Respiration
What is the difference between aerobic and anaerobic respiration in terms of energy yield?
Aerobic respiration releases much more energy than anaerobic respiration because glucose is fully broken down.
Why is a lack of iron more dangerous for a teenager than for a small child?
Teenagers need more iron to produce haemoglobin for growth and menstruation (in girls), so deficiency affects them more.
Why are stomata usually on the underside of the leaf?
To reduce water loss from evaporation because it’s cooler and shadier.
Why do root hair cells not have chloroplasts?
Because they are underground and don’t receive light, so they don’t photosynthesise.
Why do we heat the leaf in ethanol during the starch test?
To remove the chlorophyll so the colour change from iodine can be clearly seen.
Why do muscles get tired after anaerobic respiration?
Because lactic acid builds up, which lowers pH and interferes with muscle function.
Why is fibre important in the diet even though it gives no energy?
It keeps the digestive system healthy by preventing constipation and helping food move through the gut.
Why do plants need nitrates from the soil even though they make their own food?
Nitrates are needed to make proteins for growth and enzymes.
How is the sperm cell adapted to carry out its function?
It has a tail for movement, many mitochondria for energy, and enzymes in the head to penetrate the egg.
What does a positive Benedict’s test look like, and what does it show?
Brick-red colour means reducing sugar is present.
Why is it important that mitochondria have a folded inner membrane?
It increases the surface area for enzymes that help in respiration, making it more efficient.
What would happen if you ate too much protein?
Excess protein gets broken down in the liver and excreted, which puts strain on the kidneys.
What would happen to photosynthesis if a plant was kept in green light?
It would slow down because chlorophyll doesn’t absorb green light well.
What is the function of the vacuole in a plant cell?
It stores sap and helps keep the cell firm (turgid).
Why is 37°C used in the enzyme experiment?
Because it’s body temperature, the optimum temperature for enzymes like amylase.
How is the carbon dioxide from respiration removed from the body?
It’s carried in the blood to the lungs and then exhaled.
Why do athletes need more carbohydrates than the average person?
Carbohydrates provide glucose for respiration, which fuels muscle activity.
How do insect-pollinated flowers differ from wind-pollinated ones in structure?
Insect-pollinated flowers have bright petals, scent, nectar, and sticky pollen; wind-pollinated ones have small petals, no scent, and light pollen.
Why do muscle cells have more mitochondria than skin cells?
Muscle cells need more energy for contraction, so they need more mitochondria for respiration.
In the CO₂ balloon yeast experiment, how could you prove the gas is CO₂?
Bubble it through limewater and see if it turns cloudy.
Explain how yeast can be used in both baking and brewing, even though the products are different.
In both cases, yeast does anaerobic respiration (fermentation). It produces CO₂ for bread rising and alcohol for brewing.
Compare the roles of Vitamin C and Vitamin D in the body.
Vitamin C helps with immune function and wound healing; Vitamin D helps absorb calcium for healthy bones.
Explain how deforestation could indirectly reduce oxygen levels in the atmosphere.
Fewer trees mean less photosynthesis, so less oxygen is produced and less carbon dioxide is removed.
If a cell has lots of rough ER and Golgi bodies, what might it be specialised for?
Producing and packaging proteins — like a gland cell that secretes enzymes or hormones.
In the potato osmosis experiment, why might the potato lose mass in salt water?
Water moves out of the potato cells into the salt solution because it’s more concentrated.