Biochemistry Enzymes and Cofactors Quiz

The specific region on an enzyme molecule where low-molecular substances bind, but are different in structure from the enzyme's substrates.

Substances that slow down enzyme reactions by binding to the enzyme and inhibiting its activity. They don't change the enzyme's structure permanently.

The process of breaking down complex molecules into simpler ones, releasing energy.

The process of building up complex molecules from simpler ones, using energy.

A specific characteristic of enzymes that allows them to interact with a particular substrate.

A derivative of vitamin PP (niacin) that participates in dehydrogenation reactions, often working as a coenzyme in redox reactions.

A derivative of vitamin thiamine (B1) that participates in oxidative decarboxylation of keto acids, a crucial step in energy metabolism.

A type of vitamin known as a coenzyme, capable of accepting and donating electrons and protons via its pyrimidine ring, specifically referring to vitamin B2 (riboflavin).

Pyruvate is the end product of glycolysis, a central pathway in carbohydrate metabolism.

The common pathway of catabolism refers to the metabolic processes that break down various nutrients (carbohydrates, fats, and proteins) into a common intermediate, acetyl-CoA, which then enters the Krebs cycle.

Acetyl-CoA is a central intermediate in metabolism, playing a key role in the breakdown of carbohydrates, lipids, and proteins.

Substrate phosphorylation involves the direct transfer of a phosphate group from a high-energy substrate molecule to ADP, generating ATP. It is the primary mechanism for ATP production in glycolysis.

The primary electron acceptor in the respiratory chain is NAD+ (nicotinamide adenine dinucleotide), which receives electrons from various metabolic reactions and carries them to the electron transport chain.

The first complex of the respiratory chain, NADH dehydrogenase, accepts electrons from NADH and transfers them to ubiquinone (coenzyme Q).

Oxygen is the final electron acceptor in the respiratory chain. As electrons move down the chain, they release energy, which is used to pump protons across the mitochondrial membrane, creating a proton gradient that drives ATP synthesis.

The correct sequence of the respiratory chain is: NADH, FMN, ubiquinone, cytochrome b, cytochrome c1, cytochrome c, cytochrome a, cytochrome a3. This sequence ensures the stepwise transfer of electrons, releasing energy at each step.

The pentose phosphate pathway is crucial for generating NADPH2, a reducing agent essential for various biosynthetic processes, and ribose-5-phosphate, a precursor for nucleotide synthesis.

Glucose-6-phosphate dehydrogenase is the key enzyme in the pentose phosphate pathway responsible for generating NADPH2.

The pentose phosphate pathway is a metabolic route that produces both NADPH2 and ribose-5-phosphate, crucial for various cellular processes.

NADPH2 is a vital reducing agent used in various biosynthetic paths, including fatty acid, cholesterol, and steroid synthesis, detoxification, and protection against oxidative stress.

The oxidative phase of the pentose phosphate pathway produces ribulose-5-phosphate. This is the initial stage where NADPH2 is generated.

The non-oxidative stage of the pentose phosphate pathway produces ribose-5-phosphate. This phase utilizes the products of the oxidative stage to generate ribose.

Pentoses produced in the pentose phosphate pathway are essential for generating purine and pyrimidine nucleotides, the building blocks of DNA and RNA.

Ribose-5-phosphate is a crucial product of the pentose phosphate pathway as it is the direct precursor for the synthesis of nucleic acids.

The oxidative stage of the pentose phosphate pathway involves the reduction of NADP+ to NADPH. Reducing NADP+ to NADPH requires the addition of electrons, which is why it is considered a reduction reaction.

Glucose-6-phosphate dehydrogenase is the regulatory enzyme of the pentose phosphate pathway. Its activity controls the pathway's rate and determines the production of NADPH and precursor molecules for nucleotide synthesis.

Glucose-6-phosphate is the primary substrate for the pentose phosphate pathway. This molecule is the starting point for the pathway, providing the necessary carbon units for subsequent reactions.

Gluconeogenesis primarily synthesizes glucose from non-carbohydrate precursors such as lactate, amino acids, glycerol, and glycerol-3-phosphate. These substrates are converted to glucose to maintain blood glucose levels and provide energy for various tissues.

Amino acids are substrates of gluconeogenesis, formed during the breakdown of muscle proteins. These amino acids can be converted into glucose via the gluconeogenesis pathway, supplementing energy supply during times of glucose deficiency.

Phosphoenolpyruvate carboxykinase (PEPCK) catalyzes the conversion of oxaloacetate to phosphoenolpyruvate, a critical step in gluconeogenesis. This reaction bypasses the irreversible step of pyruvate kinase in glycolysis, allowing for glucose synthesis.

Lactate, produced during anaerobic glycolysis, is involved in gluconeogenesis in the liver. The Cori cycle involves the conversion of lactate to glucose in the liver, which can then be released back into the bloodstream to be used as energy by various tissues.

The specific enzymatic reaction of gluconeogenesis is the conversion of pyruvate to glucose. This complex pathway involves several steps, including the conversion of pyruvate to oxaloacetate, then to phosphoenolpyruvate, followed by a series of reactions to finally produce glucose.

Histamine is a chemical messenger involved in the body's inflammatory response. It triggers the release of gastric juice, dilates blood vessels, and increases blood flow to the affected area.

Dopamine is inactivated through oxidation by MAO enzymes, which break down the neurotransmitter. This prevents dopamine from accumulating and causing imbalances in the brain.

Tetrahydrofolic acid (H4-folate) is a crucial coenzyme involved in the transfer of one-carbon units, which are essential for various metabolic processes like DNA synthesis and amino acid metabolism.

Glycine is the amino acid precursor for the synthesis of porphyrins, which are complex organic molecules that make up the heme group in hemoglobin and other important proteins.

S-adenosylmethionine (SAM) is the active form of methionine. It is synthesized from methionine and ATP using the enzyme methionine adenosyltransferase. SAM is a crucial methyl donor in various metabolic reactions.

Methionine acts as the sulfur donor in the synthesis of cysteine, an important amino acid involved in various metabolic reactions.

Phenylketonuria (PKU) is a genetic disorder caused by a deficiency in the enzyme phenylalanine hydroxylase. This enzyme converts phenylalanine to tyrosine. PKU can lead to intellectual disability, seizures, and problems with behavior if left untreated.

S-Adenosylmethionine (SAM) donates its methyl group to detoxify various substances, including toxic metabolites of medications, contributing to the overall detoxification process in the body.

The brain is the organ most vulnerable to low blood sugar levels during prolonged fasting.

Gluconeogenesis is the process where the body generates glucose from non-carbohydrate sources like amino acids and glycerol when blood sugar is low.

Glycogen phosphorylase is an enzyme crucial for breaking down glycogen stored in the liver and muscles. Deficiency in this enzyme leads to low blood sugar (hypoglycemia) as glycogen can't be properly utilized.

Glucose-6-phosphatase is a liver-specific enzyme vital for regulating blood glucose levels. It converts glucose-6-phosphate into free glucose, which can then be released into the bloodstream.

The formation of ribulose-5-phosphate happens during the oxidative phase of the pentose phosphate pathway. This specific reaction is catalyzed by a decarboxylation process.

The transaldose enzyme catalyzes the transformation of sedoheptulose-7-phosphate and glyceraldehyde-3-phosphate into erythroso-4-phosphate and fructose-6-phosphate, essential steps in the pentose phosphate pathway.

Isomerase is an enzyme that changes the structure of ribulose-5-phosphate, converting it into ribose-5-phosphate. This is vital for nucleotide synthesis.

Phosphorylation and dephosphorylation are the processes of adding or removing phosphate groups from molecules, respectively. This is a common way to modify enzyme activity, including glycogen phosphorylase and glycogen synthase.