Metabolism
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Questions and Answers

What triggers the release of insulin from pancreatic beta cells?

  • Release of glucagon from alpha cells
  • Increase in blood glucose concentrations (correct)
  • Decrease in peripheral tissue glucose levels
  • Absence of food in the digestive system

During the post-absorptive state, which of the following functions does glucagon primarily serve?

  • Enhance insulin release
  • Stimulate glycogen breakdown (correct)
  • Stimulate glycogen synthesis
  • Inhibit gluconeogenesis

In starvation mode, which is the first priority for the body?

  • Preservation of muscle mass
  • Provision of glucose for the brain (correct)
  • Regulation of body temperature
  • Utilization of fat stores for energy

What mechanism of heat exchange involves the direct transfer of heat between objects in contact?

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

How many nutritional calories (kcal) are needed to raise the temperature of 1kg of water by 1 degree Celsius?

<p>1000 (C)</p> Signup and view all the answers

Which metabolic pathway is responsible for the production of ATP during the breakdown of glucose?

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

What is the primary purpose of gluconeogenesis in the body?

<p>To synthesize glucose from non-carbohydrate sources (A)</p> Signup and view all the answers

Which of the following statements about catabolic reactions is true?

<p>They break down organic molecules to release energy. (A)</p> Signup and view all the answers

What percentage of energy from catabolic reactions is typically converted into ATP?

<p>40% (C)</p> Signup and view all the answers

Which of the following molecules serves as the immediate energy source for cellular functions?

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

What occurs when the net energy balance in the body is negative?

<p>The body utilizes energy stores for fuel. (D)</p> Signup and view all the answers

What is the primary function of the urea cycle?

<p>To eliminate excess nitrogen from amino acids (A)</p> Signup and view all the answers

Which of the following best describes lipogenesis?

<p>The conversion of excess carbohydrate to fats (B)</p> Signup and view all the answers

Which process begins with the oxidation of glucose and results in the production of pyruvate?

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

What is the primary role of NAD+ and FAD in cellular respiration?

<p>Accept hydrogen atoms (C)</p> Signup and view all the answers

During anaerobic respiration, pyruvate can be converted into which of the following?

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

Which of the following accurately describes the output of the Krebs cycle for one molecule of glucose?

<p>2 ATP, 1 FADH2, 3 NADH (A)</p> Signup and view all the answers

What is produced during glycolysis from one molecule of glucose?

<p>2 pyruvate and 2 NADH (C)</p> Signup and view all the answers

In the electron transport chain, what is the primary function of the high-energy electrons carried by NADH and FADH2?

<p>Pump protons to create a gradient (D)</p> Signup and view all the answers

When glucose is metabolized under anaerobic conditions, what is the role of NADH?

<p>To regenerate NAD+ (C)</p> Signup and view all the answers

What is the final waste product released during aerobic respiration?

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

What is the energy yield from one glucose molecule during aerobic respiration?

<p>36 to 38 ATP (C)</p> Signup and view all the answers

Which component initiates the Krebs cycle by combining with acetyl CoA?

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

What is the primary end product of the electron transport chain from one glucose molecule?

<p>32-34 ATP molecules (D)</p> Signup and view all the answers

Which component is essential for the production of ATP from ADP during the flow of protons back into the mitochondria?

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

Which hormone stimulates the release of pancreatic lipase and the gall bladder concentration?

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

How does gluconeogenesis primarily use lactate, glycerol, and amino acids?

<p>To synthesize new glucose molecules (C)</p> Signup and view all the answers

Which process describes the breakdown of fatty acids to produce energy?

<p>Beta-oxidation (B)</p> Signup and view all the answers

What occurs when there is excess acetyl CoA in the liver beyond what can be processed by the Krebs cycle?

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

What is the main purpose of the urea cycle?

<p>To excrete nitrogenous waste (A)</p> Signup and view all the answers

During lipid digestion, which compounds are transported by chylomicrons?

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

What process converts ammonia into urea?

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

Which energy-producing process occurs primarily in the liver during periods of low glucose availability?

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

What is primarily the role of amino acids during starvation?

<p>To provide energy leading to potential body deterioration (C)</p> Signup and view all the answers

What metabolic process involves the breakdown of triglycerides for energy?

<p>Beta-oxidation (C)</p> Signup and view all the answers

Which hormone is responsible for increasing blood glucose levels by stimulating gluconeogenesis?

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

What consequence does phenylketonuria (PKU) have on newborns if not detected?

<p>Developmental defects due to high phenylalanine levels (D)</p> Signup and view all the answers

How does insulin primarily affect carbohydrate metabolism?

<p>Promotes glucose uptake and storage in cells (B)</p> Signup and view all the answers

What is a primary characteristic of Cushing syndrome?

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

What does the pyruvate dehydrogenase complex enzyme convert pyruvate into?

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

Which hormone primarily stimulates growth and development of tissues and muscles?

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

What is a treatment for Addison's disease?

<p>Cortisol replacement therapy (C)</p> Signup and view all the answers

What metabolic outcomes can result from malfunctioning enzymes?

<p>Metabolic diseases leading to various manifestations (D)</p> Signup and view all the answers

Flashcards

Cellular Respiration

The process of breaking down glucose in the presence of oxygen to produce energy (ATP).

Glycolysis

The first stage of cellular respiration, where glucose is broken down into pyruvate. This occurs in the cytoplasm.

Krebs Cycle

The second stage of cellular respiration, where pyruvate is further broken down to release energy in the form of ATP and electron carriers. Occurs in the mitochondria.

Electron Transport Chain

The final stage of cellular respiration, where electrons from the Krebs cycle are used to produce ATP. Occurs in the mitochondria.

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Anaerobic Respiration

The process of breaking down glucose without oxygen. Produces lactic acid as a byproduct.

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Catabolic Reactions

Chemical reactions that break down larger molecules into smaller ones, releasing energy.

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Anabolic Reactions

Chemical reactions that build up larger molecules from smaller ones, requiring energy.

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ATP

Adenosine triphosphate, a molecule that serves as the primary energy currency of cells.

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Sugar Catabolism

The process of breaking down polysaccharides into their simpler units, monosaccharides. This is the first step in extracting energy from carbohydrates.

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Glucose

The primary fuel source for cells to generate energy (ATP). It's the product of sugar catabolism and is readily used by cells for various processes.

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Glycogen

A storage form of glucose in the liver and muscles. It's a readily accessible energy reserve that can be broken down back into glucose when needed.

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Triglycerides

The primary form of stored fat in the body. They are made up of glycerol and fatty acids, and serve as a long-term energy reserve.

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Beta-oxidation

The metabolic process that breaks down triglycerides (fats) into usable energy (ATP). It releases fatty acids from the glycerol backbone.

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Catabolic Hormones

Hormones that stimulate the breakdown of molecules, releasing energy. They help regulate metabolism during times of stress or energy depletion.

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Anabolic Hormones

Hormones that promote the synthesis of new molecules, essential for growth and development.

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Cushing Syndrome

A disorder caused by excessive cortisol production, leading to weight gain, muscle weakness, and other metabolic abnormalities.

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Addison's Disease

A disorder caused by insufficient cortisol production, leading to fatigue, low blood pressure, and other metabolic disturbances.

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Insulin's Role

Insulin, released by pancreatic beta cells, helps absorb glucose from the bloodstream into liver, adipose, and muscle cells.

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Glucagon's Role

Glucagon, released from the alpha cells of the pancreas, breaks down stored glycogen in the liver into glucose when blood sugar is low.

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Thermoregulation

The process of maintaining a stable body temperature.

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Conduction

Heat transfer through direct contact between two objects.

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Calorie vs. Nutritional Calorie

A calorie is the energy needed to raise 1g of water by 1°C, while a nutritional calorie (kcal) raises 1kg of water by 1°C, representing the energy in food.

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What is phenylalanine?

Phenylalanine is an amino acid that is essential for human growth and development. In people with phenylketonuria (PKU), the body cannot break down phenylalanine properly, leading to a buildup in the blood.

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What is the role of redox reactions in cellular metabolism?

Redox reactions involve the transfer of electrons between molecules. In cellular metabolism, they are essential for energy production, as they allow for the release and transfer of energy stored in chemical bonds.

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What are coenzymes and their role in redox reactions?

Coenzymes are non-protein molecules that assist enzymes in catalyzing reactions. In redox reactions, they act as carriers of electrons and hydrogen atoms, facilitating the transfer of energy.

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What is ATP and its function?

ATP (adenosine triphosphate) is the primary energy currency of the cell. It is a molecule that stores and releases energy through the breaking and forming of phosphate bonds.

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What is glycolysis and its end products?

Glycolysis is the first step in cellular respiration, where glucose is broken down into pyruvate, releasing energy in the process.

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What is anaerobic respiration and its purpose?

Anaerobic respiration occurs when oxygen is limited. It allows cells to produce a small amount of ATP by converting pyruvate into lactic acid or alcohol.

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What is the Krebs cycle and its role in cellular respiration?

The Krebs cycle is a series of reactions that take place in the mitochondria, where pyruvate is further broken down, releasing electrons and carbon dioxide.

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What is the electron transport chain and its function?

The electron transport chain is the final stage of cellular respiration, where electrons from NADH and FADH2 are used to generate ATP through a series of protein complexes.

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What is the difference between aerobic and anaerobic respiration?

Aerobic respiration requires oxygen and produces much more ATP than anaerobic respiration. Anaerobic respiration occurs when oxygen is limited and produces a small amount of ATP.

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What is the relationship between pyruvate, acetyl CoA, and the Krebs cycle?

Pyruvate, the end product of glycolysis, enters the mitochondria where it is converted into acetyl CoA, a 2-carbon molecule that enters the Krebs cycle.

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Oxidative Phosphorylation

The process of generating ATP through the electron transport chain and the subsequent movement of protons across the mitochondrial membrane. It's the primary method of ATP production in aerobic organisms.

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Lipid Digestion

The breakdown of triglycerides into monoglycerides and fatty acids in the intestines, aided by pancreatic lipase and bile salts.

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Chylomicrons

Lipoprotein particles that transport dietary fats and cholesterol from the intestines to the bloodstream.

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Gluconeogenesis

The production of new glucose molecules from non-carbohydrate sources like lactate, glycerol, and certain amino acids, primarily in the liver during periods of low glucose.

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Ketogenesis

The production of ketone bodies from excess acetyl-CoA in the liver, serving as an alternative energy source during times of low glucose availability.

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Metabolic Rate

The total amount of energy expended by the body, representing the balance between energy intake and expenditure.

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Basal Metabolic Rate (BMR)

The amount of energy required to maintain basic bodily functions at rest.

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Study Notes

Carbohydrate Metabolism

  • Cellular Respiration (with Oxygen): Involves glycolysis, the Krebs cycle, and the electron transport chain, producing ATP.
  • Glycolysis: Breaks down glucose into pyruvate, producing ATP and NADH. Occurs in the cytoplasm, doesn't need oxygen.
  • Krebs Cycle (Citric Acid Cycle): Pyruvate is converted to acetyl CoA, then enters a cycle producing ATP, NADH, and FADH2, releasing carbon dioxide. Takes place in mitochondria.
  • Electron Transport Chain (Oxidative Phosphorylation): Uses NADH and FADH2 to create a proton gradient, driving ATP synthesis. Generates most ATP during cellular respiration.
  • Anaerobic Respiration (without Oxygen): Occurs when oxygen is limited or absent, resulting in lactate production. A less efficient way to produce ATP.
  • Lactate Production (Fermentation): Pyruvate is converted to lactate, regenerating NAD+ to sustain glycolysis.
  • Gluconeogenesis: Synthesizes glucose from non-carbohydrate sources (e.g., pyruvate, lactate) when glucose levels are low. Primarily occurs in the liver.

Lipid Metabolism

  • Lipolysis: Breakdown of triglycerides into fatty acids and glycerol.
  • Ketogenesis: Creation of ketone bodies from fatty acids when glucose is scarce. Ketones can be used for energy.
  • Ketone Body Oxidation: Ketones are used as an alternative fuel source.
  • Lipogenesis: Synthesis of lipids (fatty acids, triglycerides) from acetyl CoA when glucose is abundant. Occurs in adipose and liver cells.

Protein Metabolism

  • Protein Digestion/Proteolysis: Proteins are broken down into amino acids through enzymatic processes in the stomach and small intestine.
  • Energy from Amino Acids: Amino acids can be used to produce ATP, enter glycolysis or Krebs cycle pathways.
  • Urea Cycle: Converts ammonia (toxic byproduct of protein breakdown) into urea for excretion, protecting the body.

General Metabolic Concepts

  • Metabolism: All chemical reactions in the body, divided into two types:
    • Catabolism: Breakdown of molecules to release energy (e.g., protein to amino acids).
    • Anabolism: Building of molecules from smaller ones (e.g., amino acids to proteins).
  • ATP (Adenosine Triphosphate): Primary energy currency. Energy to power bodily functions and create molecules. High energy bond between phosphates.
  • Redox Reactions: Series of reactions where molecules transfer electrons and energy.
  • Coenzymes (NAD+, FAD): Support electron transfer during metabolic reactions.
  • Metabolic Rate: Energy consumed minus energy expended; Basal Metabolic Rate (BMR) is at rest.
  • Absorptive vs Post-absorptive State: Metabolic states after or before eating.

Hormonal Regulation of Metabolism

  • Catabolic Hormones: Stimulate breakdown of molecules and energy production.
    • Cortisol: Released from adrenal gland during stress; increases blood glucose.
    • Glucagon: Released from pancreas when blood glucose is low; breakdown of glycogen.
    • Adrenaline/Epinephrine: Released during stress; increases heart rate, blood pressure and gluconeogenesis.
  • Anabolic Hormones: Stimulate synthesis of molecules.
    • Growth Hormone: Stimulates growth and tissue repair.
    • Insulin-like Growth Factor (IGF): Promotes muscle and bone growth.
    • Insulin: Regulates blood sugar levels, promotes glucose uptake by cells.
    • Testosterone & Estrogen: Influence muscle mass, strength, and metabolism.

Metabolic Diseases

  • Cushing Syndrome: Excessive cortisol production, leading to characteristic symptoms and associated health risks
  • Addison's Disease: Insufficient cortisol production, characterized by symptoms like low blood pressure, fatigue, and weight loss.
  • Pyruvate Dehydrogenase Complex Deficiency: A neurodegenerative condition impacting the Krebs cycle.
  • Phenylketonuria (PKU): Genetic disorder affecting phenylalanine metabolism. Key symptoms relate to buildup of phenylalanine in the body.

Digestion and Cellular Respiration

  • Carbohydrate Digestion: Begins in the mouth and proceeds to monosaccharide absorption in the small intestine which then transfers to the liver. After absorption cellular respiration begins.
  • Cellular Respiration: Breaks down glucose to produce ATP.
  • Glycolysis Summary: A series of reactions breaks down glucose into pyruvate, generating ATP and NADH.
  • Anaerobic Respiration Summary: In the absence of oxygen, pyruvate is converted into either lactic acid or alcohol, regenerating NAD+ to allow glycolysis to continue. Efficient but not as much ATP produced as aerobic respiration.
  • Aerobic Respiration Summary: In the presence of oxygen, the process includes glycolysis, followed by the Krebs cycle, and finally the electron transport chain.
  • Krebs Cycle Summary: Pyruvate is broken down into acetyl CoA. The cycle releases carbon dioxide and generates NADH, FADH2, and ATP.
  • Electron Transport Chain Summary: Electron carriers (NADH and FADH2) generate a proton gradient which is used by ATP Synthase to produce ATP.
  • Lipid Digestion: Lipids are broken down by pancreatic lipases and bile salts in the small intestine.
  • Chylomicrons: Transport lipids from the intestines to other tissues and organs.
  • Gluconeogenesis Summary: Glucose is produced from non-carbohydrate sources (e.g., amino acids or glycerol) when blood glucose is low.
  • Fatty Acid Breakdown: Released fatty acids are broken down to form acetyl CoA, entering the Krebs cycle or ATP.
  • Ketogenesis Summary: Excess acetyl CoA molecules are converted into ketone bodies if glucose is low or not available.
  • Ketone Oxidation Summary: Ketone bodies enter cells where they are converted into acetyl CoA to be used as an alternative energy source during periods of fasting or low glucose.
  • Lipogenesis Summary: Synthesis of fatty acids and triglycerides from acetyl CoA when glucose levels are abundant.

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Test your knowledge on carbohydrate metabolism, focusing on key processes like cellular respiration, glycolysis, and the Krebs cycle. Explore both aerobic and anaerobic pathways, including lactate production and gluconeogenesis. Challenge yourself to understand how these processes contribute to ATP production in the body.

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