Biochemistry Quiz on Lipid Metabolism

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Questions and Answers

Which condition is characterized by an accumulation of glucocerebrosides due to an enzyme deficiency?

Alcoholic Fatty Liver Disease

Gaucher Disease (correct)

Non-Alcoholic Fatty Liver Disease

Ketoacidosis

What is the effect of a low ATP/ADP ratio on ketogenesis?

Inhibits ketogenesis

Has no effect on ketogenesis

Stimulates ketogenesis (correct)

Promotes glycolysis instead

In which case is high NADH levels favorable for the conversion of acetoacetate?

In a fasting state (correct)

During low-carbohydrate diets

In a high energy state

During prolonged exercise

How is Non-Alcoholic Fatty Liver Disease primarily characterized?

Fat accumulation in the liver unrelated to alcohol Signup and view all the answers

What are the symptoms commonly associated with ketoacidosis?

Nausea, vomiting, abdominal pain, confusion Signup and view all the answers

What type of bond allows water molecules to interact with each other?

Hydrogen bond Signup and view all the answers

What property of water allows for the formation of droplets on smooth surfaces?

Cohesion Signup and view all the answers

Which of the following statements about water's boiling point is true?

It is influenced by the presence of hydrogen bonds. Signup and view all the answers

At 25℃, what is the concentration of H+ in pure water?

$1.0×10^{-7}M$ Signup and view all the answers

What role does water play in temperature regulation?

It absorbs and retains heat effectively. Signup and view all the answers

What does the equilibrium constant (Kw) represent in the context of water?

The relationship between H+ and OH- concentrations Signup and view all the answers

In acidic solutions, which is true regarding the concentrations of H+ and OH-?

[H+] > [OH−] Signup and view all the answers

Which statement best describes how water's polarity influences its role as a solvent?

It can dissolve a wide variety of polar molecules. Signup and view all the answers

What is the main characteristic of water acting as an acid?

It donates protons (H+). Signup and view all the answers

What is the significance of water's high specific heat in biological systems?

It prevents rapid temperature changes. Signup and view all the answers

Which enzyme catalyzes the oxidation of acyl-CoA to trans-Δ²-enoyl-CoA?

Acyl-CoA dehydrogenase Signup and view all the answers

What is produced during the second oxidation step of β-oxidation?

NADH Signup and view all the answers

During the hydration step of β-oxidation, what functional group is added to the β-carbon?

Hydroxyl group Signup and view all the answers

What happens to the hydroxyl group during the second dehydration step?

It is converted to a carbonyl group Signup and view all the answers

What is the primary significance of the thiolysis step in β-oxidation?

It cleaves 3-ketoacyl-CoA, producing acetyl-CoA Signup and view all the answers

Which molecule is the direct substrate for the step involving enoyl-CoA hydratase?

trans-Δ²-enoyl-CoA Signup and view all the answers

What type of reaction occurs when acyl-CoA is acted upon by acyl-CoA dehydrogenase?

Dehydration Signup and view all the answers

What is the ultimate purpose of β-oxidation?

To generate acetyl-CoA for the citric acid cycle Signup and view all the answers

Which of the following reduces FAD to FADH₂ during β-oxidation?

Acyl-CoA dehydrogenase Signup and view all the answers

What is the role of N-acetylglutamate (NAG) in the regulation of the urea cycle?

It activates carbamoyl phosphate synthase I. Signup and view all the answers

Which enzyme is directly responsible for the cleavage of arginosuccinate resulting in arginine and fumarate?

Arginosuccinase Signup and view all the answers

What is the consequence of large quantities of citrulline in the urea cycle?

It prevents excessive urea formation. Signup and view all the answers

What product results from the action of arginase in the final step of the urea cycle?

Urea and Ornithine Signup and view all the answers

Which of the following metabolic derangements is associated with a defect in carbamoyl phosphate synthase I?

Hyperammonemia type I Signup and view all the answers

In the urea cycle, where does ornithine go after it participates in the formation of urea?

It is reused in the urea cycle. Signup and view all the answers

Which type of amino acids can serve as substrates for gluconeogenesis?

Glucogenic amino acids only Signup and view all the answers

Which intermediate can glucogenic amino acids be converted to for entry into gluconeogenesis?

Pyruvate Signup and view all the answers

Which two amino acids are exclusively ketogenic?

Leucine and Lysine Signup and view all the answers

What is a major function of the urea cycle in the body?

To convert toxic NH4+ into harmless urea. Signup and view all the answers

Which of the following processes is a key regulatory step in glycolysis?

Phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate Signup and view all the answers

What is produced as the end product of glycolysis in the presence of oxygen?

Pyruvate Signup and view all the answers

How many ATP molecules are produced per glucose molecule during glycolysis?

2 Signup and view all the answers

Which enzyme is responsible for the initial phosphorylation of glucose in glycolysis?

Hexokinase Signup and view all the answers

What is the primary function of NADPH produced in the pentose phosphate pathway?

Fatty acid synthesis Signup and view all the answers

In glycolysis, which step involves the generation of NADH?

Oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate Signup and view all the answers

Which condition allows glucose-6-phosphate to enter the pentose phosphate pathway?

Low NADPH levels Signup and view all the answers

What is the effect of ATP accumulation on glycolysis?

It inhibits earlier enzymatic steps. Signup and view all the answers

What key product is synthesized during gluconeogenesis?

Glucose Signup and view all the answers

Which disorder is characterized by a deficiency in pyruvate kinase?

Pyruvate kinase deficiency Signup and view all the answers

What is the role of glucose-6-phosphate dehydrogenase in the pentose phosphate pathway?

It produces NADPH. Signup and view all the answers

Which of the following metabolites is an intermediate product of glycolysis?

Glyceraldehyde 3-phosphate Signup and view all the answers

Which enzyme is inhibited by high levels of NADPH?

Glucose-6-phosphate dehydrogenase Signup and view all the answers

What transforms 2-phosphoglycerate into phosphoenolpyruvate during glycolysis?

Dehydration Signup and view all the answers

What is the primary role of ligases in enzymatic reactions?

Joining two molecules through and forming a new chemical bond Signup and view all the answers

Which type of enzyme catalyzes the transfer of phosphate groups?

Transferase Signup and view all the answers

Which enzyme type is specifically responsible for removing hydrogen atoms from substrates?

Dehydrogenase Signup and view all the answers

What distinguishes isomerases from other enzyme classes?

They catalyze rearrangements of atoms within a molecule Signup and view all the answers

Which cofactor plays a crucial role in stabilizing enzyme structures and facilitating electron transfer?

Metal Ion Signup and view all the answers

What is the key characteristic of proenzymes, also known as zymogens?

They are inactive precursors that require activation Signup and view all the answers

Which enzyme type specifically catalyzes the hydrolysis of lipids?

Lipase Signup and view all the answers

Which of the following enzymes is responsible for the joining of RNA fragments?

RNA Ligase Signup and view all the answers

In the context of enzyme kinetics, the term 'kcat' refers to what?

The maximum number of substrate molecules converted per enzyme per second Signup and view all the answers

Which enzyme is responsible for decomposing hydrogen peroxide into water and oxygen?

Catalase Signup and view all the answers

Which group of enzymes can convert one stereoisomer into another, such as converting lactate into its isomer?

Racemase Signup and view all the answers

What role do cofactors play in enzymatic reactions?

They assist enzymes in catalyzing reactions Signup and view all the answers

Which enzyme type is involved in removing carboxyl groups from substrates?

Decarboxylase Signup and view all the answers

What is the significance of isoenzymes in metabolism?

They allow tissues to perform specific functions based on metabolic needs Signup and view all the answers

Study Notes

Final Exam Information

Duration: 2 hours
Exam Type: Closed-book
Calculators: Bring non-programmable calculators from the approved HKMU list
Topics Covered: Lectures 1-11 (primarily lectures 6-11)
Weight: 50% of overall grade

Final Exam Structure

Multiple Choice Questions (20%): 20 questions, each question worth 1 mark
Short Questions (40%): 7 questions, each question worth varying marks
Long Questions (40%): 5 questions, each worth 10 marks; select 4 to answer

Example of Short Questions

Name the metabolite or enzyme from 1 to 6 in the provided diagram of the TCA cycle
Name five important enzymes in oxidative phosphorylation. Give one disorder related to dysfunction of oxidative phosphorylation.
What are the overall products of the TCA cycle? How do these products contribute to energy production?
Describe the four levels of protein structure.

Example of Long Questions

A 45-year-old male presents to the emergency department after several days of severe fasting and significant weight loss. He has a history of type 2 diabetes and reports fatigue, weakness, and confusion. Blood tests reveal elevated ketone levels and a high blood urea nitrogen (BUN) ratio a) Identify two metabolic processes regarding the elevated ketone levels and high blood urea nitrogen in this patient. (2 marks) b) How will the activity of acyl-CoA dehydrogenase change in this patient? Why? (4 marks) c) For patients with type 2 diabetes, insulin levels often become insufficient to manage blood glucose utilization. What is the most likely disorder this patient will develop if his diabetic condition is not well-controlled? Why? (4 marks)

Lecture 1: Water and Aqueous System

Chemical formula: H₂O
Polar molecule: Oxygen has a large nucleus, attracting electrons, resulting in a negative charge; hydrogens are positively charged
Hydrogen bonds: Allow water molecules to interact with each other via attraction between the positive hydrogen and negative oxygen of adjacent molecules
Cohesion: Water molecules stick to each other
Adhesion: Water molecules stick to other substances
High boiling point: Due to hydrogen bonds
High specific heat: More energy to increase the temperature of water (important for temperature regulation and homeostasis)
Solvent for polar molecules: Water's polarity and ability to form hydrogen bonds make it a good solvent for many biochemical reactions

Lecture 2: Carbohydrates, Proteins, and Lipids

Carbohydrates
- Monosaccharides: glucose, galactose, fructose, mannose, ribose and deoxyribose Glucose is the primary energy source for human consumption
- Disaccharides: maltose, cellobiose, sucrose, and lactose
- Oligosaccharides
- Function: Storage and energy production are primary functions Polysaccharides: starch, glycogen, cellulose are important structural components and for energy storage
Proteins
- Amino acids: Classification (polar, nonpolar, charged (basic or acidic)
- Four levels of protein structure: Primary, secondary (alpha helix or beta strands), tertiary, quaternary (multiple subunits).
Lipids
- Phospholipids, glycolipids, fatty acids.

Lecture 3: Nucleic Acids

DNA structure: double helix; made of deoxyribose sugar, phosphate groups, and nitrogenous bases (A, C, G, T)
Adenine (A) pairs with thymine (T); guanine (G) pairs with cytosine (C)
DNA stores genetic information
DNA replication: the process of producing two identical DNA replicas from one original DNA molecule
DNA gives instructions for protein synthesis.
RNA: single-stranded helix; made of ribose sugar, phosphate groups, and nitrogenous bases (A, C, G, U)
Uracil (U) replaces thymine (T) in RNA

Lecture 4: Metabolism and Energy I: Tricarboxylic Acid (TCA) Cycle

Pyruvate oxidation: A key metabolic step linking glycolysis and the TCA cycle.
Converts pyruvate into Acetyl-CoA
Occurs in the mitochondrial matrix
Enables the complete oxidation of glucose
Critical for ATP production and overall cellular metabolism.
Acetyl CoA: plays a role in energy production through the TCA cycle. Sources of acetyl CoA include glucose, fatty acids, and amino acids.
TCA cycle: produces CO2, NADH, FADH2, and GTP/ATP.

Lecture 5: Metabolism and Energy II: Oxidative Phosphorylation

Oxidative Phosphorylation: process of ATP production through the transfer of electrons in the electron transport chain (ETC), creating a proton gradient
Components: ETC (electron carriers, protein complexes, ubiquinone, cytochrome c), chemiosmosis (ATP synthase)
Location: Inner mitochondrial membrane
Protons pumped into the intermembrane space, creating a proton gradient, which drives ATP synthase
ATP synthesis: Uses the proton gradient to generate ATP
Role of Oxygen: The final electron acceptor in the ETC, crucial for processes involving redox reactions

Lecture 6: Carbohydrate Metabolism : Glycolysis

Glycolysis: pathway for glucose breakdown to produce ATP
Occurs primarily in the cytoplasm
Two phases: preparatory and payoff
Preparatory phase: Glucose is phosphorylated and arranged into two 3-carbon molecules
Payoff phase: Energy is extracted from these 3-carbon molecules in the form of ATP and NADH.
NADH, a crucial coenzyme, participates in electron transfer during this phase

Lecture 7: Protein and Lipid Metabolism

Protein Metabolism: Transamination: Amino groups are moved from amino acids to keto acids Oxidative deamination: Deamination of amino acids, generating ammonia Urea cycle: Ammonia is converted into urea, a less toxic substance excreted in urine.
Lipid Metabolism: Beta-oxidation: Fatty acids are broken down to produce acetyl-CoA, an important entry point for energy production Fatty acid activation, transport across the mitochondrial membrane, and the four main steps (oxidation, hydration, oxidation, thiolysis) of beta oxidation

Lecture 8: Hemoglobin

Hemoglobin: Globular protein in red blood cells.
Transport oxygen throughout the body.
Basic Components: Globin chains (alpha and beta), heme group (iron atom within a porphyrin ring), iron atom (Fe)
Oxygen transport: binds oxygen in the lungs, transports it to tissues.
Carbon dioxide transport: also transports carbon dioxide.
pH regulation: Hemoglobin acts as a buffer, helping maintain appropriate pH

Lecture 9: Enzyme I: Introduction to Enzymes

Enzymes: Biological catalysts
Protein-based molecules that accelerate chemical reactions
Mechanism of enzyme action: substrate binding, induced fit, catalysis, and product release.

Lectures 10-11: Enzyme Kinetics and Inhibitors and Enzyme Diagnostics & Assay

Enzyme Kinetics:
- Michaelis-Menten equation, describing reaction velocity to substrate concentration.
- Turnover number.
Enzyme Inhibitors:
- Reversible inhibitors (competitive, uncompetitive, non-competitive) and Irreversible inhibitors.
Enzyme Diagnostics & Assay:
- Liver enzymes (ALT, AST, GGT, ALP)
- Cardiac enzymes (CK-MB, troponin I, troponin T, myoglobin)
- Pancreatic enzymes (amylase, lipase, proteases, carboxypeptidase, elastase)
- Cancer-associated enzymes (PSA, ALP, LDH, CEA)

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Description

Test your knowledge on important biochemistry concepts related to lipid metabolism. This quiz covers enzyme deficiencies, the effects of ATP ratios, and key symptoms associated with metabolic disorders. Challenge yourself and see how well you understand these critical biochemical processes.