Answer: - Unisa Study Notes



Question 1An atom is defined as a smallest particle of ____A compound that can take part in chemical reactionAn element that can take part in chemical reactionA molecule that with other moleculesAn isotope that can take part in chemical reactionA compound that reacts with other compoundsAnswer:An element that can take part in chemical reactionThe three domains of life are____Eukarya, fungi and bacteriaEukarya, archaea and bacteriaEukarya, fungi and animaliaEukarya, archaea and fungiEukarya, bacteria and animaliaAnswer:Eukarya, archaea and bacteriaVan der Waals interaction is a bond formed by ____Polar positively charged and polar negatively charged atomsPolar positively charged and non-polar negatively charge atomsNon-polar positively charged and non-polar negatively charge atomsPositively charged and negatively charge atomsNon-polar positively charge and negatively charged atomsAnswer: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.)Chitin is an example of a _____PolypeptidePolysaccharideFatNucleic acidGlycerolAnswer: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.)The electron configuration 1s22s22p6 belongs to____CarbonOxygenNitrogenNeonMagnesiumAnswer:NeonRibosomes are responsible for____Protein synthesisDigestive compartmentsPhotosynthesisControlling the centre of the cellThe removal of waste from the cellAnswer:Protein synthesisThe mass number refers to_____The number of protons in an atomThe combined number of protons and neutrons in an atomThe number of electrons in an atomThe combined number and protons and electrons in an atomThe number of neutrons and electrons in an atomAnswer:The combined number of protons and neutrons in an atomChloroplasts are responsible for:The shipping and receiving centreDigestive compartmentsPhotosynthesisControlling the centre of the cellProtein synthesisAnswer:PhotosynthesisIn DNA double helix, adenine pairs with ______ and guanine pairs with ______ cytosine, thymineguanine, adenineuracil, cytosinethymine, cytosinecytosine, uracilAnswer:thymine, cytosineWhich statement best describes the isotonic solution? It is a solution with a high solutes concentration and a low water concentration.It is a solution with a high water concentration and low solutes concentration.It is a solution with a balanced water and solutes concentration.It is a solution with a high water concentration and a low solutes concentration, hence producing constant movement of water. Both i. and ii. are correct.Answer:It is a solution with a balanced water and solutes concentration.Which statement best describes chemical work? The beating of cilia, contraction of muscles. Movement of chromosomes during cellular reproduction. The pumping of substances across membranes against spontaneous movement.The pushing driving of endergonic reactions, such as the synthesis of polymers from monomers.The diffusion of substances across the selective permeable membraneAnswer:The pushing driving of endergonic reactions, such as the synthesis of polymers from monomers.The atomic number refers to____The number of protons in an atomThe combined number of protons and neutrons of an atomThe number of electrons in an atomThe combined number of protons and electrons of an atomThe number of neutrons and electrons.Answer:The number of protons in an atomA 9:3:3:1 phenotypic ratio is characteristic of the____ F1 generation of a monohybrid crossF2 generation of a monohybrid crossF1 generation of a dihybrid crossF2 generation of a dihybrid crossF3 generation with dihybrid crossAnswer:F2 generation of a dihybrid crossThe correct definition of isotopes is _____ Atoms of the different elements that have the same number of neutrons, but differ in the number of protons. Atoms of the same element containing the same number of protons, but differ in the number of electrons.Atoms of the same element containing the same number of protons, but differ in the number of neutrons. Atoms of the same element containing the same number of electrons, but differ in the number of neutrons. 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. A pH of 7 indicates that____The solution consists of pure waterThe concentration of hydrogen ions equals that the hydroxide ions in the solutionThere are no hydrogen ions in the solutionThere are no hydroxide ions in the solutioni) and ii) are correctAnswer:The concentration of hydrogen ions equals that the hydroxide ions in the solutionCellulose is an example of a_____ PolypeptideLipidPolysaccharideFatNucleic acidAnswer: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)]What is the basic unit of life?DNACellsOrganellesNucleiTissueAnswer:CellsWhich term/s is/are not part of the groupSoluteSolventEvaporationSolutioni) + iii)Answer:EvaporationQuestion 2Explain 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 Lactic acid fermentation Pyruvate is converted to ethanol in two steps Pyruvate is directly reduced by NADH to form lactate as an end product Carbon dioxide is released from the pyruvate and forms acetaldehyde No release of carbon dioxide Acetaldehyde is reduced by NADH to ethanol No acetaldehyde formedCompare in tabular form the process of fermentation and cellular respiration (10)Answer:FermentationCellular respirationThe final electron acceptor is an organic molecule pyruvate (lactic acid fermentation) or acetaldehyde (alcohol fermentation) The final electron acceptor is oxygen Harvests less energy Harvests more energy Yields 2 ATPs Yields 38 ATPs Anaerobic conditions Aerobic conditions Name the tree domains of life (3)Answer:Bacteria, archaea, eukaryaDefine the following terms:DiploidAnswer:Two sets of chromosomes per nucleus.EnthalpyAnswer:The total potential energy of a system.AutotrophAnswer:Produce its own organic food from inorganic substancesClimax communityAnswer:Succession progress to a stable persistent communityEcotoneAnswer:Transition zone where two communities or biomes meet and integrate.PrimosomeAnswer:A complex of proteins responsible for synthesizing the RNA primers required in DNA synthesis.IsomerAnswer: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 functionIt is the control centre of the cellAnswer:NucleusIt encloses cellular contents and regulates movement of material in and out of the cellAnswer:Plasma membrane It stores materials, waste and water, and maintains hydrostatic pressureAnswer:VacuoleIt is the site of lipid synthesisAnswer:Smooth endoplasmic reticulumIt enables photosynthesisAnswer:ChloroplastCompare animal and plant cell in tabular form (12)Answer: Plant cell Animal cell Consists of cell wall No cell wall Regular fixed shape Irregular Large central vacuole and tonoplast If present small vacuole Chloroplast present Absent No lysosomes Present No centrosomes 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 pare 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 not2. 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 organizationHomeostasis Metabolism Responsiveness Reproduction Heredity GrowthWhat 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 lifeGive the electron configuration of oxygen (3)Answer:1s22s22p4Imagine a hybrid cross in dogs. The female is a true-breed black, long-tailed dog. The male is a true-breed white, short-tailed dogB- black hairb- white hairT- long tailt- short tailGive the genotypes of the P –generation and the genotype of their gametesAnswer:P-generation: female x male 2028825181610BBTT x bbtt2447290635000Gametes: BT btWhat is the genotype of the F1 – generationAnswer:F1- generation: BbTt Illustrate with Punnet square the F2 –generation indicate the gametesAnswer:F2-generation: BbTt x BbTtGametes BT Bt bT Bt BT BBTT BBTt BbTT BbTt Bt BBTt BBtt BbTt Bbtt bT BbTT BbTt BbTT bbTt bt BbTt Bbtt bbTt bbtt What is the ratio for the phenotypeAnswer:9:3:3:1Describe the characteristics of the phenotype for the F2 –generationAnswer:9 - black, long tail3 - white, long tail3 - black, short tail1- white, short tailDescribe the structure and functions of four polysaccharides (8)Answer:StarchStructure: 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)GlycogenStructure : 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.CelluloseStructure : 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.ChitinStructure: 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 3In 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 inhibitorsAnswer: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:Acid and baseAnswer:Acid – proton (H+ ) donor, Base is proton acceptor.Kinetic and potential energyAnswer:Kinetic energy- energy in motion, potential- to do work (stored energy).Phagocytosis and pinocytosisAnswer:Phagocytosis – cell engulfs food particles. Pinocytosis, cell engulfs liquidQuestion 4Name 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 environmentWhat 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 Meiosis DNA replication occurs during interphase before mitosis begins DNA replication occurs during interphase before meiosis 1 begins One division Two divisions Synapsis does not occur Synapsis occurs during prophase 1 Two daughter cells, each 2n and genetically identical to parent cell Four haploid cells, each containing half as many chromosomes as the parent cell Effects growth and repair 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: 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: Pp (heterozygote) crossed with pp (true-bred white) Gametes through meiosis: P and p crossed with p and ppp 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 IProphase I: it is when the homologous chromosomes replicateMetaphase I: chromosomes are arranged on metaphase plateMeiosis IIProphase II: a spindle is formedMetaphase II: chromosomes are on the metaphase plate as on meiosis IExplain 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 ................
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