Digestive System Obtaining nutrients Energy Body cells need energy to run cell processes.
Animals obtain chemical energy fromfood. Energy is derived from breakingchemical bonds. Food energy is measured in units calledcalories. Many lipids are made up of fatty acids and glycerine.
Lipids are fats, oils, andwaxes. Lipids are used forstoring energy, makingcell membranes, andsynthesizing steroidhormones. No Monomer Many lipids are made up of fatty acids and glycerine. Starch is made up of glucose.
Carbohydrates Sugars and starch arethe carbohydrates thathumans can digest.Fiber is indigestiblecarbohydrates, such ascellulose and inulin. Glucose is needed byall body cells as energy. Monomer = monosaccharide Starch is made up of glucose. Proteins are made up of amino acids.
Amino acids fromdigested proteins areused by cells to build allthe proteins that ourbody needs. Humans need a balanceof the 20 amino acids,which can be obtainedfrom animal proteins, orby blending plantprotein sources. Monomer = amino acids Proteins are made up of amino acids. Macromolecule summary
Polymers Monomers Roles Complex Carbohydrates (i.e. starch) Glucose and other simple sugars Broken apart to get energy to make ATP. Proteins Amino acids Used to make our own enzymes and other body proteins. Lipids (Fats, waxes, oils, and steroids) None Used for cellular energy and energy storage; used to make cell membranes, steroid hormones. Nucleic Acids Nucleotides Store and transmit hereditary information Digestion Two-way digestion Simple animals have asingle digestive pouchwith a single opening. Food enters throughthe opening, wasteleaves through thesame opening. These organisms mustfinish digesting beforeeating again. One-way digestion More complex animals have one-way digestion.
Food enters oneopening and wasteleaves from another. Animals with one-waysystems can eat anytime, which is anadvantage. Mechanical digestion In humans, mechanicaldigestion takes place in themouth. Human incisors andcanines are adapted fortearing food, while molarsare adapted for grindingfood. Saliva, which containsenzymes, mixes with food. Stomach Acid digestion occurs in the stomach.
Gastrin, a hormone,stimulates acid release. Pepsin, an enzymethat breaks upproteins, requires anacidic environment tobecome active. Duodenum Alkaline digestion takesplace in the upper smallintestine, the duodenum. Enzymes from thepancreas require analkaline environment tobe active. Pancreas and Liver Pancreas releasespancreatic juice,containingbicarbonate, lipases,proteases, andamylase. The liver makes bile,which emulsifies fats.Bile is made fromcholesterol, which ismade in the liver. Small intestine The walls of the smallintestine are lined withmillions of microvilli.This is the site ofnutrient absorption. Small intestines alsoproduce manydigestive enzymes tobreak large polymerscompletely down intomonomers. Digestion and pH Location pH Enzymes Molecules digested Mouth neutral
Amylase Starch Stomach acidic Pepsin (a peptidase) Initial protein digestion Small intestine Basic to neutral Mixture of amylase, peptidases, lipases Digestion of starches, final breakdown of proteins, digestion of lipids. Large intestine Water from digested foodis absorbed in the largeintestine. Bacteria present in thelarge intestine feed onunabsorbed nutrients, andproduce several vitamins. Fecal material is formedfrom fiber and otherundigested material. Digestion Diagram Digestion