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Grade 12 Biology national exam, 2013 E.C. (2021 G.C.)

95 questions · 120 minutes. The first 5 answers are shown with explanations; sit the whole paper timed in the app to get your score and the textbook page behind every question.

1. 1.Which one of the following is true about the importance of Lucy in resolving debates about human evolution?
   • A. Big brains came before bipedalism.
   • B. Lucy had a brain size of 1.8% of her body mass.
   • C. Bipedalism came before big brains.
   • D. Lucy was partially an arboreal primate.
   Answer: C. The discovery of Lucy (Australopithecus afarensis) was pivotal because she had a small, ape-like brain but walked upright, proving that bipedalism evolved before large brains in human evolution. Textbook: Grade 12, unit 4 · section 4.1.5.
2. 2.Which one of the following can best explain behavior? It is
   • A. the co-ordinated response of an organism to an internal or external stimuli.
   • B. the tendency for parts of plants to grow towards light.
   • C. the actions or reactions of a person or animal in response to external or internal stimuli.
   • D. a cell or group of cells that receives and processes stimuli.
   Answer: A. Behavior is the coordinated response of an organism to internal or external stimuli. Option A gives this broad meaning of behavior. B is wrong because it describes only plant growth towards light; C is narrower because it refers to actions or reactions of people or animals; D is wrong because it describes a receptor, a cell or group of cells that detects and processes stimuli. Textbook: Grade 11, unit 2 · section 2.5.1.
3. 3.The quick withdrawal of your hand from a hot plate is an example of
   • A. fixed action pattern
   • B. innate behavior
   • C. biological clock
   • D. key stimulus
   Answer: B. The key idea is that an innate behaviour is present without being learned. Quickly pulling a hand away from a hot plate is an inborn protective response. A fixed action pattern is a specific sequence of behaviour; a biological clock controls timing; and a key stimulus is a signal that triggers a response, not the response itself. Textbook: Grade 11, unit 2 · section 2.5.1.
4. 4.Which one of the following processes describes a biological clock?
   • A. Removal of one's thumb from hot objects quickly
   • B. The growing of plants towards light
   • C. Circannual migration of birds from temperate to tropical areas
   • D. Kinesis and taxes of woodlice and other simple animals
   Answer: C. A biological clock is an internal timing system that helps an organism respond to regular time patterns. Bird migration that repeats each year is a circannual rhythm, so C describes a biological clock. A is a quick reflex, not a yearly timing pattern. B is growth toward light, and D describes movement responses to environmental conditions. Textbook: Grade 9, unit 6 · section 6.1.5.
5. 5.Identify learned behavior from the following.
   • A. Dog trained to hunt.
   • B. Honey bee making honey.
   • C. Child withdraws hand from hot things.
   • D. Ants making nest.
   Answer: A. The question tests the difference between learned and innate behavior. A dog trained to hunt learns the behavior through experience or training. B, C, and D describe behaviors that are not learned by training. Textbook: Grade 11, unit 2 · section 2.5.1.
6. 6.Which one of the following features is unique to bacteria?
   • A. Presence of permeable membrane
   • B. Being unicellular
   • C. Absence of nuclear membrane
   • D. Having flagella for locomotion
   Answer, explanation and textbook page: open in the app.
7. 7.This item is based on the diagram which shows the different shape of bacteria below. What is the correct name of the shape of bacteria represented by letters A, B, and C, respectively?
   
   • A. Rod, spirochaete, sphere
   • B. Sphere, rod, spirochaete
   • C. Flagellated bacilli, clusters, spirilla
   • D. Spirochaete, sphere, rod
   Answer, explanation and textbook page: open in the app.
8. 8.It is possible to produce human insulin in a bacterial strain. The insulin gene should be inserted in a plasmid and the recombinant DNA plasmid should be inserted into a bacterium. What is the role of the bacterium in this process?
   • A. The source of insulin and modification
   • B. The source of plasmid and insulin production
   • C. Multiplying the recombinant DNA molecule
   • D. Joining the gene of insulin with the gene of plasmid
   Answer, explanation and textbook page: open in the app.
9. 9.Bacteria can cause diseases in all of the following mechanisms EXCEPT
   • A. changing the genetic structure of host cells.
   • B. entering living cells and disrupting metabolic systems.
   • C. releasing toxins as they multiply.
   • D. invading and growing on the tissues of organs.
   Answer, explanation and textbook page: open in the app.
10. 10.Functional diseases differ from infectious diseases in that they
    • A. are caused by microorganisms.
    • B. occur in the brain and heart.
    • C. are common in females than males.
    • D. show no signs of damage on the organ.
    Answer, explanation and textbook page: open in the app.
11. 11.This item is based on the drawing of a bacteriophage given below. In the above diagram of a bacteriophage, DNA and Protein coat are respectively represented by
    
    • A. 2 and 3.
    • B. 1 and 3.
    • C. 1 and 2.
    • D. 2 and 1.
    Answer, explanation and textbook page: open in the app.
12. 12.The social impact of AIDS can be mainly revealed by
    • A. fear of stigmatization
    • B. loss of appetite
    • C. reduced labor force
    • D. loss of body weight
    Answer, explanation and textbook page: open in the app.
13. 13.Which one of the following is a DNA virus?
    • A. Herpes complex
    • B. HIV
    • C. Hepatitis C
    • D. H1N1
    Answer, explanation and textbook page: open in the app.
14. 14.Which one of the following is a correct comparison of lytic and lysogenic cycles of virus multiplication?
    • A. Lysogenic cycle releases new viruses using only chronic cycle.
    • B. Lytic cycle involves incorporation of viral DNA into the host DNA.
    • C. Lytic cycle releases new viruses only by splitting the host cell.
    • D. Both cycles damage the host cell DNA following infection.
    Answer, explanation and textbook page: open in the app.

1. 15.Which student do you think is correct?
   • A. Student B
   • B. Student A
   • C. Student D
   • D. Student C
   Answer, explanation and textbook page: open in the app.
2. 16.Which event of cellular respiration takes place in the cytoplasm eukaryotic cells?
   • A. Production of pyruvate from glucose
   • B. Reaction of acetyl CoA with oxaloacetate
   • C. Production of ATP through chemiosmosis
   • D. Reaction of pyruvate with coenzyme A
   Answer, explanation and textbook page: open in the app.
3. 17.Suppose two moles of glucose is burned aerobically. How many moles of ATP can be produced by substrate level phosphorylation in Krebs cycle?
   • A. 4
   • B. 6
   • C. 10
   • D. 8
   Answer, explanation and textbook page: open in the app.
4. 18.During alcoholic fermentation, is released when
   • A. acetaldehyde is reduced.
   • B. pyruvate is oxidized.
   • C. pyruvate is decarboxylated.
   • D. ethanol is oxidized.
   Answer, explanation and textbook page: open in the app.
5. 19.During anaerobic respiration, reduced NAD is required to
   • A. split pyruvate to $\mathrm{CO_2}$ and acetaldehyde.
   • B. reduce pyruvate to lactate.
   • C. convert lactate into pyruvate.
   • D. reduce pyruvate to acetyl CoA.
   Answer, explanation and textbook page: open in the app.
6. 20.Why do we get tired and fatigued during heavy exercise such as long distance running? It is due to
   • A. accumulation of $\mathrm{CO_2}$.
   • B. accumulation of lactic acid.
   • C. high rate of aerobic respiration.
   • D. shortage of glucose.
   Answer, explanation and textbook page: open in the app.
7. 21.If one base in the six triplets of the gene coding for one of the four polypeptides in the haemoglobin molecule alters the triplet from GAG to GTG, which one of the following biological terms best describes the above phenomenon?
   • A. Mutation
   • B. Cloning
   • C. Translation
   • D. Transcription
   Answer, explanation and textbook page: open in the app.
8. 22.Which one of the following is the basic characteristic of mutation? It is
   • A. spontaneous.
   • B. planned.
   • C. regular.
   • D. expected.
   Answer, explanation and textbook page: open in the app.
9. 23.The theory that suggests "life can evolve autonomously from non-living objects" is known as
   • A. cosmozoan theory.
   • B. spontaneous generation theory.
   • C. biochemical theory.
   • D. eternity theory.
   Answer, explanation and textbook page: open in the app.
10. 24.Which one of the following is true about neo-Darwinian theory?
    • A. There is a natural variation in features and variations which are heritable.
    • B. All species tend to produce more offspring than can possibly survive.
    • C. It takes into account genetics and animal behavior to understand evolution.
    • D. Development of new feature is important for survival.
    Answer, explanation and textbook page: open in the app.
11. 25.Which one of the following statements describes the evolutionary theory of Lamarck?
    • A. Acquired characteristics cannot be inherited.
    • B. Structures commonly used become more developed.
    • C. Origin of species happens only through natural selection.
    • D. Species started complex and gradually become simple.
    Answer, explanation and textbook page: open in the app.
12. 26.The behavior which trainers look, if modified, could lead to the desired behavior and reward such a behavior is
    • A. innate.
    • B. instinct.
    • C. reflex.
    • D. operant.
    Answer, explanation and textbook page: open in the app.
13. 27.Which one of the following examples of behavior describes when an animal stops responding to stimulus or cue after a period of repeated exposure?
    • A. Imprinting
    • B. Reflex
    • C. Habituation
    • D. Conditioning
    Answer, explanation and textbook page: open in the app.
14. 28.A police man trained a dog on how to find explosive materials through sniffing, on another instant the same police man observed a week old puppy following him on the roadside. Which one of the following is correct about the behaviors of the animals in the observation?
    • A. The first case is genetically encoded and the second is adaptive
    • B. Both of the cases indicate natural behavior of the animals
    • C. Both of the cases indicate learned behavior of the animals
    • D. The first case develops through trial and the second is genetically coded
    Answer, explanation and textbook page: open in the app.
15. 29.The Ethiopian wolf (Canis simensis) lives and hunt in packs. During patrolling their habitat, both male and female wolves of the group maintain their area with urine containing pheromone. This pattern of behavior best exemplifies
    • A. courtship behavior.
    • B. territorial behavior.
    • C. operant behavior.
    • D. learned behavior.
    Answer, explanation and textbook page: open in the app.
16. 30.The terrestrial biome characterized by cold temperature, dry precipitation, frozen soil and inhabited by migrating birds is
    • A. boreal forests.
    • B. deserts
    • C. tropical montane forests.
    • D. tundra.
    Answer, explanation and textbook page: open in the app.
17. 31.This item is based on the table below. Biome Soil Animals Desert (hot) L M Tropical montane forest N O Select the correct representatives for L, M, N and 0, respectively
    • A. Fertile, many animals, poor, few animals
    • B. Poor, sparse, fertile, many animals
    • C. Fertile, migratory animals, poor, drought and fire adapting animals
    • D. Medium, ants and spiders, poor, polar bears
    Answer, explanation and textbook page: open in the app.
18. 32.Which one of the following explains biodiversity?
    • A. The variability among living organisms, within species, and of ecosystem
    • B. The large number of human races in the world
    • C. The similarity and difference of organisms which live in different ecosystems
    • D. Large number of organisms in the same ecosystem
    Answer, explanation and textbook page: open in the app.
19. 33.This item is based on the table below which shows an 'invented' ecosystems. Number of organisms of each species Species Area 1 Area 2 Area 3 A 86 16 23 B 5 17 25 C 2 16 27 D 3 17 5 E 1 17 12 F 3 17 8 In which area of the above table does all of the species are more or less equally successful?
    • A. Area 2
    • B. Area 1
    • C. Area 1 and 3
    • D. Area 1 and 2
    Answer, explanation and textbook page: open in the app.
20. 34.What is the major difference that viruses have with free living cells? Viruses
    • A. reproduce only asexually.
    • B. lack genetic material of their own.
    • C. do not function outside of a living cell.
    • D. lack locomotary structure.
    Answer, explanation and textbook page: open in the app.
21. 35.A major factor in controlling the population size that helps to minimize predators and recover prey's number is
    • A. Disease-causing organisms
    • B. Inter-specific competition
    • C. Predation
    • D. Intra-specific competition
    Answer, explanation and textbook page: open in the app.
22. 36.Which one of the following orders of life processes correctly illustrates occurrence of the nutrient cycle?
    • A. feeding → death and decomposition → excretion → respiration and breathing
    • B. feeding → excretion → respiration and breathing → death and decomposition
    • C. death and decomposition → feeding → excretion → respiration and breathing
    • D. respiration and breathing → feeding → excretion → death and decomposition
    Answer, explanation and textbook page: open in the app.
23. 37.Which of the following processes in the phosphate cycle DOES NOT return phosphate ions to the soil?
    • A. Weathering of rocks
    • B. Use of fertilizers
    • C. Decomposition of dead animals
    • D. Cellular respiration
    Answer, explanation and textbook page: open in the app.
24. 38.A previously bare land was gradually occupied by lichen and mosses, annual herbs, perennial herbs, shrubs and finally by forests. Which one of the following best describes the process indicated above?
    • A. Afforestation
    • B. Succession
    • C. Climax community
    • D. Natural Selection
    Answer, explanation and textbook page: open in the app.
25. 39.This item is based on the table below. Condition Population size Natality exceeds mortality X Mortality exceeds natality Y Mortality and natality are equal Z The population number of X, Y, and Z, respectively will
    • A. decrease, increase, remain the same.
    • B. increase, decrease, remain the same.
    • C. decrease, remains the same, increase
    • D. remain the same, increase, decrease.
    Answer, explanation and textbook page: open in the app.
26. 40.This item is based on the table below which shows population growth trend. Time period Numbers in population X Numbers in population Y 0 5 40 1 10 80 2 15 160 3 20 320 4 25 640 5 30 1280 6 35 2560 7 40 5120 Which one of the following is correct about X and Y?
    • A. X is exponential growth because the numbers increase by the same fixed amount in each time period and Y is arithmetic growth because the population doubles in each time period.
    • B. X and Y cannot be compared because each of them grow differently with incomparable proportion.
    • C. X is arithmetic growth because the numbers increase by the same fixed amount in each time period and Y is exponential growth because the population doubles in each time period.
    • D. Both X and Y are exponential growth since each of them increase regularly without interruption.
    Answer, explanation and textbook page: open in the app.
27. 41.Drosophila melanogaster are convenient experimental animals in genetics. Because they
    • A. have 23 pairs of chromosomes per cell.
    • B. are small animals with a short life cycle.
    • C. are too cheap to breed in large numbers.
    • D. have chromosomes that can't be easily detected,
    Answer, explanation and textbook page: open in the app.
28. 42.This item is based on the table below which shows population growth trend. Which one of the following is correct about X and Y?
    
    • A. X is exponential growth because the numbers increase by the same fixed amount in each time period and Y is arithmetic growth because the population doubles in each time period
    • B. X and Y cannot be compared because each of them grows differently with incomparable proportions
    • C. X is arithmetic growth because the numbers increase by the same fixed amount in each time period and Y is exponential growth because the population doubles in each time period
    • D. Both X and Y are exponential growth since each of them increases regularly without interruption
    Answer, explanation and textbook page: open in the app.

1. 43.Nothing else is drawn or labelled; a small 'Scanned with CamScanner' watermark sits at the bottom left of the image.]
   
   • A. X involves cross breeding and Z involves inbreeding.
   • B. X involves inbreeding and Z involves cross breeding.
   • C. X represents natural selection and Z represents artificial selection.
   • D. Both X and Z represent inbreeding.
   Answer, explanation and textbook page: open in the app.
2. 44.If organisms share very similar molecules such as DNA, then they must be closely related evolutionarily. Which evidence of evolution supports the above information?
   • A. Comparative embryology
   • B. Comparative anatomy
   • C. Comparative physiology
   • D. Comparative biochemistry
   Answer, explanation and textbook page: open in the app.
3. 45.Which one of the following CANNOT be used as an evidence of evolution through paleontology?
   • A. Stomach
   • B. Teeth
   • C. Hair
   • D. Bones
   Answer, explanation and textbook page: open in the app.
4. 46.The process in which individuals with a particular heritable trait survive better than the other is
   • A. adaptation.
   • B. evolution.
   • C. selective breeding.
   • D. natural selection,
   Answer, explanation and textbook page: open in the app.
5. 47.Which type of selection favors individuals at both extremes of a range to have some advantage over these displaying the mean value?
   • A. Stabilizing selection
   • B. Directional selection
   • C. Natural selection
   • D. Disruptive selection
   Answer, explanation and textbook page: open in the app.
6. 48.Which one of the following is true about the human evolution?
   • A. Humans and chimpanzees both evolved from a common ancestor.
   • B. Humans evolved from chimpanzees.
   • C. Humans evolved from different line of evolution than great apes.
   • D. Humans evolved from great apes.
   Answer, explanation and textbook page: open in the app.
7. 49.Which one of the following organic molecules is used to make haemoglobin?
   • A. Glycogen
   • B. Lipids
   • C. Proteins
   • D. Nucleic acids
   Answer, explanation and textbook page: open in the app.
8. 50.Which one of the following is the correct formula of maltose?
   • A. $C_6H_{12}O_6$
   • B. $C_{12}H_{24}O_{12}$
   • C. $C_5H_{10}O_5$
   • D. $C_{12}H_{22}O_{11}$
   Answer, explanation and textbook page: open in the app.
9. 51.A grade 11 student added Benedict's reagent on food sample and heated the mixture for 5 minutes. Then he observed a color change. Which one of the following is FALSE about the result?
   • A. An orange colour shows that a reducing sugar is present.
   • B. A yellow colour shows that a reducing sugar is present.
   • C. An orange colour shows that a non-reducing sugar is present.
   • D. A red colour shows that a reducing sugar is present.
   Answer, explanation and textbook page: open in the app.
10. 52.In a Benedict's test for sucrose, why does the test sample first boil with hydrochloric acid?
    • A. To reduce Benedict's solution
    • B. To neutralize the solution
    • C. To hydrolyze non-reducing sugar
    • D. To retest the mixture with Benedict's solution
    Answer, explanation and textbook page: open in the app.
11. 53.Which one of the following statements explains the specificity of enzymes? Enzymes
    • A. catalyse one reaction only.
    • B. speed up a reaction without being used up.
    • C. can be destroyed by excessive heat.
    • D. can be used over and over again.
    Answer, explanation and textbook page: open in the app.
12. 54.The relevance and promise of biological sciences can be demonstrated by their contribution in
    • A. finding mechanisms to feed the growing human population.
    • B. finding solutions to ethnic conflicts.
    • C. development of housing and construction sectors.
    • D. advancement of aviation technology.
    Answer, explanation and textbook page: open in the app.
13. 55.All are the roles of biology to combat the spread of HIV/AIDS EXCEPT
    • A. producing drugs that can stop the virus from reproducing
    • B. breaking the transmission pathway.
    • C. raising fund for infected people.
    • D. producing a vaccine against the virus.
    Answer, explanation and textbook page: open in the app.
14. 56.Which one of the following statements is INCORRECT about AIDS? The rate of transmission of AIDS will reduce when
    • A. the transmission path ways is broken.
    • B. promiscuous sexual intercourse is reduced.
    • C. the number of sexual partners is restricted.
    • D. men and women are circumcised.
    Answer, explanation and textbook page: open in the app.
15. 57.Which one of the following statements explains the property of water? It
    • A. takes less energy to heat water up.
    • B. has the lowest latent heat of vaporization.
    • C. is a transparent molecule.
    • D. is highly viscous substance.
    Answer, explanation and textbook page: open in the app.
16. 58.Suppose there are two communities in a village. Community A actively participates in HIV/AIDS awareness creation, HIV prevention and gets blood test for HIV whereas community B frequently requests for food aid, participates only in afforestation activities and HIV positive individuals keep the secret to themselves. In which community do you think that the incidence of HIV/AIDS most probably high?
    • A. In both communities
    • B. In community B
    • C. Impossible to decide
    • D. In community A
    Answer, explanation and textbook page: open in the app.
17. 59.Which property of water is useful for life that it continues in relatively warm water underneath through the cold weather?
    • A. High specific heat capacity
    • B. High density in its solid form than its liquid form
    • C. High surface tension
    • D. High latent heat of vaporization
    Answer, explanation and textbook page: open in the app.
18. 60.Consider the following table which contains organic and inorganic molecules. Which rows contain the corresponding organic and inorganic molecules correctly? No Organic Molecules Inorganic Molecules 1 Lysine, surcose Salts, hydrochloric acid 2 Deoxyribose, carbon monoxide Fructose, sodium chloride 3 Fatty acid, methane Sodium hydroxide, carbon dioxide 4 Water, calcium carbonate Stearic acid, starch Which rows contain the corresponding organic and inorganic molecules correctly?
    
    • A. 2 and 3
    • B. 1 and 2
    • C. 3 and 4
    • D. 1 and 3
    Answer, explanation and textbook page: open in the app.
19. 61.Cellulose is
    • A. a mixture of amylose and amylopectin.
    • B. a polymer of -glucose molecule. β
    • C. a non-reducing monosaccharide sugar.
    • D. a polymer of -glucose molecule. α
    Answer, explanation and textbook page: open in the app.
20. 62.Which organic molecules are formed when two fatty acid molecules are bounded to the glycerol and the place of the third is taken by a phosphate group?
    • A. Waxes
    • B. Glycolipids
    • C. Triglycerides
    • D. Phospholipids
    Answer, explanation and textbook page: open in the app.
21. 63.All are the function of lipids EXCEPT
    • A. thermal insulation.
    • B. water proofing.
    • C. respiratory substrates
    • D. determines a particular features.
    Answer, explanation and textbook page: open in the app.
22. 64.Three different cells are in the process of transporting materials across the cell membrane as indicated below: Na+ Cell 1 = water from high concentration to low concentration Cell 2 = from high concentration to low concentration Cell 3 = glucose form low concentration to high concentration Which types of transport mechanism do the above cells use, respectively?
    • A. Osmosis, facilitated diffusion, active transport
    • B. Osmosis, active transport, facilitated diffusion
    • C. Facilitated diffusion, osmosis, active transport
    • D. Facilitated diffusion, active transport, osmosis
    Answer, explanation and textbook page: open in the app.
23. 65.Suppose you took a container and divided it into two halves by a membrane which is permeable to water and labeled the two halves as A and B. Finally, you added hypertonic solution in A and hypotonic solution in B. What will be the expected result of this experiment?
    • A. Rise of the water level in both halves
    • B. Rise of the water level in B
    • C. Rise of the water level in A
    • D. No change in both halves
    Answer, explanation and textbook page: open in the app.
24. 66.A student did an experiment and found out that catabolism of amino acid produces toxic ammonia in the liver cells which gradually get converted into urea and excreted through urine. What would be the result of the experiment if osmosis was blocked? The liver cells
    • A. gain water and become turgid.
    • B. excrete more ammonia and urea.
    • C. become over active and produce more energy.
    • D. become damaged and lose functionality.
    Answer, explanation and textbook page: open in the app.
25. 67.Consider the following key events in the study of cell biology. I. Hooke describes 'cells' in a cork. II. Leeuwenhoek discovers protozoa. III. Schleiden and Schwann propose a cell theory. IV. Jansen builds the first compound microscope. Which one of the following represents the correct order from ancient to the recent?
    • A. I, II, III and IV
    • B. IV, I, II and II
    • C. III, II, I and IV
    • D. II, III, IV and I
    Answer, explanation and textbook page: open in the app.
26. 68.One of the differences of prokaryotic and eukaryotic cells is their cell wall. This is because cell wall of prokaryotic cell is
    • A. the site of energy production.
    • B. impermeable.
    • C. stronger than eukaryotic cells.
    • D. made from sugar and amino acid.
    Answer, explanation and textbook page: open in the app.
27. 69.Consider the following features of cells. I. have pili II. have chromosome III have circular DNA IV. have larger ribosomes Which of the above features of cells can be included in eukaryotic cells?
    • A. II and III
    • B. I and II
    • C. II and IV
    • D. I and III
    Answer, explanation and textbook page: open in the app.
28. 70.Which of the following is correct about the structure of the cell membrane?
    • A. Phospholipid molecules form a transport channel.
    • B. Protein molecules form a double layer.
    • C. The membrane has a fluid nature that is regulated by cholesterol.
    • D. Proteins form the outer layer while phospholipids form the inner layer.
    Answer, explanation and textbook page: open in the app.
29. 71.Which of the following is a correct match of cellular organelles and their corresponding function?
    • A. Vacuole strength and elasticity
    • B. Mitochondria - ATP synthesis
    • C. Lysosome - modification of proteins
    • D. Golgi body - digesting foreign cells
    Answer, explanation and textbook page: open in the app.
30. 72.What structural arrangements make chlorophyll suit for its function?
    • A. The floating of the photosystems and the electron transport chain in the cytosol.
    • B. The fixing of the photosystems and the electron transport chain on thylakoid membrane.
    • C. The structural differences between Photosystem I and Photosystem II.
    • D. The long distance between Photosystem I and Photosystem I.
    Answer, explanation and textbook page: open in the app.
31. 73.Why does photorespiration take place in a hot environment? Because plants close their stomata and face H O 2 CO 2 O
    • A. shortage
    • B. shortage.
    • C. accumulation.
    • D. shortage 2 O 2
    Answer, explanation and textbook page: open in the app.

1. 74.The scan is low contrast with faint text bleeding through from the reverse of the page and a small 'Scanned with CamScanner' watermark at the bottom left.]
   
   • A. D and F
   • B. C and E
   • C. B and A
   • D. F and E
   Answer, explanation and textbook page: open in the app.
2. 75.Which of the following is correct about the process of glucose production in the light-independent reactions of photosynthesis?
   • A. A total of 9 ATP molecules are synthesized.
   • B. CO$_2$ reacts with GP to form RuBP.
   • C. One TP is directly converted to one glucose molecule.
   • D. GP is reduced to TP by reduced NADP.
   Answer, explanation and textbook page: open in the app.
3. 76.Which of the following is a correct description of the CAM pathway of photosynthesis?
   • A. $\mathrm{CO_2}$ is stored in the form of malate during the night.
   • B. The Calvin cycle takes place during the night.
   • C. The Calvin cycle takes place in the bundle sheath cells during the day.
   • D. $\mathrm{CO_2}$ is stored in the bundle sheath cells during the night.
   Answer, explanation and textbook page: open in the app.
4. 77.Which one of the following statements explains how an enzyme lowers the activation energy of a reaction? By
   • A. enabling the reaction to occur at lower physiological temperature
   • B. making the individual substrate molecules more reactive
   • C. lowering the kinetic energy of the reacting molecules
   • D. changing its tertiary structure into secondary protein structure
   Answer, explanation and textbook page: open in the app.
5. 78.Consider the following chemical reaction below. Based on the above chemical reaction, in which classes of enzymes can enzyme "E" be grouped? + 2 A RH 2
   • A. Transferases
   • B. Hydrolyases
   • C. Isomerases
   • D. Oxidoreductases
   Answer, explanation and textbook page: open in the app.
6. 79.Which one of the following enzymes is used as washing powders?
   • A. Biochymosin
   • B. Lipase
   • C. Cellulase
   • D. Pectinase
   Answer, explanation and textbook page: open in the app.
7. 80.What happens when the substrate molecule binds to the active site or an enzyme?
   • A. The substrate and the enzyme will bond permanently.
   • B. They form a stable intermediate substance.
   • C. The amino acids in the active site become unreactive.
   • D. The chemical bonds of the substrate distorted.
   Answer, explanation and textbook page: open in the app.
8. 81.How does crossing over during meiosis bring variation in species? By
   • A. increasing the amount of genes in one of the parents during meiosis
   • B. combination of genes in the gametes that are not found in either parent
   • C. combining sex and somatic cell chromosomes
   • D. creating genes that are not found in both parents due to meiosis
   Answer, explanation and textbook page: open in the app.
9. 82.How does our body synthesize some of the amino acids in our body? From
   • A. fatty acids we consume
   • B. intermediate molecules of different path ways
   • C. breaking down of pre-existing proteins
   • D. biological breakdown of our own cells
   Answer, explanation and textbook page: open in the app.
10. 83.This item is based on the following list of events during cloning of an insulin gene into plasmid. I. Obtaining insulin producing cells and plasmid from organisms II. Cutting the insulin gene and plasmid III. X IV Inserting the recombinant plasmid into bacteria V. Production of insulin by bacteria Which one of the following best represents the step listed as "X"?
    • A. Inserting the insulin gene into a bacterium
    • B. Inserting the open plasmid into a bacterium
    • C. Fusing the insulin and plasmid genes to the cell wall of bacteria
    • D. Combining the insulin gene into the opened plasmid
    Answer, explanation and textbook page: open in the app.
11. 84.Consider the DNA molecule containing: Strand 1: T A C G T A Strand 2: A T G C A T What will be the sequence of the new DNA if the DNA replicates semi-conservatively?
    • A. ATGCAT UACGUA
    • B. TACGTA ATGCAU
    • C. ATGCAT ATGCAT
    • D. TACGTA ATGCAT
    Answer, explanation and textbook page: open in the app.
12. 85.During translation the
    • A. tRNA serves as a template of the DNA molecule.
    • B. ribosome moves forward over two codons at a time.
    • C. mRNA brings amino acids into the ribosomes.
    • D. tRNA with complementary anticodon binds on the codon of mRNA.
    Answer, explanation and textbook page: open in the app.
13. 86.The step of scientific method which comes after analyzing results and draw conclusion is
    • A. doing background research.
    • B. constructing hypothesis.
    • C. designing and carrying out experiment.
    • D. accepting or rejecting the hypothesis.
    Answer, explanation and textbook page: open in the app.
14. 87.In a group of individuals in which group A was a control and group B was an experimental group, a student gave a placebo to the control group, and an unknown drug to the experimental group. At the end, the experimental group got better. Which one of the following is true about the result?
    • A. The drug has an effect.
    • B. Placebo has better effect.
    • C. The experiment was wrong.
    • D. Conclusion cannot be reached.
    Answer, explanation and textbook page: open in the app.
15. 88.A biologist conducted simple experiment to investigate the effect of pH on salivary amylase. She added 5 cm3 amylase solution into starch suspension with a neutral pH in a test tube. After ten minutes, she tested it with iodine reagent and the solution turned into blue-black color. What is the dependent variable of this experiment?
    • A. Applying iodine treatment
    • B. pH of the solution
    • C. Adding salivary amylase
    • D. Formation of blue-black color
    Answer, explanation and textbook page: open in the app.
16. 89.Which one of the following pairs of biological tools and their functions is FALSE?
    • A. Petri dish -used for culturing microorganisms
    • B. Balances-used for measuring mass
    • C. Quadrate- to separate solids from liquids
    • D. Optical microscope- use beam of light to produce magnified image
    Answer, explanation and textbook page: open in the app.
17. 90.Grade 12 students went to a field and collected plant specimens for identification in the laboratory. They wanted to preserve the plant parts for some times and specimens can be analyzed later. Which one of the following biological tool is used for their activities?
    • A. Plant press
    • B. Pitfall traps
    • C. Theodolite
    • D. Quadrat
    Answer, explanation and textbook page: open in the app.
18. 91.Some amino acids are synthesized using transamination process in the cell. This activity more describes the cell's
    • A. replication.
    • B. catabolism.
    • C. energy production.
    • D. anabolism.
    Answer, explanation and textbook page: open in the app.
19. 92.Identify the statement that correctly explains the factors of an enzyme activity.
    • A. Excessive heat breaks the ionic bonds that hold the tertiary structure of the enzyme protein.
    • B. Hydrogen ion concentration affects the ionic bonds of an enzyme.
    • C. Increasing concentration of substrates does not affect enzyme activity.
    • D. Inhibitors increase enzyme activity by increasing their turnover rate.
    Answer, explanation and textbook page: open in the app.
20. 93.Which one of the following is true about allosteric regulation?
    • A. Enzymes are activated when activators attached on the active site.
    • B. Inhibition by competitive inhibitors when it interacts on the allosteric site.
    • C. Activation by activators when it interacts on the allosteric site.
    • D. Allosteric inhibition is occurred when inhibitors attached on the active site.
    Answer, explanation and textbook page: open in the app.
21. 94.If an enzyme from thermophilic bacteria, which catalyses glucose 6- phosphate into fructose 6-phosphate in the process of glycolysis, is subjected to below the optimum temperature, the rate of reaction will be decreased. This is because
    • A. the particles have more kinetic energy
    • B. the enzyme is denatured.
    • C. more collisions between enzyme and glucose 6-phosphate occurred.
    • D. less enzyme - glucose 6-phosphate complexes formed.
    Answer, explanation and textbook page: open in the app.
22. 95.Cyclooxygenase-2 is an enzyme that catalyzes the conversion of arachidonic acid to prostaglandins, which promote pain and fever in our body. The pain killer ibuprofen, act as non-competitive inhibitor of cyclooxygenase-2, reduces the production of prostaglandins. What would happen if the concentration of the ibuprofen increased?
    • A. Pain of the body is decreased.
    • B. Production of prostaglandin is increased.
    • C. Concentration of arachidonic acid is decreased.
    • D. Substrate affinity of cyclooxygenase-2 is higher.
    Answer, explanation and textbook page: open in the app.