Enzymes Flashcards
Diverse group of water-insoluble biological molecules; fats – energy stores; phospholipids and sterols – major
components of membrane.
Lipids
Polyhydroxy aldehydes and ketones with the
general formula of (CH2O)n.
Carbohydrates
Most complex and most abundant
organic molecules containing at least one
carboxyl group and one amino group.
Proteins
DNA carries coded information, arranged into genes, that is passed from each cell to its daughter cells and from one generation to the next; RNA instrumental in translating the coded message of DNA into sequences of amino acids during synthesis of protein molecules
Nucleic Acid
The process of increasing the rate of reaction with the use of a catalyst.
Catalysis
Any substance that increases rate of reaction upon addition to a certain reaction
Catalyst
Catalyst of biochemical reactions (biological catalysts). Neither used up in the reaction nor do they appear as reaction products
Enzymes
Catalyzes all the synthetic and metabolic
reactions of the cell that allows for a faster speed of reaction. Increases the rate of reaction by means of
lowering the activation energy
Enzymes
Measured as the number of calories required to bring all the molecules in a mole of reactant at a given temperature to a reactive (or activated) state.
Activation energy
How do enzymes hasten the reaction?
Enzyme lowers the activation energy needed
Enzyme (E) binds with a substrate (S) to form an activated:
Enzyme-substrate complex (ES)
reactions catalyzed by enzymes are usually __________ to ________ times faster than uncatalyzed reactions.
10^3 to 10^17
Trait of an enzyme being specific for a certain substrate:
Enzyme Specificity
Specificity of enzymes varies on:
Stereoisomerism
Enzyme present in the intestine that hydrolyses any peptide bond where the carbonyl belongs to a phenylalanine, tyrosine, or tryptophan residue.
Chymotrypsin
Close and complementary fit between enzymes and substrate in a special portion of the enzyme surface
Active Site
Two enzyme-substrate complex models
Lock and Key model, Induced Fit model
Catalytic potential of an enzyme
Enzyme activity
Number of reactions catalyzed per second by the enzyme
Turnover number
How enzymes accelerate reactions
- Hold substrates in close proximity; increasing reaction probability
- Presence of proton donors and acceptors in the binding site
- Forms an unstable intermediate that readily
undergoes second reaction
Factors affecting Enzyme activity
temperature, pH level, cofactors, and coenzymes
Increases enzymatic activity by increasing the kinetic energy, thus number of molecular collisions increases, increasing the probability of reaction between molecules
Temperature
An extreme increase in temperature leads to the __________ of the enzymes
denaturation
in pH level exposes more positive sites in the enzyme for interactions with negative groups on substrates
Drop
_____ in pH level facilitates the binding of positive groups in a substrate to negative sites in the enzyme
Rise
Small organic molecules that act as cofactors
coenzymes
An enzyme minus its cofactor; cannot function without its cofactor/coenzyme.
Apoenzyme
Cofactor + apoenzyme
Holoenzyme
Enzyme that facilitates oxidation-reduction reaction
Oxidoreductase
Enzyme that catalyzes the transfer of functional groups
Transferases
Enzymes that facilitate Hydrolysis reactions
Hydrolase
Enzyme that facilitates the addition or removal of groups to form double bonds
Lyase
Enzyme that facilitates Isomerization(intramolecular group transfer)
Isomerase
Enzymes that facilitate ligation of two substrates at the expense of ATP hydrolysis
Ligases
The rate at which an enzymatic reaction proceeds depends on the concentrations of substrate, product, and active enzymes.
Enzyme Kinetics
Means of controlling enzymatic reactions used by living cells.
Enzyme Inhibition
Two types of Enzyme Inhibition
Competitive and Non-competitive
Inhibition where inhibitor molecules directly reacts with the active site of an enzyme
Competitive inhibition
Most common type of competitive inhibition
Substrate analogs
Caused by inhibitor molecules that bind outside the active site.
Non-competitive inhibition
Regulation of metabolic reactions
- Control of Enzyme Synthesis
- Control of Enzyme Activity
- End-product(feedback) inhibition
Alters the tertiary structure of an enzyme thus changing the conformation of the active site
allosteric site
Interactions of the end products in the allosteric site, making the end product an _________________
allosteric inhibitor
Some cat-ion cofactors acts as allosteric activators for some enzyme
Enzyme Activation
Two kinds of metabolic pathways in animal tissues
Anaerobic and aerobic
Metabolic pathway where food molecules are completely oxidized to carbon dioxide and water by molecular oxygen. Greater energy yield
Aerobic metabolism
Incomplete oxidation of food molecules converting it to lactic acid; due to absence of oxygen
Anaerobic metabolism
