5A - photosynthesis and respiration Flashcards
what are the 4 stages of aerobic respiration and where do they occur?
Glycolysis - cytoplasm
link reaction - mitochondrial matrix
krebs cycle - mitochondrial matrix
oxidative phosphorylation - inner membrane / cristae
describe gylcolysis
glucose (6C) is phosphorylated due to the hydrolysis of 2ATP into 2ADP +2Pi forming glucose phosphate (6C) . this molecules splits into triose phosphate ( 3C X 2). this molecule is oxidised, losing a hydrogen which is picked up by the co - enzyme, 2NAD being reduced into 2NADH. 4ADP and 4Pi forms 4ATP in a condensation reaction. 2 3C pyruvates are formed.
what is the gain of molecules at the end of glycolysis
2ATP, 2NADH and 2 3C pyruvate molecules.
describe the link reaction
pyruvate molecule is oxidised and NAD is reduced forming NADH. the pyruvate is decarboxylated releasing CO2 and producing an acetate molecule. acetate reacts with co-enzyme A forming acetyl coenzyme A
describe the krebs cycle
acetyl CoA reacts with a 4C molecule producing a 6C moleucle. the 6C molecule is decarboxylated releasing 2 carbons and producing 2 CO2 molecules. it is oxidised releasing hydrogens which are taken up by by 3 NAD enzymes and 1 FAD enzyme, producing 3NADH and 1FADH2. an ATP molecule is produced via substrate level phosphorylation. this will reproduce a 4C molecule.
what are the products of the krebs cycle
2CO2, 3NADH,1FADH2 and 1ATP
describe oxidative phosphorylation
NADH and FADH2 are oxidised releasing the H. the H splits into an electron and a proton. the electron moves across the etc through cattier proteins, releasing energy which is used in the active transport of protons across the inner membrane space, this forms an electro-chemical gradient. protons move back to the matrix through ATP synthase via facilitated diffusion. this causes rotation- for every 1 proton there is 1 rotation, and 1 ATP molecule is made every 3 rotations-
oxygen acts as the final electron acceptor, joining with 2 electrons and 2 protons to produce 1 water molecule.
what happens to lipids before they are used as products
they are hydrolysed by lipase into fatty acids and glycerol. the glycerol is phosphorylated and then converted into triose phosphate, entering glycolyis
what happens to the glycerol before entering the process of respiration
the glycerol is phosphorylated and then converted into triose phosphate, entering glycolyis
what happens to the fatty acids before entering the process of respiration
the fatty acids are converted into acetyl conenzyeme A, entering the krebs cycle
when is protein used at respiratory substrate
severe starvation
what happens to proteins inorder to be used as a respiratory substrate
proteins are hydrolysed into amino acids. 3 carbon compounds are converted into pyruvates. 4 and 5 carbon compounds are used directly in the krebs cycle
what is deamination
removal of the amine group NH2
steps of alcohol fermentation in anaerobic respiration
occurs in yeast and some plants.
pyruvate will lose a molecule of CO2 and accepts a hydrogen from NADH. this produces ethanol and regenerates NAD
pathway of lactate fermentation in anaerobic respiration
occurs in animals and bacteria.
pyruvate accepts a hydrogen from NADH.
this produces lactate and regenerates NAD
negatives of respiring anaerobically in animals
accumulation of lactate causes cramp and muscle fatigue. as lactate is acidic it will reduce the pH affecting enzymes
what is anerobic respiration and where does it occur
respiration in the absence of oxygen. occuring in the cytoplasm of the cell
what is the efficiency of aerobic respiration
38 molecules of ATP produced = 32% efficiency
what is the net production of ATP in anaerobic respiration
2 molecules
word equation for photosynthesis
carbon dioxide + water -> glucose + oxygen
why do plants need energy
photosynthesis
active transport
DNA replication
protein synthesis
mitosis + meiosis
structure of an ATP molecule
adenine, ribose sugar and 3 phosphate groups
why is ATP a good energy source
- releases energy in small and manageable amounts so no energy is wasted
- ATP is easily broken down so energy is easily released
- cant leave the cell so there is always an energy source
location of the dependent and independent reactions
dependent - thylakoid membrane of the chloroplasts
independent - stroma of the chloroplast
Describe the structure of a thylakoid membrane, and proteins it contains?
folded membrane containing chlorophyll
embedded with transmembrane electron carrier proteins
Describe the location of chlorophyll and what is its role?
located on the thylakoid membrane
different proteins that absorb light
Summary of the light-dependent reaction
first stage of photosynthesis
occurs in the thylakoid membrane
uses light energy and water to produce ATP and NADPH for the light-independent reaction
involves photoionisation of chlorophyll, photolysis and chemiosmosis
What happens during photoionisation of chlorophyll
light energy absorbed by the chlorophyll excites electrons so they move to a higher energy level, leaving the chlorophyll
some of the energy released is used to make ATP and NADPH
What happens during photolysis
light energy absorbed by chlorophyll, splitting water into oxygen, H+ and e-
products of photolysis and what are they used for
oxygen - used in respiration or diffuses out the stomata
H+ - picked up by NADP to form NADPH, after passing through ATPsynthase, also form ATP
e- - join with the magnesium ion found in chlorophyll
How is the chemiosmotic gradient formed
electrons gain energy and move across the electron carrier proteins in the thylakoid membrane
they release energy which pumps protons across the thylakoid membrane into the stroma
an electrochemical gradient made protons pass back across to the thylakoid via ATP synthase producing ATP
what happens to the protons after chemiosmosis
combine with NADP to become NADPH
products of the light dependent reaction
ATP
NADPH
oxygen
Summary of the light independent reaction
calvin cycle
uses CO2, NADPH and ATP to form glucose
occurs in the stroma which contains the enzyme rubisco
1st step of the calvin cycle
CO2 combines with ribulose bisphosphate (5c) to form an unstable 6c molecule.
catalysed by rubisco
2nd step of the calvin cycle
the 6c molecule is broken down into 2 glycerate - 3- phosphate (3c) molecules.
3rd step of the calvin cycle
GP is reduced to form triose phosphate
the energy is provided by the hydrolysis of 2 ATP molecules
NADPH is also oxidised for the H+
4th step of the calvin cycle
5/6 turns of the calvin cycle produce RuBP from triose phosphate
this also uses energy from the hydrolysis of ATP.
1/6 turns of the calvin cycle produce organic compounds e.g. glucose
requirements/conditions for photosynthesis
photosynthetic pigments e.g. chlorophyll
carbon dioxide
water
light
optimum temperature
3 limiting reactants of photosynthesis
light intensity
CO2 concentration
temperature
how does light intensity affect rate of photosynthesis
low light intensity limits the light dependent reaction, this decreases the ATP and NADPH produced, so less is transferred to the light in dependent reaction, decreasing rate of photosynthesis.
when there is a high light intensity, something else will be the limiting factor
how does CO2 concentration affect rate of photosynthesis
low CO2 concentration limits the light independent reaction, less CO2 can bind with RuBP, less GP and TP made.
high CO2 conc means something else is the limiting factor
how does temperature affect rate of photosynthesis
low temp, low kinetic energy, low rate of photosynthesis , due to enzyme - catalysed reactions requiring Ke.
optimum temp, the optimum rate of photosynthesis
high temp, enzymes begin to denature, rate of photosynthesis stops.
what is the saturation point
the point on a graph where a different factor become the limiting factor, when the graph begins to plateaux.
