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A Level Biology > Chapter 5 - > Flashcards

Chapter 5 - Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is the main structural component in a cell membrane?

A

phospholipid bilayer

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2
Q

name of the model showing membrane structure?

A

fluid mosaic model

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3
Q

why is it called fluid mosaic model?

A
  • fluid bc molecules move

- mosaic bc molecules in membrane forma pattern like a mosaic

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4
Q

what do membranes do? (3)

A
  • compartmentalisation
  • site of chemical reactions
  • cell communication
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5
Q

Compartmentalisation?

A
  • form partially permeable barriers between cytoplasm and cell’s environment
  • plasma cell surface membrane
  • organelles and cytoplasm - e.g. nuclear envelope, outer mitochondrial membrane
  • separating different parts of the same organelles - e.g. inner mitochondrial membrane
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6
Q

site of chemical reactions?

A

e.g. thylakoid membranes are where the light dependent reactions of photosynthesis happen

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7
Q

cell communication?

A

receptors bind signal molecules e.g. hormones and neurotransmitters
- antigens indicate whether a cell is self or non self

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8
Q

factors affecting membrane structure: 1 - temperature

A

(see Beetroot Pag)

  • as temp increases, the KE of phospholipid molecules increases and the fluidity of the membrane increases
  • temporary gaps appear between phospholipids which increases the permeability of the membrane
  • at high temps, intrinsic proteins denature forming large gaps in the membrane which becomes freely permeable
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9
Q

factors affecting membrane structure: organic solvents

A

E.g ethanol/ other alcohols
Organic solvent molecules get into the hydrophobic core of the membranes, dissolving the fatty acids
Thfr, destroying membrane

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10
Q

2 factors affecting membrane structure are?

A
  • Temperature

- Organic solvents

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11
Q

Ways substances cross membranes depends on which 2 things?

A
  • What the substance is

- Conc gradient (direction)

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12
Q

The 5 ways substances can cross membranes are:

A
  1. Simple diffusion
  2. Facilitated diffusion
  3. Active transport
    • 5, endocytosis, exocytosis
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13
Q

Simple diffusion?

A
  • Requires no energy from ATP hydrolysis, diffusion is always a passive process
  • Lipid soluble, non polar particles dissolve in the fatty acids of the membrane and move down the conc gradient across phospholipid bilayer
  • E.g. carbon dioxide, oxygen, lipid soluble hormones e.g testosterone
    • exception - water can cross via simple diffusion despite being polar - osmosis
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14
Q

Facilitated diffusion?

A
  • Water soluble, polar particles need a channel/ carrier protein to facilitate their diffusion
  • DOWN conc gradient
  • Carrier protien - conformational change
  • Channel protein - specific hydrophilic pore
  • E.g. glucose, amino acids
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15
Q

Active transport?

A
  • Any particles can be transported against conc gradient by a carrier protein using ATP hydrolysis
  • E.g. the Na(^+) and K(^+) pump
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16
Q

ATP hydrolysis equation?

A

ATP -> ADP + Pi

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17
Q

Endocytosis, Exocytosis ?

A

The ‘bulk transport’ of many particles or entire cells in and out of cells
ACTIVE - requires energy from ATP hydrolysis

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18
Q

Repeatability definition?

A

Every time a replicate is done, it is similar to previous replicates

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19
Q

Precision definition?

A

How close replicates are to each other

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20
Q

Overlapping standard deviation error bars?

A

Difference in mean isn’t significant

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21
Q

Error bars don’t overlap?

A

Difference in mean is significant

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22
Q

What is standard deviatioN?

A

SD gives a measure of how spread out a set of replicates is about the mean

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23
Q

Small SD=?

A

Replicates tightly clustered around mean - high repeatability and precision

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24
Q

Large SD =?

A

Replicates spread widely about the mean - low repeatability & precision

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25
Q

Water potential is a measurement of?

A

The pressure of water in a solution

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26
Q

Pure water has the?

A

Highest water potential: 0kPa

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27
Q

Water potential of any solution must be?

A

Negative

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28
Q

Use a _____ ___ to figure out direction of water movement?

A

Number line

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29
Q

On the number line?

A

0 is at the top

Arrow at bottom

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30
Q

Rate of water potential depends on?

A

Steepness of water potential gradient

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31
Q

OSMOSIS DEFINITION?

A

The movement of water from a high to low water potential across a selectively permeable membrane

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32
Q

Isotonic solution definition?

A

Same water potential, same conc of solute

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33
Q

Hypertonic solution ?

A
  • lower water potential, higher conc of solute

Hyper = strong, strong when hype

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34
Q

Hypotonic solution?

A

Higher water potential, lower conc of solute

Hippoes - weak solution

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35
Q

Plant cell in pure water

A

Cell becomes TURGID as solution is hypotonic

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36
Q

Plant cell in concentrated salt solution?

A

Cell becomes PLASMOLYSED as solution is hypertonic

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37
Q

Animal cell in pure water?

A

Cytolysis as solution is hypotonic (bursts)

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38
Q

Animal cell in conc salt solution?

A

Cell becomes crenated as solution is hypertonic

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39
Q

Pressure potential

A

Same water potential inside and outside of cell as cell contains solute particles
This is explained by the pressure the cell wall is exerting on the cytoplasm, preventing water movement - this is pres pot

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40
Q

Water potential =

A

Water potential of cell = solute potential + pressure potential
Water p = 0 or -
Solute p = always -
Prssure p = 0 or _+

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41
Q

Pressure potential counteracts?

A

Solute potential

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42
Q

Phospholipid?

A

2 hydrophobic fatty acid tails joined with ester bonds to glycerol which is also bound to a phosphate group, forming a hydrophilic phosphate group

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43
Q

Carrier protein?

A

A intrinsic protien capable of undergoing conformational change. Can active transport particles across the membrane using energy from ATP hydrolysis, or allow particles to cross the membrane by facilitated diffusion

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44
Q

Channel protein?

A

An intrinsic protein with a hydrophilic pore, allowing a specific water soluble particle (e.g. glucose) to cross the membrane by facilitated diffusion

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45
Q

How are channel proteins held in place?

A

Inteactions between the hydrophobnicbcore of the membrane and the hydrophobic R groups on the outside of proteins

46
Q

Cholesterol?

s

A

Regulates the fluidity of membrane by stabilising the phospholipids at high temps, and preventing them from crytraslising at low temp

47
Q

Receptor protein?

A

An instrinic protein with a binding site on the extracellular surface complementarty to a signal molecule, like a hormone. When a signal molecule binds to a receptor, a response is triggered inside the cell - cell signalling
E.g. receptors for neurotransmitters

48
Q

Signal molecule?

A

A molecule like a hormone or neurotransmitter that binds to a receptor, triggering a response

49
Q

Glycoprotein?

A

A chain of carbohydrates attarhed to a protein. Can act as an antigen if extrinsic and extracellular, identifying a cell as self or non self.
If instrinic, can act as a receptor in the same way as a receptor protein

50
Q

Glycolipid?

A

A chain of carbs attached to the fatty acids in the core of the membrane. Can act as antigens, identifying the cell as self or non self

51
Q

Phospholipid bilayer?

A
  • Hydrophobic core forms a barrier impermeable to water soluble particles separating the cytoplasm from the extracellular envir.
  • Hydrophilic phosphate heads interact with the water either side of the membrane
52
Q

Intracellular extrinsic membrane proteins could be?

A

Enzyme

53
Q

What is particular to each type of cell?

A

the type and number of proteins and lipids

54
Q

all cells contain?

A

plasma membrane

55
Q

cell membranes act as ?

A

barriers to control what passes in/ out of cells and organelles

56
Q

functions of the phospholipid bilayer in cell membrane?

A
  • creates partially permeable barrier - controls envir of cell
  • keeps membrane fluid but stable
57
Q

2 types of membrane proteins?

A

integral

peripheral

58
Q

integral are ?

A

based in centre

59
Q

peripheral are?

A

outside

60
Q

integral/ intrinsic proteins?

A
  • firmly embedded into cell membrane

- the region of the protein that is inside the CM is hydrophobic which keeps it anchored in place

61
Q

transmembrane proteins - what are they?

A

some integral proteins can span both layers of the cell membrane

62
Q

peripheral/ extrinstic proteins?

A
  • found ONLY ON 1 SIDE of CM and are not embedded into membrane
  • loosely held in place by electrostatic forces such as ionic bonds
63
Q

types of transmembrane protiens?

A

channel & carrier

64
Q

how do channel proteins work?

A

they form hydrophilic channels that allow specific water soluble molecules to pass through the membrane

65
Q

how do carrier proteins work?

A

transport specific molecules across M by changing shape when the mols bind to the protein

66
Q

what is a glycoprotein?

A

proteins with a chain of carbohydrate molecules attached

67
Q

what is a glycolipid?

A
  • lipids or phospholipids with a chain or carb molecules attached
68
Q

like phospholipids, cholesterol also has?

A

a hydrophilic end and a hydrophobic end

69
Q

how does cholesterol regulate membrane fluidity?

A

may sit inbetween the phospholipd mols

70
Q

how does cholesterol prevent the CM from becoming too sitff?

A

it prevents the phospholipids from grouping too close together

71
Q

how does cholesterol prevent the CM from becoming too fluid?

A

by interacting with the fatty acid tails of the phospholipids

72
Q

if CMs become too fluid?

A

water nd small soluble mol can more easily pass thru

73
Q

the fact that the CM acts as a partially permeable barrier allows?

A

the maintenance of diff conditions both inside and outside of cells

74
Q

why is compartmentalisation important for cells?

A
  • protection - e.g. fragile DNA in nucleus

- the ability to maintain diff conditions for diff metabolic reactions

75
Q

cell membranes are also involved in

A

the uptake and secretion of larger molecules

e.g. at synapse

76
Q

cell membranes as sites of chemical reactions?

A

membranes also contain prtns that are involved in chemical reactions e.g. respiration requires the presence of electron carriers & ATPase to be located on the inner mitochondrial membrane

77
Q

what happens if the membrane is too fluid?

A

can break apart

78
Q

why is temp an imprtnt factor affecting membrane fluidity?

A

many organisms cannot regulate their body temp

79
Q

at a very high temps what can happen to membrane fluidity?

A

the increased fluidity can cause the membrane to completely lose its structure

80
Q

apart from denaturation, what else can happen to membrane proteins at high temps?

A

can drift sideways which reduced their ability to function

81
Q

reducing the effect of low temp on CM fluidity- sat, unsat?

A
  • compression of phospholipids can be reduced by changing proportion of sat and unsat tails
  • unsat phslips have kiks which push them further apart
  • many organisms in cold envirs ar able to change proportion
82
Q

reducing the effect of low temp on CM fluidity- cholesterol?

A

cholesterol prevents compression of phslips

83
Q

reducing effects of high temp - cholesterol?

A

cholestrol pulls the phslips together by intercating with the tails

84
Q

effect of organic solvents - low and high conc?

A

low - makes CM more permeable to charged or larger mols

high - can destroy cells

85
Q

diffusion definition?

A

the net movement of particles from an area of high conc to an area of lower conc

86
Q

(diffusion) equilibrium is reached when?

A
  • conc of particles is equal on both sides of the CM so there is no net movement
87
Q

simple diffusion - what is able to slowly diffuse across the bilayer?

A

small polar mols with small diffs in charge e..g. water

88
Q

facilitated diffusion definition?

A

the net movement of particles from an area of high conc to an area of low conc across a partially permeable membrane via channel or carrier proteins

89
Q

what are aquaporins?

A

special channels proteins for water movement

kidney has lots

90
Q

both channel and carrier proteins are ?

A

specific to 1 type of particle

91
Q

channel vs carrier proteins

A

channel: transport small, polar, charged particles
carrier: larger or charged

92
Q

factors affecting diffusion?

A 
temp
conc gradient
surface area
diffusion distance 
no of channel and carrier protiens
size of molecule
93
Q

factors affecting diffusion- temp?

A

when temp inc, KE of particles inc, so move and collide at faster rate

94
Q

factors affecting diffusion- conc gradient?

A

steeper conc gradient = faster rate

95
Q

factors affecting diffusion- diffusion distance?

A

how far particles hav to move
takes longer to move further, so larger diffusion distance = slower rate
so organsims have specialised exchange surfaces

96
Q

factors affecting diffusion- SA?

A

rate can be increased by incrasing SA of CM

greater SA = greater no. of particles that can diffuse across CM in a given amount of time

97
Q

factors affecting diffusion- no of transport proteins?

A
  • rate of diffusion can be increased by increasing no of transport proteins in a given area of CM
    more channel & carrier prtns = more particles can cross CM in given amnt of time
98
Q

osmosis is a ? process

A

PASSIVE

99
Q

osmosis stops when?

A

equilibrium is reached

100
Q

as no cell wall to prevent bursting, its imporant to ?

A

carefully regulate water potential of blood and other extracelllular fluids at all times in animal cells

101
Q

why do plant cells have cell walls?

A

they prevent from bursting as they arb’t always able to regulate the water potential of the fluid outside cell

102
Q

active transport definition?

A

the movement of particles from an area of low conc to an area of higher conc using ATP and protein carriers

103
Q

endocytosis definition?

A

the bulk transport of ;arhe molecules into a cell

104
Q

exocytosis definition?

A

the bulk transport of large molecules out of a cell

105
Q

endocytosis: phagocytosis and pinocytosis?

A

phagocytosis: bulk transport of solid material into a cell
pinocytosis: bulk transport of liquids into a cell

106
Q

steps of endocytosis?

A
  • invagination of cell surface membrane around material that will be taken in
  • membrane fuses, enclosing material in vesicle
  • vesicle pinches off from CSM and moves towards interior of cell
107
Q

steps of exocytosis?

A
  • secretory vesicle moves towards CSM
  • vesicle fuses with CSM
  • which results in release of material to outside of cell
108
Q

where is ATP used in bulk transport?

A
  • fusion of cell membranes to create/destroy vesicles

- movement of vesicles along cytoskeleton

109
Q

process of active transport?

A
  • particle must bind to specific site in carrier prtn
  • on inside of cell, ATP also binds to carrier prtn
  • ATP is hydrolysed into ADP & Pi which releases energy and causes conformational change in carrier
  • carrier prtn is now open to other side of membrane and particle is released
  • phosphate mol is then released from carrier prtn, causing prtn to retrurn to orginl shape
110
Q

equilibrium doesn’t mean that the particles stop moing just that

A

the movements are equal in both directions

111
Q

what is hydrostatic pressure?

A

increased volume of solution. if solution is in a close system, such as a cell, this resulsts in an increase in pressure

112
Q

intrinsic and extrinsic proteins functions:

A
  • acting as recptors for drugs and hormones to bind to
  • acting as recognition sites for immune system
    helping cells adhere toegther to form tissues

A Level Biology (28 decks)

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