Topic – 6.1
(a) (i) State the word equation for photosynthesis.
(ii) State the name of the green pigment that is needed for photosynthesis.
(b) A student investigated the rate of photosynthesis at different temperatures in potato plants.
Fig. 1.1 shows the results of the investigation.
Using the information in Fig. 1.1:
(i) State a temperature when the rate of photosynthesis is 30 arbitrary units.
(ii) State the rate of photosynthesis when the temperature is 15°C.
(iii) Describe the effect of increasing temperature on the rate of photosynthesis in potato plants.
(c) (i) Potato cells contain starch. State one use of starch in potato cells.
(ii) Starch is a large molecule made from many glucose molecules. State the name of one other carbohydrate that is found in plants and is made from glucose molecules.
(iii) Glucose can be combined with ions to make amino acids in plants. State the name of the ions needed to make amino acids.
(d) Photosynthesis is one process of the carbon cycle. State two other processes of the carbon cycle.
▶️ Answer/Explanation
Ans:
(a)(i) The word equation for photosynthesis is: \[ \text{carbon dioxide + water} \rightarrow \text{glucose + oxygen} \]
(a)(ii) The green pigment required is chlorophyll, which absorbs light energy.
(b)(i) From the graph, photosynthesis reaches 30 units at 17°C and 35°C.
(b)(ii) At 15°C, the rate is 21 ± 0.5 arbitrary units.
(b)(iii) The rate increases up to an optimum (24°C), then declines due to enzyme denaturation.
(c)(i) Starch acts as an energy store in potato cells.
(c)(ii) Another glucose-based carbohydrate is cellulose (for cell walls).
(c)(iii) Nitrate ions are combined with glucose to form amino acids.
(d) Other carbon cycle processes include respiration and combustion.
Topic – 7.3
(a) (i) Physical digestion by teeth breaks down food into smaller pieces. Explain the importance of food being physically broken down into smaller pieces.
(ii) State the name of one other part of the digestive system where physical digestion occurs in humans.
(b) (i) There are different types of human teeth. The boxes on the left contain diagrams of different types of human teeth. The boxes on the right contain the names of the types of human teeth. Draw one straight line from each box on the left to a box on the right to match each tooth to its name. Draw three lines.
(ii) Describe the function of molar teeth.
(c) Fig. 2.1 is a diagram of a human tooth.
State the names of the parts labelled A, B, C and D in Fig. 2.1.
▶️ Answer/Explanation
Ans:
(a)(i) Breaking food into smaller pieces increases surface area for enzymes to act, speeding up chemical digestion. For example, amylase works more efficiently on smaller starch particles.
(a)(ii) The stomach performs physical digestion through churning and mixing actions.
(b)(i) Correct tooth matches:
(b)(ii) Molars grind and crush food into a paste-like consistency for swallowing.
(c) Tooth structure labels:
A: Enamel (hard outer layer)
B: Dentine (bony tissue beneath enamel)
C: Pulp (contains nerves and blood vessels)
D: Cement (anchors tooth to jawbone)
Topic – 8.2
Fig. 3.1 is a photomicrograph of a section through the stem of a plant.
(a) Use a label line and label to identify and name a structure that transports sucrose in Fig. 3.1.
(b) Complete the sentences about water uptake in a plant using words or phrases from the list. You may use the words or phrases once, more than once or not at all.
active transport cuticle mesophyll osmosis photosynthesis respiration root cortex root hair stomata transpiration
Plants absorb water molecules from the soil through …………. cells by the process of …………. Water molecules then move into …………. cells and then into the xylem. From the xylem, the water molecules move into …………. cells in the leaf. Water vapour diffuses out of the leaves through the …………. The loss of water vapour from leaves is called …………. .
▶️ Answer/Explanation
Ans:
(a)
The structure that transports sucrose is the phloem, as shown in the labeled diagram below:
(b)
Plants absorb water molecules from the soil through root hair cells by the process of osmosis. Water molecules then move into root cortex cells and then into the xylem. From the xylem, the water molecules move into mesophyll cells in the leaf. Water vapour diffuses out of the leaves through the stomata. The loss of water vapour from leaves is called transpiration.
Detailed Explanation:
Part (a): The phloem is responsible for transporting sucrose and other organic nutrients in plants. It is identified in the photomicrograph as a distinct vascular tissue.
Part (b): Water uptake follows a specific pathway:
1. Root hair cells absorb water via osmosis due to their high surface area.
2. Water moves into the root cortex and then into the xylem for upward transport.
3. In leaves, water enters mesophyll cells and evaporates, exiting through stomata in a process called transpiration.
Topic – 9.2
(a) Complete the description of the human circulatory system. The circulatory system is a system of blood vessels with a ………. and ………. to ensure one‑way flow of blood.
(b) A student investigated the resting heart rate in people of different ages. The student recorded the heart rate as the number of beats per minute (bpm).
(i) The student wore a watch that could monitor their heart rate. State two other methods that can be used to monitor heart rate.
(ii) Table 4.1 shows the results of the investigation.
Tick (✓) two correct conclusions that can be drawn from the data shown in Table 4.1.
(c) A 38‑year‑old person had a resting heart rate of 72bpm. The person exercised for 10 minutes. At the end of exercise their heart rate was 170bpm. Calculate the percentage change in heart rate from the beginning to the end of exercise for the 38‑year‑old. Give your answer to the nearest whole number. Space for working.
(d) A lack of physical activity is one factor that can increase the risk of coronary heart disease. Diet also has a role in the risk of coronary heart disease. Discuss the role of diet in reducing the risk of coronary heart disease.
▶️ Answer/Explanation
Ans:
(a) The circulatory system consists of blood vessels with a pump (heart) and valves to ensure one-way blood flow. The heart propels blood, while valves prevent backflow.
(b)(i) Two alternative methods to monitor heart rate:
- Measuring pulse rate (e.g., at the wrist or neck).
- Using an electrocardiogram (ECG) to detect electrical activity.
(b)(ii) Correct conclusions (✓):
- Resting heart rate decreases until age 40, then increases.
- From ages 5 to 10, heart rate decreases by 25 bpm.
(c) Percentage change calculation:
- Change = 170 bpm – 72 bpm = 98 bpm.
- Percentage change = \(\left(\frac{98}{72}\right) \times 100 \approx 136\%\).
(d) Diet’s role in reducing coronary heart disease risk:
- Low saturated fats: Reduces LDL cholesterol, preventing artery plaque.
- High fiber: Lowers blood cholesterol levels.
- Limited salt/sugar: Controls blood pressure and obesity risks.
- Antioxidant-rich foods: Protect blood vessels from damage.
Topic – 17.4
(a) The melanin gene in humans codes for a pigment produced in the skin, hair and eyes.
(i) Describe what is meant by the term gene.
(ii) State the name of a cell structure in humans that contains genes.
(b) Albinism is a genetic condition where there is a mutation in the gene that produces melanin. People with albinism have very pale skin, hair and eyes. In a population, 1 in 18000 are people with albinism. Calculate how many people with albinism would be expected in a population of 270000 people.
(c) The allele for normal melanin production is dominant and is represented by the letter A. The allele for albinism is recessive and is represented by the letter a. Fig. 5.1 is a pedigree diagram showing the inheritance of albinism in one family.
(i) State the sex chromosomes for person 1 in Fig. 5.1.
(ii) State how many people in Fig. 5.1 have albinism.
(iii) Circle the correct description of the genotype of person 3 in Fig. 5.1.
heterozygous homozygous dominant homozygous recessive
(d) An unaffected person has a child with a person with albinism. Complete the genetic diagram to show the possible genotypes and phenotypes of this child also the ratio of unaffected people:people with albinism.
▶️ Answer/Explanation
Ans:
(a)(i) a length of DNA ; that codes for a protein
A gene is a segment of DNA that carries instructions for synthesizing a specific protein, determining traits like melanin production.
(a)(ii) nucleus
Genes are located on chromosomes, which are housed in the nucleus of eukaryotic cells.
(b) 15 (people)
Calculation: \( \frac{270000}{18000} = 15 \). In a population of 270,000, 15 individuals are expected to have albinism based on the given frequency.
(c)(i) XX
Person 1 is female (indicated by the circle in the pedigree diagram), so their sex chromosomes are XX.
(c)(ii) 4
Four individuals in the pedigree (shaded circles/squares) exhibit the phenotype for albinism.
(c)(iii) homozygous recessive
Person 3 has albinism (shaded square), so their genotype must be homozygous recessive (aa).
(d) parental gametes: A a × a a ;
offspring genotypes: Aa (Aa) aa (aa) ;
offspring phenotypes: unaffected (unaffected) albinism (albinism) ;
ratio 1:1
An unaffected parent (Aa) and a parent with albinism (aa) can produce offspring with either genotype Aa (unaffected) or aa (albinism) in a 1:1 ratio.
Topic – 21.2
(a) (i) Fig. 6.1 is a diagram of a bacterial cell.
Complete Fig. 6.1 by using the words in the list to label these structures on the answer lines provided.
- cell membrane
- cell wall
- circular DNA
- cytoplasm
- ribosome
(ii) State the names of two structures in the cell in Fig. 6.1 that are not found in animal cells.
(iii) Describe the function of plasmids in bacterial cells.
(b) Many sewage treatment plants use bacteria in the process of cleaning sewage. Some of these bacteria release methane as a waste product. This methane can be burned as a source of energy for the sewage treatment plant. Explain why the production and use of methane in this way is described as sustainable.
(c) Sometimes untreated sewage enters water ecosystems. Describe the effects of untreated sewage on river ecosystems.
▶️ Answer/Explanation
Ans:
(a)(i) The labeled bacterial cell structures are:
(a)(ii) Two structures not found in animal cells: cell wall and circular DNA (or plasmids).
(a)(iii) Plasmids store extra genetic material and enable gene transfer between bacteria, aiding adaptation (e.g., antibiotic resistance).
(b) Methane production is sustainable because it is continuously generated by bacteria during sewage treatment and serves as a renewable energy source when burned.
(c) Untreated sewage depletes oxygen, kills aquatic life, spreads diseases, and disrupts food chains, reducing biodiversity.
Final Answers:
(a)(i) See labeled diagram above.
(a)(ii) Cell wall, circular DNA/plasmids.
(a)(iii) Gene storage/transfer.
(b) Renewable and continuously produced.
(c) Oxygen depletion, biodiversity loss, disease spread.
Topic – 14.4
(a) The human body must maintain a constant internal environment.
(i) State the term used to describe the maintenance of a constant internal environment.
(ii) Secretion of hormones by endocrine glands is one way that a constant internal environment is maintained.
Fig. 7.1 shows the locations of some endocrine glands and some organs in the human body.
Table 7.1 shows some of the names of the endocrine glands, the hormones they secrete, their functions and their letters from Fig. 7.1.
(b) State how hormones secreted by an endocrine gland reach their target organ.
(c) (i) The nervous system also helps the body to maintain a constant internal environment. Complete Table 7.2 to compare nervous and hormonal control
(ii) State one type of neurone found in a reflex arc.
▶️ Answer/Explanation
Ans:
(a)(i) Homeostasis – the process by which the body maintains a stable internal environment despite external changes.
(a)(ii) The completed table matches endocrine glands (e.g., pancreas, adrenal glands) with their hormones (insulin, adrenaline) and functions (regulating blood sugar, fight-or-flight response).
(b) Hormones travel through the bloodstream to reach their target organs.
(c)(i) Nervous control is fast and short-lived (e.g., reflexes), while hormonal control is slower but longer-lasting (e.g., growth regulation).
(c)(ii) Sensory, relay, or motor neurones are found in a reflex arc, transmitting signals rapidly for quick responses.
Topic – 16.3
A student carefully took a fuchsia flower apart. Fig. 8.1 is a photograph of the parts of the flower.
State the function of each of the parts labelled A to D in Fig. 8.1.
▶️ Answer/Explanation
Ans:
A: Attracts insects or pollinators, aiding in the transfer of pollen for fertilization.
B: Contains the female sex cells (ovules), which develop into seeds after fertilization.
C: Produces and releases male gametes (pollen), essential for fertilizing the ovules.
D: Receives pollen grains during pollination, facilitating fertilization.
These structures work together to ensure successful sexual reproduction in flowering plants.