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Digestion and Excretion The Need for Digestion Digestion: the process of breaking down food particles into molecules small enough to be absorbed by cells Polymers are too large to pass through the cell membrane in humans The mitochondria will use the digested nutrients to make energy There are four macromolecules: carbohydrates, proteins, lipids, and nucleic acids Carbohydrates Sugars Polymers = large molecules Carbohydrate polymers are polysaccharides Monomers = small subunits Carbohydrate monomers are simple sugars or monosaccharide's Ex: glucose, sucrose, lactose, maltose The functions of carbohydrates are: 1. to store energy 2. to provide building materials for the body Lipids Fats and oils Polymers are sometimes called triglycerides Monomers are 1 glycerol and 3 fatty acids The energy stored in lipids is for long-term use and is not used up quickly It takes a lot of exercise to burn fat Vegetable oils contain unsaturated fats; meats and dairy contain saturated fats Unsaturated fats are less likely to cause heart disease than saturated fats Nucleic Acids Carry hereditary information Polymers are DNA and RNA Monomers are nucleotides Proteins Proteins are large polymers made of amino acid monomers There are 20 different amino acids The order of the amino acids determines the protein’s properties Enzymes Enzymes: proteins that speed up reactions in organisms Also called organic catalysts Work on substances called substrates Substrates are turned into products Condensation synthesis = enzymes help make a big molecule from smaller ones Hydrolysis = enzymes help break a larger molecules down into smaller pieces Enzymes have an area called the active site that matches the shape of the substrate Enzymes are specific for their substrates The active site and substrate are said to fit together just as a key fits in a lock (lock and key model) Enzymes are not changed or used up in reactions Enzymes speed up reactions by lowering the activation energy Activation energy = the energy needed to get a reaction started 1 2 Enzyme-substrate complex Products 4 3 Enzyme breaks the bond holding the substrate together Enzymes lose their specific shape (they denature) if they are exposed to unfavorable conditions Most enzymes work best at 37°C and a neutral pH Pepsin, an enzyme in the stomach, works best at an acidic pH Types of Digestion Extracellular digestion: food is broken down by enzymes outside the body Fungi have special structures called rhizoids that secrete enzymes onto food The food is then absorbed by the fungus Rhizoids Intracellular digestion: food is broken down by enzymes inside the cells The amoeba engulfs its food using extensions of its cytoplasm called pseudopods Process is called phagocytosis The paramecium uses hair-like extensions called cilia to push food into its oral groove Human Digestion Human digestion is intracellular Unlike the amoeba and paramecium, humans have digestive organs Mouth Pharynx Salivary glands Liver Gall bladder Esophagus Stomach Small intestine Large intestine Pancreas Appendix Anus Rectum Pathway of Digestion 1. Mouth: site of mechanical and chemical digestion Ingestion the process of taking food into the organism) Carb digestion begins in the mouth. Teeth: grind up food (mechanical) Salivary glands: secrete saliva into the mouth Saliva contains the enzyme salivary amylase that breaks down carbohydrates (chemical) Epiglottis closes off the trachea when you swallow 2. Peristalsis: rhythmic waves of muscle 3. Stomach: both mechanical and chemical digestion occurs. Protein digestion begins here. The walls grind and churn food Gastric juice contains pepsin and hydrochloric acid Pepsin: enzyme that breaks down proteins CHYME: liquid material found in stomach (digested food) 4. Small intestine: where most chemical digestion occurs Has many finger-like projections called villi that absorb nutrients into the blood Other organs secrete substances into the small Pancreas: secretes enzymes for breaking down lipids, proteins, and carbohydrates into the small intestines. Liver: makes bile, which breaks fat globules into smaller pieces Called emulsification Allows enzymes to digest the fats Gall bladder: stores bile until it is needed secretes into the small intestines. Absorption of nutrients. 5. Large intestine: absorbs water from undigested material No digestion occurs Indigestible matter becomes feces, which pass through the rectum and anus Diseases Peptic ulcers form when the protective mucus lining of the stomach is destroyed by bacteria Helicobacter pylori The hydrochloric acid breaks down the stomach wall Pancreatitis happens when the duct that connects the pancreas to the small intestine is blocked Enzymes build up in the pancreas and start to digest it Colon cancer occurs in the large intestine May be genetic May be caused by low-fiber diets where the feces remain in the intestine for too long Fiber = roughage Gallstones: bile/cholesterol hardens in the form of stones and blocks the passage of bile into the small intestines. Pain and discomfort are the symptoms. Anorexia: eating disorder, person under eats, psychological issue. Bulimia: Binge and Purge. Eat large quantities and then vomit. Psychological issue at start then resulting in bodily damage. Excretory System Excretion: the removal of metabolic wastes from the body Includes the liver, skin, lungs and kidneys The liver breaks down old red blood cells, recycles useful materials, and breaks down extra amino acids(deamination) The skin gets rid of water and salts through sweat Kidneys filter the blood Nephron Kidney Kidney Renal artery Renal vein Ureter Urinary bladder Urethra Ureter Bowman’s capsule Glomerulus Tubule Capillaries Kidneys Filter wastes out of the blood Urea is a waste made by cells during metabolism The filtering is done by microscopic structures called nephrons in the kidneys Blood is brought to the kidneys by the renal artery and enters the glomerulus of the nephron Wastes leave the blood and enter Bowman’s capsule Urine is made as the wastes travel through the tubule Urine leaves the kidneys through the ureters Urine is stored in the urinary bladder The urethra carries urine out of the body Diseases Nephritis: inflammation of the kidney caused by a bacterial infection Bladder infection. If not treated with antibiotics, it can lead to kidney failure Kidney stones are caused by a build up of calcium May pass on their own (painful!) or require surgery GOUT: Uric acid crystals in the joints. Painful and swollen joints. Kidney Failure: kidneys are not working for a variety of reasons. DIALYSIS: a machine that filters the blood in place of the kidney. Transplant: a donor kidney is implanted into another persons body. (Match it) Immunosuppressant drugs are taken.