the components of the digestive system carry out mechanical and chemical digestion.
Mechanical digestion is the physical breaking up of food into smaller pieces.
Chemical digestion is the chemical breakdown of large insoluble food molecules into smaller soluble food molecules using digestive enzymes.
Each structure in the body has its function:
stomach - a large muscular bag that churns food and releases hydrochloric acid and pepsin (protein) for digestion. This is mechanical and chemical digestion.
mouth - where food is chewed and mixed with saliva. This is mechanical and chemical digestion.
salivaryglands - secretesaliva containing the salivary amylase which is a carbohydrase. This is chemical digestion.
oesophagus - through which food is moved from the mouth to the stomach. This is nodigestion.
liver - makes bile.Not a digestion.
Gall bladder
Stores bile. No digestion.
Small intestine - ileum
Absorbs the small soluble of food digestion into the bloodstream. This is chemical digestion.
Small intestine - duodenum
Bile and enzymes are released here for digestion. This is chemical digestion.
Large intestine
Absorbs water from food. No digestion.
Pancreas
Releases proteases, carbohydrases, and lipases into the duodenem. This is chemical digestion.
Rectum
Where feces are compacted and temporarily stored. No digestion.
Anus
Where fecesleave the digestive tract. No digestion.
Peristalsis:
food is moved through the digestivesystem through peristalsis; a wave of muscular contraction.
-> movement of the food
Chemical digestion:
a chemicalreaction involving the breaking of bonds through the addition of a watermolecule, using an enzyme.
Enzymes:
enzymes catalyze the hydrolysis of large insoluble food molecules into small soluble food molecules.
there are 3 types of enzymes; lipases, proteases, and carbohydrases.
types of enzymes:
carbohydrases - carbohydrates like starch/food molecules that are produced are sugars e.g. glucose/ the bond that is broken is glycosidic/ enzymes are made in the salivary glands and pancreas/ yet the enzymes digest food in the small intestine and mouth
types of enzymes:
proteases - proteins/ food molecules produced are amino acids/ peptide bonds are broken/ enzymes are made in the stomach and pancreas/ enzymes digest food in the stomach and small intestine
types of enzymes:
lipases - fats e.g lipids/ food molecules produced are fatty acids and glycerol/ ester bonds are broken/ enzymes are made in the pancreas/ enzymes are digested in the small intestine
roles in digestion and how it affects enzyme enzyme-controlledcontrolled digestion:
hydrochloric acid:
gives the stomach a pH of 2
because of this, it activates the stomach enzymes providing the optimum pH for their action.
killing most bacteria on the food
inactivating the salivary amylase
roles in digestion and how it affects enzyme-controlled digestion:
bile:
alkaline pH and neutralizes the stomach acid to provide pH 7 <- optimum pH for small intestine enzymes
emulsifies fats providing a larger surface area for lipase action.
roles in digestion and how it affects enzyme-controlled digestion:
mucus:
protects stomach lining from being digested by protease enzymes
protects stomach from hydrochloric acid burns
lubricates food so it passes down the digestive tract more easily
what is gastrin?
a hormone that is released when a protein is detected in the stomach
stimulates the release of hydrochloric acid and protease enzymes from the cells lining the stomach
promotes contraction from the stomach muscles
relaxes the sphincter muscle bottom of the stomach
this increases the rate of the stomach emptying
increases flow of bile from the gall bladder
Model answer for chemical digestion of proteins:
Proteins are digested by protease enzymes.
They digest proteins into amino acids by catalysing hydrolysis reactions which break the peptide bonds in the protein.
Protease enzymes are made by the stomach and small intestine.
Protein digestion starts in the stomach where the optimum pH of 2 is created by the release of hydrocholric acid.
The digestion is completed in the small intestine, where the optimum pH is created by bile neutralising the hydrochloric acid.