Exam questions · Biology
Homeostasis
- 48 exam questions
- 145 marks
- 72 quick checks
Maintaining a Constant Internal Environment
Just this lesson-
1 State [1 mark]
State what is meant by homeostasis.
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Model answer
The regulation of the conditions inside the body so that they stay constant.
Mark scheme
- Regulation of internal conditions to keep them constant — 1 mark
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2 Name [2 marks]
Name two conditions in the body that are controlled by homeostasis.
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Model answer
Body temperature and blood glucose concentration.
Mark scheme
- Body temperature — 1 mark
- Blood glucose concentration, or water content — 1 mark
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3 Describe [3 marks]
Describe the roles of the receptor, the coordination centre and the effector in a control system.
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Model answer
The receptor detects a change in a condition. The coordination centre receives the information and decides what the response should be. The effector, which is a muscle or a gland, carries out the response.
Mark scheme
- Receptor detects the change — 1 mark
- Coordination centre receives information and decides — 1 mark
- Effector carries out the response — 1 mark
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4 Explain [3 marks]
Explain why it is important that the body temperature stays close to 37 °C.
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Model answer
The enzymes in the body have an optimum temperature of about 37 °C. If the temperature changes, the enzymes work more slowly, or they stop working. So the chemical reactions in the cells would be too slow, and the cells could not carry out their functions.
Mark scheme
- Enzymes work best at about 37 °C — 1 mark
- A change slows or stops the enzymes — 1 mark
- Reactions in the cells are affected — 1 mark
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5 Explain [3 marks]
Explain what is meant by negative feedback, using the control of blood glucose as an example.
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Model answer
Negative feedback is a response that reverses a change. When the glucose concentration of the blood rises, insulin is released, which makes the concentration fall back to normal. Once it is normal, less insulin is released.
Mark scheme
- A response reverses the change — 1 mark
- Glucose rises, so insulin is released — 1 mark
- The concentration falls, so less insulin is released — 1 mark
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6 Evaluate [6 marks]
A runner takes part in a race on a hot day. Describe the changes that take place in the body of the runner, and explain how homeostasis helps the runner to stay healthy.
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Model answer
The runner's muscles release heat, so the body temperature tends to rise, which is a stimulus. The muscles also use glucose and the runner loses water in sweat, so the glucose concentration and the water content of the body tend to fall. Receptors detect each of these changes, and a coordination centre, such as the brain or the pancreas, decides on the response. The effectors, which are glands and muscles, carry out the responses. For example, the sweat glands release more sweat, to cool the body, and glucose is released from stores to replace what is used. Each response reverses the change, which is negative feedback. This keeps the temperature close to 37 °C, so that the enzymes in the cells keep working, and keeps the glucose and water content steady, so that the cells have energy and do not gain or lose too much water.
Mark scheme
- Temperature rises, which is a stimulus — 1 mark
- Glucose and water fall — 1 mark
- Receptors detect the changes — 1 mark
- Effectors respond, for example more sweating — 1 mark
- Negative feedback reverses the change — 1 mark
- Enzymes and cells keep working — 1 mark
Quick check
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1
What is homeostasis?
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B: Regulation of internal conditions so they stay constant
The regulation of conditions inside the body to keep them constant.
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2
What is the normal body temperature?
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C: 37 °C
About 37 °C.
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3
Which part of a control system carries out the response?
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D: The effector
The effector.
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4
Which of these is an effector?
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A: A muscle
A gland or a muscle carries out a response.
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5
What does negative feedback do?
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C: It reverses a change
It reverses a change and returns the condition to normal.
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6
Why must the temperature of the body stay constant?
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A: The enzymes work best at about 37 °C
The enzymes work best at about 37 °C.
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7
Which of these is an internal change that the body responds to?
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B: Eating a meal
Eating a meal raises the blood glucose concentration.
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8
Which of these is NOT usually kept constant by the body?
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D: The amount of exercise
The body does not keep the amount of exercise constant.
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9
How does hormonal control compare with nervous control?
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B: It is slower and lasts longer
It is slower, and the effects usually last longer.
Why Homeostasis Matters: Enzymes and Osmosis
Just this lesson-
1 State [1 mark]
State the optimum temperature of most enzymes in the human body.
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Model answer
About 37 °C.
Mark scheme
- 37 °C — 1 mark
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2 Explain [2 marks]
Explain why a low temperature reduces the rate of an enzyme-controlled reaction.
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Model answer
The enzyme and substrate molecules have less energy and move more slowly. There are fewer collisions between them, so the rate of the reaction is lower.
Mark scheme
- Molecules move more slowly — 1 mark
- Fewer collisions — 1 mark
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3 Explain [3 marks]
Explain why a very high body temperature can be fatal.
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Model answer
A very high temperature breaks the bonds that hold the enzymes in shape, so the enzymes are denatured. The substrate no longer fits in the active site, so the reactions in the cells, such as respiration, stop.
Mark scheme
- Enzymes are denatured — 1 mark
- Active site changes shape, so the substrate does not fit — 1 mark
- Reactions in the cells stop — 1 mark
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4 Describe [3 marks]
Describe what happens to a red blood cell that is placed in pure water.
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Model answer
Water enters the cell by osmosis, because the water outside is more dilute than the cytoplasm. The cell swells, and it may burst, because animal cells have no cell wall.
Mark scheme
- Water enters by osmosis — 1 mark
- The cell swells — 1 mark
- May burst, no cell wall — 1 mark
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5 Calculate [3 marks]
A cylinder of potato has a mass of 5.0 g. After one hour in a concentrated salt solution, its mass is 4.2 g. Calculate the percentage change in mass.
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Model answer
The change is 0.8 g, and 0.8 divided by 5.0, multiplied by 100, is 16%, so the percentage change is a decrease of 16%.
Mark scheme
- Change in mass is 0.8 g — 1 mark
- 0.8 divided by 5.0, multiplied by 100 — 1 mark
- 16% decrease — 1 mark
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6 Evaluate [6 marks]
Explain the importance of controlling the temperature of the body, and the water content of the blood.
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Model answer
The body temperature is kept at about 37 °C, which is the optimum temperature for the enzymes in the cells. If the temperature falls, the enzyme and substrate molecules move more slowly, there are fewer collisions, and the reactions slow down. If the temperature rises too high, the enzymes are denatured, because the bonds that hold their shape break, and the active site changes, so the substrate no longer fits and the reactions stop. The water content of the blood must also be controlled. Animal cells have no cell wall. If the blood is too dilute, water enters the cells by osmosis and they swell and may burst. If the blood is too concentrated, water leaves the cells by osmosis, and they shrink, so they cannot work properly.
Mark scheme
- Optimum temperature, about 37 °C — 1 mark
- Too cold, slower reactions — 1 mark
- Too hot, enzymes denatured — 1 mark
- Active site changes shape — 1 mark
- Too dilute, cells swell or burst by osmosis — 1 mark
- Too concentrated, cells shrink — 1 mark
Quick check
-
1
What is the optimum temperature of human enzymes?
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C: 37 °C
About 37 °C.
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2
What happens to an enzyme at a very high temperature?
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B: It is denatured
It is denatured, because its shape changes.
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3
Why does a low temperature slow down an enzyme?
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A: There are fewer collisions
There are fewer collisions between enzyme and substrate molecules.
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4
What happens to a red blood cell in a concentrated solution?
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D: It shrinks
Water leaves by osmosis, and the cell shrinks.
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5
What happens to a red blood cell in a dilute solution?
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B: It swells and may burst
Water enters by osmosis, and the cell swells.
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6
Why can animal cells burst in a dilute solution?
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C: They have no cell wall
They have no cell wall.
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7
What is osmosis?
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A: The net movement of water from a dilute to a more concentrated solution across a partially permeable membrane
The net movement of water across a partially permeable membrane from a dilute to a concentrated solution.
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8
A potato cylinder gains mass in a solution. What does this show?
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D: Water entered the cells by osmosis
Water entered the cells by osmosis, so the solution was more dilute than the cytoplasm.
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9
Which term means the control of the water content of the body?
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B: Osmoregulation
Osmoregulation.
Thermoregulation and the Skin
Just this lesson-
1 State [1 mark]
State the part of the brain that coordinates the response to a change in body temperature.
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Model answer
The hypothalamus.
Mark scheme
- Hypothalamus — 1 mark
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2 Describe [2 marks]
Describe the role of the epidermis.
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Model answer
The epidermis is the outer layer of the skin. It forms a barrier that stops pathogens from getting into the body and water from leaving it.
Mark scheme
- Outer layer, a barrier — 1 mark
- Stops pathogens or water loss — 1 mark
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3 Explain [3 marks]
Explain how sweating helps to cool the body.
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Model answer
The sweat glands in the dermis release sweat onto the surface of the skin. The sweat evaporates, and evaporation needs heat energy, which is taken from the skin. So the skin and the body are cooled.
Mark scheme
- Sweat released onto the skin — 1 mark
- Sweat evaporates — 1 mark
- Takes heat from the skin — 1 mark
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4 Explain [3 marks]
Explain why shivering helps to warm the body.
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Model answer
When a person shivers, the muscles contract and relax very quickly. This needs energy from respiration, and respiration in the muscle cells releases heat energy, which warms the body.
Mark scheme
- Muscles contract rapidly — 1 mark
- Respiration in the muscle cells — 1 mark
- Releases heat energy — 1 mark
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5 Describe [4 marks]
Describe the role of the hypothalamus in the control of body temperature.
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Model answer
The hypothalamus has receptors that monitor the temperature of the blood, and it receives impulses from temperature receptors in the skin. It acts as the coordination centre, and compares the temperature with the normal level. It sends impulses to the effectors, such as the sweat glands and the muscles, which respond, so that the temperature returns to about 37 °C.
Mark scheme
- Monitors the temperature of the blood — 1 mark
- Receives impulses from receptors in the skin — 1 mark
- Coordination centre, decides on the response — 1 mark
- Sends impulses to effectors — 1 mark
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6 Evaluate [6 marks]
Explain how the skin and the hypothalamus work together to keep the body temperature at about 37 °C when a person moves from a cold room to a hot room.
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Model answer
The temperature receptors in the skin detect the rise in the temperature of the surroundings, and the hypothalamus detects that the blood is warmer. The hypothalamus is the coordination centre, and it sends impulses to the effectors. The sweat glands in the dermis release more sweat, which evaporates from the skin and takes heat from it, so the body is cooled. The muscles stop shivering, and the hairs lie flat, so less air is trapped and heat can be lost. As the body temperature falls back towards 37 °C, the hypothalamus reduces its signals. The responses reverse the change in temperature, which is negative feedback.
Mark scheme
- Receptors in the skin detect the change — 1 mark
- Hypothalamus is the coordination centre — 1 mark
- Impulses sent to the effectors — 1 mark
- More sweat, which evaporates — 1 mark
- Cooling by taking heat from the skin — 1 mark
- Negative feedback restores the temperature — 1 mark
Quick check
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1
Which part of the brain is the thermostat of the body?
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D: The hypothalamus
The hypothalamus monitors body temperature.
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2
Which layer of the skin contains the sweat glands?
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B: The dermis
The dermis.
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3
How does sweat cool the body?
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A: By evaporating and taking heat from the skin
It evaporates, and takes heat energy from the skin.
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4
Where does the heat in shivering come from?
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C: Respiration in the muscle cells
Respiration in muscle cells.
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5
What do the hairs do when the body is cold?
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B: They stand up and trap air
They stand up, and trap a layer of air.
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6
What is the role of the epidermis?
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D: It is a protective barrier
It is a protective barrier.
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7
Which of these is an effector in thermoregulation?
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A: A sweat gland
A sweat gland carries out the response.
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8
What happens to the sweat glands when the body is cold?
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C: They release little or no sweat
They release little or no sweat.
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9
What type of control is thermoregulation?
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B: Negative feedback
Negative feedback.
Vasoconstriction and Vasodilation (Higher tier)
Just this lesson-
1 State [1 mark]
State what is meant by vasodilation.
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Model answer
The widening of the blood vessels in the skin.
Mark scheme
- Widening of blood vessels — 1 mark
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2 Describe [2 marks]
Describe what happens to the blood vessels in the skin when the body is too cold.
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Model answer
The blood vessels in the dermis get narrower, which is vasoconstriction, so less blood flows near the surface of the skin.
Mark scheme
- Vessels get narrower — 1 mark
- Less blood flows near the surface — 1 mark
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3 Explain [3 marks]
Explain how vasodilation helps to cool the body.
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Model answer
The blood vessels in the skin get wider, so more blood flows close to the surface of the skin. More heat is transferred from the blood to the surroundings, so the body cools.
Mark scheme
- Vessels get wider — 1 mark
- More blood near the surface — 1 mark
- More heat lost to the surroundings — 1 mark
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4 Explain [3 marks]
Explain why the skin of the fingers of a person outside in the snow looks paler than normal.
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Model answer
The hypothalamus detects that the body is cold, and vasoconstriction takes place. The blood vessels in the skin narrow, so less blood flows near the surface, which makes the skin look paler.
Mark scheme
- Vasoconstriction — 1 mark
- Vessels narrow — 1 mark
- Less blood near the skin surface — 1 mark
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5 Explain [4 marks]
Explain the role of the hypothalamus in controlling the diameter of the blood vessels in the skin.
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Model answer
The hypothalamus has receptors that detect the temperature of the blood. If the temperature changes from normal, it sends impulses to the muscles in the walls of the blood vessels in the skin. In the cold, they contract and the vessels narrow, and when it is hot they relax and the vessels widen. The change in heat loss brings the temperature back to normal.
Mark scheme
- Detects the temperature of the blood — 1 mark
- Sends impulses to the muscles in the vessel walls — 1 mark
- Muscles contract or relax, changing the diameter — 1 mark
- Heat loss changes, so the temperature returns to normal — 1 mark
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6 Evaluate [6 marks]
A person goes from a warm room into snow. Explain how the body responds to prevent the body temperature from falling.
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Model answer
Temperature receptors in the skin detect the cold, and the hypothalamus detects that the temperature of the blood has fallen. The hypothalamus sends impulses to the effectors. The muscles in the walls of the blood vessels in the dermis contract, so the vessels narrow. This is vasoconstriction, and it reduces the blood flow near the surface of the skin, so less heat is lost. The skeletal muscles shiver, and respiration in the muscle cells releases heat, which warms the blood. The sweat glands release little sweat, so less heat is lost by evaporation. As the body temperature rises back towards 37 °C, the signals from the hypothalamus are reduced. The responses reverse the change, which is negative feedback.
Mark scheme
- Hypothalamus detects the fall — 1 mark
- Impulses sent to effectors — 1 mark
- Vasoconstriction reduces heat loss — 1 mark
- Shivering releases heat from respiration — 1 mark
- Less sweat — 1 mark
- Negative feedback restores 37 °C — 1 mark
Quick check
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1
What is vasoconstriction?
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B: The narrowing of the blood vessels in the skin
The narrowing of the blood vessels in the skin.
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2
When does vasodilation happen?
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A: When the body is too hot
When the body is too hot.
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3
What does vasodilation do to heat loss?
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C: It increases heat loss
It increases heat loss.
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4
What controls the muscles in the walls of the blood vessels?
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D: Impulses from the hypothalamus
Impulses from the hypothalamus.
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5
Why does the skin look red during vasodilation?
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B: More blood flows near the surface
More blood flows close to the surface.
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6
Why does the skin look pale during vasoconstriction?
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A: Less blood flows near the surface
Less blood flows close to the surface.
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7
Which response warms the body in the cold?
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C: Shivering
Shivering releases heat from respiration.
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8
How is most heat lost from the skin in vasodilation?
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D: It is transferred from the blood to the surroundings
Heat is transferred from the blood to the surroundings.
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9
What type of control is shown by these responses?
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B: Negative feedback
Negative feedback.
Insulin and Blood Glucose
Just this lesson-
1 State [1 mark]
State the name of the organ that releases insulin.
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Model answer
The pancreas.
Mark scheme
- Pancreas — 1 mark
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2 Name [2 marks]
Name the hormone that lowers the blood glucose concentration, and the storage carbohydrate that the liver makes from glucose.
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Model answer
Insulin, and glycogen.
Mark scheme
- Insulin — 1 mark
- Glycogen — 1 mark
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3 Describe [3 marks]
Describe how the blood glucose concentration changes after a person eats a meal, and what the body does in response.
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Model answer
The blood glucose concentration rises after the meal. The pancreas releases insulin, which makes the cells take up glucose, so the blood glucose concentration falls back to normal.
Mark scheme
- Concentration rises — 1 mark
- Pancreas releases insulin — 1 mark
- Cells take up glucose, so the level falls — 1 mark
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4 Explain [3 marks]
Explain why the control of the blood glucose concentration is an example of negative feedback.
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Model answer
When the glucose concentration rises, insulin is released, which makes it fall. When it has returned to normal, less insulin is released. The response reverses the change.
Mark scheme
- Rise triggers insulin — 1 mark
- Insulin makes the concentration fall — 1 mark
- The response reverses the change — 1 mark
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5 Calculate [2 marks]
A person's blood glucose concentration rises to 9.0 mmol per dm³ after a meal. After 3 hours it has fallen to 5.4 mmol per dm³. Calculate the mean rate of fall in mmol per dm³ per hour.
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Model answer
The fall is 3.6 mmol per dm³, and 3.6 divided by 3 is 1.2 mmol per dm³ per hour.
Mark scheme
- 9.0 minus 5.4 is 3.6 — 1 mark
- 1.2 mmol per dm³ per hour — 1 mark
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6 Evaluate [6 marks]
Explain how insulin controls the concentration of glucose in the blood, and why this control is important.
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Model answer
After a meal, carbohydrate is digested to glucose, which is absorbed into the blood, so the blood glucose concentration rises. The pancreas detects the rise, and releases insulin into the blood. Insulin is carried to the liver and the muscles, where it makes the cells take up glucose from the blood. The liver converts the glucose into glycogen, which is stored. The blood glucose concentration falls to its normal level, and the pancreas then releases less insulin, which is negative feedback. This control is important because the cells need a steady supply of glucose for respiration, and if the concentration were too high, water would leave cells by osmosis, and tissues would be damaged.
Mark scheme
- Glucose concentration rises after a meal — 1 mark
- Pancreas detects it and releases insulin — 1 mark
- Cells take up glucose — 1 mark
- Liver converts glucose to glycogen — 1 mark
- Negative feedback, less insulin when normal — 1 mark
- Cells need steady glucose, or osmosis damage — 1 mark
Quick check
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1
Which organ releases insulin?
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C: The pancreas
The pancreas.
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2
What does insulin do?
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B: Lowers the blood glucose
It makes cells take up glucose, lowering the blood glucose concentration.
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3
What does the liver convert glucose into?
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D: Glycogen
Glycogen.
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4
What is the normal blood glucose concentration?
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A: About 5 mmol per dm³
About 5 mmol per dm³.
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5
What happens to the release of insulin when the blood glucose falls to normal?
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C: Less insulin is released
Less insulin is released, which is negative feedback.
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6
What detects a rise in the blood glucose?
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B: Cells in the pancreas
Cells in the pancreas.
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7
Why does the blood glucose rise after a meal?
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A: Carbohydrate is digested to glucose, which is absorbed
Carbohydrate is digested to glucose, which is absorbed.
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8
What is the storage carbohydrate in the liver?
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D: Glycogen
Glycogen.
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9
Which statement about insulin is correct?
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B: It is a hormone carried in the blood
It is a hormone carried in the blood.
Glucagon and Blood Glucose (Higher tier)
Just this lesson-
1 State [1 mark]
State the name of the hormone that increases the blood glucose concentration.
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Model answer
Glucagon.
Mark scheme
- Glucagon — 1 mark
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2 Describe [2 marks]
Describe what glucagon does in the liver.
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Model answer
Glucagon makes the liver convert glycogen into glucose, and the glucose is released into the blood.
Mark scheme
- Glycogen converted to glucose — 1 mark
- Glucose released into the blood — 1 mark
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3 Explain [3 marks]
Explain why glucagon is released from the pancreas during a long period of exercise.
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Model answer
Muscle cells use glucose in respiration, so the blood glucose concentration falls. The cells of the pancreas detect the fall, and release glucagon. Glucagon makes the liver release glucose, so the concentration rises back to normal.
Mark scheme
- Glucose is used in respiration, so it falls — 1 mark
- Pancreas releases glucagon — 1 mark
- Liver releases glucose — 1 mark
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4 Explain [3 marks]
Explain why insulin and glucagon are described as having opposite effects.
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Model answer
Insulin is released when the blood glucose is too high, and it lowers the concentration, by making the cells take up glucose and the liver store it as glycogen. Glucagon is released when the glucose is too low, and raises the concentration, by making the liver release glucose.
Mark scheme
- Insulin lowers the blood glucose — 1 mark
- Glucagon raises the blood glucose — 1 mark
- Released at opposite times — 1 mark
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5 Describe [4 marks]
Describe how the blood glucose concentration of a healthy person changes over a day, and explain the changes.
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Model answer
The concentration rises after each meal, because glucose is absorbed from the digested food, and insulin is then released, which makes the concentration fall. Between meals the concentration falls slightly, below normal, and glucagon is released, which makes the liver release glucose, so the concentration returns to about 5 mmol per dm³.
Mark scheme
- Rises after meals — 1 mark
- Insulin makes it fall — 1 mark
- Falls between meals — 1 mark
- Glucagon makes it rise back to normal — 1 mark
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6 Evaluate [6 marks]
Explain how negative feedback controls the concentration of glucose in the blood, using insulin and glucagon.
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Model answer
If the blood glucose concentration rises, for example after a meal, the pancreas detects it and releases insulin. Insulin makes cells take up glucose, and the liver converts it to glycogen, so the concentration falls back to normal. If the concentration falls too low, for example between meals, the pancreas releases glucagon instead. Glucagon makes the liver convert glycogen to glucose, and release it into the blood, so the concentration rises back to normal. In each case the response reverses the original change, which is negative feedback, and when the concentration is normal, less of each hormone is released.
Mark scheme
- Rise detected, insulin released — 1 mark
- Cells take up glucose, liver stores glycogen — 1 mark
- Fall detected, glucagon released — 1 mark
- Liver converts glycogen to glucose — 1 mark
- Each response reverses the change — 1 mark
- Less hormone released at normal level — 1 mark
Quick check
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1
Which hormone raises the blood glucose concentration?
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D: Glucagon
Glucagon.
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2
Where does glucagon act?
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A: On the liver
On the liver.
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3
What does glucagon make the liver do?
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C: Convert glycogen to glucose
Convert glycogen to glucose.
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4
When is glucagon released?
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B: When the blood glucose is too low
When the blood glucose is too low.
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5
Which organ makes both insulin and glucagon?
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A: The pancreas
The pancreas.
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6
Why do insulin and glucagon have opposite effects?
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D: One lowers and the other raises the blood glucose
One lowers and the other raises the blood glucose concentration.
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7
What happens to the blood glucose during exercise?
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C: It tends to fall
It tends to fall, because muscle cells use glucose in respiration.
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8
What is the storage molecule in the liver?
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B: Glycogen
Glycogen.
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9
What type of control keeps the blood glucose steady?
Show answerHide answer
A: Negative feedback
Negative feedback.
Type 1 and Type 2 Diabetes
Just this lesson-
1 State [1 mark]
State what is meant by type 1 diabetes.
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Model answer
A condition in which the pancreas does not produce enough insulin.
Mark scheme
- Pancreas does not produce enough insulin — 1 mark
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2 Describe [2 marks]
Describe how a person with type 1 diabetes controls their blood glucose concentration.
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Model answer
They inject insulin, and they control their diet, including the carbohydrate that they eat, and take exercise.
Mark scheme
- Inject insulin — 1 mark
- Diet and exercise — 1 mark
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3 Explain [3 marks]
Explain why a person with type 1 diabetes has to inject insulin rather than swallow it.
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Model answer
Insulin is a protein. If it was swallowed, it would be digested by protease enzymes in the stomach and the small intestine, so it would not reach the blood. Injection puts it straight into the blood.
Mark scheme
- Insulin is a protein — 1 mark
- Would be digested — 1 mark
- Injection puts it into the blood — 1 mark
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4 Explain [3 marks]
Explain why a person with type 2 diabetes may have a high blood glucose concentration even though the pancreas makes insulin.
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Model answer
The body cells no longer respond properly to insulin. So the cells do not take up glucose from the blood, and the liver does not store it, so the blood glucose concentration stays high.
Mark scheme
- Cells do not respond to insulin — 1 mark
- Glucose not taken up — 1 mark
- Concentration stays high — 1 mark
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5 Interpret [3 marks]
The graph shows the blood glucose concentration after a meal. Describe two differences between the curve for a person with type 1 diabetes and the curve for a person with no diabetes.
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Model answer
The person with type 1 diabetes has a higher starting concentration, about 10 compared with 5 mmol per dm³, and a higher peak, about 17 compared with 8. After 4 hours, the person with type 1 diabetes is still about 15, while the person with no diabetes has returned to 5.
Mark scheme
- Higher starting concentration — 1 mark
- Higher peak — 1 mark
- Does not return to normal — 1 mark
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6 Evaluate [6 marks]
Compare the causes of type 1 and type 2 diabetes, and evaluate how each is controlled.
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Model answer
In type 1 diabetes, the immune system destroys the cells in the pancreas that make insulin, so the pancreas does not produce enough insulin. In type 2 diabetes, the body cells no longer respond to insulin, and this is linked to obesity and a lack of exercise. Type 1 is controlled by injections of insulin, because insulin is a protein that would be digested if swallowed, together with a controlled diet and exercise. This works well, but the person has to monitor their glucose and inject for life. Type 2 is controlled by a healthy diet, exercise and weight loss, which can reduce the risk and may reverse the condition, and tablets or insulin are used if these are not enough. Type 2 can often be prevented, but type 1 cannot be, because it is not caused by lifestyle.
Mark scheme
- Type 1: insulin-making cells destroyed — 1 mark
- Type 2: cells do not respond, linked to obesity — 1 mark
- Type 1 controlled by insulin, diet, exercise — 1 mark
- Why injection — 1 mark
- Type 2 controlled by diet, exercise and weight loss — 1 mark
- Type 2 can be prevented, type 1 cannot — 1 mark
Quick check
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1
What is the cause of type 1 diabetes?
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B: The pancreas does not produce enough insulin
The pancreas does not produce enough insulin.
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2
What is the cause of type 2 diabetes?
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D: The body cells no longer respond to insulin
The body cells no longer respond to insulin.
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3
How is type 1 diabetes controlled?
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A: By injections of insulin, diet and exercise
By injections of insulin, a healthy diet and exercise.
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4
Why is insulin not taken by mouth?
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C: It would be digested
It is a protein, and would be digested.
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5
What is the main risk factor for type 2 diabetes?
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B: Obesity
Obesity.
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6
Which type of diabetes often starts in childhood?
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A: Type 1
Type 1.
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7
How can type 2 diabetes often be prevented?
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D: A healthy diet and exercise
A healthy diet and exercise.
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8
What happens to the blood glucose in a person with diabetes after a meal?
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C: It rises higher and stays high for longer
It rises higher, and stays high for longer.
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9
What is an insulin pump?
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B: A device that delivers insulin
A device that delivers insulin under the skin.
Body Mass, BMI and Type 2 Diabetes
Just this lesson-
1 State [1 mark]
State the equation used to calculate body mass index (BMI).
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Model answer
BMI = mass in kilograms divided by height in metres squared.
Mark scheme
- Mass (kg) divided by height (m) squared — 1 mark
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2 Calculate [3 marks]
A man has a mass of 95 kg and a height of 1.75 m. Calculate his BMI to 1 decimal place, and state which group he is in.
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Model answer
The height squared is 3.0625, and 95 divided by 3.0625 is 31.0, so he is in the obese group.
Mark scheme
- 1.75 squared is 3.0625 — 1 mark
- 31.0 — 1 mark
- Obese — 1 mark
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3 Calculate [2 marks]
A man has a waist circumference of 106 cm and a hip circumference of 100 cm. Calculate his waist to hip ratio, and state whether it shows a higher risk for a man.
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Model answer
His ratio is 1.06, which is above 0.90, so the risk is higher.
Mark scheme
- 1.06 — 1 mark
- Above 0.90, so higher risk — 1 mark
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4 Describe [2 marks]
Describe the correlation between BMI and the percentage of adults with type 2 diabetes shown in the bar chart.
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Model answer
As the BMI increases, the percentage of adults with type 2 diabetes increases, from 2% for a BMI below 18.5 to 28% for a BMI of 40 and above. This is a positive correlation.
Mark scheme
- Percentage rises as the BMI rises — 1 mark
- Data, such as 2% to 28% — 1 mark
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5 Explain [3 marks]
Explain why a high BMI does not always show that a person is at risk of type 2 diabetes.
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Model answer
BMI only uses the mass and the height. A person with a lot of muscle can have a high BMI but little fat, so the risk of type 2 diabetes may be low. The waist to hip ratio, which shows where the fat is stored, gives extra information.
Mark scheme
- BMI uses only mass and height — 1 mark
- Muscle is not fat — 1 mark
- Waist to hip ratio gives extra information — 1 mark
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6 Evaluate [6 marks]
Evaluate the evidence that a high body mass increases the risk of type 2 diabetes.
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Model answer
Large studies show a positive correlation, as the BMI rises, the percentage of people with type 2 diabetes also rises, for example from 3% to 28% in the data. There is also a possible mechanism, because excess body fat, particularly around the abdomen, makes the cells less sensitive to insulin. The waist to hip ratio shows a similar pattern, and people with type 2 diabetes who lose mass often improve their glucose control. However, a correlation does not prove a cause, because people with a high BMI may also have a poor diet or take little exercise, or carry genes that increase the risk. BMI also does not distinguish muscle from fat, so some people with a high BMI are not at risk. On balance the evidence for a link is strong, but a high mass is one risk factor among several.
Mark scheme
- Positive correlation, with data — 1 mark
- Mechanism: insulin resistance — 1 mark
- Supporting evidence, such as weight loss — 1 mark
- Correlation is not cause — 1 mark
- Other factors, such as diet, exercise and genes — 1 mark
- BMI limits, or a balanced conclusion — 1 mark
Quick check
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1
What is the equation for BMI?
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C: Mass divided by height squared
Mass in kg divided by height in m squared.
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2
A BMI of 32 is in which group?
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D: Obese
30 or more is obese.
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3
What is the BMI of a person with a mass of 60 kg and a height of 1.5 m?
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B: 26.7
60 divided by 2.25 is 26.7.
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4
What does the waist to hip ratio show?
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A: Where the fat is stored
Where the fat is stored.
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5
A woman has a waist to hip ratio of 0.90. What does this show?
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C: A higher risk
It is above 0.85, so the risk is higher.
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6
What is the correlation between BMI and type 2 diabetes?
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B: Positive
Positive: as the BMI rises, the risk rises.
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7
What does a correlation NOT prove?
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D: That one factor causes the other
That one factor causes the other.
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8
Why is BMI limited as a measure of health?
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A: It does not distinguish between muscle and fat
It does not distinguish between muscle and fat.
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9
How does obesity increase the risk of type 2 diabetes?
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B: It can make cells less sensitive to insulin
Excess fat can make cells less sensitive to insulin.