Respiration and Energy

Complete these activities after you have watched the video clips. Print the pages off and you have all the notes you need

about respiration.

Respiration releases energy for cells from glucose. This can be aerobic respiration, which needs oxygen, or anaerobic respiration, which does not. During exercise, the breathing rate and heart rate increase. During hard exercise an oxygen debt may build up.

What is aerobic respiration?Respiration is a series of reactions in which energy is released from glucose.

Aerobic respiration is the form of respiration which uses oxygen. It can be summarised by this equation:glucose + oxygen → carbon dioxide + water (+ energy)

Energy is shown in brackets because it is not a substance. Notice that:Glucose and oxygen are used upCarbon dioxide and water are produced as waste productsAerobic respiration happens all the time in the cells of animals and plants. Most of the reactions involved happen inside mitochondria, tiny objects inside the cytoplasm of the cell. The reactions are controlled by enzymes.

Grade E - What is energy used for?Grade C – Explain why birds and mammals can be active at night whilst it is cold?Grade A – On a cold night, a robin will lose a quarter of its body mass. Why?

When you exercise, your muscles need to contract more. They need more energy.

Sugar passes across the gut wall and some of it goes to the muscle cells where it is changed to glycogen.

Heart rate also goes up, so more blood with oxygen is delivered to the muscle cells.

Your breathing rate increases which gets more oxygen into the lungs and blood.

More respiration means the muscle cells need more glucose and oxygen.

They have to carry out more respiration to release the extra energy.

The waste products are carried away..

When muscle cells respire they release more heat and more carbon dioxide as well as energy

Anaerobic respirationNot enough oxygen may reach the muscles during exercise. When this happens, they use anaerobic respiration to obtain energy.Anaerobic respiration involves the incomplete breakdown of glucose. It releases around 5% of the energy released by aerobic respiration, per molecule of glucose. The waste product is lactic acid rather than carbon dioxide and water:glucose → lactic acid (+ little energy)

Muscle fatigueMuscles become fatigued (tired) during long periods of vigorous activity. This means that they stop contracting efficiently. One cause of this is the build-up of lactic acid in the muscles from anaerobic respiration. The lactic acid is removed from the muscles by blood flowing through them.

Fitness versus healthFit people are able to carry out physical activities more effectively than unfit people. Their pulse rate is likely to return to normal more quickly after exercise.But being fit is not the same as being healthy. Healthy people are free from disease and infection - they may or may

Oxygen debt - Higher tierMuch less energy is released during anaerobic respiration than during aerobic respiration. This is because the breakdown of glucose is incomplete.Anaerobic respiration produces an oxygen debt. This is the amount of oxygen needed to oxidise lactic acid to carbon dioxide and water. The existence of an oxygen debt explains why we continue to breathe deeply and quickly for a while after exercise.

Grade E – which provides more energy; aerobic or anaerobic?Grade C – what causes muscle fatigue?Grade A – Why do an athletes heart and breathing rate remain high for a few minutes after a race has ended?