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MSI Unit I > 1-22 Membranes and Microscopy > Flashcards

1-22 Membranes and Microscopy Flashcards

1
Q

5 Functions of biological membranes

A
  1. permeability layer
  2. compartmentalization of functions
  3. identification
  4. signaling
  5. energy storage
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2
Q

describe the permeability barrier function of biological membranes

A

controls what gets in and what gets out

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3
Q

describe the compartmentalization function biological of membra nes

A

allows functional compartmentalization

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4
Q

describe the identification function of biological membranes

A

proteins/lips/carbs that occur on surface of cell to identify different cells. (ex. A and b antigens of AB blood type)

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5
Q

describe the signaling function of membranes

A

receptors tell the inside of the cell what the conditions are on the outside

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6
Q

describe the energy storage function of biological membranes

A

any time you create a gradient across a membrane, can be used as a source of energy. Gradients are used to drive molecule transport, drive oxydative phosphorylation in mitochondria.

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7
Q

Common chemical features of membrane lipids

A

The membrane lipids are amphipathic molecules. Besides cholesterol, they have a three-carbon backbone with at least one fatty acid tail attached.

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8
Q

phospholipids

examples?

hydrophilic parts?
hydrophobic parts?

A

membrane lipid with phosphate.

includes phosphoglycerides (hydrophobic fatty acid chains, hydrophilic phosphorylated alcohol)

and sphingomyelin (hydrophobic fatty acid chains, hydrophilic phosphoryl choline)

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9
Q

glycolipids

example of?

describe.

hydrophobic parts? hydrophilic parts?

A

example of sphingolipid

sphingosine backbone with sugar (unlike phospholipids, not phosphate) attatched via ester bond.

hydrophobic parts - fatty acid chains, sphingosine hydrocarbon chain

sugar - hydrophilic

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10
Q

cholesterol

structure?

hydrophobic parts? hydrophilic?

A

build on a four ring steroid structure with a hydrophobic head group.

Ring structure and hydrocarbon are hydrophobic

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11
Q

the membrane proteins. do what?

A
  • allow selective permeability
  • carry out most of the specialized and specific cell functions of the membranes
  • diffuse laterally (unless constrained) but don’t flip flop
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12
Q

most membranes have more ____ than _____

A

protein, lipid

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13
Q

peripheral membrane proteins

A

bound to membrane surface or to an integral protein.

released without disrupting bilayer

amphipathic molecules - hydrophobic regions interact with inner lipid part of membrane. hydrophobic regions interact with the head groups and aqueous environment.

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14
Q

integral membrane proteins

A

penetrate the lipid bilayer

require detergents to be released (must disrupt bilayer)

have a defined topography (orientation) that will not change since it was inserted into the membrane

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15
Q

how do lipids effect the physical characteristics of membranes?

interactions? 
kinks?
cholesterol content?
temperature?
transport?
A

hydrophobic interactions by tails dictate the shape.

kinks in fatty acid chains decrease interactions/packing and increase fluidity

cholesterol incorporation causes a net decrease in membrane fluidity

higher temperatures causes lipids to pack loosely

membrane allows for passive trasnport of small, nonpolar substances. Larger substances cannot pass through the tight packing of fatty acid tails and polar substances cannot pass through the hydrophobic tail region

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16
Q

How do proteins effect the physcial characteristics of membranes?

A

Allow the membrane to be selectively permeable by carrying out facilitated diffusion. In general, proteins give specialized membranes their specialized characteristics

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17
Q

what are the sources of variation between biological membranes?

A

all membranes made of same basic molecules

relative composition and kinds of proteins present allow for differences

membranes with different degrees of unsat, various amounts of cholesterol, different types of membrane proteins will have different physical and biochemical properties.

18
Q

The two halves of the bilayer must be

A

assymetrical

19
Q

lipid rafts

purpose?

A

1) Higher content of sphingo lipisd - glycolipids, sphingomyelin
2) Longer fatty acid chains

3) Lots of cholesterol
4) Packed tightly, move as raft

purpose - gathering areas for subsets of protein

20
Q

common chemical features of membrane lipids

A

amphipathic molecules.

Besides cholesterol, they have a three-carbon backbone with at least one fatty acid tail attached.

21
Q

phosphoglyceride

A 
fatty acid chain (hydrophobic)
phosphorylated choline (hydrophilic)
22
Q

sphingomyelin

A

fatty acid chain & hydrocarbon chain of sphingosine (phobic)

phosphoryl choline (philic)

23
Q

glycolipid

A

fatty acid cahin and hydrocarbon chain of sphingosine

one or more sugars (philic)

24
Q

cholesterol

A

hydrophobic part (entire molecule but OH group)

philic part - the OH group.

25
Q

draw general structure of phosphoglycerides, sphingomyelin, and glycolipid

A

page 274

26
Q

formation of lipid bilayers in aqueous solution is a

A

spontaneous process

driven by hydrophobic effect, van der waals forces, and electrostatic/h-bond interactions between polar head groups and water

27
Q

lipid bilayers are ______

describe the compositions

A

outer half - phosphatidylcholine, sphingomyelin, glycolipids

inner half - phosphatidylserine and ethanolamine

cholesterol distributed evenly between 2 halves

28
Q

lipid bilayers are permable to

A

small uncharged polar molecules

hydrophobic molecules

29
Q

lipid bilayers are not permeable to

A

large uncharged polar molecules

ions

30
Q

scramblases

A

move random phospholipids from one half of bilayer to another, redistributing phospholipids evenly between the two halves of the lipid bilayer

31
Q

flippases

A

located on golgi and PM, move specific phospholipids from one side to another to create asymmetry

32
Q

in aqueous solution at pH 7, a lipid bilayer will be most permeable to which of the following molecules:

Na+ ion, Cl- ions, water, glucose, valine

A

water

33
Q

what determines if Na+ ions can cross a biological membrane?

A

the presence of INTERGRAL membrane proteins about to act as Na+ transporters.

34
Q

Summarize the factors affecting membrane fluidity (temp, concentration of unsaturated lipids, length of fatty acid chains, cholesterol content)

A 
Increasing fluidity:
Higher temp
more unsaturated lipids
Shorter fatty acid chains
lower cholesterol content
35
Q

Which types of proteins are bound to surface of membrane and can be release without disrupting lipid bilayer

A

Peripheral membrane proteins

36
Q

Which types of proteins penetrate lipid bilayer and require detergents to release them from membrane bilayer. They transverse the entire lipid bilayer

A

Integral membrane proteins

37
Q

Where are membrane lipids synthesized?

A

ER

38
Q

How to newly synthesized lipids insert themselves into bilayer?

A

Newly synthesized phospholipids insert themselves exclusively into the cytosolic half of the bilayer

39
Q

What is a difference between the function of scramblase and flippase?

A

Scramblase flips lipids in the membrane to prevent asymmetry while flippase creates asymmetry that is needed for certain functions

40
Q

Which of the following forces is LEAST important in driving formation of a lipid bilayer in aqueous solution?

A. The hydrophobic effect (removal of the hydrophobic lipid tails from water)

B. van der Waals interactions between the hydrophobic tails of the lipids

C. Electrostatic interactions between phosphate groups in the polar head groups of neighboring lipid molecules

D.Hydrogen bonding interactions between the polar head groups of the lipids and surrounding water molecules

A

Electrostatic interactions (repulsion) between the phosphates can actually oppose bilayer formation; all of the other forces help drive formation.

41
Q

In aqueous solution at pH 7, a lipid bilayer will be MOST permeable to which of the following molecules:

A. Na+ ions

B. Cl- ions

C. water

D. glucose

E. valine as a free amino acid

A

Water

MSI Unit I (52 decks)

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