Week 3 Flashcards
Respiration and some photosynthesis
What are the names of the two electron carriers in the electron transport chain?
Q and cytochrome c
Which protein complexes act as proton pumps?
Complexes 1, 3 and 4
What enables the protein complexes to act as proton pumps?
Shape changes from the free energy produced during electron transportation
How many protons are moved per NADH?
10
How many protons are moved per FADH2?
6
What is the evolutionary significance of Cytochrome c?
Evolutionary biologists can assess the similarities or differences among different species’ cytochrome c molecules to investigate evolutionary relationships
What is the main way that protons can move back into the mitochondrial matrix?
Through ATP synthase which couples the movement to the addition of inorganic phosphate to ADP to produce ATP
What type of energy is the proton gradient a form of?
Potential energy
In association to the laws of thermodynamics, why do protons move back across the inner membrane to form the proton gradient?
To be at an equal concentration and have lower free energy
What is the role of uncoupling proteins?
They move protons back across the membrane, not through ATP synthase
How do uncoupling proteins move protons back across the membrane?
They bind to the protons and transport them, they uncouple the energy in the proton gradient from ATP
What is the potential energy from the proton gradient converted to during uncoupling, and why?
It is converted to kinetic energy as heat, to either keep an organism warm or attract insects (pollinators)
What is oxidative phosphorylation?
The process of moving protons through ATP synthase and producing ATP
Which produces more ATP: oxidative phosphorylation or substrate level phosphorylation?
Oxidative phosphorylation (about 26 or 28), compared to substrate level phosphorylation which produces 4
Why does oxidative phosphorylation produce either about 26 ATP per glucose OR about 28 per glucose?
Because it depends on whether the electron shuttle is NADH or FADH, as FADH is less energetically favourable and therefore produces slightly less ATP
What is the maximum ATP yield per glucose during cellular respiration?
About 30 OR 32 ATP
Explain the structure of ATP synthase
Has channels that protons can move down and subunits that protons bind to. The binding of protons causes the subunits to rotate, which in turn causes shape changes and activates catalytic sites that produce ATP.
What happens to the pyruvate in anaerobic respiration/fermentation instead of getting transported into the mitochondria like in aerobic respiration?
It stays in the cytosol and is broken down into lactate, or ethanol in yeasts
If necessary, how can proteins be used in respiration?
If the ammonia of an amino acid is removed it can enter the pathway by being converted into pyruvate, acetyl CoA or metabolites of the citric acid cycle.
Where does beta oxidation occur?
In the mitochondrial matrix
How is energy gained from fats?
Acyl units from fatty acid chains are cleaved off and are converted into Acetyl CoA and are fed into the citric acid cycle
Why do triacylglycerols produce more ATPs than glucose?
Because fat molecules can pack together tightly and store more energy
Why do prokaryotes have higher yields of ATP per glucose than eukaryotes?
Because eukaryotes have an energetic cost of moving ATP out of the mitochondria, but because prokaryotes do not have a mitochondria there is no cost.
What is the purpose of the reaction of pyruvate being broken down into lactate or ethanol in anaerobic respiration?
To continue to regenerate NAD so glycolysis can continue to occur
What are the two phases of photosynthesis?
Calvin cycle reactions and light dependent reactions
What do some prokaryotes use instead of water as their electron donor in photosynthesis?
Hydrogen Sulfide (H2S)
Where do light reactions occur?
In the thylakoid membrane
Where do Calvin reactions occur?
In the stroma
Why are chloroplasts, and in turn, plants, green?
Because the green and yellow light is transmitted or reflected, not absorbed
What light to chloroplast pigments absorb to drive photosynthesis?
Red and blue light
Why do deciduous leaves turn yellow, orange, red in autumn?
The leaves recycle chlorophylls before they fall to conserve nitrogen, and the accessory pigments that are left which do not contain nitrogen mean that the leaves reflect and transmit yellow, orange and red light
Explain fluorescence, when electrons are raised to higher energy orbitals by photons of light in an isolated chlorophyll molecule
The electrons return to their original orbital and the energy is released as heat or light
Explain resonance energy transfer
Photosystems position chlorophylls close together so the energy from one excited chlorophyll is passed onto a neighbour chlorophyll causing a chain
What is the role of a reaction centre chlorophyll?
To pass the electron which is excited from resonance energy transfer onto the electron acceptor
What do water splitting complexes do and where does it occur?
Removes electrons from water and pass onto the oxidised reaction centre chlorophylls that have lost its electron. This occurs in Photosystem 2
What is the reaction centre chlorophyll of Photosystem 1 called
P700
What is the reaction centre chlorophyll of Photosystem 2 called?
P680
What is the role of the electron acceptor?
Take an energised electron away from the excited electron centre chlorophyll and passes the electron onto the electron transport chain.
