Foundations of Metabolism Flashcards
Aside from maintaining the integrity of its hereditary material, the most important general metabolic concern of a cell is:
Maintaining a constant supply and concentration of ATP
A general process that breaks down large molecules into smaller ones is called:
catabolism
In metabolism, the advantage of multi-enzyme complexes and multi-function enzymes is:
intermediates can be moved very quickly to the next reaction in the pathway
Allosteric modification of enzyme activity can only happen if:
the enzyme has a second binding site for a molecule other than the substrate
Which statement is incorrect? Covalent modification of enzymes by phosphorylation (and dephosphorylation):
(a) is an important mode of hormonal control of enzyme activity
(b) involves addition or removal of phosphate groups
(c) involves modification of all types of amino acids
(d) involves the action of protein kinases
(e) none of the above
c
Which one of the following types of mechanisms is not known to play a role in the reversible alteration of enzyme activity?
(a) Activation by cleavage of an inactive zymogen
(b) Allosteric response to a regulatory molecule
(c) Alteration of the synthesis or degradation rate of an enzyme
(d) Covalent modification of the enzyme
(e) Interactions between catalytic and regulatory subunits
a
If the ΔG°’ of the reaction A −−> B is –40 kJ/mol, under standard conditions the reaction:
will proceed spontaneously from left to right.
Which of the following carrier molecules can be reduced in catabolic pathways?
(a) ADP
(b) FAD
(c) Phosphocreatine
(d) NADH
(e) Acetyl-CoA
b
Biological oxidation-reduction reactions always involve:
transfer of electron(s)
Phosphorylation at the expense of ATP is catalysed by enzymes belonging to which of the following groups or types of enzymes?
(a) protein kinases
(b) synthetases
(c) phosphatases
(d) phosphorylases
(e) (a) and (b) are correct
e
Which is usually the slowest way to regulate a reaction in a metabolic pathway?
(a) allosteric modulation
(b) covalent modification
(c) changing the enzyme concentration
(d) control of substrate/product concentrations
(e) all of the above are usually equally as fast
c
Which of the following is/are usually mechanisms that lead to quick changes in enzyme activity?
(a) Phosphorylation of rate-limiting enzymes
(b) Decreased concentration of allosteric effectors
(c) Proteolysis of enzymes at the committed step of a pathway
(d) Increased expression of enzymes from near equilibrium reactions
(e) Compartmentation of metabolic enzymes
a + b
Which statement is not true about catabolic pathways?
(a) They have a net release of energy.
(b) They have a net consumption of ATP.
(c) They liberate smaller molecules from larger ones.
(d) They include the citric acid cycle.
(e) None of the above are correct
b
Which of the following provides reducing equivalents for biosynthetic reactions?
(a) FAD
(b) NADPH.
(c) NAD+
(d) NADH
(e) NADP+
b
Anabolic and catabolic reactions in eukaryotes can occur simultaneously in cells. This is possible because
(a) they all occur in the cytosol
(b) the anabolic and catabolic pathways do not share any intermediate metabolites
(c) of the compartmentation of metabolites for the reactions of opposing pathways
(d) all catabolic reactions are exergonic and all anabolic reactions are endergonic
(e) allosteric regulation
c
ATP is classified as an energy-rich compound because
(a) the standard Gibbs free energy change (ΔG° ) of its de-phosphorylation is highly positive.
(b) it has a relatively low Gibbs free energy (G) of hydrolysis.
(c) its complete oxidation to carbon dioxide releases a large amount of energy.
(d) of the Gibbs free energy (G) released from cleavage of the phosphoanhydride bond.
(e) of the energy-rich thioester bond between adenosine and the phosphate groups.
d
The phosphorylation of ADP to ATP has a ΔG°’ of +31 kJ/mol. Under standard conditions, the reaction:
(a) is thermo-dynamically favorable.
(b) is near equilibrium.
(c) will occur spontaneously.
(d) will proceed when coupled with a highly exergonic reaction.
(e) requires the presence of an electron carrier.
d
The chemical energy generated by oxidation reactions cannot be captured by
(a) NADH.
(b) NADP.
(c) FAD.
(d) ADP.
(e) CoA.
a
In general, catabolic pathways break down major nutrients _____ resulting in the synthesis of _____
(a) exergonically; ADP
(b) endergonically; ADP
(c) exergonically; ATP
(d) endergonically; NADP+
(e) endergonically; ATP
c
Consider the following metabolic reaction:
Succinyl-CoA + Acetoacetate -> Acetoacetyl-CoA + Succinate ΔG°’ = –1.25 kJ/mol
The ΔG°’ for the hydrolysis of Succinyl-CoA is –33.9 kJ/mol.
What is the ΔG°’ for the hydrolysis of Acetoacetyl-CoA:
Acetoacetyl-CoA -> Acetoacetate + CoA
(a) –35.2 kJ/mol
(b) –32.7 kJ/mol
(c) +32.7 kJ/mol
(d) +35.2 kJ/mol
(e) none of the above
b
Which vitamin deficiency manifests itself as impaired wound healing, gastrointestinal bleeding and sore and bleeding oral tissues?
(a) Vitamin A
(b) Folate
(c) Vitamin C
(d) Vitamin D
(e) Vitamin B12
c
Question 22
https://canvas.qut.edu.au/courses/15061/pages/week-2-foundations-of-metabolism?module_item_id=1436926
a
Which of the following is (are) true regarding vitamins?
I. They are essential organic molecules an organism is unable to synthesize.
II. Some water soluble vitamins mediate electron-transfer reactions.
III. In humans, the water soluble vitamins converted into organic coenzymes.
IV. In humans, the fat soluble vitamins mediate group transfer reactions.
(a) I, II, III, IV
(b) I, II, III
(c) II, III, IV
(d) I only
(e) II, IV
b
Question 24
https://canvas.qut.edu.au/courses/15061/pages/week-2-foundations-of-metabolism?module_item_id=1436926
e
What is an oxidation? What is a reduction?
Can an oxidation occur without a simultaneous reduction? Why or why not?
Oxidation is the loss of electrons; reduction is the gain of electrons. Free electrons are unstable (do not occur), so whenever an electron is released by oxidation of some species, an electron must be accepted by reduction of another species.
Mnemonic: OIL RIG – oxidation electron loss, reduction electron gain
Explain the reasons why phosphorylation is an extremely effective tool for catalytic control
A phosphoryl group adds negative charges, allowing new electrostatic interactions and new hydrogen-bond formation. The free energy charge of phosphorylation is large, which can affect the conformational equilibrium of different states. Using ATP means that the reaction is linked to the energy status of the cell. Phosphorylation is rapid and reversible and can result in amplified effects. These factors affect structural, thermodynamic, regulatory, and kinetic properties.
What are the stages for extracting energy from food?
There are three stages.
(1) Large food molecules are broken down into smaller units, such as amino acids, carbohydrates, and fatty acids.
(2) The small units are further broken down to a subset of small molecules that are critical to metabolism, such as acetyl CoA.
(3) ATP is produced by oxidation of the acetyl units.
How are metabolic processes unified (for example, by using molecules that are common to multiple pathways) ?
How can you use this to help learn and understand metabolism?
Common molecules and mechanisms are evident in motifs and patterns throughout metabolic pathways. Understanding the logic of catabolic and anabolic pathways, and knowing common molecules (such as ATP, NAD+/NADH and acetyl CoA) and mechanisms (oxidation-reduction), makes it simpler to understand the myriad paths of metabolism.
What is an active (or activated) carrier?
List five active (or activated) carriers in metabolism and give the vitamins that are the precursors of these carriers.
Activated carriers are molecules that are used as carriers of a particular chemical group (group of atoms, electrons, or protons), often with “high energy” linkages between carriers and the groups.
One example would be ATP, which is the activated carrier of phosphoryl groups. Flavin derivatives (FAD) and nicotinamide derivatives (NAD+) are examples of activated carriers of
electrons.
Activated carrier:
NADH and NADPH
FADH2
Acetyl coenzyme A
Biotin
Tetrahydrofolate
Vitamin:
Niacin or Nicotinamide
Riboflavin
Pantothenate
Biotin
Folic acid
