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Biochemistry MCQ's

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Papers covered; - August 2013
tj.sloan
Quiz by tj.sloan, updated more than 1 year ago
tj.sloan
Created by tj.sloan almost 10 years ago
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Question 1

Question
The redox centre of FAD is
Answer
  • Flavin mononucleotide (FMN)
  • Nicotinamide
  • Adenosine
  • Phosphate

Question 2

Question
Which of the following nucleotide triphosphates is often involved in signal transduction and also provides the energy for ribosomal translocation?
Answer
  • CTP
  • TTP
  • UTP
  • GTP

Question 3

Question
Which monosaccharide provides the main source of energy for sperm cells?
Answer
  • Glucose
  • Fructose
  • Galactose
  • Mannose

Question 4

Question
Which pathway(s) include phosphorylated seven carbon monosaccharides?
Answer
  • Calvin cycle
  • Leloir pathway
  • Glycogen synthesis
  • All of the above

Question 5

Question
The isomerisation of glucose 1-phosphate to glucose 6-phosphate occurs in which two pathways?
Answer
  • Calvin cycle and glycogen synthesis
  • Leloir pathway and Calvin cycle
  • Leloir pathway and glycolysis
  • Leloir pathway and glycogen synthesis

Question 6

Question
Steroids
Answer
  • Are entirely hydrophobic molecules
  • Often act as hormones
  • Cannot pass through cell membranes
  • Are mainly hydrophilic molecules

Question 7

Question
The sequence of reactions: oxidation-hydration-oxidation occurs in which two pathways?
Answer
  • β-oxidation of fatty acids and tricarboxylic acid (Krebs’) cycle
  • β-oxidation of fatty acids and glycolysis
  • Fatty acid synthesis and tricarboxylic acid (Krebs’) cycle
  • Fatty acid synthesis and glycolysis

Question 8

Question
The mobility of membrane phospholipids can be demonstrated by
Answer
  • Irradiating a leaf and watching the return of the green colour
  • Observing the molecules using an electron microscope
  • Paper chromatography of the lipids and staining
  • Bleaching of fluorescently labelled phospholipids and watching the return of the fluorescence

Question 9

Question
Cholesterol is an example of what class of molecule?
Answer
  • Sterol
  • Fatty acid
  • Ketose monosaccharide
  • Aldose monosaccharide

Question 10

Question
In the Calvin cycle, how many molecules of carbon dioxide are required for the synthesis of one molecule of fructose 6-phosphate?
Answer
  • 3
  • 4
  • 6
  • 12

Question 11

Question
In cellulose, the glucose residues are bonded together by:
Answer
  • α(1→4) glycosidic bonds
  • α(1→4) glycosidic bonds with α(1→6) glycosidic bonds approximately every tenth residue
  • β(1→4) glycosidic bonds
  • β(1→4) glycosidic bonds with β(1→6) glycosidic bonds approximately every tenth residue

Question 12

Question
Which of the following is not a reducing sugar?
Answer
  • Sucrose
  • Maltose
  • Lactose
  • Galactose

Question 13

Question
The carnitine cycle
Answer
  • “Fixes” atmospheric carbon dioxide into sugars
  • Transports fatty acids into the matrix of the mitochondria
  • Transports ATP out of the mitochondria
  • Produces NADH for use in oxidative phosphorylation

Question 14

Question
Glycerol can be used as a source of energy by conversion to the glycolytic intermediate dihydroxyacetone phosphate. Per molecule of glycerol, this process:
Answer
  • Produces one molecule of NADH and consumes one molecule of ATP
  • Produces one molecule of ATP and consumes one molecule of NADH
  • Produces one molecule of NADH and consumes no molecules of ATP
  • Produces no molecules of NADH and consumes one molecule of ATP

Question 15

Question
Fatty acid synthesis:
Answer
  • Requires NADH
  • Requires water as a reactant
  • Adds carbon atoms two at a time
  • All of the above

Question 16

Question
In enzyme kinetics, the ratio of constants kcat/Km:
Answer
  • Is a measure of the rate of acceleration carried out by the enzyme.
  • For a given enzyme is independent of the substrate used.
  • Has units of concentration.
  • Gives an idea of the enzymes catalytic efficiency.

Question 17

Question
In enzyme catalysis, the term ‘approximation’ refers to:
Answer
  • A catalytic strategy facilitating transition state formation through covalent bond formation between the substrate and enzyme active site.
  • A catalytic strategy facilitating transition state formation through hydrogen bond formation and electrostatic bond formation between the substrate and enzyme active site.
  • A catalytic strategy facilitating transition state formation through interaction involving metal ions and substrate in the enzyme active site.
  • A catalytic strategy facilitating transition state formation through direct transfer of a proton to or from the substrate in the enzyme active site.

Question 18

Question
Consider an enzyme that shows Michaelis-Menten kinetics where: v0 = Vmax . [S] / (Km + [S]) If a substrate, S, is present at a concentration of 8 mM, and Km is 4 mM, the rate of reaction (v0) measured will be:
Answer
  • Half of Vmax
  • Two thirds of Vmax
  • Double Vmax
  • Three times Vmax

Question 19

Question
Koshland’s induced fit model for enzyme-substrate complex formation:
Answer
  • May explain why enzymes have particular substrate specificity.
  • May explain why enzymes are able to catalyse chemical reactions that cannot be facilitated in any other way
  • May explain why enzymes increase the rate of a reaction by reduction of the activation energy change for the reaction
  • May explain why enzymes can effectively reduce the loss of energy from a chemical reaction as heat

Question 20

Question
Enzymes:
Answer
  • are chemically altered at the end of their reaction
  • are involved in changing the equilibrium constant of the reaction that they catalyse
  • bind their substrates at their active site(s)
  • increase the activation energy of the reaction they catalyse

Question 21

Question
The Michaelis constant, Km:
Answer
  • Is a measure of the rate acceleration caused by the enzyme
  • For a given enzyme is independent of the substrate used
  • Has units of concentration
  • Gives an idea of the enzyme’s catalytic efficiency

Question 22

Question
The Vmax of an enzyme catalysed reaction:
Answer
  • Is altered when a competitive inhibitor is present
  • Can be determined from the intercept on the x-axis of a Lineweaver-Burk plot
  • Is the maximum rate at which the enzyme can convert substrate into product
  • Has units of concentration

Question 23

Question
Proteosome-mediated proteolysis:
Answer
  • Is controlled by serine protease enzymes.
  • Is a key part of the control mechanism in the eukaryote cell cycle
  • Is a key part of the control mechanism in the prokaryote cell cycle
  • Is controlled by ubiquinone activating enzymes.

Question 24

Question
The Alanine Cycle:
Answer
  • Is completely located in the mitochondrial matrix.
  • Facilitates transport of ammonia produced in the liver to the muscles where it can be used in anabolic processes - preventing the exposure of free ammonium to other components of eukaryote tissues.
  • Facilitates transport of ammonia produced in the muscles to the liver where it can be effectively removed from the body - preventing the exposure of free ammonium to other components of eukaryote tissues.
  • Is located in the cell membrane of muscle cells.

Question 25

Question
Which of the following is a Redox Centre of Mitochondrial Respiratory Chain Enzymes?
Answer
  • NADPH
  • Succinate
  • Oxygen
  • FMN, flavin

Question 26

Question
In Photosynthesis energy of light Quanta is captured by a molecule of:
Answer
  • Plastoquinone
  • Oxygen
  • Chlorophyll
  • Cytochrome c

Question 27

Question
What is the overall equation for a light phase of Photosynthesis?
Answer
  • 18CO2+ 2 NADPH + 3 ATP + light → 2 NADPH + 3 Glucose + 3 ADP + 18O2
  • 2 H2O + 2 NADP+ + 3 ADP + 3 Pi + light → 2 NADPH + 2 H+ + 3 ATP + O2
  • 2 H2O + 2 NAD+ 2 Pi → 2 NADPH + 2 H+ + O2 + light
  • CO2 + light + H2O → Glucose + O2

Question 28

Question
Uncouplers inhibit Mitochondrial Oxidative Phosphorylation due to:
Answer
  • Inhibition of respiratory chain
  • Their ability to translocate protons and dissipate the membrane potential
  • Inhibition of ATP-hydrolysis
  • Inhibition of glycolysis

Question 29

Question
Which of the following statements about light phase of Photosynthesis is incorrect?
Answer
  • Proton-translocating ATP-synthase of thylakoid membrane can synthesise ATP
  • Photosystem I and II can capture light quanta
  • The thylakoid membrane is negatively charged on the lumen side
  • The proton motive force can be used for active transport

Question 30

Question
In biochemical pathways the metabolic cycles are:
Answer
  • Compounds which occur at cross-over or branching points in metabolic pathways
  • Initial substrates which feed into metabolic pathways
  • Compounds which catalyse the individual steps in a metabolic pathway
  • Metabolic hubs which allow the use and re-use of relatively small numbers of molecules

Question 31

Question
Protein degradation is an example of which type of biochemical pathway?
Answer
  • Anabolic
  • Catabolic
  • Amphibolic
  • Hyperbolic

Question 32

Question
Which of the following is true of endotherms?
Answer
  • They generate most of their heat through internal processes
  • They get most of their heat from the environment
  • They generate most of their heat from external processes
  • They cannot regulate their body temperature

Question 33

Question
Which ONE of the following statements are true for the sympathetic nervous system?
Answer
  • It prepares us for strenuous muscular activity
  • It prepares us for relaxing (non-strenuous) activity
  • It is one of 3 autonomic nervous systems
  • It is a part of the endocrine system

Question 34

Question
Diabetes insipidus is a disease caused by:
Answer
  • A lack of insulin
  • A lack of ADH
  • A lack of oxytocin
  • An excess of insulin

Question 35

Question
Cyclic AMP is:
Answer
  • An activator of pyruvate kinase C
  • An activator of protein kinase A
  • The product of adenylate kinase
  • An activator of phosphofructokinase-1

Question 36

Question
Phosphofructokinase-1 Activity is:
Answer
  • stimulated by citrate
  • inhibited by citrate
  • inhibited by AMP
  • inhibited by fructose 2,6-bisphosphate

Question 37

Question
Glycogen Phosphorylase is:
Answer
  • inhibited by AMP
  • activated by phosphorylation
  • activated by glucose
  • inhibited by phosphorylation

Question 38

Question
Protein Kinase A:
Answer
  • is an allosteric enzyme
  • is activated by ADP
  • phosphorylates glycogen phosphorylase
  • phosphorylates phosphorylase kinase

Question 39

Question
Cancer cells produce large amounts of Lactate even in the presence of Oxygen because they:
Answer
  • Lack mitochondria
  • Lack the gene for citrate synthase
  • Possess an over-active glycerol phosphate shuttle
  • Have a defective glycerol phosphate shuttle

Question 40

Question
We know relatively little about the metabolism of the liver fluke. What is the most realistic prediction about galactose metabolism in this organism compared to the one we know about in humans?
Answer
  • It will follow the Leloir pathway like in humans
  • It will follow a different pathway because it is a parasite
  • It will follow a different pathway because it eats different food
  • We cannot make any realistic predictions
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