IB Biology - Topic 6.1 + D.2: Digestive System

outline the process of digestion

explain why digestion is necessary

• large molecules need to be digested before the nutrients can be absorbed

• polymers are insoluble and are required to be dissolved in a solution

• macromolecules can be reassembled and assimilated to be useful to the human body

explain how food molecules are split

hydrolysis

explain why enzymes have a role in digestion

glands release enzymes into the gut that are used in catabolic reactions (breaking down molecules)

draw and label the digestive system

outline the process of digestion (mouth)

mechanical digestion crushed the food; salivary glands (an exocrine gland) secretes saliva which moistens the food to make a bolus for swallowing; salivary amylase beings the chemical digestion of starch

outline the process of digestion (esophagus)

peristalsis, wave of muscle contractions, pushes the bolus into the stomach

outline the process of digestion (stomach)

muscle contractions continue to mix the food; the acid in the stomach (hydrochloric acid) kills bacteria; pepsinogen secreted by the gastric cells is turned into pepsin in the presence of the acid and begin the digestion of proteins

outline the process of digestion (duodenum, small intestine)

bile is secreted into the duodenum from the liver/gall bladder; acid from the stomach is neutralized and fats are emulsified into small droplets for easier reactions; pancreatic amylase and lipase digest carbohydrates and fats

outline the process of digestion (ileum, small intestine)

absorbs nutrients into the bloodstream via villi

outline the process of digestion (large intestine)

water is reclaimed back into the bloodstream; feces stored in the rectum

outline the process of digestion (egestion)

poop

name the 4 digestive exocrine glands

1. salivary glands

2. pyloric glands (stomach)

3. pancreas

4. liver

explain why the exocrine glands contain so much rough ER and Golgi apparatus

mass synthesis of enzymes for digestion

draw and label a diagram of an exocrine cell

explain the role of hydrochloric acid in the stomach

lowers the pH to around 2 to kill bacteria and denature proteins

explain the parts of the stomach that aid it in digestion

muscular walls that contract to mix food and enzymes, stretching of muscles also triggers enzyme secretion; gastric pits release gastric acid and mucus; muscular sphincters control entry and exit of chyme

list the pancreatic enzymes that are release into the small intestine

1. pancreatic amylase: breakdown of carbohydrates into monomers of glucose

2. pancreatic lipase: breakdown of lipids into monomers of fatty acids and monoglycerides

3. pancreatic trypsinogen: digests proteins into monomers of free amino acids

explain the reason for villi

villi are projections that increase the surface are for maximum absorption

explain why rich blood supply in the villi is important

to create concentration gradients for molecules to diffuse through

outline how the ileum absorbs molecules

active transport; the epithelial cells of the ileum pump sodium ions into the lumen of the small intestine, maintaining a concentration gradient; passively, reentry of sodium is accompanied by nutrients; these nutrients pass through the epithelial cells and enter the capillaries

outline the control of digestive juice secretion

1. combination of nervous and hormonal control

2. food in stomach stimulates stretch receptors (nervous) that triggers gastrin (hormone) into the bloodstream to produce HCl

3. chyme in the small intestine triggers release of secretin (hormone) that triggers secretion by liver and pancreas

draw and label a villus and microvillus cell

explain the significance of lacteals

allow glycerol and fatty acids to be easily absorbed (lipids)

explain what vitamins are

organic compounds that cannot be synthesized in the body; some water soluble some lipid soluble

explain what minerals are

inorganic elements; all water soluble

draw and label a diagram of a section of ileum

outline the functions of the colon (large intestine)

1. maximize surface area for absorption of water + vitamins

2. store feces temporarily

3. secrete mucus for lubrication to push feces

4. produce good bacteria

list some benefits of fiber rich diets

1. reduce huger

2. aids peristalsis

3. clears out waste products

4. prevent constipation

5. reduce risk of appendicitis, cancer, + hemorrhoids

6. slows rate of sugar absorption

outline the different types of membrane transport used in the absorption of digested food