Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Membranes > Membrane Transport > Flashcards

Membrane Transport Flashcards

1
Q

How does a voltage clamp work?

A
  • electrode in axon and out of axon

- measure the voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How does a patch clamp work?

A
  • study native membrane

- study changes occurring, the potential across the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does a pure membrane measurement work?

A
  • Can incorporate single protein into bilayer

- Study of opening + closing of channels in real time (minuscule changes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why should we have transport across membranes?

A
  • uptake of nutrients , cofactors & minerals
  • removal of toxic waste
  • move biomolecules from one compartment to another ( such as in glycolysis, moving products from cytoplasm to the mitochondria)
  • control movement of signalling molecules/ ions between compartments and cells
  • production of ATP by H+ gradient in mitochondria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the different types of membrane transport?

A
  • passive diffusion (diffusion of solutes down a concentration gradient, no proteins involved)
  • facilitated diffusion (diffusion of solution down a conc gradient, proteins involved)
  • active transport (requires energy, solute moves against conc gradient, proteins involved)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is Fick’s law?

A
  • diffusion is directly proportional to the conc gradient across the membrane
  • J = -D change con/ change position
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does permeability affect diffusion across a membrane?

A
  • water, hydrophobic molecules and small, uncharged polar molecules are able to cross straight though
  • large and charged/ polar molecules and ions cannot
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is Graham’s Law?

A

rate of effusion or diffusion of a gas is inversely proportional to the square root of its molecular weight

  • the bigger the molecule, the less likely to diffuse
  • more hydrophobic, more likely to diffuse
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is effusion?

A

The process in which gas escapes through a small hole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What experiment was used to conclude that membrane associated proteins must be involved with facilitated diffusion?

A
  • isolate membranes from RBC and measure permeability constant for different solutes
  • experiment undertaken in phospholipid membranes alone all conform to ideality
  • experiment with RBC membranes & protein denaturant mean that all solutes now conform to ideality
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is facilitated diffusion?

A
  • movement down a conc gradient, requiring proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the facilitated diffusion kinetics equation? (Hint: similar to MM)

A

J = Jmax[S] / Km + S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What factors affect facilitated diffusion?

A
  • temp
  • pH
  • protein denaturing agents
  • solute specificity (e.g Glucose transporter)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the methods of facilitated diffusion?

A
  • using selective channels

- using carriers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are ionophores?

A

a substance which is able to transport particular ions across a lipid membrane in a cell
- penetrates through membrane and releases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the types of selective channels?

A
  • non-gated
  • ligand gated
  • electrically or potential gated
  • stress gated
17
Q

Describe the characteristics of non-gated selective channels? Inc example

A
  • always open
  • selectively through charge and site
  • e.g. aquaporins
  • highly selective
  • only let water in
  • impermeable to charged molecules
18
Q

Describe the characteristics of ligand gated selective channels? Inc example

A
  • ligand alters conformation allowing molecule to go through
  • e.g. nicotinic acetylcholine receptors (nAChR)
  • binding site at the top
  • conformational change opens iron pore
  • ACh/ nicotine is the ligand
  • once bound it twists, allows Na/K channels to open
19
Q

Describe the characteristics of potential gated selective channels? Inc example

A
  • change in potential (such as in axons) opens the gate
  • e.g. Voltage gated sodium channels (NavMs)
  • channel domain in the middle
  • changes in charge causes domain to change position and pivot in (mechanical change)
20
Q

Describe the characteristics of stress gated selective channels? Inc example

A
  • under pressure, conformational change occurs and gate opens
  • e.g. MscL
  • lots of water intake thins the membrane due to osmotic pressure
  • molecule stretches out, opening of pore and release of pressure
21
Q

How do specific plasma membrane carriers work?

A
  • binding of one side causes conformational change and opens on the other side
  • never opens up on both sides at the same time
22
Q

How do co-transporters work?

A
  • antiporters and symporters utilise the energy of movement of one solute down its conc gradient to move another solute against its gradient
23
Q

What are the 2 types of co-transporters?

A

Symporters
- both solutes go in the same direction
Antiporters
- solutes go in the opposite direction

24
Q

How does primary active transport occur?

A
  • requires energy in the form of ATP

- transports solute against the concentration gradient by directly hydrolysing ATP

25
Q

Why do pumps and co-transports transport solutes at a slower rate than channels?

A

Pumps, co-transporters and carriers have to undergo numerous conformational steps in order to transport the solute
- channels are a pore and so allow fast movement

26
Q

How does group translocation work?

A
  • multicomponent system
  • example is the PEP group translocation phosphotransferase system
  • utilises energy from glucose influx through the membrane to translocate other solutes
27
Q

How can ion gradients be used to transport other molecules? Glucose example, Amino acid example, Sugar example.

A
  • using co-transporters
  • glucose uptake into mammalian cells using Glucose/Na+ co-transporter
  • amino acids uptake into cells using a.a./Na+ co-transporter
  • sugar uptake into bacteria cells such as in the lac operon using Lactose/H+ co-transporter
28
Q

How does the lactose permease co-transporter work?

A
  • proton binds first
  • lactose binds after
  • flips and causes conformational change
  • release of the lactose first
  • when releasing the H+, the protein changes back
29
Q

What is the structure of the sodium potassium pump? (Na+/K+ ATPase)

A

Tetramer α2 β2. The α subunits have 10 α-helices. There is an A domain (Actuated domain) that sends the signal for conformation change. There is a P domain (Phosphorylated domain) where binding occurs. There is a N domain (Nucleotide binding domain)

30
Q

What happens during the action of the sodium potassium pump work?

A
  • Active transport

- Each ATP hydrolysis= 3 Na+ pumped out and 2K+ pumped inside.

31
Q

What is the affinity like in the E1 and E2 conformations of the sodium potassium pump?

A 
E1: (inside face)
- high affinity sites for Na+ 
- low affinity sites for K+
E2: (outside face)
- high affinity sites for K+
- low affinity sites for Na+
32
Q

How does the sodium potassium pump work?

A 
The pump exists in 2 major conformations, E1 and E2.
During E1: (inside face)
1. Binding of ATP opens up for 3Na binding
2. Phosphorylation occurs (ATP ------> ADP + P)
- causes conformational change
- stimulates the release of 3Na outside
During E2: (outside face)
3. Exchange Na for 2K
- stimulates hydrolysis of Pi
- release of Pi
4. Release of 2K inside
Back to the beginning
33
Q

What does Ca2+ regulate?

A
  • neurotransmitter function
  • hormone function
  • muscle contraction
  • cell growth / differentiation
  • cell death
34
Q

How does Ca2+ regulate heart muscle contraction?

A
  1. A high conc of Ca2+ outside means that the calcium moves in to the heart cell
    - leading to contraction of the cell
  2. Na/Ca exchange stops contraction to happen all the time as calcium leaves the cell
    - Ca leave the cell and Na goes into the cell
  3. Na/K pump releases Na out of the cell to maintain the gradient (low Na in cell) so that step 2 can occur
35
Q

How do poisons/ drugs increase heart rate?

A

Drugs inhibit step 3 (Na/K pump) so that Na+ stays in the cell

  • this means that the conc. gradient will not be as steep anymore
  • Ca2+ is able to stay in the cell and contract the heart for longer
36
Q

How does the Ca2+ ATPase protein work?

A 
The pump exists in 2 major conformations, E1 and E2.
E1 State in endoplasmic reticulum
1. Add ATP
- Opens up E1 state 
- High affinity for 2Ca2+
2. Binding of 2Ca2+
- Makes ATP------>ADP+P
E2 state:
3. Conformational change
4. Release of 2Ca2+
CYCLE

Membranes (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions