Lecture 2 - Membrane Proteins Flashcards

1
Q

Are proteins dynamic or static structures?

A

Dynamic

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2
Q

What does the structure of a membrane protein structure depend on?

A

Its function

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3
Q

If a protein was to change conformation, what would it require?

A

A specific biological signal

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4
Q

Do all living cells have membrane potentials?

A

YES

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5
Q

What is the importance of water in functioning proteins?

A

They need to be optimally hydrated to obtain their specific 3D structure

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6
Q

How does water interact with protein?

A

Dynamically constantly moving around forming hydrogen bonds

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7
Q

Fact to know:

A

Proteins are flexible and elastic, this is a key structural feature that enables function

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8
Q

What are the 3 modes of movement proteins in the membrane can do?

A

Lateral motion
Rotational motion
CONFORMATIONAL CHANGE

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9
Q

How are membrane proteins classified?

A

Based on their location/structural association with the membrane

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10
Q

What are the 2 groups of membrane proteins?

A

Peripheral proteins
Integral proteins

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11
Q

Where can peripheral proteins be located on the membrane?

A

External Membrane Face
Internal Membrane Face

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12
Q

How do peripheral proteins adhere to the membrane?

A

Via loose interactions/associations (non covalent) with INTEGRAL PROTEINS/LIPID head groups

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13
Q

What is the importance of Intracellular peripheral proteins and the Cortical cytoskeleton?

A

Provides flexibility and elasticity to membrane
Disperses forces throughout network protecting cell integrity

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14
Q

What is the function of extracellular peripheral proteins?

A

Enzymes
Antigens
Adhesive molecules with ECM

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15
Q

What are integral membrane proteins?

A

Proteins that have varying degrees of penetration of the lipid bilayer

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16
Q

How is the degree of penetration of integral membrane proteins determined?

A

The non polar and polar bond formed
Non polar (hydrophobic tails of bilayer)
Polar head groups and peripheral proteins interact with the polar residues of the peptide chains

17
Q

What are lipid anchored proteins?

A

Type of integral protein where there’s a covalent link between the fatty acid group within the bilayer

18
Q

Where is the functional protein located in a lipid anchored protein?

A

Outside the membrane

Able to move laterally

19
Q

How are membrane proteins organised?

A

Very specifically and precisely in order to function correctly

20
Q

What determines the positioning of membrane proteins?

A

The status of the near field electrical environment

21
Q

What are the 3 ways that membrane proteins organise/interact?

A

Aggregation
Tethering (Extracellular and Intracellular)
Cell-cell interaction

22
Q

Give 2 examples of aggregates:

A

Mitochondria (ET chain)
Lipid Rafts (Antigen presentation)

23
Q

Give an example of External tethering::

A

Integral membrane proteins connect with ECM

24
Q

What is internal tethering?

A

When membrane proteins connect with the cytoskeleton providing structure all strength and whole cell flexibility/elasticity

25
Q

What is an example of a cell-cell interaction

A

Cadherins

26
Q

What is the benefit of cadherins when forces are experienced?

A

They allow forces to be transmitted and dissipated through the tissue

27
Q

What are the 3 mains structural components of the cortical cytoskeleton of the RBC plasma membrane?

A

Transmembrane proteins
Intermediate Anchoring Proteins connecting (1 & 3)
Long flexible/elastic force carrying proteins

28
Q

What are the key transmembrane proteins in RBCs?

A

HCO3- / Cl- antiporter also called band 3.1 (TRANSPORTS CO2)

Glycophorin

29
Q

What are the additional roles of Band 3.1 and Glycophorin?

A

Shaping RBC bioconcave architecture
Allow forces to be distributed throughout the whole structure

30
Q

What does ankyrin do?

A

Binds spectrin to band 3.1 (HCO-3/Cl- Exchanger)

Links band 3.1 to cytoskeleton

Spectrin = cytoskeleton of RBC

31
Q

What does Band 4.1, Adducin and Actin do?

A

Anchors Glycophorin

32
Q

What is another name for spectrin?

A

Cytoskeleton

33
Q

What is the function of spectrin?

A

It forms massive hexagonal lattice throughout whole RBC

34
Q

What is the function of the cortical cytoskeleton?

A

Provides flexibility and elasticity for whole cell

Keeps membrane proteins in place

35
Q

What would happen if the cytoskeleton proteins of RBCs were mutated?

A

Loss of RBC structural integrity

36
Q

What is a common condition where the cytoskeleton proteins of red blood cells are affected?

A

Hereditary Spherocytosis