Question 45

how many potassiums bind to the sodium potassium pump?

Answer 45

2 K

Question 46

is the sodium potassium pump active or facilitated?

Answer 46

active

Question 47

what does the glucose symport do?

Answer 47

transports glucose from a low to high concentration

Question 48

is the glucose symport active or facilitated?

Answer 48

facilitated

Question 49

how many sodiums are transported in the glucose symport?

Answer 49

2 Na

Question 50

what are receptor proteins?

Answer 50

proteins that have specific binding sites for extracellular hydrophilic signal molecules

Question 51

what causes a conformational change in receptor proteins?

Answer 51

the binding of chemical signal which triggers a signal transduction pathway

Question 52

when a signal transduction pathway is triggered what does this cause?

Answer 52

causes a specific intracellular response

Question 53

what can a signal transduction pathway involve?

Answer 53

- activation of enzyme or G protein - a change in uptake or secretion of molecules - activation of proteins that regulate gene transcription - rearrange the cell's cytoskeleton

Question 54

what is nerve transmission?

Answer 54

a wave of depolarisation of a resting potential

Question 55

what is nerve transmission stimulated by?

Answer 55

stimulated by a signal molecule to open ligand gated channels at synapse

Question 56

what does the opening of a ligand-gated channel in nerve transmission allow?

Answer 56

allows enough Na ions movement to undergo depolarisation

Question 57

once depolarisation has passed, what makes the neuron's membrane potential negative again?

Answer 57

- voltage-gated ions close - stops Na moving in - K moves out

Question 58

what are the 5 changes in membrane potential as an impulse is passed along a neuron?

Answer 58

- resting potential - depolarisation - action potential - repolarisation - hyperpolarisation