1 Diagram 1 shows human body planes. Which of the planes labelled **A**, **B** and **C** is the sagittal plane? flag bookmark A A B B C C T4 Chapter 1.3 Communicating in Biology The sagittal plane is a vertical plane that divides the body into left and right parts. Plane A runs from front to back through the middle of the body, so it is the sagittal plane. Plane B is horizontal (transverse plane) and plane C divides the body into front and back parts (frontal plane).
2 Diagram 2 shows a unicellular organism, *Paramecium* sp. What is the reproduction process shown in Diagram 2? flag bookmark A Budding B Conjugation C Binary fission D Spore formation T4 Chapter 2.2 Living Processes in Unicellular Organisms The diagram shows one *Paramecium* dividing across the middle into two identical daughter cells. This is binary fission. Conjugation involves two cells joining to exchange genetic material, which is not shown.
3 Diagram 3 shows the structure of plasma membrane. What is structure X? flag bookmark A Glycolipid B Cholesterol C Glycoprotein D Phospholipid T4 Chapter 3.1 Structure of Plasma Membrane Structure X is a protein embedded in the membrane with a carbohydrate chain attached to it, so it is a glycoprotein. A glycolipid has the carbohydrate chain attached to a lipid instead of a protein.
4 Diagram 4 shows the movement of substance X across the plasma membrane. Which of the following describes the movement of substance X? flag bookmark A Simple diffusion B Facilitated diffusion C Active transport D Passive transport T4 Chapter 3.2 Concept of Movement of Substances Across a Plasma Membrane Substance X moves from a region of low concentration to a region of high concentration, which is against the concentration gradient. This needs energy from ATP and carrier proteins, so it is active transport. Diffusion (simple or facilitated) and other passive transport only move substances down the concentration gradient.
5 Diagram 5 shows the breakdown process of a triglyceride molecule. What is process X? flag bookmark A Deamination B Hydrolysis C Condensation D Assimilation T4 Chapter 4.4 Lipids Three water molecules are used to break the triglyceride into one glycerol and three fatty acids. Breaking down a molecule by adding water is hydrolysis. Condensation is the reverse process, which joins molecules and releases water.
6 Diagram 6 shows an experiment to investigate pepsin activity. The test tube contains a mixture of 1 ml of 1% pepsin solution, 2 ml of 1% albumen suspension and 5 drops of dilute hydrochloric acid. What should be done to reduce the time taken for the mixture to turn clear? flag bookmark A Add 5 drops of dilute sodium hydroxide solution B Decrease the concentration of pepsin to 0.5% C Increase the temperature of water bath to 37°C D Add rennin into the mixture T4 Chapter 5.2 Enzyme The water bath is at 25 °C. Pepsin works best at body temperature, about 37 °C, so raising the temperature to 37 °C makes pepsin digest the albumen faster and the mixture turns clear sooner. Adding sodium hydroxide raises the pH away from pepsin's acidic optimum, a lower pepsin concentration slows the reaction, and rennin acts on milk protein, not albumen.
7 Diagram 7 shows a preservation method of cucumber to make it last longer. This method takes one month to complete the preservation process. Which of the following can shorten the time for the preservation process? flag bookmark A Replace with a fresher cucumber B Replace with a bigger jar C Replace with a smaller size cucumber D Replace the solution with less concentrated solution T4 Chapter 3.4 Movement of Substances Across a Plasma Membrane and Its Application in Daily Life The cucumber is preserved in a concentrated (hypertonic) solution, so water leaves the cucumber cells by osmosis. A smaller cucumber has a larger total surface area to volume ratio, so osmosis happens faster and the process takes less time. A less concentrated solution would slow down water loss.
8 Diagram 8 shows a cell cycle. In which phase does the replication of DNA occur? flag bookmark A G₁ B S C G₂ D M T4 Chapter 6.2 Cell Cycle and Mitosis DNA replication happens in the S (synthesis) phase of interphase, so each chromosome becomes two sister chromatids. G₁ and G₂ are growth phases, and M is mitosis.
9 The following information shows the characteristics of a child with genetic disorder. - Slanted eyes - Mental retardation - Protruding tongue What is the cause of this genetic disorder? flag bookmark A Synapsis did not occur during prophase I B Cytokinesis did not occur during telophase II C Nucleus membrane did not form during telophase II D Sister chromatids did not separate during anaphase II T4 Chapter 6.4 Issues of Cell Division on Human Health These are the features of Down syndrome, which is caused by an extra chromosome 21. It happens because of non-disjunction during meiosis, for example when sister chromatids fail to separate during anaphase II, so a gamete gets two copies of chromosome 21.
10 The following information describes energy production by yeast. > Alcohol fermentation is a process to generate ATP without utilizing oxygen. Which of the following equations is correct to describe the process? flag bookmark A Glucose →(zymase) Ethanol + Carbon dioxide + 210 kJ B Glucose →(zymase) Lactic acid + 210 kJ C Glucose →(zymase) Ethanol + Lactic acid + 150 kJ D Glucose →(zymase) Ethanol + Water + 210 kJ T4 Chapter 7.3 Fermentation In alcoholic fermentation, yeast uses the enzyme zymase to break down glucose into ethanol and carbon dioxide, releasing a small amount of energy (210 kJ). Lactic acid is made in lactic acid fermentation in muscles, not by yeast, and water is not a product of fermentation.