Questions and Answers
Define anabolic, catabolic, and amphibolic metabolic pathways.
Anabolic pathways build molecules and require energy, catabolic pathways break down molecules and release energy, while amphibolic pathways can function in both anabolic and catabolic processes.
What are the main sites of dietary carbohydrate digestion?
The mouth and the intestinal lumen are the main sites of dietary carbohydrate digestion.
What role do glycoside hydrolases play in carbohydrate digestion?
Glycoside hydrolases catalyze the hydrolysis of glycosidic bonds in carbohydrates.
Describe the function of endoglycosidases.
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What is the significance of disaccharidases in carbohydrate metabolism?
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How do metabolic pathways regulate the flux of metabolites?
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Explain how metabolic fuels are provided in the fed vs. fasting states.
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Study Notes
Overview of Metabolism
- Metabolism encompasses all biochemical processes involving the conversion of food into energy and cellular components.
- Metabolic pathways can be categorized into three types:
- Anabolic pathways: Build complex molecules from simpler ones, requiring energy (e.g., synthesis of proteins).
- Catabolic pathways: Break down complex molecules into simpler ones, releasing energy (e.g., glycolysis).
- Amphibolic pathways: Serve as both anabolic and catabolic processes, integrating metabolism (e.g., citric acid cycle).
Metabolism of Nutrients
- Key macronutrients include carbohydrates, lipids, and amino acids, each metabolized in tissues and organs.
- At the subcellular level, metabolism involves specific organelles (e.g., mitochondria for aerobic respiration).
- Interconversion of metabolic fuels allows the body to adapt to different energy demands and nutrient availabilities.
Regulation of Metabolic Pathways
- Flux of metabolites through pathways is regulated by:
- Enzyme activity, which can be modulated by allosteric effects and covalent modifications (e.g., phosphorylation).
- Hormonal signaling that influences enzyme expression and activity (e.g., insulin promoting glucose uptake).
- Availability of substrates and energy status within the cell.
Supply of Metabolic Fuels
- In the fed state, the body stores excess energy as glycogen and fat.
- Metabolic reserves are mobilized during the fasting state through hormone-regulated pathways:
- Glycogenolysis: breakdown of glycogen into glucose.
- Lipolysis: breakdown of triglycerides into fatty acids and glycerol.
Digestion and Absorption of Carbohydrates
- Major dietary carbohydrates include starch, sucrose, and lactose.
- Primary sites of carbohydrate digestion:
- Mouth: Salivary amylase begins starch breakdown.
- Intestinal lumen: Further digestion by pancreatic enzymes occurs here.
- Digestion is rapid, facilitated by glycoside hydrolases (glycosidases) that hydrolyze glycosidic bonds.
Enzyme Functions in Carbohydrate Digestion
- Endoglycosidases: Enzymes that hydrolyze internal glycosidic bonds within polysaccharides and oligosaccharides.
- Disaccharidases: Enzymes that hydrolyze disaccharides into reducing sugars, necessary for absorption.
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Description
This quiz covers the fundamental concepts of metabolism, including the various biochemical processes involved in converting food into energy. Explore the three types of metabolic pathways: anabolic, catabolic, and amphibolic, to understand how they contribute to cellular functions.
