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Biology > Enzymes (C1.1) + Respiration (C1.2) + Photosynthesis (C1.3) > Flashcards

Enzymes (C1.1) + Respiration (C1.2) + Photosynthesis (C1.3) Flashcards

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1
Q

Define an enzyme (3)

A

biological catalysts

speed up chemical reactions + increase rate of occurrence

globular proteins

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2
Q

Define metabolism

A

complex network of interacting chemical reactions in living organisms

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3
Q

Properties of enzymes

A

specific - catalyses specific reaction

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4
Q

Significance of enzyme shape to being complementary to subtrate (2)

A

interactions of amino acids determine active site shape

active site created from folding of polypeptide chain

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5
Q

How enzymes catalyse reactions (6)

A

substrate moves randomly until close enough to active site

chemical properties of enzyme surface attract substrate to active site

induced fit-binding : interactions between substrate + AS change 3D shape of both

if 2nd substrate, it will bind to another part of AS

changed substrate molecules weaken bonds + allow new bonds to form to make products

products detach from A.S + enzyme activity site returns to original shape

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6
Q

Molecular motion in forming enzyme substrate complexes (3)

A

enzyme substrate complex only form when both are close to each other

random movement causes occasional successful collision

increasing substrate/enzyme amount + temperature increases chances of collision

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7
Q

Variation of molecular motion between enzymes and substrates (3)

A

most cases substrate smaller than enzymes = substrate moves more

some substrates large + dont move much = enzyme has to move in relation to substrate

some enzymes embedded in membranes = substrate does all movement

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8
Q

Relationship between pH and enzyme activity (2)

A

ph increases = rate of reaction increases up till optimum ph

beyond optimum pH = denaturation + alter shape of active site

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9
Q

Why pH affects enzyme activity (2)

A

prescence/abscence of hydrogen ions affects ionic bonds between amino acids

changes AS shape

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10
Q

Enzymes role in energy (2)

A

reduce activation energy required for a reaction - increases rate of reaction

bonds in substrate weaken during enzyme-substrate complex = less energy needed to break

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11
Q

Enzyme anabolic reactions (4)

A

synthesis of complex molecules from simpler molecules

by reducing repulsion between substrates, allowing them to bond more easily

requires energy

e.g protein/DNA synthesis

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12
Q

Enzyme catabolic reactions (4)

A

breaks complex molecules into simpler molecules

puts strain on the bonds, making them easier to break

releases energy

e.g digestion, respiration

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13
Q

Define extracellular enzymes (2)

A

enzymes released from cell + work outside it

synthesized by ribosomes attached to endoplasmic reticulum

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14
Q

Define intracellular enzymes (2)

A

enzymes used within cells

synthesized by ribosomes in cytoplasm

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15
Q

Factors which affect enzyme activity (4)

A

substrate concentration

enzyme concentration

temperature

pH

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16
Q

Define the saturation point for an enzyme

A

point at which every active site is filled

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17
Q

Rate of reaction formula

A

(product formed/reactant used up)/ time

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18
Q

Define an allosteric site

A

second active site for a different substance to bind/unbind to

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19
Q

Features of non-competitive inhibitors (4)

A

bind to allosteric site - change shape of enzyme

enzyme rate of reaction decreases

changing enzyme shape = A.S no longer complementary to substrate

hence fewer complementary enzymes

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20
Q

Features of competitive enzyme inhibitors (4)

A

bind to active site of enzyme = substrate cannot bind to A.S

chemically similar to substrate

inhibitor competes with substrate for A.S

faster rate of reaction than non-competitive inhibitor

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21
Q

Features of end-product inhibition (2)

A

enzymes allosterically inhibited by end-product of pathway

prevents over-production of certain substance

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22
Q

Features of mechanism-based inhibition (3)

A

irreversible binding of inhibitor to A.S through covalent bond

enzyme permanently loses catalytic ability

harmful to organisms

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23
Q

Penicillin as mechanism-based inhibition (3)

A

bacterial cell wall protects + prevents bacteria from bursting

transpeptidase - enzyme which maintains cell wall structure by forming cross-links with polysaccharide chains

penicillin binds to transpeptidase irreversibly - inhibits its function + cell wall weakens

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24
Q

Define ATP (2)

A

consist of adenine, ribose sugar, 3 phosphate groups

used for temp. storage of energy + energy transfer

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25
Q

Properties of ATP (5)

A

soluble in water - can move freely through cytoplasm

stable at pH levels close to neutral

cannot pass freely through phospholipid bilayer

3rd ATP phosphate group easily removed + attached through hydrolysis + condensation reaction

hydrolysing ATP to ADP + phosphate releases energy

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26
Q

Uses of ATP (3)

A

synthesizing DNA + Protein

active transport of molecules + ions across membraines

move things around cells (e.g chromosomes + muscle fibers)

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27
Q

How ATP works (4)

A

ATP has 3 phosphates linked through high energy bonds

breaking of phosphate group (hydrolysis) releases energy

ATP –> ADP + one phosphate group

ADP converted back into ATP through respiration

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28
Q

Define phosphorylation (2)

A

process of adding a phosphate to a molecule

makes many molecules more unstable + more reactive

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29
Q

Define respiration

A

complex metabolic process to break down carbon compounds + create energy

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30
Q

Define respiratory substrate (3)

A

organic nutrient oxidised in respiration

e.g glucose, fats, proteins

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31
Q

Define aerobic respiration (4)

A

complete breakdown of glucose to generate a net gain of 36 molecules of ATP in presence of oxygen

takes place in cytoplasm + mitochondria

can use glucose, fats and proteins as respiratory substrates

produces water + carbon dioxide as waste products

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32
Q

Define anaerobic respiration (4)

A

partial breakdown of glucose to produce net 2 ATP in absence of oxygen

takes place in cytoplasm

only carbohydrates as respiratory substrates

produces lactic acid/lactate as a waste product

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33
Q

Factors which affect respiration rate (4)

A

Temperature

pH

concentration of respiratory substrates

oxygen concentration

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34
Q

Function of respirometer (2)

A

simple devices

measure rate of respiration in organism that respire aerobically

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35
Q

How is a respirometer used to measure the rate of reaction (6)

A

rate of oxygen consumption used as indicator of respiration

organism placed in closed system

alkaline solution added to absorb CO2

decrease in volume of gas in tube due to oxygen being used in respiration

reduces pressure in tube due to reduced oxygen

liquid will move towards tube

36
Q

Structure of mitochondria (3)

A

has 2 membranes - outer + inner

outer membrane is permeable + contains transport proteins (porins)

inner membrane folded into cristae

37
Q

How structure of mitochondria relates to its function (4)

A

cristae increases surface area

matrix - space between 2 membranes

matrix contains enzymes for respiration

small space of matrix allows for high concentration gradients to form

38
Q

Function of NAD in respiration (2)

A

functions as coenzyme

is a hydrogen carrier - able to be reduced + oxidised

39
Q

Define a coenzyme

A

molecule required for enzyme to carry out a function

40
Q

Reduced NAD equation (3)

A

NAD+ + 2H+ + 2e- –> NADH + H+ (reduced NAD)

NAD initially has one positive charge

NAD accepts 2 e + 1 p from 2 hydrogen atoms

41
Q

Where does glycolysis occur

A

takes place in cytoplasm

42
Q

Stage 1 of aerobic respiration (glycolysis) (6)

A

2 molecules of ATP phosphorylate glucose (6 carbon has phosphate added to it)

lysis - phosphorylated glucose split into 2 3 carbon G3P

each G3P oxidised by losing hydrogen atom

2NAD uses H atoms to produce NADH (reduced NAD)

2 ATP produced from each G3P (2 net)

1 glucose will produce net 2 ATP, 2 NADH, 2 pyruvate molecules

43
Q

Stage 2 of aerobic respiration (link reaction) (5)

A

2 pyruvates enter matrix of mitochondria through active transport

pyruvates dehydrogenated + decarboxylated

enzymes remove CO2 + transfer hydrogen to NAD (NADH)

pyruvate bonds with acetyl group (CoA) become 2 acetyl CoA

2 NADH formed + 2CO2 produced as waste product

44
Q

Stage 3 of aerobic respiration (krebs cycle) (7)

A

takes place in matrix of mitochondria

acetate from Acetyl CoA (2C) binds with oxaloacetate (4C) to make citrate (6C)

Co-A goes back to link reaction

oxidative decarboxylation - CO2 molecule removed + NAD becomes NADH + citrate becomes 5-carbon compound

2nd oxidative decarboxylation - another CO2 molecule removed + NAD becomes NADH + one molecule of ATP formed + 4-carbon compound

2H used to reduce FAD + H2O added to 4-carbon compound + NAD reduced again to make oxaloacetate

per glucose 6 reduced NAD, 2 reduced FAD, 2 ATP, 4 molecules of CO2

45
Q

Glycolysis for Anaerobic respiration in animal cells (lactic acid fermentation) (2)

A

NADH becomes NAD+

Pyruvate forms lactate/lactic acid + carbon dioxide

46
Q

Glycolysis for anaerobic respiration in yeast (ethanol fermentation) (2)

A

pyruvate converted to ethanol

CO2 produced + NADH oxidised to NAD (H used to make ethanol)

47
Q

Factors which determine how much ATP can be generated (4)

A

availability of hydrogen when respiratory substrates are broken down

more hydrogen = more reduced NAD

more reduced NAD = more protons to be transported across IMM

more ATP generated

48
Q

No. of ATP generated by lipids (2)

A

460 ATP

produce more due to having long chains of carbon + hydrogen

49
Q

Why Lipids are not used as a main respiratory substrate (4)

A

lipids must first be broken down to glycerol + fatty acids

glycerol must be further broken down to be used in glycolysis

fatty acids must be broken down into acetyl groups

lipids are harder to digest + transport (hydrophobic)

50
Q

Why proteins are not used as main respiratory substrate

A

produce toxic nitrogenous wastes (NH3)

51
Q

Inner Mitochondrial Membrane (IMM) (2)

A

membrane of matrix of mitochondria

contains series of 4 transmembrane proteins + 2 electron carriers

52
Q

Explain the electron transport chain (6)

A

reduced NAD (NADH) delivered to protein I

NADH –> NAD+, H+, 2e-

2 electrons passed along electron carriers

electrons allow H+ ions to be pumped into intermembrane space

FAD delivers electrons to 2nd protein

proton (H+) gradient created between intermembrane space + matrix

53
Q

Role of oxygen in electron transport chain (3)

A

electrons must go somewhere

O2 split into individual oxygen atoms

each O2 molecules joins with 4e- + 4H+ to form 2 H2O molecules

54
Q

ATP synthase role in ATP generation

A

flow of protons (proton motive force) generates energy to phosphorylate ADP

H+ ions pass through ATP synthase through diffusion –> rotates + converts ADP to ATP

55
Q

Define chemiosmosis

A

flow of protons (H+) down electrochemical gradient to generate energy

56
Q

How much ATP is created from aerobic respiration of a glucose molecule

A

38

57
Q

Define photosynthesis

A

production of carbon compounds in cells using light energy

58
Q

Define photolysis

A

reaction which splits molecules of water using light energy

59
Q

Photosynthesis equation (2)

A

6CO2 + 6H2O –> C6H12O6 + 6CO2

carbon dioxide + water –> glucose + oxygen

60
Q

Different pigments of a leaf (3)

A

chlorophyll

beta-carotene

xanthophyll

61
Q

Rf chromatography formula

A

distance travelled by sample/distance travelled by solvent

62
Q

Define an action spectrum (2)

A

graph comparing rate of photosynthesis with wavelength of light

shows which wavelengths are good for photosynthesis

63
Q

Why leaves are green (2)

A

chlorophyll a + b absorbs other lights more + reflects green light most

pigments are bad absorbers of green light

64
Q

Limiting reactants of photosynthesis (3)

A

CO2 concentration

light intensity

temp.

65
Q

How can CO2 concentration be controlled in photosynthesis experiments

A

dissolving sodium hydrogen carbonate in water

66
Q

How can photosynthesis be measured (4)

A

hydrogen carbonate indicator solution

change colour as CO2 concentration changes

less photosynthesis, more respiration = CO2 will increase + indicator turns orange/yellow

more photosynthesis, less respiraton = CO2 will decrease + indicator turns purple

67
Q

Define photosystems (3)

A

molecular arrays of chlorophyll + accessory pigments

within protein complexes + located in membranes

capture light energy + convert to chemical energy

68
Q

Photosystems in thykaloid membranes (2)

A

photosystem I - most sensitive to light wavelengths of 700nm

photosystem II - most sensitive to light wavelengths of 680nm

69
Q

Photosynthesis light-dependent stage (4)

A

photons of light hit pigments inside photosystems

excite electrons within the molecules

excited electrons transferred to reaction centre

photoactivation - photochemical reaction occurs which emits excited electron

70
Q

How oxygen is created from light independent stage of photosynthesis (5)

A

release of electrons from reaction centre creates unstable oxidised molecule

water molecules split to give up electron –>1/2 O2 + 2H+ + e-

electron replaces electron lost in reaction centre

protons released to thykaloid space to increase proton electrochemical gradient

oxygen diffuses out

71
Q

Advantages of photosystems having different pigments in a structured array (2)

A

variety of pigments = enough light energy for light dependent stage

energy only transferred from one close pigment to another - structure allows energy to reach reaction centre

72
Q

Photosynthesis light-independent stage (Calvin cycle) (2)

A

takes place in stroma

uses ATP + reduced NAD to form carbon compounds (glucose) from CO2

73
Q

Electron transport chain of non-cyclic photophosphorylation (5)

A

electrons released from PSII passed along electron carriers onto PSI

electrons re-excited by light energy from PSI

electrons passed onto protein ferrodoxin

electrons from ferrodoxin react with H+ in stroma to form H atoms

NADP –> reduced NADP (NADPH) (accepts 2 electrons from PSI + 2 H+ from stroma)

74
Q

ATP generation in photosytems II (2)

A

hydrogen ions accumulate in intermembrane space

H+ diffuse through ATP synthase to phosphorylate ADP to ATP

75
Q

Cyclic photophosphorylation (3)

A

light energy causes excitation of electrons from PSI

electrons move to electron carriers to pump H+ across

electrons will return to same PS1 after moving along carriers

76
Q

Features of Thykaloids (2)

A

flattened membrane-bound sacs

contain photosystems

77
Q

Features of grana (2)

A

stacks of thykaloids

provide SA for as much photosystems, ETCs as possible

78
Q

Features of lamella

A

connects grana to each other

79
Q

Features of stroma lamella (2)

A

unstacked thykaloids

form connections between thykaloids in grana

80
Q

Carbon fixation stage of Light independent stage of photosynthesis (Calvin Cycle) (2)

A

Co2 added to RuBP (5C) - catalysed by rubisco

forms 2 molecules of GP3 (3C)

81
Q

Define rubisco

A

enzyme which adds CO2 to RuBP

82
Q

Why is there a high concentration of Rubisco (2)

A

inefficient - slow enzyme + high energy requirements

can be competitively inhibited by oxygen

83
Q

Reduction of GP stage of Calvin cycle (2)

A

one ATP molecule adds phosphate to GP

hydrogen added to GP from NADPH to become triose phosphate

84
Q

Regeneration of RuBP (4)

A

6 CO2 can make 12 triose phosphate

10 triose phosphate (30C) used to make 6 RuBP (5C each)

requires 1 ATP

2 triose phosphate left over can synthesize carbon compounds

85
Q

Uses of excess triose phosphate produced (4)

A

glucose/starch

amino acids

fatty acids

DNA/RNA

86
Q

Interdependence of light dependent + light independent (Calvin cycle) (2)

A

Calvin cycle requires ATP + reduced NADP from light dependent

light dependent requires NADP + ADP to produce ATP + reduced NADP

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