1.3 Membrane Proteins Flashcards Preview

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Flashcards in 1.3 Membrane Proteins Deck (36)
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1
Q

what do regions of hydrophobic R groups allow

A

strong hydrophobic interactions that hold integral membrane proteins within the phospholipid bilayer

2
Q

what are the different types of membrane proteins

A

integral and peripheral

3
Q

what do integral membrane proteins interact with

A

they interact intensively with the hydrophobic region of membrane phospholipids

4
Q

what are integral proteins

A

transmembrane proteins

5
Q

what do peripheral membrane proteins have

A

hydrophilic R groups on their surface and are bound to the surface of membranes, by ionic and hydrogen bond interactions

6
Q

what do peripheral membrane proteins interact with

A

they interact with the surface of integral membrane proteins

7
Q

what is the phospholipid bilayer

A

a barrier to ions and most uncharged polar molecules

8
Q

how do small molecules pass through the bilayer

A

small molecules such as oxygen and carbon dioxide pass through the bilayer by simple diffusion

9
Q

what is facilitated diffusion

A

the passive transport of substances across the membrane through specific transmembrane proteins

10
Q

what do cells have to perform specialised functions

A

different cell types have different channels and transporter proteins

11
Q

most channel proteins in animal and plant cells are

A

highly selective

12
Q

what are channels

A

multi-subunit proteins with the subunit arranged to form water-filled pores that extend across the membrane

13
Q

what do channels have to prevent diffusion

A

some channel proteins are gated and change conformation

14
Q

what are the different types of channel protiens

A

ligand-gated

voltage-gated

15
Q

what are ligand-gated channels controlled by

A

the binding of signal molecules

16
Q

what are voltage-gated channels controlled by

A

changes in ion concentration

17
Q

what are the different types of proteins involved in transporting substances

A
channel proteins (facilitated diffusion (passive))
transporter proteins (facilitated diffusion (passive))
protein pumps
18
Q

why do transporter proteins bind to the specific substance

A

to be transported and undergo a conformational change to transfer the solute across the membrane

19
Q

why do transporters alternate between two conformations

A

so that the binding site for a solute is sequentially exposed on one side of the bilayer, then the other

20
Q

what does active transport use

A

pump proteins that transfer substances across the membrane against their concentration gradient

21
Q

pumps that mediate active transport are

A

transporter proteins coupled to an energy source

22
Q

what is required for active transport

A

a source of metabolic energy

23
Q

why do some active transport proteins hydrolyse ATP directly

A

to provide the energy for the conformational change required to move substances across the membrane

24
Q

what hydrolyses ATP

A

ATPases

25
Q

what determines the transport of the solute for a solute carrying a net charge

A

the concentration gradient and the electrical potential difference combine to form the electrochemical gradient that determines the transport of the solute

26
Q

how is a membrane potential created

A

(an electrical potential difference) when there is a difference in electrical charge on the two sides of the membrane

27
Q

what do ion pumps use energy for

A

ion pumps, such as the sodium-potassium pump, use energy from the hydrolysis of ATP to establish and maintain ion gradients

28
Q

how does the sodium-potassium pump transport ions

A

transports ions against a steep concentration gradient using energy directly from ATP hydrolysis

29
Q

what does a sodium-potassium pump transport

A

actively transport sodium ions out of the cell and potassium ions into the cell

30
Q

what are the stages that the sodium-potassium pump goes through

A
high affinity for sodium ions inside the cell
binding occurs
phosphorylation by ATP
conformation changes
affinity for sodium decreases 
sodium ions released outside of the cell
potassium ions bind outside of the cell
dephosphorylation 
conformation changes
potassium ions taken into cell
affinity returns to start
31
Q

how many ions are transported through the cell membrane

A

for each ATP hydrolysed, three sodium ions are transported out of the cell and two potassium ions are transported into the cell.
this establishes both concentration gradients and an electrical gradient

32
Q

why is the sodium-potassium pump important

A

it is found in most animal cells and accounts for a high proportion of the basal metabolic rate in many organisms

33
Q

what does the sodium gradient in the small intestine lead to

A

the sodium gradient created by the sodium-potassium pump drives the active transport of glucose

34
Q

what happens with the sodium-potassium pump in intestinal epithelial cells

A

the sodium-potassium pump generates a sodium ion gradient across the plasma membrane

35
Q

what is the glucose transporter responsible for

A

the glucose symport transports sodium ions and glucose at the same time and in the same direction

36
Q

how are sodium ions and glucose transported in the concentration gradient

A

sodium ions enter the cell down their concentration gradient, the simultaneous transport of glucose pumps glucose into the cell against its concentration gradient