Respiration and exercise

What is aerobic respiration? The process of releasing energy from food. It happens in all cells in plants and animals at all times. Oxygen is required.

Where does it occur? Inside mitochondria. Enzymes catalyse the reaction. ATP can be found inside and is used as an energy store.

What is the energy used for? To make larger molecules like proteins. Muscle contraction. Maintain body temperature (birds and mammals). To make larger molecules like proteins from sugars and nitrates in plants.

Exercise Task 1 – carry out some light exercise. What changes did you notice?

Increase in breathing rate and breathe deeper – get more oxygen to muscle cells and remove the build up of carbon dioxide. Increase in heart rate – delivers more blood to the muscles

The fitter you are the lower your resting HR, smaller increase in HR when exercising and a shorter recovery period. Fitness Recovery period Resting heart rate

Where does the energy come from? Stored as glycogen in the liver and muscles. During exercise this is broken down into glucose to provide energy.

Anaerobic respiration During vigorous exercise the body struggles to keep up with the demand from the muscles. Lacking oxygen the cells can respire anaerobically.

Lactic acid Anaerobic respiration causes muscle fatigue and produces lactic acid. This causes cramps and can be very painful.

Task 2 - Investigating muscle fatigue In pairs/ small groups count how many times you can open and close the tube holder in 20 seconds when holding a test tube holder in your left hand. Repeat 5 times and then with your right hand. Draw a line graph to show any patterns in your results.

Investigating muscle fatigue Hand Repetitions in 20 seconds T1 T2 T3 T4 T5 T6 Left Right

Oxygen debt After exercising hard you have to ‘pay back’ the oxygen you couldn’t deliver to the muscles. Breathing and heart rate will be high for some time until this is completed. This will allow the lactic acid to be broken down into carbon dioxide and water.

Exercise investigation Using the wooden benches and working in pairs or small groups you are to investigate the effects of exercise on heart rate. Measure your resting heart rate when sitting. Do step ups for 1 minute and then measure your resting HR sitting. Produce a line graph to show any patterns in your results.

Comparing recovery period Name Resting heart rate (bpm) HR after 1 min HR after 1.5 min HR after 2 min HR after 2.5 min HR after 3 min HR after 3.5 min HR after 4 min HR after 4.5 min HR after 5 min