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cell bio part 2 > Membrane Structure and Transport > Flashcards

Membrane Structure and Transport Flashcards

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Biology 101 flashcards
1
Q

All membranes of bacteria and eukaryotes are constructed of what?

A

Phospholipid bilayer

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2
Q

Membranes also contain various….

A

Proteins

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3
Q

Where are the proteins found in membranes

A

Inner surface, outer surface, some span the entire membrane

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4
Q

Where are the proteins in the membranes made

A

Made along cytosolic side of endoplasmic reticulum in eukaryotes

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5
Q

What are the most abundant membrane lipids

A

Phospholipids

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6
Q

Phospholipids are

A

Amphipathic

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7
Q

What are that characteristics of phospholipids

A

have a polar, hydrophilic head that contains a phosphate group, and have two nonpolar, hydrophobic hydrocarbon tails

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8
Q

Cholesterol and other types of what are common

A

lipids

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9
Q

Cholesterol and lipids lack what but have other charged groups

A

phosphate

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10
Q

Cholesterol and lipids alter membrane fluidity for organisms but particularly those living where

A

In extreme temperatures

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11
Q

All membranes are what

A

Selective barriers

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12
Q

plasma membranes surround the what of all cells

A

the cytoplasm

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13
Q

Eukaryotes have additional what around their organelles

A

cell membranes

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14
Q

with a “sheet” orientation, the edges of the lipids would interact with

A

the water

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15
Q

What is the most energetically favorable shape for the bilayer to form

A

a sphere

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16
Q

In water, pure phospholipids spontaneously form a….

A

Liposome

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17
Q

Phospholipids rapidly spin and laterally traverse their monolayers, but mostly need what to switch sides

A

Enzymes

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18
Q

What two things switch phospholipids across monolayers

A

Scramblase (ER) and flippase (Golgi)

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19
Q

The fluidity of a membrane depends on what

A

The types of lipids present

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20
Q

Saturated fats have no what

A

No double bonds (pack together better)

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21
Q

Unsaturated fats have what

A

At least 1 double bond that causes a kink (don’t pack together well)

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22
Q

Regions of a membrane can be made more or less fluid based on

A

The types of lipids present

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23
Q

Higher amounts of saturated fatty acids decrease what

A

Membrane fluidity and create “lipid rafts”

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24
Q

Higher amounts of what correlate with high temperature adaptation/plasticity in certain animals

A

Cholesterol

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25
Q

Protein structure allows part of the protein to interact with lipids with the other part is what

A

Hydrophilic and forms a path for polar molecules to move through

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26
Q

hydrophilic residues are indicated by what

A

red center, left

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27
Q

hydrophobic residues are indicated by what

A

green edges, left

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28
Q

Transmembrane proteins provide what in the membrane

A

“Gates”

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29
Q

Type “D” membrane proteins can be separated by what

A

Mild detergents

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30
Q

What is the cell cortex

A

The cell cortex in a meshwork of filamentous proteins that provide structure and support to animal cells

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31
Q

Proteins that are inserted into the membrane attach to what

A

They attach to proteins that span the inner surface of the membrane to provide structural support

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32
Q

Do plant cells need a cell cortex?

A

No

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33
Q

Proteins embedded in lipid membranes using what type of domain

A

Alpha - helical

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34
Q

Hydrophobic amino acids on the outside of the helix interact with what

A

Lipids

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35
Q

The polar backbone of a polypeptide makes up the inner portion of what

A

the helix

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36
Q

Cell surfaces are frequently coated with what?

A

Carbohydrates

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37
Q

What is it called when carbohydrates link to proteins

A

Glycoproteins

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38
Q

What is it called when long polysaccharides link to proteins

A

Proteoglycans

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39
Q

What is it called when carbohydrates are on lipids

A

Glycolipids

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40
Q

Glycocalyx =

A

all CHO’s on a cell

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41
Q

What is glycocalyx dependent on

A

Flippase dependent in the case of glycolipids

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42
Q

Membrane carbohydrates are related to many functions including…

A

Protection, Adhesion, Cellular identity (ABO blood type)

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43
Q

What is permeability

A

The ability to allow solids or gasses to cross the membrane

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44
Q

Lipid bilayers are

A

Semipermeable

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45
Q

The smaller and more hydrophobic the molecule, the easier what

A

it moves across it

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46
Q

The lipid membrane may restrict movement of what

A

Nutrients or wastes

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47
Q

Lipid membrane permeability allows concentrations gradients to form and can set up what

A

Stored energy for later conversion

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48
Q

A cell must balance water levels to maintain what

A

Concentrations of solutes

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49
Q

Water movement across a membrane occurs through what?

A

Aquaporins

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50
Q

All cells have aquaporins to allow what

A

The movement of water across membranes

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51
Q

What is diffusion

A

The movement of a substance across a membrane from high to low concentration

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52
Q

What is diffusion related to?

A

Entropy and random distribution

53
Q

Movement across ions is what type of energy

A

Kinetic energy

54
Q

Having a concentration gradient is what type of energy

A

Potential

55
Q

What is osmosis?

A

The movement of water across a membrane from high to low concentration OF THE WATER

56
Q

In osmosis, water moves from an area of low solute concentration to what

A

An area of high solute concentration

57
Q

Osmosis is related to what

A

Entropy and random distribution

58
Q

In uncharged molecules what determines the movement direction

A

Concentration gradient

59
Q

What determines the movement direction in ions (charged molecules)

A

concentration gradient and electrochemical gradient

60
Q

Organic compounds including DNA, RNA and amino acids have what charge

A

Negative charge

61
Q

Most cations are at higher concentrations where

A

Outside the cell

62
Q

Also high concentrations of phosphates and what in cells

A

Phosphates and phospholipids

63
Q

Na + may leak back into the cell, but K+ usually does or doesn’t?

A

K+ usually doesn’t leak out of cells

64
Q

What is membrane potential measured in?

A

Millivolts

65
Q

Polar and charged substances that do not readily cross a lipid bilayer are transported by what?

A

Membrane proteins

66
Q

What do channels do?

A

Allow movement based on size and charge; may allow movement of more than one chemical

67
Q

Movement across a membrane can be

A

passive (diffusion) or active (energy required)

68
Q

What is passive transport

A

movement of a substance down a gradient

69
Q

Passive transport is what type of movement

A

Energetically favorable (releases energy)

70
Q

What is active transport

A

Uses energy to move solutes against a gradient

71
Q

Active transport is what type of movement

A

Energetically unfavorable because it needs energy put in / needs to be coupled

72
Q

What are the two types of active transport?

A

Primary and secondary

73
Q

What is primary active transport

A

Uses ATP or light directly

74
Q

What is secondary transport

A

Converts stored energy (ATP was needed previously) by exploiting gradient concentrations

75
Q

Transporters mostly move small organic compounds, but also some what?

A

Inorganic ions

76
Q

Are transporters specific?

A

Yes, highly specific

77
Q

Different membranes in a cell have the same or different transporters present?

A

Different

78
Q

Are transporters active or passive?

A

Both

79
Q

Na+/K+ ATPase Pump

A

Uses ATP directly, 3 Na+ are pumped out, and 2K+ are pumped in, keeps [Na+] high outside and [K+] high inside

80
Q

Na+ Glucose Symporter

A

Couple movement of a solute in the same direction as the Na+ concentration gradient

81
Q

Na+ Glucose Symporter is important for what

A

Digestive function

82
Q

Glucose always moves into what type of cells, even if the cell has higher concentration than the __________.

A

Gut cells

83
Q

Na+/H+ Antiporter

A

Couple movement of H+ in the opposite direction as the Na+ and is regulated by hormones in distal kidneys

84
Q

Proton H+ gradients

A

H+ gradients are used as an energy source for ATP synthesis and symports

85
Q

Cells use multiple gradients as energy sources which means what

A

ATP and activated carriers (NADH, etc.) are not the only sources of energy

86
Q

Both types of transport are. mediated by what

A

Proteins

87
Q

Active transporters are commonly called what?

A

Pumps

88
Q

Some ion channels are selective where some ions can pass but others cannot, what is that dependent on?

A

Shape, size, and charge

89
Q

Some channels are gated and only do what

A

Open/close

90
Q

Gated channels can be opened or closed based on what?

A

Signals that affect proteins conformation

91
Q

Voltage-gated

A

Responds to a change in resting membrane potential (-70millivolts), many examples from neurons to muscles

92
Q

Ligand-gated

A

Direct specific binding, taste

93
Q

Mechanically-gated

A

“touch receptors”, hearing and balance, venus flytrap prey capture, mimosa pudica leaf closing response

94
Q

Ca2+ ATP-Driven Pump

A

Cells also regulate Ca2+ balance; low the cytosol, higher outside the cell and in the ER

95
Q

Ca2+ have multiple roles in cells related to regulating protein activity which includes

A

Muscle contraction, nerve signaling, fertilization

96
Q

Action potentials in nerve cell signaling

A

Neurons receive and transmit signals

97
Q

What is an action potential

A

The wave of signaling

98
Q

The signal results from changes in what

A

Membrane potential (voltage) across the neurons plasma membrane

99
Q

Neuron dendrites receive signals from other cells and then what happens to the signals?

A

Signals are transmitted along the axon, including membrane potentials, pumps, and voltage-gated channels

100
Q

Nerve terminals interact with dendrites of another neuron to send the signal where?

A

Send the signal to new neurons or a target like skeletal muscle cells

101
Q

What percent of the body’s energy is used by the nervous system, mostly in Na+/K+ pump activity

A

20%

102
Q

Voltage-gated (VG) Na+ channels

A

Activation gate and inactivation gate, at rest activation gate is closed and inactivation gate open, transient influx of Na+ causes the membrane to depolarize

103
Q

Voltage-gated (VG) K+ channels

A

Single activation gate that is closed in the resting state, K+ channel opens slowly, Efflux of K+ repolarizes the membrane

104
Q

At the resting potential, the membranes permeability is determined by what?

A

Its open ion channels

105
Q

Resting phase

A

Equilibrium between diffusion of K+ out of cell and voltage pulling K+ into cell, at rest this is usually -70mV, and K+ leak channels allow a slow leak of K+ in both directions

106
Q

A stimulus generates an electrical signal at or above threshold which is?

A

-55mV

107
Q

Rising phase

A

Stimulus causes a change in voltage at or above the threshold (-55 mV), positively charged ions rush into the cell, charge inside becomes less negative (depolarization), voltage-gated K+ channels are also triggered but are SLOW

108
Q

After a delay, voltage gated K+ channel slow gates open and what happens as a result??

A

Voltage gated Na+ channel inactivation gates close

109
Q

At the top of the curve what is reached

A

Maximum voltage is reached

110
Q

At the top of the curve, there is a rapid shift of what

A

High Na+ permeability and low K+ permeability to high K+ permeability and low Na+ permeability

111
Q

With the voltage-gated K+ channels open, what happens

A

Positive ions rush out of the cell

112
Q

Falling phase

A

Undershoot occurs as excess K+ diffuses out before (VG) K+ channel closes and the charge inside becomes more negative again (hyperpolarizes)

113
Q

Before a new action potential can begin, all voltage-gated channels must reset

A

No new action potentials can occur until this happens (absolute refractory period)

114
Q

Refractory period

A

VG K+ channel slow gate closes
VG Na+ channel activation gate closes
VG Na+ channel inactivation gate opens

115
Q

Once channels are reset, a greater or less then normal depolarization can result a new action potential (relative refractory period)

A

GREATER

116
Q

What do Na+/K+/ATP pumps must do in the refractory period

A

Restore ion gradients

117
Q

APs are self-propagating (change in potential triggers) and also what

A

Undirectional

118
Q

What are the two ways of speeding up electrical propagation?

A

1) Myelination
2) Large diameter

119
Q

Myelination

A

Cellular insulation, “jumps segments”, and saltatory conduction

120
Q

Large diameter

A

Reduces electrical resistance, giant squid “fight or flight” axons

121
Q

Transmitting signals between neurons

A

Electrical signals do not jump from neuron neuron

122
Q

Transmitting signals between neurons

A

There is a synapse (a gap) between the nerve terminal and the dendrites of the next neuron

123
Q

To transmit the signal, neurotransmitters are released from the nerve terminal

A

Ex. acetylcholine

124
Q

Electrical signals help bind to what

A

They bind receptors on the dendrites of the next neuron

125
Q

At the nerve terminal, the action potential causes what to open

A

voltage-gated Ca2+ channels to open

126
Q

After voltage gated Ca2+ channels open, what happens

A

Ca2+ moves into the cell, Higher [Ca2+] causes vesicles containing neurotransmitters to fuse
with the plasma membrane, Neurotransmitters are released into the synapse

127
Q

What are neurotransmitters

A

igands that bind ligand-gated Na+ channels
on dendrites neurons, or similar channels on skeletal muscles

128
Q

The ligand-gated Na+ channels open and allow Na+ to enter the cell, causing what

A

An action potential in that cell, or electrical trigger for contraction.

cell bio part 2 (9 decks)

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