GCSE Combined Science Biology — Questions and Answers
Question 1: Which organelle is responsible for aerobic respiration in animal cells?
- Nucleus
- Ribosome
- Mitochondria (Correct answer)
- Cell membrane
Correct answer: Mitochondria
Mitochondria are the site of aerobic respiration, where glucose and oxygen react to release energy (as ATP). They are sometimes called the 'powerhouses' of the cell. Active cells like muscle cells contain more mitochondria.
Question 2: What is the word equation for photosynthesis?
- Glucose + oxygen → carbon dioxide + water
- Carbon dioxide + water → glucose + oxygen (Correct answer)
- Glucose → ethanol + carbon dioxide
- Oxygen + glucose → lactic acid
Correct answer: Carbon dioxide + water → glucose + oxygen
Photosynthesis converts carbon dioxide and water into glucose and oxygen, using light energy absorbed by chlorophyll. This process occurs in the chloroplasts of plant cells and is essential for producing food and releasing oxygen.
Question 3: In the human digestive system, where does most absorption of nutrients occur?
- Stomach
- Large intestine
- Small intestine (Correct answer)
- Oesophagus
Correct answer: Small intestine
The small intestine is the main site of nutrient absorption. Its inner surface has millions of villi, which increase the surface area enormously. Villi have thin walls and a rich blood supply for efficient absorption.
Question 4: What type of cell division produces genetically identical daughter cells?
- Meiosis
- Mitosis (Correct answer)
- Binary fission
- Fertilisation
Correct answer: Mitosis
Mitosis produces two genetically identical daughter cells from one parent cell. It is used for growth, repair, and asexual reproduction. Each daughter cell has the same number of chromosomes as the parent cell.
Question 5: Which of the following best describes the role of white blood cells in the immune system?
- They carry oxygen around the body
- They help blood to clot at wound sites
- They defend against pathogens by producing antibodies and engulfing microorganisms (Correct answer)
- They transport dissolved nutrients
Correct answer: They defend against pathogens by producing antibodies and engulfing microorganisms
White blood cells defend the body against infection. Phagocytes engulf and digest pathogens, while lymphocytes produce specific antibodies that lock onto antigens on the surface of pathogens, marking them for destruction.
Question 6: A plant hormone called auxin causes shoots to grow towards light. What is this response called?
- Gravitropism
- Phototropism (Correct answer)
- Hydrotropism
- Thigmotropism
Correct answer: Phototropism
Phototropism is the growth response of a plant towards or away from light. Auxin accumulates on the shaded side of the shoot, causing cells there to elongate more, bending the shoot towards the light source.
GCSE Combined Science Biology
Which organelle is responsible for aerobic respiration in animal cells?