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Biology > Module 2.1.5 - plasma membranes > Flashcards

Module 2.1.5 - plasma membranes Flashcards

1
Q

What are the general roles of membranes?

A
  • separating cell contents from external environment
  • cell recognition and signalling via receptors
  • separating cell components from cytoplasm
  • holding components of the same metabolic pathways in place
  • regulating transport of materials in or out of cells
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2
Q

What is the phospholipid bilayer?

A
  • consists of 2 layers of phospholipids, one being the hydrophobic interior and a hydrophilic exterior
  • hydrophilic head group and hydrophobic tails (fatty acid chains) are depicted in the single phospholipid molecule
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3
Q

What molecules can and can’t diffuse through the phospholipid bilayer?

A

Small and fat soluble molecules can diffuse through
large, charged and fat insoluble molecules can’t diffuse through so require membrane proteins

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4
Q

What are polar molecules?

A
  • partially charged
  • fat insoluble
    hydrophilic
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5
Q

What are non-polar molecules?

A
  • uncharged
  • soluble in fats
  • hydrophobic
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6
Q

What is the fluid mosaic model?

A

States membranes are composed of a phospholipid bilayer with various protein molecules floating around within it

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7
Q

What does the lipid bilayer contain?

A

lipid molecules which have their hydrophilic heads in contact with the watery exterior
e.g. cytoplasm

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8
Q

What do hydrophilic phosphate heads form?

A

They form hydrogen bonds with water molecules

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9
Q

Where are hydrophobic tail regions in the fluid mosaic model?

A

In the centre of the membrane, away from the water

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10
Q

What membrane do intrinsic proteins have?

A

transmembrane

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11
Q

What are the 2 types of intrinsic proteins?

A

Channel proteins - act as passageways to allow ions with electrical charges to pass through
Carrier proteins - can change shape to allow specific molecules across

Some proteins (glycoproteins) are attached to carrier proteins and act as enzymes, antigens or receptor sites for chemicals, such as hormones

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12
Q

What are extrinsic proteins?

A
  • serve in transport of molecules and as receptors
  • present in one side of the bilayer
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13
Q

What are glycoproteins?

A
  • proteins that contain covalently attached sugar residues
  • role in cell adhesion and as receptors for signalling
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14
Q

What does the receptor binding do in glycoproteins?

A

Triggers a direct response or a cascade of events inside the cell
e.g. receptors for insulin and glucagon are glycoproteins

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15
Q

What are glycolipids?

A

Lipids with a carbohydrate attached by a glyosidic bond

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16
Q

What is the role of glycolipids?

A

to maintain stability of the cell membrane n to facilitate cellular recognition (antigens) which is crucial to the immune response and in the connections that allow cells to connect to one another to form tissues

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17
Q

How is glycocalyx formed?

A

from the carbohydrate chains attached to lipids (glycolipids) or proteins (glycoproteins) in the membrane

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18
Q

What is glycocalyx?

A

‘sugar coat’

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19
Q

What is cholesterol?

A
  • type of lipid/fat
  • has a hydrophilic end and a hydrophobic end
  • regulates fluidity and stability of the membrane
  • helps the membrane resist temperature changes
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20
Q

What does the folded inner membrane of the mitochondria (cristae) create?

A

A large surface area for aerobic respiration
Enzymes requires are localised in the cristae

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21
Q

Where do light dependent reactions occur?

A

Thylakoid membranes in chloroplasts which is part of the inner membrane containing chlorophyll

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22
Q

What do digestive enzymes on the plasma membrane of epithelial cells of the small intestine do?

A

Catalyse some of the final stages of the breakdown of certain types of sugars

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23
Q

What do membranes control?

A

The passage of different substances in and out of cells (and organelles)

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24
Q

What is vital to selective permeability?

A

Membrane integrity

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25
Q

What 4 factors effect membrane permeability?

A
  • temperature
  • proportion of cholesterol
  • proportion of saturated and unsaturated fats
  • presence of solvents
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26
Q

How does temperature effect membrane permeability?

A
  • phospholipid molecules constantly moving
  • increase temp means increase in KE of phospholipids so more fluidity
  • more fluidity = less membrane integrity
  • excessive temp = membrane disintegrates completely
  • proteins are less stable than phospholipids
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27
Q

How does cholesterol effect membrane permeability?

A
  • buffers the effect of lowered temperatures to prevent a reduction in the membrane’s fluidity
  • prevents phospholipid molecules from packing together too closely
  • reduces membrane fluidity at moderate temperatures
  • low temperatures, hinders them
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28
Q

How do unsaturated and saturated fats effect membrane permeability?

A
  • unsaturated hydrocarbon tails with kinks are better in cold temperatures = have a double covalent bond
  • saturated hydrocarbon tails have no kinks so better in warm temperatures = have single covalent bonds
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29
Q

How do solvents effect membrane permeability?

A
  • dissolve membranes, disrupting cells
  • rationale behind ethanol use in antiseptic
  • very strong alcohol solution = toxic
  • less concentrated alcoholic solutions = don’t dissolve membranes, still cause damage
  • ethanol = non polar, diffuses across lipid bilayer and through channel proteins, disrupting membrane structure = increasing permeability
  • disrupted neuronal membranes = disrupted nerve impulses = lack of coordination/slower reaction time associated with drunkenness
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30
Q

What buffers to lower the temperature?

A

Cholesterol

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31
Q

What do unsaturated hydrocarbon tails do?

A

Have kinks so work better in low temperatures a the tails allow diffusion to happen even though there is low energy levels

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32
Q

What do saturated hydrocarbon tails do?

A

Have no kinks so diffusion still happens quickly as there is high energy levels from the high temperatures

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33
Q

What is diffusion?

A

The NET movement of particles from a high concentration to a low concentration, down the concentration gradient

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34
Q

What do molecules posses as they move randomly?

A

kinetic energy

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35
Q

The steeper the concentration the…

A

Higher diffusion rate

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36
Q

What are the 2 types of diffusion?

A

simple and facilitated diffusion

37
Q

What is simple diffusion?

A
  • Molecules pass through the membrane unassisted
  • down the concentration gradient
  • no proteins are involved
  • some molecules pass straight through the membrane
  • molecules are small and soluble in lipids so can pass through lipids in the membrane
  • a passive process, no energy required
38
Q

What are water molecules?

A

Polar and lipid insoluble

39
Q

When can direct diffusion happen?

A

If there’s high levels of water molecules

40
Q

What do some membranes use?

A

Aquaporin channels (special water channel proteins to allow water molecules to move across the membrane. This is a form of facilitated diffusion)

41
Q

What happens in the alveoli?

A

oxygen diffuses into the blood from an area of high to low concentration

42
Q

What is pumped away to the cell in the blood capillaries?

A

Oxygen, which maintains the concentration gradient

43
Q

What happens in the cells?

A

Oxygen diffuses into the cytoplasm and then into the mitochondria for aerobic respiration, constantly lowering the oxygen conc inside the cell, maintaining conc gradient

44
Q

What is facilitated diffusion?

A
  • specific proteins carriers or protein channels in the cell membrane are needed to transport molecules
  • ions are insoluble in the lipid bilayer due to hydrophobic tails
  • these molecules diffuse through protein channels or pores in the membrane down the conc gradient
  • doesn’t require energy
45
Q

What are carrier proteins?

A
  • transmembrane proteins in the membrane called carrier proteins bind with specific molecules, which opens the protein to allow molecules to cross the membrane
  • have a specific shape, normally carrying 1 specific shaped molecule
46
Q

What factors effect diffusion?

A
  • temperature
  • diffusion distance
  • surface area
  • size of diffusing molecule
  • concentration gradient
47
Q

Why does temperature effect diffusion?

A

high temp - quicker diffusion as more diffusion
low temp - slower diffusion as less energy

48
Q

Why does diffusion distance effect diffusion?

A

bigger distance - slower diffusion
small diffusion - quicker diffusion

49
Q

Why does surface area effect diffusion?

A

large SA - quicker diffusion
small SA - slower diffusion

50
Q

Why does size of diffusing molecule effect diffusion?

A

bigger molecules take longer to diffuse
smaller molecules are quicker to diffuse

51
Q

Why does concentration gradient effect diffusion?

A

steep concentration - faster diffusion
not steep - slower diffusion

52
Q

What is active transport?

A

The net movement of particles from an area of low concentration to high concentration, against the concentration gradient

53
Q

What does active transport require?

A
  • Energy/ATP
  • carrier proteins
54
Q

Why do cells need a large amount of ATP in active transport?

A

kinetic energy isn’t enough

55
Q

What is often transported by active transport?

A

Ions

56
Q

Why are carrier proteins required in active transport?

A

To transport a substance with a specific shape to the carrier protein against the concentration gradient

57
Q

What do root hair cells use to absorb minerals from the soil?

A

Active transport

58
Q

What doe root hair cells absorb through active transport?

A

Minerals from the soil

59
Q

What is the equation for active transport?

A

ATP + H2O -> ADP +P + energy

60
Q

What are the 2 types of cytosis?

A
  • exocytosis
  • endocytosis
61
Q

How is cytosis possible?

A

The fluid nature of the cell surface membrane

62
Q

What is the process of endocytosis?

A
  • takes substance into cell
  • cell surface membrane infolds (invaginates) round the substance outside the cell to form a vesicle
  • vesicle enters the cell and membrane reforms
  • ATP provides energy to form vesicles and move them using motor proteins along the cytoskeleton microtubules
63
Q

What is the process of exocytosis?

A
  • solids or liquids leave the cell when vesicles fuse with the cell membrane
  • contain isolated substances in vesicles
  • vesicles move towards the cell surface membrane and fuses with it, enabling the contents of the vesicle to leave the cell
  • the membrane then reforms
64
Q

What are the 2 types of endocytosis?

A
  • Phagocytosis
  • Pinocytosis
65
Q

What is phagocytosis?

A

cell eating, vesicle traps solids or food substances to be taken into cell

66
Q

What is pinocytosis?

A

Cell drinking, vesicles traps liquid to go into the cell

67
Q

What is osmosis?

A

The movement of water molecules across a partially permeable membrane from a region of high water potential to a region of lower water potential, with the water potential gradient

68
Q

What is the water potential of a solution a measure of?

A

How much water the solution contains in relation to other substances and how much pressure it exerts on the membrane/container

69
Q

What does a solution containing a lot of water have?

A

A higher water potential, exerting some pressure

70
Q

What does a solution containing a lot of dissolved solutes have?

A

A lower water potential, exerting less pressure

71
Q

What is the units and symbol for water potential?

A

Units = Pa/ KPa
Symbol = ψ (Psi)

72
Q

What does water potential quantify?

A

The tendency of water to diffuse from one area to another sue to osmosis

73
Q

What is the highest water potential you can have?

A

0 Pa

74
Q

What type of water has the highest water potential?

A

Pure/distilled as it contains no dissolves solutes

75
Q

What is a isotonic solution?

A

Contains the same amount of solutes and and has the same water potential as a cell suspended in the solution

76
Q

What does hyper mean?

A

High, over, excess

77
Q

What does hypo mean?

A

Low, under, beneath

78
Q

What does a hypertonic solution contain?

A

More solutes

79
Q

What does a hypotonic solution contain?

A

Less solutes

80
Q

What type of water potential do hypertonic solutions have?

A

Lower water potential than a cell suspended in the solution

81
Q

What type of water potential do hypotonic solutions have?

A

Higher water potential than a cell suspended in the solution

82
Q

What does crenation mean?

A

Cell shrinkage

83
Q

What does plasmolysis mean?

A

Membrane pulls away from cell wall as cytoplasm shrinking due to plant cell being in a hypertonic solution

84
Q

What does placing an animal cell in a solution of low water potential mean?

A

An osmotic water potential gradient is established (high inside cell and low outside cell), water moves down the water potential gradient

85
Q

What does cytolysis mean?

A

Cell swells and bursts as the membrane breaks when in a hypotonic solution

86
Q

What does haemolysis mean?

A

Red blood cell bursts in a hypotonic solution

87
Q

What does turgid mean?

A

Plant cell swells but doesn’t burst in a hypotonic solution, increasing turgid pressure

88
Q

What’s the difference between plant and animal cells when they are in a hypotonic solution?

A

Plant cells swell/become turgid due to having a cell surface membrane and cell wall
Animal cells burst as they only have a cell surface membrane

Biology (10 decks)

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