Topics 4-5:- Enzymes and Digestive system

Catalyst

A substance that increases the rate of a chemical reaction without being used up

Enzyme

Protein molecule that functions as a biological catalyst without being used up

Properties of enzymes

They are protein in nature

They are biological catalysts

intercellular enzymes

Enzymes working inside the cells

extracellular enzymes

Enzymes working outside the cells

Factors affecting enzymes

Temperature

pH

Temperature (graph)

collisions between enzyme and substrate due to higher kinetic enegry so more enzyme substrate complex.

after optimum temp

At high temperature the enzymes get denatured, the active site changes shape so its no longer complementary to the substrate so no more enzyme substrate complex

Absorption

the movement of small soluble molecules and ions through the walls of the ileum(small intesntine) and into the blood

Physical\mechanical digestion

break down of food into small pieces without chemical change to increase the surface area for enzymes to work faster

Chemical digestion

break down of large insoluble molecules to small soluble ones using enzymes to be easily absorbed into the blood

why fibre important in the human diet?

stimulates peristalsis

reduce risk of constipation

reduce risk of colon cancer

Muscular walls of the stomach

strong muscular walls that contract and relax to churn food (mechanical digestion)

Gastric juice

(pepsin) breaks down proteins into amino acids

works best in acidic conditions

hydrochloric acid: provides acidic conditions needed for action of pepsin

kills bacteria by denaturing their enzymes

duodenum

emulsification of fat

change ph of food coming from the stomach from ph 2 to ph 9

Bile juice

produced from liver, stored in gallbladder and enter in the duodenum through bile duct

Bile salts

Causes emulsification of large fat globules into small droplets giving greater surface area to be digested by lipase into fatty acids and glycerol

Pancreatic juice

Produced in the pancreas and enters the duodenum through pancreatic duct

APL

amylase: breaks down starch into maltose

hydrogen carbonate: it is an alkaline that helps neutralize acid coming from the stomach

protease (trypsin): breaks proteins to amino acids (polypeptides)

lipase: breaks fats into fatty acids and glycerol

chemical digestion

Ileum adaptation

Have villi which has a long finger like projection to provide larger surface area for faster rate of absorption

Villi adaptation

epithelium cells are one cell thick for shorter distance of diffusion of digested food molecules

Capillaries: rich in blood supply to transport vitamins, glucose, minerals, amino acids and water to the liver through the hepatic portal vein

Lacteal: transports fatty acids and glycerol through lymphatic system

Epithelium cells have lots of mitochondria in their wall to provide energy needed for active transport through respiration

epithelium cells have microvilli which has a long finger like projection to provide larger surface area for faster rate of absorption by diffusion or active transport

Colon

more water and salts are reabsorbed by osmosis

rectum

storage of faeces

anus

egestion of undigested food as faeces by perisatisis

How does cholera cause diarrhea

The bacteria releases toxins which stimulates the lining of the intestine to secrete chloride ions in the lumen of the ileum lowering the water potential so water will move out of blood and into the lumen of ileum by osmosis

side effects of diahrrea and treatment

Dehydration, loss of ions, loss of water and death

treatment: giving oral rehydration therapy and antibiotics

Enzyme: amylase

Found in mouth (saliva) and pancreas

breaks down starch (substrate) to maltose (product)

Enzyme: Pepsin

Found in stomach.

breaks down protein (substrate) to amino acids (product)

Enzyme:lipase

Found in pancreas

breaks down lipids\fats (substrate) to fatty acids and glycerol (product)

Enzyme:protease

Found in stomach, pancreas and ileum

breaks down protein (substrate) to amino acids (product)

Enzyme: maltase

found in ileum

breaks down maltose (substrate) to glucose (product)