Relevant LO’s…B2.6 Aerobic and anaerobic respiration

B2.6.1 Aerobic Respiration• The chemical reactions inside cells are controlled by enzymes• During aerobic respiration (respiration that uses oxygen) chemical reactions occur that: Use glucose (a sugar) and oxygen Release energy

• Aerobic respiration takes place continuously in both plants and animals• Most of the reactions in aerobic respiration take place inside mitochondria• Aerobic respiration is summarised by the equation:

Glucose + oxygen -> carbon dioxide + water (+ energy)• Energy that is released during respiration is used by the organism. The energy may be

used: To build larger molecules from smaller ones In animals, to enable muscles to contract In mammals and birds, to maintain a steady body temperature in colder surroundings In plants, to build up sugars, nitrates and other nutrients into amino acids which are then built up into proteins

• During exercise a number of changes take place: The heart rate increases The rate and depth of breathing increases

• These changes increase the blood flow to the muscles and so increase the supply of sugar and oxygen and increase the rate of removal of carbon dioxide

• Muscles store glucose as glycogen, which can then be converted back to glucose for use during exercise

Relevant LO’sB2.6.2 Anaerobic Respiration• During exercise, if insufficient oxygen is reaching the muscles they use

anaerobic respiration to obtain energy• Anaerobic respiration is the incomplete breakdown of glucose and produces

lactic acid• **As the breakdown of glucose is incomplete, much less energy is

released than during aerobic respiration. Anaerobic respiration results in an oxygen debt that must be repaid in order to oxidise lactic acid to carbon dioxide and water** (HT only)

• If muscles are subjected to long periods of vigorous activity, they become fatigued and stop contracting efficiently. One cause of muscle fatigue is the build up of lactic acid in the muscles. Blood flowing through the muscles removes the lactic acid

Short Answer Questions

1. Respiration is a chemical process. a) Where does respiration take place? Circle the correct answer.

(1)chloroplasts mitochondria nuclei ribosomes

b) Which food material is used in respiration? _________________________________________________________________ (1)c) Name the two waste materials that are produced in respiration._________________________________________________________________ (2)d) Respiration is important in muscle contraction. Explain why. _________________________________________________________________ (2)

2. a) Copy and complete the word equation for aerobic respiration.Oxygen + __________ -> Water + __________ (+ energy)b) i) Which substance is missing in anaerobic respiration?_________________________________________________________________ (1)ii) What is made during anaerobic respiration?_________________________________________________________________ (1)iii) Muscles get tired during anaerobic respiration. Explain why._________________________________________________________________ (1)

Past Paper Question – Longer Answer

In this question, you will be assessed on using good English, organising information clearly and using specialist terms where appropriate

The bar charts show what happens in an athlete’s muscles when running in two races of different distances.

The equations show two processes that occur in muscle cells.

Use all the information to explain what happens in the athlete’s muscles when running in the two races (6)

Aerobic RespirationGlucose + Oxygen -> Carbon Dioxide + Water

Anaerobic RespirationGlucose -> Lactic Acid

100m race 1500m race

Rate

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Rate

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5-6 marks 3-4 marks 1-2 marks 0 marks• There is a clear, balanced and

detailed explanation about the differences between the two races in terms of aerobic and anaerobic respiration

• The answer is coherent and in a logical sequence

• It contains a range of appropriate or relevant specialist terms used accurately

• The answer shows few errors in spelling, punctuation and grammar

• There is some attempt to explain the differences between the two races in terms of respiration

• The answer has some structure and organisation

• The use of specialist terms has been attempted, but not always accurately

• There may be some errors in punctuation, spelling and grammar

• There is a brief description of the differences between the two races, which has little clarity and detail

• The answer is poorly constructed with an absence of specialist terms or their use demonstrates a lack of understanding of their meaning

• The spelling, punctuation and grammar are weak

• No relevant content

Examples of biology points made in the response:

Use all the information to explain what happens in the athlete’s muscles when running in the two races

(6 marks)

• Energy is transferred faster in the 100m race• Carbon dioxide produced faster during the 1500m race/more• Carbon dioxide produced• Correct reference to twice/half as fast in either/both cases• Respiration during 100m race (mainly) anaerobic• Respiration during 1500m race (mainly) aerobic• Aerobic respiration produced carbon dioxide• Anaerobic respiration produced lactic acid