Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MCB 3010 > EXAM 3 > Flashcards

EXAM 3 Flashcards

1
Q

functions of membranes

A

boundaries of cell

allows import and export

retains metabolites and ions

senses external signals and transmits info into the cell

provides compartmentalization within eukaryotic cells

stores energy as a proton gradient

supports synthesis of ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

functions of membranes: import and export

A

selective import of nutrients and selective export of wastes and toxins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

functions of membranes: compartmentalization

A

separate energy-producing reactions from energy consuming ones

keeps proteolytic enzymes away from important cellular proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

membranes are composed of

A

variety of lipids and proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

some membrane lipids and proteins are

A

glycosylated

esp outer face of plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

membrane bilayer

A

2 leaflets of lipid monolayers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

membrane bilayer is made up mostly of

A

glycerophospholipids (+sphingolipids and others)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

membrane bilayer spontaneously forms due to

A

hydrophobic effect

hydrophilic head groups interact w water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

glycerophospholipids

A

two fatty acids on C1 and C2 of glycerol

highly polar PO4 on C3 may be further esterified by an alcohol (head groups)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

sphingolipids

A

one fatty acid attached to sphingosine by amide linkage

head group may also be attached to sphingosine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

fluid mosaic model of membranes

A

singer and nicholson

lipids form a viscous, 2D solvent into which proteins are inserted and integrated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

two types of proteins in fluid mosaic model

A

integral and peripheral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

integral proteins

A

firmly associated with the membrane, often spanning the bilayer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

peripheral proteins

A

weakly associated to the surface of the bilayer via lipids or integral proteins and can be removed easily

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

physical properties of membranes

A

dynamic and flexible

asymmetric

can undergo phase transitions

not permeable to larger polar solutes and ions

permeable to small polar solutes and nonpolar compounds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

composition of membranes: lipids

A

ratio of lipid to protein varies

type of phospholipid varies

abundance and type of sterols varries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

prokaryotes lack ______ in membranes

A

sterols

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

cholesterol is found higher in ________ and absent in ______

A

higher in plasma membrane and absent in mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

asymmetry of membranes: lipids

A

outer and inner leaflets have different compositions

head groups on inner leaflet are smaller for smaller radius

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

asymmetry of membranes: proteins

A

individual peripheral membrane proteins are only associated w one side of the membrane

integral proteins have different domains on different sides of the membrane

specific lipid anchors added to proteins target the protein to a specific leaflet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

asymmetry of membranes: carbs

A

only on outside of plasma cell membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

asymmetry of membranes: electric

A

inside is usually -50

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

membrane phases

A

depending on their composition and the temperature, the lipid bilayer can be in the gel or fluid phase

gel
fluid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

gel phase

A

liquid ordered state

individual molecules do not move around

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

fluid phase

A

liquid disordered state

individual molecules can move around

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

membrane phases temperature

A

heating: gel to fluid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

membrane under physiological conditions

A

membranes are more fluid like than gel like

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

adjusting membrane composition

A

fluidity is determined mainly by the fatty acid composition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

shorter and more unsaturated fatty acids:

A

more fluid membranes

less interactions bc short

more kinks so less packing, lower Tm, more fluidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

high temperature membrane

A

more saturated fatty acids to maintain integrity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

low temperature membrane

A

more unsaturated fatty acids to maintain fluidity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

sterols in membranes

A

cholesterol: animals
phytosterols: plants
ergosterol: fungi

affect membrane rigidity and permeability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

functions of proteins in membranes

A

receptors
enzymes
channels, gates, pumps

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

functions of proteins in membranes: receptors

A

detect signals from the outside

light (opsin)
hormones (insulin receptor)
NT (Ach receptor)
pheremones (taste and smell receptors)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

functions of proteins in membranes: enzymes

A

lipid biosynthesis (acyltransferases)

ATP synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

functions of proteins in membranes: channels, gates, pumps

A

nutrients (maltoporin)
ions (K+ channel)
NT (SSRI)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

peripheral membrane proteins

A

associate with the polar head groups on one side of membranes

loosely associated
noncovalent interactions with lipid head groups or aqueous domains of integral membrane proteins

can be removed by disrupting ionic/polar interactions either with high salt or change in pH

purified peripheral proteins are no longer associated with any lipids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

integral membrane proteins

A

span the entire memrane or linked to membrane by lipid moiety

have asymmetry relative to the membrane; different segments in different compartments

tightly associated with the membrane
hydrophobic stretches in the protein interact with the hydrophobic regions of the membrane

removed by detergents that disrupt the membrane

purified integral membrane proteins still have phospholipids associated with them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

lipid anchors

A

some membrane proteins are lipoproteins

contain a covalently linked lipid molecule

  • long chain FA
  • sterol
  • isoprenoid
  • glycosylated phosphotidylinositol (GPI)

lipid can become part of the membrane

protein is now anchored to the membrane

process is reversible if enzyme can cleave lipid moiety off the protein
allows targeting of proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

types of integral membrane proteins: alpha helices

A

single transmembrane domain

many helices connected with loops

many domains not linked together

lipid anchored

combo of anchor and helix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

types of integral membrane proteins: beta sheets

A

barrels form with hydrogen bonds maximized by circle of beta strands

usually transporters

only found in bacteria, mitochondria, chloroplasts on the outer membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

structure of integral membrane proteins: helices

A

proteins made of helices need helices of about 20 AA to cross the membrane

amino acids must be hydrophobic if interacting with the membrane; need to be hydrophilic if interacting with other helices or central to a pore

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

structure of integral membrane proteins: beta sheets

A

need 7-9 AA in a strand to cross the membrane

amino acids with R groups pointing towards membrane must be hydrophobic

AA with R groups into barrel must be hydrophilic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

hydropathy index

A 
positive = phobic
negative = philic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

hydropathy plots

A

predicts helical transmembrane domains for most transmembrane proteins

hydropathy index vs amino acid

predictive plot

a way to look at known primary structure and try to determine if there are segments that form helices or cross the membrane

46
Q

amino acids in membrane proteins cluster

A

transmembrane segments are predominantly hydrophobic

Tyr and Trp cluster at nonpolar/polar interface because hydrophaty indexes are around zero
—> associate with polar head groups of membranes at transition

charged AA found only in aqueous domains

47
Q

membrane dynamics: lateral diffusion

A

individual lipids undergo fast lateral diffusion within the leaflet

48
Q

membrane dynamics: transverse diffusion

A

spontaenous flips from one leaflet to another are rare; charged head group must transverse the hydrophobic tail region of the membrane

important for the composition of the membrane so we have to have a way for this to happen otherwise you don’t get the differential composition between the two leaflets

flippases

49
Q

flippases

A

cause transverse movement of lipids

some use energy of ATP to move lipids against the concentration gradient

50
Q

floppases

A

moves phospholipids from cytosolic to outer leaflet

51
Q

scramblase

A

moves lipids in either direction toward equilibrium, no ATP with gradient

52
Q

flippase

A

PE and PS form outer to cytosolic leaflet

53
Q

membrane fusion

A

membranes can fuse with each other without losing continuity

can be spontaneous or protein mediated

54
Q

membrane fusions: proteins can

A

bend membranes to form a vesicle

bring a vesicle close enough to fuse with a membrane

55
Q

examples of protein-mediated membrane fusion

A

entry of influenza virus into host cell

release of NTM at nerve synapses

56
Q

cell membranes are permeable to

A

small nonpolar molecules that passively diffuse through the membrane

57
Q

passive diffusion of polar molecules involves

A

desolvation and thus has a high activation energy barrier

58
Q

transport across the membrane can be facilitated by proteins that provide an

A

alternative diffusion path (transporters)

59
Q

passive transport must be energetically favorable

A

concentration dependence

electrochemical gradient

60
Q

concentration dependence

A

solute moves towards equilibrium across the membrane high to low

61
Q

electrochemical gradient

A

solute moves toward charge equilibrium across the membrane

62
Q

active transport

A

solute moving isn’t energetically favorable to the system

63
Q

polar solutes need alternative paths to cross cell membranes

A

protein helps with the desolvation process and keeps molecules from interacting with the hydrophobic core

lowers activation energy for transport, makes movement faster

64
Q

C2

A

destination of molecule

65
Q

C1

A

original location of molecule

66
Q

dGt is negative if

A

C2 < C1

67
Q

dPsi

A

charge on the membrane

68
Q

dPsi is negative when

A

molecule is moving towards the negative side

69
Q

dPsi is positive when

A

molecule is moving towards the positive side

70
Q

integral membrane proteins: ion channels

A

passive transport

molecules move down their concentration gradient at rates close to diffisuion

generally don’t become saturated

71
Q

integral membrane proteins: transporters

A

can be active or passive

move molecules slower than diffusion

can move molecules up their concentration gradient

can be saturated

72
Q

cotransport

A

2 or more molecules

73
Q

glucose transporter

A

12 transmembrane helices

amphipathic

hydrophilic core for glucose

74
Q

glucose transporter model

A

2 conformations of glucose transporter

uniporter in either direction

passive transport

transport rarely stops because metabolism allows cell to keep glucose low inside or phosphorylates it so it cannot be bound by the transporters

we want [glucose] high = outside so it can enter the cell

75
Q

glucose symporter

A

on apical surface

glucose and sodium secondary active

76
Q

sodium potassium exchanger

A

prevents sodium buildup in the cell

77
Q

glucose uniporter

A

basal surface

GLUT2

78
Q

bicarbonate transporter

A

antiporter;

CO2 to lungs

antiport speeds up bicarbonate transport and maintains the electrochemical potential across the membrane

79
Q

bicarbonate: in tissues

A

CO2 diffuses in and is converted to bicarbonate via carbonic anhydrase

bicarbonate transports out into the plasma via a Cl- bicarbonate exchanger

80
Q

bicarbonate: in lungs

A

bicarbonates enters the blood cell via bicarbonate-Cl- exchanger

converted to CO2 via carbonic anhydrase and CO2 diffuses out into the lungs to be exhaled

81
Q

ABC transporters

A

primary active

ATP Binding casette

uses ATP hydrolysis to drive transport of substrates

ATP hydrolysis occurs separately from the transporter and the hydrolysis changes the conformation of the protein and allows transport up a gradient

82
Q

Proton transport

A

energy of ATP hydrolysis can be used to pump protons across the membrane against a gradient (Ftype ATPase)

pH control

energy of proton gradient can be used to synthesize ATP

ATP synthase in chloroplast and mitochondrial membranes

83
Q

ion channels

A

passive transport

potassium enters cavity of channel, hydrated by water molecules

helix in transporters have diples; negative dipole helps binding of the K+ ion

K+ interacts with the carbonyl oxygens on amino acids in the binding site

binding slots desolvate K+ ions with oxygens on carbonyls

K+ fits into alternating slots

84
Q

hydrolysis of ATP is favorable under standard conditions

A

charge separation in products makes the reaction favorable

products are better solvated

products are stabilized with resonance, making the reaction more favorable

85
Q

the actual free energy change of a process

A

depends on the standard free energy (-30.5 for ATP hydrolysis)

actual concentrations of reactants and products

86
Q

the free-energy change is more favorable if

A

the ratio of reactant concentration to product concentration exceeds that at standard concentration

[ATP] is kept high in cells

if [ATP] levels get low, fewer molecules and less energy to drive reactions

87
Q

dG for ATP hydrolysis in erythrocytes

A

-52kJ/mol

88
Q

many phosphorylated compounds have a large dG’* for hydrolysis

A

electrostatic repulsion with the reactant is relieved

the products are stabilized with resonance or more favorable solvation

product undergoes tautomerization

89
Q

phosphates can be transfered from

A

compounds with more negative dG to those with less negative dG

90
Q

NTP reactions: activation of a reaction

A
  1. Pi or PPi or NMP (AMP) is bound to substrate or enzyme

2. phosphate containing moiety is displaced

91
Q

energy quantities

A

phosphoenolpyruvate

1,3-bisphosphoglycerate

phosphocreatine

ATP

glucose-6P

glycerol-6P

92
Q

in some instances ATP or GTP are hydrolyzed directly

A

provides energy for movement

ribosome movement on mRNA

93
Q

phosphorylation of proteins can change conformation

A

to cause activity

Na+K+ATPase transports ions using cycling of phosphorylation

94
Q

2ADP —> ATP + AMP

A

when ATP is low

can run in reverse when ATP is high

95
Q

thioesters

A

sulfer atom replaces oxygen

hydrolysis generates a carboxyllic acid

product is resonance stabilized

dG’* is negative

96
Q

most common types of redox reactions in biological systems

A

transfer of single electrons with or without simultaneous transfer of protons

transfer of a hydride ion

transfer of electrons to molecular oxygen

incorporation of one or both oxygen atoms from O2 into a substrate

97
Q

most common types of redox reactions in biological systems: transfer of single electrons

A

with or without simultaneous transfer of protons

enzymes require cofactors

occur predominantly in mitochondria as part of the electron transport chain and in chloroplasts or cyanobacteria in photosynthesis

98
Q

enzymes involved in transfering of single electrons: cofactors

A

hemes (change in oxidation state of iron between Fe2+ and Fe3+)

iron-sulfur proteins

copper ions (Cu+/Cu2+)

flavin nucleotides (FMN or FAD)

99
Q

most common types of redox reactions in biological systems: transfer of a hydride ion

A

one proton plus 2 electrons

NAD+/NADH and NADP+/NADPH are usually involved

catalyzed by dehydrogenases or reductases

100
Q

most common types of redox reactions in biological systems: transfer of electrons to molecular oxygens

A

reduced to water or H2O2 in this process

catalyzed by oxidases

101
Q

most common types of redox reactions in biological systems: incorporation of one or both oxygen atoms from O2 into a substrate

A

catalyzed by oxygenases

102
Q

reduced organic compounds

A

serve as fuels from which electrons can be stripped off during oxidation

103
Q

oxidation reduction reactions

A

many biochemical oxidation-reduction reactions involve transfer of 2 electrons

in order to keep the charges in balance, proton transfer often accompanies electron transfer

in many dehydrogenases, the reaction proceeds by a stepwise transfer of proton and hydride

104
Q

measuring the standard reduction potential of a redox pair

A

measures electron movement

test cell with equal lactate and pyruvate conjugate redox pair

at standard hydrogen electrode: water half reaction takes place

if the electron affinity of the oxidized form of the conjugate redox pair is higher than the electron affinity of H3O+, the standard reduction potential is positive; if not, it is negative

  • *electrons go to test cell —> higher reduction potential
    • electrons go to reference cell —> lower reduction potential
105
Q

reduction potential (E)

A

affinity for electrons; interest of molecule to take electrons and be reduced

electrons transfered from molecules with lower E to higher E

pH of 7 and 1M concentrations assumed

106
Q

NAD+ and NADP+

A

common redox cofactors

coenzymes (can dissociate from enzyme after the reaction and react elsewhere to return to original redox state)

hydride from an alcohol is transferred to NAD+ giving NADH

107
Q

NADPH

A

usually used to reduce other molecules

108
Q

NAD+

A

breakdown of molecules

109
Q

NADP+

A

synthesis

110
Q

tossman fold

A

proteins have specific domains for NAD(H) or NADP(H) binding

111
Q

flavin cofactors

A

allow single and double electron transfers

organic cofactor used in oxidative phosphorylation and photosynthesis as an electron carrier in electron transport

prosthetic groups (tightly bound to enzymes)

FAD or FMN can accept one electron and one hydrogen at a time to make FADH2 or FMNH2

can also pass or accept 2 electrons and 2 hydrogens (usually intermediary between NAD+/NADH and metal ions)

112
Q

FMN or fAD

A

depends on the enzyme

MCB 3010 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions