2.5 biological membranes Flashcards Preview

biology module 2- foundations in biology > 2.5 biological membranes > Flashcards

Flashcards in 2.5 biological membranes Deck (112)
Loading flashcards...
1

what is tonoplast

the membrane surrounding the vacuole

2

is the nuclear envelope a membrane

yes

3

the membrane at the outside of the cell can be called...

the plasma membrane or the cell surface membrane

4

membranes are - permeable

partially

5

cell membranes control...

what can enter and exit the cell

6

cell membranes are used in cell

signalling

7

cell membranes provide - for enzymes

attachment sites

8

cytosol is...

an area of cytoplasm with no organelles in it

9

cell membranes compartmentalise, which means that they...

produce different compartments inside cells

10

phospholipid heads are

hydrophilic

11

phospholipid tails are

hydrophobic

12

what are the bonds in phospholipids?

ester bonds

13

what is formed when phospholipids are put in water?

micelles

14

what did Gorter and Grendel propose and when?

that the cell membrane is formed of a phospholipid bilayer, 1925

15

what was Davson-Danielli wrong about?

he said that proteins formed a layer on top of the membrane, but they are actually embedded in the membrane

16

who proposed the fluid mosaic model?

Singer and Nicholson

17

what model do we use for the plasma membrane structure?

the fluid mosaic model

18

proteins move more freely in - phospholipids, because...

unsaturated, they are bent and less rigid

19

what makes ATP?

ATP synthase (in the mitochondria)

20

can fat soluble molecules go through the phospholipid bilayer?

yes

21

a glycocalyx consists of...

a lipid and a glycolipid

22

what proteins are present in the plasma membrane?

peripheral proteins, enzyme or signalling proteins, glycoproteins, transport proteins, integral proteins

23

what are the transport proteins? 4

passive carrier protein, active carrier protein, channel protein, gated channel protein

24

integral and intrinsic proteins...

span the whole plasma membrane

25

peripheral and extrinsic proteins...

are found in one layer of the plasma membrane only

26

channel proteins are - in the plasma membrane

pores

27

channel proteins allow movement of - or - molecules, eg.

large or hydrophilic, glucose

28

channel proteins are often gated so that...

they only allow one type of ion through

29

channel proteins may be gated, which means they can...

open and close to allow certain things through

30

carrier proteins are often used in - using - energy

active transport, ATP

31

carrier proteins often have a particular shape so that

specific molecules fit

32

a glycocalyx is a - chain

carbohydrate

33

glycocalyxs form - bonds with -, helping to stabilize the membrane structure

hydrogen, water

34

aggregating means

bringing together

35

glycocalyxs are involved in cell adhesion for

aggregating cells into tissues

36

glycocalyxs act as receptors for

chemical signals

37

glycolipids in the glycocalyx act as cell identity markers or -, allowing...

antigens, the immune system to recognise them as self or non-self

38

cholesterol is found between - of a plasma membrane

the tails in the phospholipids

39

the function of cholesterol in the plasma membrane is...

to regulate fluidity

40

at high temperatures, cholesterol makes the plasma membrane more/less fluid

less

41

at low temperatures, cholesterol makes the plasma membrane more/less fluid

more

42

the plasma membrane being more fluid when it is colder is useful as it prevents...

the membrane from freezing

43

lipid soluble molecules go through

the phospholipid bilayer

44

polar or soluble molecules go through

hydrophilic channels created by channel proteins

45

endocrine systems signal to cells

over large distances

46

panacrine systems signal to cells

to other cells locally

47

autocrine systems signal

within the cell or to cells of the same type

48

the 'message molecule' sent is called the - or the -

signal or stimuli

49

the most common types of signal or stimuli are

hormones

50

the detect signals, cells must have sensors called -

receptors

51

receptors are often

proteins

52

non polar signals (such as testosterone and oestrogen) are able to... and bind to ...

diffuse directly through the phospholipid bilayer, intracellular receptors

53

polar signals must bind to the membrane bound receptors, which are the - proteins

intrinsic

54

5 steps of cell signalling:

1. stimuli
2. receptors
3. transducers
4. amplifiers
5. intracellular responses

55

a ligand is the

primary messenger

56

hormones are - messengers transported in the -

chemical, blood

57

target cells are any cells with a - for

receptor, the hormone

58

the hormone and the receptor on the target cell bind due to

their complementary shapes

59

channel proteins travel to- to let - into the cell

the cell membrane, glucose

60

binding causes the target cell to

react in a certain way

61

under normal circumstances, are there any channel proteins present in the plasma membrane?

yes

62

when blood glucose levels rise, the hormone - is secreted into the blood by the -

insulin, pancreas

63

medicinal drugs can interfere with

receptors

64

beta blockers block receptors to prevent...

the heart muscle increasing the heart rate if it would be dangerous for the patient

65

some drugs mimic natural receptors which people lack, eg in

schizophrenia

66

drugs blocking receptors form

drug- receptor complexes

67

painkillers attach to receptors and block - from travelling along the -

pain signals, nerve

68

drugs can do 2 things:

- mimic natural receptors
- block receptors

69

how does botox work?

it uses a toxin from the bacterium clostridium botulinum, the toxin binds to the receptors on muscle fibres, prevents them working and causes paralysis, reduces wrinkling of the skin

70

what is theory of Brownian Motion?

molecules move around randomly and bump into each other, and so tend to fill out the space that they are in

71

diffusion occurs down a

concentration gradient

72

diffusion is always

passive

73

diffusion can be - or -

simple or facilitated

74

what happens at equilibrium

the reaction rate is equal in both directions

75

which molecules go through channel proteins

large or polar molecules

76

is facilitated diffusion active

no

77

how wide is the phospholipid bilayer

7nm

78

how wide is the channel protein

0.8nm

79

what can move by osmosis

only water

80

pure water has a potential of

0

81

which symbol represents water potential

psi

82

diffusion occurs across a

partially permeable membrane

83

why are plant cells not haemolysed

they have a cell wall which prevents it

84

plant cells, water moves in so cell is

turgid

85

animal cells, water moves in so cell is

haemolysed

86

plant cells, water moves out so cell is

flaccid or plasmolysed

87

animal cells, water moves out so cell is

crenated

88

what is a hypertonic solution

something with a very low water potential

89

what is plamolysis

when water moves out of a cell, causing the vacuole to shrink and cytoplasm to move away from the cell wall

90

what is the incipient point of plasmolysis

when 50% of cells have been plasmolysed

91

what is bulk transport

moving large quantities of material in or out of the cell

92

endocytosis is

moving large quantities of material into the cell

93

exocytosis is

moving large quantities of material out of the cell

94

what type of energy does active transport need

ATP

95

when is active transport used

when diffusion isn't quick enough or when the movement is against a concentration gradient

96

cells involved in active transport have lots of

mitochondria

97

why are most carrier proteins one way

because otherwise particles would want to move back by diffusion

98

the shape of carrier proteins is

complementary

99

carrier proteins are complementary so that

they only allow specific molecules to enter snd exit the cell

100

the two types of endocytosis are

pinocytosis and phagocytosis

101

pinocytosis is

the cell taking in liquids

102

phagocytosis is

the cell taking in solids

103

an example of phagocytosis is

white blood cells engulfing and digesting pathogens

104

is bulk transport active or passive

active

105

why is bulk transport active

because it uses energy to transport material in vesicles along the cytoskeleton

106

exocytosis example

insulin exiting the cell

107

endocytosis example

pathogens entering the cell

108

why is beetroot used to investigate the effect of temperature on cell membranes

because their red cell sap is naturally coloured and easy to see

109

why does temperature effect cell membranes

because phospholipids break and proteins denature, and the plasma membrane melts. The tonoplast is broken and cell sap can escape from the vacuole.

110

what steps happen to the cell membrane as temperature is increased

1. proteins are denatured as the bonds in their tertiary structure are broken
2. phospholipid membrane bonds break
3. rate of diffusion increases

111

how do we conduct an experiment to investigate the effect of temperature on cell membranes?

1. place test tubes with 10cm3 of water into water baths set at 30, 40, 50 and 70, and leave one at room temperature. Leave for 15 mins to equilibrate.
2. cut beetroot into identical cylinders measured with a ruler and rinse and dry them
3. place the beetroot cylinders into test tubes and leave for 10 mins
4. remove the test tubes, remove the beetroot and swirl the liquid
5. place liquid into cuvettes and measure light absorption, record data in table and plot graph

112

how do we investigate osmosis in an artificial cell?

1. create a dilution series of 1.0, 0.8, 0.4, 0.2 and 0.1 mol dm3
2. cut visking tubing into 5 equal sections and tie then ends in knots
3. fill tubing 1/3 full with 0.4 mol dm3 solution
4. measure the mass of each concentration initially
5. place the artificial cells into each concentrated solution for 20 mins and then remove and weigh mass
6. create a table recording concentration, initial mass, final mass, mass change, and percentage change