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Biology > Chapter 5: Structure and Function of Plasma Membranes > Flashcards

Chapter 5: Structure and Function of Plasma Membranes Flashcards

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1
Q

How thick are plasma membranes?

A

5 to 10 nanometers

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2
Q

What are the principle components of the plasma membrane?

A

Lipids, proteins and carbohydrates attached to some lipids and proteins

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3
Q

What two lipids are in the plasma membrane?

A

Phospholipids and cholesterol

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4
Q

What is the protein, lipid and carbohydrate ratio in a typical human cell?

A

50:40:10

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5
Q

glycoprotein

A

proteins with carbohydrates attached to them

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6
Q

glycolipid

A

lipids with carbohydrates attached to them

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7
Q

Where are all carbohydrates in the plasma membrane?

A

Attached to lipids or proteins on the exterior surface

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8
Q

amphiphilic

A

describes a molecule with both a polar and nonpolar area

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9
Q

Which part of a phospholipid is charged?

A

The phosphate head

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10
Q

What charge does the phosphate head in a phospholipid have?

A

A negative charge

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11
Q

Which part of a phospholipid is nonpolar?

A

The fatty acids

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12
Q

micelle

A

spherical structure that phospholipids spontaneously form in water where all the phosphate head face outwards

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13
Q

liposome

A

spherical structure that phospholipids form in water where lipid bilayer forms

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14
Q

integral protein

A

proteins that are fully integrated into the plasma membrane

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15
Q

single-pass integral protein

A

proteins that only span the membrane once

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16
Q

multi-pass integral protein

A

proteins that span the membrane several times

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17
Q

How many protein segments can multi-pass integral proteins have?

A

Up to twelve segments

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18
Q

Which protein structure can span the membrane multiple times?

A

Proteins with alpha-helices

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19
Q

transmembrane integral protein

A

integral protein that reaches both sides of the plasma membrane

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20
Q

monotopic intergral protein

A

integral protein that are attached to only one side of the plasma membrane and do not reach both sides

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21
Q

peripheral protein

A

proteins loosely attached to integral proteins or phospholipids

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22
Q

How many monosaccharide units does a typical carbohydrate attached to the plasma membrane have?

A

2-60 monosaccharide units

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23
Q

What structures can carbohydrates attached to the plasma membrane be in?

A

Straight or branched

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24
Q

Which components of the plasma membrane help in cell identification?

A

Peripheral proteins and carbohydrates

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25
Q

Why is cell identification important?

A

It allows cell to differentiate from the body’s own cells and foreign cells

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26
Q

glycocalyx

A

the collective name for all carbohydrates attached to the plasma membrane

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27
Q

Is the glycocalyx hydrophilic or hydrophobic?

A

It is highly hydrophilic

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28
Q

How does the glycocalyx’s hydrophilic properties help the cell?

A

It attracts large amounts of water to the cell to aid in the cell’s interaction with the water

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29
Q

Which two factors affect the plasma membrane’s fluidity?

A

Unsaturated phospholipids and cholesterol

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30
Q

How do unsaturated phospholipids aid in the plasma membrane’s fluidity?

A

Due to the kink in unsaturated fatty acids, when it is cold and phospholipids pack together, space creaked by the kinks allows more fluidity

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31
Q

How does cholesterol aid in the plasma membrane’s fluidity?

A

It decreases the effects of temperature on the membrane

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32
Q

Where is cholesterol found in the plasma membrane?

A

Inside the phospholipid bilayer

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33
Q

selectively permeable

A

describes a membrane that allows only some substances to pass through it

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34
Q

Is the plasma membrane selectively permeable?

A

Yes

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35
Q

passive transport

A

naturally occurring movement of materials across membrane due to differences in concentration

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36
Q

concentration gradient

A

area of high concentration that is adjacent to an area of low concentration

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37
Q

Is the plasma membrane symmetric?

A

No, the interior and exterior sides are different

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38
Q

Which type of molecules can pass through the plasma membrane easily?

A

Nonpolar and lipid-soluble molecules

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39
Q

Which types of molecules cannot pass through the plasma membrane easily?

A

Polar molecules

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40
Q

diffusion

A

process of passive transport where substances in a high concentration move to a low concentration

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41
Q

facilitated transport

A

diffusion of materials with the help of membrane proteins

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42
Q

Why is facilitated transport necessary for ions?

A

Since ions are polar they will be repelled from the hydrophobic parts of the plasma membrane

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43
Q

transport protein

A

integral proteins involved in facilitated transportation of molecules across the plasma membrane

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44
Q

channel protein

A

protein that creates a channel for ions to pass through

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45
Q

What property do channel proteins have that allow for facilitated transport?

A

They are hydrophilic and this provides a hydrated opening for ions to pass through

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46
Q

aquaporin

A

channel protein that allows water through the plasma membrane at a high rate

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47
Q

What two forms can channel proteins be in?

A

They can be open at all times or they are gated

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48
Q

What does it mean for a channel protein to be ‘gated’?

A

It controls the opening and closing of its channel

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49
Q

carrier protein

A

transport protein that changes shape when it binds a substance to transport that substance

50
Q

How selective are carrier proteins?

A

They are specific for only one substance

51
Q

ligand

A

molecule that binds to another

52
Q

Why can carrier proteins’ selectivity be a problem sometimes?

A

Since there are a limited number of carrier proteins for each substance, there is a limit to the rate of transportation regardless of the concentration gradient and not enough materials might be transported

53
Q

Which membrane transport protein works faster?

A

Channel proteins work faster

54
Q

osmosis

A

movement of water across a semipermeable membrane due to water’s concentration gradient

55
Q

tonicity

A

describes how the concentration of solute in a solution can affect osmosis

56
Q

osmolarity

A

describes a solution’s solute concentration

57
Q

What does having a higher osmolarity mean?

A

The solution has fewer water molecules compared to solute

58
Q

What does having a lower osmolarity mean?

A

The solution has more water molecules compared to solute

59
Q

hypotonic

A

when the extracellular fluid has a lower osmolarity than the fluid inside the cell

60
Q

hypertonic

A

when the extracellular fluid has a higher osmolarity than the fluid inside the cell

61
Q

isotonic

A

when the extracellular fluid has the same osmolarity as the fluid inside the cell

62
Q

What happens to red blood cells in a hypertonic solution?

A

Water leaves the cell and shrivels up

63
Q

What happens to cells in a hypotonic solution?

A

Water enters the cell and may burst

64
Q

lysis

A

destruction of a cell due to damage to the cell membrane by excessive water

65
Q

crenation

A

destruction of a cell due to damage to the cell membrane when too much water leaves the cell

66
Q

What happens to a red blood cell during lysis?

A

The spaces between the phospholipids and proteins becomes too large and the cell breaks apart

67
Q

What happens to a red blood cell during crenation?

A

The solutes in water is left behind in the cell which makes the cytosol denser and prevents diffusion, causing the cell to lose function

68
Q

osmoregulation

A

mechanisms that cells use to prevent the effects to osmosis

69
Q

turgor pressure

A

force inside a cell that pushes the cell membrane against the cell wall

70
Q

How do plant cells combat osmotic efffects?

A

The cell wall prevents the cell membrane from expanding too much

71
Q

Do plant cells have a higher or lower osmolarity than its cellular environment?

A

Plant cells’ cytoplasm is always slightly hypertonic

72
Q

plasmolysis

A

when the cell membrane detaches from the cell wall due to osmotic effects when water leaves the cell

73
Q

What happens when plants are not watered?

A

They lose turgor pressure and start to wilt

74
Q

contractile vacuole

A

vesicle that collects and pumps out excessive water to prevent lysis in a hypotonic environment

75
Q

active transport

A

transport of materials across the membrane that requires the cell’s energy

76
Q

Where does the cell get its energy in active transport?

A

Usually from ATP

77
Q

electrical gradient

A

a difference in charge across the plasma membrane

78
Q

Is the inside of a cell positively or negatively charged?

A

Negatively

79
Q

Do cells have a higher or lower concentration of K+ compared to its environment?

A

Cells have a higher concentration of K+

80
Q

Do cells have a higher or lower concentration of Na+ compared to its environment?

A

Cells have a lower concentration of Na+

81
Q

electrochemical gradient

A

the combined concentration and electrical gradients affecting an ion

82
Q

What is the electrochemical gradient for K+ in cells?

A

The concentration gradient drives K+ out of the cell but the electrical gradient drives K+ into the cell

83
Q

What is the electrochemical gradient for Na+ in cells?

A

The concentration gradient drives Na+ into the cell and the electrical gradient also drives Na+ into the cell

84
Q

active transport pump

A

mechanism that actively transports substances against its electrochemical gradient

85
Q

What are the three types of transport proteins?

A

Uniporters, symporters and antiporters

86
Q

uniporter

A

transport protein that carries only one specific molecule

87
Q

symporter

A

transport protein that carries two different molecules in the same direction

88
Q

antiporter

A

transport protein that carries two different molecules but in opposite directions

89
Q

primary active transport

A

moves ions across the plasma membrane by using ATP directly

90
Q

secondary active transport

A

moves ions across the plasma membrane as a result of the electrochemical gradient caused by primary active transport

91
Q

Na+-K+ ATPase

A

sodium-potassium pump

92
Q

sodium-potassium pump

A

maintains the electrochemical gradient and the correct concentrations of K+ and Na+ in cells

93
Q

In which direction does the sodium-potassium pump move K+ and Na+?

A

K+ is moved into the cell and Na+ is moved out of the cell

94
Q

How many Na+ are moved for every K+?

A

For every three Na+ moved out of the cell, two K+ are moved into the cell

95
Q

What are the two forms a sodium-potassium pump can be in?

A

It can be oriented to the cell’s interior or exterior

96
Q

What happens when the sodium-potassium pump is oriented towards the cell’s interior?

A

The carrier has a high affinity for Na+ and these ions bind to the protein

97
Q

How is Na+ pumped out of the cell?

A

When Na+ attaches to the pump, the pump hydrolyses ATP and a phosphate group attaches to it, changing the pumps shape and reorienting outwards and releasing the Na+

98
Q

What happens when the sodium-potassium pump is oriented towards the cell’s exterior?

A

The carrier has a high affinity for K+ and these ions bind to the protein

99
Q

How is K+ pumped into the cell?

A

When K+ attaches to the pump, the phosphate group from the previously hydrolysed ATP detaches and the pump orients itself to the interior, releasing the K+

100
Q

electrogenic pump

A

pump that creates a difference in charge across the membrane

101
Q

What happens as a result of primary active transport?

A

Since more Na+ is being pumped out of the cell than K+ into the cell, the cell’s interior becomes negatively charged

102
Q

How does secondary active transport work?

A

Due to excessive Na+ outside the cell from primary active transport, an electrochemical gradient is created and Na+ are driven inside the cell through channel proteins

103
Q

What does secondary active transport move across the membrane?

A

Na+ is moved into the cell, along with other substances like glucose and some amino acids

104
Q

bulk transport

A

transport of large macromolecules through the cell membrane

105
Q

endocytosis

A

type of active transport where the cell membrane invaginates
and forms a pocket around its target, pinching the pocket off into a vesicle inside the cell

106
Q

phagocytosis

A

when a cell takes in a large particle by surrounding the target and engulfing it

107
Q

clathrin

A

protein that helps form coated vesicles in endocytosis

108
Q

How does clathrin help in endocytosis?

A

It coats a portion of the inner cell membrane in preparation to stabilise the vesicle formed by endocytosis and disengages before the vesicle merges with a lysosome

109
Q

endosome

A

organelle of a fused vesicle and lysosome

110
Q

pinocytosis

A

when a cell takes in molecules along with the water that surrounds it by surrounding and engulfing it

111
Q

What are the differences between phagocytosis and pinocytosis?

A
  1. Phagocytosis engulfs a large molecule as if eating it and pinocytosis drinks the water and the particles inside of the water
  2. Vesicles in phagocytosis are a lot larger
  3. Vesicles in pinocytosis do not need to fuse with a lysosome
112
Q

potocytosis

A

a variation of pinocytosis

113
Q

caveolin

A

coating protein that plays a role, similar to clathrin, in potocytosis

114
Q

lipid raft

A

special part of lipid bilayer that contains more glycosphingolipids and receptor proteins

115
Q

caveola

A

specialised vesicle made up of lipid rafts and coated with caveolin that is the main transport vesicle in potocytosis

116
Q

receptor-mediated endocytosis

A

when a cell takes in specific materials with the help of receptor proteins

117
Q

What is the difference between phagocytosis and receptor-mediated endocytosis?

A

Normal phagocytosis involves eating any macromolecules, but receptor-mediated endocytosis uses receptor proteins to bind to certain substances

118
Q

Does receptor-mediated endocytosis only allow certain substances to enter?

A

No, sometimes other substances may gain entry at the same site

119
Q

exocytosis

A

process of removing materials from the cell

120
Q

How does exocytosis work?

A

Vesicles containing waste materials in the cell fuse with the plasma membrane and open up to release the waste

Biology (9 decks)

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