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My Packs: UWO (BIO 2382) > (Damjanovski) Lecture 9 > Flashcards

(Damjanovski) Lecture 9 Flashcards

(49 cards)

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1
Q

What are the 4 properties of biomembranes?

A
  1. Fluid
  2. Closed compartments
  3. Semi-permeable
  4. Asymmetric
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2
Q

What procedure is used to measure membrane fluidity?

A

Fluorescence Recovery After Photobleaching (FRAP)

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3
Q

In FRAP:

If the membrane is very fluid, what will show up on FRAP?

A

Protein diffusion will be really fast
* Photobleached area will regain fluorescence in a short amount of time

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4
Q

In FRAP:

If the membrane is not very fluid, what will show up on FRAP?

A

Protein diffusion will be really slow
* Photobleached area will not regain fluorescence for a while/at all

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5
Q

What is considered extracellular?

A

Anything that is not in the cytoplasm

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6
Q

What does asymmetry of biomembranes imply?

A

The cytosolic face of the membrane will always be the cytosolic face

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7
Q

What can pass through the membrane freely?

A
  1. Small
  2. Uncharged
  3. Hydrophobic
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8
Q

What cannot pass through the biomembrane freely?

A
  1. Large
  2. Charged
  3. Hydrophilic
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9
Q

Carbohydrates are found…

A

On the exoplasmic face

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10
Q

What types of membrane proteins are there?

A
  1. Integral
  2. Lipid-linked
  3. Peripheral
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11
Q

True or False:

All proteins are asymmetric

A

True

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12
Q

What are the 3 domains of integral membrane proteins?

A
  1. Cytoplasmic - hydrophilic
  2. Transmembrane - hydrophobic
  3. Exoplasmic - hydrophilic
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13
Q

Cytoplasmic domain is often filled with charged amino acids such as…

A

Arginine and Lysine

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14
Q

What is the transmembrane domain usually like?

A

Hydrophobic amino acid chain (20-25 amino acids long)
* Alpha-helix and beta-barrel structure

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15
Q

What is a characteristic of the exoplasmic domain?

A

Almost always glycosylated

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16
Q

True or False:

Lipid-linked proteins go into the hydrophobic layer

A

False, the protein itself doesn’t go into the hydrophobic layer

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17
Q

How are lipid-linked proteins anchored to the membrane?

A

Via a lipophilic adduction

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18
Q

What are the types ways lipid-linked proteins are anchored?

A
  1. GPI anchor
  2. Acylation of Gly residue to lipid
  3. Prenylation of Cys residue to lipid
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19
Q

What does GPI stand for?

A

Glycosylphophatidylinositol

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20
Q

True or False:

GPI anchors are exoplasmic

21
Q

What do GPI anchors require to function?

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A

Sugar residues

22
Q

Are acylation of Gly and prenylation of Cys residues exoplasmic or cytoplasmic?

23
Q

What glycine is acylated to lipid on membrane?

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A

N terminal Glycine is acylated to membrane

24
Q

What cysteine is prenylated to membrane?

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A

C-terminal Cysteine is prenylated to membrane

25
Why do lipid-linked proteins diffuse ffaster than integral proteins?
The protein itself is not in the membrane in lipid-linked proteins
26
How are peripheral proteins attached to the membrane?
They are not, they are attached to integral or lipid-linked proteins via non-covalent interactions
27
What non-covalent interactions can peripheral proteins use to attached to other proteins?
* Ionic interactions * Hydrogen bonds * Protein-protein interactions * Van der Waals forces
28
What is the job of peripheral proteins?
Links proteins (integral or lipid-linked) to cytoskeletal components or ECM
29
What type of proteins are there based on insertion into membranes?
* Type I * Type II * Type III * Tail anchored proteins * GPI-anchored proteins * Type IV
30
What types of topogenic sequences are there?
* N-terminal (cleaved) signal sequence * Stop-transfer/membrane anchor sequence (STA) * Signal-anchor internal (uncleaved) sequence (SA) * Hydrophobic C-terminus
31
What is the topogenic sequence in tail anchored proteins?
Hydrophobic C-terminus tail
32
What is the membrane insertion of the tail anchored proteins done by?
1. Get3 recognizes hydrophobic tail 2. Brings TRANSLATED protein to the ER membrane to Get1 and Get2 3. ATP hydrolysis forces C terminus tail into the membrane
33
What are the cytosolic and exoplasmic domains in tail anchored proteins?
* Cytosolic - N terminal * Exoplasmic - NONE
34
What is the topogenic sequence in Type 1 proteins?
1. N terminal signal sequence 2. STA
35
What happens to Type 1 proteins once topogenic sequence is read?
The ribosome will bring the protein to the ER membrane * Ribosome will translate the protein through a translocon
36
What happens to the N terminal signal sequence?
Cleaved immediately as it enters through the translocon
37
What happens to Type 1 protein translation?
* Translates through translocon until STA sequence is reached * STA is forced into membrane * Remainder protein is translated
38
What are the cytoplasmic and exoplasmic domains in Type 1 proteins?
* Cytoplasmic - C terminal * Exoplasmic - N terminal
39
What are the topogenic sequences of GPI anchored proteins?
Technically a Type 1 Protein * N terminal signal sequence * C terminal STA sequence
40
What happens to GPI anchored proteins after C terminal STA sequence is forced into membrane?
GPA transamidase recognizes a sequence near the membrane and cleaves it * Transfers extracellular portion to an adjacent GPI
41
What are the cytoplasmic, transmembrane and exoplasmic domains of a GPI anchored protein?
* Cytoplasmic - NONE * Transmembrane - NONE * Exoplasmic - N terminal domain
42
What are the topogenic sequences in Type II/Type III proteins?
* SA sequence
43
What is the orientation of Type II/Type III proteins determined by?
Positively charged amino acids around the SA sequences
44
If the charged amino acids are on the N terminal side...
* Cytoplasmic - N terminal * Exoplasmic - C terminal Type II
45
If the charged amino acids are on the C terminal side...
* Cytoplasmic - C terminal * Exoplasmic - N terminal Type III
46
What are the topogenic sequences in Type IV proteins?
1. SA sequences 2. STA sequences
47
Do type IV proteins have an even or odd number of transmembrane domains?
Even or odd
48
What is the pattern for SA/STA domains for Type IVa proteins?
SA, STA, SA, STA... * Starting in cytosol
49
What is the pattern for SA/STA domains for Type IVb proteins?
SA, SA, STA, SA, STA, SA... * Starting extracellular

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