5.2 respiration Flashcards
(32 cards)
give the two forms of cellular respiration, the conditions under which they occur, and the products formed.
aerobic respiration - requires oxygen, and produces carbon dioxide, water and much ATP.
anaerobic respiration - takes place in the absence of oxygen, and produces lactate (in animals), or ethanol and carbon dioxide (in plants and fungi), and only a little ATP.
give the four stages of aerobic respiration.
- glycolysis
- link reaction
- Krebs cycle
- oxidative phosphorylation
give the four stages of glycolysis.
- phosphorylation of glucose to glucose phosphate.
- splitting of the phosphorylated glucose.
- oxidation of triose
phosphate. - the regeneration of ATP.
summarise the events that occur during glycolysis, and state where glycolysis takes place.
- glycolysis is the splitting of the 6-carbon glucose molecule hexose bisphosphate into 3-carbon pyruvate molecules.
- glycolysis occurs in the in the cytoplasm of cells.
gives two reasons why glycolysis occurs in the cytoplasm, as opposed to the mitochondria.
- glucose is too large to cross the mitochondrial membrane.
- no transport proteins to move large molecules, such as glucose, across the membrane.
what is the overall yield from glucose molecules undergoing glycolysis?
- two molecules of ATP.
- two molecules of reduced NAD.
- two molecules of pyruvate.
where in a cell do the Krebs cycle and link reaction occur?
the mitochondrial matrix.
summarise the events that occur during the link reaction.
the 3-carbon pyruvate molecules enter into a series of reactions which lead to the formation of acetylcoenzyme A, a 2-carbon molecule.
during the link reaction, pyruvate undergoes a series of reactions. outline the changes that take place.
- the pyruvate is oxidised to acetate.
- in this reaction, the 3-carbon pyruvate looses a carbon dioxide molecule and two hydrogens.
- these hydrogens are accepted by NAD and used to form reduced NAD, which is later used to produce ATP.
- the 2-carbon acetate combines with coenzyme A (CoA) to produce acetylcoenzyme A.
give a summary of the overall equation for the link reaction.
pyruvate + NAD + CoA → acetyl CoA + reduced NAD + CO₂
summarise the events that occur during the Krebs cycle.
the introduction of acetylcoenzyme A into a cycle of oxidation-reduction reactions that yield some ATP and a large quantity of reduced NAD and FAD.
what are NAD and FAD?
- NAD and FAD are coenzymes involved in the oxidation and reduction reactions that occur during cellular respiration.
- they are responsible for accepting ‘high energy’ electrons and carrying them to the electron transport chain, where they are used to synthesise ATP molecules.
summarise the events that occur during oxidative phosphorylation.
the use of the electrons associated with reduced NAD and FAD are released from the Krebs cycle to synthesise ATP, with water produced as a by-product.
the synthesis of ATP by oxidative phosphorylation involves the transfer of electrons down what?
a series of electron carriers, which together form an electron transfer chain.
as the electrons are passed along the electron transfer chain, they release energy. describe what this energy is used for.
the energy released by the electrons causes the active transport of protons across the inner mitochondrial membrane into the inter-membranal space.
the protons accumulate in the inter-membranal space before they diffuse back into the mitochondrial matrix. give the enzyme is responsible for this process, and where it is found.
the protons diffuse back into the mitochondrial matrix through ATP-synthase channels, embedded in the inner mitochondrial membrane.
which molecule is the final acceptor of electrons in the electron transfer chain?
oxygen.
explain why it is important for oxygen to act as the final electron acceptor.
- the importance of oxygen in respiration is to act as the final electron acceptor of the hydrogen atoms produced in glycolysis and the Krebs cycle.
- without its role in removing hydrogen atoms at the end of the chain, the hydrogen ions would ‘back up’ along the chain and the process of respiration would come to a halt.
the process of oxidative phosphorylation involves a series of what type of reaction?
oxidation-reduction reactions.
during the Krebs cycle, a single molecule of ATP is produced as a result of substrate-level phosphorylation. explain substrate-level phosphorylation.
the 6-carbon molecule citrate loses carbon dioxide and hydrogen to produce the 4-carbon molecule succinate and a single molecule of ATP.
how is citrate produced?
the 2-carbon acetylcoenzyme A from the link reaction combines with a 4-carbon dicarboxylic acid to produce citrate.
give the overall yield of the link reaction and the Krebs cycle, per one molecule of pyruvate.
- reduced coenzymes NAD and FAD.
- one molecule of ATP.
- three molecules of carbon dioxide.
give two reasons why the Krebs cycle is significant in aerobic respiration.
- the Krebs cycle breaks down macromolecules into smaller, more useful molecules - pyruvate is broken down into carbon dioxide.
- it produces hydrogen atoms that are carried by NAD to the electron transfer chain to provide energy for oxidative phosphorylation.
describe the chemiosmotic theory of oxidative phosphorylation.
oxidative phosphorylation via the chemiosmotic theory occurs on the inner mitochondrial membrane and requires NADH and FADH₂, from the Krebs cycle, to produce water and many molecules of ATP.
