Enzyme Function and Carbohydrate Chemistry

Enzyme

Biological catalyst increasing reaction rates without change.

Activation Energy

Energy required to initiate a chemical reaction.

Carbonic Anhydrase

an enzyme that converts CO2 and H2O into carbonic acid and then turns into bicarbonate +hydrogen ions

Substrate

Molecule that binds to an enzyme's active site.

Active Site

Region on enzyme where substrates bind for reaction.

Enzyme-Substrate Complex

Combination of enzyme and substrate during catalysis.

Enzyme-Product Complex

Intermediate formed after substrate conversion in enzyme.

Lactase

Enzyme that catalyzes lactose hydrolysis into monosaccharides.

Quaternary Structure

Protein structure with multiple subunits, like lactase.

Absolute Specificity

Enzymes catalyzing only one specific substrate reaction.

Lock-and-Key Model

Rigid substrate fits rigid enzyme like a key.

Induced-Fit Model

Flexible enzyme adapts to substrate shape for catalysis.

Phosphorylation

Covalent modification activating or deactivating an enzyme.

Kinase

Enzyme that activates others by adding phosphate groups.

Phosphatase

Enzyme that removes phosphate groups to activate enzymes.

Allosteric Enzymes

Enzymes regulated by binding at sites other than active site.

Positive Regulator

Molecule enhancing substrate binding to the active site.

Negative Regulator

Molecule preventing substrate binding, decreasing reaction rate.

Feedback Control

Regulatory mechanism using end product to control enzyme activity.

Regulatory Enzymes

Enzymes controlling reaction rates based on substrate levels.

Hydrogen Bonds

Weak interactions stabilizing enzyme-substrate complexes.

Salt Bridges

Ionic interactions contributing to enzyme structure stability.

Hydrophobic Interactions

Nonpolar interactions aiding enzyme-substrate binding.

Feedback control

End product binds to allosteric enzyme, regulating synthesis.

Allosteric enzyme

First enzyme in a reaction sequence, regulated by end product.

Noncompetitive inhibitor

Does not resemble substrate; binds elsewhere on enzyme.

Inhibitors

Molecules causing loss of catalytic activity in enzymes.

Reversible inhibition

Loss of enzyme activity that can be restored.

Competitive inhibitor

Competes with substrate for the active site.

Antimetabolites

Competitive inhibitors used to treat bacterial infections.

Sulfanilamide

Competes with PABA, inhibiting(preventing) bacterial growth.

Irreversible inhibition

Enzyme activity destroyed by covalent bond with inhibitor.

Covalent modification

Enzyme activity modified by forming or breaking covalent bonds.

Zymogens

Inactive enzyme precursors activated by covalent modification.

Proteases

Digestive enzymes that hydrolyze proteins from inactive forms.

Trypsinogen

Zymogen activated to trypsin for protein digestion.

Proinsulin

Inactive form of insulin, activated by peptide removal.

Cofactor

Non-protein molecule required for enzyme activity.

Coenzyme

Small organic molecule, often a vitamin, aiding enzymes.

Carboxypeptidase

Enzyme requiring Zn2+ cofactor for peptide bond hydrolysis.

Vitamins

Organic molecules essential for health, required in trace amounts.

Optimum pH

pH level where enzymes function best, around 7.4.

Carbohydrates

Major energy source, made of carbon, hydrogen, oxygen.

Photosynthesis

Process plants use to produce glucose from CO2 and H2O.

Saccharides

Another term for sugars, referring to carbohydrate structure.

C-terminal aromatic amino acid

Target of carboxypeptidase during peptide bond hydrolysis.

Monosaccharides

Simple carbohydrates, single sugar units.

Disaccharides

Two monosaccharides linked together.

Polysaccharides

Many monosaccharides linked together.

Aldoses

Monosaccharides with an aldehyde group.

Ketoses

Monosaccharides with a ketone group.

Triose

Monosaccharide with three carbon atoms.

Tetrose

Monosaccharide with four carbon atoms.

Pentose

Monosaccharide with five carbon atoms.

Hexose

Monosaccharide with six carbon atoms.

Aldopentose

Five-carbon saccharide with an aldehyde group.

Ketohexose

Six-carbon saccharide with a ketone group.

d-Glucose

Most common hexose, known as blood sugar.

d-Galactose

Aldohexose obtained from lactose in milk.

Galactosemia

Condition due to missing enzyme for galactose conversion.

d-Fructose

Ketohexose, sweetest carbohydrate, found in fruits.

High-fructose corn syrup

Sweetener made from sucrose hydrolysis.

Haworth structures

Cyclic forms of sugars from carbonyl and hydroxyl reaction.

Fischer projection

2D representation of carbohydrates showing stereochemistry.

α-anomer

Cyclic form with -OH group below the ring.

β-anomer

Cyclic form with -OH group above the ring.

Sugar alcohols

Reduced carbohydrates used as sweeteners in products.

Glucose tolerance test

Measures blood glucose after glucose ingestion.

Aldehyde group

Functional group with a carbonyl and hydrogen.

Hydroxyl group

Functional group containing an -OH group.

Sugar acids

Carbohydrates(H) oxidized to carboxylic(0H) acids.

Benedict's solution

Oxidizing agent for reducing sugars.

Reducing sugar

Carbohydrate that reduces another substance.

Fructose

Ketohexose with a ketone group.

Ketohexose

Hexose with a ketone functional group.

Glucose

Aldose that can be oxidized easily.

Sugar alcohols

Reduced monosaccharides, also called alditols.

D-sorbitol

Sugar alcohol derived from D-glucose.

D-xylitol

Sugar alcohol derived from D-xylose.

D-mannitol

Sugar alcohol derived from D-mannose.

Disaccharide

Carbohydrate formed from two monosaccharides.

Glycosidic bond

Covalent bond linking monosaccharides.

Lactose

Disaccharide of galactose and glucose.

Maltose

Disaccharide known as malt sugar.

α-(1→4)-glycosidic bond

Bond between carbon 1 and 4 of glucose.

β-(1→4)-glycosidic bond

Bond in lactose between galactose and glucose.

Sucrose

Disaccharide of glucose and fructose.

α,β-(1→2)-glycosidic bond

Bond between glucose and fructose in sucrose.

Sucralose

Chlorinated derivative of sucrose, artificial sweetener.

Aspartame

Noncarbohydrate sweetener made from amino acids.

Sweetness scale

Sucrose assigned a sweetness value of 100.

Neotame

Artificial sweetener 10,000 times sweeter than sucrose.

Saccharin

Noncarbohydrate sweetener, banned in Canada.

Lactose

Disaccharide of α-D-Glucose and β-D-Galactose.

Maltose

Disaccharide of two α-D-Glucose units.

Sucrose

Disaccharide of α-D-Glucose and β-D-Fructose.

Melibiose

Disaccharide of α-D-Galactose and α-D-Glucose.

Glycosidic bond

Covalent bond linking monosaccharides in carbohydrates.

α-(1→6)-glycosidic bond

Bond linking α-D-Glucose and α-D-Galactose in melibiose.

Cellulose

Polysaccharide of glucose with β-(1→4)-glycosidic bonds. >>> humans lack cellulose