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Papers covered; - August 2013

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Biochemistry MCQ's

Pregunta 1 de 40

1

The redox centre of FAD is

Selecciona una de las siguientes respuestas posibles:

  • Flavin mononucleotide (FMN)

  • Nicotinamide

  • Adenosine

  • Phosphate

Explicación

Pregunta 2 de 40

1

Which of the following nucleotide triphosphates is often involved in signal transduction and also provides the energy for ribosomal translocation?

Selecciona una de las siguientes respuestas posibles:

  • CTP

  • TTP

  • UTP

  • GTP

Explicación

Pregunta 3 de 40

1

Which monosaccharide provides the main source of energy for sperm cells?

Selecciona una de las siguientes respuestas posibles:

  • Glucose

  • Fructose

  • Galactose

  • Mannose

Explicación

Pregunta 4 de 40

1

Which pathway(s) include phosphorylated seven carbon monosaccharides?

Selecciona una de las siguientes respuestas posibles:

  • Calvin cycle

  • Leloir pathway

  • Glycogen synthesis

  • All of the above

Explicación

Pregunta 5 de 40

1

The isomerisation of glucose 1-phosphate to glucose 6-phosphate occurs in which two pathways?

Selecciona una de las siguientes respuestas posibles:

  • Calvin cycle and glycogen synthesis

  • Leloir pathway and Calvin cycle

  • Leloir pathway and glycolysis

  • Leloir pathway and glycogen synthesis

Explicación

Pregunta 6 de 40

1

Steroids

Selecciona una de las siguientes respuestas posibles:

  • Are entirely hydrophobic molecules

  • Often act as hormones

  • Cannot pass through cell membranes

  • Are mainly hydrophilic molecules

Explicación

Pregunta 7 de 40

1

The sequence of reactions: oxidation-hydration-oxidation occurs in which two pathways?

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 8 de 40

1

The mobility of membrane phospholipids can be demonstrated by

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 9 de 40

1

Cholesterol is an example of what class of molecule?

Selecciona una de las siguientes respuestas posibles:

  • Sterol

  • Fatty acid

  • Ketose monosaccharide

  • Aldose monosaccharide

Explicación

Pregunta 10 de 40

1

In the Calvin cycle, how many molecules of carbon dioxide are required for the synthesis of one molecule of fructose 6-phosphate?

Selecciona una de las siguientes respuestas posibles:

  • 3

  • 4

  • 6

  • 12

Explicación

Pregunta 11 de 40

1

In cellulose, the glucose residues are bonded together by:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 12 de 40

1

Which of the following is not a reducing sugar?

Selecciona una de las siguientes respuestas posibles:

  • Sucrose

  • Maltose

  • Lactose

  • Galactose

Explicación

Pregunta 13 de 40

1

The carnitine cycle

Selecciona una de las siguientes respuestas posibles:

  • “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

Explicación

Pregunta 14 de 40

1

Glycerol can be used as a source of energy by conversion to the glycolytic intermediate dihydroxyacetone phosphate. Per molecule of glycerol, this process:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 15 de 40

1

Fatty acid synthesis:

Selecciona una de las siguientes respuestas posibles:

  • Requires NADH

  • Requires water as a reactant

  • Adds carbon atoms two at a time

  • All of the above

Explicación

Pregunta 16 de 40

1

In enzyme kinetics, the ratio of constants kcat/Km:

Selecciona una de las siguientes respuestas posibles:

  • 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.

Explicación

Pregunta 17 de 40

1

In enzyme catalysis, the term ‘approximation’ refers to:

Selecciona una de las siguientes respuestas posibles:

  • 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.

Explicación

Pregunta 18 de 40

1

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:

Selecciona una de las siguientes respuestas posibles:

  • Half of Vmax

  • Two thirds of Vmax

  • Double Vmax

  • Three times Vmax

Explicación

Pregunta 19 de 40

1

Koshland’s induced fit model for enzyme-substrate complex formation:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 20 de 40

1

Enzymes:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 21 de 40

1

The Michaelis constant, Km:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 22 de 40

1

The Vmax of an enzyme catalysed reaction:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 23 de 40

1

Proteosome-mediated proteolysis:

Selecciona una de las siguientes respuestas posibles:

  • 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.

Explicación

Pregunta 24 de 40

1

The Alanine Cycle:

Selecciona una de las siguientes respuestas posibles:

  • 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.

Explicación

Pregunta 25 de 40

1

Which of the following is a Redox Centre of Mitochondrial Respiratory Chain Enzymes?

Selecciona una de las siguientes respuestas posibles:

  • NADPH

  • Succinate

  • Oxygen

  • FMN, flavin

Explicación

Pregunta 26 de 40

1

In Photosynthesis energy of light Quanta is captured by a molecule of:

Selecciona una de las siguientes respuestas posibles:

  • Plastoquinone

  • Oxygen

  • Chlorophyll

  • Cytochrome c

Explicación

Pregunta 27 de 40

1

What is the overall equation for a light phase of Photosynthesis?

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 28 de 40

1

Uncouplers inhibit Mitochondrial Oxidative Phosphorylation due to:

Selecciona una de las siguientes respuestas posibles:

  • Inhibition of respiratory chain

  • Their ability to translocate protons and dissipate the membrane potential

  • Inhibition of ATP-hydrolysis

  • Inhibition of glycolysis

Explicación

Pregunta 29 de 40

1

Which of the following statements about light phase of Photosynthesis is incorrect?

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 30 de 40

1

In biochemical pathways the metabolic cycles are:

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 31 de 40

1

Protein degradation is an example of which type of biochemical pathway?

Selecciona una de las siguientes respuestas posibles:

  • Anabolic

  • Catabolic

  • Amphibolic

  • Hyperbolic

Explicación

Pregunta 32 de 40

1

Which of the following is true of endotherms?

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 33 de 40

1

Which ONE of the following statements are true for the sympathetic nervous system?

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

Pregunta 34 de 40

1

Diabetes insipidus is a disease caused by:

Selecciona una de las siguientes respuestas posibles:

  • A lack of insulin

  • A lack of ADH

  • A lack of oxytocin

  • An excess of insulin

Explicación

Pregunta 35 de 40

1

Cyclic AMP is:

Selecciona una de las siguientes respuestas posibles:

  • An activator of pyruvate kinase C

  • An activator of protein kinase A

  • The product of adenylate kinase

  • An activator of phosphofructokinase-1

Explicación

Pregunta 36 de 40

1

Phosphofructokinase-1 Activity is:

Selecciona una de las siguientes respuestas posibles:

  • stimulated by citrate

  • inhibited by citrate

  • inhibited by AMP

  • inhibited by fructose 2,6-bisphosphate

Explicación

Pregunta 37 de 40

1

Glycogen Phosphorylase is:

Selecciona una de las siguientes respuestas posibles:

  • inhibited by AMP

  • activated by phosphorylation

  • activated by glucose

  • inhibited by phosphorylation

Explicación

Pregunta 38 de 40

1

Protein Kinase A:

Selecciona una de las siguientes respuestas posibles:

  • is an allosteric enzyme

  • is activated by ADP

  • phosphorylates glycogen phosphorylase

  • phosphorylates phosphorylase kinase

Explicación

Pregunta 39 de 40

1

Cancer cells produce large amounts of Lactate even in the presence of Oxygen because they:

Selecciona una de las siguientes respuestas posibles:

  • Lack mitochondria

  • Lack the gene for citrate synthase

  • Possess an over-active glycerol phosphate shuttle

  • Have a defective glycerol phosphate shuttle

Explicación

Pregunta 40 de 40

1

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?

Selecciona una de las siguientes respuestas posibles:

  • 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

Explicación

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