OCR GCSE Biology B (Twenty First Century)
OCR GCSE Biology B B5.4 Why do we need to maintain a constant internal environment? Exam Questions
Free OCR GCSE Biology B exam questions for B5.4 Why do we need to maintain a constant internal environment?, with a mark scheme for every pack. Covers homeostasis, control systems, body temperature regulation, blood glucose control with insulin and glucagon, water balance, the kidney and ADH.
B5.4 Why do we need to maintain a constant internal environment? exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About OCR GCSE Biology B B5.4 Why do we need to maintain a constant internal environment?
B5.4 explains homeostasis: keeping conditions inside the body within narrow limits so that enzymes and cells work properly. You need to describe control systems made of receptors, coordination centres and effectors, and apply them to body temperature, blood glucose and water balance. Insulin and glucagon from the pancreas control blood glucose, and the kidneys, with ADH from the pituitary, control water levels. This topic builds on nerves in B5.2 and hormones in B5.3, and leads to what happens when control fails in B5.6. Examiners like extended explanations of thermoregulation and blood glucose control.
What you need to know
- Homeostasis Homeostasis is the regulation of internal conditions to maintain optimum conditions for enzyme action and cell function despite internal and external changes.
- Control systems Receptors detect changes, coordination centres (brain, spinal cord, pancreas) process information, and effectors (muscles or glands) bring about responses, often by negative feedback.
- Temperature control The thermoregulatory centre in the brain monitors blood temperature. When hot: sweating and vasodilation. When cold: shivering, vasoconstriction and less sweating.
- Blood glucose When blood glucose is high, the pancreas releases insulin, so cells take up glucose and the liver and muscles convert it to glycogen. When low, the pancreas releases glucagon, which causes glycogen to be converted back to glucose.
- Water balance Cells can be damaged if water moves in or out by osmosis. The kidneys filter blood, reabsorb useful substances and the right amount of water, and remove urea in urine.
- ADH If blood is too concentrated, the pituitary releases more ADH, making kidney tubules more permeable so more water is reabsorbed and urine is more concentrated.
Common mistakes in B5.4 Why do we need to maintain a constant internal environment?
- Saying blood vessels move towards the skin surface. Vasodilation widens arterioles so more blood flows near the surface.
- Confusing glucagon and glycogen. Glucagon is a hormone; glycogen is a storage carbohydrate.
- Writing that insulin turns glucose into glycogen. Insulin causes liver and muscle cells to convert glucose to glycogen.
- Stating ADH makes more urine. More ADH means more water reabsorbed, so less, more concentrated urine.
- Saying sweat cools you by being cold. Energy is transferred from the skin to evaporate the water in sweat.
Try three B5.4 Why do we need to maintain a constant internal environment? exam-style questions
1. Name the hormone released when blood glucose concentration is too low. (1 mark)
Show the mark scheme answer
Glucagon.
2. A person's blood glucose rises from 5.0 mmol per dm3 to 8.5 mmol per dm3 after a meal. Calculate the percentage increase. (2 marks)
Show the mark scheme answer
Increase = 3.5; 3.5 / 5.0 x 100 = 70%.
3. Explain how the body responds when its core temperature rises. (4 marks)
Show the mark scheme answer
The thermoregulatory centre in the brain detects the rise; sweat glands produce more sweat, which evaporates and transfers energy from the skin; arterioles near the skin dilate (vasodilation); more blood flows near the surface so more energy is transferred to the surroundings.
B5.4 Why do we need to maintain a constant internal environment? FAQs
What does OCR GCSE Biology B B5.4 cover?
It covers homeostasis and control systems, temperature regulation, blood glucose control by insulin and glucagon, and water balance by the kidneys and ADH.
Which paper is B5.4 examined in?
J257 has two papers at each tier, Breadth in Biology and Depth in Biology, and content from any chapter, including B5, can be assessed on either one. Expect it to be linked to ideas about science and to other chapters.
How do I stop mixing up glucagon and glycogen?
Remember glucaGON is the hormone released when glucose is GONe, and glycogen is the stored carbohydrate in the liver and muscles.
