1 Diagram 1 shows an anatomical drawing of a horse. Which of **A**, **B**, **C** and **D** shows the anatomical direction of the posterior part? flag bookmark A A B B C C D D T4 Chapter 1.3 Communicating in Biology In a four-legged animal, posterior means towards the tail end, so it is direction C. A is anterior (head end), B is dorsal (back) and D is ventral (belly side).
2 Which component of an animal cell has two layers of membrane? flag bookmark A Ribosome B Mitochondrion C Golgi apparatus D Plasma membrane T4 Chapter 2.1 Cell structure and function A mitochondrion is surrounded by a double membrane: a smooth outer membrane and a folded inner membrane (cristae). Ribosomes have no membrane, and the Golgi apparatus and plasma membrane are made of a single membrane.
3 Diagram 2 shows the structure of a plant cell. Which structure **A**, **B**, **C** or **D** acts as a medium for biochemical reactions in the cell? flag bookmark A A B B C C D D T4 Chapter 2.1 Cell structure and function A is the cytoplasm. It is a jelly-like medium that contains water, dissolved substances and enzymes, and most biochemical reactions of the cell happen in it. B is the nucleus, C is the vacuole (tonoplast) and D is the cell wall.
4 Diagram 3 shows Visking tubing containing 10% sucrose solution. After 20 minutes, the volume of the Visking tubing decreases. What is solution K? flag bookmark A Distilled water B 20% sucrose solution C 10% sucrose solution D 5% sucrose solution T4 Chapter 3.3 Movement of Substances Across a Plasma Membrane in Living Organisms The Visking tubing became smaller, so water moved out of it by osmosis. This happens when the solution outside is hypertonic, i.e. more concentrated than 10% sucrose. So K is the 20% sucrose solution. Distilled water and 5% sucrose would make the tubing swell, and 10% sucrose would cause no change.
5 Diagram 4 shows the movement of substances across a plasma membrane. Which of the following is a movement of substances across the plasma membrane as shown in Diagram 4? flag bookmark A Gaseous exchange between an alveolus and blood capillary B Reabsorption of water through the renal tubule in the kidney C Transport of sucrose from leaf to phloem tissue D Absorption of fructose molecules in villus T4 Chapter 3.3 Movement of Substances Across a Plasma Membrane in Living Organisms The diagram shows a carrier protein using ATP to move molecules across the membrane, which is active transport. Sucrose is loaded from leaf cells into the phloem sieve tubes by active transport, against its concentration gradient. Gaseous exchange is simple diffusion, water reabsorption is osmosis, and fructose is absorbed by facilitated diffusion.
6 During a field trip to the mangrove swamp, Ahmad collected a soil sample from the area to pot a chilli plant. After a few days, he found that the plant had wilted. What is the process that happens to the plant cells and what should Ahmad do to help the wilted plant? | | Process | Action | |---|---|---| | A | Haemolysis | Put the plant under the sunlight | | B | Crenation | Add chemical fertiliser to the soil | | C | Plasmolysis | Add more water to the soil | | D | Deplasmolysis | Add some sand to the soil | flag bookmark A Haemolysis – Put the plant under the sunlight B Crenation – Add chemical fertiliser to the soil C Plasmolysis – Add more water to the soil D Deplasmolysis – Add some sand to the soil T4 Chapter 3.4 Movement of Substances Across a Plasma Membrane and Its Application in Daily Life Mangrove soil is very salty, so the soil water is hypertonic to the root cells. Water leaves the plant cells by osmosis and they become plasmolysed, so the plant wilts. Adding more water dilutes the salt so that the plant cells can take in water again. Haemolysis and crenation happen to red blood cells, not plant cells.
7 Diagram 5 shows the formation of a chromosome from DNA. What is X? flag bookmark A DNA B Histone C Nucleosome D Chromosome T4 Chapter 6.1 Cell Division In a chromosome, the long DNA molecule is wound around ball-shaped protein cores called histones; DNA wrapped around histones forms nucleosomes, which coil further to form the chromosome. According to the answer scheme, the structure X labels is the histone.
8 The following statement is about enzyme activity. > Enzyme activity can be slowed down or stopped by enzyme inhibitors. Which of the following is an enzyme inhibitor? flag bookmark A Magnesium ion B Vitamin B C Nitrogen D Mercury T4 Chapter 5.2 Enzyme Heavy metals such as mercury and lead are enzyme inhibitors: they bind to the enzyme and change the shape of its active site, so the substrate can no longer fit. Magnesium ions and B vitamins actually help many enzymes work (as cofactors and coenzymes).
9 Diagram 6 shows a cell cycle. What happens during phase Q? flag bookmark A Replication of DNA B Energy is stored C Spindle fibres are formed D Number of cellular components increases T4 Chapter 6.2 Cell Cycle and Mitosis The cycle goes from the M phase to P (G₁), then Q (S phase) and R (G₂) before the next M phase. In the S phase, DNA is replicated so that each chromosome has two sister chromatids. Cell components increase in G₁, and energy is stored in G₂.
10 A student carried out an activity as shown in Diagram 7. Which of the following is correct? | | Mixture A | Gas B | Mixture A after 24 hours | |---|---|---|---| | A | Yeast + boiled glucose solution | Carbon dioxide | Yeast + ethanol | | B | Boiled yeast + boiled glucose solution | Oxygen | Yeast + glucose solution + ethanol | | C | Yeast + glucose solution | Oxygen | Yeast + lactic acid | | D | Boiled yeast + glucose solution | Carbon dioxide | Yeast + water | flag bookmark A Yeast + boiled glucose solution – Carbon dioxide – Yeast + ethanol B Boiled yeast + boiled glucose solution – Oxygen – Yeast + glucose solution + ethanol C Yeast + glucose solution – Oxygen – Yeast + lactic acid D Boiled yeast + glucose solution – Carbon dioxide – Yeast + water T4 Chapter 7.3 Fermentation The glucose solution is boiled to remove dissolved oxygen, and paraffin oil stops air from entering, so the living yeast carries out fermentation. Yeast breaks down glucose into ethanol and carbon dioxide; the carbon dioxide (gas B) inflates the balloon. Boiled yeast is dead and cannot ferment, and yeast does not produce lactic acid.