namibia UniVERSITY OF SC IEnCE AnD TECHnOLOGY FACULTY OF HEALTH AND APPLIED SCIENCES DEPARTMENT OF HEALTH SCIENCES PAPER: THEORY

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1 namibia UniVERSITY OF SC IEnCE AnD TECHnOLOGY FACULTY OF HEALTH AND APPLIED SCIENCES DEPARTMENT OF HEALTH SCIENCES QUALIFICATION: BACHELOR OF BIOMEDICAL SCIENCES QUALIFICATION CODE: SOBBMS LEVEL: 6 COURSE: CELL BIOLOGY SESSION: JUNE 2016 COURSE CODE: CEB210S PAPER: THEORY DURATION: 3 HOURS MARKS: 100 FIRST OPPORTUNITY EXAMINATION QUESTION PAPER EXAMINER(S) Mrs Elsabe van der Coif MODERATOR: Mrs Cornelia de Waai-Miller INSTRUCTIONS 1. Answer all questions. 2. Please write neatly and legibly. 3. Do not use the left side margin ofthe exam paper. This must be allowed for the examiner. 4. No books, notes and other additional aids are allowed. 5. Mark all answers clearly with their respective question numbers. THIS QUESTION PAPER CONSISTS OF _7 _PAGES (Including this front page)

2 SECTION A (43 MARKS) QUESTION 1 [13] Evaluate the statements in each numbered section and select the most appropriate answer or phrase from the given possibilities. Write the appropriate letter next to the number of the statement/phrase. 1.1 The transmission electron microscope {1) is ideal for looking at living cells. has a resolution of 0.2 nm. uses lenses made of glass. was invented by Anton van Leeuwenhoek. is easily transportable. 1.2 Which of the following statements is incorrect? (1) Glycogen is formed from units that include glucose. Starch (in plants) is formed from units that include glucose. Lactose is formed from units that include ribose. Adenosine is formed from units that include ribose. Maltose is formed by two glucose molecules. 1.3 The following type of organelle has the function to recycle molecules like those used to build the cell membrane in neurons: (1) Peroxisome Lysosome Mitochondria Endoplasmic reticulum Golgi apparatus 1.4 Methionine is coded for by: (1) one codon only two different codons three different codons four different codons six different codons 1.5 Okazaki fragments are {1) short peptide sequences. RNA primers. newly synthesized stretches of DNA produced during replication of the lagging template strand. degraded fragments of DNA. the lengths of DNA between origins of replication. 2

3 1.6 The trp operon is transcribed when (1) tryptophan concentrations in the cell are high. the trp repressor is bound to tryptophan or a sim ilar shaped molecule. tryptophan is bound to its aporepressor. the appropriate corepressor is absent. all of the above. 1.7 The following are functions of domains in proteins, except: (1) to form globular proteins binds a small ligand (e.g. a peptide) spans the plasma membrane (transmembrane proteins) DNA binding (in transcription factors) provides a surface to bind specifically to another protein 1.8 Endocytotic vesicles can only form in the presence of (1) receptors specific for a ligand that is present in the extracellular medium. adaptor proteins clathrin dynamin all of the above 1.9 The Krebs cycle (1) breaks down pyruvate oxidizes two-carbon units to produce carbon dioxide and reduced coenzymes oxidizes glycerol drives H+ out of the mitochondrial matrix uses GTP rather than ATP to supply phosphate groups When a nerve cell axon is depolarized to threshold, the flow of potassium through potassium channels in the plasma membrane is (1) outward, and of a greater absolute amplitude than at the resting voltage. inward, and of a greater absolute amplitude than at the resting voltage. outward, but of a smaller absolute amplitude than at the resting voltage. inward, but of a smaller absolute amplitude than at the resting voltage. zero Extracellular messengers include the following except: (1) polysaccharides amino acids and derivatives, e.g. glutamate, thyroid hormone, acetylcholine gases e.g. nitric oxide and carbon dioxide steroids, e.g. sex hormones a wide variety of polypeptides and proteins 3

4 1.12 Which of the following are not components of the cytoskeleton? (A} Actin filaments Collagen fibers Microtubules Microfilaments Intermediate filaments 1.13 Pa ired chromatids separate and begin to move toward the spindle poles in mitotic (A} prophase prometaphase metaphase anaphase telophase QUESTION 2 [10] Assess the following statements and decide whether they are true or false. Write only the number of the question and TRUE for a true statement or FALSE for a false statement next to the number of the question. 2.1 An electron microscope has a lower resolving power than a light microscope. 2.2 In the water molecule electrons spend more time orbiting the two hydrogen nuclei than orbiting the oxygen nucleus. 2.3 The primary function of the Golgi apparatus is the processing and packaging of proteins and lipids for cell secretion (exocytosis} or for use within the cell Gyrase adds nucleotides to a growing strand of DNA. 2.5 In transcription both DNA strands are copied. 2.6 Domains are protein sequences and structures that evolve, function and exist independently from the rest of the protein. 2.7 Amino acid sequence determines the fate/destination of proteins. 2.8 Unfolding of proteins is necessary since nuclear pores are not big enough to transport them. 2.9 The 1st and 2"d Laws of Thermodynamics indicate that universal energy is not constant Axonal transport refers to the transport of organelles, small vesicles and mrna in both directions. 4

5 QUESTION 3 [20] Define I briefly describe the following terms: 3.1 Two types of electron microscopes (2) 3.2 Hydrolysis (2) 3.3 Gap junctions (2) 3.4 The genetic code (2) 3.5 Two basic mechanisms which organisms use to reduce the error rate of DNA replication (2) 3.6 A promotor in molecular biology (2) 3.7 The two ends of a protein (2) 3.8 Michaelis Menton constant (2) 3.9 Membrane potential vs resting potential. (2) 3.10 Cytoplasmic streaming within eukaryotes. {2) SECTION B (17 MARKS) QUESTION 4 [9] 4.1 Describe three functions of lipids inside the cell. (3) 4.2 Classify the following cell junctions based on localization: {6) Tight junctions Adherens junctions and desmosomes Hemidesmosomes Gap junctions QUESTION Mention three facts about a domain of a protein. 5.2 Name two pathways in lipid metabolism. [8] {3) (2) 5

6 5.3 Match each checkpoint in the cell cycle with the appropriate question. (3) Checkpoint Question 1. GJS A. Can sister chromatids separate correctly? 2. Gz/M B. Has DNA synthesis been completed correctly? 3. Spindle checkpoint c. Can DNA synthesis begin? SECTION C (40 MARKS} QUESTION 6 [9] 6.1 Describe the functions of the three types of muscle tissue. (6) 6.2 Illustrate (in words) the importance of nucleosides and nucleotides in the human body. (3) QUESTION 7 [11] 7.1 Match each type of single base substitution (mutation) in the first column with the appropriate description in the second column. Write only the number and the appropriate letter. (5) MUTATION DESCRIPTION 1. Missense mutation A. If a single base substitution modifies a codon to a termination codon. 2. Nonsense mutation B. A purine is substituted by a pyrimidine or vice versa. 3. Frameshift mutation C. A purine is replaced by another purine or a pyrimidine is replaced by another pyrimidine. 4. Transitions D. If the mutated codon specifies another amino acid in the polypeptide chain during translation. 5. Transversions E. Insertions or deletions of bases shift the reading frame. 6

7 7.2 Create a table and identify the template and the product (from... to... ) in each of the following processes: QUESTION 8 Replication Transcription Translation 8.1 Describe four functions of amino acids. 8.2 Explain how specificity in vesicle targeting is ensured. (How do the vesicles know where to go?) 8.3 Identify any four properties of enzymes. {6} [10] (4} (2} (4} QUESTION Name two types of membrane transport proteins and mention two facts about each. 9.2 Write notes on the stimulus for cell reproduction and the role of growth factors. [10] {6} (4} END OF QUESTION PAPER. GOOD LUCK! 7