6.1 Digestion Flashcards
Explain why digestion of large food molecules is essential
Foods are made up of large complex biological polymer molecules. These tend to be insoluble and chemically inert. Therefore, we must break them down into soluble products, so that they can be absorbed, transported and reassembled into new products.
Explain the need for enzymes in digestion
Enzymes allow the digestive process to occur at body temperature (37C in humans) and at a sufficient speed to meet the organism’s survival requirements.
State the enzyme type of Salivary Amylase
Amylase
State the source of Salivary Amylase
Salivary glands
State the substrate of Salivary Amylase
Starch
State the products which Salivary Amylase produces
Maltose
State the optimal pH for Salivary Amylase
pH ~7 (neutral)
State the enzyme type of Pepsin
Protease
State the source of Pepsin
Secreted by chief cells in stomach lining. Found in gastric juices (stomach).
State the substrate of Pepsin
Large polypeptides
State the products which Pepsin produces
Smaller peptides and amino acids
State the optimal pH for Pepsin
pH ~2 (highly acidic)
State the enzyme type of Pancreatic Lipase
Lipase
State the source of Pancreatic Lipase
Pancreas
State the substrate for Pancreatic Lipase
Tryglycerides
State the produces which Pancreatic Lipase produces
Glycerol + Fatty acid chains
State the optimal pH for Pancreatic Lipase
pH ~8 (slightly alkaline)
State the two major organ groups associated with human digestion
Alimentary Canal and Accessory Organs
Describe the Alimentary Canal
Contains organs through which the food actually passes (esophagus, stomach, small intestine, large intestine, etc.)
Describe the Accessory Organs
Organs that assist in digestion but no food passes through them (liver, pancreas, gall bladder, salivary glands, etc.)
Outline the function of the stomach
Breaks down food into a liquidly mixture called chyme. Secretes HCL to kill off bacteria which could cause food poisoning. Secretes pepsin for protein digestion. Provides optimum pH for pepsin. Slowly empties that chyme into the small intestines.
Outline the function of the small intestine
Final stages of digestion occur. All soluble food substances (e.g. nutrients) are absorbed into the bloodstream.
State the three sections of the small intestine
Duodenum
Jejunum
Ileum
Outline the function of the Duodenum
Food particles broken down into soluble components. Sodium bicarbonate neutralises stomach acid in the chyme. Bile emulsifies large fat droplets into smaller droplets, increasing their surface area, pancreatic lipase breaks them apart.
Outline the function of the Jejunum
Majority of absorption occurs. Lined with villi, which are in turn lined with microvilli. These absorb nutrients into the blood via active transport, maximizing absorption.
Outline the function of the Ileum
Absorbs bile salts, vitamin B12, and whatever usable products of digestion were not absorbed by the jejunum
Outline the function of the large intestine
Absorbs water. Converts what remains from fluid state to semi-solid faeces. Faeces stored in rectum and eliminated out the anus.
Define absorption
Movement of fluid or dissolved substance across a membrane. Soluble products of digestion are absorbed into bloodstream, or the lymphatic system in the case of lipids.
Define assimilation
When food products become part of the body’s tissue. Products of digestion are absorbed into cells from the blood to be stored or used within cells/tissues.
State 6 of the features of the villus which are related to their roles in absorption and transport of products of digestion
Microvilli Rich capillary networks Single-cell epithelial layer Lacteals Intestinal crypts Mitochondria
(MRS LIM)
Explain how microvilli assist the villus in the absorption and transport of products of digestion
Greatly increase the surface area of the villus, allowing for a greater rate of absorption.
Explain how the rich capllary network assists the villus in the absorption and transport of products of digestion
Help to maintain a concentration gradient for absorption by rapidly transporting absorbed products away.
Explain how the single epithelial layer assists the villus in the absorption and transport of products of digestion
Ensures minimal diffusion distancebetween the intestinal lumen and capillary network.
Explain how the lacteals assist the villus in the absorption and transport of products of digestion
Absorb lipids from the intestine into the lymphatic system (which are later reabsorbed back into normal circulation).
Explain how intestinal crypts assist the villus in the absorption and transport of products of digestion
Located between villi and release juices that act as a carrier fluid for nutrients.
Explain how mitochodria assist the villus in the absorption and transport of products of digestion
Produce sufficient ATP to enable active transport into cells (contents then passively diffuse into bloodstream).
