Questions and Answers
What is the primary purpose of anabolism in the body?
What is the process called when glucose is converted to glycogen in the liver and muscle tissues?
Where is glycogen reconverted to glucose to maintain blood glucose levels?
What is the primary function of glycogen in the body?
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What is the end product of glycolysis in muscle contraction?
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What is the process of breaking down large complex molecules into smaller ones?
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Where does glycogenolysis occur in the cell?
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What is the product of glycogenolysis?
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Where is glucose stored as glycogen?
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What is the role of glucagon in glycogenolysis?
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What is the byproduct of glycolysis when producing energy from glucose?
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Where does gluconeogenesis mainly occur?
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What is the purpose of glycogenolysis?
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What is the net energy yield of gluconeogenesis?
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What is the purpose of glycogen phosphorylation?
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What is the metabolic pathway that converts glucose into pyruvate?
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During fasting, what metabolic pathways are increased in the liver?
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What is the primary function of insulin in the body?
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What is the main cause of diabetes (hyperglycemia)?
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Which of the following is NOT a human disease of carbohydrate metabolism?
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What is the primary role of glucagon in the body?
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Which of the following enzymes is responsible for breaking down lactose?
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What is the primary effect of insulin on glycogenesis?
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Which of the following metabolic pathways leads to the production of glucose from non-carbohydrate sources?
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Study Notes
Carbohydrate Metabolism
- Metabolism is the total amount of biochemical reactions that occur within each cell of living organisms, providing energy for vital processes and synthesizing new organic material.
Anabolism and Catabolism
- Anabolism is a biochemical process that builds up large complex molecules from simple molecules, consumes energy through ATP hydrolysis, and represents growth of muscles, bones, and other body structures.
- Catabolism is a process where large complex molecules are broken down into smaller ones, releasing energy, and involves processes such as glycolysis.
Fate of Glucose after Absorption
- In the liver, glucose undergoes various chemical changes depending on the physiological need of the body, including: • Oxidation to CO2, H2O, and energy (glycolysis and citric acid cycle) • Conversion to glycogen (glycogenesis) and storage in liver and muscle tissues • Reconversion of glycogen to glucose (glycogenolysis) to maintain blood glucose levels • Conversion to fatty acids and storage in adipose tissue as triglycerides (lipogenesis) • Utilization for synthesis of ribose and deoxyribose for nucleic acids • Partial degradation in muscle contraction, resulting in lactic acid formation
Glycolysis
- Glycolysis is the metabolic pathway that converts glucose into pyruvate
- It produces 2 molecules of pyruvate, ATP, NADH, and water
- The process takes place in the cytosol (cytoplasm) of a cell and does not require oxygen
- Glucose phosphorylation occurs on the cell membrane by the action of glucokinase (in the liver) and hexokinase (in liver and other extra-hepatic cells)
Glycogenesis (Glycogen Synthesis)
- Glycogenesis is the formation of glycogen from glucose
- Glycogen serves as an energy store primarily in muscle and liver when glucose and ATP are present in relatively high amounts
- Insulin promotes glucose conversion into glycogen for storage in liver and muscle cells
Glycogenolysis
- Glycogenolysis is the biochemical breakdown of glycogen to glucose
- It takes place in the cells of muscle and liver tissues in response to hormonal and neural signals
- Glycogenolysis is stimulated by glucagon and adrenaline hormones
- It plays an important role in regulating glucose levels in the blood
Gluconeogenesis
- Gluconeogenesis is the process of producing glucose from non-carbohydrate sources
- 6 ATP molecules are consumed per molecule of glucose produced
- Most reactions take place in the cytoplasm, while two reactions occur in the mitochondria
- It mainly occurs in hepatocytes in the liver
- Substrates for gluconeogenesis include proteins, lipids, and pyruvate
Regulatory Pathways
- During fasting, glycolysis rates decrease, while gluconeogenesis and glycogenolysis rates increase, leading to increased hepatic glucose production
- In response to feeding, glycolysis rates increase, while gluconeogenesis and glycogenolysis rates decrease, leading to suppression of hepatic glucose production
Insulin and Glucagon
- Insulin facilitates glucose entry into cells and promotes glucose storage as glycogen in liver and skeletal muscles, and as triglycerides in fat cells
- Insulin deficiency or resistance leads to diabetes (hyperglycemia)
- Glucagon stimulates the liver to break down glycogen to release glucose into the blood and activates gluconeogenesis and lipolysis
Human Diseases of Carbohydrate Metabolism
- Diabetes mellitus
- Lactose intolerance
- Fructose intolerance
- Galactosemia
- Glycogen storage disease
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Description
This quiz covers the basics of carbohydrate metabolism, including the importance of metabolic processes and the two types of metabolic reactions. Learn about the biochemical reactions that take place within cells and how they provide energy for vital processes.
