What happens to the carbon and hydrogen of glucose in aerobic respiration?

Carbon is released as carbon dioxide; hydrogen is combined with oxygen to form water.

Why is respiration a stepped process?

Energy is released in small amounts that can be captured in ATP, avoiding damaging heat, and each step can be controlled by an enzyme.

What are the products of glycolysis from one glucose?

Net 2 ATP, 2 reduced NAD and 2 pyruvate.

Why are two ATP used at the start of glycolysis?

To phosphorylate the hexose, making it more reactive.

What is substrate-level phosphorylation?

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

What is the net yield of ATP in glycolysis?

2 ATP per glucose (4 made, 2 used).

What happens to pyruvate in anaerobic respiration in animals?

It accepts hydrogen from reduced NAD and is converted to lactate.

Why must NAD be regenerated in anaerobic respiration?

So that glycolysis can continue to make ATP.

What happens to lactate after exercise?

It is carried to the liver and converted back to pyruvate, which is oxidised or converted to glucose and glycogen.

What does methylene blue show in a respiration experiment?

It becomes colourless when it accepts hydrogen, so the time taken shows the rate of respiration.

Why is a layer of oil used in the yeast and methylene blue experiment?

To keep out oxygen, which would reoxidise the dye.

What is a suitable control in the redox indicator experiment?

Boiled and cooled yeast, in which the enzymes are denatured.

Overview of respiration and glycolysisEdexcel International A Level Biology: Flashcards

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Give the word equation for aerobic respiration.

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Give the word equation for aerobic respiration.: Glucose + oxygen → carbon dioxide + water + energy (ATP).
What happens to the carbon and hydrogen of glucose in aerobic respiration?: Carbon is released as carbon dioxide; hydrogen is combined with oxygen to form water.
Why is respiration a stepped process?: Energy is released in small amounts that can be captured in ATP, avoiding damaging heat, and each step can be controlled by an enzyme.
Where does glycolysis occur?: In the cytoplasm.
What are the products of glycolysis from one glucose?: Net 2 ATP, 2 reduced NAD and 2 pyruvate.
Why are two ATP used at the start of glycolysis?: To phosphorylate the hexose, making it more reactive.
What is substrate-level phosphorylation?: The formation of ATP by direct transfer of a phosphate group from a substrate to ADP.
What is the net yield of ATP in glycolysis?: 2 ATP per glucose (4 made, 2 used).
What happens to pyruvate in anaerobic respiration in animals?: It accepts hydrogen from reduced NAD and is converted to lactate.
Why must NAD be regenerated in anaerobic respiration?: So that glycolysis can continue to make ATP.
What happens to lactate after exercise?: It is carried to the liver and converted back to pyruvate, which is oxidised or converted to glucose and glycogen.
What does methylene blue show in a respiration experiment?: It becomes colourless when it accepts hydrogen, so the time taken shows the rate of respiration.
Why is a layer of oil used in the yeast and methylene blue experiment?: To keep out oxygen, which would reoxidise the dye.
What is a suitable control in the redox indicator experiment?: Boiled and cooled yeast, in which the enzymes are denatured.

Exam questions on Overview of respiration and glycolysis

Glycolysis is the first stage of respiration in a liver cell supplied with glucose. In the later reactions of glycolysis a total of four molecules of ATP are made from each molecule of glucose.
Explain why the net gain of ATP from glycolysis is two molecules per molecule of glucose.2 marks
A student investigates respiration in yeast. She adds yeast suspension to glucose solution containing methylene blue, a redox indicator that is blue when oxidised and colourless when reduced. Each tube is covered with a thin layer of oil and kept in a water bath, and she records the time taken for the blue colour to disappear. One tube is kept at 15 °C and another at 35 °C.
Explain why the methylene blue becomes colourless more quickly at 35 °C than at 15 °C.2 marks
During a 100 m sprint, the muscle fibres in an athlete's leg respire anaerobically. In one fibre, 0.50 mmol of glucose is respired anaerobically by glycolysis alone.
Calculate the amount of lactate and the net amount of ATP produced from the glucose in this fibre.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).