Topic 2.2

Question 1

Which of the following is incorrect regarding nucleotides?
a) They contain sugar, a nitrogen-containing base, and a phosphate functional group
b) They are the monomers f fats a polysaccharides
c) They join together by alternating covalent bonds between the sugars and phosphate groups
d) They are present in both DNA and RNA

Answer 1

b) They are the monomers f fats a polysaccharides

Question 2

Which of the following is correct regarding ATP?
a) It is an amino acid
b) It has a heliccal structure
c) It is a high- energy molecule that can break down to ADP and phosphate
d) It is a nucleotide component o DNA and RNA

Answer 2

c) It is a high- energy molecule that can break down to ADP and phosphate

Question 3

Summarize why enzymes are needed in biochemical pathways and how cells may regulate their activity

Answer 3

*Enzymes are needed to reduce the activation energy of the reactions present in a biochemical reaction, this allowing reactions to occur under conditions of the cell.
*A cell can convert an enzyme from an inactive form to an active one by the addition or removal of phosphate groups or by cleaving off parts of the protein
*Cellular enzymes are subject to feedback inhibition.
*The presence of cofactors and coenzymes in the cell regulates enzyme activity

Question 4

Describe how enzymes accelerate chemical reactions

Answer 4

Enzymes lower the activation of a reaction, allowing it to occur with lower inputs of energy

Question 5

Discuss why the three-dimensional shape of an enzyme is important to its function

Answer 5

How well the enzyme interacts with the reactants and the rate at which product is formed is determined by the three- dimensional shape of the protein molecule and its active site

Question 6

Define metabolic pathway

Answer 6

Series of linked reactions, beginning with a particular reactant and terminating with an end product.

Question 7

Define enzyme

Answer 7

Organic catalyst, usually a protein, that speeds a reaction in cells due to its particular shape.

Question 8

Define ribozomes

Answer 8

RNA molecule that functions as an enzyme that can catalyze chemical reactions.

Question 9

Define energy of activation (Ea)

Answer 9

Energy that must be added in order for molecules to react with one another.

Question 10

Define active site

Answer 10

Region of an enzyme where the substrate binds and where the chemical reaction occurs.

Question 11

Define induced fit model

Answer 11

Change in the shape of an enzyme’s active site that enhances the fit between the active site and its substrate(s).

Question 12

Define denatured

Answer 12

Loss of a protein’s or enzyme’s normal shape so that it no longer functions; usually caused by a less than optimal pH and temperature.

Question 13

Define enzyme inhibition

Answer 13

Means by which cells regulate enzyme activity; may be competitive or noncompetitive inhibition.

Question 14

Define cofactor

Answer 14

Nonprotein assistant required by an enzyme in order to function. Many cofactors are metal ions; others are coenzymes.

Question 15

Define coenzymes

Answer 15

Nonprotein organic molecule that aids the action of the enzyme to which it is loosely bound.

Question 16

Define vitamin

Answer 16

Organic nutrient that is required in small amounts for metabolic functions. Vitamins are often part of coenzymes.

Question 17

Which of the following is incorrect regarding the active site of an enzyme?
a) is unique to that enzyme
b) is the part of the enzyme where its substrate fits in
c) can be used over and over again
d) is not affected by environmental factors, such as pH and temperature

Answer 17

d) is not affected by environmental factors, such as pH and temperature

Question 18

Which of the following environmental conditions may have an influence on enzyme activity?
a) substrate concentration
b) temperature
c) pH
d) all of the above

Answer 18

d) all of the above

Question 19

In which of the following does an inhibitor bind to a site other than the active site of an enzyme?
a) competitive inhibition
b) noncompetitive inhibition
c) redox reactions
d) none of the above

Answer 19

d) none of the above

Question 20

Enzymes catalyze chemical reactions by which of the following?
a) lowering the energy of activation in the reaction
b) raising the energy of activation in the reaction
c) increasing entropy
d) increasing the free energy of the products

Answer 20

b) raising the energy of activation in the reaction

Question 20

Enzymes catalyze chemical reactions by which of the following?
a) lowering the energy of activation in the reaction
b) raising the energy of activation in the reaction
c) increasing entropy
d) increasing the free energy of the products

Answer 20

a) lowering the energy of activation in the reaction

Question 21

Explain the role of NAD+ and FAD in cellular respiration

Answer 21

NAD+ and FAD serve as coenzymes for the enzymes involved in cellular respiration. Both molecules receive electrons and become reduced (NADH and FADH2) and transport the electrons to inside the mitochondria, where they function in the electron transport chain.

Question 22

Distinguish between the aerobic and anaerobic phases of cellular respiration

Answer 22

Glycolysis is an anaerobic process. The preparatory reaction, citric acid cycle (KREBS cycle), and electron transport chain are all aerobic and therefore dependent on the presence of oxygen.

Question 23

Summarize the location and function of each phase of cellular respiration

Answer 23

The complete breakdown of glucose during cellular respiration consists of four phases:
1. Glycolysis in the cytoplasm produces pyruvate, which enters mitochondria if oxygen is available.
2. The preparatory reaction and the citric acid cycle that follow occur inside the mitochondria.
3. Inside the mitochondria, the electron transport chain receives the electrons removed from glucose breakdown products.
4. The result of glucose breakdown is a maximum of 36 to 38 ATP, depending on the particular cell.

Glycolysis~>Preparatory reaction/Krebs cycle~>Electrons received in electron transport chain~>Glucose breakdown= 36 to 38 ATP

Question 24

Define cellular respiration

Answer 24

Metabolic reactions that use the energy from carbohydrate, fatty acid, or amino acid breakdown to produce ATP molecules.

Question 25

Define NAD+ (Nicotinamide adenine dinucleotide)

Answer 25

Coenzyme in oxidation-reduction reactions that accepts electrons and hydrogen ions to become NADH + H+ as oxidation of substrates occurs. During cellular respiration, NADH carries electrons to the electron transport chain in mitochondria.

Question 26

Define FAD (flavin adenine dinucleotide)

Answer 26

A coenzyme of oxidation-reduction that becomes FADH2 as oxidation of substrates occurs in the mitochondria during cellular respiration, FAD then delivers electrons to the electron transport chain.

Question 27

Define anaerobic

Answer 27

A chemical reaction that occurs in the absence of oxygen; an example is the fermentation reactions.

Question 28

Define aerobic

Answer 28

A chemical process that requires air (oxygen); phase of cellular respiration that requires oxygen.

Question 29

During glycolysis, what is the net production of ATP per glucose molecule?
a) 0
b) 1
c) 2
d) 8
e) 32-34

Answer 29

c) 2

Question 30

Which of the following is not a product or reactant of glycolysis
a) NADH
b) ATP
c) pyruvate
d) oxygen

Answer 30

d) oxygen

Question 31

Which of these is incorrect regarding fermentation?
a) There is a net gain of only two ATP per glucose
b) It occurs in the cytoplasm
c) The process starts with glucose entering glycolysis
d) NADH donates electrons to the electron transport chain
e) it’s anaerobic

Answer 31

d) NADH donates electrons to the electron transport chain

Question 31

Fermentation is primarily involved in the recycling of
a) ADP
b) oxygen
c) pyruvate
d) NAD+

Answer 31

d) NAD+

Question 32

The greatest contributor of electrons to the electron transport chain is
a) oxygen
b) the prep reaction
c) glycolysis
d) fermentation
e) the citric acid cycle

Answer 32

e) the citric acid cycle

Question 33

Which of these is not true of the citric acid cycle?
a) the citric acid cycle include the prep reaction
b) the citric acid cycle produces ATP by substrate-level ATP synthesis
c) the citric acid cycle occurs in the mitochondria
d) the citric acid cycle produces two ATP per glucose molecule

Answer 33

a) the citric acid cycle include the prep reaction

Question 34

Which of these is not true of the electron transport chain?
a) the electron transport chain is located on the cristae of the mitochondria
b) the electron transport chain produces more NADH than any metabolic pathway
c) the electron transport chain contains cytochrome molecules
d) the electron transport chain ends when oxygen accepts electrons

Answer 34

b) the electron transport chain produces more NADH than any metabolic pathway

Question 35

The oxygen required by cellular respiration is reduced and becomes part of which molecule?
a) ATP
b) pyruvate
c) H2O
d) CO2

Answer 35

c) H2O