- branched and interconnected (networked) - Networking is arbitrary and driven by chemical logic - Catabolic reactions generate energy and anabolic reactions use energy

Metabolism (General) Flashcards by Alshayma Althani

Active holoenzymes are formed from
____________ in the presence of
_________.
a. Cofactors; proteins
b. Proteins; cofactors
c. Apoenzymes; cofactors
d. Apoenzymes; proteins
e. Apoenzymes; inactive holoenzymes

c. Apoenzymes; cofactors

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Define Metabolism

the entire network of chemical reactions carried out by living cells

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Define Metabolites

small molecule intermediates in the degradation and synthesis of polymers

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Catabolic reactions

Degrade molecules to create smaller molecules and energy

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Anabolic reactions

synthesize molecules for cell maintenance, growth and reproduction

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Metabolic Pathways

branched and interconnected (networked)
Networking is arbitrary and driven by chemical logic
Catabolic reactions generate energy and anabolic reactions use energy

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Cell Organelles and Metabolic Functions:

1- Mitochondria
2-Cytosol
3- Lysosomes
4- Golgi Complex
5- Endoplasmic reticulum
6- Peroxisomes (plants)

1- Mitochondrion: TCA cycle, Oxidative Phosphorylation, fatty acid oxidation, Amino acid breakdown

2- Cytosol: Glycolysis, Fatty acid biosynthesis, gluconeogenesis

3- Lysosomes: Degradation of cell components
Nucleus-DNA replication, Transcription, RNA processing

4- Golgi Complex: Synthesis of membrane components

5- Endoplasmic reticulum: Synthesis of proteins

6- Peroxisomes (plants): Oxidative reactions in plants

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The metabolism of the four major groups of biomolecules will be considered:

Carbohydrates
Lipids
Amino Acids
Nucleotides

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Flux

flow of material through a metabolic pathway which depends upon:
(1) Supply of substrates (2) Removal of products (3) Pathway enzyme activities

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Feed-back inhibition:

Product of a pathway controls the rate of its own synthesis by inhibiting an early step (usually the first “committed” step (unique to the pathway)

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Feed-forward activation:

Metabolite early in the pathway activates an enzyme further down the pathway

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Interconvertible enzyme activity can be rapidly and reversibly altered by..

covalent modification

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Three types of compounds are produced that mediate the release of energy

(1) Acetyl CoA
(2) Nucleoside triphosphates (e.g. ATP)
(3) Reduced coenzymes (NADH, FADH2, QH2)

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Oxidative phosphorylation

is the process by which the potential is coupled to the reaction: ADP + Pi —> ATP

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ΔG=ΔH–TΔS

Gibbs free energy

Cells must work within the laws of thermodynamics

There are three cases
∆G < 0: the reaction proceeds as written
∆G = 0: the reaction is at equilibrium
∆G > 0: the reaction runs in reverse

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ΔG=ΔH–TΔS

Gibbs free energy

Cells must work within the laws of thermodynamics

There are three cases
∆G < 0: the reaction proceeds as written
∆G = 0: the reaction is at equilibrium
∆G > 0: the reaction runs in reverse

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Has 3 phosphoryl groups
Hydrolysis releases large amount energy
Energy release is accompanied by transfer of phosphoryl group to another compound
Hence, biologically important molecule

ATP-A High Energy Intermediate

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Formation of glucose 6-phosphate from glucose is an example of ——– reaction

Coupled Reactions

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Formation of ATP from ADP is an example of ——– reaction

Coupled Reactions

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Metabolic Pathways that occurs in Cytosol

Glycolysis

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Metabolic Pathways that occurs in Mitochondria

Oxidative Phosphorylation

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Operation of different metabolic pathways at different compartments occurs in ———— cells

Eukaryotic cells

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All of the reactions take place in the same compartment but localized to different areas

prokaryotic cells

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Compartmentalization of metabolic processes permits:

separate pools of metabolites within a cell
simultaneous operation of opposing metabolic paths
high local concentrations of metabolites
coordinated regulation of enzymes

Example: fatty acid synthesis enzymes (cytosol), fatty acid breakdown enzymes (mitochondria)

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Compartmentalization of metabolic processes permits:

- separate pools of metabolites within a cell - simultaneous operation of opposing metabolic paths - high local concentrations of metabolites - coordinated regulation of enzymes Example: fatty acid synthesis enzymes (cytosol), fatty acid breakdown enzymes (mitochondria)

Compartmentalization is -------------specific

tissue and organ

Gluconeogenesis and detoxification occurs in which organ?

Liver

Storage of triglycerides occurs in which tissue?

Adipose tissue

LDH Type M present in...

skeletal muscle and liver -Pyruvate to Lactate

LDH Type H present in...

heart muscle -Lactate to Pyruvate

Organisms extract energy from -------- to drive energy-consuming reactions

external sources

T or F Cells are not static

T cell components are continually synthesized and degraded (i.e. undergo turnover)

Organisms or cells maintain specific internal concentrations of...

inorganic ions, metabolites and enzymes

Three Metabolic Pathways and they are......

(a) Linear (b) Cyclic (c) Spiral pathway

------------------------ permit control of energy input and output

Multiple-step pathways

Catabolic multi-step pathways provide energy in ------------------

smaller stepwise amounts

---------- occur in multi-step pathways

Control points

Metabolism is ----------- to permit organisms to respond to changing conditions

highly regulated

Most Metabolic pathways are....

irreversible

Metabolic fuels:

(1) Carbohydrates: provide energy (2) Proteins: provide amino acids for protein synthesis and some energy (3) Fats: triacylglycerols provide energy and also lipids for membrane synthesis

Active holoenzymes are formed from ____________ in the presence of _________. a. Cofactors; proteins b. Proteins; cofactors c. Apoenzymes; cofactors d. Apoenzymes; proteins e. Apoenzymes; inactive holoenzymes

c. Apoenzymes; cofactors

Because coenzymes are specific for the chemical groups that they accept and donate, they are referred to as a. Cofactors b. Reactive centers c. Activator ions d. Group-transfer reagents e. All of the above

d. Group-transfer reagents

Ca2+ or Mg2+ are most likely to be part of ___________, while Zn2+ or Fe2+ are present in _______________. a. Metal-activated enzymes; metalloenzymes b. Metalloenzymes; metal-activated enzymes c. Cofactors; coenzymes d. Coenzymes; cofactors e. Apoenzymes; holoenzymes

a. Metal-activated enzymes; metalloenzymes

Coenzymes which must return to their original form after each catalysis are called a. Prosthetic groups b. Cosubstrates c. Metabolite coenzymes d. Vitamin coenzymes e. All of the above

e. All of the above

Intermediary metabolism is the term applied to reactions that _______________. a. degrade molecules b. synthesize large molecules such as proteins c. convert glucose to pyruvate d. involve low molecular weight metabolites

d. involve low molecular weight metabolites

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.

b. They have a net consumption of ATP.

A distinct set of metabolic reactions is called a reaction ________________. a. microcosums b. cycle c. pathway d. mechanism

c. pathway

Consider the synthesis of a biopolymer in which the addition of successive monomers occurs by the same kind of reaction(s). The synthesis of the polymer is a ________ pathway. a. linear b. cyclic c. spiral d. branched

c. spiral

Which statement is false about most metabolic pathways? a. Most pathways are reversible under physiological conditions. b. Pathways serve to increase the efficiency of energy transfers. c. The rates of pathway reactions vary to respond to changing conditions. d. The enzymes that catalyze reactions in metabolic pathways generally catalyze only a single step.

a. Most pathways are reversible under physiological conditions.

The flow of material through a metabolic pathway is called the ________. a. current b. degree of amplification c. cascade effect d. flux

d. flux

The flow of material through a reaction pathway usually depends on ________________. a. control at several steps in the pathway b. control of the first step of the pathway c. covalent modification of the enzyme that catalyzes the reaction d. feed-forward activation

a. control at several steps in the pathway

For a step in a reaction pathway to serve as a control point it should be ____________. a. irreversible b. endergonic c. far from equilibrium d. both a and c e. all of the above

d. both a and c

Ten people are sitting in a row. Their objective is to whisper a secret from one person to the next all the way down the row. The first person whispers the secret to the second person who passes the secret to the third person and so on. After whispering to the third person, the second person in the row notices the ninth person has fallen asleep in their chair, so she gets up, goes down the row and shakes person nine awake. This example is similar to ________. a. allosteric control b. positive cooperativity c. feed-forward activation d. negative modulation

c. feed-forward activation

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. all of the above are usually equally as fast

c. changing the enzyme concentration

The ultimate product of complete oxidation of carbohydrates is __________. a. carbon dioxide b. acetyl CoA c. pyruvate d. acetate ion

a. carbon dioxide

Which distinguishes a steady state from an equilibrium? a. In a steady-state the concentrations of intermediates vary; in an equilibrium they do not. b. A steady-state requires constant removal of product and replenishment of reactant; an equilibrium does not. c. Steady-state and equilibrium are not distinguishable. They are two terms for the same thing. d. Steady-states apply only to irreversible reactions. Equilibrium reactions must be reversible.

b. A steady-state requires constant removal of product and replenishment of reactant; an equilibrium does not.

Calculate Delta G 0' for the reaction shown if the mass action ratio, Q, is 5.3 x 102 M -1 and Delta G is 46 kJ/mol at a temperature of 298 K. (R = 8.315 J/K-mol) ADP + Pi --> ATP a. 30 kJ/mol b. -30 kJ/mol c. 61 kJ/mol d. -61 kJ/mol

a. 30 kJ/mol

A reaction that best serves as a control point for regulation _______________. a. is a near equilibrium reaction b. has a large positive Delta G c. is metabolically irreversible d. follows Michaelis-Menton kinetics

c. is metabolically irreversible

The amount of energy recovered as ATP can be estimated by measuring free energy of hydrolysis of a. Phosphoester I bond in ATP b. Phosphoanhydride bonds in ADP c. Phosphoester bond I ADP d. Phosphoanhydride bonds in ATP e. All of the above

d. Phosphoanhydride bonds in ATP

ATP is the most commonly used source of energy rich compounds in cells because a. It complexes with Mg2+ b. It has a higher free energy of hydrolysis c. Its products of hydrolysis are more stable the ATP d. It is used more often than other nucleoside triphoshates e. It engages in phosphoryl-group transfers

d. It is used more often than other nucleoside triphoshates

Which of the following is not a factor contributing to the large free energy of hydrolysis of ATP? a. Electrostatic repulsion of oxygen atoms b. Better solvation of products than ATP itself c. Complexes with Mg2+ or Mn2+ ions d. Better stability of products than ATP itself e. Electrical sheilding of products of hydrolysis

c. Complexes with Mg2+ or Mn2+ ions

ATP can be used to activate a substrate by a. Phosphorylation b. Adding a nucleotidyl group c. Producing inorganic phosphate d. Both a and b e. a, b, and c

d. Both a and b

A compound with a greater free energy of hydrolysis than ATP is a. Glucose 1-phosphate b. Any phosphoester c. Phosphoenolpyruvate d. Acetyl CoA e. All of the above

c. Phosphoenolpyruvate

ATP is thermodynamically suited as a carrier of phosphoryl groups in animal cells because a. It is stable under cell conditions b. It is not hydrolyzed in cells without enzyme action c. It is intermediate in grouptransfer potential d. It can be produced from phosphocreatine e. All of the above

e. All of the above

The formation of acetyl CoA is brought to completion because a. The standard free energy for the first reaction is negative b. The standard free energy for the final reaction is negative c. The product pyrophosphate is readily removed by pyrophosphatase d. The formation of an ADP intermediate is negative e. All of the above

c. The product pyrophosphate is readily removed by pyrophosphatase

The chemical energy generated by oxidations cannot be captured by a. NADH b. NADP c. FMN d. FAD e. Q

a. NADH

When a reduction half-reaction is __________ (negative, positive), electrons flow to the more readily reduced substance which is __________ (negative, positive) in value. a. Negative; negative b. Negative; positive c. Positive; positive d. Positive; negative

b. Negative; positive

The biochemical reactions that degrade molecules, such as nutrients, are called anabolic reactions. a. True b. False

b. False

A given cell type tends to maintain relatively constant internal concentrations of inorganic ions, enzymes and metabolites. a. True b. False

a. True

Metabolic pathways generally have easily distinguished starting and stopping points. a. True b. False

b. False

Most metabolic reactions occur continuously at a fixed rate. a. True b. False

b. False

Phosphatases catalyze the hydrolytic removal of phosphate groups. a. True b. False

a. True

Metal-activated enzymes may require a metal ion or simply be stimulated in the presence of the ion. a. True b. False

a. True

Vitamin deficiency diseases are a result of the lack of formation of certain coenzymes. a. True b. False

a. True

Phosphorylation of enzymes involved in catabolic pathways usually activates them. a. True b. False

a. True

All enzymes require metallic cations to achieve full catalytic activity. a. True b. False

b. False

All metabolic reactions occur in the cytosol of cells. a. True b. False

b. False

Reactions of most metabolic pathways are in a state of equilibrium and have a Delta G equal to zero. a. True b. False

b. False

Protein catalysts rely exclusively on the amino acid residues for reactivity at the sites of action. a. True b. False

b. False

Organic compounds are coenzymes and cofactors while inorganic ions are cofactors only. a. True b. False

b. False