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BMSC > Module 9 - 2 > Flashcards

Module 9 - 2 Flashcards

1
Q

What are membranes primarily composed of?

A

Lipids and proteins.

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2
Q

What is the role of proteins in membranes?

A

Reception and other active roles.

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3
Q

What is the relationship between membrane activity and protein to lipid ratio?

A

More active membranes have a higher ratio of protein to lipid.

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4
Q

Can the composition of membrane components be dynamic?

A

Yes, particularly for prokaryotes.

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5
Q

What is the fluid mosaic model of membrane structure?

A

a model describing biological membranes as a fluid bilayer with embedded proteins; The bilayer exhibits both structural and functional asymmetry

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6
Q

What causes membranes to be dynamic

A

the nature of the non-covalent interactions

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7
Q

Is lateral movement of proteins and lipids within the membrane slow or rapid?

A

Rapid.

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8
Q

Is movement across the membrane restricted or unrestricted?

A

restricted

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9
Q

What is transbilayer movement require?

A

A polar head group to pass through the hydrophobic environment

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10
Q

Is the uncatalyzed rate of lipid molecule crossing from one sheet to the other fast or slow?

A

Very slow.

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11
Q

What are flippases?

A

Enzymes that catalyze translocation of lipids from one side of bilayer to the other.

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12
Q

Can the lipid composition of the inner and outer sheets of the bilayer be different? What does this allow for?

A

Yes. It allows for specialization of the membrane faces

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13
Q

Why do cells need to maintain appropriate levels of membrane fluidity?

A

To ensure proper function.

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14
Q

Do membranes undergo temperature-dependent phase transitions?

A

Yes

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15
Q

What happens to the membrane below the phase transition temperature?

A

It becomes too solid.

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16
Q

What happens to the membrane above the phase transition temperature?

A

It becomes too fluid.

17
Q

What happens to the membrane at the phase transition temperature?

A

The hydrocarbon chains are partially ordered but lateral diffusion is still possible. (Just right)

18
Q

How do cells adjust membrane composition to maintain liquid-ordered state?

A

Bacteria vary the length and saturation of the hydrocarbon tails of membrane lipids; animals use cholesterol to mediate membrane fluidity

19
Q

Can temperature cause changes to membrane composition?

A

Yes.

20
Q

Can membrane structure and function be specialized?

A

Yes.

21
Q

What are the mechanisms to enable specialization in the bilayer?

A

Composition and distribution of membrane components and specialized membrane regions

22
Q

What are the components of the membrane?

A

lipid and protiens

23
Q

How are membrane components distributed?

A

Static and dynamic

24
Q

What are lipid rafts?

A

Plasma membrane microdomains, rich in cholesterol and sphingolipids, which provide a particularly ordered environment

25
Q

What is the composition of lipid rafts?

A

Sphingolipids with longer tails that exclude glycerophospholipids

26
Q

What is the function of lipid rafts?

A

Docking points for lipid-anchored proteins that contain long chain saturated fatty acid anchors and the lipid linked proteins that associated with rafts often serve signaling functions

27
Q

What are the three categories of membrane proteins?

A

Peripheral (c and d), lipid-anchored (e), and integral membrane proteins (a and b)

28
Q

What are the active roles of membrane proteins?

A

Receptors and transporters

29
Q

How do peripheral membrane proteins associate with the membrane?

A

Through electrostatic or hydrogen-bonding interactions

30
Q

Where are the bulk of peripheral membrane proteins located?

A

In the cytosol or extracellular space

31
Q

What releases peripheral membrane proteins from the membrane?

A

Changes in pH or ionic strength

32
Q

What are lipid-linked proteins?

A

Proteins that associate with rafts and contain long-chain saturated fatty acid anchors

33
Q

What are the specialized compositions and functions of membranes?

A

Varies across species and cell types

34
Q

What are the dynamic changes to membrane composition and/or positioning used for?

A

To regulate biological events

35
Q

What is an example of dynamic changes to membrane composition?

A

Movement of phosphatidylserine to outer leaf functions in initiating cell destruction (apoptosis)

36
Q

What are the hydrocarbon tails of sphingolipids like?

A

Longer and saturated

37
Q

What makes lipid rafts thicker and more ordered than the rest of the membrane?

A

The stable associations formed by the longer, saturated hydrocarbons of sphingolipids

38
Q

Lipid rafts arise from what original

A

These spontaneous association of lipid molecules whose hydrocarbon tails are of similar length

BMSC (19 decks)

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