1. Carolyn, Shannon, Pavina, Brittany, Emmelyn
6.1: Digestion
- Digestion-breaking down of large food molecules using enzymes
- Ingestion- intake of food macromolecules
- Absorption- digested food molecules going into the blood through the plasma membrane
- Assimilation- molecules taken up by cells for use and continuing metabolizing
- Excretion-waste products removed from the blood and released as urine
- Egestion- materials not digested
Being that polymers are insoluble, digestion is required in order for the macromolecules to be
broken down and absorbed through the plasma membrane. Hydrolysis occurs to break down
large organic molecules. Digestive enzymes are used in catabolic reactions to break down larger
molecules. Enzymes lower activation energy of reaction which in turn does not require high
temperatures for reaction. Digestion occurs in a series of steps:
- Mouth chews food; saliva moistens food in order to swallow; salivary amylase
chemically digests starch
- Oesophagus pushes food into stomach
- Stomach continues digestion; acid kills bacteria; pepsin begins digestion of proteins
- (duodenum) Small intestine- pancreatic amylase and lipase digest carbohydrates and fats;
trypsin digest polypeptides to amino acids
- (ileum) small intestine- absorbs nutrients into the blood through the villi
- Large intestine- water reclaimed and returned to blood
- Egestion – faeces forced out of the anus
Villi (finger-like projections in small intestine) structures:
- Capillary: carries blood to and fro
- Lacteal-transport fat to circulatory system
- Mitochondria- generate ATP
- Microvilli- Increase surface area for absorption