Digestive System

• Factors that effect energy requirements / metabolism include: body size, physical activity, sex, age, hereditary factors.
• Catabolism: reactions that break down larger molecules into smaller subunits
• Anabolism: reactions that use energy to produce larger molecules from smaller subunits
• Mechanical digestion is the physical breakdown of food (Ex. teeth, stomach churning, bile salts).
• Chemical digestion is the chemical breakdown of food (using enzymes/gastric juices) Ex. amylase, pepsin, lipase.
• Sucrase breaks down sucrose.
• Proteases break down proteins.
• Lipases break down lipids.
• Enzymes are catalysts and speed up chemical reactions without being used up.
• Reactants are the starting substance, which change into products after chemical reactions.
• Daily caloric intake should include 30% fats, 50% to 60% carbs, and 10% to 20% proteins.
• Proteins are made up of amino acids linked together.
• Proteins help build and maintain muscle tissue, immune system is reliant on enzymes and proteins, transport molecules across cell membrane, and provide structural support to cells, tissues, and organs.
• Proteins are essential for the growth, repair, and maintenance of tissues and organs, play a crucial role in the synthesis of enzymes, hormones, and anti-bodies, and provide necessary amino acids the body cant produce on its own.
• Carbohydrates are our primary source of energy (ex. glucose), are used for quick energy, and contribute to the structure and function of cells and tissues.
• Carbs are made up of monosaccharids (ex. gluclose): there are simple carbs (ex. sugars) and complex carbs (starches and fibres).
• Carbs are essential as they provide necessary energy for various cellular processes and physical activites.
• Lipids are a source of long term energy storage, provide insulation and cushion to tissues, are part of the cell membrane, and synthesize hormones.
• Lipids are composed of fatty acids and glycerol.
• Lipids are essential as they are a concentrated source of energy, provide fatty acids the body cant produce, help with the absorption of fat soluble vitamins (A, D, E, K) and are essential for overall health.
• Substrates are compounds that enzymes act upon.
• The active site is the region at which the enzyme attaches to the substrate.
• Industrial applications of enzymes include: yogurt, medicine, and meats (tenderizing).
• The ideal starch digestion environment is warm (37 C) and a PH of 7 (Neutral).
• Cellulose is an essential dietary fibre from green plants, acts as a cleaning agent for the digestive system by assisting in the movement of food.
• Salivary glands produce salivary amylase for carb digestion.
• The stomach produces hydrochloric acid, pepsin / pepsinogen, and mucus (Primarily for protein digestion).
• The pancreas secretes pancreatic amylase, bicarbonate, trypsinogen, and pancreatic lipase. It also regulates blood sugar levels.
• The liver produces bile while the gall bladder stores and releases it as needed.
• The small intestine produces erepsin and carboxypeptidases such as maltase, sucrase, and lactase.
• All accessory organs (Pancreas, liver, gall bladder) assist and are connected to the small intestine.
• Ingestion occurs in the mouth, pharynx, esophagus, and small intestine.
• Digestion occurs in the stomach.
• Absorption occurs in the large and small intestine (Water & vitamins + nutrients).
• Excretion occurs in the rectum and anus.
• The small intestine is the main site of digestion and absorption of nutrients.
• Small finger-like projections called villi line the surface of the small intestine and increase the available surface area for nutrient absorption. The small intestine is also a long coiled tube shape which increases surface area and allow nutrients to travel and be absorbed for a long period.