Lipid Metabolism Quiz
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Questions and Answers

What is the primary action of phospholipase A2?

  • Hydrolysis of phospholipids (correct)
  • Formation of micelles
  • Hydrolysis of carbohydrates
  • Production of toxins

Which organism's venom contains phospholipase D that causes tissue damage?

  • Spiders (correct)
  • Frogs
  • Snakes
  • Scorpions

What effect do the lipid products of hydrolysis by phospholipases in snake venoms have on victims?

  • Enhance blood clot formation
  • Neutralize small peptides
  • Increase venom toxicity
  • Lysis of red blood cells (correct)

In snake venoms with low concentrations of toxins, what is typically high?

<p>Phospholipase concentration (D)</p> Signup and view all the answers

What is a potential consequence of a bite from a snake with high phospholipase levels?

<p>Bleeding to death (C)</p> Signup and view all the answers

What is the role of ATP in the formation of acyl-CoA?

<p>It is converted into AMP during the reaction. (A)</p> Signup and view all the answers

In the first step of the reaction, what is formed alongside the acyl adenylate intermediate?

<p>AMP (B)</p> Signup and view all the answers

What is produced in the overall reaction aside from acyl-CoA?

<p>PPi (B)</p> Signup and view all the answers

Which component is crucial for the thioester formation in the reaction?

<p>CoA-SH (C)</p> Signup and view all the answers

What type of reaction is involved in the conversion of acyl adenylate to acyl-CoA?

<p>Thioesterification (B)</p> Signup and view all the answers

How many moles of ATP are generated from the complete oxidation of one mole of stearic acid?

<p>1120 (D)</p> Signup and view all the answers

What is the equivalent of ATP that must be subtracted during the activation step of stearic acid?

<p>Two ATP (D)</p> Signup and view all the answers

How many FADH2 molecules are produced from the β-oxidation of stearic acid?

<p>19 (C)</p> Signup and view all the answers

What happens to the molecules of NADH and FADH2 in the oxidation of stearic acid?

<p>There is no net change. (A)</p> Signup and view all the answers

How many moles of acetyl-CoA are produced from the β-oxidation of one mole of stearic acid?

<p>9 (A)</p> Signup and view all the answers

In the citric acid cycle, how many GTP molecules are formed from the oxidation of 9 acetyl-CoA?

<p>9 (D)</p> Signup and view all the answers

What is the total number of NADH molecules generated from the citric acid cycle for the complete oxidation of stearic acid?

<p>227 (D)</p> Signup and view all the answers

Which reaction step contributes the least to the total ATP yield from stearic acid oxidation?

<p>Activation step of stearic acid (B)</p> Signup and view all the answers

Where does the esterification of fatty acids primarily take place?

<p>Cytosol (C)</p> Signup and view all the answers

What is the primary site of action for phospholipase A2?

<p>B site (A)</p> Signup and view all the answers

What activates triacylglycerol lipase in adipose tissue?

<p>cAMP production (A)</p> Signup and view all the answers

Which fatty acids can serve as substrates for phosphoacylglycerol enzymes?

<p>Both saturated and unsaturated fatty acids (C)</p> Signup and view all the answers

What must happen for the oxidation process of fatty acids to proceed?

<p>Fatty acids must be transported into the mitochondrion (B)</p> Signup and view all the answers

Which enzyme is NOT named after its historical accident?

<p>Phospholipase C (A)</p> Signup and view all the answers

Which component is NOT involved in the liberation of fatty acids from triacylglycerols?

<p>Glycogen synthase (C)</p> Signup and view all the answers

Which type of fatty acids do phospholipases specifically target?

<p>Both long-chain and short-chain fatty acids (A)</p> Signup and view all the answers

What is released as a result of the action of triacylglycerol lipase?

<p>Both glycerol and fatty acids (D)</p> Signup and view all the answers

Which of the following enzymes has a historical naming origin?

<p>Phospholipase A2 (C)</p> Signup and view all the answers

How many moles of ATP can be obtained from the complete oxidation of one mole of glucose?

<p>32 moles (D)</p> Signup and view all the answers

Why do fatty acids yield more ATP than carbohydrates for the same number of carbon atoms?

<p>Fatty acids are less oxidized compared to carbohydrates. (A)</p> Signup and view all the answers

What is a significant characteristic of the metabolic water produced during the oxidation of nutrients?

<p>It can be a primary water source for desert animals. (D)</p> Signup and view all the answers

What adaptation allows kangaroo rats to thrive in desert environments?

<p>They metabolize fat to produce sufficient water. (D)</p> Signup and view all the answers

In comparison to glucose, how many ATP molecules are produced from three glucose molecules?

<p>96 ATP molecules (C)</p> Signup and view all the answers

What role does metabolic water play for camels during desert trips?

<p>It provides hydration during long periods without water. (D)</p> Signup and view all the answers

What product is formed during the aerobic oxidation of both fatty acids and carbohydrates?

<p>Both carbon dioxide and metabolic water (D)</p> Signup and view all the answers

Which of the following statements is true regarding the oxidation of fatty acids?

<p>It leads to the production of metabolic water. (A)</p> Signup and view all the answers

What is produced when citrate is exported to the cytosol?

<p>Oxaloacetate and Acetyl-CoA (A)</p> Signup and view all the answers

What role does NADPH play in fatty acid biosynthesis?

<p>It substitutes for NADH in the biosynthesis pathway. (C)</p> Signup and view all the answers

What is the first product formed during the carboxylation of acetyl-CoA?

<p>Malonyl-CoA (A)</p> Signup and view all the answers

Which enzyme complex catalyzes the production of malonyl-CoA from acetyl-CoA?

<p>Acetyl-CoA carboxylase complex (B)</p> Signup and view all the answers

What key components are required for the activity of acetyl-CoA carboxylase?

<p>Mn2+, Biotin, and ATP (A)</p> Signup and view all the answers

Which of the following statements about biotin in the enzyme complex is true?

<p>Biotin is bound to the biotin carrier protein via an amide linkage. (A)</p> Signup and view all the answers

What does the carboxylation of acetyl-CoA directly produce?

<p>Malonyl-CoA (D)</p> Signup and view all the answers

Which of the following enzymes does NOT form part of the acetyl-CoA carboxylase complex?

<p>NADH dehydrogenase (A)</p> Signup and view all the answers

Flashcards

Stearic Acid Oxidation

The complete breakdown of a stearic acid molecule to produce ATP.

Activation Step (Stearic acid)

Conversion of stearic acid to stearyl-CoA, requiring 2 ATP molecules.

Beta-oxidation

A metabolic process that breaks down fatty acid chains into acetyl-CoA molecules.

Acetyl-CoA

A molecule produced during fatty acid oxidation, a crucial intermediate in energy production.

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Citric Acid Cycle

A series of enzymatic reactions that completely oxidizes acetyl-CoA.

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NADH and FADH2

Electron carriers produced during fatty acid oxidation and the citric acid cycle, crucial for ATP production.

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ATP Production (Stearic Acid)

The theoretical net yield of ATP after complete oxidation of one stearic acid molecule is 120.

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Theoretical ATP Yield

Calculations of ATP based on complete oxidation of fatty acids, but may vary in real-world cells.

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Phospholipase A2

An enzyme that hydrolyzes phospholipids at micelle surfaces.

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Phospholipase D

Enzyme found in spider venom, causing tissue damage.

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Snake Venom Phospholipases

Venom containing high phospholipase concentration, low toxin concentration.

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Lipid Hydrolysis Effects

Lipid breakdown products lyse red blood cells, hindering clotting.

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Snakebite Outcome

Snakebite victims can bleed to death due to disrupted clotting.

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Fatty Acid Oxidation

Metabolic process breaking down fatty acids for energy.

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Phospholipases

Enzymes that hydrolyze phosphoacylglycerols.

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Fatty Acid Activation

Converting a fatty acid to a form usable in mitochondria.

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Mitochondrial Matrix

Location of the later stages of fatty acid oxidation.

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Hormone-Dependent Activation

Triacylglycerol breakdown in adipose tissue regulated by hormones.

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Triacylglycerol

Storage form of fatty acids in adipose tissue.

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Adenylate Cyclase

Enzyme activating other proteins involving fatty acid release.

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Protein Kinase

Enzyme that activates other molecules via phosphorylation.

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Cytosol

Site of early fatty acid activation steps.

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Fatty acid transport

Movement of activated fatty acids into the mitochondria.

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Acyl-CoA Synthesis

The process of attaching a fatty acid to CoA, making it reactive for further metabolism.

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Acyl-Adenylate

A high-energy intermediate in fatty acid activation, formed from ATP and fatty acid.

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CoA-SH

Coenzyme A, a molecule crucial for carrying activated acyl groups.

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Acyl-CoA Synthetase

The enzyme that catalyzes the formation of Acyl-CoA.

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Fatty Acid Activation

The initial step which prepares fatty acids for metabolism, requiring ATP

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Fatty Acid Oxidation

The process of breaking down fatty acids to produce energy, yielding more ATP than carbohydrates per carbon atom.

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ATP Yield (Fatty Acids)

Fatty acid oxidation produces significantly more ATP than the oxidation of an equal number of carbon atoms in glucose.

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Reduced State of Fatty Acids

Fatty acids are in a highly reduced state, meaning they have more potential for further oxidation.

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Metabolic Water Production

Water produced as a byproduct of aerobic respiration (including fatty acid oxidation); vital in arid environments.

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Camel Adaptation

Camels store lipids to use for energy and water during long desert journeys.

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Kangaroo Rat Example

Kangaroo rats live off a lipid-rich diet and produce sufficient metabolic water to survive without drinking.

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Aerobic Metabolism

Metabolic processes that require oxygen, such as the complete oxidation of fatty acids, carbohydrates, etc.

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Reduced Electron Carriers

In fatty acid oxidation, the reduced state enables further oxidation and more energy production.

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Acetyl-CoA Carboxylase

Enzyme complex that adds a carboxyl group to acetyl-CoA, forming malonyl-CoA.

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Malonyl-CoA

Important intermediate in fatty acid biosynthesis, formed by carboxylating acetyl-CoA.

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Fatty Acid Biosynthesis

Metabolic pathway that synthesizes fatty acids from acetyl-CoA.

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Citrate Export

Citrate leaving the mitochondria to the cytosol for fatty acid biosynthesis.

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Oxaloacetate

Intermediate in the citric acid cycle; is a byproduct of citrate export.

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NADPH

Electron carrier used in fatty acid biosynthesis, replaces NADH.

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Biotin

Cofactor essential for acetyl-CoA carboxylase activity.

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Acetyl-CoA Carboxylase Complex

Multi-enzyme complex catalyzing the carboxylation of acetyl-CoA to malonyl-CoA.

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Study Notes

Lipid Metabolism

  • Lipids are involved in energy generation and storage.
  • Carbohydrate polymers (starch, glycogen) store energy, which can be broken down for energy.
  • Lipid oxidation (fatty acid oxidation) releases large amounts of energy, producing acetyl-CoA, NADH, and FADH2.
  • Triacylglycerols and phosphoacylglycerols are important lipid storage forms.
  • Lipases and phospholipases hydrolyze lipids.
  • Fatty acid activation involves a thioester bond between a fatty acid and CoA. This requires ATP.
  • Activated fatty acids (acyl-CoA) enter the mitochondrial matrix for oxidation.
  • Acyl-CoA can’t cross the inner mitochondrial membrane, so carnitine shuttles acyl groups across the inner membrane.
  • Fatty acid oxidation (β-oxidation) is a cyclic process that cleaves 2-carbon units from fatty acids, producing acetyl-CoA. Each cycle yields FADHâ‚‚ and NADH.
  • Even-numbered fatty acids yield acetyl-CoA, whereas odd-numbered fatty acids yield propionyl-CoA (which needs a separate pathway to enter the citric acid cycle).
  • Monounsaturated fatty acids require isomerization for complete β-oxidation.
  • Polyunsaturated fatty acids require additional enzymes to handle multiple double bonds.

Ketone Bodies

  • Ketone bodies are produced when excess acetyl-CoA from β-oxidation cannot enter the citric acid cycle.
  • This happens in conditions like starvation or uncontrolled diabetes.
  • Ketone bodies include acetoacetate, β-hydroxybutyrate, and acetone.
  • Ketone bodies are an alternative energy source for tissues like the brain and heart.
  • Excessive ketone bodies can cause ketosis and ketoacidosis (low blood pH).

Fatty Acid Biosynthesis

  • Fatty acid biosynthesis occurs in the cytosol, not in the mitochondrial matrix.
  • Acetyl-CoA is transported from the mitochondria to the cytosol as citrate.
  • Acetyl-CoA carboxylation, producing malonyl-CoA, is a key step in fatty acid synthesis. This step is catalyzed by acetyl-CoA carboxylase.
  • Fatty acid synthase is a complex enzyme carrying out the successive addition of two carbon units to the fatty acid chain.
  • Acetyl-CoA to acyl carrier protein and then malonyl-CoA to ACP.
  • Repeated cycles of condensation, reduction, dehydration, and reduction reactions produce progressively longer fatty acid chains.
  • The process terminates when a sixteen-carbon saturated fatty acid (palmitate) is synthesized.

Cholesterol Biosynthesis

  • Cholesterol is synthesized from acetyl-CoA.
  • Three acetyl units condense to form mevalonate.
  • Mevalonate is converted to isoprene units, and then to squalene.
  • Squalene is converted to lanosterol, and then to cholesterol.
  • HMG-CoA reductase is a key enzyme in cholesterol biosynthesis; it's often a drug target.
  • Cholesterol is a precursor for other steroids (bile acids, steroid hormones).
  • Cholesterol is transported in the blood by lipoproteins (LDL, HDL).
  • High levels of LDL cholesterol contribute to atherosclerosis (plaque formation in arteries).

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Biochemistry 9e - Lipids & Metabolism - Campbell PDF

Description

Test your knowledge on lipid metabolism, including the roles of lipids in energy generation and storage. This quiz covers key processes such as fatty acid oxidation, the function of triacylglycerols, and the importance of acyl-CoA in mitochondrial metabolism.

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