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Biology module 2 > 2.5 Biological membranes > Flashcards

2.5 Biological membranes Flashcards

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1
Q

What does a phospholipid consist of?

A

-Phosphate head (hydrophilic + Polar)
-Fatty acid tail (Hydrophobic + non-polar)

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2
Q

What sort of substances can pass through the phospholipid bilayer?

A

-small substances
-lipid soluble substances

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3
Q

what is the role of membranes at the surface of cells?

A

-seperate cell contents from exterior
-regulate transport of materials
-contains receptors
-contains antigens so organisms immune system doesn’t attack itself
-can release chemicals to signal to other cells

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4
Q

what is the role of membranes within cells?

A

-site for attachment of enzymes
-provide selective permeability
-creation of concentration gradients
-seperates contents of organelles from the cytoplasm
-controls what substances enter/leave organelles

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5
Q

what is the membrane model called?

A

fluid mosaic model

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6
Q

what creates the mosaic pattern?

A

the scattered proteins

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7
Q

what can be found in the membrane?

A

-phospholipids
-integral protein
-protein channel
-carrier protein
-glycocalyx
-cholesterol
-peripheral protein

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8
Q

what is a peripheral protein?

A

-can be an enzyme
-dont span the entire phospholipid bilayer

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9
Q

what is an integral protein?

A

-spans whole bilayer
-receptor
-can be channel/carrier protein

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10
Q

what is a protein channel?

A

-water filled channel
-inside is lined with hydrophilic amino acids
-outside is lined with hydrophobic amino acids

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11
Q

what sort of molecules does the protein channel allow through?

A

charged molecules/ ions

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12
Q

what sort of molecules does the carrier protein allow through?

A

large molecules

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13
Q

what is the glycocalyx?

A

glycolipids and glycoproteins

They are chains of carbohydrates attached to a lipid/protein

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14
Q

what does the glycocalyx do?

A

-act as antigens
-cell signalling
-receptors
-bind to other cells for cell adhesion
-attract water with dissolved solutes

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15
Q

what does cholesterol do?

A

gives mechanical stability and flexibility/fluidity

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16
Q

what is diffusion?

A

movement of molecules from an area of a high concentration to a low concentration

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17
Q

what is simple diffusion?

A

when molecules move freely and randomly due to kinetic energy

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18
Q

describe examples of molecules that can pass through simple diffusion

A

oxygen
carbon dioxide

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19
Q

what are factors which affect the rate of diffusion?

A

-temperature
-diffusion distance
-surface area
-size of diffusing molecule
-concentration gradient

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20
Q

how can the concentration gradient be maintained?

A

molecules entering cells pass into organelles and are used for metabolic reactions

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21
Q

Describe examples of molecules entering cells into organelles and being used for metabolic reactions

A

oxygen in the cytoplasm of respiring cells then into mitochondria from aerobic respiration

22
Q

what is facilitated diffusion?

A

movement of molecules from area of a high concentration to a area of low concentration via protein channels or carriers

23
Q

what is an example of a molecule that passes through a protein channel

A

glucose

24
Q

what is a passive process

A

when molecules only use their kinetic energy and no ATP

25
Q

what is osmosis?

A

the net movement of water from a high water potential to a low water potential through a partially permeable membrane ( down a water potential gradient)

26
Q

what is water potential?

A

a measure of the tendency of water molecule to diffuse from one region to another

27
Q

what affects water potential?

A

more solute molecules = lower water potential

28
Q

what has the highest water potential?

A

pure water

29
Q

what happens when an animal cell is placed in pure water?

A

too much water will enter the cell and it will burst (cytolysis)

30
Q

what happens when a plant cell is placed in pure water?

A

cell wall prevents bursting so membrane pushes against the wall and makes the cell turgid

31
Q

what happens when an animal cell is places in a strong solute solution?

A

cell will shrink and wrinkle which means the cell is crenated

32
Q

what happens when a plant cell is placed in a strong solute solution?

A

cell membrane pulls away from the cell wall. This is called plasmolysis

33
Q

what would collective plasmolysed cells be called?

A

flaccid (tissue is flaccid)

34
Q

what are alternate words for high water potential?

A

dilute
hypotonic

35
Q

what are alternate words for low water potential?

A

concentrated
hypertonic

36
Q

what is active transport?

A

movement of substances against their concentration gradient across a cell membrane using ATP

37
Q

how is energy for active transport provided?

A

through the hydrolysis of ATP

ATP–ADP+P+energy

38
Q

why may active transport be needed?

A

-when you need more energy than kinetic energy
-cells may need to accumulate more of a particular ion

39
Q

what is bulk transport?

A

endocytosis
exocytosis

40
Q

when is bulk transport needed?

A

when molecules are too large to pass through the plasma membrane or through carrier/channel proteins

41
Q

what is endocytosis?

A

when a segment of plasma membrane surrounds and encloses the particle and brings it into the cell through a vesicle

42
Q

what is phagocytosis?

A

endocytosis with solid matter

43
Q

what is pinocytosis?

A

endocytosis with liquid matter

44
Q

what is exocytosis?

A

vesicle containing molecules moves towards and fuses with the membrane

45
Q

what is ATP needed for in exocytosis?

A

-fusing membranes together
-moving the vesicles

46
Q

how does a drop in temperature affect membrane structure and permeability?

A

-saturated fatty acids become compressed
-less kinetic energy
-reduces permeability

47
Q

how does a membrane maintain permeability?

A

-the kinks in the unsaturated fatty acid tails push adjacent phospholipids away
-cholesterol maintains fluidity

48
Q

what happens when the temperature increases?

A

-increases permeability
-can denature proteins

49
Q

what happens to proteins when they denature?

A

-breaks ionic and hydrogen bonds which unravels tertiary structure
-cytoskeleton and plasma membrane fall apart

50
Q

what is meant by cell signalling?

A

communication between cells

Biology module 2 (6 decks)

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