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Questions and Answers
What is the primary function of carbohydrates in the body?
What is the classification of amino acids that cannot be synthesized by the body?
Which vitamin is not a fat-soluble vitamin?
What is the primary function of the citric acid cycle?
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Which hormone regulates glucose release from storage?
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What is an example of a micronutrient deficiency disease?
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What is the energy yield of carbohydrates per gram?
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What is the classification of fatty acids based on their saturation?
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What is the primary role of glucagon in regulating blood sugar levels?
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Which of the following hormones is NOT a counter-regulatory hormone?
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What is the effect of the parasympathetic nervous system on blood sugar levels?
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Which of the following factors can lead to impaired glycemic control?
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What is the primary function of insulin in regulating blood sugar levels?
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What is the result of impaired glycemic control?
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Which of the following is a benefit of maintaining optimal glycemic control?
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What is the role of the sympathetic nervous system in regulating blood sugar levels?
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What is the primary site of glycogen synthesis?
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What is the role of insulin in glucose metabolism?
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What is the final product of glycolysis?
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What is the primary site of starch digestion?
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What is the role of glucagon in glucose metabolism?
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What is the enzyme that phosphorylates glucose, trapping it in the cell?
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What is the result of fiber fermentation by gut microbiota in the large intestine?
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What is the primary mechanism of glucose transport across the cell membrane?
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What is the final product of starch digestion in the small intestine?
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What is a physiological effect of dietary fiber?
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What type of transport mechanism is used to transport glucose into cells?
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Study Notes
Macronutrients
-
Carbohydrates:
- Provide energy for the body (4 kcal/g)
- Classified into simple (sugars) and complex (polysaccharides) forms
- Important sources: grains, fruits, vegetables, and dairy products
-
Proteins:
- Build and repair tissues (4 kcal/g)
- Composed of amino acids (20 standard amino acids)
- Essential amino acids (9) cannot be synthesized by the body and must be obtained through diet
- Important sources: meat, fish, eggs, dairy products, and legumes
-
Fats:
- Provide energy and absorb fat-soluble vitamins (9 kcal/g)
- Classified into saturated and unsaturated forms
- Important sources: oils, fatty fish, nuts, and seeds
Micronutrients
-
Vitamins:
- Fat-soluble: A, D, E, and K
- Water-soluble: B vitamins (8) and C
- Function as coenzymes, antioxidants, and hormone regulators
-
Minerals:
- Macro-minerals: calcium, phosphorus, magnesium, potassium, sodium, and chloride
- Micro-minerals (trace elements): iron, zinc, iodine, selenium, copper, and others
- Involved in enzyme functions, nerve transmission, and bone health
Metabolic Pathways
- Glycolysis: breakdown of glucose to pyruvate (anaerobic)
- Citric Acid Cycle (Krebs Cycle): breakdown of acetyl-CoA to ATP, NADH, and FADH2 (aerobic)
- Fatty Acid Oxidation: breakdown of fatty acids to acetyl-CoA
- Protein Synthesis: assembly of amino acids into proteins
Hormone Regulation
- Insulin: regulates glucose uptake and storage
- Glucagon: regulates glucose release from storage
- Thyroid Hormones: regulate metabolic rate
- Adrenaline (Epinephrine): regulates energy metabolism and response to stress
Nutrient Interactions and Deficiencies
- Synergistic effects: nutrients work together to produce a greater effect
- Antagonistic effects: nutrients counteract each other's effects
- Deficiencies: can lead to various diseases and disorders, such as scurvy (vitamin C), rickets (vitamin D), and anemia (iron)
Macronutrients
- Carbohydrates provide energy for the body, with 4 kcal of energy per gram.
- They are classified into simple (sugars) and complex (polysaccharides) forms.
- Important sources of carbohydrates include grains, fruits, vegetables, and dairy products.
- Proteins build and repair tissues, with 4 kcal of energy per gram.
- They are composed of amino acids, with 20 standard amino acids and 9 essential amino acids that cannot be synthesized by the body.
- Important sources of proteins include meat, fish, eggs, dairy products, and legumes.
- Fats provide energy and absorb fat-soluble vitamins, with 9 kcal of energy per gram.
- They are classified into saturated and unsaturated forms.
- Important sources of fats include oils, fatty fish, nuts, and seeds.
Micronutrients
- Vitamins are classified into fat-soluble (A, D, E, and K) and water-soluble (B vitamins and C).
- They function as coenzymes, antioxidants, and hormone regulators.
- Minerals are classified into macro-minerals (calcium, phosphorus, magnesium, potassium, sodium, and chloride) and micro-minerals (trace elements).
- Minerals are involved in enzyme functions, nerve transmission, and bone health.
Metabolic Pathways
- Glycolysis is the breakdown of glucose to pyruvate, an anaerobic process.
- The citric acid cycle (Krebs cycle) is the breakdown of acetyl-CoA to ATP, NADH, and FADH2, an aerobic process.
- Fatty acid oxidation is the breakdown of fatty acids to acetyl-CoA.
- Protein synthesis is the assembly of amino acids into proteins.
Hormone Regulation
- Insulin regulates glucose uptake and storage.
- Glucagon regulates glucose release from storage.
- Thyroid hormones regulate metabolic rate.
- Adrenaline (epinephrine) regulates energy metabolism and response to stress.
Nutrient Interactions and Deficiencies
- Synergistic effects occur when nutrients work together to produce a greater effect.
- Antagonistic effects occur when nutrients counteract each other's effects.
- Deficiencies in nutrients can lead to various diseases and disorders, such as scurvy (vitamin C deficiency), rickets (vitamin D deficiency), and anemia (iron deficiency).
Glycemic Control
Definition
- Glycemic control is the regulation of blood sugar levels to maintain a stable and healthy range.
Importance
- Optimal blood sugar levels prevent and manage diseases like diabetes, cardiovascular disease, and obesity.
- Glycemic control is essential for energy homeostasis, cognitive function, and overall health.
Mechanisms of Glycemic Control
- Glucagon stimulates glycogenolysis and gluconeogenesis to increase blood glucose levels.
- Insulin promotes glucose uptake in cells, inhibits glycogenolysis and gluconeogenesis, and stimulates glycogen synthesis.
- Cortisol, growth hormone, and thyroid hormone are counter-regulatory hormones that increase blood glucose levels.
- The sympathetic nervous system stimulates glycogenolysis and gluconeogenesis.
- The parasympathetic nervous system promotes insulin secretion and glucose uptake.
Factors Affecting Glycemic Control
- Consuming high-carbohydrate, high-fiber, or low-glycemic index foods regulates blood sugar levels.
- Regular physical activity improves insulin sensitivity and glucose uptake.
- Chronic stress leads to insulin resistance and impaired glycemic control.
- Adequate sleep is essential for maintaining optimal glycemic control.
- Genetic predisposition affects an individual's ability to regulate blood sugar levels.
Clinical Implications
- Diabetes is a disease characterized by impaired glycemic control, leading to hyperglycemia and associated complications.
- Hypoglycemia is a condition characterized by low blood sugar levels, often resulting from excessive insulin secretion or insulin sensitivity.
- Metabolic Syndrome is a cluster of conditions, including insulin resistance, glucose intolerance, and cardiovascular disease risk factors.
Carbohydrate Metabolism
- Starch is a complex carbohydrate composed of amylose and amylopectin
- Salivary amylase breaks down starch into maltose and dextrins in the mouth
- Pancreatic amylase further breaks down maltose and dextrins into maltose in the small intestine
- Maltase converts maltose into glucose, which is then absorbed into the bloodstream
Dietary Fiber
- Dietary fiber is a type of carbohydrate that is not digestible by human enzymes
- Fiber is classified into soluble (e.g. pectin, gum) and insoluble (e.g. cellulose, hemicellulose) types
- Gut microbiota ferments fiber in the large intestine, producing short-chain fatty acids (SCFAs)
- SCFAs can be used as energy by the host or excreted in the feces
Glucose Transport and Uptake
- Glucose is transported across the cell membrane through facilitated diffusion
- GLUT proteins (e.g. GLUT2, GLUT4) are specific transporters for glucose
- Sodium-glucose cotransport uses the energy from sodium gradients to transport glucose
- Insulin stimulates the translocation of GLUT4 to the cell surface, increasing glucose uptake in muscle and adipose tissue
Glycogen Metabolism
- Glycogen is a complex carbohydrate stored in the liver and muscle
- Glycogen synthase adds glucose molecules to the growing glycogen chain during synthesis
- Insulin stimulates glycogen synthesis, while glucagon inhibits it
- ATP and glucose-6-phosphate are allosteric activators of glycogen synthase
Glycolysis
- Glycolysis is the first step in cellular glucose metabolism, converting glucose into pyruvate
- Glycolysis generates ATP and NADH through 10 enzyme-catalyzed reactions
- Key regulatory steps in glycolysis include:
- Hexokinase phosphorylating glucose, trapping it in the cell
- Phosphofructokinase 1 committing glucose to glycolysis
- Pyruvate kinase regulating the final step of glycolysis, influenced by ATP and fructose-2,6-bisphosphate
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Description
Understand the role of carbohydrates and proteins in the human body, including their functions, sources, and composition. Learn about the importance of these macronutrients in our diet.
