Metabolism Overview: Catabolism & Anabolism

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Questions and Answers

What is metabolism primarily defined as?

A series of oxidizing reactions

A process of energy acquisition and transformation (correct)

The breakdown of cellular components only

The storage of proteins and fats exclusively

Which of the following describes catabolism?

Building complex molecules from smaller units

A breakdown process that releases energy (correct)

Summation of all cellular reactions

The process of energy consumption only

Which of these macronutrients provides the highest caloric energy per gram?

Proteins

Fats (correct)

Carbohydrates

Sugars

In which phase of metabolism are large molecules constructed from smaller ones?

Anabolism Signup and view all the answers

Which enzyme is primarily responsible for the initial digestion of carbohydrates in the mouth?

Salivary amylase Signup and view all the answers

What is the percentage range of carbohydrates in the average Filipino diet?

55 – 65% Signup and view all the answers

Which product is NOT typically produced during carbohydrate digestion?

Amino acids Signup and view all the answers

What type of bonds does α-amylase cleave in amylopectin during carbohydrate digestion?

α1→6 and α1→4 bonds Signup and view all the answers

What is the primary end product of glycolysis under aerobic conditions?

Pyruvate Signup and view all the answers

Which of the following statements about ATP is true?

ATP serves as the primary energy currency of the cell. Signup and view all the answers

What is one main feature of glycolysis?

It can function in both aerobic and anaerobic conditions. Signup and view all the answers

Which metabolic process involves the conversion of pyruvate to acetyl CoA?

Glycolysis Signup and view all the answers

What process synthesizes glucose from non-carbohydrate sources?

Gluconeogenesis Signup and view all the answers

Which molecule can enter the electron transport chain and yield 3 ATP?

NADH Signup and view all the answers

Which of the following substrates is not considered a major substrate for gluconeogenesis?

Glucose-6-phosphate Signup and view all the answers

What is the final step in the Kreb’s Cycle concerning the oxidized acetyl moiety?

Reduction of coenzymes Signup and view all the answers

What is the primary reason the body needs gluconeogenesis?

To respond to glucose needs when carbohydrates are insufficient Signup and view all the answers

Which of the following is a consequence of low blood glucose levels?

Potential brain malfunction leading to coma Signup and view all the answers

What is not a role of glucose in the body?

It acts as a direct precursor for amino acids Signup and view all the answers

Which process converts lactate back to glucose in the liver during anaerobic conditions?

Cori cycle Signup and view all the answers

Which special reaction is not part of gluconeogenesis?

Pyruvate to Glycerol Signup and view all the answers

What is the main storage form of glucose in the body?

Glycogen Signup and view all the answers

How much glycogen is approximately stored in a 70kg adult’s skeletal muscles?

260g Signup and view all the answers

Which process primarily uses glucose to regenerate energy during low oxygen conditions in muscles?

Anaerobic glycolysis Signup and view all the answers

What is the primary function of glycogenesis?

To synthesize glycogen from glucose Signup and view all the answers

Which enzyme is responsible for glycogen synthesis?

Glycogen synthase Signup and view all the answers

What role does glucagon play in glycogen metabolism?

Stimulates breakdown of glycogen Signup and view all the answers

What effect does insulin have on glycogen metabolism?

Inhibits glycogen breakdown Signup and view all the answers

Which hormone is primarily associated with the fight or flight response?

Adrenaline Signup and view all the answers

Where is glycogen primarily stored in the body?

Liver and muscles Signup and view all the answers

What processes are stimulated by adrenaline in relation to glycogen?

Glycogen breakdown and glucose release Signup and view all the answers

What is the effect of glucagon in relation to glycogen synthesis?

Inhibits glycogen synthesis Signup and view all the answers

Study Notes

Metabolism

The sum of all enzymatic reactions occurring in biological systems
Involves energy transformation including acquisition, transformation, use, and storage within a cell

Phases of Metabolism

Catabolism: The breakdown of large complex molecules into smaller molecules
- Often accompanied by energy release (energy-producing process)
- Examples: Breakdown of carbohydrates, proteins, and fats into carbon dioxide, water, ammonia, and urea.
Anabolism: The building up of large complex organic molecules from smaller molecules
- Requires an input of energy (energy-consuming process)
- Examples: Synthesis of carbohydrates, proteins, and fats from pyruvate, glucose, and carbon dioxide.

Sources of Caloric Energy

Carbohydrates: 1 gram provides 4 kilocalories (kcal)
Fats: 1 gram provides 9 kcal
Protein: 1 gram provides 4 kcal
Average Filipino Diet: Typically consists of 55-65% carbohydrates, 15-20% fats, and 5-15% protein.

Digestion of Carbohydrates

Early Digestion: Involves the intake of dietary carbohydrates and the action of salivary amylase.
Luminal Digestion: Combines the roles of the stomach, pancreas, and intestine. Primarily involves pancreatic alpha-amylase, which breaks down amylopectin into various products, including maltose, glucose, and alpha-limit dextrin.
Brush Border Digestion: Involves disaccharidases and oligosaccharidases located on the brush border of the small intestine, further breaking down disaccharides and oligosaccharides into monosaccharides for absorption.

Carbohydrate Metabolism

Focuses on the provision and fate of glucose (blood sugar, dextrose).
One major pathway for utilizing glucose is Glycolysis.

Glycolysis

Occurs in the cytosol of all cells.
Can function both aerobically (with oxygen) and anaerobically (without oxygen).
Aerobic glycolysis produces pyruvate as the end product.
Anaerobic glycolysis produces lactate as the end product.

ATP

Stands for adenosine triphosphate.
Composed of adenine (nitrogenous base), ribose (5-carbon sugar), and a phosphate group.

Role of ATP

Food and oxygen react chemically to produce energy (cellular respiration).
Energy produced during cellular respiration is trapped in ATP molecules.
ATP supplies the energy needed for all cell activities.

ATP Production

Oxidative Phosphorylation: Production of ATP through redox reactions in mitochondria via the Electron Transport Chain (ETC).
- 1 mole of NADH produces 3 ATP molecules.
- 1 mole of FADH2 produces 2 ATP molecules.
Substrate Level Phosphorylation: Production of ATP at the substrate level.

Kreb's Cycle (Citric Acid Cycle)

A sequence of reactions occurring in mitochondria.
Oxidizes the acetyl moiety of acetyl-CoA.
Reduces coenzymes that are reoxidized through the ETC.
The final common pathway for the oxidation of carbohydrates, lipids, and proteins.
Acetyl-CoA is derived from pyruvate, produced during aerobic glycolysis.

Gluconeogenesis

The synthesis of glucose from non-carbohydrate sources.
Major substrates include glucogenic amino acids, lactate, glycerol, and propionate.
Major tissues involved are liver and kidney.

Biomedical Importance of Gluconeogenesis

Supplies glucose when dietary carbohydrate intake is insufficient.
Essential for the nervous system and red blood cells.
Brain's primary fuel, prevents malfunction, coma, and death.
Provides glyceride in adipose tissue for fat synthesis.
Maintains intermediates of the Kreb's cycle in various tissues.
Only fuel that provides energy to skeletal muscles under anaerobic conditions.
Precursor of lactose in the mammary gland and is actively taken up by the fetus.

Cori Cycle

When anaerobic conditions occur in active muscles, glycolysis produces lactate.
Lactate enters the bloodstream and travels to the liver, where it's oxidized back to pyruvate.
Gluconeogenesis converts pyruvate to glucose, which is then transported back to the muscles.
Represents the flow of lactate and glucose between the muscles and the liver.

Glycogen Metabolism

Glycogen: The human storage glucan polysaccharide.
Glycogen Storage: 80g in the liver and 260g in skeletal muscles of a 70kg adult.
Hepatic Glycogen: Maintains blood glucose concentration, especially between meals.
Muscle Glycogen: Serves as an energy reserve for muscle activity.
Glycogen Structure: Branched chains of alpha-1,4-linked glucose residues with alpha-1,6 linkages at branch points.

Glycogenesis

Synthesis of glycogen from glucose.
Carried out by glycogen synthase.
Occurs when there's excess glucose in the body, helping to regulate blood glucose.
Stored primarily in the liver and muscles.

Glycogenolysis

The breakdown of glycogen to glucose.
Carried out by glycogen phosphorylase.
Released glucose enters the bloodstream, supplying energy to various tissues.

Regulation of Glycogen Metabolism

Glucagon, Insulin, and Adrenaline: Major hormonal regulators.
Glucagon: Stimulates glycogen breakdown, releasing glucose into the blood.
Insulin: Reverses the effects of glucagon, stimulating glycogen synthesis and glycolysis, and inhibiting gluconeogenesis.
Adrenaline: Stimulates glycogen breakdown into glucose, releasing glucose into the bloodstream.

Flight or Fight Response

Body's reaction to perceived threat or danger.
Releases hormones like adrenaline and cortisol, increasing heart rate, slowing digestion, diverting blood flow, and providing a burst of energy and strength.

Pathways for Glucose

Glucose can be used for energy production through glycolysis.
Glucose can be stored as glycogen for later use.
Glucose can be converted into other molecules, such as fatty acids and amino acids.
Glucose can be released from the liver to maintain blood glucose levels between meals.

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Description

Explore the essential concepts of metabolism, including the phases of catabolism and anabolism in biological systems. Learn how energy is transformed and used through the breakdown of complex molecules and the building of macromolecules. This quiz will also cover the sources of caloric energy from carbohydrates, fats, and proteins.