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Question 1 1. An atom is defined as a smallest particle of ____ i) A compound that can take part in chemical reaction ii...

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Question 1 1. An atom is defined as a smallest particle of ____ i) A compound that can take part in chemical reaction ii) An element that can take part in chemical reaction iii) A molecule that with other molecules iv) An isotope that can take part in chemical reaction v) A compound that reacts with other compounds

Answer: ●

An element that can take part in chemical reaction

2. The three domains of life are____ i) Eukarya, fungi and bacteria ii) Eukarya, archaea and bacteria iii) Eukarya, fungi and animalia iv) Eukarya, archaea and fungi v) Eukarya, bacteria and animalia

Answer: ●

Eukarya, archaea and bacteria

3. Van der Waals interaction is a bond formed by ____ i. Polar positively charged and polar negatively charged atoms ii. Polar positively charged and non-polar negatively charge atoms iii. Non-polar positively charged and non-polar negatively charge atoms iv. Positively charged and negatively charge atoms v. Non-polar positively charge and negatively charged atoms

Answer: ●

Non-polar positively charged and non-polar negatively charge atoms

(Van der Waals interactions: Non-polar covalent bonds may have positively and negatively charged regions where very weak bonds can be formed when the atoms and molecules are very close together.) 4. Chitin is an example of a _____ i. Polypeptide ii. Polysaccharide iii. Fat iv. Nucleic acid v. Glycerol

Answer: ●

Polysaccharide

(Chitin Structure: The structure is similar to cellulose except that chitin has a nitrogen – containing appendages in its glucose monomer. Functions: The exoskeleton of arthropods, (insects, spiders ,

crustaceans and related animals is composed of chitin. In fungi, it is used as the building material for their cell walls.) 5. The electron configuration 1s22s22p6 belongs to____ i. Carbon ii. Oxygen iii. Nitrogen iv. Neon v. Magnesium

Answer: ●

Neon

6. Ribosomes are responsible for____ i. Protein synthesis ii. Digestive compartments iii. Photosynthesis iv. Controlling the centre of the cell v. The removal of waste from the cell

Answer: ●

Protein synthesis

7. The mass number refers to_____ i) The number of protons in an atom ii) The combined number of protons and neutrons in an atom iii) The number of electrons in an atom iv) The combined number and protons and electrons in an atom v) The number of neutrons and electrons in an atom

Answer: ●

The combined number of protons and neutrons in an atom

8. Chloroplasts are responsible for: i. The shipping and receiving centre ii. Digestive compartments iii. Photosynthesis iv. Controlling the centre of the cell v. Protein synthesis

Answer: ●

Photosynthesis

9. In DNA double helix, adenine pairs with ______ and guanine pairs with ______ i. cytosine, thymine ii. guanine, adenine iii. uracil, cytosine

iv. thymine, cytosine v. cytosine, uracil

Answer: ●

thymine, cytosine

10. Which statement best describes the isotonic solution? i. It is a solution with a high solutes concentration and a low water concentration. ii. It is a solution with a high water concentration and low solutes concentration. iii. It is a solution with a balanced water and solutes concentration. iv. It is a solution with a high water concentration and a low solutes concentration, hence producing constant movement of water. v. Both i. and ii. are correct.

Answer: ●

It is a solution with a balanced water and solutes concentration.

11. Which statement best describes chemical work? i. The beating of cilia, contraction of muscles. ii. Movement of chromosomes during cellular reproduction. iii. The pumping of substances across membranes against spontaneous movement. iv. The pushing driving of endergonic reactions, such as the synthesis of polymers from monomers. v. The diffusion of substances across the selective permeable membrane

Answer: ●

The pushing driving of endergonic reactions, such as the synthesis of polymers from monomers.

12. The atomic number refers to____ i. The number of protons in an atom ii. The combined number of protons and neutrons of an atom iii. The number of electrons in an atom iv. The combined number of protons and electrons of an atom v. The number of neutrons and electrons.

Answer: ●

The number of protons in an atom

13. A 9:3:3:1 phenotypic ratio is characteristic of the____ i. F1 generation of a monohybrid cross ii. F2 generation of a monohybrid cross iii. F1 generation of a dihybrid cross iv. F2 generation of a dihybrid cross v. F3 generation with dihybrid cross

Answer: ●

F2 generation of a dihybrid cross

14. The correct definition of isotopes is _____ i) Atoms of the different elements that have the same number of neutrons, but differ in the number of protons. ii) Atoms of the same element containing the same number of protons, but differ in the number of electrons. iii) Atoms of the same element containing the same number of protons, but differ in the number of neutrons. iv) Atoms of the same element containing the same number of electrons, but differ in the number of neutrons. v) Atoms of different elements that have the same number of neutrons, but differ in the number of electrons.

Answer: ●

Atoms of the same element containing the same number of protons, but differ in the number of neutrons.

15. A pH of 7 indicates that____ i) The solution consists of pure water ii) The concentration of hydrogen ions equals that the hydroxide ions in the solution iii) There are no hydrogen ions in the solution iv) There are no hydroxide ions in the solution v) i) and ii) are correct

Answer: ●

The concentration of hydrogen ions equals that the hydroxide ions in the solution

16. Cellulose is an example of a_____ i) Polypeptide ii) Lipid iii) Polysaccharide iv) Fat v) Nucleic acid

Answer: ●

Polysaccharide

(Cellulose Structure: Is a polymer formed by the glucose in the β configuration making every glucose upside down with respect to next joined ones. Function: Major component of the plant cell wall. Building material for plants.) (Glycogen Structure: It is formed by polymers of glucose which form substantial number of branches. Function: When hydrolysed the glycogen releases glucose when the sugar demand increases.) [Starch Structure: Is formed by glucose monomers joined by 1-4 linkages. Function: When starch is broken down the available glucose serve as nutrient for animal cells (including humans)]

17. What is the basic unit of life? i) DNA ii) Cells iii) Organelles iv) Nuclei v) Tissue

Answer: ●

Cells

18. Which term/s is/are not part of the group i) Solute ii) Solvent iii) Evaporation iv) Solution v) i) + iii)

Answer: ●

Evaporation

Question 2 ●

Explain how edges and corridors can strongly influence landscape biodiversity (6)

Answer: Edges between ecosystems have unique sets of physical conditions and communities of species. Edges become more extensive as habitat fragmentation increases, and edge-adapted species may become more dominant. Movement corridors may promote dispersal and help sustain populations or they may promote harmful conditions such as disease. ●

Distinguish between/Compare the fate of pyruvate in alcohol fermentation and in lactic acid fermentation (6)

Answer: Alcohol fermentation Pyruvate is converted to ethanol in two steps Carbon dioxide is released from the pyruvate and forms acetaldehyde Acetaldehyde is reduced by NADH to ethanol



Lactic acid fermentation Pyruvate is directly reduced by NADH to form lactate as an end product No release of carbon dioxide No acetaldehyde formed

Compare in tabular form the process of fermentation and cellular respiration (10)

Answer: Fermentation The final electron acceptor is an organic molecule pyruvate (lactic acid fermentation) or acetaldehyde (alcohol fermentation) Harvests less energy Yields 2 ATPs Anaerobic conditions ●

Cellular respiration The final electron acceptor is oxygen Harvests more energy Yields 38 ATPs Aerobic conditions

Name the tree domains of life (3)

Answer: Bacteria, archaea, eukarya ●

Define the following terms: o Diploid

Answer: o

✓ Two sets of chromosomes per nucleus. Enthalpy

Answer: o

✓ The total potential energy of a system. Autotroph

Answer: o

✓ Produce its own organic food from inorganic substances Climax community

Answer: o

✓ Succession progress to a stable persistent community Ecotone

Answer: o

✓ Transition zone where two communities or biomes meet and integrate. Primosome

Answer:

o

✓ A complex of proteins responsible for synthesizing the RNA primers required in DNA synthesis. Isomer

Answer: ✓ Two or more chemical compound with the same chemical formula but different structural formulas.



Give the name of the cell structure that has the following function o It is the control centre of the cell

Answer: o

✓ Nucleus It encloses cellular contents and regulates movement of material in and out of the cell

Answer: o

✓ Plasma membrane It stores materials, waste and water, and maintains hydrostatic pressure

Answer: o

✓ Vacuole It is the site of lipid synthesis

Answer: o

✓ Smooth endoplasmic reticulum It enables photosynthesis

Answer: ✓ Chloroplast



Compare animal and plant cell in tabular form (12)

Answer: Plant cell Consists of cell wall Regular fixed shape Large central vacuole and tonoplast Chloroplast present No lysosomes No centrosomes



Animal cell No cell wall

Irregular If present small vacuole Absent Present Present

Distinguish between asexual and sexual reproduction (3)

Answer: In asexual reproduction, one parent produces genetically identical offspring. Sexual reproduction is a type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from the gametes of the two parents. Gametes are produced through meiosis. ●

Compare a prokaryotic cell to a eukaryotic cell (10)

Answer: SIMILARITIES: 1. They both have DNA as their genetic material. 2. They are both membrane bound. 3. They both have ribosomes. 4. They have similar basic metabolism. 5. They are both amazingly diverse in forms. DIFERENCES: 1. Eukaryotes have a nucleus, while prokaryotes do not 2. Eukaryotes have membrane-bound organelles, while prokaryotes do not. 3. Eukaryotic cells are, on average, ten times the size of prokaryotic cells. 4. The DNA of eukaryotes is much more complex and therefore much more extensive than the DNA of prokaryotes. 5. Eukaryotes undergo mitosis; prokaryotes divide by binary fission (simple cell division)



List the seven properties of life (7)

Answer: ✓ Cellular organization ✓ Homeostasis ✓ Metabolism ✓ Responsiveness ✓ Reproduction ✓ Heredity ✓ Growth ●

What is an isotope? Discuss this phenomenon with regard to the medical application of radioisotopes (5)

Answer: Isotopes are the atoms of an element that have the same number of protons but different amounts of neutrons. Radioisotopes are isotopes with unstable nucleus, which decays spontaneously releasing particles and energy – change number of protons – transform atom to atom of different element.

Often used as diagnostic tools in medicine – example kidney disorders are diagnosed by injecting small doses of radioactively-labelled substances into the blood and then analysing the tracer molecules excreted in the urine. PET scans for cancer tumours/cells. Cells can use radioactive atoms just as they would use nonradioactive isotopes of the same elements. The radioactive isotopes are incorporated into biological active molecules, which are then used as tracers to track atoms during metabolism. Researchers measure radioactive decay in fossils to date these relics of past life



Give the electron configuration of oxygen (3)

Answer: 1s22s22p4



Imagine a hybrid cross in dogs. The female is a true-breed black, long-tailed dog. The male is a true-breed white, short-tailed dog B- black hair b- white hair T- long tail t- short tail o Give the genotypes of the P –generation and the genotype of their gametes

Answer: P-generation: female x male BBTT x bbtt Gametes: BT bt o What is the genotype of the F1 – generation

Answer: F1- generation: BbTt o Illustrate with Punnet square the F2 –generation indicate the gametes

Answer: F2-generation: BbTt x BbTt Gametes

BT

Bt

BT

BBTT

BBTt

Bt

BBTt BbTT BbTt

BBtt

bT bt o

BbTt Bbtt

bT BbTT BbTt BbTT bbTt

Bt BbTt Bbtt bbTt bbtt

What is the ratio for the phenotype

Answer: 9:3:3:1 o Describe the characteristics of the phenotype for the F2 –generation

Answer: 9 - black, long tail 3 - white, long tail 3 - black, short tail 1- white, short tail



Describe the structure and functions of four polysaccharides (8)

Answer: Starch o o

Structure: Is formed by glucose monomers joined by 1-4 linkages. Function : When starch is broken down the available glucose serve as nutrient for animal cells(including humans)

o o

Structure : It is formed by polymers of glucose which form large number of branches. Function: When hydrolysed the glycogen releases glucose when the sugar demand increases.

o

Structure : Is a polymer formed by the glucose in the β configuration making every glucose upside down with respect to next joined ones. Function : Major component of the plant cell wall. Building material for plants.

Glycogen

Cellulose

o Chitin o o



Structure: The structure is like cellulose except that chitin has a nitrogen – containing appendages in its glucose monomer. Functions: The exoskeleton of arthropods, (insects, spiders, crustaceans and related animals is composed of chitin. In fungi, it is used as the building material for their cell walls.

Define the term “buffer” in the definition, refer to suitable examples of a buffer and indicate its application in living systems (3)

Answer: A buffer is a substance that minimizes the changes in the concentrations of H+ and OH- in a solution. In living systems, for example human blood, buffering capacity of the blood prevents the swing s in pH. The normal pH of human blood is 7.4, which slightly basic. If the pH increases to more than the normal one, the buffer works by accepting H+ from the solution when they are in excess and donating H+ to the solution when they have been lacking.

Question 3 ●

In sesame plants, the one-pod condition (P) is dominant to the tree-pod condition (p) Normal leaf (L) is dominant to wrinkled leaf (l). A homozygote in one-pod condition and normal leaves is crossed with a homozygote in three- pod condition and wrinkled leaves. Use a Punnet square to predict the phenotypic and genotypic ratios of the F2 generation. (19)

Answer: P-generation: PPLL crossed with ppll Gametes through meisois: PL cross with pl F1-generation are all PLpl all purple F1-generation cross with F1-generation: Gametes formed by meiosis are PL, Pl, pL and pl crossed with PL, Pl, pL and pl The Punnet square for the F2 generation is as follows:

F2-generation: Phenotype: 9 one pod normal: 3 three pod normal: 3 one pod wrinkle : 1 three pod, wrinkle. ●

Distinguish between parasitism, mutualism and commensalism (6)

Answer: Parasitism: a symbiotic relationship in which the parasite benefits at the expense of the host. Mutualism: a symbiotic relationship in which both participants benefit. Commensalism: a symbiotic relationship in which the symbiotic benefits but the host is neither helped nor harmed. ●

Explain how enzyme activity can be regulated or controlled by environmental factors, substrate concentration co-factors and enzyme inhibitors

Answer: The velocity of an enzymatic reaction will increase with temperature because the substrate collides with active sites more frequently. Beyond the optimum temperature the speed of an enzymatic reaction will drop sharply. The same hold true for pH. The more substrate molecule available the more frequently they access the active sites of the enzymes. However, there is a limit to how fast the reaction can be pushed by adding more substrate to a fixed concentration of enzyme and the velocity of the reaction will stabilize if all the active sites are engaged. Cofactors can be inorganic or organic (called co-enzymes) that bound to the active site to assist the enzyme. Enzyme inhibitors are usually chemicals that inhibit the enzyme reaction by binding to the active site. It is usually irreversible if the inhibitor bind covalently to the site by it may be reversible if the bond is weak.



Distinguish between the following terms: o Acid and base

Answer: o

✓ Acid – proton (H+ ) donor, Base is proton acceptor. Kinetic and potential energy

Answer: o

✓ Kinetic energy- energy in motion, potential- to do work (stored energy). Phagocytosis and pinocytosis

Answer: ✓ Phagocytosis – cell engulfs food particles. Pinocytosis, cell engulfs liquid

Question 4 ●

Name the five features of living organisms (5)

Answer: ✓ Organisms are composed of cells. ✓ Living organisms grow and develop. ✓ Metabolism. ✓ Response to stimuli. ✓ Reproduction. ✓



Living things are made of cells. Living things obtain and use energy. Living things grow and develop. Living things reproduce. Living things respond to their environment

What is the summarised equation for cellular respiration? (6)

Answer: Organic compounds + Oxygen → Carbon dioxide + Water + Energy OR C6H12O6 + 6O2 → 6C02+ 6H20 + Energy (ATP + heat) ●

Make labelled drawings to illustrate the different phases of mitosis in an animal cell with two chromosomes. (20)

Answer:



Tabulate the key differences between mitosis and meiosis. (14)

Answer: Mitosis DNA replication occurs during interphase before mitosis begins One division Synapsis does not occur Two daughter cells, each 2n and genetically identical to parent cell Effects growth and repair ●

Meiosis DNA replication occurs during interphase before meiosis 1 begins Two divisions Synapsis occurs during prophase 1 Four haploid cells, each containing half as many chromosomes as the parent cell Produces gametes

A purple flower with an unknown genotype is crossed with a white flower. Determine the genotype of the purple flower if purple (P) is dominant and white (p) is recessive. (20)

Answer: P-generation: o o o o o

The purple flower must have the P-allele because purple is dominant. We do not know what the other allele is – P or p. Let us suppose the other allele is P. PP crossed with pp (true-bred white) Gametes through meiosis: P crosses with p F1-generation is all Pp, all purple If the outcome of our cross is purple flowers, we know that the purple flower was also true-bred.

Let us look at the other option, where the purple flower is a heterozygote – P-generation:

o o

P p

Pp (heterozygote) crossed with pp (true-bred white) Gametes through meiosis: P and p crossed with p and p

p Pp pp

p Pp pp

Phenotype: 2 purple to 2 white If the outcome of our cross is 2 purple flowers to 2 white flowers, know that the purple flower was a heterozygote. The outcome is 50% white and 50% purple.



Describe the structure and function of ribosomes. (10)

Answer: ✓ Ribosomes are made of two types of subunits – large and small subunits. ✓ The ribosomal subunits are made up of proteins and RNA molecules are called ribosomal RNA, or rRNA. ✓ The ribosomal subunits are made in the nucleolus. ✓ The subunits are then transported via the nuclear pores to the cytoplasm. ✓ Approximately two-thirds of the mass of a ribosome is rRNA. ✓ The ribosomes of eukaryotes are slightly larger than those of prokaryotes. ✓ Ribosomes play a role in the formation of polypeptides.



Define predation, herbivory and parasitism. (6)

Answer: ✓ Predation: The interaction in which a predator eats another animal. ✓ Herbivory: The interaction in which an herbivore eats a plant. ✓ Parasitism: A symbiotic relationship in which the parasite benefits at the expense of the host.



Write short notes on the greenhouse effect. (6)

Answer: ✓ CO2, water vapour, sulphur dioxide and other greenhouse gases in the atmosphere intercept and absorb radiant energy emitted by the earth and reflect it back towards the earth. This process causes some of the solar energy to be retained. The greenhouse effect is believed to have contributed to the present global warming.



List the four major threats to biodiversity and give an example of each.

Answer: ✓ HABITAT LOSS: Human activities such as agriculture, urban development, forestry, mining, etc., can also lead to habit loss. ✓ INTRODUCED SPECIES: Introduction of exotic species, are those that humans move intentionally or accidently from the species, native locations to new geographic regions. ✓ OVERHARVESTING: Overharvested organisms such as seabirds, elephants, whales, rhinoceroses, and fish are in the danger of extinction because of overharvesting. ✓ GLOBAL CHANGE: The final threat to biodiversity is global change which changes the fabric of Earth’s ecosystems at regional to global scales. Global change includes climate, atmospheric chemistry, and broad ecological systems that reduce the capacity of Earth to sustain life.



Draw a diagram to describe the process of alcoholic fermentation. (12)



Define mitosis (3)

● Explain the difference between cytokinesis in plant and animal cells. (6) In animal cells, cytokinesis occurs by a process known as cleavage. Plant cells have cell walls and form no cleavage furrow. ● List the phases of meiosis I and meiosis II and describe the events characteristic of each phase. (20) Meiosis I Prophase I: it is when the homologous chromosomes replicate Metaphase I: chromosomes are arranged on metaphase plate Meiosis II Prophase II: a spindle is formed Metaphase II: chromosomes are on the metaphase plate as on meiosis I ●

Explain the general process of transcription, including the three major steps of initiation, elongation and termination. (12)



Distinguish between a food chain and a food web. (4)



Write short notes on global warming. (7)



How is the accumulation of chlorofluorocarbons responsible for depleting the atmospheric zone