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122.101 Biochemistry of Cells > Exam Study > Flashcards

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1
Q

An amino acid residue that is a secondary amine and prevents alpha helix formation is:

A

Proline.

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2
Q

What can enzyme activity be affected by?

A
  • pH
  • temperature
  • substrate concentration
  • concentration of the product
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3
Q

Humans can digest starch but not cellulose because:

A

Humans have enzymes that can hydrolyse the a-glycosidic linkages of starch but not the b-glycosidic linkages of cellulose.

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4
Q

A molecule with the formula C18H36O2 is probably a:

A

Fatty acid.

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5
Q

In facilitated diffusion, what is the main role of transport proteins?

A

Transport proteins provide hydrophillic routes for specific solutes to cross membranes.

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6
Q

What is substrate-level phosphorylation?

A

ATP synthesis when the phosphate donor is a molecule with high phosphoric group transfer potential.

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7
Q

What is an allosteric effector of phosphofructokinase?

A

Citrate.

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8
Q 
Which of the enzymes below acts in the conversion of glucose-6- phosphate to fructose-6-
phosphate
A. Kinase
B. Isomerase
C. Phosphatase
D. Mutase
E. Dehydrogenase
A

B. Isomerase

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9
Q

The net product of anaerobic glycolysis are

A

ATP, lactate.

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10
Q

Which process is NOT increased in the presence of insulin? (looking for lowering blood
sugar)

A

Gluconeogenesis in the liver.

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11
Q

Which type of interaction stabilizes the alpha (α) helix and the beta (β) pleated sheet structures of proteins?

A

Hydrogen bonds.

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12
Q

The effects of insulin on glucose uptake by muscle tissue are most directly opposed by
(insulin lowers blood sugar)

A

Glucagon (raises blood sugar).

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13
Q

Glycolysis will cease if:

A

NADH is not oxidised.

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14
Q

The disaccharide lactose is composed of

A

Glucose and galactose

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15
Q

Glycolysis is only partially reversible because of energy barriers at the reactions catalyzed
by

A

Hexokinase, phosphofructokinase, and pyruvate kinase

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16
Q

An increase in glucagon will cause

A

An increase in the liver glycogenolysis

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17
Q

Galactose is found in the hydrolytic products of

A

Lactose

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18
Q

The main organ responsible for keeping blood glucose level steady between meals by
making glucose via gluconeogenesis is the

A

Liver

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19
Q

Sucrose is a disaccharide composed of___ linked to ___.

A

Glucose, fructose.

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20
Q 
Which of the following would stimulate the principal controlled step of glycolysis?
A. ATP
B. Citrate
C. Fructose 2,6-bisphosphate
D. Glucose-6- phosphate
E. Fructose 1,6-bisphosphate
A

C. Fructose 2,6-biphosphate

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21
Q

What is the approximate yield of ATP (from ADP) when one residues of glucose, released
from glycogen, is converted to lactic acid under anaerobic conditions?

A

2

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22
Q

Using a signal transduction pathway, glucagon influences the activity of the enzyme that
catalyzes the formation of

A

Fructose 2,6-biphosphate

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23
Q

The NET products of aerobic glycolysis are

A

acetyl-CoA, NADH, ATP

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24
Q

The substrate for the committed step in glycolysis is

A

fructose-6-phosphate

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25
Q

Glucagon plays a homeostatic role by

A

Being released from the pancreas in response to lowered blood glucose levels and then
activating the liver phosphorylase system

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26
Q

Biotin participates in the reaction catalyzed by

A

Pyruvate carboxylase

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27
Q

Glycogen in muscle

A

Serves as a source of fuel for ATP synthesis within that tissue

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28
Q

The immediate event that occurs to glucose on entering a liver cell that prevents the glucose

A

Phosphorylation at C-6

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29
Q

The most important enzyme in the physiological regulation of glycolysis is

A

Phosphofructokinase

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30
Q

An enzyme in the glycolytic pathway that results in the conversion of hexose-bisphosphate
into triose-phosphates is

A

Aldolase

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31
Q

In the malate-asparatate shuffle, electrons are transferred from NADH to

A

Ocaloacetate

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32
Q

All enzymes of the citric acid cycle except for succinate dehydrogenase are found in the

A

Mitochondrial matrix

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33
Q

Mitochondrial synthesis of ATP by ATP synthase is driven by

A

Movement of protons from the inter membrane space to the matrix of the mitochondrion.

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34
Q

ATP for gluconeogenesis comes mainly from

A

Fatty acid oxidation

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35
Q

Aminotransferase enzymes do what?

A

Catalyse the transfer of an a-amino group to an a-keto acid.

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36
Q

Mysoin heads have binding sites for..

A

Actin and ATP.

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37
Q

Skeletal muscle deprived of adequate ATP will

A

Enter a state where actin and myosin are unable to seperate.

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38
Q

In chloroplasts, chemiosmosis translocates protons from

A

The matrix to the stroma.

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39
Q

The process of photosynthesis cannot occur in the absence of..

A

Carbon dioxide.

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40
Q

The pI of an amino acid is the pH at which

A

There is an equal number of positive and negative charges found on the molecule.

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41
Q

An enzymes specificity is likely to be due to

A

Molecular recognition based on structural complementarily.

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42
Q 
Which of the following fatty acids is mono-unsaturated?
A. Stearic acid 
B. Oleic acid
C. Linoleic acid
D. a-linoleic acid
A

Oleic acid.

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43
Q

Phospholipid bilayers are highly permeable to

A

O2

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44
Q

The function of the Na+/K+ ATPase pump is to

A

Actively co-transport Na+ out of the cell and K+ into the cell.

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45
Q

The pyruvate carboxylase reaction

A

Provides oxaloacetate for the TCA cycle.

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46
Q

When glucose enters a liver cell it is immediately

A

Phosphorylated at carbon 6

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47
Q

Where does fatty acid synthesis occur?

A

In the cytsol

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48
Q

The Calvin cycle takes place in the

A

Stroma of the chloroplast

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49
Q

What are isoenzymes?

A

Different enzymes that catalyse the same reaction.

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50
Q

The end products of anaerobic glycolysis are

A

Lactate and ATP

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51
Q

The glycerol-phosphate shuttle transports reducing equivalents in

A

NADH/H+ from the cytosol across the inner mitochondrial membrane.

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52
Q

The mitochondrial electron transport chain is regulated by the availabilty of

A

NADH/H+ and ADP.

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53
Q

What does pyruvate carboxylase do

A

Replenish oxaloaxetate for the TCA

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54
Q

The transverse tubules of a muscle cell are specialised regions of the

A

Plasma membrane

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55
Q

Photosynthesis depends on light from which regions of the spectrum

A

Visible

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56
Q

The excitation energy from light is transferred within the photosynthetic light harvesting complex by

A

Resonance energy transfer

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57
Q

What is the enzyme responsible for CO2 fixation during photosynthesis is

A

Ribulose-1:5-biphosphate carboxylase/oxygenase

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58
Q

Describe the a-helix

A

A-helices are curled, ribbon-like helical structures which are held together by hydrogen bonds.

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59
Q

Describe the bonds within the a-helix

A

The carbonyl of 1 amino acid is bonded to the animo H of another amino acid which is 4 down the chain. R-groups stick out from the a-helix where they are free to interact.

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60
Q

Describe the B-pleated sheet

A

B-pleated sheets are two or more segments of the polypeptide chain which line up next to each other to form a sheet like structure.

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61
Q

Explain the bonding within the B-pleated sheet

A

The hydrogen bonds form between carbonyl and amino groups of the backbone, whilst R groups extend above and below the plane of the sheet.

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62
Q

Describe the non-covalent interactions that contribute to the structure of a globular protein in aqueous solution

A

The proteins hydrophobic amino acids are bounded towards the molecules interior where as the hydrophillic amino acids are bounded outwards, allowing dipole-dipole interactions with solvents and thus making them water soluble.

63
Q

Why does Hb have a different binding curve to Mb?

A

Hb is a tetrameric protein with 4 subunits (2- a globin and 2 B-globin, each with an associated haem molecule). MB is a monomeric protein. Hb produces a sigmoidal curve because of its significantly more complex structure. Mb produces a hyperbolic curve.

64
Q

What is the importance of BPG?

A

Hb unloads O2 to the tissues and BPG binds to any deoxyHb, and holds it in the T-state. This means that the O2 cannot re-bind to Hb. Any free un-bound O2 can therefore be taken up by Mb.

65
Q

Where on the Hb molecule does BPG bind and what are the interactions involved?

A

Binds in the central cavity of the T-state Hb. The anion groups of BPG are within Hb0bonding and ion-pairing distances of both the N-terminal amino group of both B sub-units.

66
Q

What does Km mean

A

The substrate concentration at which velocity is exactly 1/2 of Vmax

67
Q

What does Vmax mean

A

The rate of reaction when enzyme is saturated with substrate

68
Q

Why are Vmax and Km important

A
  • To predict the metabolic fate of substrate

- To predict the relative amount that will flow through each pathway

69
Q

What is enzyme specificity?

A

Enzyme specificity is the ability of an enzyme, through molecular recognition mechanisms and structural and conformational complementarity to choose exact substrate from a group of chemically similar molecules.

70
Q

Why does pH affect enzyme activity?

A

Reducing/increasing the pH away from optimum pH reduces the rate of reaction because the H+ conc, in solution affects the tertiary structure of the enzyme molecules.

71
Q

What is facilitated diffusion?

A

The process of spontaneous passive transport of molecules/ions across a biological membrane via specific transmembrane integral proteins.

72
Q

What is active transport?

A

The movement of ions/molecules across a cell membrane into a region of higher conc. assisted by enzymes requiring energy.

73
Q

What is a catabolic reaction?

A

Catabolic reactions break down large organic molecules into smaller molecules, in turn releasing the energy which is contained in the chemical bonds. It is a degradative pathway.

74
Q

What is an anabolic reaction?

A

Also known as a biosynthesis reaction, anabolic reactions are the joining of smaller molecules into larger ones, requiring energy.

75
Q

How are catabolic and anabolic reactions linked?

A

Anabolic reactions require the use of the ATP produced by the catabolic reactions.

76
Q

Describe the pyruvate dehydrogenase reaction

A

Pyruvate dehydrogenase is a complex of 3 enzymes that converts pyruvate into acetyl-CoA by pyruvate decarboxylation.

77
Q

What is the metabolic importance of the pyruvate dehydrogenase reaction

A

The acetyl-CoA may then be used in the citric acid cycle;e to carry out cellular respiration and this complex links the glycolysis metabolic pathway to the citric acid cycle.

78
Q

Why is glycogen an important fuel reserve

A
  • Important buffer to maintain blood-glucose levels
  • Glucose from glycogen is readily mobilised and is a goof source of energy for sudden, strenuous activity
  • Glucose can provide energy in the absence of oxygen and can thus supply energy for anaerobic activity.
79
Q

Why do glycogen synthesis and glycogen breakdown do not occur at the same time

A

Glycogen breakdown and synthesis are reciprocally regulated by a hormone-triggered cAMP cascade acting through protein kinase A. Otherwise they would occur in a large futile cycle.

80
Q

Why does NADH/H+ yields more ATP than FADH2 when it is deoxidised in the mitochondrial electron transport chain

A

FADH2 makes less ATP because it enters the electron transport chain at a later stage than NADH, and activates less proton pumps in the stage.

81
Q

Explain the regulation of gluconeogenesis and glycolysis

A

They are co-ordinated within a cell so that one pathway is inactive and the other pathway is highly active. Both reactions are highly exergonic and under cellular conditions and there is no thermodynamic barrier to the simultaneous activity. The amounts and activities are controlled. The rate of glycolysis is determined by the conc. of glucose, the rate of gluconeogenesis is detemined by the conc. of lactose.

82
Q

Explain the metabolic importance of the reaction catalysed by lactate dehydrogenase in anaerobic glycolysis

A

Lactate dehydrogenase catalyses the conversion of lactate to pyruvate and back, converting NAD+ to NADH. It is a key enzyme in anaerobic respiration, catalysing the final step in anaerobic glycolysis.

83
Q

Explain the primary structure of a globular protein

A

A sequence of polypeptides or a chain of amino acids joined by peptide bonds.

84
Q

Explain the secondary structure of a globular protein

A

Alpha-helices (ribbon shaped helical structures) and beta sheets held together by H bonds between carboxyl and amine groups of the amino acids.

85
Q

Explain the tertiary structure of a globular protein

A

The folding of helices and sheets. Polar/hydrophilic amino acids on the outside - non-polar/hydrophobic amino acids on the inside, creates the 3D shape responsible for solubility.

86
Q

Which of the following statements about enzyme-catalysed reactions is TRUE?
A) The reaction is faster than the same reaction in the absence of the enzyme.
B) The free energy change of the reaction is opposite to the free energy change of the reaction in the absence of the enzyme.
C) The reaction always goes in the direction toward chemical equilibrium.
D) Enzymes cause a reaction to take place that would not normally do so.
E) There are many side-reactions.

A

A) The reaction is faster than the same reaction in the absence of the enzyme.

87
Q

Which of the following statements about a typical plasma membrane is correct?
A) The hydrophilic interior of the plasma membrane is composed primarily of
the fatty acyl chains of phospholipids.
B) The two sides of the plasma membrane have different lipid and protein
compositions.
C) Phospholipids are the primary component that determines which solutes
can cross the plasma membrane.
D) The plasma membrane is a covalently linked network of phospholipids and
proteins that controls the movement of solutes into and out of a cell.
E) Glycoproteins that are integrated into the plasma membrane have no effect

A

B) The two sides of the plasma membrane have different lipid and protein

88
Q

Increased levels of ATP inhibit which pair of enzymes?
A) glyceraldehyde 3-phosphate dehydrogenase and enolase B) lactate dehydrogenase and triose phosphate isomerase C) phosphofructokinase and pyruvate kinase
D) phosphofructokinase and glucose 6-phosphate isomerase E) glucokinase and phosphoglycerate mutase

A

C) phosphofructokinase and pyruvate kinase

89
Q

Which of the following molecules is a negative allosteric effector of phosphofructokinase?
A) Succinic acid B) ADP
C) Oxaloacetate D) ATP
E) All of the above

A

D. ATP

90
Q 
In the malate-aspartate shuttle, electrons are transferred from NADH to
A) oxaloacetate.
B) aspartate.
C) acetate.
D) glutamate.
E) dihydroxyacetone phosphate.
A

A. Oxaloacetate

91
Q
  1. Which of the following statements about the glycerol-phosphate and malate- aspartate shuttles is TRUE?
    A) Both shuttles serve to mediate transport of FADH2 across the inner mitochondrial membrane.
    B) The glycerol-phosphate shuttle transports NADH across the outer mitochondrial membrane, while the malate-aspartate shuttle transports NADH across the inner mitochondrial membrane.
    C) The malate-aspartate shuttle is a less energy-efficient means of transporting metabolites across the mitochondrial membrane.
    D) FAD serves as the oxidising agent in the mitochondrial matrix with the glycerol-phosphate shuttle.
    E) ATP yield from use of the malate-aspartate shuttle is higher than ATP yield from use of the glycerol-phosphate shuttle.
A

E) ATP yield from use of the malate-aspartate shuttle is higher than ATP yield from use of the glycerol-phosphate shuttle.

92
Q

The activity of pyruvate dehydrogenase (PDH) decreases
A) as the concentration of acetyl-CoA decreases. B) as the concentration of NAD+ increases.
C) when it is phosphorylated.
D) as the concentration of pyruvate increases.
E) as the concentration of AMP increases.

A

C) when it is phosphorylated.

93
Q 
The citric acid cycle is slowed by which of the following?
A) ADP and AMP
B) ADP and oxaloacetate
C) NAD+ and ADP
D) NADH and ATP
E) NAD+ and oxaloacetate
A

D) NADH and ATP

94
Q 
Which of the following is NOT a substrate for gluconeogenesis?
A) Lactate
B) Pyruvate
C) Leucine
D) Alanine
E) Glycerol
A

C. Leucine

95
Q 
ATP for gluconeogenesis comes mainly from
A) glycolysis.
B) fatty acid oxidation.
C) glycogen breakdown.
D) substrate-level phosphorylation.
E) lactate.
A

B. Fatty acid oxidation

96
Q

Aminotransferase enzymes

A

catalyse the transfer of an α-amino group to an α-keto acid.

97
Q

Which of the following does NOT apply to fatty acid synthesis?
A) The pathway occurs in the mitochondrion.
B) ATP is provided from aerobic catabolism of glucose.
C) The acetyl-CoA used as a precursor is generated from citrate.
D) It takes place in the liver.
E) It takes place in adipose tissue.

A

A. The pathway occurs in the mitochondrion.

98
Q

Which of the following statements is NOT true?
A) Most amino acids can be converted to glucose.
B) Acetyl-CoA can be converted to glucose in animals.
C) Ketogenic amino acids can be converted to ketone bodies.
D) Excess production of ketone bodies results in the spontaneous production of acetone.
E) Some amino acids are both glucogenic and ketogenic.

A

B. Acetyl-CoA can be converted into glucose in animals.

99
Q

The contraction of skeletal muscles is based on
A) actin and myosin filaments both coiling up to become shorter.
B) myosin filaments coiling up to become shorter.
C) actin filaments coiling up to become shorter.
D) myosin cross-bridges binding to actin and undergoing a conformational
change to generate force.
E) actin cross-bridges binding to myosin and undergoing a conformational

A

D. Myosin cross bridges binding to actin and undergoing a conformational change to generate force.

100
Q

Skeletal muscle deprived of adequate ATP will
A) fire many more action potentials than usual.
B) immediately relax.
C) release all actin-myosin cross-bridges.
D) enter a state where actin and myosin are unable to separate.
E) sequester all free calcium ions into the sarcoplasmic reticulum.

A

D. Enter a state where myosin and actin are unable to seperate.

101
Q

In chloroplasts, chemiosmosis translocates protons from
A) the stroma to photosystem II.
B) the thylakoid lumen to the stroma.
C) the matrix to the stroma.
D) the intermembrane space to the matrix.
E) the stroma to the thylakoid lumen.

A

B. The thylakoid lumen to the stroma.

102
Q

In photosynthesis the reactions that produce O2 take place in
A) both the light reactions and the Calvin cycle.
B) the light reactions alone.
C) the chloroplast, but are not part of photosynthesis.
D) the Calvin cycle alone.
E) neither the light reactions nor the Calvin cycle.

A

B. The light reactions alone.

103
Q 
The amino acid side-chain that most commonly interacts to form covalent bonds in proteins
A) contains an amino group.
B) contains a sulfhydryl group.
C) is that of histidine.
D) is that of glutamate.
A

B. Contains a sulfhydyrl group.

104
Q

Isoenzymes are
A) proteolytic enzymes which are activated by the hydrolysis of a part of the peptide chain.
B) enzymes containing identical amino acid compositions and sequences but which catalyse different reactions.
C) different enzymes which catalyse the same reaction.
D) enzymes which catalyse several different reactions.

A

B) enzymes containing identical amino acid compositions and sequences but which catalyse different reactions.

105
Q

In the case of an enzyme displaying a sigmoidal relationship between velocity and substrate concentration [S], it can be concluded that
A) the enzyme contains only one binding site for substrate.
B) substrate binds more easily at low [S] than at high [S].
C) the enzyme must contain at least four subunits.
D) the binding of one substrate molecule facilitates the binding of others.

A

D) the binding of one substrate molecule facilitates the binding of others.

106
Q 
Which substrate is used to transfer phosphate directly to ADP?
A) 3-phosphoglycerate.
B) Fructose-1,6-bis phosphate.
C) Phosphoenolpyruvate.
D) 2-phosphoglycerate.
A

C) Phosphoenolpyruvate.

107
Q 
Which of the following compounds are in their oxidised form?
A) NAD+, NADP+ and FAD
B) NADH, NADPH and FAD
C) NADH, NADPH and FADH2
D) NAD+, NADP+ and FADH2
A

A) NAD+, NADP+ and FAD

108
Q

When a high energy compound undergoes hydrolytic cleavage
A) there is a decrease in resonance.
B) there is a large decrease in free energy content between reactant and products.
C) the redox potential is lowered.
D) the equilibrium constant increases.

A

B) there is a large decrease in free energy content between reactant and products.

109
Q 
The formation of GTP in the citric acid cycle is an example of
A) oxidation.
B) oxidative phosphorylation.
C) reduction.
D) substrate level phosphorylation.
A

D) substrate level phosphorylation.

110
Q 
In the malate-aspartate shuttle, electrons are transferred from NADH to
A) oxaloacetate.
B) aspartate.
C) malate.
D) glutamate.
A

A) oxaloacetate.

111
Q

The glycerol-phosphate shuttle transports reducing equivalents in
A) FADH2 from the cytosol across the inner mitochondrial membrane.
B) NADH/H+ from the cytosol across the inner mitochondrial membrane.
C) NADPH/H+ from the cytosol across the inner mitochondrial membrane.
D) either FADH2 or NADH/H+ from the cytosol across the inner mitochondrial membrane.

A

B) NADH/H+ from the cytosol across the inner mitochondrial membrane.

112
Q

The activity of pyruvate dehydrogenase (PDH) increases when
A) the concentration of acetyl CoA increases.
B) the concentration of pyruvate decreases.
C) the enzyme is phosphorylated.
D) the enzyme is not phosphorylated.

A

D) the enzyme is not phosphorylated.

113
Q 
The mitochondrial electron transport chain is regulated by the availability of
A) NAD+.
B) NADH/H+ and ADP.
C) NAD+ and ADP.
D) NADH/H+ and ATP.
A

B) NADH/H+ and ADP.

114
Q

The DGo’ of malate dehydrogenase is strongly positive but the reaction proceeds in the direction of oxaloacetate because
A) the reaction favours the production of oxaloacetate.
B) the mitochondrial oxaloacetate concentration is high.
C) citrate synthase has a high KM for oxaloacetate.
D) citrate synthase uses up the oxaloacetate.

A

D) citrate synthase uses up the oxaloacetate.

115
Q

Pyruvate carboxylase
A) replenishes oxaloacetate for the citric acid cycle.
B) converts pyruvate into acetyl CoA to start the citric acid cycle.
C) reduces pyruvate to lactate at the end of glycolysis.
D) replenishes malate for the citric acid cycle.

A

A) replenishes oxaloacetate for the citric acid cycle

116
Q

If a redox couple has a negative reduction potential it can
A) accept electrons from redox couples with positive reduction potentials.
B) donate electrons to redox couples with positive reduction potentials.
C) be used to make ATP.
D) not be used to make ATP.

A

B) donate electrons to redox couples with positive reduction potentials.

117
Q 
The tranverse tubules of a muscle cell are specialised regions of the
A) plasma membrane.
B) sarcoplasmic reticulum.
C) thick filaments.
D) thin filaments.
A

A) plasma membrane.

118
Q 
Photosynthesis depends on light from which region(s) of the spectrum?
A) Ultraviolet.
B) Visible.
C) Visible and infrared.
D) Infrared.
A

C) Visible and infrared.

119
Q

The enzyme responsible for CO2 fixation during photosynthesis is
A) glyceraldehyde-3-phosphate dehydrogenase.
B) phosphoglycerate kinase.
C) ribulose-1:5-bisphosphate carboxylase/oxygenase.
D) ferridoxin reductase.

A

C) ribulose-1:5-bisphosphate carboxylase/oxygenase.

120
Q

Which of the following statements about protein structure is correct?
A) Alpha helices are stabilised by hydrophobic interactions.
B) Beta sheets are rarely found in globular proteins.
C) A globular protein has an interior enriched with hydrophobic amino acids.
D) The primary structure does not influence the native tertiary structure.

A

C) A globular protein has an interior enriched with hydrophobic amino acids.

121
Q 
Which one of the following features does not apply to enzymes?
A) Regulation.
B) Ability to change DG.
C) Catalytic activity.
D) Specificity.
A

B) Ability to change DG.

122
Q 
The term Vmax refers to
A) maximum enzyme concentration.
B) maximum volume.
C) substrate concentration at the maximum velocity.
D) maximal reaction rate.
A

D) maximal reaction rate.

123
Q 
An example of a coenzyme is
A) an iron-sulphur cluster.
B) Zn2+
C) heme.
D) NAD+
A

D) NAD+

124
Q 
The enzyme amylase can hydrolyse glycosidic linkages between glucose monomers only if the monomers are in the alpha form. Which of the following could amylase hydrolyse?
A) Starch and chitin
B) Glycogen and cellulose
C) Glycogen and amylopectin
D) Amylose and cellulose
A

C) Glycogen and amylopectin

125
Q

Which of the following characteristics is unique to active transport?
A) The transport of hydrophobic molecules.
B) The transport of hydrophilic molecules.
C) The movement of molecules or ions across a membrane from a higher to a lower concentration.
D) An input of energy.

A

D) An input of energy.

126
Q

A high energy bond is a bond
A) which is highly unstable.
B) which is highly exergonic.
C) with a high phosphate group transfer potential.
D) with a large negative free energy change on hydrolysis.

A

D) with a large negative free energy change on hydrolysis.

127
Q

If DG for a reaction is large and negative, the reaction
A) will be at equilibrium.
B) will proceed in the direction as written.
C) in the opposite direction will be favoured.
D) will need an enzyme to proceed in the direction as written.

A

B) will proceed in the direction as written.

128
Q

How many molecules of NAD+ are reduced to NADH/H+ as one molecule of pyruvate is metabolised to CO2?
A) 2 B) 3 C) 4 D) 5

A

C. 4

129
Q

Which of the following statements about mitochondria is correct?
A) The outer mitochondrial membrane is extensively folded.
B) The mitochondrial matrix is filled with a concentrated solution of glycolytic enzymes.
C) The inner mitochondrial membrane is extensively folded.
D) The inner mitochondrial membrane is freely permeable to all substances.

A

C) The inner mitochondrial membrane is extensively folded.

130
Q

Which of the following statements is correct?
A) The NADH/H+ produced in aerobic glycolysis is reoxidised by lactate dehydrogenase.
B) The mitochondrial inner membrane is permeable to NADH/H+.
C) Shuttle systems transport reducing equivalents across the mitochondrial inner membrane.
D) Shuttle systems transport NADH/H+ produced in aerobic glycolysis across the mitochondrial inner membrane.

A

C) Shuttle systems transport reducing equivalents across the mitochondrial inner membrane.

131
Q 
When glucose enters a liver cell it is immediately
A) converted into lactate.
B) phosphorylated at carbon 6.
C) phosphorylated at carbon 1.
D) converted into glycogen.
A

B) phosphorylated at carbon 6.

132
Q

Which of the following pathways are more active in the fasting state than in the fed state?
A) Glycogen synthesis, glycolysis and fatty acid oxidation.
B) Glycogen breakdown, glycolysis and fatty acid oxidation.
C) Glycogen breakdown, fatty acid oxidation and ketone body synthesis.
D) Glycogen breakdown, glycolysis and ketone body synthesis.

A

C) Glycogen breakdown, fatty acid oxidation and ketone body synthesis.

133
Q

Ketone bodies
A) are produced in all tissues when acetyl-CoA levels are high.
B) can be used as an energy source in liver.
C) are only used by the brain when glucose levels are low.
D) are made in the liver and used in most tissues except the liver.

A

D) are made in the liver and used in most tissues except the liver.

134
Q

Creatine phosphate acts as an energy reserve in exercising muscle when ATP is depleted because
A) myosin can use creatine phosphate instead of ATP for force production.
B) creatine phosphate can be used by creatine kinase to convert ADP to ATP.
C) creatine phosphate binds to troponin.
D) creatine phosphate binds to tropomyosin.

A

D) creatine phosphate binds to tropomyosin.

135
Q 
In muscle cells, the "cross-bridges" that link thick and thin filaments are formed by
A) F-actin.
B) the globular head of thick filaments.
C) the tails of myosin filaments.
D) globular actin.
A

B) the globular head of thick filaments.

136
Q

Type I muscle has a higher concentration of mitochondria than type II muscle. Which of the following best describes ATP production in these two muscle types?
A) Type I muscle relies on oxidative phosphorylation and type II muscle relies on glycolytic substrate level phosphorylation.
B) Type I muscle relies on glycolytic substrate level phosphorylation and type II muscle relies on oxidative phosphorylation.
C) Type I and II muscle use oxidative and glycolytic substrate level phosphorylation equally.
D) Type I and II muscle produce very little ATP and import it from other tissues.

A

A) Type I muscle relies on oxidative phosphorylation and type II muscle relies on glycolytic substrate level phosphorylation.

137
Q 
The Calvin cycle takes place in the
A) cytoplasm surrounding the chloroplast.
B) thylakoid membrane.
C) stroma of the chloroplast.
D) chlorophyll molecules.
A

C) stroma of the chloroplast.

138
Q

The sequence of reactions in the production of glyceraldehyde-3-phosphate in the Calvin cycle is:
A) CO2 fixation, phosphorylation, oxidation.
B) CO2 fixation, phosphorylation, reduction.
C) H2O oxidation, NADPH oxidation.
D) H2O oxidation, H+ transfer.

A

B) CO2 fixation, phosphorylation, reduction.

139
Q 
Which of the following statements regarding chloroplast cyclic photophosphorylation is false?
A) Light is required.
B) NADP+ is required.
C) Photosystem I is required.
D) Cytochrome b6f is required.
A

B) NADP+ is required.

140
Q

What is the role of glycogen in the liver

A

Glycogen stores within the liver serve as a store of glucose for the use throughout the whole body, but particularly the CNS.

141
Q

What is the role of glycogen within muscle

A

An energy store for muscle cells. The breakdown of muscle glycogen impedes muscle glucose uptake from the blood, increasing the amount of blood glucose available to other tissues.

142
Q

Why is muscle glycogen and liver glycogen different

A

Muscle cells lack glucose-6-phosphate so cannot pass glucose into the blood, the glycogen they store is purely for internal use.

143
Q

What are the metabolic conditions that cause ketone body synthesis in the liver

A

Produced mainly in the mitochondria of liver cells. Synthesis usually occurs as a response to unavailability of blood glucose, such as during fasting.

144
Q

Why can animals not synthesis glucose from acetyl-CoA

A

Because fatty acids are metabolised 2 carbons at a time into the acetyl units of acetyl-CoA and we lack the enzymes to convert acetyl-CoA into pyruvate or any other metabolite in the gluconeogenesis pathway.

145
Q

What happens to triaglycerols stored in adipose tissue when blood glucose levels are low

A

When blood glucose is low, triaglycerols are converted into acetyl-CoA and used to generate ATP through aerobic respiration.

146
Q

Explain the oxidation of fatty acids

A

The first stage is B-oxidation where 2 carbons units are cleaved off from the carboxyl end of fatty acyl-CoA with the formation of acetyl-CoA. These acetyl units formed participate in the Kreb’s cycle, forming NADH and FADH2. These reduced coenzymes are oxidised, giving up their protons and electrons to O2 present in the mitochondria, to synthesis ATP by the ETC.

147
Q

What is the role of sarcoplasmic reticulum in muscle contraction and relaxation

A

Muscle contraction is stimulated by the influx of calcium ions which causes re-arrangement of actin-associated proteins. Muscle relaxation occurs at low Ca2+ levels.

148
Q

how is light energy captured and transferred to the phtosynthetic reaction centre

A

Light energy is absorbed directly by pigment molecules, or passed to them by resonance transfer from antenna pigments. The reaction centre catches the energy of photons using the pigment molecules.

149
Q

Explain the swinging cross-bridge model of muscle contraction

A

Within the sarcomere, myosin slides along actin to contract the muscle fibre in a process that requires ATP. Myosin reaches forward, binds to actin, contracts, releases actin and reaches forward in a new cycle again, in turn producing cross bridges.

150
Q

Why do glycogen synthesis and glycogen breakdown not occur at the same time

A

Reciprocally regulated by a hormone triggered cAMP cascade acting through protein kinase A.

151
Q

Why does NADH/H+ make more ATP than FADH2 does

A

FADH2 makes less ATP because it enters the electron transport chain at a later stage than NADH and activates less proton pumps in the chain.

152
Q

What is the reaction catalysed by lactate dehydrogenase in anaerobic glycolysis

A

Lactate dehydrogenase catalyses the conversion of lactate to pyruvate and back, converting NAD+ to NADH. It is a key enzyme in anaerobic respiration, and the final step in anaerobic glycolysis.

153
Q

Describe the pyruvate dehydrogenase reaction

A

Pyruvate dehydrogenase is a complex of 3 enzymes that converts pyruvate into acetyl-CoA by pyruvate decarboxylation. The acetyl-CoA may then be used in the citric acid cycle to carry out cellular respiration and this complex links the glycolysis metabolic pathway to the citric acid cycle.

122.101 Biochemistry of Cells (3 decks)

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