chapter 13 Flashcards
How do enzymes differ from ordinary catalysts?
1) Higher reaction rates
2) Milder reaction conditions
3) Greater reaction conditions
4) Capacity for control
How are the reaction rates of enzymes different from uncatalyzed reactions and ordinary catalyzed reactions?
enzyme catalyst are typically 10^6 to 10^12 greaterthan uncatalyzed reactions and at least several orders greater than chemically catalyzed reactions
How do the conditions of enzyme catalyst and chemical catalyse differ?
Enzymatically catalyzed reactions occur under realitively milder conditions: temperature below 100 degrees C, atmospheric pressure and nearly neutral pH’s. In contrast, chemical catalysis often require elevated temperatures and pressures as well as extremes of pH.
How does reaction specificity differ between enzyme catalyze reactions and chemical catalyze?
Greater specificity of enzyme catalyze reactions with respect to the identities of both substrates (reactants) and their products than chemical catalyst. That is enzymatic reactions rarley have side products
Why does the catalytic activities of many enzymes vary?
varies in response to concentration of substances other than their substrate and products.
What are the mechanisms that control the capacity of enzymes?
allosteric control
covalent modification of enzymes
and variation in amount of enzymes synthesized
enzymology
study of enzymes
diastase contains _____ and catalyzes what?
alpha amylase and catalyzes the hydrolysis of starch more efficiently sulfuric acid.
Lock and key hypothesis
The specificity of an enzyme (the lock) for its substrate (the key) arises from their geometrically complementary shapes.
what was the first enzyme catalyzed? which does what
Jack bean urease which catalyzes the hydrolysis of urea to NH3 and CO2
Enzymes are what types of molecule?
proteins
The noncovalent forces through which substrates and other molecules bind to enzymes are similar in character to what?
the forces that dictate the conformations of the proteins themselves: both involve van der Waals, electrostatic, hydrogen bonding and hydrophobic interaction.
In general a substrate binding site consists of what?
an indention or cleft on the surface of an enzyme molecule that is complementary in shape to the substrate (geometrically complementary)
Molecules that are different in shape or functional group distribution from the substrate do what?
do not bind to the enzyme; cannot form enzyme-substrate complexes that lead to the formation of products
Enzymes are highly specific in what?
both binding chiral substrates and in catalyzing their reaction
Why does enzyme specificity arise?
because enzymes, by the virtue of their inherent chirality (proteins consist of only L-amino acids), form asymmetric active sites.
If the YAD reaction is carried out with deuterated ethanol, the product NADH is what?
Deuterated
Many organisms are unable to synthesize certain portions of essential cofactors and therefore these substances must be present in the organism’s diet; thus they are _____
vitamins
many coenzymes are what?
growth factors for microorganisms or substance that cure nutritional deficiency diseases in humans and animals
The NAD+ component nicotinamide or its carboxylic acid analog nicotinic acid relieves what?
dietary deficiency disease in humans known as pellagra
Pellagra is characterized by what symptoms?
diarrhea, dermatitis, and dementia
Most animals can synthesize nicotinamide from what?
the amino acid tryptophan
Vitamins in the human diet that are coenzymes precursors are all ______
water soluble vitamins
Vitamin A and Vitamin D are what?
lipid-soluble vitamins
What vitamins are not components of coenzymes?
lipid-soluble vitamins such as vitamin A and D
What are the two ways an organism controls the catalytic activities of its component enzymes so it can coordinate its numerous metabolic processes?
1) Control enzyme availability
2) Control enzyme activity
The amount of a given enzyme depends on what? Which is controlled by what?
both its rate of synthesis and its rate of degradation. controlled by the cell
An enzyme’s catalytic activity may be directly controlled how?
through conformational or structural alterations.
The rate of enzymatically catalyzed reaction is directly proportional to what?
to the concentration of its enzyme-substrate complex which varies with enzyme substrate concentrations and with enzyme’s substrate-binding affinity.
The catalytic activity can be controlled by what?
through variation of its substrate binding affinity
arbitrarily assigned number for YADH?
1: 1: 1: 17
NAD+ oxidoreductase is waht?
an alcohol
Oxidoreductase is what type of reaction catalyzed?
oxidation-reduction
Transferase is what type of reaction catalyzed?
Transfer of functional groups
Hydrolases is what type of reaction catalyzed?
hydrolysis reactions
Lyases is what type of reaction catalyzed?
Group elimination to from double bonds
Isomerases is what type of reaction catalyzed?
Isomerization
Ligases is what type of reaction catalyzed?
Bond formation coupled with ATP hydrolysis
The coenzyme Biotin is what type of reaction mediated?
carboxylation
The coenzyme Cobalamin (B12) is what type of reaction mediated?
Alkylation
The coenzyme, coenzyme A is what type of reaction mediated?
acyl transfer
The coenzyme Flavin is what type of reaction mediated?
oxidation-reduction
The coenzyme Lipoic acid is what type of reaction mediated?
acyl transfer
The coenzyme Nicotinamide is what type of reaction mediated?
oxidation-reduction
The coenzyme Pyridoxal is what type of reaction mediated?
Amino group transfer
The coenzyme tetrahydrofolate is what type of reaction mediated?
One-carbon group transfer
The coenzyme Thiamine pyrophosphate is what type of reaction mediated?
aldehyde transfer
The vitamin Biotin has what coenzyme and causes what human deficency disease?
Biocytin causing human deficency disease is rare or unobserved
The vitamin Cobalamin (b15) has what coenzyme and causes what human deficency disease?
cobalamin (b12) coenzymes) and cause pernicious anemia
The vitamin Folic acid has what coenzyme and causes what human deficency disease?
Tetrahydrofolate and causes Megaloblastic anemia
The vitamin Nicotinamide has what coenzyme and causes what human deficency disease?
Nicotinamide coenzymes and cause pellagra
The vitamin Pantothenate has what coenzyme and causes what human deficency disease?
Coenzyme A and causing human deficency disease is rare or unobserved
The vitamin Pyridoxine (B6) has what coenzyme and causes what human deficency disease?
pyridoxal phosphate causing human deficency disease is rare or unobserved
The vitamin Riboflavin (B2) has what coenzyme and causes what human deficency disease?
Flavin coenzymes causing human deficency disease is rare or unobserved
The vitamin Thiamine (B1) has what coenzyme and causes what human deficency disease?
Thiamine pyrophosphate and causes Beriberi disease
urease catalyzes
hydrolysis of urea
alcohol dehydrgenase catalyzes
the oxidation of alcohols to their corresponding aldehydes
What are the 6 major classes of enzymes
1) Oxidoreductases
2) Transferase
3) Hydrolases
4) Lysases
5) Isomerase
6) Ligases
Each enzyme is assigned
2 names Accepted name and systemic name, The accepted name is used for everyday use and the systemic name is used when ambiguity must be minimized.
What is the systemic name of an enzyme?
name of substrate followed by word ending in -ase
I number identification what does each number mean?
- first number indicates enzymes major class
- second number denotes its subclasses (glycosylases)
- third number designates its sub-sub class (enzymes hydrolyzing )- and S-glycosylcompounds)
- fourth number is enzyme’s arbitrarily assigned serial number in its sub-subclass.
The common name alcohol dehydrogenase has the systemic name of what?
alcohol:NAD+ oxidoreductase
Classification number of alcohol dehydrogenase?
1: 1: 1: 1
dehydrogenases that catalyze reactions whose equilibrium constants with their natural substrates in the direction of reduction are <10^-12 M are almost always transfer _____?
pro-R hydrogen
dehydrogenases that catalyze reactions whose equilibrium constants >10^-10 M generally transfer ____
pro S hydrogen
The NADH hydrogen transferred in a enzymatic reaction is where?
almost certainly on the side of the nicotinamide ring facing the substrate.
Enzymes are selective about the identities of the chemical groups on their substrate are called what?
geometric specificity (size and shape)
Which is a more stringent requirement?
Geometric specificity
Most enzyme catalyze how many enzymes
Most enzymes catalyze the reaction of a small range of related compounds; few enzymes are absolute;y specific for only one compound
