B2a Topic 1 Inside living cells

Demonstrate an understanding of how digital thermometers and breathing rate and heart rate thermometers, can provide more reliable data than traditional methods.

Which one would you choose to use? Why?

Explain why the heart rate and breathing rate increase with exercise and interpret data on these measurements.

Who is the fittest?Steve and Derek wanted to find out which of them was the fittest. They did some exercise which made them both breathe faster. They then stopped exercising and timed how long it took for their breathing rates to return to normal again.

Their results are shown in the graph on the next slide.

a) After how many minutes did Steve and Derek stop exercising?

2 minutes

b) From the graph, who do you think is the fittest of the two, and why?

Derek – as his breathing rate returned to a steady resting rate before Steve.

Derek said that the faster a person’s breathing rate returned to a steady resting rate, the fitter the person is.

c) Explain how this investigation may not have been fair.

Derek and Steve may have been exercising to varying degrees, accounting for the fact that Steve took longer to recover.

-Explain why during vigorous exercise, muscle cells may not receive sufficient oxygen for their energy requirements

How do cells get their energy?All organisms need energy to survive.

Animals obtain their energy from the food they eat, but plants can make their own food by photosynthesis.

In both cases, however, energy must first be converted into a form that can easily be used by cells. This process is called respiration.

Where does respiration take place?Mitochondria are cellular organelles in which respiration takes place.

Mitochondria use enzymes to convert the energy from glucose into ATP – the basic energy source for all cells.

Mitochondria have an inner membrane on which the enzymes are embedded.

This membrane is highly folded to increase the surface area on which respiration can take place.

What is aerobic respiration?Aerobic respiration is the process of releasing energy through the oxidation of glucose molecules.

Aerobic respiration is summarized by the equation:

This reaction releases energy in the form of ATP – a compound that can readily be used in cellular processes.

oxygencarbondioxide

glucose + + water ( energy)+

6O2 6CO2C6H12O6 + + 6H20 ( ATP)+

- Describe that glucose is changed into lactic acid and energy is released during anaerobic exercise

- Explain why extra oxygen is needed to remove the lactic acid that causes cramp (oxygen dept)

What is anaerobic respiration?Anaerobic respiration takes place with little oxygen, and releases less energy than aerobic respiration because glucose molecules are only partially broken down.

During strenuous exercise, cells are deprived of oxygen but still need energy to work. The body responds by converting glucose into lactic acid and energy, leading to an oxygen ‘debt’.

Lactic acid causes muscle cramps. When exercise stops, oxygen levels rise, paying off the oxygen debt and oxidising the lactic acid.

Glucose Lactic Acid + (some) Energy

Therefore the equation for Anaerobic respiration is…

from the digestive system

waste product

not as much energy as with

aerobic respiration

You will notice that this reaction is only an option for shortshort periods of time.

This is because the waste product is harmful and not enough energy is made to satisfy the

body.

The oxygen debt will have to be repaid when the exercise stops.

Oxygen will be used to break down the lactic acid that is present in the body. The oxygen ‘oxidises’ the lactic acid.

In fact, the lactic acid is oxidised into carbon dioxide and water.

In this way, the process of aerobic respiration can be converted into

The process of anaerobic respiration which can then turn back into...

Why is Lactic Acid so harmful?

Well, this chemical can stop muscles within the body, from contracting and relaxing.

The Lactic acid soaks the muscle cells and prevents the muscle cell from doing its job.

Relaxation

Contraction

If the muscles in your body stop contracting and relaxing they are said to be fatiguedfatigued. They eventually seize and you

experience cramp.

- Discuss why official advice on diet and exercise change over time and consider the scientific basis of current fashionable diets and advice

Different nutrients

Unhealthy diets?

A history of fad diets

Which diets are designed for weight loss?

How could you find out which diets work best?

Which diets have a scientific basis?

- Describe organelles in the cell that are involved in making protein

Exploring animal cells

Protein synthesis

Protein synthesis