IB Biology 12 HL

Food molecules are polymers and insoluble. Food molecules must be digested from insoluble to smaller soluble molecules before being absorbed in the blood stream. Polymers are large food molecules that when digested become monomers

Proteins -> amino acids carbohydrates/starch/glycogen -> glucose nucleic acids -> DNA and RNA (both nucleoside tripho, ATP

Amylase: salivary amylase source: mouth substrate: amylose (starch) product: disaccharide maltose pH: 7.5-7.8 (basic) action: hydrolysis of 1-4 glycotic bonds Protease: pepsin source: stomach substrate: polypeptides product: smaller peptides pH: 2 (very acidic) action: endopeptidase Lipase: pancreatic lipase source: pancreas substrate: triglyeride lipids product: fatty acid chains and glycerols pH: 7.2 (basic) action: hydrolysis of lipids into fatty acids and glycerol molecules

The hydrolysis of polypeptides into peptides (polymer to monomer) using enzymes

Bile salts

1. increases the surface area of lipids for the digestion of fats 2. exposes the glycerol "head" structure to the enzyme

See diagram

The hydrolysis of polymers to monomers

Responsible for storing food from meal and beginning protein digestion (a) Lumen of the stomach stores the food from a meal (b) Gastric pits from which mucus, enzymes and acid are secreted (c) Mucus secreting cells. Mucus protects the surface of the stomach from auto-digestion (d) Parietal cells that produce HCL which kills microorganism that enter the digestive system (food & tracheal mucus). This also converts inactive pepsinogen to active pepsin (e) Chief cells: produces pepsinogen a protease enzyme

Responsible for completing digestion and absorbing products of digestion (a) Villus which increase the surface area for absorption of the products of digestion (b) Microvilli border of the epithelial cell increases the surface are for absorption. (c) Lacteals are connect to the lymphatic system for the transport of lipids. (d) In the wall of the small intestine are the blood vessels to transport absorbed products to the general circulation, There are also the muscle to maintain peristalsis

Responsible for reabsorption of water from the gut (a) The lumen of the colon (b) The mucus producing goblet cells (b) Muscular walls to maintain peristalsis

Insoluble food molecules are digested to soluble products in the lumen of the gut. Absorption:

1. The soluble products are first taken up by various mechanisms into the epithelial cells that line the gut.
2. These epithelial cells then load the various absorbed molecules into the blood stream.

Assimilation:

1. The soluble products of digestion are then transported to the various tissues by the circulatory system.
2. The cells of the tissues then absorb the molecules for use within this tissues