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BMSC 200 > Chapter 9 + Quiz Questions > Flashcards

Chapter 9 + Quiz Questions Flashcards

1
Q

What are the 6 membrane functions?

A

1) Separate cells from the external medium to create an intracellular environment of unique and defined composition.
2) Allow selective transport of substrates in and out of the cell.
3) Provide a location for specialized pathways and processes
4) Rapid changes in electric potential across the membranes of
neurons as basis of the nervous system.
5) Localization of receptors to facilitate response to physiological signals.
6) Mediate cell-cell recognition and interaction

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2
Q

What are 8 membrane characteristics?

A

1) Membranes are sheet-like structures, two molecules thick, that form closed boundaries between compartments.
2) Membranes consist of mainly of lipids and proteins, with
carbohydrates linked to these molecules.
3) Membranes are built from amphipathic molecules.
4) Membranes are largely impermeable to polar molecules.
5) Specific membrane proteins mediate particular biological
functions.
6) Membranes are self-assembling, non-covalent structures.
7) Membranes are fluid and dynamic structures.
8) Membranes are highly specialized in their composition and
distribution (asymmetric)

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3
Q

Membrane formation is a consequence of the ..?

A

Amphipathic nature of the membrane lipids

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4
Q

These molecules in self-assemble through the ____ _____

A

hydrophobic effect

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5
Q

The structure formed depends on the ____ of cross-sectional areas of the polar head group and the hydrophobic tail

A

ratio

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6
Q

Fatty acids favor formation of ______; lipids with two hydrocarbon tails tend to form _____

A

micelles, bilayers

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7
Q

Exposure of hydrophobic tails at the edge of the bilayer to water is energetically _______

A

unfavorable

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8
Q

Flat bilayer sheets are unstable and spontaneously form membrane _____. These are the basis of cells and organelles

A

vesicles

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9
Q

Lipid bilayer membranes have a very low ______ to ions and most polar molecules

A

permeability

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10
Q

Permeability of small molecules is correlated with their relative ____

A

solubility in water

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11
Q

Some small ___-____ gases and small ____ molecules can pass directly through the membrane

A

non-polar, hydrophobic

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12
Q

The cell membrane can represent a critical barrier for polar drugs intended for ______ targets

A

intracellular

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13
Q

Encapsulation of a drug within a liposome can facilitate ____ across the membrane

A

transport

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14
Q

Liposomes can also be used to target ____ cells or organelles

A

specific

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15
Q

Membranes are primarily composed of __ and ____

A

lipids, proteins

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16
Q

More active membranes have a higher ratio of ____ to ____

A

protein, lipid

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17
Q

Composition of membrane components can be _____, in
particular for prokaryotes

A

dynamic

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18
Q

Membranes are dynamic structures due to the nature of the ___-_____ interactions

A

non-covalent

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19
Q

Lipids and proteins freely ____ in the plane of the membrane

A

diffuse

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20
Q

Lateral movement of proteins and lipids within the membrane is very _____

A

rapid

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21
Q

Movements across the membrane is _____

A

restricted

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22
Q

Transbilayer movement requires a ____ head group to pass through hydrophobic environment

A

polar

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23
Q

Uncatalyzed rate of lipid molecule crossing from one sheet to the other (flip-flop diffusion) is very ___

A

slow

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24
Q

What are flippases?

A

Translocation of lipids from one side of bilayer to the other is catalyzed by enzymes

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25
Q

Lipid composition of the inner and outer sheets of the bilayer can be different, allowing for ______ of
the membrane faces

A

specialization

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26
Q

Cells need to maintain an appropriate levels of
_____ _____

A

membrane fluidity

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27
Q

Membranes undergo _____-dependent
phase transitions

A

temperature

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28
Q

Membranes undergo temperature-dependent
phase transitions. What happens to the membrane when the temperature is below, above, or at the phase transition temperature?

A

Below: membrane is too solid
Above: membrane is too fluid
At the: the hydrocarbon chains are partially ordered but lateral diffusion is still possible

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29
Q

Animals use _____ to mediate membrane
fluidity

A

cholesterol

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30
Q

While the basic features of the bilayer are simple and consistent, there are mechanisms to enable specialization: what are 3 of them?

A
  1. Composition of Membrane Components
  2. Distribution of Membrane Components
  3. Specialized Membrane Regions
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31
Q

In the mechanisms that enable specialization, what entails Composition of Membrane Components?

A

Lipids and Proteins

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32
Q

In the mechanisms that enable specialization, what entails Distribution of Membrane Components?

A

Static and Dynamic

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33
Q

In the mechanisms that enable specialization, what entails Specialized Membrane Regions?

A

Lipid Rafts

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34
Q

The lipid composition of membranes ____ across species and cell types

A

varies

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35
Q

____ ____ arise from the spontaneous association of lipid molecules whose hydrocarbon tails are of similar length

A

Lipid rafts

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36
Q

The longer, saturated hydrocarbons of sphingolipids form stable associations making the lipid rafts ___ and more ____ than the rest of the membrane

A

thicker, ordered

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37
Q

____ are docking points in lipid-anchored proteins that contain long-chain saturated fatty acid anchors

A

Rafts

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38
Q

The lipid-linked proteins that associate with rafts often serve ____ functions

A

signaling

39
Q

Three categories of membrane proteins are defined based on different mechanisms of association with the membrane:

A

1) Peripheral
2) Lipid-anchored
3) Integral membrane

40
Q

What kind of membrane proteins associate with the membrane through electrostatic or hydrogen-bonding
interactions?

A

Peripheral

41
Q

What kind of membrane proteins can dock to either membrane lipids or integral membrane proteins?

A

Peripheral

42
Q

The bulk of the ____ membrane proteins is in the cytosol or extracellular space

A

peripheral

43
Q

Changes in pH or ionic strength often releases these proteins from the membrane..?

A

Peripheral

44
Q

Covalently attached ___ can anchor proteins to the membrane

A

lipids

45
Q

Protein modifications are sometimes ______, allowing for regulation of cellular location

A

reversible

46
Q

Proteins with ____ chain hydrocarbons always are on the inner face

A

single

47
Q

_____ membrane proteins are immersed in, and usually span, the membrane

A

Integral

48
Q

In what kind of membrane proteins are the positioning within a membrane specific and directional?

A

Integral

49
Q

Integral membrane proteins tend to be of three varieties:

A

1) Single pass α-helical
2) α-helical bundles
3) β-barrels

50
Q

In the integral membrane proteins, charged residues are located mostly within the ____ and ______ portions of the protein

A

intra, extracellular

51
Q

Residues with non-polar side chains dominate ____ the hydrophobic slab of the bilayer

A

inside

52
Q

Membrane spanning regions can be predicted from the..?

A

amino acid sequence

53
Q

Stretches of ___ hydrophobic residues in a row are likely membrane spanning

A

~20

54
Q

A hydropathy index looks at the _____ characteristics of a protein to predict transmembrane regions

A

hydrophobic

55
Q

Side chains within the transmembrane region tend to be
___-_____, however the carbonyl and amide groups of each peptide bond are ____

A

non-polar, polar

56
Q

Polar unpaired carbonyl and amide groups in the bilayer core are energetically _______

A

unfavorable

57
Q

______ and ____ groups of the protein backbone within the bilayer have to be hydrogen-bonded

A

Carbonyl, amide

58
Q

What are the four Categories of Membrane
Transport?

A

1) Simple Diffusion
2) Facilitated Diffusion (carriers, channels)
3) Active Transport (primary, secondary)
4)Ion Transporters

59
Q

Their direction and rate of movement is determined by their concentrations on either side of the membrane. What Kind of transport is this?

A

Simple Diffusion

60
Q

____ can only result in the net movement down a concentration gradient

A

Diffusion

61
Q

Membrane transporters lower the activation energy barrier of crossing the bilayer in what kind of transport?

A

Facilitated Diffusion

62
Q

The activation energy for removing the hydration shell from a polar solute and transferring it into the non-polar
environment in the core of the bilayer is very ____

A

high

63
Q

Membrane transporters _____ the activation energy for crossing the membrane by replacing the hydration shell with interactions with polar groups along the transfer
path in the protein interior

A

lower

64
Q

Does the following occur in Channels or Carriers: Membrane pores transport molecules down concentration gradient

A

Channels

65
Q

Does the following occur in Channels or Carriers: high conductance rates because they bind the substrate very weakly

A

Channels

66
Q

Does the following occur in Channels or Carriers: no saturation?

A

Channels

67
Q

Does the following occur in Channels or Carriers: membrane proteins that undergo substrate-induced conformational change, or membrane repositioning, to release substrate to the other side of the membrane

A

Carriers

68
Q

Does the following occur in Channels or Carriers: slower because they bind the substrate quite strongly

A

Carriers

69
Q

Does the following occur in Channels or Carriers: saturation

A

carriers

70
Q

What is uniport?

A

Transport of a single molecule

71
Q

What is the difference between antiporters and symporters?

A

Antiporters move molecules in different directions.
Symporters move molecules in the same direction

72
Q

In diffusion, co-transport through antiport or symport depends on the..?

A

Charge of the molecules in order to have a net neutral change

73
Q

In secondary active co-transport, system couples a molecule moving down its gradient to..?

A

one moving down its gradient

74
Q

What is active transport?

A

The input of energy that allows movement of molecules
against concentration gradients

75
Q

What is primary active transport, and what does it include?

A

It is driven by direct source of energy (ATP) and includes P-type, V-type, and ABC Transporters

76
Q

What is secondary active transport?

A

Couples the movement of one molecule down its concentration gradient within the movement of another molecule down its gradient

77
Q

What is P-Type ATPase? (x4)

A

1) Cells maintain high gradients of Na+ outside the cell and K+ inside the cell
2) The gradient control cell volume, electrical excitability, and enables uptake of nutrients through secondary active transport
3) Na+, K+ ATPase uses the energy of ATP hydrolysis to pump three Na+ out of the cell and two K+ into the cell
4) Undergoes a phosphorylated intermediate

78
Q

What is the V-Type ATPase? (x2)

A

1) Use the energy of ATP to move protons against a concentration gradient
2) Acidification of organelles

79
Q

What are ABC transports? (x3)

A

1) Contain ATP-binding domains (ATP-Binding
Cassette)
2) Transport of a variety of biomolecules out of
the cell against a concentration gradient
3) Multi-drug resistance protein pumps drugs out of the cell rendering the drugs ineffective

80
Q

What is secondary active transport?

A

1) The movement of glucose up its concentration gradient is enabled by the movement of Na+ ions down their concentration.
2) Active transport of glucose depends on the action of the Na+-K+ ATPase to establish the gradient of Na+ ions

81
Q

___ channels enable rapid movement of ions across the
membrane

A

Ion

82
Q

Actions of ion channels can cause changes in _____ _____ in neurons.

A

membrane potential (action potentials)

83
Q

Ion channels are tightly _____; voltage-gated channels
and ligand-gated channels

A

regulated

84
Q

Ion channels differ from ion transporters (like the N+,K+
ATPase) in three ways:

A

1) Faster
2) No saturation limits
3) Gated/Regulated

85
Q

Ion channels are highly ______ for the molecule to be
transported

A

selective

86
Q

Selectivity filter discriminates K+ and Na+ based on their ability to shed ____ _______ to form electrostatic
interactions within backbone carbonyls

A

water molecules

87
Q

As K+ ions enter the filter, the electrostatic repulsion from other incoming K+ ions helps to push the flow of ions from ____ to ____the cell

A

inside, outside

88
Q

Which type of transporter is involved in establishing and maintaining membrane potential?

A

P-type ATPases

89
Q

The fluid mosaic model refers to..?

A

the freedom of movement of membrane proteins and lipids within the plane of the membrane

90
Q

Which is an example of symport?

A

Glucose uptake into intestinal epithelial cells

91
Q

Molecule X is transported into the cell in a manner that requires a specific protein, at a rate that depends on the extracellular concentration of X, and with an upper limit to the rate of transport. What type of transport system is likely responsible for transport of X?

A

Diffusion through a carrier

92
Q

Uptake of glucose into intestinal epithelial cells is an example of..?

A

Secondary active transport

93
Q

The movement of non-polar gases across a membrane reflects..?

A

Simple diffusion

BMSC 200 (11 decks)

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