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Membrane Function Flashcards

1
Q

What is the major function of the plasma membrane?

A

Acts as a barrier
Transport
Signal Transduction

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2
Q

Which functional proteins are present at the lysosomal membrane ?

A

Hydrolytic enzymes

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3
Q

Which molecules are able to pass through the membranes passively?

A

Lipid soluble molecules
Hydrophobic molecules - N2, O2 etc.
Small uncharged polar molecules - H20, Urea, glycerol, CO2

these can all move either way through the membrane

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4
Q

What are the functions of the mitochondrial membranes?

A

Inner membrane
- Energy transduction

Outer membrane
- Acts as a barrier

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5
Q

What is Co transport?

A

The transport of 2 molecules simultaneously by one protein

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6
Q

What is the advantage of carrier mediated diffusion ?

A

Carrier mediated facilitated diffusion is more efficient than simple facilitated diffusion

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7
Q

What parallels can be drawn between enzyme kinetics and membrane transports?

A
  • Saturable - both have a maximum no. of molecules/substrate that are carried at a given time
  • Specificity - Transporters/enzymes are specific to their substrate/molecule
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8
Q

What are the 2 types of membrane transport?

A
  1. Passive

2. Active

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9
Q

What occurs at the peroxisomal membranes?

A

Fatty acid oxidation

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10
Q

What is Kt (AKA Km)?

A

The measure of affinity for transport of a transporters substrate

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11
Q

What are carrier mediated uniports?

A

Integral membrane proteins that transport a Single type of molecule across a cell membrane

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12
Q

How permeable are the membranes in the body?

A

Partially permeable

- certain molecules are able to pass through

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13
Q

What is an antiporter?

A

A co transporter integral membrane protein that transports 2 molecules in opposite directions

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14
Q

What does the GLUT2 transporter regulate in the pancreatic Β cells?

A

Regulates insulin levels

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15
Q

What is active membrane transport?

A

Transport requiring energy (ATP)

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16
Q

Why is blood glucose not taken up by the liver at low [glucose]?

A

Other organs require glucose at lower concentrations e.g. brain (always requires glucose)

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17
Q

Where is the GLUT4 transporter located in the body?

A

Muscle and fat cells

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18
Q

Describe the structural features of a glucose transporter

A
  • large molecule
  • amino terminus
  • carboxyl terminus
  • 12 transporter domains (can vary)
  • N linked glycosylation
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19
Q

What molecule does the GLUT5 transporter carry?

A

Fructose

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20
Q

What is passive transport?

A

All non mediated processes
small no. of molecules pass through pores
driven by concentration gradient

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21
Q

How can no. of GLUT4 receptors in muscles be increased?

A

Through endurance training, no. of GLUT4 receptors in the plasma membrane can increase

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22
Q

What does a low Kt mean for glucose transporters?

A

Glucose transporters are saturated at a low [glucose]

  • has a high affinity
  • active at low [glucose]
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23
Q

Which two glucose receptors are found in all mammalian tissues?

A

GLUT1 and GLUT3 involved in basal glucose uptake

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24
Q

What are the major functions of the various types of endoplasmic reticulum membranes?

A

RER
- Translation protein processing

SER
- Complex lipid synthesis

25
How do large uncharged polar molecules pass through the membrane?
e.g. Glucose | movement of these molecules depends on their concentration
26
What is the function of the nuclear membrane ?
Chromatin attachment
27
What Kt value do the brains glucose transporters have?
Low Kt values for glucose transporters in brain - high affinity Therefore brains energy needs always met
28
What type of transport is carried out by carrier mediated uniports?
Passive as still driven by concentration gradients
29
What is meant by a symporter?
Integral membrane protein involved in the co transport of molecules in the same direction
30
What is membrane function dependent on?
The membranes structure
31
What is a similarity between facilitative diffusion and active transport?
Both are selective and require integral membrane proteins
32
How is the concentration gradient of glucose maintained?
Glucose phosphorylated to G6P when it enters cell There are no G6P transporters in cells - G6P can't leave cell - [Glucose] always higher outside cell - eqb. never reached
33
Give an example of co transport in the body?
Glucose absorption by epithelial cells
34
Which transport process is required for continuous transport?
Both active and passive are required for continuous transport across cell membranes
35
Where is GLUT5 transporter found?
In the small intestine
36
What functions does the golgi membrane stacks carry out?
Post translational modifications occur on the Golgi membrane processing for secretions into the secretory pathway
37
How are ions able to move through the membrane?
By simple diffusion from a high to low concentration
38
What is foxglove digitalis?
Is a genus of herbacus (plant) used to produce transport inhibiting drugs Known as cardiotonic steroids
39
What is the function of the GLUT2 receptor in the liver?
Removes excess glucose from blood
40
Name the 5 different glucose transporters and their transport affinities (Kt)
``` GLUT1 - 1mM GLUT2 - 15-20mM GLUT3 - 1mM GLUT4 - 5mM GLUT5 - N/A ```
41
What is the major function of the liver?
Regulating blood glucose levels
42
What happens to excess blood glucose in the body?
Taken up by Liver
43
What is the role of Digitalis?
Specifically inhibits the Na+/K+ pump
44
Where are GLUT2 transporters found in the body?
Located in liver and pancreatic Β cells
45
Explain how the co transport of glucose and Na+ occurs in the epithelial cells in the gut.
1. High [Na+] outside epithelial cells 2. Na+ diffuse in to cell taking glucose in by co transport through SGLUT1 and SGLUT2 receptors - Glucose taken in against conc. gradient 3. Glucose passes into blood by facilitated diffusion 4. Na+ enters blood by active transport using ATP 5. Na+ exchanged for
46
Why is energy required for active transport?
Energy required as molecules are pumped against their concentration gradient [low} -> [high]
47
How are proteins targeted specifically to organelles?
Proteins have specific signal sequences targeting them to specific organelles
48
How does the Digitalis antiport system function to inhibit Na+/K+ pump?
Na+ is pumped out and Ca2+ is pumped in
49
Explain how re-hydration therapy works?
Targets co transport for glucose and sodium to treat diarrhoea
50
How can glucose uptake be increased?
Increasing number of glucose transporters | Increasing insulin
51
How is digitalis used to treat heart conditions?
Digitalis increases force of contraction of the heart - Na+/K+ pump inhibition leads to increased Na+ - slower Ca2+ removal by Na+/Ca2+ pump - increased contraction
52
What is the significance of compartmentalisation?
- Separates reactions - Enables regulation of local environments - Brings reactants together
53
What are the key features of glucose transport?
- carrier mediated - different tissues have different glucose transporters - transport depends on cell type
54
How is cystic fibrosis caused?
Mutation of CFTR gene causes faulty Cl- channel Build up of Cl- causes increase in water absorption in blood Mucus in airways becomes thicker
55
What is Digitalis used to treat?
Congestive Heart disease since 1780s
56
Explain how the glucose transporter is able to carry glucose across the membrane
1. Glucose binds to transporter 2. Conformational changes occur 3. Results in transport across membrane down concentration gradient 4. Bidirectional transport can occur 5. Gradient maintained by phosphorylation
57
How are plasma membranes able to respond to their environment?
They have receptors allowing interaction with the environment
58
How are lysosomal enzymes targeted differently?
"Not targeted by their amino acid sequence | Targeted by the Mannose-6-Phosphate pathway instead

FLC (34 decks)

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