 |
| 1 | |
The first enzymes ever known, from which the word enzyme was derived, were |
| | A) | enzymes of saliva that break down starch |
| | B) | enzymes of yeast that ferment glucose |
| | C) | enzymes of the stomach that digest protein |
| | D) | isomerases which rearrange molecule into different isomers |
|
|
|
| 2 | |
RNA molecules called ribozymes have some specialized enzyme activity, but otherwise as a general rule, all enzymes are |
| | A) | inorganic catalysts |
| | B) | complex carbohydrate molecules |
| | C) | phospholipids and glycolipids |
| | D) | proteins |
|
|
|
| 3 | |
An enzyme has all of the following properties except |
| | A) | it increases the rate of a chemical reaction. |
| | B) | it is not permanently changed by the reaction it catalyzes. |
| | C) | it increases the energy yield from a chemical reaction. |
| | D) | it does not change what the products of a chemical reaction will be. |
|
|
|
| 4 | |
We use a match to light a fireplace, but we get much more heat back from the firewood than the amount put into it by the match. The energy of the match represents the |
| | A) | entropy needed to start the fire |
| | B) | activation energy of a chemical reaction |
| | C) | oxidizing agent that makes the wood burn |
| | D) | free energy of the system |
|
|
|
| 5 | |
An enzyme or any other catalyst essentially works by |
| | A) | making a reaction more endergonic |
| | B) | making a reaction more exergonic |
| | C) | lowering the activation energy of a reaction |
| | D) | increasing the net energy yield form a reaction |
|
|
|
| 6 | |
The three-dimensional shape of an enzyme molecule is critically important to its ability to catalyze chemical reactions. This characteristic three-dimensional shape is called its |
| | A) | primary structure. |
| | B) | conformation. |
| | C) | substrate. |
| | D) | confirmation. |
|
|
|
| 7 | |
Carbonic anhydrase breaks down carbonic acid into water and carbon dioxide gas. The specific area of the enzyme where carbonic acid attaches is known as the |
| | A) | active site. |
| | B) | conformation. |
| | C) | substrate. |
| | D) | product. |
|
|
|
| 8 | |
Carbonic anhydrase breaks down carbonic acid into water and carbon dioxide gas. Carbonic acid would be considered the |
| | A) | substrate. |
| | B) | product. |
| | C) | enzyme. |
| | D) | by-product. |
|
|
|
| 9 | |
When carbonic anhydrase and carbonic acid are temporarily joined together, they form |
| | A) | an allosteric complex. |
| | B) | a reactant-product complex. |
| | C) | an isoenzyme. |
| | D) | an enzyme-substrate complex. |
|
|
|
| 10 | |
The "lock-and-key model" of enzyme function describes the |
| | A) | complementarity of isoenzymes to each other. |
| | B) | mechanism of allosteric inhibition. |
| | C) | interaction between enzymes and their coenzymes. |
| | D) | specific fit of a substrate to its particular enzyme. |
|
|
|
| 11 | |
Which of the following is not a category of enzymes? |
| | A) | Phosphatases |
| | B) | Dehydrogenases |
| | C) | Autolases |
| | D) | Synthetases |
|
|
|
| 12 | |
Slightly different variations of an enzyme that perform the same job, but are found in different cells or tissues, are called |
| | A) | isoenzymes. |
| | B) | isomers. |
| | C) | isomerases. |
| | D) | allosteric variants. |
|
|
|
| 13 | |
The rate of an enzymatic reaction can be affected by all of the following except |
| | A) | temperature. |
| | B) | pH. |
| | C) | osmotic pressure. |
| | D) | enzyme concentration. |
|
|
|
| 14 | |
The rate of an enzymatic reaction increases as the temperature rises, up to a point. Above 40°C or so, however, the reaction rate begins to decline because the |
| | A) | enzyme changes shape at higher temperatures. |
| | B) | substrate changes shape at higher temperatures. |
| | C) | enzyme gets used up faster at temperature above 40°C. |
| | D) | substrate gets used up faster at temperatures above 40°C. |
|
|
|
| 15 | |
Which of the following is a coenzyme? |
| | A) | FAD |
| | B) | Amylase |
| | C) | Ca2+ |
| | D) | Mg2+ |
|
|
|
| 16 | |
Substrate concentration increases the rate of an enzymatic reaction up to a certain point, but then has no further effect and the reaction rate levels off. This is because |
| | A) | excess product is not released from the active site. |
| | B) | accumulation of end product shuts down the reaction |
| | C) | excess substrate makes the enzymes change conformation |
| | D) | all the active sites are saturated with substrate molecules |
|
|
|
| 17 | |
The reaction H2O + CO2 ↔ H2CO3 will proceed to the right if there is excess water and carbon dioxide available, or to the left if there is excess carbonic acid available, because of |
| | A) | end-product inhibition. |
| | B) | allosteric inhibition. |
| | C) | the first law of thermodynamics. |
| | D) | the law of mass action. |
|
|
|
| 18 | |
A metabolic pathway differs from a simple enzymatic reaction in that it has |
| | A) | reversible reactions. |
| | B) | several intermediates and enzymes. |
| | C) | branch points. |
| | D) | allosteric inhibitors. |
|
|
|
| 19 | |
A branched metabolic pathway can be switched from the production of one final product to production of a different final product by |
| | A) | changing the substrates. |
| | B) | activating an isoenzyme. |
| | C) | end-product inhibition. |
| | D) | switching from endergonic to exergonic. |
|
|
|
| 20 | |
In allosteric inhibition, the final end product of a metabolic pathway |
| | A) | cannot be produced. |
| | B) | binds to the active site of an enzyme earlier in the pathway and blocks its reaction with the substrate. |
| | C) | binds to some other site on an earlier enzyme in the pathway and changes the enzyme's conformation. |
| | D) | gets used up as fast as it is produced. |
|
|
|
| 21 | |
Phenylketonuria (PKU) occurs when there is |
| | A) | not enough phenylalanine in the diet |
| | B) | not enough tyrosine in the diet |
| | C) | a hereditary defect in an enzyme |
| | D) | a failure of end-product inhibition to occur |
|
|
|
| 22 | |
All of the following are inborn error of metabolisms except |
| | A) | Tay-Sachs disease. |
| | B) | benign prostatic hypertrophy. |
| | C) | albinism. |
| | D) | lactose intolerance. |
|
|
|
| 23 | |
In inborn errors of metabolism |
| | A) | the end-product of a metabolic pathway accumulates. |
| | B) | the body is unable to produce any of the enzymes needed for a specific metabolic pathway. |
| | C) | the individual acquires this disorder during his/her lifetime. |
| | D) | intermediates in a specific metabolic pathway accumulate and the final product is not made. |
|
|
|
| 24 | |
The flow of energy through living systems is known as |
| | A) | thermodynamics. |
| | B) | ergonomics. |
| | C) | bioenergetics. |
| | D) | biofeedback. |
|
|
|
| 25 | |
According to the ____, energy can be converted from one form to another, for example from solar energy to chemical bond energy, but it is neither created nor destroyed in these transformations. |
| | A) | first law of thermodynamics |
| | B) | second law of thermodynamics |
| | C) | law of free energy |
| | D) | law of entropy |
|
|
|
| 26 | |
According to the ____, whenever energy is transferred from one molecule to another, some of it is lost and is no longer available to do useful work (no longer present in an organized state). |
| | A) | first law of thermodynamics |
| | B) | second law of thermodynamics |
| | C) | principles of oxidation and reduction |
| | D) | law of conservation of energy |
|
|
|
| 27 | |
If the products of a chemical reaction contain more total energy than the reactants, the reaction must be |
| | A) | imaginary, because this could never happen according to the second law of thermodynamics. |
| | B) | endergonic. |
| | C) | exergonic. |
| | D) | an oxidation reaction. |
|
|
|
| 28 | |
An exergonic reaction is one in which |
| | A) | electrons are added to a molecule. |
| | B) | electrons are removed from a molecule. |
| | C) | the products have more free energy than the reactants. |
| | D) | the reactants have more free energy than the products. |
|
|
|
| 29 | |
The calorie is fundamentally a unit used to measure |
| | A) | the energy content of a substance. |
| | B) | the amount of energy given off by a chemical reaction. |
| | C) | heat. |
| | D) | nutritional content of a substance. |
|
|
|
| 30 | |
Your textbook symbolizes exergonic and endergonic reactions as two meshed gears with exergonic reactions driving endergonic reactions. The fundamental reason that the exergonic gear is shown larger than the endergonic one is that |
| | A) | all energy transfers lose some free energy as useless heat. |
| | B) | exergonic reactions are more powerful than endergonic ones. |
| | C) | usually, many different endergonic reactions are driven by one exergonic reaction. |
|
|
|
| 31 | |
The main endergonic reaction that is driven by most of the body's exergonic reactions is the |
| | A) | oxidation of FADH2. |
| | B) | synthesis of ATP. |
| | C) | reduction of NAD. |
| | D) | hydrolysis of ATP. |
|
|
|
| 32 | |
Within mammalian cells, the "universal energy carrier" is |
| | A) | FAD. |
| | B) | FADH2. |
| | C) | glucose. |
| | D) | adenosine triphosphate. |
|
|
|
| 33 | |
An atom or molecule has been oxidized when |
| | A) | it has been broken down into smaller or simpler substances. |
| | B) | its free energy content has decreased. |
| | C) | electrons have been donated to it. |
| | D) | it has lost some of its electrons. |
|
|
|
| 34 | |
If molecule A accepts electrons from molecule B, molecule A is said to be |
| | A) | reduced. |
| | B) | a reducing agent. |
| | C) | an oxidizing agent. |
| | D) | an exergonic agent. |
|
|
|
| 35 | |
Any oxidation reaction must be coupled to |
| | A) | the synthesis of ATP. |
| | B) | the availability of oxygen. |
| | C) | an exergonic reaction. |
| | D) | a reduction reaction. |
|
|
|
| 36 | |
If a molecule accepts a hydrogen atom, it becomes |
| | A) | hydrolyzed. |
| | B) | dehydrated. |
| | C) | oxidized. |
| | D) | reduced. |
|
|
|
| 37 | |
Nicotinamide adenine dinucleotide (NAD) is |
| | A) | a vitamin. |
| | B) | an oxidizing agent. |
| | C) | a reducing agent. |
| | D) | a coenzyme. |
|
|
|
| 38 | |
Which of the following represents the reduced form of a coenzyme? |
| | A) | FADH2. |
| | B) | FAD. |
| | C) | NAD. |
| | D) | ADP. |
|
|
|
| 39 | |
The reduced form of flavin adenine dinucleotide is FADH2, while the reduced form of nicotinamide adenine dinucleotide is NADH. The reason the latter is written NADH and not NADH2 is that |
| | A) | NADH is less oxidized than FADH2. |
| | B) | NADH is more oxidized than FADH2. |
| | C) | NAD can only accept one electron. |
| | D) | NAD can only accept one proton. |
|
|
.