SIR MICHELANGELO REFALO CENTRE FOR FURTHER STUDIES VICTORIA GOZO Half-Yearly Exam 2013 Subject: BIOLOGY Level: INT 1 st Yr Time: 2hrs Name: Course: Year: SECTION A: Answer ALL questions in this section in the space provided below. 1. This question is about Chemicals of Life. The following are two organic molecules: a. Identify them: A - B - (2 marks) b. Give one function of each in the human body. A - B - (2 marks) c. Water is a very important chemical of life. List TWO physical or chemical properties of water and explain how they affect the functioning of living organisms. (4 marks) Page 1 of 10
d. By which process does water move into and out of cells? e. How does the size of a molecule influence its solubility? f. Why are lipids, rather than proteins or carbohydrates, utilized as stores of energy in living organisms? (2 marks) g. Name the three different bonds which join the building units of: carbohydrates: lipids: and proteins:. (3 marks) (Total: 15 marks) 2. This question concerns Cell Biology. a. What is a cell? Describe the main features found in nearly all cells. (3 marks) b. Define an organelle. c. List three major differences between prokaryotic and eukaryotic cells. (6 marks) Page 2 of 10
d. Arrange the following structures in increasing order of size: cells; cell membranes; molecules; bacteria; viruses; organelles (3 marks) e. Name one major group of organisms that are characterized by prokaryotic cells. f. Briefly describe one function of the following structures of prokaryotic cells: Slime capsule: Flagellum: Plasmid: Ribosomes: (6 marks) (Total: 20 marks) 3. The table below contains description of the structure and / or function of various organelles that are characteristic of eukaryotic cells. Fill the blank spaces in the table with the name of the organelle that best matches each description. Description Organelle Organelle that transports and chemically modifies the materials contained within it. It is particularly important in secretory cells. Organelle surrounded by an envelope of two membranes and contains a gel-like stroma through which runs a system of membranes that are stacked in places to form grana. Very small organelles consisting of a large and a small subunit. Organelle surrounded by an envelope of two membranes, the inner being folded to form cristae. Page 3 of 10
Large organelle enclosed by an envelope of two membranes that is perforated by pores. Contains chromatin. Organelles composed of a simple spherical sac bounded by a single membrane and containing digestive enzymes. Their functions are all concerned with breakdown of structures and molecules. Partially permeable barrier controlling exchange between cell and its external environment. 1 mark each (Total: 7 marks) 4. The diagrams below show cross sections of two different types of blood vessels arteries and capillaries. Note that the diagrams are not to scale. a. i. Identify ONE structural characteristic visible in the diagram of the artery and state how this characteristic enables to perform its function. (2 marks) ii. Identify ONE structural characteristic visible in the diagram of the capillary and state ONE function that this characteristic enables the capillary to perform. (2 marks) b. In the diagram below, figure A shows a normal vein with healthy values, while figure B shows a varicose vein with weak valves. Compare the blood flow in a normal vein and a varicose vein. Give a reason for your answer. Page 4 of 10
(2 marks) c. i. Name ONE blood component found in higher concentrations in a vein than in an artery. ii. Name ONE substance that can cause the narrowing of an artery. (Total: 8 marks) 5. Infectious diseases are one of the principal sources of mortality in several developing countries. 5.1 What is an infectious disease? 5.2 The immune system of the human body constitutes a defence against disease. Two components of the immune system of humans are phagocytic leucocytes and antibodies. Briefly describe the role of both in maintaining immunity against disease. Phagocytic leucocytes: Antibodies: (3 marks) Page 5 of 10
5.3 Suggest TWO reasons as to why humans still suffer from disease despite the presence of an immune system. (2 marks) 5.4 Antibiotics and vaccines represent two factors that may strengthen the immune system of the body. Distinguish between antibiotics and vaccines. (2 marks) 5.5 Many medical researchers recommend that antibiotics should not be administered as frequently as they are now. Suggest ONE reason for such a recommendation. 5.6 A person can catch cold several times in the space of a few months. Suggest ONE reason as to why no effective vaccine has ever been developed against the common cold. (Total: 10 marks) 6. This question is concerned with transport in and out of cells. 6.1 Define the term simple diffusion. 6.2 The rate of diffusion through a membrane is proportional to: surface area x difference in concentration thickness of membrane Page 6 of 10
Predict whether the values of each of these three variables will be high or low when the rate of diffusion through the membrane is at a maximum: Surface area: Difference in concentration: Thickness of membrane: (3 marks) 6.3 List TWO examples of simple diffusion in biological systems. The outer layer of cells on a young root is called the epidermis. Root epidermal cells absorb water and mineral ions from the soil solution. The graph below shows the relative concentration of magnesium, nitrate and phosphate ions in the epidermal cells of a plant root and in the soil solution that is in direct contact with the epidermal cells. 6.4 Using the information from the graph, by which process, do you think, plants take up mineral ions from the soil into their roots? 6.5 What do you predict would happen to the concentration of ions inside the cells if the root epidermal cells were treated with a respiratory poison such as cyanide? (Total: 7 marks) Page 7 of 10
7. Aerobic respiration and anaerobic respiration may be viewed as biochemical pathways that recharge ATP. 7.1 What is the importance of ATP for living organisms? 7.2 How do aerobic and anaerobic respiration compare in their production of ATP? 7.3 In what part of the cell does anaerobic respiration take place? (0.5 mark) 7.4 In what part of the cell does aerobic respiration take place? (0.5 mark) 7.5 In the space provided below, make a large diagram of a mitochondrion to show its structure as seen under the electron microscope and label the sites where the phases of aerobic respiration occur. (5 marks) (Total: 8 marks) Page 8 of 10
SECTION B: Answer only ONE question from this section. This section carries 25 marks. Your answer to Section B should be written on the separate answer booklet provided. 8. This question is concerned with the digestive system of the human body. 8.1 Draw a large, clearly labelled diagram of the digestive system of a human. (5 marks) Describe the role of each of the following structures or processes in digestion: 8.2 digestive enzymes; 8.3 villi; 8.4 the liver; 8.5 chewing of food. (20 marks) (Total: 25 marks) 9. The diagrams below illustrate how the rate of an enzyme-controlled reaction varies with: (i) temperature, (ii) ph, (iii) substrate concentration and (iv) the concentration on an inhibitor. a. For each graph, explain as fully as you can the reasons for the relationship shown between the y and the x axis. (5,5,5,4) Page 9 of 10
b. Enzymes play an important role in digestion. Choose one amylase and one protease found in the human digestive tract and for each one name: i. the site of production, ii. site of action, iii. the substrate, iv. the products, v. the optimum ph conditions, You can present your answer in the form of a table. (6 marks) (Total: 25 marks) 10. Give an account of photosynthetic processes in green plants. Refer to the following in your answer: 10.1 relation of leaf structure to its function in photosynthesis; (10 marks) 10.2 the role of chlorophylls and other photosynthetic pigments; (10 marks) 10.3 the light-dependent and light-independent reactions of photosynthesis (5 marks) (Total: 25 marks) GOOD LUCK! Page 10 of 10