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Cell Biology > Chapter 15: The Plasma Membrane > Flashcards

Chapter 15: The Plasma Membrane Flashcards

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1
Q

what are the 5 functions of membrane?

A
  1. boundary & selective permeability
  2. organization & localization
  3. proteins for transport processes
  4. receptors for signal detection
  5. cell-to-cell communication
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2
Q

what are the main components of membranes?

A

phospholipids

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3
Q

what are phospholipids made of?

A
  • hydrocarbon tails
  • glycerol
  • phosphate
  • PC, PS, PE, PI, sphingomyelin
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4
Q

the phospholipid tails are

A

nonpolar & hydrophobic

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5
Q

the phospholipid heads are

A

polar & hydrophilic

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6
Q

membranes are impermeable to all

A

hydrophilic molecules

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7
Q

membranes are permeable to small…

such as

A

hydrophobic molecules

steroid hormones

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8
Q

membrane bilayers are

A

viscous fluids NOT solids

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9
Q

the outer portion of the membrane is made of

A

PC, sphingomyelin, glycoproteins

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10
Q

the inner portion of the membrane is composed of

A

PS, PE, PI

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11
Q

the membrane is composed of about

A

50% proteins

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12
Q

where is sphingomyelin synthesized?

A

in the Golgi

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13
Q

what aids in creating the cell membrane potential?

A
  • the negative charges of head groups
  • ion concentration in the cytosol
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14
Q

define phase transition

A

changing from one state to the other

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15
Q

the plasma membrane state can change very quickly over a very

A

narrow temperature range

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16
Q

what stabilizes both stages of a membrane’s phase transition?

A

cholesterol

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17
Q

phase transition is aka

A

a cell’s fluidity

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18
Q

___________ determines the proper function of the membrane

A

fluidity

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19
Q

what are the 4 determinants of fluidity?

A
  1. fatty acid length
  2. type of fatty acid
  3. cholesterol
  4. lipid rafts
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20
Q

how is fatty acid length a determinate of fluidity?

A

gel state is stabilized by van der Waals interactions
- short chains have less surface area for interaction
- short chain lipids melt at lower temperatures

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21
Q

short-chain lipids are

A

more fluid

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22
Q

long-chain lipids are

A

less fluid

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23
Q

what are the 2 types of fatty acids?

A
  1. saturated fatty acids
  2. unsaturated fatty acids
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24
Q

do saturated fatty acids increase or decrease membrane fluidity?

A

decrease

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25
Q

do unsaturated fatty acids increase or decrease membrane fluidity?

A

increase

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26
Q

why do unsaturated fatty acids increase membrane fluidity?

A

b/c they contain = bonds which increase the amount of proteins in the membrane and the passage of molecules

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27
Q

cholesterol at high temperatures

A

decreases fluidity

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28
Q

cholesterol at low temperatures

A

increases fluidity

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29
Q

lipid rafts are semisolid patches of

A

sphingomyelin, glycolipids, & cholesterol

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30
Q

lipid rafts are

A

discrete membrane domains

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31
Q

lipid rafts are thought to move

A

laterally within the plasma membrane

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32
Q

lipid rafts are thought to associate w/

A

specific proteins

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33
Q

what is the fluid mosaic model?

A

the plasma membrane w/ all the proteins, phospholipids, cholesterol. lipid rafts, and carbohydrate components

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34
Q

membrane proteins move _____ along the surface of the membrane

A

laterally

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35
Q

who observed the migration of labeled proteins and demonstrated the fluid mosaic model?

A

Frye and Edidin

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36
Q

what are 2 addition features of the plasma membrane?

A
  1. glycocalyx
  2. caveolae
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37
Q

describe glycocalyx

A

the carbohydrate coat around carbohydrate portions of glycolipids found on the OPM

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38
Q

glycocalyx protects cells from

A

ionic/mechanical stress

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39
Q

the glycocalyx is a barrier to

A

invading microorganisms

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40
Q

oligosaccharides participate in

A

cell-cell interactions

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41
Q

caveolae are

A

small invagination of the plasma membrane

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42
Q

caveolae are organized by

A

caveolin

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43
Q

caveolae carry out

A

receptor-mediated & receptor-independent endocytosis

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44
Q

what are the 3 main categories of membrane proteins?

A
  1. integral
  2. peripheral
  3. lipid anchored
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45
Q

integral proteins either

A

completely or partially transect the membrane

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46
Q

what type of integral proteins DO NOT transect the mem. all the way?

A

monotopic

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47
Q

integral proteins are typically found on the

A

cytosolic side of the plasma membrane

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48
Q

peripheral proteins DO NOT interact w/

A

membrane lipids directly

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49
Q

peripheral proteins interact w/

A

integral proteins

protein that is already in the mem.

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50
Q

lipid anchored proteins are

A

covalently linked to membrane phospholipid

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51
Q

lipid anchored proteins are inserted to the

A

cytosolic side of the membrane after being translated & folded

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52
Q

what is the exception of lipid anchored proteins? why?

A
  • GPI anchors
  • they are inserted to the outside of the membrane
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53
Q

what are 4 ways in which membrane proteins can be connected to the membrane?

A
  1. amphipathic α-helix
  2. hydrophobic loop
  3. lipidation
  4. electrostatic/ionic interactions
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54
Q

amphipathic α-helix protein connection to the membrane sits __________ to the membrane

A

parallel

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55
Q

lipidation is when a protein is

A

covalently bound to membrane lipids

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56
Q

explain the electrostatic/ionic interactions which some proteins can use to be connected w/ the plasma membrane

A

+ charged R groups of aa interact with - charged phospholipids

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57
Q

transmembrane proteins that form channels typically use

A

α-helices to cross the membrane

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58
Q

other transmembrane proteins that form channels can use

A

β-barrels

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59
Q

β-barrels are common in

A

aquaporins

seen in kidney nephron

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60
Q

proteins are anchored to the plasma membrane by

A

lipids and glycolipids

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61
Q

what are the proteins involved in anchoring other proteins to the cytosolic side of the plasma membrane?

A
  • Src
  • Ras
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62
Q

Ras proteins makes connections through

A

disulfide bonds

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63
Q

Src proteins make connections through

A

ionic interactions

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64
Q

detergents solubilize

A

integral mem. proteins

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65
Q

detergents separate what from membranes?

A

proteins

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66
Q

detergents are synthesized to be

A

amphipathic

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67
Q

detergent that is considered to be ‘mild’ stringency

A

SDS

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68
Q

detergent that is considered to be ‘high’ stringency

A

Triton X-100

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69
Q

what are the 3 types of transport of molecules across the plasma membrane?

A
  1. passive/simple diffusion
  2. facilitated diffusion (passive transport)
  3. active transport
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70
Q

what are the 2 types of active transport

A
  1. indirect
  2. direct
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71
Q

passive/simple diffusion require NO

A

energy input

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72
Q

what are the 3 main factors that affect the passive diffusion of molecules?

A
  1. size
  2. polarity
  3. ion permeability
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73
Q

how can size affect the passive diffusion of molecules?

A

b/c the mem. is more permeable to small rather than large molecules

74
Q

how can polarity affect the passive diffusion of molecules?

A

the mem. is permeable to nonpolar & less permeable to polar molecules

75
Q

in general lipid bilayers are VERY

A

impermeable to ions

76
Q

phospholipid bilayers are ONLY permeable to

A
  • gases
  • small hydrophobic molecules
77
Q

facilitated diffusion is aka

A

passive transport

78
Q

does facilitated diffusion require energy?

A

NO

79
Q

facilitated diffusion can be described as movement in the direction of

A

relative concentrations

80
Q

in facilitated diffusion molecules do NOT dissolve

A

in the membrane

81
Q

facilitated diffusion is mediated by

A

proteins

82
Q

facilitated diffusion typically transports

A

charged or polar molecules

83
Q

give some examples of the charged or polar molecules that are transported through facilitated diffusion

A
  • aa
  • nucleosides
  • sugars
  • ions
84
Q

what are the 2 classes of proteins that mediated facilitated diffusion?

A
  1. carrier proteins
  2. channel proteins
85
Q

what are the 2 types of transporters?

A
  1. uniport
  2. cotransport
86
Q

what are the 2 types of cotransport?

A
  1. symport
  2. antiport
87
Q

describe the symport cotransport

A

the transport of two molecules in the SAME direction

88
Q

describe the antiport cotransport

A

the transport of two molecules in OPPOSITE directions

89
Q

what is an example of facilitated diffusion by carrier proteins?

A

the glucose transporter

90
Q

the glucose transporter transports molecules in both directions and is dependent on where

A

[] of glucose is the highest

91
Q

list the steps of the glucose transporter

A
  1. glucose binds to the binding site on the outside of the cell
  2. transporter changes conformations
  3. glucose is released to the inside of the cell
  4. transporter changed to original conformation
92
Q

most ion channels are NOT permanently ___________, but are regulated by ________ that open in response to __________.

A
  • open
  • gates
  • stimuli
93
Q

regulated opening of ion channels mediates transmission of

A

electrical signals

94
Q

what are the 2 types of ion channels?

A
  1. voltage gated
  2. ligand gated
95
Q

voltage gated ion channels open via

A

membrane depolarization

96
Q

ligand gated ion channels open via

A

the binding of a key

97
Q

which type of transport is extremely rapid?

A

facilitated diffusion through ion channels

98
Q

ligand-gated channels open in response to

A

binding of neurotransmitters/ signaling molecules

99
Q

voltage-gated ion channels open in response to

A

changes in electrical potential across the plasma mem.

100
Q

Na+ channels select Na+ atoms that are

A

bound to H2O

101
Q

K+ channels select

A

dehydrated K+ atoms

102
Q

isotonicity relies on

A

total solute concentration

103
Q

________ is pumped out of the cell while _______ is pumped in

A

Na+

K+

104
Q

which ion has the greatest effect on resting membrane potentials? why?

A
  • K+

-b/c some K+ channels remain open

105
Q

Na+ channels are open during which period of the action potential?

A

depolarization

106
Q

what causes hyperpolarization?

A

the increase amount of open K+ channels

107
Q

Ca2+ is stored where?

A

in the ER

108
Q

list the 5 steps in the

A
  1. arrival of action potential
  2. voltage-gated Ca2+ channels open
  3. Ca2+ enters axon terminal causing vesicles to bind to synaptic membrane
  4. neurotransmitter is released into synaptic cleft
  5. neurotransmitter binds to ligand-gated ion channels
  6. post-synaptic membrane gets depolarized
109
Q

what is an example of a unique pore?

A

porins

110
Q

porins cross the membrane as

A

beta-barrel structures

111
Q

porins enclose an

A

aqueous pore

112
Q

porins do NOT allow

A

charged ions to cross

113
Q

which types of porins are only found in some unique tissues?

A

aquaporins

114
Q

aquaporins allow

A

rapid passage of large volumes of H2O

115
Q

aquaporins are found in

A
  • proximal tubules of kidneys
  • erythrocytes
116
Q

what is known as the transport of molecules against their concentration gradient?

A

active transport

117
Q

facilitated diffusion is energetically

A

favorable

118
Q

active transport is energetically

A

unfavorable

119
Q

what are the 3 major functions made possible by active transport?

A
  1. nutrient uptake
  2. substance removal
  3. maintain non-equilibrium intracellular []
120
Q

active transport is based on an

A

energy source

121
Q

active transport is regarded as either

A

direct or indirect

122
Q

direct active transport is aka

A

primary active transport

123
Q

indirect active transport is aka

A

secondary active transport

124
Q

direct active transport is coupled directly to an

A

exergonic chemical reaction

125
Q

indirect active transport depends on the

A

co-transport of 2 solutes

126
Q

describe indirect active transport

A

the movement of a solute down its concentration gradient drives the movement of another solute against its concentrations gradient

127
Q

with indirect active transport one of the solutes is most likely an

A

ion

128
Q

which type of active transport is directly coupled to an exergonic chemical reaction?

A

direct/ primary active transport

129
Q

what is the exergonic chemical reaction that direct active transport is coupled with?

A

hydrolysis of ATP

130
Q

what is the name for the transport proteins that are driven by ATP hydrolysis?

A

ATPases ATPase Pumps

131
Q

the largest family of membrane transporters consists of the

A

ABC transporters (ABC-type ATPases)

132
Q

ABC transporters are characterized by a highly conserved ATP-binding domain known as

A

ATP-binding cassette

133
Q

the Na+/K+ ATPase pump is used to regulate and maintain ________ in the cell

A

isotonicity

134
Q

the Na+/K+ ATPase pump pumps _______ Na+ ____ and _________ K+ ________.

A

3

out

2

in

135
Q

list the 9 steps in the sodium/potassium pump

A
  1. pump open to inside
  2. 3 Na+ bind
  3. ATP phosphorylates causing a conformational change
  4. 3 Na+ expel outside
  5. pump is open to the outside
  6. 2 K+ bind
  7. dephosphorylation causes a conformational change
  8. 2 K+ expel inside
  9. pump returns to original shape
136
Q

the ion gradients that are maintained by Na+/K+ pumps are essential for

A

transmission of action potentials

137
Q

there is a higher concentration of what ion inside the cell?

A

K+

138
Q

there is a higher concentration of which ion outside the cell?

A

Na+ & Cl-

139
Q

what other pump is also powered by ATP hydrolysis?

A

Ca2+ pump

140
Q

Ca2+ is pumped into the

A

ER lumen

141
Q

since Ca2+ is pumped into the ER lumen Ca2+ _______________ concentrations are extremely low

A

intracellular

142
Q

transient increases in cellular Ca2+ are important in

A

cell signaling

143
Q

tonicity is a comparison of

A

2 aqueous systems

144
Q

tonicity is the measure of the

A

osmotic pressure of 2 solutes separated by a semipermeable membrane

145
Q

tonicity commonly describes a

A

response of cells immersed in solution

146
Q

like osmotic pressure, tonicity is influenced by only

A

solutes that CANNOT cross the membrane

- b/c these exert an osmotic pressure

147
Q

why do solutes that can freely cross the membrane NOT affect tonicity?

A

b/c there will always be an equal concentration on both sides of the membrane

148
Q

osmotic pressure is the pressure that must be applied to a solution to prevent the

A

inward flow of H2O across a semipermeable membrane

149
Q

osmolarity (tonicity) is a term used to describe the concentration of a solute in terms of the

A

osmotic pressure it can exert

150
Q

the Na+/K+ pump plays a crucial role in regulating

A

cell volume & maintaining osmolarity

151
Q

what are the 3 sources of intracellular osmolarity?

A
  1. macromolecules
  2. small inorganic molecules
  3. small inorganic ions
152
Q

macromolecules contribute little to osmolarity b/c

A

they count as a single molecule

153
Q

macromolecules are highly charged and attract many

A

inorganic ions of the opposite charge

154
Q

b/c most small inorganic molecules are charged they attract

A

counterions

155
Q

examples of small organic molecules include

A

sugars, amino acids, nucleotides

156
Q

small inorganic ions leak

A

slowly across membrane into the cell

157
Q

small inorganic ions are attracted to

A
  • macromolecules
  • small organic molecules
158
Q

why does water tend to move in the direction of the cell cytoplasm?

A
  • b/c of the intracellular sources of osmolarity
159
Q

the Na+/K+ pump increases external osmolarity by

A

pumping out excess Na+

160
Q

ABC transporters transport in

A

1 direction

161
Q

in bacteria ABC transporters are used to drive the ______________ of _____________.

A

import

nutrients

162
Q

in eukaryotes ABC transporters are used to transport toxic substances _____________ of the cell

A

out

163
Q

ABC transporters can be problematic in the

A

delivery of chemotherapeutics

164
Q

ATP phosphorylation causes the ABC transporters to be open to the

A

outside of the cell

165
Q

mutations affecting ABC transporters are the molecular cause of

A

cystic fibrosis

166
Q

CFTR stands for

A

cystic fibrosis transmembrane-conductance regulator

167
Q

lack of function of Cl- channel results in the

A

accumulation of mucus in the respiratory & digestive tracks

168
Q

indirect active transport is aka

A

secondary active transport

169
Q

describe indirect active transport

A

the transport of 2 solutes
- one w/ its concentration gradient
- one against its concentration gradient

170
Q

what is an example of a transporter that transports molecules in an indirect active transport manner?

A

the Na+/glucose transporter

171
Q

describe the indirect active transport mechanism of the Na+/glucose transporter

A

the downward flow of Na+ provides enough energy to take up glucose and create high intracellular glucose concentrations

172
Q

list the 6 steps in the active transport of glucose

A
  1. pump open outside
  2. Na+ ion binds (stimulating glucose binding)
  3. conformational change
  4. pump opens to inside
  5. Na+ is released inside
  6. glucose is released inside
  7. pump returns to original position
173
Q

with the Na+/ glucose pump how does the Na+ that’s transported into the cell return to the outside of the cell?

A

by the Na+/K+ pump

174
Q

explain the transport of glucose in the intestines

A
  • active transport takes glucose to the apical surface of the intestinal epithelial
  • glucose is then transferred to connective tissue and blood via facilitated diffusion
175
Q

the transport of glucose in the intestines is driven by the

A

N+/K+ pump

176
Q

what 4 types of transport are seen in erythrocytes?

A
  • simple diffusion
  • facilitated diffusion by carrier proteins
  • facilitated diffusion by channel proteins
  • active transport
177
Q

describe the simple diffusion that is seen in erythrocytes?

A

cellular respiration: diffusion of O2 & CO2

178
Q

describe the facilitated diffusion by carrier proteins that is seen in erythrocytes?

A

-glucose
- Cl- and HCO3- by anion exchange protein

179
Q

describe the facilitated diffusion by channel proteins that is seen in erythrocytes?

A
  • aquaporins
180
Q

describe the active transport that is seen in erythrocytes?

A

Na+/K+ pump driven by ATP hydrolysis

Cell Biology (12 decks)

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