BIOLOGY MIDTERM EXAM QUESTIONS WITH ANSWERS, Exams of Biology

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1. Why do cells need to have the mechanism to synthe- size glucose? a) Because glucose isn't readily available in our diet b) To supply glucose to brain and red blood cells during fasting, starvation or extended exercise c) Because only glucose made inside the body can be used for fuel d) Because glucose needs to be made into fructose to go through glycolysis 2. The reverse of the reaction carried out by pyruvate kinase in glycolysis is carried out by which enzyme(s) in gluconeogenesis? a) Fructose 1,6-bisphosphatase b) Both Pyruvate carboxylase and Phosphoenolpyru- vate carboxykinase c) Pyruvate carboxylase d) Phosphoenolpyruvate carboxykinase 3. What is the purpose of the first stage of glycolysis? a) Producing Acetyl Co-A b) Harvesting ATP energy c) Trapping glucose in the cell and priming it to be- come a high-transfer phosphate donor d) Maintaining redox balance in the cell 4. Which enzyme catalyzes the SECOND phosphoryla- tion event in glycolysis? a) Glucose 6-phosphate isomerase b) Aldolase c) Phosphofructokinase d) Hexokinase 5. Which of the following statements about metabolism are true? 1) Catabolism is the process in which complex sub- stances are broken down, yielding a net output of energy.2) Metabolism is an integrated system in which many of the same reactions participate in degradative

b) To supply glu- cose to brain and red blood cells during fast- ing, starvation or extended exercise b) Both Pyru- vate carboxylase and Phospho- enolpyruvate car- boxykinase c) Trapping glu- cose in the cell and prim- ing it to become a high-transfer phosphate donor c) Phosphofruc- tokinase b) All four state- ments are correct.

A trans fatty acid: a) has a tail that resembles a saturated fatty acid in conformation b) is the most prevalent type of unsaturated fat found in nature. c) has a kinked tail structure. d) has a tail that resembles a cis fatty acid in confor- mation.

10. True or False. Triacylglycerols are the most prevalent type of fat seen in membranes? 11. ATP is a donor molecule for what type of covalent modification of enzymes? a) ubiquination b) sulfation c) phosphorylation d) acetylation 12. How are zymogens activated? a) acetylation b) protease cleavage (peptide bond cleavage) c) dephosphorylation d) phosphorylation 13. What is the velocity of a reaction at the concentration defined by Km? a) Vmax b) none of the answers are correct. c) Vo d) 1/2 Vmax 14. Which one of the following describes how an uncom- petitive inhibitor effects on enzyme's Km and Vmax? a) Km and Vmax are both lower b) Km is lower and Vmax is the same c) Km is higher and Vmax is lower d) Km and Vmax are both higher e) Km is higher and Vmax is the same a) has a tail that resembles a satu- rated fatty acid in conformation False c) phosphorylation b) protease cleav- age (peptide bond cleavage) d) 1/2 Vmax a) Km and Vmax are both lower

A holoenzyme is: a) inactive enzyme without its cofactor b) inactive enzyme without its coenzyme c) active enzyme with its cofactor d) active enzyme with its coenzyme

21. Which statement is FALSE about allosteric regula- tion? a) Cellular response is faster with allosteric control than by controlling enzyme concentration in the cell. b) The regulation usually is important to the conserva- tion of energy and materials in cells. c) Allosteric modulators bind non-covalently at sites other than the active site and induce conformational changes in the enzyme. d) It is usually the mode of regulation for the last step in reaction pathways since this step produces the final product. 22. The stereochemical designators ±and ²distinguish be- tween: a) enantiomers at an epimeric carbon atom. b) enantiomers at an anomeric carbon atom. c) epimers at an anomeric carbon atom. d) epimers at a non-anomeric carbon atom. 23. Triacylglycerols are compounds which contain con- bined: a) cholesterol and other steroids b) fatty acids and phospholipids c) fatty acids and glycerol d) fatty acids and choline 24. Lipids are naturally occurring compounds which all: a) contain fatty acids as structural units b) are water-insoluble, but soluble in nonpolar sol- vents c) are cyclic in structure d) contain cholesterol c) active enzyme with its cofactor d) It is usually the mode of regulation for the last step in reaction path- ways since this step produces the final product. c) epimers at an anomeric carbon atom. c) fatty acids and glycerol b) are water- insol- uble, but soluble in

25. Saturated fats are at room temperature and are obtained from? a) liquids; plants b) liquids; animals c) solids; plants d) solids; animals 26. During a hydropathy analysis of a protein that has d) solids; animals c) Protein is like- recently been sequenced, a researcher discovers that ly to be an integral the protein has several regions that contain 20- hy- drophobic amino acids. What conclusions would she draw from this finding? a) Protein would be specifically localized in the mito- chondrial membrane. b) Protein would be targeted to the nucleus c) Protein is likely to be an integral protein d) Protein is probably a peripheral membrane protein 27. Unsaturated fatty acids have lower melting points than saturated fatty acids, because: a) their molecules fit closely together b) cis-double bonds give them an irregular shape c) they have fewer hydrogen atoms d) they have more hydrogen atoms 28. Which of these processes results in hyperpolariztion? a) excessive outflow of K+ b) excessive outflow of Na+ c) excessive influx of K+ d) excessive influx of Na+ 29. If a neuronal membrane, which is normally slightly passively permeable to K+, becomes impermeable, but the Na+/K+-ATPase remains active, the neuron's resting potential would become: a) more negative, because [K+] increases inside the neuron b) more negative, because [K+] increases outside the neuron c) more positive, because [K+] increases inside the

protein b) cis-double bonds give them an irregular shape a) excessive out- flow of K+ c) more positive, because [K+] in- creases inside the neuron

a) decrease in in- tracellular [K+] c) opening Na+ gates d) No. Oxygen (O2) is not a substrate for any of the enzyme-cat- alyzed reactions. a) Carbon dioxide b) NADH

35. Where in a eukaryotic cell does glycolysis occur? a) Mitochondrial matrix b) Peroxisome c) Cytosol d) Nucleus e) Endoplasmic reticulum 36. How many carbon atoms do each of the following molecules contain? Glucose, pyruvate and lactate a) 7, 4, and 3 b) 6, 3, and 3 c) 6, 2, and 2 d) 5, 2, and 3 37. What is the net number of ATP produced per glucose in an obligate anaerobe? a) 2 ATP b) 4 ATP c) 36 ATP d) 32 ATP 38. Which of the following enzymes does NOT catalyze an irreversible reaction in glycolysis? a) Hexokinase (HK) b) Phosphofructokinase (PFK) c) Glucose-6-phosphate isomerase (G6PI or PGI) d) Pyruvate kinase (PK) 39. Which enzyme-catalyzed reaction in glycolysis gener- ates NADH? a) The reaction catalyzed by hexokinase (HK) b) The reaction catalyzed by glyceraldehyde-3- phos- phate dehydrogenase (GAPDH) c) The reaction catalyzed by phosphofructokinase (PFK) d) The reaction catalyzed by phosphoglycerate kinase (PGK) c) Cytosol b) 6, 3, and 3 a) 2 ATP c) Glucose-6- phos- phate isomerase (G6PI or PGI) b)The reaction catalyzed by glyceralde- hyde-3-phos- phate dehydrogena se (GAPDH)

d) The reaction catalyzed by pyru- vate kinase (PK) c) 2 pyruvates (Pyr), 2 ATP, and 2 NADH a) Hexokinase b) oxaloacetate; mitochondrial ma- trix c) Cytosol

c) Cytosol d) Nucleus

45. Which of the following enzymes does NOT catalyze a bypass reaction in gluconeogenesis? a) Pyruvate carboxylase b) Glucose-6-phosphatase c) Fructose-1,6-bisphosphatase d) Glyceraldehyde-3-phosphate dehydrogenase e) Phosphoenolpyruvate carboxykinase 46. Which enzyme-catalyzed reaction in gluconeogenesis generates NADH? a) The reaction catalyzed by pyruvate carboxylase b) The reaction catalyzed by glyceraldehyde-3- phos- phate dehydrogenase c) The reaction catalyzed by glucose-6-phosphatase d) The reaction catalyzed by fructose-1,6- bisphos- phatase e) The reaction catalyzed by phosphoenolpyruvate carboxykinase f) None of the listed enzyme-catalyzed reactions in gluconeogenesis generates NADH. 47. What is the first reaction that begins metabolism of fructose in the liver? a) phosphorylation b) aldol cleavage c) hydrolysis d) isomerization 48. If a person is missing the enzyme lactase, what disac- charide do they have difficulty metabolizing? a) maltose b) lactose c) tetrahalose d) sucrose 49. Which of the following is NOT a reason why glycogen breakdown occurs via phosphorolysis instead of hy-

drolysis? a) Phosphorolysis enables the monosaccharide to readily leave the cell and travel to different tissues. b) Phosphorylated monosaccharides can enter direct- ly into glycolysis. c) Phosphorolysis adds a phosphate across the gly- cosidic bond, thus saving an ATP in glycolysis. d) All of the above are reasons why glycogen break- down occurs via phosphorolysis instead of hydroly- sis.

50. Phosphorylation of the dimer conformation of glycogen phosphorylase will this enzyme. a) phosphorylase b; inactivate b) phosphorylase b; activate c) phosphorylase a; activate d) phosphorylase a; inactivate 51. Which of the following indicates the most "active" conformation of the glycogen phosphorylase en- zyme? I. b form II. a form III. T state IV. R state a) III and I b) II c) II and IV d) I e) III f) IV 52. Which of the following nonhormonal intracellular con- ditions will trigger glycogen breakdown in muscle? a) High glucose-6-phosphate b) High AMP c) High glucose d) High ATP

saccharide to readily leave the cell and travel to different tissues. b) phosphorylase b; activate c) II and IV b) High AMP