Biochemistry Quiz: Enzymes and Metabolism
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Questions and Answers

What role do enzymes play in biological processes?

Enzymes act as biological catalysts that direct metabolic events, exhibit specificity toward substrates, and regulate metabolism.

How are proteins formed from amino acids?

Proteins are formed through the dehydration polymerization of amino acids, where each amino acid is linked by peptide bonds.

Why is the three-dimensional structure of proteins significant?

The three-dimensional structure of proteins is crucial because it determines their biological activity and functionality.

Explain the concept of protein denaturation.

<p>Protein denaturation is the unfolding and disorganization of a protein's structure, often irreversible, leading to loss of biological function.</p> Signup and view all the answers

What are the classifications of carbohydrates?

<p>Carbohydrates can be classified into monosaccharides, disaccharides, and polysaccharides.</p> Signup and view all the answers

What distinguishes a disaccharide from a monosaccharide?

<p>A disaccharide is made up of two monosaccharides joined by glycosidic linkages, while a monosaccharide is the simplest sugar unit.</p> Signup and view all the answers

What is the significance of amino acid composition in proteins?

<p>The type, nature, and number of amino acids in a protein determine its characteristic properties and functions.</p> Signup and view all the answers

How do carbohydrates function in living organisms?

<p>Carbohydrates provide energy and act as storage molecules of energy in living organisms.</p> Signup and view all the answers

What is the primary function of ATP in cellular metabolism?

<p>The primary function of ATP is to provide energy for various biochemical reactions in the cell.</p> Signup and view all the answers

Describe the process of β-oxidation of fatty acids.

<p>β-oxidation is the metabolic pathway where fatty acids are broken down in the mitochondria to generate acetyl-CoA, NADH, and FADH2.</p> Signup and view all the answers

What is meant by the term 'free energy' in biochemical reactions?

<p>Free energy refers to the energy available to do work in a system, which determines the spontaneity and equilibrium of biochemical reactions.</p> Signup and view all the answers

How does the electron transport chain contribute to ATP production?

<p>The electron transport chain generates a proton gradient that drives ATP synthesis through oxidative phosphorylation.</p> Signup and view all the answers

What role do uncouplers play in cellular respiration?

<p>Uncouplers disrupt the proton gradient, leading to the dissipation of energy as heat rather than producing ATP.</p> Signup and view all the answers

What is the significance of the Kreb's cycle in metabolism?

<p>The Kreb's cycle, also known as the citric acid cycle, plays a central role in the oxidation of acetyl-CoA to generate electron carriers NADH and FADH2.</p> Signup and view all the answers

Identify and explain one respiratory poison and its mechanism of action.

<p>Cyanide is a respiratory poison that inhibits cytochrome c oxidase in the electron transport chain, preventing ATP production.</p> Signup and view all the answers

Explain the process of lipid digestion and absorption in the body.

<p>Lipid digestion involves emulsification by bile salts and hydrolysis by lipases, followed by absorption of fatty acids and monoglycerides into intestinal cells.</p> Signup and view all the answers

What is zymogen activation and provide an example?

<p>Zymogen activation is the process where inactive enzyme precursors are converted into their active forms through hydrolysis, such as pepsinogen converting to pepsin.</p> Signup and view all the answers

How does reversible covalent modification regulate enzyme activity?

<p>Reversible covalent modification regulates enzyme activity by adding or removing phosphate groups, as seen in the phosphorylation of phosphorylase kinase by protein kinases.</p> Signup and view all the answers

Define allosteric modulation and its effect on enzymatic activity.

<p>Allosteric modulation involves small molecules binding to an enzyme at sites distinct from the active site, causing conformational changes that either enhance or inhibit catalytic activity.</p> Signup and view all the answers

What are feedback inhibitors and how do they function in metabolic pathways?

<p>Feedback inhibitors are end products that inhibit the activity of enzymes in a metabolic pathway, effectively stopping the pathway when enough product is produced.</p> Signup and view all the answers

What distinguishes positive allosteric effectors from negative effectors?

<p>Positive allosteric effectors enhance the enzyme's catalytic activity, while negative effectors decrease it.</p> Signup and view all the answers

What role does the Vmax play in enzyme kinetics related to allosteric regulation?

<p>Vmax represents the maximum reaction rate of an enzyme, which can be increased or decreased by allosteric effectors, influencing overall enzyme efficiency.</p> Signup and view all the answers

Explain the relationship between Km and enzyme activity.

<p>Km is the substrate concentration at which an enzyme reaches half its Vmax; allosteric effectors can raise or lower Km, affecting enzyme affinity for substrates.</p> Signup and view all the answers

Why is feedback inhibition considered a common regulatory mechanism in biosynthetic pathways?

<p>Feedback inhibition is common because it prevents overproduction of metabolites, ensuring that pathways are finely tuned to the cell's current needs.</p> Signup and view all the answers

What type of reactions do Class I oxidoreductases catalyze, and provide an example?

<p>Class I oxidoreductases catalyze oxidation-reduction reactions. An example is lactate dehydrogenase.</p> Signup and view all the answers

Define the function of Class II transferases and give an example reaction.

<p>Class II transferases catalyze the transfer of functional groups other than hydrogen. An example is the reaction of ATP with D-hexose to form D-hexose-6-phosphate.</p> Signup and view all the answers

Describe the primary action of Class III hydrolases and provide a specific example.

<p>Class III hydrolases catalyze the hydrolysis of various bonds using water. A specific example is β-galactosidase acting on β-D-galactoside.</p> Signup and view all the answers

What distinguishes Class IV lyases from other enzyme classes, and provide an example?

<p>Class IV lyases catalyze the removal of groups from substrates, forming double bonds without hydrolysis. An example is malate hydro-lyase.</p> Signup and view all the answers

Explain the role of Class V isomerases and illustrate with an example.

<p>Class V isomerases facilitate the interconversion of isomers. An example is triosephosphate isomerase, which converts D-glyceraldehyde-3-phosphate to dihydroxyacetone phosphate.</p> Signup and view all the answers

What reactions do Class VI ligases catalyze, and can you provide a reaction example?

<p>Class VI ligases catalyze the joining of two compounds while breaking a pyrophosphate bond. An example is the formation of L-glutamine from ATP, L-glutamate, and ammonia.</p> Signup and view all the answers

Identify the substrate and products in the reaction catalyzed by hexokinase.

<p>Hexokinase catalyzes the reaction between ATP and D-hexose, producing ADP and D-hexose-6-phosphate.</p> Signup and view all the answers

What types of bonds can Class III hydrolases act upon, and provide a general example?

<p>Class III hydrolases can act on ester, ether, peptido, glycosyl, or other types of bonds using water. A general example is the hydrolysis of glycosidic bonds.</p> Signup and view all the answers

What is the significance of feedback regulation in biosynthetic pathways?

<p>Feedback regulation ensures that enzymes function optimally at the earliest irreversible step in the pathway.</p> Signup and view all the answers

How are plasma enzymes classified according to their origin?

<p>They are classified into enzymes secreted by organs and those released during normal cell turnover.</p> Signup and view all the answers

What causes an increase in plasma levels of intracellular enzymes?

<p>Tissue damage due to diseases results in increased release of intracellular enzymes into the plasma.</p> Signup and view all the answers

In what conditions might plasma lipase levels be low?

<p>Plasma lipase levels may be low in liver disease, Vitamin A deficiency, and certain malignancies.</p> Signup and view all the answers

What is the role of α-amylase in the body?

<p>α-Amylase catalyzes the breakdown of dietary starch and glycogen to maltose.</p> Signup and view all the answers

How are α-amylase levels used diagnostically?

<p>α-Amylase levels are primarily used to diagnose acute pancreatitis.</p> Signup and view all the answers

What can elevated trypsin levels in plasma indicate?

<p>Elevated trypsin levels in plasma may indicate acute pancreatic disease.</p> Signup and view all the answers

What can measurement of enzyme concentrations in plasma reveal?

<p>Measurement of enzyme concentrations can provide valuable information about diseases affecting their tissues of origin.</p> Signup and view all the answers

What specific glycosidic linkage does pancreatic amylase hydrolyze?

<p>Pancreatic amylase hydrolyzes terminal α-(1,4) glycosidic linkages in polysaccharides and oligosaccharides.</p> Signup and view all the answers

What are the products formed when lactose is hydrolyzed by lactase?

<p>Lactose is hydrolyzed to glucose and galactose.</p> Signup and view all the answers

How does lactose intolerance affect adults who lack lactase?

<p>Adults who lack lactase cannot digest lactose, leading to fermentation by bacteria, causing diarrhea and abdominal pain.</p> Signup and view all the answers

What is the pH range for maltase, and what reaction does it catalyze?

<p>Maltase has a pH range of 5.8 to 6.2 and catalyzes the hydrolysis of maltose into two glucose molecules.</p> Signup and view all the answers

What products are formed from the hydrolysis of sucrose by sucrase?

<p>Sucrase hydrolyzes sucrose to form glucose and fructose.</p> Signup and view all the answers

Explain the two mechanisms of carbohydrate absorption mentioned.

<p>Carbohydrate absorption occurs via simple diffusion, dependent on concentration gradients, and active transport, which requires energy.</p> Signup and view all the answers

Why are monosaccharides the only carbohydrates that can be absorbed directly into the bloodstream?

<p>Only monosaccharides are small enough to be absorbed directly into the bloodstream from the intestine.</p> Signup and view all the answers

Which monosaccharide is absorbed faster, fructose or pentoses, and why?

<p>Fructose is absorbed faster than pentoses but slower than glucose and galactose.</p> Signup and view all the answers

Flashcards

Catabolism of Fuel Molecules

The process of breaking down fuel molecules to generate energy in the form of ATP. This energy is then used by the body for various biological processes.

What is free energy?

A measure of the energy available to do work in a chemical reaction. A negative free energy change indicates a reaction that releases energy, while a positive free energy change indicates a reaction that requires energy.

Oxidation Reduction Reactions

Chemical reactions that involve the transfer of electrons between molecules. One molecule loses electrons (oxidation) and the other gains electrons (reduction).

What is Aerobic Energy Generation?

A process that converts food molecules into energy in the presence of oxygen. This involves the Krebs cycle and the electron transport chain.

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What is the Krebs Cycle?

A series of chemical reactions that occur in the mitochondria. It breaks down pyruvate from glycolysis to produce ATP, CO2, and reducing equivalents.

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What is Oxidative Phosphorylation?

The process of transferring electrons down a chain of molecules in the mitochondria, resulting in the generation of ATP. It requires oxygen as the final electron acceptor, and is coupled to the proton gradient across the mitochondrial membrane.

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What is Respiratory Control?

A process where the rate of electron transport and ATP synthesis is regulated by the cell's need for ATP. It's tightly controlled by the availability of ADP, which is a signal that the cell has used up some of its ATP stores.

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What are Uncouplers?

Substances that disrupt the electron transport chain and prevent ATP synthesis by uncoupling oxidative phosphorylation. This results in a loss of energy as heat.

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Enzymes

Biological catalysts that speed up chemical reactions in living organisms.

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Denaturation

The process of breaking down a protein's structure and losing its function. Usually irreversible.

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Monosaccharide

The most basic sugar unit. Examples include glucose and fructose.

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Disaccharide

Two monosaccharides joined together by a glycosidic linkage.

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Polysaccharide

A polymer composed of many monosaccharide units joined together. Examples include starch and cellulose.

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Amino Acids

The building blocks of proteins. They are joined together by peptide bonds.

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Proteins

Large, complex molecules made up of chains of amino acids.

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Tertiary Structure

The specific three-dimensional structure of a protein that determines its function.

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What are Oxidoreductases?

Enzymes catalyzing oxidation-reduction reactions where one molecule loses electrons (oxidation) and another gains electrons (reduction).

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What are Transferases?

Enzymes that transfer functional groups, like methyl, acyl, amino, or phosphate groups, from one molecule to another.

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What are Hydrolases?

Enzymes that break down molecules by adding water, splitting them into smaller components. They act on a variety of bonds, including esters, ethers, peptides, and glycosides.

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What are Lyases?

Enzymes that break down molecules by removing groups without using water, creating double bonds. These reactions often involve removing atoms like carbon, oxygen, nitrogen, sulfur, or halogens.

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What are Isomerases?

Enzymes that catalyze changes within a molecule's structure, including altering its optical, geometric, or positional isomer forms.

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What are Ligases or Synthetases?

Enzymes that join two molecules together, using energy from ATP or similar molecules. This process often forms new bonds like C-O, C-S, C-N, or C-C.

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What is the Enzyme Commission (EC) Number System?

A system used to classify enzymes based on the type of reaction they catalyze. Each enzyme is assigned a four-digit code, with each digit representing a specific category: class, subclass, sub-subclass, and serial number.

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Why is enzyme classification important?

Enzymes are classified based on their catalytic functions, allowing for better understanding and organization of these crucial biological catalysts.

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Lactase

An enzyme that breaks down lactose, a sugar found in milk, into glucose and galactose. Found in the small intestine.

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Lactose Intolerance

A condition where individuals lack the enzyme lactase and cannot digest lactose, leading to digestive discomfort after consuming dairy products.

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Absorption of Carbohydrates

The process of taking in digested nutrients from the small intestine into the bloodstream.

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Simple Diffusion

A simple way for nutrients to move across cell membranes, following the concentration gradient from high to low.

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Active Transport

A process that requires energy to move nutrients across cell membranes, even against the concentration gradient.

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Pancreatic amylase

It hydrolyzes terminal α-(1,4) glycosidic linkages in polysaccharides and oligosaccharides, releasing free glucose molecules.

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Maltase

It hydrolyzes the α-(1,4) glycosidic linkage between glucose units in maltose molecules, releasing two glucose molecules. Its pH range is 5.8 to 6.2.

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Sucrase

It hydrolyzes sucrose into glucose and fructose. Its pH range is 5.0 to 7.0.

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What are proenzymes or zymogens?

Enzymes that exist in an inactive form (proenzyme or zymogen) and require specific changes to become active.

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What is allosteric regulation?

A type of enzyme regulation where a specific molecule binds to the enzyme at a site other than the active site, changing its activity.

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What are allosteric effectors?

Molecules that bind to an allosteric enzyme and modify its activity, either increasing (positive effector) or decreasing (negative effector) it.

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What is feedback inhibition?

The process where the end product of a metabolic pathway inhibits the enzyme that catalyzes the first step of the pathway, preventing further production of the end product.

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How does feedback inhibition work?

A type of allosteric regulation where the end product of a metabolic pathway acts as a negative effector, inhibiting the enzyme that catalyzes the first step of the pathway.

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What is reversible covalent modification?

The irreversible covalent modification of an enzyme by removing or adding a phosphate group, leading to activation or inactivation.

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What is zymogen activation?

The process of converting an inactive proenzyme to an active enzyme through specific hydrolysis of peptide bonds.

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What is zymogen activation?

The process of converting an inactive proenzyme to an active enzyme through specific hydrolysis of peptide bonds.

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Intracellular Enzymes

A group of enzymes normally present within cells, but can be released into blood during tissue damage, reflecting cell turnover.

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Plasma Enzymes

These enzymes are normally secreted by specific organs for a specific function in the blood, like coagulation.

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Enzyme Activity & Tissue Damage

The measurement of specific enzyme activity in the plasma often correlates with the extent of tissue damage. Higher levels mean more damage to the tissue.

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Enzymes as Diagnostic Tools

The level of a specific enzyme in the plasma can be a useful indicator of disease. This is particularly relevant to diseases affecting the heart, liver, muscles, and other tissues.

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Lipase: The Fat Breaker

Lipase, an enzyme involved in fat breakdown, is secreted by the pancreas and liver. Increased lipase levels in the blood may indicate diseases like acute pancreatitis.

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α-Amylase: The Starch Breaker

α-Amylase, the starch and glycogen breakdown enzyme, is found in pancreatic juice, saliva, and other tissues. Elevated amylase levels can indicate conditions like pancreatitis and mumps.

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Trypsin: The Protein Breaker

Trypsin, an enzyme secreted by the pancreas, breaks down proteins. Elevated levels in the blood could indicate acute pancreatic disease or injury.

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Enzymes and Disease Monitoring

Plasma enzyme levels can be used to monitor the progress of a disease, adjust treatment, and assess the effectiveness of therapy.

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Study Notes

Lecture Notes

  • Medical Biochemistry lecture notes for health science students were produced in collaboration with the Ethiopia Public Health Training Initiative, The Carter Center, The Ethiopia Ministry of Health, and the Ethiopia Ministry of Education in 2004.
  • The authors are Solomon Adugna, Lakshmi Ahuja Mekonnen Alemu, Tsehayneh Kelemu, Henok Tekola, Belayhun Kibret, and Solomon Genet.
  • The notes cover topics including Enzymes, Carbohydrate Metabolism, Lipid Metabolism, Amino Acids & Proteins, Vitamins & Coenzymes, Mineral Metabolism, Hormones, and Molecular Genetics.
  • The notes are intended for educational use only by practicing health care workers or students and faculty in a health care field.

Acknowledgements

  • The authors thank the Carter Center (EPHTI) for its financial and logistical support.
  • They also thank the administrations of Gondar University, Debub University, and Jimma University for their cooperation.
  • The authors express gratitude to Ato Akililu Mulugeta and Abdel-Aziz Fatouh Mohammed (Ph.D) and Daniel Seifu for their professional editing and helpful feedback.

Table of Contents

  • The table of contents lists the various topics covered in the lecture notes, including relevant subtitles and page numbers.

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Medical Biochemistry Lecture Notes PDF

Description

Test your knowledge on the vital role of enzymes and proteins in biological processes. This quiz covers topics such as protein formation, carbohydrate classifications, and key metabolic pathways including the Kreb's cycle and ATP production. Perfect for those studying biochemistry or molecular biology!

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