Respiration Flashcards
4 stages of aerobic respiration and an overview of each
- Glycolysis - the 6C glucose is split into 2 x 3C pyruvate molecules
- Link reaction - the 3C pyruvate enters a series of reactions which form acetyl coenzyme A (2C)
- Krebs cycle - acetyl CoA enters a cycle of redox reactions that produce some ATP and a lot of reduced NAD and FAD.
- Oxidative phosphorylation - electrons and reduced NAD and FAD from the Krebs cycle are used to synthesise ATP. Water is a by product.
Aerobic vs anaerobic
Aerobic respiration requires oxygen and produces carbon dioxide, water and ATP.
Anaerobic respiration takes place in the absence of oxygen and produces lactate in animals, or ethanol and carbon dioxide in plants and fungi. Less ATP is produced.
Link reaction - equation
Pyruvate + NAD + CoA ⇒ acetyl CoA + reduced NAD + CO2
Stages of glycolysis
- phosphorylation of glucose to glucose phosphate using ATP
- splitting of glucose phosphate into 2x triose phosphate
- oxidation of triose phosphate to pyruvate.
Net production of ATP and reduced NAD.
What is the purpose of respiration?
Conserve energy from the breakdown of glucose in the production of ATP.
Where does glycolysis occur?
in the cytoplasm
How many molecules of ATP are produced in glycolysis?
2
How many carbon atoms are there in a molecule of pyruvate?
3
How is glycolysis indirect evidence for evolution?
it occurs in all living organisms
Is glycolysis aerobic or anaerobic?
anaerobic.
What happens to pyruvate from glycolysis in aerobic respiration?
it is actively transported into the mitochondrial matix, then used in the link reaction.
What happens in the link reaction?
pyruvate is oxidised to acetate, producing reduced NAD and CO2 in the process. Acetate then combines with coenzyme A to produce acetylcoenzyme A.
What happens in the Krebs cycle?
Acetyl CoA reacts with a 4C molecule, releasing CoA and prodcing a 6C molecule which enters the Krebs cycle.
There are a series of oxidation-reduction reactions, in which:
- reduced coenzymes are generated
- ATP is produced by substrate-level phosphorylation
- CO2 (x2) is lost.
the 4C molecule is regenerated.
In which stages of aerobic respiation is ATP produced?
glycolysis, Krebs cycle, oxidative phosphorylation.
Which stage of aerobic respiration produces the most ATP?
oxidative phosphorylation
What respiratory substrates other than glucose are there? Which stage do the enter?
The breakdown products of lipids and amino acids - these enter the Krebs cycle.
How is ATP synthesised using the electron transport chain in aerobic respiration?
by oxidative phosphorylation.
How many times do the link reaction and Krebs cycle occur per molecule of glucose?
2
once per pyruvate and 2 pyruvates are produced per glucose
What is the main purpose of the Krebs cycle?
To generate reduced coenzymes for use in oxidative phosphorylation and generate a small amount of ATP.
Describe the stages of ATP production via oxidative phosphorylation. (aerobic respiration)
- Reduced NAD and FAD from the Krebs cycle carry H+ and electrons to the electron transfer chain.
- Electrons are transferred from NAD and FAD to the first molecule in the electron transfer chain.
- The electrons pass between electron carriers in a series of redox reactions.
- The electrons release energy as they are transferred from one electron carrier to the next. This energy is used to actively transport H+ ions (from coenzymes) from the matrix to the intermembrane space of the mitochondria.
- H+ diffuse back into the matrix through ATP synthase channels. This allows the synthesis of ATP to occur: ADP + Pi ⇒ ATP + H2O
- Electrons and H+ ions combine to form hydrogen atoms, which combine with oxygen to create water.
What is the role of oxygen in aerobic respiration?
As the final electron acceptor - oxygen combines with electrons and protons from the electron transport chain to produce water.
What are coenzymes? name some involved in respiration and photosynthesis.
molecules required for some enzymes to function, they are often involved in the transfer of chemical groups or electrons.
NAD, FAD, coenzyme A (respiration)
NADP (photosynthesis)
What is the purpose of anaerobic respiration?
To regenerate oxidised NAD, which can be used to produce more ATP in glycolysis. This is needed as without oxygen, all coenzymes become reduced, and oxidative phosphorylation and the Krebs cycle become stop - no ATP would be produced.
Equation for anaerobic respiration in plants and yeast
Pyruvate + reduced NAD ⇒ ethanol + carbon dioxide + oxidised NAD
Equation for anaerobic respiration in animals and some bacteria
pyruvate + reduced NAD ⇒ lactate + oxidised NAD
Which stages are common to both aerobic and anaerobic respiration?
glycolysis
Where do the Krebs cycle and link reaction ocur?
the mitochondrial matrix
Where does oxidative phosphorylation occur?
the inner mitochindrial membrane.
What happens if oxygen is not present at the end of the electron transport chain in oxidative phosphorylation?
electrons and hydrogens would back up along the ETC and coenzymes would all become reduced. Aerobic respiration would stop.
Which enzyme catalyses ATP synthesis in oxidative phosphorylation?
What is the equation for this reaction?
What type of reaction is this?
ATP synthase
ADP + Pi ⇒ ATP + H2O
Condensation
Where is ATP synthase found in a mitochondrion?
embedded in the inner mitochondrial membrane.
