Lecture 5 Energy and Enzymes

Question 1

Metabolism

Answer 1

total of all chemical reactions in the body

Question 2

Catabolic reactions

Answer 2

break down large molecules into smaller ones ex: glycogen -> glucose

Question 3

Anabolic reactions

Answer 3

Build up larger molecules from smaller ones amino acids -> proteins

Question 4

Exergonic reactions

Answer 4

release energy

Question 5

endergonic reactions

Answer 5

require energy

Question 6

Name the types of metabolic reactions

Answer 6

Hydrolysis & Dehydration Phophorylation & Dephosphorylation Oxidation-Reduction Reactions

Question 7

Hydrolysis

Answer 7

Add H20 to break bonds between monomer units

catabolic

A-B + H20 -> A-OH + H-B

e.g. surcose + H20 -> glucose + fructose

Question 8

Dehydration

Answer 8

Remove H20 to join monomers

anabolic

A-OH + H-B -> A-B +H20

e.g. peptide bond formation

Question 9

Phosphorylation

Answer 9

addition of a phosphate group (Pi)

C+Pi -> C-P+H20

e.g. ATP synthesis

Question 10

Transfer of phosphate from ATP

Answer 10

catalyzed by kinase enzyme

C+ATP -> C -P +ADP

Question 11

Dephosphorylation

Answer 11

removal of a phosphate group

C-P + H20 -> C + Pi

e.g. ATP hydrolysis

Question 12

Oxidation-Reducation (redox) Reactions

Answer 12

Electron transfer reactions: Oxidation is loss, Reduction is gain of electrons

major energy source of cells: Oxidation of sugars, fatty acids, and amino acids

Question 13

Redox reactions

Answer 13

are coupled: one molecule is oxidized another is reduced

in cells usually involve transfer of H atoms (not H+ ions)

e.g. reduction of pyruvate to lactate

Question 14

Coenzymes in redox reactions

role in cellular respiration

Answer 14

act as temporary carriers of H atoms and their electrons

NAD+ + 2 H (oxidized) -> NADH + H+(reduced)

FAD + 2H (oxidized) -> FADH2 (reduced)

oxygen is the final electron acceptor in cellular respiration 1/2 O2 + 2H -> H20

Question 15

Energy Metabolism

Answer 15

cells use chemical energy to do biological work: movement, synthesis, transport

energy is released in exergonic reactions that convert high-energy to lower-energy molecules

e.g. oxidation of glucose

Question 16

ATP energy currency of cells

role in energy metabolism

(production of ATP)

Answer 16

energy captured from oxidation of substrates is used to produce ATP

energy released from ATP hydrolysis powers energy-required processes

Question 17

Enzymes

Answer 17

are biochemical catalyst - speed up chemical reactions

most enzymes are proteins

increase reaction rate by lowering activation energy or providing an alternative chemical pathway for the reaction

Question 18

Name the 4 functional properites of enzymes

Answer 18

Substrate specificity

Sensitivity to temp and pH

Saturation kinetics

Regulation

Question 19

Substrate Specificity

Answer 19

substrate (reactant) binds reversibly to active site of the enzyme

specific fit between substrate and active site (shape and charge polarity)

induced fit: enzyme pulls on chemical bonds of substrates

Question 20

Sensitivity to temp and pH

Answer 20

effects on tertiary structure of proteins

Question 21

Saturation Kinetics

low and high [s] what happens

limited by?

Answer 21

reaction rate depends on substrate concentration (non-linear)

at low [s] reaction rate increases w/ increasin [s]

at high [s] reaction rate reaches maximum level

at the saturation point, all active sites are occupied

maximum rate is limited by number of available enzymes

Question 22

Regulation

Covalent Regulation

Involves?

Answer 22

regulation of enzyme via covalent binding of a chemical group

usually involves addition of phosphate group which activates the enzyme

E (inactive enzyme) + ATP -> E-P (acitve enzyme) + ADP

Question 23

Allosteric Regulation

Answer 23

regulation by non-covalent binding of a modulator to a regulatory site on the enzyme

can be either allosteric activation or allosteric inhibition

reaction rate depends on concentration of the modulator as well as substrate

Question 24

Feedback inhibition

Answer 24

product of a reaction pathway can act as a modulator which inhibits an enzyme in an earlier step (via allosteric inhibiton)

regulates formation of products

Question 25

Example of enzymes

Answer 25

Catalase

2 H202 -> 2 H20 + 02

Carbonic anhydrase

H20 + C02 -><- H2C03 -><- H+ + HCO3-

Hexokinase

glucose + ATP -> glucose-6-phosphate + ADP

Question 26

Clinical applications

Answer 26

abnormal enzyme levels may be associated with disease (e.g. liver enzyme tests)

Genetic deficiency in an enzyme -> inborn errors of metabolism (e.g. PKU)

Question 27

Kinase

Answer 27

protein kinase enzymes catalyze phosphorylation of other enzymes; important in cell signaling