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Questions and Answers
Kinases catalyze the transfer of a phosphate group from adenosine triphosphate (ATP) to give adenosine diphosphate (ADP) and a ______.
Kinases catalyze the transfer of a phosphate group from adenosine triphosphate (ATP) to give adenosine diphosphate (ADP) and a ______.
phosphorylated product
Hydrolases catalyze a hydrolysis reaction in which the addition of a water molecule to a bond causes the bond to ______.
Hydrolases catalyze a hydrolysis reaction in which the addition of a water molecule to a bond causes the bond to ______.
break
Prosthetic groups are tightly incorporated into protein structure by covalent or noncovalent ______.
Prosthetic groups are tightly incorporated into protein structure by covalent or noncovalent ______.
forces
The suffix -ase identifies a substance as an ______.
The suffix -ase identifies a substance as an ______.
Examples of prosthetic groups include derivatives of B vitamins such as pyridoxal phosphate, flavin mononucleotide (FMN), and ______.
Examples of prosthetic groups include derivatives of B vitamins such as pyridoxal phosphate, flavin mononucleotide (FMN), and ______.
Lyases catalyze the addition of a group to a double bond or the removal of a group to form a double bond in a manner that does not involve ______.
Lyases catalyze the addition of a group to a double bond or the removal of a group to form a double bond in a manner that does not involve ______.
Carbohydrases effect the breaking of glycosidic bonds in oligo- and ______.
Carbohydrases effect the breaking of glycosidic bonds in oligo- and ______.
Thiamin (B-1) is also associated with a coenzyme known as ______.
Thiamin (B-1) is also associated with a coenzyme known as ______.
Chirality is inherent in an enzyme active site because amino acids are ______ compounds.
Chirality is inherent in an enzyme active site because amino acids are ______ compounds.
An L-amino acid oxidase will catalyze the oxidation of the L-form of an amino acid but not the ______ form.
An L-amino acid oxidase will catalyze the oxidation of the L-form of an amino acid but not the ______ form.
The degree of enzyme specificity is determined by the ______ site.
The degree of enzyme specificity is determined by the ______ site.
Enzyme activity is a measure of the rate which an enzyme converts substrate to ______ in a biochemical reaction.
Enzyme activity is a measure of the rate which an enzyme converts substrate to ______ in a biochemical reaction.
Absolute specificity refers to an enzyme that will catalyze only ______ reaction.
Absolute specificity refers to an enzyme that will catalyze only ______ reaction.
Catalase is an enzyme with absolute specificity; it catalyzes the conversion of hydrogen peroxide (H2O2) to ______ and H2O.
Catalase is an enzyme with absolute specificity; it catalyzes the conversion of hydrogen peroxide (H2O2) to ______ and H2O.
When the temperature increases beyond a certain point, the increased energy begins to cause disruptions in the ______ structure of the enzyme.
When the temperature increases beyond a certain point, the increased energy begins to cause disruptions in the ______ structure of the enzyme.
Denaturation occurs when the tertiary structure at the active site is ______.
Denaturation occurs when the tertiary structure at the active site is ______.
An enzyme is produced from an apoenzyme and a ______.
An enzyme is produced from an apoenzyme and a ______.
Most enzymes are composed of ______ proteins.
Most enzymes are composed of ______ proteins.
Enzymes cause cellular reactions to occur millions of times faster than corresponding ______ reactions.
Enzymes cause cellular reactions to occur millions of times faster than corresponding ______ reactions.
Cofactors for enzymatic reactions may include vitamins and ______.
Cofactors for enzymatic reactions may include vitamins and ______.
The inactive form of the apoenzyme is known as a ______.
The inactive form of the apoenzyme is known as a ______.
A simple enzyme is composed only of ______.
A simple enzyme is composed only of ______.
Cofactors can provide additional chemically reactive ______ groups.
Cofactors can provide additional chemically reactive ______ groups.
Common cofactors include ______ ions like Zn and Mg.
Common cofactors include ______ ions like Zn and Mg.
Enzyme activity is dramatically affected by changes in ______.
Enzyme activity is dramatically affected by changes in ______.
The protein part of a conjugated enzyme is referred to as an ______.
The protein part of a conjugated enzyme is referred to as an ______.
The products must leave the site before the ______ can be repeated.
The products must leave the site before the ______ can be repeated.
Turnover Number is the number of substrate molecules transformed per minute by one molecule of enzyme under optimum conditions of ______, pH, and saturation.
Turnover Number is the number of substrate molecules transformed per minute by one molecule of enzyme under optimum conditions of ______, pH, and saturation.
If the amount of substrate present is kept constant and the enzyme concentration is increased, the ______ rate increases.
If the amount of substrate present is kept constant and the enzyme concentration is increased, the ______ rate increases.
A noncompetitive inhibitor binds to a site on an enzyme other than the ______ site.
A noncompetitive inhibitor binds to a site on an enzyme other than the ______ site.
An irreversible inhibitor inactivates enzymes by forming a strong ______ bond to an amino acid sidechain group at the enzyme’s active site.
An irreversible inhibitor inactivates enzymes by forming a strong ______ bond to an amino acid sidechain group at the enzyme’s active site.
A competitive inhibitor sufficiently resembles an enzyme substrate in shape and charge distribution that it can compete with the substrate for occupancy of the enzyme’s ______ site.
A competitive inhibitor sufficiently resembles an enzyme substrate in shape and charge distribution that it can compete with the substrate for occupancy of the enzyme’s ______ site.
Enzyme inhibitors slow or stop the normal ______ function of an enzyme by binding to it.
Enzyme inhibitors slow or stop the normal ______ function of an enzyme by binding to it.
Increasing enzyme concentration will ______ the rate of reaction.
Increasing enzyme concentration will ______ the rate of reaction.
Vitamin B12 is also known as ______.
Vitamin B12 is also known as ______.
Water-soluble vitamins circulate in the ______-filled parts of the body.
Water-soluble vitamins circulate in the ______-filled parts of the body.
Fat-soluble vitamins tend to remain in ______-storage sites.
Fat-soluble vitamins tend to remain in ______-storage sites.
Excess vitamin B12 is removed from the body by the ______.
Excess vitamin B12 is removed from the body by the ______.
Vitamin B6 is also referred to as ______.
Vitamin B6 is also referred to as ______.
Vitamin B1 is commonly known as ______.
Vitamin B1 is commonly known as ______.
Folate is also known as ______ acid.
Folate is also known as ______ acid.
Coenzyme A (CoA) is associated with ______ acid.
Coenzyme A (CoA) is associated with ______ acid.
Vitamin B12 transfers ______ groups and hydrogen atoms.
Vitamin B12 transfers ______ groups and hydrogen atoms.
Nicotinamide adenine dinucleotide (NAD+) is associated with ______.
Nicotinamide adenine dinucleotide (NAD+) is associated with ______.
An oxidase enzyme catalyzes an ______ reaction.
An oxidase enzyme catalyzes an ______ reaction.
A hydrolase enzyme catalyzes a ______ reaction.
A hydrolase enzyme catalyzes a ______ reaction.
Oxidoreductase is an enzyme that catalyzes an ______ reduction reaction.
Oxidoreductase is an enzyme that catalyzes an ______ reduction reaction.
Transferase enzymes are involved in the transfer of a ______ group.
Transferase enzymes are involved in the transfer of a ______ group.
A transaminase catalyzes the transfer of an ______ group.
A transaminase catalyzes the transfer of an ______ group.
Coenzyme A (CoA) is associated with ______ acid.
Coenzyme A (CoA) is associated with ______ acid.
Nicotinamide adenine dinucleotide (NAD+) is associated with ______.
Nicotinamide adenine dinucleotide (NAD+) is associated with ______.
Enzymes that catalyze the addition of a group to a double bond are classified as ______.
Enzymes that catalyze the addition of a group to a double bond are classified as ______.
Each substrate must occupy an enzyme active site for a finite amount of time, and the products must leave the site before the cycle can be __________.
Each substrate must occupy an enzyme active site for a finite amount of time, and the products must leave the site before the cycle can be __________.
Turnover Number is the number of substrate molecules transformed per minute by one molecule of enzyme under optimum conditions of temperature, pH, and __________.
Turnover Number is the number of substrate molecules transformed per minute by one molecule of enzyme under optimum conditions of temperature, pH, and __________.
If the amount of substrate present is kept constant and the enzyme concentration is increased, the reaction rate __________.
If the amount of substrate present is kept constant and the enzyme concentration is increased, the reaction rate __________.
A noncompetitive inhibitor is a molecule that decreases enzyme activity by binding to a site on an enzyme other than the __________ site.
A noncompetitive inhibitor is a molecule that decreases enzyme activity by binding to a site on an enzyme other than the __________ site.
An irreversible inhibitor inactivates enzymes by forming a strong __________ bond to an amino acid sidechain group at the enzyme’s active site.
An irreversible inhibitor inactivates enzymes by forming a strong __________ bond to an amino acid sidechain group at the enzyme’s active site.
A competitive inhibitor sufficiently resembles an enzyme substrate in shape and charge distribution that it can compete with the substrate for occupancy of the enzyme’s __________ site.
A competitive inhibitor sufficiently resembles an enzyme substrate in shape and charge distribution that it can compete with the substrate for occupancy of the enzyme’s __________ site.
Enzyme inhibitors slow or stop the normal catalytic __________ of an enzyme by binding to it.
Enzyme inhibitors slow or stop the normal catalytic __________ of an enzyme by binding to it.
Increasing enzyme concentration will __________ the rate of reaction.
Increasing enzyme concentration will __________ the rate of reaction.
Statins are known as HMG Coenzyme A reductase inhibitors which lower serum ______ concentration.
Statins are known as HMG Coenzyme A reductase inhibitors which lower serum ______ concentration.
Emtricitabine and Tenofovir Disoproxil Fumarate are inhibitors of viral reverse ______.
Emtricitabine and Tenofovir Disoproxil Fumarate are inhibitors of viral reverse ______.
Angiotensin Converting Enzyme (ACE) inhibitors interfere with the body’s ______ System.
Angiotensin Converting Enzyme (ACE) inhibitors interfere with the body’s ______ System.
Lactam antibiotics, such as Penicillin, inhibit ______ synthesis by targeting bacterial enzymes.
Lactam antibiotics, such as Penicillin, inhibit ______ synthesis by targeting bacterial enzymes.
Sulfa drugs mimic ______, which is vital for folic acid synthesis in bacteria.
Sulfa drugs mimic ______, which is vital for folic acid synthesis in bacteria.
Lactate Dehydrogenase (LDH) is an enzyme associated with possible tissue damage, particularly in cases of heart and ______ disease.
Lactate Dehydrogenase (LDH) is an enzyme associated with possible tissue damage, particularly in cases of heart and ______ disease.
Water-soluble vitamins, including Vitamin C and B6, circulate in ______-filled parts of the body.
Water-soluble vitamins, including Vitamin C and B6, circulate in ______-filled parts of the body.
Excess vitamin B12 is removed from the body via the ______.
Excess vitamin B12 is removed from the body via the ______.
An enzyme that catalyzes the isomerization of a substrate is called an ______.
An enzyme that catalyzes the isomerization of a substrate is called an ______.
The enzyme that catalyzes the bonding of two molecules with the participation of ATP is known as a ______.
The enzyme that catalyzes the bonding of two molecules with the participation of ATP is known as a ______.
Oxidoreductase enzymes are involved in ______ reactions.
Oxidoreductase enzymes are involved in ______ reactions.
Chymotrypsin is an example of a type of enzyme known as a ______.
Chymotrypsin is an example of a type of enzyme known as a ______.
The part of the enzyme's structure that is involved in catalysis is called the ______ site.
The part of the enzyme's structure that is involved in catalysis is called the ______ site.
The process by which an enzyme's activity is reduced or stopped is referred to as ______.
The process by which an enzyme's activity is reduced or stopped is referred to as ______.
The term for enzymes that only catalyze a single reaction is called ______ specificity.
The term for enzymes that only catalyze a single reaction is called ______ specificity.
Vitamins may act as ______ for enzymatic reactions, helping to facilitate various biochemical processes.
Vitamins may act as ______ for enzymatic reactions, helping to facilitate various biochemical processes.
Vitamin B12 is also known as ______.
Vitamin B12 is also known as ______.
Water-soluble vitamins circulate in the ______-filled parts of the body.
Water-soluble vitamins circulate in the ______-filled parts of the body.
Fat-soluble vitamins tend to remain in ______-storage sites.
Fat-soluble vitamins tend to remain in ______-storage sites.
Excess vitamin B12 is removed from the body by the ______.
Excess vitamin B12 is removed from the body by the ______.
Coenzyme A (CoA) is associated with ______ acid.
Coenzyme A (CoA) is associated with ______ acid.
Folate is also known as ______ acid.
Folate is also known as ______ acid.
Vitamin B6 is also referred to as ______.
Vitamin B6 is also referred to as ______.
Vitamin B1 is commonly known as ______.
Vitamin B1 is commonly known as ______.
Vitamin B12 transfers ______ groups and hydrogen atoms.
Vitamin B12 transfers ______ groups and hydrogen atoms.
Nicotinamide adenine dinucleotide (NAD+) is associated with ______.
Nicotinamide adenine dinucleotide (NAD+) is associated with ______.
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Study Notes
Enzymes
- Enzymes are biological catalysts, primarily proteins that accelerate biochemical reactions.
- Majority of enzymes are globular proteins, capable of undergoing denaturation.
- Enzymes accelerate cellular reactions, achieving rates millions of times faster than their uncatalyzed counterparts.
- Enzyme activity is significantly influenced by factors like temperature, pH fluctuations, and denaturants.
- Enzymes are classified structurally into two primary categories:
- Simple Enzymes: Comprised solely of protein (amino acid chains).
- Conjugated Enzymes: Contain a nonprotein component in addition to protein.
- Apoenzyme: The protein portion of a conjugated enzyme. Its inactive form is known as Proenzyme/Zymogen.
- Cofactor: The nonprotein component of a conjugated enzyme, sometimes referred to as coenzymes. They provide additional chemically reactive functional groups.
Enzyme Cofactors
- Cofactors are molecules that assist enzymes in their catalytic activity.
- Common cofactors include vitamins and metal ions.
- Metal ion activators are inorganic and bind through coordinate covalent bonds. Examples include Zn, Mg, Mn, Fe, Cu, K, and Na.
- Holoenzyme: The active form of a conjugated enzyme, formed by the combination of an apoenzyme and a cofactor.
Enzyme Structure
- The structure of an enzyme's active site dictates its specificity.
- Enzyme specificity refers to the degree to which an enzyme's activity is restricted to a certain substrate, group of substrates, bond type, or reaction type.
- Absolute Specificity: The enzyme catalyzes only one reaction with a single substrate. This is highly restrictive and uncommon. Catalase is an example, converting hydrogen peroxide to O2 and H2O.
Enzyme Nomenclature
- The suffix '-ase' identifies a substance as an enzyme. Examples include urease, sucrase, and lipase.
- The type of reaction catalyzed by an enzyme is often indicated using a prefix.
- Chirality is inherent in an enzyme's active site due to the chiral nature of amino acids. For instance, an L-amino acid oxidase will catalyze L-amino acid oxidation, but not its D-isomer.
Factors Affecting Enzyme Activity
- Enzyme Activity: Reflects the rate at which an enzyme transforms substrate into products in a biochemical reaction.
- Four key factors affecting enzyme activity:
- Temperature: Enzyme activity increases with temperature until an optimal point is reached. Further increases lead to denaturation and reduced activity.
- pH: Enzymes have optimal pH ranges, deviating from which alters structure and reduces activity.
- Substrate Concentration: Increased substrate concentration results in increased reaction rate until saturation is reached (all active sites are occupied).
- Enzyme Concentration: Increasing enzyme concentration at constant substrate levels increases reaction rate as more substrate molecules can be accommodated.
Enzyme Inhibition
- Enzyme Inhibitor: A molecule that reduces or halts an enzyme’s normal catalytic function by binding to it.
- Types of Inhibitors:
- Competitive Inhibitor: Resembles the substrate in shape and charge, competing for the enzyme's active site.
- Noncompetitive Inhibitor: Binds to a site on the enzyme other than the active site, decreasing enzyme activity.
- Irreversible Inhibitor: Inactivates enzymes by forming a strong covalent bond with an amino acid sidechain group at the active site.
Enzymes in Clinical Use
- Certain enzymes are targets for drug actions.
- Turnover Number: The number of substrate molecules transformed per minute by a single enzyme molecule under optimal conditions.
Vitamin B
- The B Vitamins are structurally diverse and are major components of coenzymes.
- Preferred and alternative names for B vitamins:
- Thiamin - Vitamin B1
- Riboflavin - Vitamin B2
- Niacin - Nicotinic acid, Nicotinamide, Vitamin B3
- Vitamin B6 – Pyridoxine, Pyridoxal, Pyridoxamine
- Folate – folic acid
- Vitamin B12 – cobalmin
- Pantothenic acid – Vitamin B5
- Biotin – Vitamin B7
B Vitamins and Coenzymes
- Thiamin (B1): Thiamin pyrophosphate (TPP) – Transfers aldehydes
- Riboflavin (B2): Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) – Transfers hydrogen atoms
- Niacin (B3): Nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+) – Transfers hydrogen atoms
- Pantothenic acid (B5): Coenzyme A (CoA) – Transfers acyl groups
- Vitamin B6: Pyridoxal-5-phosphate (PLP), pyridoxine-5’-phophate (PNP), pyridoxamine-5’-phosphate (PMP) – Transfers amino groups
- Biotin (B7): Biotin – Transfers carbon dioxide (Carboxyl group)
- Folate: Tetrahydrofolate (THF) – Transfers one-carbon groups other than CO2
- Vitamin B12: Methylcobalamin – Transfers methyl groups and hydrogen atoms
Vitamin A
- Four Major Functions:
- Vision: Key component of rhodopsin, a light-sensitive pigment in the retina.
- Growth and Development: Essential for normal growth and development, particularly of epithelial tissues.
- Immune Function: Supports immune system function by maintaining healthy epithelial barriers.
- Reproduction: Plays a role in male reproductive health, including sperm production.
Vitamin E
- Four Major Functions:
- Antioxidant: Protects cell membranes from oxidative damage.
- Immune Function: Supports immune system health.
- Blood Clotting: May influence blood clotting.
- Nerve Function: May be involved in nerve function.
Water-Soluble vs. Fat-Soluble Vitamins
| Category | Characteristics | Examples |
|---|---|---|
| Water-Soluble: | - Directly absorbed into the bloodstream. - Travel without carriers. - Circulate in the body's water-filled spaces. - Stored in the body but not for prolonged periods. - Excreted in urine. - Less likely to reach toxic levels. - Required in frequent doses. - Often function as coenzymes. | B Vitamins, Vitamin C |
| Fat-Soluble: | - Enter the lymph first. - Many need protein carriers. - Found in cells associated with fat. - Stored in fat storage sites. - Can reach toxic levels with excessive intake. - Needed in periodic doses. - Do not function as coenzymes. | Vitamins A, D, E, K |
Enzymes Overview
- An enzyme is a protein that catalyzes a specific chemical reaction in the body.
- Enzymes have an active site that binds to the substrate, the molecule on which the enzyme acts.
- The suffix "-in" is often used in enzyme names, such as trypsin, chymotrypsin, and pepsin.
- Six main classes of enzymes:
- Oxidoreductase: Catalyzes an oxidation-reduction reaction.
- Transferase: Transfers a functional group from one molecule to another.
- Hydrolase: Catalyzes hydrolysis reactions.
- Lyase: Adds or removes groups to/from double bonds.
- Isomerase: Rearranges atoms within a molecule.
- Ligase: Joins two molecules together.
Models of Enzyme Action
- Lock-and-key model: the active site of an enzyme is a perfect fit for the substrate.
- Induced fit model: The active site of an enzyme changes shape to fit the substrate.
Enzyme Concentration
- As enzyme concentration increases, the reaction rate increases, as more substrate molecules can be accommodated.
Enzyme Inhibition
- Enzyme inhibitors: molecules that slow or stop enzyme activity by binding to the enzyme.
- Competitive inhibitors: Molecules that bind to the active site, competing with the substrate.
- Noncompetitive inhibitors: Molecules that bind to a site on the enzyme other than the active site.
- Irreversible inhibitors: Molecules that inactivate enzymes by forming a strong covalent bond with the active site.
Enzymes in Clinical Use
- Statins: Inhibit HMG CoA reductase to lower serum lipid concentration.
- Emtricitabine and Tenofovir Disoproxil Fumarate: Inhibit viral reverse transcriptase to block HIV replication.
- ACE inhibitors: Inhibit the conversion of angiotensin I to angiotensin II, lowering blood pressure.
- Lactam antibiotics: Inhibit alanyl alanine carboxypeptidase transpeptidase, blocking cell wall synthesis in bacteria.
- Sulfa drugs: Mimic PABA, hindering bacterial growth by interfering with folic acid synthesis.
Selected Blood Enzyme Assays
- Lactate Dehydrogenase (LDH), Creatinine Phosphokinase (CPK), Aspartate Transaminase (AST), Alanine Transaminase (ALT), Gamma-glutamyl Transpeptidase (GGTP), and Alkaline Phosphatase (ALP) are enzymes used in diagnostic medicine to assess tissue damage and disease.
Vitamins
- Vitamins are organic compounds essential for human health obtained from dietary sources.
- Water-soluble vitamins are absorbed directly into the bloodstream and excreted in urine.
- Fat-soluble vitamins are absorbed into the lymph system and stored in fat-storage sites.
Vitamin B
- A group of structurally diverse vitamins that are essential for the functioning of coenzymes.
Vitamin A
- Essential for vision, growth, and immune system function.
- Forms retinol, retinal, and retinoic acid.
Vitamin E
- An antioxidant that protects cell membranes from damage.
- Also known as tocopherol.
Vitamin D
- Essential for calcium absorption and bone health.
Vitamin K
- Essential for blood clotting.
Co-enzymes
- Coenzymes are non-protein organic molecules that assist enzymes in catalyzing reactions.
- Many B vitamins are components of coenzymes.
- Coenzymes do not undergo permanent chemical change
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