Question

b. State the summary of digestion occurringin the mouth & stomach under the followingheadings (5)
Source Gland, Secretions, Enzymes,
Substrate, and Product of digestion​

Answer 1

DIGESTION IN MOUTH:

• The buccal cavity of mouth possesses three major pairs of salivary glands namely parotid , sub maxillary or sub mandibular and sublingual gland.

• They secrete enzyme, bicarbonate, sodium ions , IgA and mucus.

• They secrete enzyme called salivary amylase or ptyalin.

• The enzyme converts 30% of ingested starch into maltose.

• The substrate is starch and the digested product is maltose.

DIGESTION IN STOMACH:

• The partially digested food called bolus reach stomach from mouth through oesophagus by peristaltic movement.

• The three types of cells in stomach are zymogen or peptic or chief cells, parietal or oxyntic cells and neck cells.

• Parietal cells secrete HCl (hydrochloric acid). It kills the ingested bacteria.

• Neck cells secrete mucus which prevents the damage of stomach wall due to the acidity of HCl.

• Peptic cells secrete two type of enzymes namely pepsinogen and rennin.

• Pepsinogen is an inactive proenzyme which is converted into active enzyme pepsin by HCl.

• Pepsin converts protein into peptides and peptones.

• Rennin converts soluble milk protein caesinogen into insoluble caesin.

• Stomach also secrets a negligible amount of lipase which converts fat or lipids into fatty acid and glycerol.