Enzymes (C1.1) + Respiration (C1.2) + Photosynthesis (C1.3) Flashcards
Relationship between pH and enzyme activity (2)
ph increases = rate of reaction increases up till optimum ph
beyond optimum pH = denaturation + alter shape of active site
Enzymes role in energy (2)
reduce activation energy required for a reaction - increases rate of reaction
bonds in substrate weaken during enzyme-substrate complex = less energy needed to break
Enzyme anabolic reactions (4)
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
Enzyme catabolic reactions (4)
breaks complex molecules into simpler molecules
puts strain on the bonds, making them easier to break
releases energy
e.g digestion, respiration
Factors which affect enzyme activity (4)
substrate concentration
enzyme concentration
temperature
pH
Define the saturation point for an enzyme
point at which every active site is filled
Rate of reaction formula
(product formed/reactant used up)/ time
Define ATP (2)
consist of adenine, ribose sugar, 3 phosphate groups
used for temp. storage of energy + energy transfer
Uses of ATP (3)
synthesizing DNA + Protein
active transport of molecules + ions across membraines
move things around cells (e.g chromosomes + muscle fibers)
How ATP works (4)
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
Define phosphorylation (2)
process of adding a phosphate to a molecule
makes many molecules more unstable + more reactive
Define respiration
complex metabolic process to break down carbon compounds + create energy
Define respiratory substrate (2)
organic nutrient oxidised in respiration
e.g glucose, fats, proteins
Define aerobic respiration (4)
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
Define anaerobic respiration (4)
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
Factors which affect respiration rate (4)
Temperature
pH
concentration of respiratory substrates
oxygen concentration
Function of respirometer (2)
simple devices
measure rate of respiration in organism that respire aerobically
How is a respirometer used to measure the rate of reaction (6)
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
Structure of mitochondria (3)
has 2 membranes - outer + inner
outer membrane is permeable + contains transport proteins (porins)
inner membrane folded into cristae
How structure of mitochondria relates to its function (4)
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
Function of NAD in respiration (2)
functions as coenzyme
is a hydrogen carrier - able to be reduced + oxidised
Where does glycolysis occur
takes place in cytoplasm
Stage 1 of aerobic respiration (glycolysis) (6)
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
Stage 2 of aerobic respiration (link reaction) (5)
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
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
Glycolysis for Anaerobic respiration in animal cells (lactic acid fermentation) (2)
NADH becomes NAD+
Pyruvate forms lactate/lactic acid + carbon dioxide
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
No. of ATP generated by lipids (2)
460 ATP
produce more due to having long chains of carbon + hydrogen
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)
Why proteins are not used as main respiratory substrate
produce toxic nitrogenous wastes (NH3)
Inner Mitochondrial Membrane (IMM) (2)
membrane of matrix of mitochondria
contains series of 4 transmembrane proteins + 2 electron carriers
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
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
Define an enzyme (3)
biological catalysts
speed up chemical reactions + increase rate of occurrence
globular proteins
Define metabolism
complex network of interacting chemical reactions in living organisms
Properties of enzymes
specific - catalyses specific reaction
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
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
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
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
Why pH affects enzyme activity (2)
prescence/abscence of hydrogen ions affects ionic bonds between amino acids
changes AS shape
Define extracellular enzymes (2)
enzymes released from cell + work outside it
synthesized by ribosomes attached to endoplasmic reticulum
Define intracellular enzymes (2)
enzymes used within cells
synthesized by ribosomes in cytoplasm
Define an allosteric site
second active site for a different substance to bind/unbind to
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
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
Features of end-product inhibition (2)
enzymes allosterically inhibited by end-product of pathway
prevents over-production of certain substance
Features of mechanism-based inhibition (3)
irreversible binding of inhibitor to A.S through covalent bond
enzyme permanently loses catalytic ability
harmful to organisms
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
Define a coenzyme
molecule required for enzyme to carry out a function
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
Glycolysis for anaerobic respiration in yeast (ethanol fermentation) (2)
pyruvate converted to ethanol
CO2 produced + NADH oxidised to NAD (H used to make ethanol)
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
Define chemiosmosis
flow of protons (H+) down electrochemical gradient to generate energy
How much ATP is created from aerobic respiration of a glucose molecule
38
Define photosynthesis
production of carbon compounds in cells using light energy
Photosynthesis equation (2)
6CO2 + 6H2O –> C6H12O6 + 6CO2
carbon dioxide + water –> glucose + oxygen
Why leaves are green (2)
chlorophyll a + b absorbs other lights more + reflects green light most
pigments are bad absorbers of green light
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
Photosynthesis light-independent stage (Calvin cycle) (2)
takes place in stroma
uses ATP + reduced NAD to form carbon compounds (glucose) from CO2
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)
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
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)
Define rubisco
enzyme which adds CO2 to RuBP
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
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
Uses of excess triose phosphate produced (4)
glucose/starch
amino acids
fatty acids
DNA/RNA
Define photolysis
reaction which splits molecules of water using light energy
Different pigments of a leaf (3)
chlorophyll
beta-carotene
xanthophyll
Rf chromatography formula
distance travelled by sample/distance travelled by solvent
Define an action spectrum (2)
graph comparing rate of photosynthesis with wavelength of light
shows which wavelengths are good for photosynthesis
Limiting reactants of photosynthesis (3)
CO2 concentration
light intensity
temp.
How can CO2 concentration be controlled in photosynthesis experiments
dissolving sodium hydrogen carbonate in water
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
Define photosystems (3)
molecular arrays of chlorophyll + accessory pigments
within protein complexes + located in membranes
capture light energy + convert to chemical energy
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
Photosystems in thykaloid membranes (2)
photosystem I - most sensitive to light wavelengths of 700nm
photosystem II - most sensitive to light wavelengths of 680nm
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
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
ATP generation in photosytems II (2)
hydrogen ions accumulate in intermembrane space
H+ diffuse through ATP synthase to phosphorylate ADP to ATP
Features of Thykaloids (2)
flattened membrane-bound sacs
contain photosystems
Features of grana (2)
stacks of thykaloids
provide SA for as much photosystems, ETCs as possible
Features of lamella
connects grana to each other
Features of stroma lamella (2)
unstacked thykaloids
form connections between thykaloids in grana
Why is there a high concentration of Rubisco (2)
inefficient - slow enzyme + high energy requirements
can be competitively inhibited by oxygen
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
