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Questions and Answers
What processes are tightly linked by their coordinated energy requirements?
What is the first stage of metabolism in which large molecules are broken down?
Which stage of catabolism involves the oxidation of small molecules to CO2 and H2O?
In which way does metabolism regulate the flow of materials through a pathway?
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What do multi-step metabolic pathways provide compared to single-step pathways?
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What is the primary reason the action of salivary amylase stops in the stomach?
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Which enzyme is responsible for further carbohydrate digestion in the small intestine?
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Which phase of intestinal digestion involves the action of intestinal brush border enzymes?
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In what initial location does carbohydrate digestion begin?
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Which of the following is NOT a dietary carbohydrate type mentioned?
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Study Notes
Metabolism Overview
- Anabolism involves reduction reactions and uses energy from ATP.
- Catabolism releases energy from nutrients, stored in ATP for use in anabolic processes.
- Metabolism consists of discrete, multi-step pathways allowing control over energy input and output.
Stages of Catabolic Reactions
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Stage 1: Digestion and Hydrolysis
- Breaks down large molecules into smaller ones for bloodstream entry.
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Stage 2: Degradation
- Further breakdown and partial oxidation result in 2 and 3-carbon compounds.
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Stage 3: Oxidation
- Small molecules are oxidized to CO₂ and H₂O in the citric acid cycle, generating ATP.
Metabolic Regulation
- Metabolism is tightly regulated to adapt to changing conditions.
- Regulation occurs at cellular, molecular, nervous, and endocrine levels.
- Flux refers to the flow of materials in a pathway, influenced by substrate supply, product removal, and enzyme activities.
Digestion of Carbohydrates
- Carbohydrates are a primary energy source.
- Salivary amylase initiates digestion; activity halts in the acidic stomach.
- Pancreatic juice, containing pancreatic amylase, continues carbohydrate digestion in the small intestine.
Steps of Starch Digestion
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Intraluminal Hydrolysis
- Initiated by salivary α-amylase; resumed by pancreatic α-amylase in the duodenum.
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Brush-Border Hydrolysis
- Disaccharides and oligosaccharides are broken down to monosaccharides by intestinal enzymes.
Enterocytes and Absorption
- Enterocytes line the intestines and are responsible for nutrient absorption.
- Microvilli increase surface area, facilitating transport of digested products.
- Enterocytes secrete hormones such as leptin.
Brush-Border Enzymes
- Specific enzymes hydrolyze disaccharides and oligosaccharides:
- Sucrase: Hydrolyzes sucrose to fructose and glucose.
- Maltase: Breaks down maltose into glucose.
- Lactase: Converts lactose into glucose and galactose.
Embden–Meyerhof–Parnas Pathway (Glycolysis)
- Key role in energy metabolism by breaking down glucose to pyruvate while synthesizing ATP.
- Glycolysis is divided into two main phases: energy investment phase and energy recovery phase.
Glycolysis Phases
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Energy Investment Phase:
- Glucose is phosphorylated to glucose-6-phosphate by hexokinase or glucokinase.
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Splitting Phase:
- Breakdown of fructose-1,6-bisphosphate into two 3-carbon molecules.
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Energy Generation Phase:
- ATP is produced through substrate-level phosphorylation.
Key Enzymes in Glycolysis
- Hexokinase: Initiates glycolysis; phosphorylates glucose (rate-limiting step).
- Phosphofructokinase: Key regulatory enzyme that adds a phosphate to fructose-6-phosphate.
- Pyruvate Kinase: Transfers a phosphate to ADP, generating ATP and pyruvate.
Summary of Glycolytic Steps
- Each step in glycolysis involves a specific enzyme facilitating conversion and energy extraction from glucose. These reactions are crucial for cellular respiration and energy production.
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Description
This quiz covers the basics of metabolism, focusing on the processes of anabolism and catabolism. Understand how these metabolic pathways are interconnected and their role in energy transformation within biological systems. Test your knowledge on digestion, energy utilization, and metabolic stages.
