Metabolism and enzymes

Question 1

Catabolism is the

Answer 1

Breaking down nutrients into smaller molecules to produce energy
Energy is stored in bonds of ATP molecule and transported where it is needed

Question 2

Anabolism is the

Answer 2

Stored energy is used to assemble new molecules from small components produced from catabolism

Question 3

Energy for metabolic reaction is

Answer 3

Energy is supplied to cells by breakdown of nutrients
Storage forms of energy: ATP, NADH, FADH2
Energy is released when molecular bonds are broken

Question 4

Stage one of catabolism occurs in

Answer 4

the gastrointestinal tract
Digestion in the lumen of the GI tract

Question 5

Stage 2 of catabolism occurs in

Answer 5

Anaerobic respiration in the cell’s cytosol

Question 6

Stage 3 of catabolism occurs in

Answer 6

Aerobic respiration in cell mitochondria

Question 7

Catabolism stage 1 is the

Answer 7

Occurs in GI tract
Food is broken down in stomach and digested stomach contents pass to small intestine
Further broken down by enzymes
Hydrolysis
Carbohydrates broken down to monosaccharides
Fats broken down to fatty acids and glycerol
Proteins broken down to amino acids
Nutrient molecules are absorbed by cells that line small intestine
Nutrients pass to blood or lymph
Carried to organs and tissues
Many go to liver for further metabolism

Question 8

Catabolic metabolism stage 2

Answer 8

Occurs in the cytosol
Process of anaerobic respiration catabolizes nutrients
Acetyl CoA is transported through cytoplasm to the mitochondria

Question 9

Catabolic metabolism stage 3

Answer 9

Occurs in the mitochondria
Aerobic respiration involves the attachment of an inorganic PO4 to a molecule of ADP to form ATP
ATP used by the cell to carry energy
Catabolic pathways of proteins, carbohydrates and fats transfer energy stored in nutrients into ATP

Question 10

Anabolic metabolism

Answer 10

A biosynthetic process

Question 11

Dehydration synthesis

Answer 11

Important part of anabolism
Effect is opposite of hydrolysis
Monosaccharides are assembled to form chains of polysaccharide
1 monosaccharide + 1 monosaccharide = 1 disaccharide + water
Fat molecules are formed from the connection of glycerol and fatty acids
Proteins are created from chains of amino acids

Question 12

Control of metabolic reactions

Answer 12

Metabolism is a multi-enzyme sequence of events
Reactions are highly specific
Cell relies on enzymes to initiate and control metabolism
Each enzyme reacts with one particular molecule (substrate) to produce a new molecule (product)
Product of one step is substrate of the next

Question 13

Enzyme activity

Answer 13

Depends on molecular shape of the enzyme
Active site = region of enzyme that binds to the substrate
Enzymes not altered by the reactions
Enzyme names end in -ase
Enzymes often named for substrate it acts upon
Transferases are enzymes that move of part of a molecule to another molecule

Question 14

Catalytic efficiency

Answer 14

Enzyme acts as catalyst
Speeds up reactions by lowering the activation energy
Increased rate of reaction is essential to life
Example: Carbon dioxide, a waste product of respiration, must be moved out of the body
To accomplish this carbonic anhydrase combines carbon dioxide with water to form carbonic acid (H2CO3) and bicarbonate ions (HCO3-)

Question 15

Control of metabolic reactions

Answer 15

May need assistance of a nonprotein cofactor in order to complete a reaction
Completes the shape of a binding site
Examples: iron, zinc, copper, copper, potassium, calcium ions

Question 16

Examples of coenzymes

Answer 16

nicotinamide adenine dinucleotide (NAD), acetyl-coenzyme A, flavin adenine dinucleotide (FAD)

Question 17

Factors effecting enzyme activity

Answer 17

Enzyme concentration
Effect on rate is directly proportional
Substrate concentration
Rate increases until enzyme is saturated
Temperature
Rate increases until denaturation of enzyme
pH
Many enzymes have maximum activity at pH near 7
Most enzymes are denatured at pH extremes
Pepsin is an exception – optimum pH is 1.5

Question 18

Enzyme inhibition

Answer 18

Enzyme inhibitor – any substance that can decrease the rate of an enzyme-catalyzed reaction
Many poisons and some medicines inhibit enzymes
Some inhibitors provide internal regulation of cellular metabolism

Question 19

Two categories of enzyme inhibition

Answer 19

Irreversible and reversible

Question 20

Irreversible inhibition

Answer 20

Irreversible inhibitor - forms a covalent bond with a functional group of the enzyme
Renders enzyme inactive
Many poisons are irreversible inhibitors

Question 21

Cyanide ion are what type of inhibition

Answer 21

Irreversible inhibition
Interferes with cytochrome oxidase
Blocks mitochondrial electron transport chain
Stops aerobic cellular respiration
Death occurs in minutes
Antidote – sodium thiosulfate
converts cyanide ion to thiocyanate that does not bind cytochrome oxidase

Question 22

Heavy metals are what type of inhibition

Answer 22

Irreversible inhibition
Combine with sulfhydryl groups on enzymes
Can cause neurological damage
Treated with chelating agents
Substance combines with metal and holds it very tightly

Question 23

Antibiotics are

Answer 23

Irreversible inhibition
Penicillin
Inhibit enzymes essential to life processes of bacteria
Penicillin interferes with transpeptidase which is needed for bacterial cell wall construction

Question 24

Reversible inhibition is and have 2 types

Answer 24

Reversible inhibitor reversibly binds to an enzyme so can be removed
Two types:
Competitive
Non competitive

Question 25

Competitive inhibition

Answer 25

Competes with substrate for binding at the active site of enzyme
Have molecular structure similar to normal substrate of enzyme
Example: sulfa drugs
Folic acid needed by bacteria is synthesized from p-aminobenzoic acid, which resembles sulfanilamide
Sulfanilamide competes for active site
Synthesis of folic acid slowed or stopped
Bacteria prevented from multiplying
Reversed by increasing concentration of normal substrate
Competition is won by whichever molecular species is in greater concentration

Question 26

Non competitive inhibitor is

Answer 26

Binds to enzyme at a location other than the active site
Bears no resemblance to normal enzyme substrate
Interaction causes 3-D shape of enzyme and active site to change
Enzyme no longer binds normal substrate or it binds improperly so reaction is not catalyzed
More substrate does not reverse inhibition

Question 27

Regulation of enzyme activity

Answer 27

Enzymes must be controlled - an organism must respond to changing conditions and cellular needs
Three control mechanisms:
Activation of zymogens
Allosteric regulation
Genetic control

Question 28

Activation of zymogens

Answer 28

Enzymes may be synthesized as inactive precursors called zymogens or proenzymes
Stored in inactive state
When needed zymogen is released and activated at location of reaction
Activation usually involves cleavage of peptide bonds of zymogen

Question 29

Allosteric regulation

Answer 29

Combination of enzyme with compound that change 3-D shape
Compound called a modulator
Allosteric enzymes are often located at key control points in cellular processes

Question 30

Allosteric regulation modulators

Answer 30

Activators – increase activity
Inhibitors – decrease activity

Question 31

Examples of allosteric regulation

Answer 31

Synthesis of isoleucine
Five steps
Product isoleucine binds to enzyme at first step and inhibits enzyme activity
No excess isoleucine is produced
When isoleucine level lowers, the enzyme will be more active and more isoleucine is synthesized
Feedback inhibition – a process in which the end product of a pathway inhibits an earlier step in the process

Question 32

Genetic control

Answer 32

Enzyme induction – synthesis of an enzyme in response to cellular need
Allows an organism to adapt to environmental changes
Example: regulation of gluconeogenesis
Activity of PEP carboxykinase is increased during fasting, starvation and diabetes mellitus due to enzyme induction by glucagon

Question 33

enzymes in clinical diagnosis

Answer 33

Certain enzymes are normally found only inside cells
Get released into blood and fluid when cells are damaged
Changes in blood serum levels of specific enzymes can be used to clinically detect cell damage or uncontrolled growth
Measurements of enzyme concentrations is a major diagnostic tool

Question 34

Alkaline phosphate indicates what in a clinical diagnosis

Answer 34

– liver or bone disease

Question 35

Isozymes are

Answer 35

A slightly different form of the same enzyme produced by different tissues
Have similar catalytic properties but different physical properties
Assays for isozymes can pinpoint location and type of disease more accurately

Question 36

Co enzymes

Answer 36

Nonprotein organic molecules that may also act as cofactors
Often vitamins, or derived from vitamins
May be bound temporarily or permanently to the enzyme

Question 37

Amylase indicates what in a clinical diagnosis

Answer 37

Pancreatic disease

Question 38

Lipase indicates what in a clinical diagnosis

Answer 38

acute pancreatitis

Question 39

Alanine transaminase indicates what in clinical diagnosis

Answer 39

hepatitis

Question 40

Aspartate transaminase indicates what in a clinical diagnosis

Answer 40

hepatitis or heart attack

Question 41

Growing cells need additional protein through anabolic metabolism because

Answer 41

Growing cells need additional proteins:
For the expanded cell membranes
To perform many other vital functions
Replacement molecules must be manufactured continuously
Metabolic turnover