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BIOL-3221 > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

The plasma membrane exhibits a tri_____ appearance

A

trilaminar

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2
Q

7 functions of the plasma membrane

A

1) compartmentalization
2) scaffold for biochemical activities: membranes provide a framework that organizes enzymes for effective interactions (ex/ photosynthetic enzymes are all enclosed in a membrane and held in the chloroplast

3) selectively permeable barrier
4) transporting solutes
5) responding to external stimuli ex/ signal transduction
6) cell-cell recognition (intracellular interactions)
7) energy transduction

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3
Q

example of how a membrane conducts enerygy transduction

A

oxidative phosphorylation occurs in the mitochondrial membranes

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4
Q

intracellular organelles are also known as ______

A

membrane bound organelles

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5
Q

why are red blood cells best for studying membrane structures?

A

1) plentiful
2) easy to obtain
3) anucleate
4) no organelles

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6
Q

How did gorter and grendel propose the lipid bilayer?

A

realized that there was 2 times as much membrane lipids as there was surface area

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7
Q

what technique was used to find embedded proteins of the lipid bilayer?

A

the freeze fracture technique; freezing the membrane of RBC, using a knide to separate the 2 layers. used molten metal to create a cast to analyze and find integral proteins embedded in the membrane.

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8
Q

prood of embedded proteins

A

1) proteins that were isolated had hydrophobic regions
2) labelling proteins showed portions that were exposed on both sides
3) proteins wre mobile in the plane of the membrane
4) freeze fracture techniques confirmed existence of transmembrane proteisn

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9
Q

Fluid mosaic model

A

the core lipid bilayer exists in a fluid state, and is capable of movement. the membrane proteins form a mosaic of particles penetrating the lipids. Membranes are DYNAMIC

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10
Q

T/F: lipid to protein ratio are the same for all cells membanes

A

false. the composition of membranes are dependent on their roles in the cell

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11
Q

how are lipids and proteins often bound together?

A

usually through non-covalent bonds (vanderwaal interactions). allows for migration around the membrane.

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12
Q

3 main types of membrane lipids

A

1) phospholipids/ phosphoglycerides
2) sphingolipids
3) cholesterol

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13
Q

what is a phosphoglycerides

A

membrane lipids that contain a phosphate group with a glycerol backbone and two hydrocarbon chains

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14
Q

What kind of glycerids are membrane lipids?

A

Di glycerides. the third site has a phosphate group attached to create a polar head

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15
Q

examples of phospholipids

A

phosphatidyl choline
phosphatidul serine
phosphatidyl ethanolamine
phosphatidyl inositol

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16
Q

phosphatidic acid

A

a fatty acid that has no additional group added to the phosphate on the glycerol backbone

CH-hydrocarbon
CH-hydrocarbon
CH-phosphate

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17
Q

What is a sphingolipid

A

a ceraminde formed by the attachment of sphingosine to fatty acid by the sphingosine’s amino group

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18
Q

what is a sphingosine

A

amino alcohol containing a long hydrocarbon chain

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19
Q

what kind of lipid arises if a carbohydrate is attached to sphingosine?

A

a glycolipid

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20
Q

what is sphingo myelin

A

a phosphocholine attached to a sphingosine, which is an amino alcohol with a hydrocarbon chain

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21
Q

what is a cerebroside

A

a simple sugar attached to sphingosine (a type of glycolipid)

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22
Q

if a complex sugar or saalic acid is bound to a spingoside, a _____lipid is formed

A

a ganglioside glycolipid

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23
Q

what would happen if there are no gangliosides in a body

A

severe neurodegeneration

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24
Q

how is cholesterol oriented in the membrane

A

the hydroxylgroup of cholesterol is on the membrane surface, with the hydrophobic ring structure in the inner portion of the membrane.

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25
Q

why are hydrophobic tails never in the aqueous face?

A

because it is not thermodynamically favorable

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26
Q

liposome

A

a continuous lipid bilayer that is formed SPONTANEOUSLY when lipids are placed in aqueous solution

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27
Q

T/F: both faces of the lipid membranes are symmetrical

A

false; each face has different lipid and protein composition

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28
Q

T/F; membrane lipids flip flop easily

A

false, they can move around laterally but very rarely flip flop

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29
Q

where are carbohydrates found on the membrane

A

on the OUTSIDE face, facing the EXTRACELLULAR space

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30
Q

what process attaches carbohydrates onto a lipid? what kind of linkage?

A

glycosylation, covalent linkages hold the oligosaccharide in place

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31
Q

roles of glycoproteins and glycolipids

A

glycoproteins have SHORTER branches of carbs for other interactions with other cells

glycolipids have LONGER branches for cell to cell recognition.

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32
Q

what two types of linkages connect carbohydrates to a protein?

A

1) N-linkages

2) O-linkages

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33
Q

what is an N linkage

A

a linkage that connects a carb to a protein. linked through N-acetylglucosamine to asparagine

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34
Q

What is an Olinkage

A

a linkage that connects a carb to a membrane protein. linked through N-acetylgalactoseamine to serine or threonine

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35
Q

how do glycolipids determine blood type?

A

Blood type O; no terminal sugar
Blood type A; N-Acetylglucosamine attached to end.
Blood type B; galatose at end

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36
Q

how is an integral membrane protein able to transport a hydrophillic solute across the interior of the membrane?

A

the protein may have a hydrophillic core that forms aqueous channels in the membrane spanning region

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37
Q

three main functions of transmembrane proteins

A

1) as receptors
2) as channels
3) as electron transport agents (ex/ succinate dehydrognase)

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38
Q

how are integral membranes sealed into the lipid “wall”

A

amino acids in the transmembrane domain form vanderwaal forces with the fatty acyl chains of the bilayer, allowing the protein to be anchored

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39
Q

portions of the integral membrane protein that span on either the extracellular or intercellular space are more ____ in shape

A

globular

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40
Q

How is integral membrane distribution studied?

A

freeze fracture analysis

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41
Q

how does a non-ionic detergent allow for the study of integral membrane proteins?

A

they won’t ionize the membrane protein and allows the native conformation to be seen. ex/ Trition-X

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42
Q

how does an ionic detergent allow for the study of integral membrane protein

A

it denatures the protein and usually coats it with negative charge (SDS), allows for gel electrophoresis conduction (PAGE)

the more negative the charge coated, the larger the protein is, allows you to characterize size based on how far it moves down the gel

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43
Q

______ crystallography allows you to determine integral membrane protein structure. What is necessary to conduct this?

A

X ray crystallography. you need a really pure smaple

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44
Q

what shape is the transmembrane domain of an integral membrane?

A

alpha helix

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45
Q

how is amino acid sequence determined in an integral membrane protein?

A

by a hydropathy plot. each site along the polypeptide is ranked on hydrophobicity based on FREE ENERGY in a PARTICULAR SOLVENT

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46
Q

how are spatial relationships/conformation determined in an integral membrane protein? (2 types)

A

1) site directed mutagenesis

2) electrone resonance

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47
Q

what feature of a protein is studied when site directed mutagenesis is conducted? what is site directed mutagenesis?

A

site directed mutagenesis is a form of studying the spatial relationships of an integral protein. it is done by changing the GENETIC CODE of a protein so that a different amino acid is coded, resulting in a DIFFERENT AMINO ACID SEQUENCE, resulting in a DIFFERENT CONFORMATION.

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48
Q

what premise does site directed mutagenesis operate on?

A

on the fact that proteins are dynamic and that a change in AA sequence will change their conformation AND INTERACTIONS WITH THEIR ENVIRONMENT, and thus their function

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49
Q

What is electron spin resonance?

A

a method of determining a protein’s spatial relationship/conformation. can be conducted WHEN THE PROTEIN IS STILL FUNCTIONING.

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50
Q

T/F: peripheral proteins are connected to the lipid membrane by covlent bonds

A

false. they are held by weak bonds. they can be easily removed with a solvent

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51
Q

how can a peripheral protein be attached to the membrane (two ways_

A

1) by NON COVALENTLY bonding to the polar head of a lipid

2) by NON COVALENTLY bonding to an integral protein

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52
Q

a GPI-linked protein is an example of a ______ protein. where are they found? how are they removed?

A

a GPI-linked protein is an example of a LIPID ANCHORED protein. found on the outer leafelet. removed by inositol specific phospholipases

GPI-linked= glucophosphatidylnositol-proteins.

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53
Q

Src and Ras proteins are an example of ____ proteins

A

example of a lipid anchored protein, attached to the CYTOPLASMIC side. involved in transforming cells to malignant state

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54
Q

3 types of membrane protein

A

1) integral
2) peripheral
3) lipid anchored proteins

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55
Q

unsaturated fatty acids and cholesterol _____ the transition temperature of a membrane. what does this do?

A

lowers the transition temperatuer. the membrane stays fluid at lower temperatures.

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56
Q

2 main states of a membrane

A

1) liquid crystal

2) gel phase

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57
Q

what role does cholesterol play in the membrane?

A

abolishes the sharp transition temperature to create an “intermediate fluid,” membrane will be fluid at lower temps.

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58
Q

the longer/shorter the fatty acyl chain of the membrane, the lower it’s melting point

A

the SHORTER the FA chain, the lower its melting temperature. Short FAs will melt at lower temperatures

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59
Q

how are membranes made?

A

by preexisting membranes

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60
Q

how do membranes cope with new environments?

A

by changing their fatty acid composition

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61
Q

what type of enzyme desaturates single bonds to double bonds?

A

desaturases

62
Q

what do phospholipases and acyltransferases do?

A

phospholipases: spilt FAs from glycerol backbone
acyltransferrases: transfer FAs between phospholipids

63
Q

two ways to remodel a lipid bilayer

A

1) switching from single to double bonds (desaturases)

2) switching acyl groups among the phospholipids (phospholipases and acyl transferases)

64
Q

what are lipid rafts?

A

patches of cholesterol and sphingolipids that float within more fluid and disordered portions of the bilayer

65
Q

what portions of the lipid bilayer are GPI-anchored proteins found?

A

found on the outer leaflet on a LIPID RAFT.

66
Q

purpose of lipid rafts

A

to serve as an organizer and provides an environment for cell-surface receptrs to interact with other membrane proteins

67
Q

what experiment proved that proteins could move?

A

a cell fusion experiment. at the beginning of fusion, the proteins of the respective celled remained on their half of the new cell. But as time went on, the proteins from human and rat cells began to intermingle

68
Q

what would you see if you conducted the cell fusion experiment at a low temperature

A

there would be less intermingling of the two proteins because the lipid membrane will be frozen (hard for eveyrthing to move)

69
Q

What is FRAP?

A

fluorecense recovery after photobleaching. used to detect protein movement. bleach a spot on the cell with a laser. see fluorecent tagged proteins move into the spot, you can no longer see the bleached spot– shows that the proteins moved

Rate of fluorecence recovery = rate of diffusion of mobile proteins

70
Q

findings of FRAP

A

1) membrane proteins move SLOWER than liposome proteins

2) some proteins will not diffuse back into the photobleached spot, indicating some proteins are stationary

71
Q

T/F; membrane proteins move slower than liposome proteins

A

true, probs due to hinderance

72
Q

disadvantages of FRAP?

A

1) need a high protein concentration

2) hard to distinguish TRUE protein mobility. protein studied might just be too far away to fill the photobleached spot

73
Q

in single particle tracking, how are proteins labelled? How are protein movement seen?

A

labelled with gold particles. movement seen with video microscopy

74
Q

ways of watching protein movement

A

1) FRAP
2) single particle tracking
3) genetic modification

75
Q

T/F: larger proteins move faster than smaller proteins

A

false

76
Q

strongest force that makes a protein stay stationary

A

integral membrane protein is thought to be bound to he MEMBRANE SKELETON

77
Q

What are optical tweezers?

A

generally found that proteins can be dragged for a certain distance until the protein encounters a barrier in the membrane.

78
Q

how can genetic modification be used to study mobility

A

cells whos cytoplasmic proteins have been genetically delted often move greater distances, indicating that barriers reside on the CYTOPLASMIC side of the membrane

79
Q

which side do most membrane barriers reside

A

on the cytoplasmic side (the membrane skeleton in the cell)

80
Q

how are phospholipids mobility hindered?

A

by integral protein fences that prevent mobility.

81
Q

3 main cells making up epithelia

A

1) apical cells: regulation of nutrient intake. faces the lumen
2) lateral cells: cell cell recognition, adhesion
3) basal membrane: cell-muscle connection, generation of ion gradients.

82
Q

how can you get a membrane ghost for analyss?

A

use a red blood cell. make it undergo hemolysis by placing it in a hypotonic solution. water will enter cell and burst cell. all cell contents will be removed, leaving the membrane.

83
Q

how can you separate proteins from a red blood cell membrane?

A

make cell undergo hemolysis by placing it in hypotonic solution, then after a ghost membrane is obtained, use PAGE electrophoresis (SDS to coat with negative charge).

84
Q

three main proteins of the RBC

A

1) glycoprotein/ BAND THREE
2) glycoporin A
3) spectrin

85
Q

purpose of band 3/glycoprotein in RBC

A

exchanged Cl- and HCO3- across a red cell membrane. When Co2 is released in the lungs, HCO3- moves out of RBC and CL- moves in through the glycophorin channel

86
Q

How does glycophorin A help an RBC?

A

prevents RBC’s from clumping by containing negatively charged oligosaccharide chains, which repel each other

87
Q

Role of spectrin in RBC? HOw is it attached?

A

a major component of the membrane skeleton. attached to membrane surfacce by NON COVALENT BONDS TO ANKYRIN (another peripheral protein that is non covalently bonded to band 3/glycoprotein)

88
Q

what is Ankryrin

A

another peripheral protein that is non covalently bonded to band 3/glycoprotein)

89
Q

2 means for substance movement

A

1) passively via diffusion

2) actively via energy coupling

90
Q

diffusion is a _____ process that moves material from a region of high to low concentration

A

diffusion is a SPONTANEOUS PROCESS

91
Q

free energy chanrge during difusion of NON electrolytes depends on the ____ gradient, while free energy change during diffusion of ELECTROLYTES depends on the ____- gradient

A

free energy chanrge during difusion of NON electrolytes depends on the CONCENTRATION gradient, while free energy change during diffusion of ELECTROLYTES depends on the ELECTROCHEMICAL gradient

92
Q

two types of non mediated diffusion,

A

1) simple diffusion. no proteins. small molecules can pass through the membrane
2) channels. no conformatinal change, but a channel protein is needed. no energy used. used to move ions

93
Q

how does transporter mediated passive transport work

A

uses a protein and binding of a substrate triggers conformational change, making it release the substrate onto the other side of the membrane. no energy is needed.

94
Q

three things that determine the lipid permeability of a molecule

A

1) partition coefficient
2) molecular size
3) polarity

95
Q

what is partition coefficient

A

helps determine how lipid soluble a molecule is. solubility of a substance in a NON POLAR solvent OVER its solubility in WATER

96
Q

Osmosis

A

diffusion of WATER through a SEMIPERMEABLE MEMBRANE from HIGH TO LOW concentrsion

97
Q

turgor pressut

A

internal pressure that plants develop that pushes against the surrounding cell wall

98
Q

in hypertonic solutions, the plant cell will_____

A

plasmolyze. plasma membrane pulls away from surrounding cellw all due to water loss.

99
Q

How does osmosis work?

A

in salt solution, water forms a hydration shell around Na+/Cl- ions. water molecules are immobile in a hydration shell. the less amount of salt, the more water molecules are free to move, therefore, water will move from hypo to hyper tonic solutions

100
Q

aquaporins are associated with _____ transport of water in plants

A

passive transport.

101
Q

How do aquaporins remain specific to water and not allow protons to flow through?

A

they have N203 and N68 amino acids that ATTRACTS the oxygen atom of each water molecule as it speeds through the constriction of the protein. This interactions prevents H2O from Hbonding with it’s neighbors at this point in the protein, preventing proton hopping and closes the bridge that normally allows protons to move from one water molecule to the next.

102
Q

conductance

A

rapid movement of ions across the concentration gradient. important for nerves

103
Q

what did patch clamp technique find?

A

discovered ion channels by measuring the voltage of oe cell/

104
Q

three types of gated ion channels

A

1) voltage gated
2) ligand gated
3) mechanogated

105
Q

What type of organism does KsCa belong to?

A

it is a potassium channel of a prokaryotic cell

106
Q

the KsCa channel is made up of ____ subunits arranged to create a pore. only ___ K+ ions can be present at the filter at once.

A

the KsCa channel is made up of 4 subunits arranged to create a pore. only 2 K+ ions can be present at the filter at once.

107
Q

T/F potassium channels can pump K+ against its gradient.

A

false. it’s a channel. it only allows potassium to flow across its gradient

108
Q

what amino acids line the selectivity filter of KsCa?

A

GYGVT

109
Q

2 domains of the eukaryotic potassium channel

A

1) pore domain. permits the selective passage of K+ ions

2) voltage sensing domain: helices S1-S4 that senses charge across the plasma membrane

110
Q

What kind of gated channel is a potassium channel

A

voltage gated

111
Q

how many helices make up Kv (eukaryotic potassium channel)

A

6 membrane spanning helices

112
Q

in a prokaryotic potassium channel, which helices are moved in order to open the channel

A

the M2 and M1 helices must swing open

113
Q

3 different conformatinal states of a eukaryotic K+ ion channel?

A

1) rest: all subunits are closed
2) open: ions can move
3) inactivated: cytoplasmic inactivation peptide fits inside and BLOCKS the pore

114
Q

four characteristics of facilitated diffussion

A

1) passive
2) saturable
3) regulated
4) specific

115
Q

which types of molecules would need to undergo facilitated diffusion

A

large substances that need to cross the membrane across their gradient

116
Q

How does facilitate diffusion transport molecules?

A

binding of a solute to the facilitative transporter on one side of the membrane thought to trigger conformational change in the protein, allowing it to diffuse down its concentration gradient to the other side.

117
Q

T/F facilitated diffusion exhibit michalis menton kinetics

A

true. it can be saturated when all the transport proteins are being used.

118
Q

provide an example of facilitated diffusion

A

GLUT1 or GLUT2. moves glucose with its concentration gradient

119
Q

how does insulin stimulate the uptake of glucose into the blood

A

insulin binds to its receptor and causes vesicles containing glucose transporteers to bind to the membrane, allowing GLUTs to be membrane bound and active (facilitated diffusion)

120
Q

Proteins associated with active transport are called ____

A

pumps

121
Q

example of a protein pump

A

Na+/K+ ATP ase

122
Q

P type pump

A

phosphorylation causes changes in conformation and ion affinity that allows transport against gradients

123
Q

T/F: plants have Na+/K+ ATPase to keep their solutes in check

A

false. Na+/K+ ATPase pumps are only found in animals

124
Q

What are the conformation states of Na+/K+ ATPase

A

E1 conformation. high affinity for Na+, low affinity for K+
ATP hydrolysis phosphorylates ATPase, becomes E2
E2 conformation. low affinity for Na+, releases Na+, high affinity for K+, binds K+.

phosphate group is removed and ATPase goes back to E1.

potassium binding dephosphorylates the protein

Has a low affinity for K+, so it released K+ into the cell.

125
Q

Ca2+ ATPase

A

a P type pump. found in ER, transports Ca2+ out of the cytosol

126
Q

H+ ATPase

A

P type pump. seen in plants, used for secondary transport

127
Q

H+/K+ ATPase

A

secretes solution of concentrated acid into the stomach.

128
Q

Which type of pump is responsible for stomach acidity? Which cells have this pump?

A

H+/K+ ATPase P type pump. Parietal cells have this pump, located in active vesicles

129
Q

mechanism for stomach acid secretion

A

parietal cells contain vesicles of H+/K+ ATPase pump. When food is injested, histamine is released and triggers these vesicles to fuse to with cell membrane of parietal cells and the H+/K+ATPase pumps get activated.

H+ is pumped out of the cell, and potassium enters the cell.

130
Q

Example of an antiport system

A

Na+/K+ ATPase, H+/K+ ATPase

131
Q

How does prilosec treat acid reflux?

A

blocks H+/K+ ATPase

132
Q

How does Zantac treat acid reflux?

A

prevents the binding of histamine, cannot activate H+/K+ ATPase at all.

133
Q

Vtype pumps

A

use energy from ATP but the protein pump itself does not get phosphorylated.

134
Q

ABC transporters

A

ATP-binding cassette transporters have regulatory ATP binding sites

135
Q

what is secondary active transport

A

using ionic gradients created by primary active transport to drive another molecule against its concentration gradient.

136
Q

example of secondary active transport

A

ex/ using sodium to drive glucose against its gradient. sodium ionic gradient was created by Na+/K+ ATPase (active transport). Sodium then flows back into the cell (across its cocnentration gradient), bringing a glucose with it. the glucose moves AGAINST its concentration gradient. the glucose was transported by SECONDARY active transport

137
Q

co transport

A

moving two different molcules the same direction (ex/ sodium and glucose secondary active transport)

138
Q

refer back to drawing of sodium glucose secondary transporter in epithelial cells

A

glucose moves into apical cells by secondary active transport via cotransport with sodium. once in the cells, glucose moves out of the basal cells to the blood stream using GLUT FACILITATED diffusion transporter

139
Q

how can light be used for active transport?

A

absorb light energy to transport protons out of the cell. proton gradient can be used to make ATP/cellular processes

140
Q

4 types of active transport

A

1) ATP hydrolysis
2) using co transport (ex/ sodium glucose secondary transport)
3) light
4) using electrons

141
Q

irritability

A

reponding to external stimulation

142
Q

schwann cells

A

cells with myelin wrapped aroung it

143
Q

how can cell resting potential be monitored?

A

using a microelectrode

144
Q

T/F: K+ leak channels move potassium along the gradient

A

true. K+ moves out of cell through leak channels because Na+/K+ ATPase has been pumping K+ into cell

145
Q

T/F: K+ leak channels open and close depending on potassium concentration

A

false. they are ALWAYS OPEN. K+ leak channels are not responsive to electrochemical concentration signals.

146
Q

all or none law

A

there is no in-between. as soon as a membrane is depolarized to -50mV from -70, the maximum reponse AP will occur. NOTHING will occur at -49mV.

147
Q

how does the diameter of an axon affect the speed of AP

A

increased diameter= decreased resistance = increased speed of action potential

148
Q

saltatory conduction

A

sodium ion flow from na+ channels in Node of Ranvier depolarized the next node of ranview. Conductive activity jumps from node to node

149
Q

neuromuscular junction

A

site where branches from motor axon form synapses with the muscle fibers of the skeletal muscle.

150
Q

an AP triggers the opening of a ____ channel, which causes the exocytosis of a vesicle holding neurotransmitters

A

triggers the opening of a calcium channel

BIOL-3221 (6 decks)

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