Macronutrients and Micronutrients

• Nutrients are substances obtained from food and used by the body to promote growth, maintenance, and repair

Macronutrients

• Carbohydrates, fats (lipids), and proteins are the main macronutrients
• They provide the body with energy, measured in kilocalories (kcal) or Calories
• 1 gram of carbohydrate provides approximately 4 kcal
• 1 gram of protein provides approximately 4 kcal
• 1 gram of fat provides approximately 9 kcal
• Water is an essential nutrient but does not provide energy

Micronutrients

• Vitamins and minerals are essential micronutrients
• They do not provide energy but are necessary for various metabolic processes

Carbohydrates

• Carbohydrates are the body's primary source of energy
• Simple carbohydrates include monosaccharides (glucose, fructose, galactose) and disaccharides (sucrose, lactose, maltose)
• Complex carbohydrates include polysaccharides (starch, glycogen, fiber)
• Glucose is the main form of carbohydrate used by the body
• Excess glucose is stored as glycogen in the liver and muscles
• Fiber is indigestible carbohydrate important for digestive health

Lipids (Fats)

• Lipids include triglycerides, phospholipids, and sterols
• Triglycerides are the main form of fat in the diet and body
• Saturated fats are typically solid at room temperature and found in animal products
• Unsaturated fats can be monounsaturated or polyunsaturated and are typically liquid at room temperature
• Essential fatty acids, such as omega-3 and omega-6 fatty acids, must be obtained from the diet
• Cholesterol is a sterol found in animal products and is important for cell membrane structure and hormone synthesis

Proteins

• Proteins are composed of amino acids
• Essential amino acids must be obtained from the diet
• Proteins are used for building and repairing tissues, making enzymes and hormones, and supporting the immune system
• Complete proteins contain all essential amino acids and are found in animal products
• Incomplete proteins lack one or more essential amino acids and are found in plant products
• Protein complementation involves combining different plant sources to obtain all essential amino acids

Vitamins

• Vitamins are organic compounds needed in small amounts for various body functions
• Fat-soluble vitamins (A, D, E, K) are stored in the body
• Water-soluble vitamins (B vitamins, vitamin C) are not stored in the body and need to be consumed regularly

Minerals

• Minerals are inorganic substances needed for various body functions
• Major minerals (calcium, phosphorus, potassium, sodium, chloride, magnesium, sulfur) are needed in larger amounts
• Trace minerals (iron, zinc, copper, iodine, fluoride, selenium) are needed in smaller amounts

Water

• Water is essential for hydration, temperature regulation, nutrient transport, and waste removal
• Water requirements vary depending on activity level, climate, and overall health

Metabolism Overview

• Metabolism refers to all chemical processes that occur in the body to maintain life
• Anabolism is the building up of complex molecules from simpler ones (requires energy)
• Catabolism is the breaking down of complex molecules into simpler ones (releases energy)

Carbohydrate Metabolism

• Digestion breaks down carbohydrates into glucose
• Glucose is absorbed into the bloodstream
• Insulin helps glucose enter cells for energy production or storage as glycogen
• Glycolysis is the breakdown of glucose to pyruvate in the cytoplasm
• Pyruvate is converted to acetyl-CoA, which enters the citric acid cycle (Krebs cycle) in the mitochondria
• The citric acid cycle produces energy carriers (NADH, FADH2) and carbon dioxide
• The electron transport chain uses NADH and FADH2 to generate ATP (adenosine triphosphate), the main energy currency of the cell
• Gluconeogenesis is the synthesis of glucose from non-carbohydrate sources (amino acids, glycerol)

Lipid Metabolism

• Digestion breaks down fats into fatty acids and glycerol
• Fatty acids are absorbed into the bloodstream
• Lipoproteins (chylomicrons, VLDL, LDL, HDL) transport lipids in the blood
• Beta-oxidation is the breakdown of fatty acids into acetyl-CoA in the mitochondria
• Acetyl-CoA enters the citric acid cycle to produce energy
• Excess fatty acids can be stored as triglycerides in adipose tissue
• Lipogenesis is the synthesis of fatty acids from acetyl-CoA

Protein Metabolism

• Digestion breaks down proteins into amino acids
• Amino acids are absorbed into the bloodstream
• Amino acids are used to synthesize new proteins
• Deamination is the removal of the amino group (NH2) from amino acids
• The amino group is converted to urea and excreted in urine
• The remaining carbon skeleton can be used for energy production or converted to glucose or fatty acids

Energy Balance

• Energy balance is the relationship between energy intake (food) and energy expenditure (physical activity, basal metabolism)
• Positive energy balance: Energy intake exceeds energy expenditure, leading to weight gain
• Negative energy balance: Energy expenditure exceeds energy intake, leading to weight loss
• Basal metabolic rate (BMR) is the energy needed to maintain basic body functions at rest
• Factors affecting BMR include age, sex, body composition, and hormones
• Physical activity increases energy expenditure
• Thermic effect of food (TEF) is the energy used to digest, absorb, and metabolize food

Regulation of Metabolism

• Hormones play a crucial role in regulating metabolism
• Insulin promotes glucose uptake and storage, while glucagon promotes glucose release
• Thyroid hormones (T3, T4) regulate metabolic rate
• Cortisol, a stress hormone, affects glucose, fat, and protein metabolism
• Enzymes catalyze metabolic reactions
• Metabolic pathways are regulated by feedback mechanisms

Metabolic Disorders

• Diabetes mellitus is a disorder of glucose metabolism due to insulin deficiency or resistance
• Type 1 diabetes is an autoimmune disease where the body does not produce insulin
• Type 2 diabetes is characterized by insulin resistance
• Metabolic syndrome is a cluster of conditions (high blood pressure, high blood sugar, abnormal cholesterol levels, excess abdominal fat) that increase the risk of heart disease, stroke, and diabetes
• Phenylketonuria (PKU) is a genetic disorder where the body cannot metabolize phenylalanine