Describe the mechanism for breathing in and out.

In = muscles contract, chest expands, pressure drops Out = muscles relax, chest shrinks, pressure rises

Explain pressure changes and how they help us breathe.

In - Bigger space → lower pressure → air rushes in Out - Smaller space → higher pressure → air pushed out

Q1. What part of the bell jar model represents the diaphragm? Q2. Give one strength of the bell jar model. Q3. Give one weakness of the bell jar model. Q5. Explain one reason why the bell jar model does NOT perfectly represent human breathing.

1. The flat sheet 2. it shows how when the diagram goes down the lungs expand 3. The diaphragm is dome shaped not a flat sheet 5. it doesn't show how the intercostal muscles work

Q1. What is meant by “lung volume”? Q2. Name one simple method for measuring lung volume. Q4. What does a peak flow meter measure?

1. the amount of air your lungs can hold 2. balloon test or spirometer 4. the speed of air leaving your lungs

Q1. In an experiment testing whether age affects lung volume, what is the independent variable? Q2. In the same experiment, what is the dependent variable? Q3. Give two control variables you should keep the same.

1. age 2. lung volume 3. same tools, same time of day

Q2. One 16‑year‑old has a much lower lung volume than the others. What is this called? Q3. Why is repeating results important? Q5. If the data shows a clear trend, does that mean the experiment was valid?

2. an anomaly 3. if the first time it wasn't the same conditions, for example, someone coughed mid-result or 5. not always

Why is it important that alveoli have very thin walls?

Short diffusion distance so gases move quickly

What is the difference between respiration and breathing?

Breathing is a physical process and respiration is a chemical process

How does smoking affect the alveoli?

Tar damages the alveoli, reducing their surface area, so less gas exchange can happen.

What is the main function of protein in the diet?

Needed for growth and repair

What is the role of iron in the body?

Makes haemoglobin for the red blood cells

Why does a very active person need more energy than someone who is not active?

Active people need more energy because their muscles are working more, so they use up more energy.

What is the role of bile in digestion?

breaks down fats and neutralises stomach acid

What happens to an enzyme if the temperature gets too high?

Active site changes shape and enzyme stops working

Why can an enzyme only work with one specific substrate?

Because their shapes match.

What colour does Benedict’s solution turn if glucose is present?

Brick-red

Q1. If a snack bar contains 10 kJ per gram and weighs 50 g, how much energy does it provide? Q2. Give one physical effect of eating too much. Q3. Which deficiency disease is caused by lack of iron? Q4. What is the role of the small intestine? Q5. Give one limitation of a digestive system model Q6. What does lipase break down? Q7. Why do villi have a large surface area?

1. 500kJ 2. high blood pressure 3. anemia 4. finishes digestion 5. doesn't show enzymes 6. lipids 7. large surface area = faster diffusion