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?

Conduction 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?

1000 Signup and view all the answers

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

Glycolysis Signup and view all the answers

What is the primary purpose of gluconeogenesis in the body?

To synthesize glucose from non-carbohydrate sources Signup and view all the answers

Which of the following statements about catabolic reactions is true?

They break down organic molecules to release energy. Signup and view all the answers

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

40% Signup and view all the answers

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

ATP Signup and view all the answers

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

The body utilizes energy stores for fuel. Signup and view all the answers

What is the primary function of the urea cycle?

To eliminate excess nitrogen from amino acids Signup and view all the answers

Which of the following best describes lipogenesis?

The conversion of excess carbohydrate to fats Signup and view all the answers

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

Glycolysis Signup and view all the answers

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

Accept hydrogen atoms Signup and view all the answers

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

Ethanol Signup and view all the answers

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

2 ATP, 1 FADH2, 3 NADH Signup and view all the answers

What is produced during glycolysis from one molecule of glucose?

2 pyruvate and 2 NADH 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?

Pump protons to create a gradient Signup and view all the answers

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

To regenerate NAD+ Signup and view all the answers

What is the final waste product released during aerobic respiration?

Carbon dioxide Signup and view all the answers

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

36 to 38 ATP Signup and view all the answers

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

Oxaloacetate Signup and view all the answers

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

32-34 ATP molecules 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?

ATP synthase Signup and view all the answers

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

Cholecystokinin (CCK) Signup and view all the answers

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

To synthesize new glucose molecules Signup and view all the answers

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

Beta-oxidation 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?

Ketogenesis Signup and view all the answers

What is the main purpose of the urea cycle?

To excrete nitrogenous waste Signup and view all the answers

During lipid digestion, which compounds are transported by chylomicrons?

Triglycerides and cholesterol Signup and view all the answers

What process converts ammonia into urea?

Urea Cycle Signup and view all the answers

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

Gluconeogenesis Signup and view all the answers

What is primarily the role of amino acids during starvation?

To provide energy leading to potential body deterioration Signup and view all the answers

What metabolic process involves the breakdown of triglycerides for energy?

Beta-oxidation Signup and view all the answers

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

Cortisol Signup and view all the answers

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

Developmental defects due to high phenylalanine levels Signup and view all the answers

How does insulin primarily affect carbohydrate metabolism?

Promotes glucose uptake and storage in cells Signup and view all the answers

What is a primary characteristic of Cushing syndrome?

Excessive cortisol production Signup and view all the answers

What does the pyruvate dehydrogenase complex enzyme convert pyruvate into?

Acetyl CoA Signup and view all the answers

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

Growth hormone Signup and view all the answers

What is a treatment for Addison's disease?

Cortisol replacement therapy Signup and view all the answers

What metabolic outcomes can result from malfunctioning enzymes?

Metabolic diseases leading to various manifestations Signup and view all the answers

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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Description

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.