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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

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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2
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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3
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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4
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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6
Q

Factors which affect enzyme activity (4)

A

substrate concentration

enzyme concentration

temperature

pH

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7
Q

Define the saturation point for an enzyme

A

point at which every active site is filled

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8
Q

Rate of reaction formula

A

(product formed/reactant used up)/ time

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9
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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10
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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11
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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12
Q

Define phosphorylation (2)

A

process of adding a phosphate to a molecule

makes many molecules more unstable + more reactive

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13
Q

Define respiration

A

complex metabolic process to break down carbon compounds + create energy

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14
Q

Define respiratory substrate (2)

A

organic nutrient oxidised in respiration

e.g glucose, fats, proteins

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15
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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17
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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18
Q

Factors which affect respiration rate (4)

A

Temperature

pH

concentration of respiratory substrates

oxygen concentration

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19
Q

Function of respirometer (2)

A

simple devices

measure rate of respiration in organism that respire aerobically

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20
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

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21
Q

Structure of mitochondria (3)

A

has 2 membranes - outer + inner

outer membrane is permeable + contains transport proteins (porins)

inner membrane folded into cristae

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22
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

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23
Q

Function of NAD in respiration (2)

A

functions as coenzyme

is a hydrogen carrier - able to be reduced + oxidised

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24
Q

Where does glycolysis occur

A

takes place in cytoplasm

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25
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

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26
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

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27
Stage 3 of aerobic respiration (krebs cycle) (7)
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
28
Glycolysis for Anaerobic respiration in animal cells (lactic acid fermentation) (2)
NADH becomes NAD+ Pyruvate forms lactate/lactic acid + carbon dioxide
29
Factors which determine how much ATP can be generated (4)
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
31
No. of ATP generated by lipids (2)
460 ATP produce more due to having long chains of carbon + hydrogen
32
Why Lipids are not used as a main respiratory substrate (4)
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)
33
Why proteins are not used as main respiratory substrate
produce toxic nitrogenous wastes (NH3)
34
Inner Mitochondrial Membrane (IMM) (2)
membrane of matrix of mitochondria contains series of 4 transmembrane proteins + 2 electron carriers
35
Explain the electron transport chain (6)
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
37
Role of oxygen in electron transport chain (3)
electrons must go somewhere O2 split into individual oxygen atoms each O2 molecules joins with 4e- + 4H+ to form 2 H2O molecules
38
Define an enzyme (3)
biological catalysts speed up chemical reactions + increase rate of occurrence globular proteins
39
Define metabolism
complex network of interacting chemical reactions in living organisms
40
Properties of enzymes
specific - catalyses specific reaction
41
Significance of enzyme shape to being complementary to subtrate (2)
interactions of amino acids determine active site shape active site created from folding of polypeptide chain
42
How enzymes catalyse reactions (6)
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
43
Molecular motion in forming enzyme substrate complexes (3)
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
44
Variation of molecular motion between enzymes and substrates (3)
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
45
Why pH affects enzyme activity (2)
prescence/abscence of hydrogen ions affects ionic bonds between amino acids changes AS shape
47
Define extracellular enzymes (2)
enzymes released from cell + work outside it synthesized by ribosomes attached to endoplasmic reticulum
48
Define intracellular enzymes (2)
enzymes used within cells synthesized by ribosomes in cytoplasm
49
Define an allosteric site
second active site for a different substance to bind/unbind to
50
Features of non-competitive inhibitors (4)
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
51
Features of competitive enzyme inhibitors (4)
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
52
Features of end-product inhibition (2)
enzymes allosterically inhibited by end-product of pathway prevents over-production of certain substance
53
Features of mechanism-based inhibition (3)
irreversible binding of inhibitor to A.S through covalent bond enzyme permanently loses catalytic ability harmful to organisms
54
Properties of ATP (5)
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
55
Define a coenzyme
molecule required for enzyme to carry out a function
56
Reduced NAD equation (3)
NAD+ + 2H+ + 2e- --> NADH + H+ (reduced NAD) NAD initially has one positive charge NAD accepts 2 e + 1 p from 2 hydrogen atoms
58
Glycolysis for anaerobic respiration in yeast (ethanol fermentation) (2)
pyruvate converted to ethanol CO2 produced + NADH oxidised to NAD (H used to make ethanol)
59
ATP synthase role in ATP generation
flow of protons (proton motive force) generates energy to phosphorylate ADP H+ ions pass through ATP synthase through diffusion --> rotates + converts ADP to ATP
60
Define chemiosmosis
flow of protons (H+) down electrochemical gradient to generate energy
61
How much ATP is created from aerobic respiration of a glucose molecule
38
62
Define photosynthesis
production of carbon compounds in cells using light energy
63
Photosynthesis equation (2)
6CO2 + 6H2O --> C6H12O6 + 6CO2 carbon dioxide + water --> glucose + oxygen
65
Why leaves are green (2)
chlorophyll a + b absorbs other lights more + reflects green light most pigments are bad absorbers of green light
66
Photosynthesis light-dependent stage (4)
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
67
Photosynthesis light-independent stage (Calvin cycle) (2)
takes place in stroma uses ATP + reduced NAD to form carbon compounds (glucose) from CO2
68
Electron transport chain of non-cyclic photophosphorylation (5)
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)
69
Cyclic photophosphorylation (3)
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
70
Carbon fixation stage of Light independent stage of photosynthesis (Calvin Cycle) (2)
Co2 added to RuBP (5C) - catalysed by rubisco forms 2 molecules of GP3 (3C)
71
Define rubisco
enzyme which adds CO2 to RuBP
72
Reduction of GP stage of Calvin cycle (2)
one ATP molecule adds phosphate to GP hydrogen added to GP from NADPH to become triose phosphate
73
Regeneration of RuBP (4)
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
74
Uses of excess triose phosphate produced (4)
glucose/starch amino acids fatty acids DNA/RNA
75
Define photolysis
reaction which splits molecules of water using light energy
76
Different pigments of a leaf (3)
chlorophyll beta-carotene xanthophyll
77
Rf chromatography formula
distance travelled by sample/distance travelled by solvent
78
Define an action spectrum (2)
graph comparing rate of photosynthesis with wavelength of light shows which wavelengths are good for photosynthesis
79
Limiting reactants of photosynthesis (3)
CO2 concentration light intensity temp.
81
How can CO2 concentration be controlled in photosynthesis experiments
dissolving sodium hydrogen carbonate in water
82
How can photosynthesis be measured (4)
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
83
Define photosystems (3)
molecular arrays of chlorophyll + accessory pigments within protein complexes + located in membranes capture light energy + convert to chemical energy
84
Penicillin as mechanism-based inhibition (3)
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
85
Photosystems in thykaloid membranes (2)
photosystem I - most sensitive to light wavelengths of 700nm photosystem II - most sensitive to light wavelengths of 680nm
86
Advantages of photosystems having different pigments in a structured array (2)
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
87
How oxygen is created from light dependent stage of photosynthesis (5)
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
88
ATP generation in photosytems II (2)
hydrogen ions accumulate in intermembrane space H+ diffuse through ATP synthase to phosphorylate ADP to ATP
90
Features of Thykaloids (2)
flattened membrane-bound sacs contain photosystems
91
Features of grana (2)
stacks of thykaloids provide SA for as much photosystems, ETCs as possible
92
Features of lamella
connects grana to each other
93
Features of stroma lamella (2)
unstacked thykaloids form connections between thykaloids in grana
94
Why is there a high concentration of Rubisco (2)
inefficient - slow enzyme + high energy requirements can be competitively inhibited by oxygen
95
Interdependence of light dependent + light independent (Calvin cycle) (2)
Calvin cycle requires ATP + reduced NADP from light dependent light dependent requires NADP + ADP to produce ATP + reduced NADP

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