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DYS: Biology > Membrane proteins > Flashcards

Membrane proteins Flashcards

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1
Q

Types of membrane proteins

A

Transmembrane (integral membrane) protein
Cytoplasmic (lipid-anchored) proteins
Accessory membrane proteins

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2
Q

Structure of Transmembrane protein

A

Alpha helices which contain amino acids with hydrophobic side chains (which would form a hydrophobic surface +interact with lipid bilayer)

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3
Q

GPCRs

A
  • Integral membrane proteins
  • 7 transmembrane alpha helices
  • Helices are connected by loops in extracellular/cytosolic parts
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4
Q

What connects helices 5 + 6?

A

Cytosolic loop 3 - which interacts with G-proteins

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5
Q

Examples of GPCR

A

M3 muscarinic, H2 histamine, CCK2 receptor

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6
Q

How many GPCRs does the human genome encode?

A

More than 800

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7
Q

What do GPCRs represent?

A

The largest class of molecular drug targets

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8
Q

Function of GPCR

A 
Drug targets
Olfactory receptors (450 - 500 GPCRs) to detect odour
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9
Q

What do GPCRs bind to and what happens?

A

Bind to ligand in cell exterior + induce conformational change (in cytoplasmic face of receptor) to enable binding to G protein

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10
Q

Causes inactive GPCR

A

Antagonist

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11
Q

Causes active GPCR

A

Agonist

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12
Q

Lipid - anchored proteins

A

Cytoplasmic proteins attach to plasma membrane by lipid anchor

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13
Q

3 types of lipid modifications

A

N-myristoylation
S-palmitoylation
S-prenylation

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14
Q

N-myristoylation

A

Linked using Amide bond
C14 myristic fatty acid binds to N-terminus
Irreversible
Galpha protein

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15
Q

S-prenylation

A

Thioether bond to link lipid to cysteine
Near C-terminus
Irreversible
Gy protein

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16
Q

S-palmitoylation

A

Thioester bond links lipid to cysteine side chains
Near N-terminus
Reversible
Galpha protein

17
Q

Types of Ion channel

A

Voltage-gated

Ligand-gated

18
Q

What controls voltage-gated?

A

Changes in membrane

19
Q

What activates Ligand-gated?

A

Binding of a ligand

20
Q

Speed of Ion channels

A

Fast - 10^7 - 10^8 ions per second

21
Q

Types of solute transporter

A

Uniporter
Antiporter
Symporter

22
Q

Uniporter

A

Transport single type of solute by passive transport

23
Q

What direction do uniporters move solute?

A

Down electrochemical gradient

24
Q

Speed of Uniporters

A

Slow - 10^2 - 10^4 molecules

25
Q

Antiporter

A

Movement of 2 solutes in the opposite directions

Need active transport

26
Q

Symporter

A

Movement of 2 solutes in the same direction

Involved in uptake of glucose by epithelial cells in intestine

27
Q

Human disease affected by SLC6A2

A

Thyroid hormone transporter, Psychomotor retardation

28
Q

Human disease affecting SLC12A1 + SLC12A3

A

Bartter syndrome, Gitelman syndrome, Kidney disorder

29
Q

Human disease affecting SLC12A6

A

Andermann syndrome, Motor + sensory neuropathy

30
Q

Types of ATP-dependent transport

A

ATP-dependent ion pumps
ABC transporters
Both transport against gradient

31
Q

What provides energy for ATP-dependent transport?

A

ATP hydrolysis

32
Q

Speed of ATP-dependent transport

A

Slow - 10^0 - 10^3

33
Q

Examples that use ATP Transporters

A

Cystic fibrosis
- Mutation in CFTR gene encoding chloride transport
Sitosterolaemia
- Mutations in the ABCG5 or ABCG8 genes (sterol + cholesterol transport)
Drug resistance/drug interactions
- MDR1

34
Q

2 ways in classifying membrane proteins

A

Architectural - transmembrane, lipid-anchored, accessory

Functional - receptors (signalling), transmembrane transport, attachment (migration)

35
Q

What can’t cross lipid bilayer

A

Water

36
Q

Example of antiporter

A

Basolateral membrane uses HCO3- to facilitate Cl- ions

DYS: Biology (4 decks)

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