Respiration (A-level only) Flashcards – AQA A-Level Biology - (7402)

What stage of aerobic and anaerobic respiration is glycolysis?

The first stage of both.

Where does glycolysis occur?

In the cytoplasm.

Does glycolysis require oxygen?

No, glycolysis does not require oxygen.

How is glucose converted into triose phosphate at the start of glycolysis?

Glucose is phosphorylated using ATP, and the resulting compound splits into two triose phosphate molecules.

What are the products of triose phosphate oxidation in glycolysis?

Pyruvate, reduced NAD and ATP.

Why does glycolysis have a net ATP yield?

More ATP is produced than is used in the initial phosphorylation.

What are the two possible products of pyruvate conversion during anaerobic respiration?

Lactate or ethanol.

What gas is released when pyruvate is converted to ethanol anaerobically?

Carbon dioxide.

What happens to reduced NAD during anaerobic conversion of pyruvate?

It supplies hydrogen and is oxidised back to NAD.

Why does NAD regeneration allow ATP production to continue without oxygen?

It allows further oxidation of triose phosphate in glycolysis, so glycolysis can continue producing ATP.

How does pyruvate enter the mitochondrial matrix during aerobic respiration?

By active transport.

What happens to pyruvate in the link reaction, and what are the products?

Pyruvate is oxidised and carbon dioxide is removed, producing a two-carbon acetate group and reduced NAD.

How is acetylcoenzyme A formed in the link reaction?

The acetate group combines with coenzyme A.

Which two stages of aerobic respiration does the link reaction connect?

Glycolysis and the Krebs cycle.

Where does the Krebs cycle take place?

In the mitochondrial matrix.

What happens when acetylcoenzyme A enters the Krebs cycle?

Its acetyl group combines with a four-carbon molecule to form a six-carbon molecule, releasing coenzyme A.

How is the four-carbon molecule regenerated in the Krebs cycle?

By a series of oxidation-reduction reactions.

What products do the oxidation-reduction reactions of the Krebs cycle release or produce?

Carbon dioxide and reduced coenzymes, including reduced NAD and reduced FAD.

By what process is ATP generated in the Krebs cycle?

Substrate-level phosphorylation.

What is substrate-level phosphorylation?

The direct transfer of a phosphate group from a substrate to ADP.

What is oxidative phosphorylation?

ATP production using energy released as electrons pass along an electron transfer chain in the inner mitochondrial membrane.

What donates electrons to the electron transfer chain in oxidative phosphorylation?

Reduced coenzymes.

How does electron transfer create a proton gradient during oxidative phosphorylation?

It releases energy to pump protons across the inner mitochondrial membrane.

How does ATP synthase use the proton gradient to produce ATP?

Protons pass through ATP synthase, which catalyses ATP formation from ADP and phosphate.

What is chemiosmosis?

The coupling of a proton gradient to ATP synthesis.

What role does oxygen play at the end of the electron transfer chain?

It is the final electron acceptor and combines with electrons and protons to form water.

What are respiratory substrates?

Molecules whose breakdown provides material for respiration and ATP production.

Besides glucose, which two types of molecule can provide breakdown products that enter the Krebs cycle?

Lipids and amino acids.

What happens to carbon-containing material from lipid and amino acid breakdown products in the Krebs cycle?

It is oxidised, producing reduced coenzymes.

How could the effect of temperature on respiration in yeast cultures be investigated?

Hold yeast cultures at different temperatures and measure the carbon dioxide produced over a fixed time.

How can carbon dioxide production be used to measure respiration rate in a yeast culture?

Calculate the amount of carbon dioxide produced per unit time.

What three factors should be kept constant when investigating the effect of temperature on yeast respiration?

Culture volume, yeast concentration and substrate concentration.

What do repeats allow in an investigation of respiration rate?

They allow variation to be assessed and a mean rate to be calculated.

Why use suitable controls and consistent measurement conditions in a respiration investigation?

To help distinguish the effect of the chosen variable from other influences.