Human Nutrition Flashcards
Explain the process of Physical Digestion
Physical digestion (sometimes referred to as mechanical digestion) is the breakdown of food into smaller pieces without chemical change to the food molecules
The processes that take place during physical digestion help to increase the surface area of food for the action of enzymes during chemical digestion
It is mainly carried out by the chewing action of the teeth, the churning action of the stomach and the emulsification of fats by bile in the duodenum
Explain where is bile produced and stored and its two main roles
Cells in the liver produce bile which is then stored in the gallbladder
Bile has two main roles:
It is alkaline to neutralise the hydrochloric acid which comes from the stomach
The enzymes in the small intestine have a higher (more alkaline) optimum pH than those in the stomach
It breaks down large drops of fat into smaller ones. This is known as emulsification. The larger surface area allows lipase to chemically break down the lipid into glycerol and fatty acids faster
Where is amylase produced and what its role
Amylases are produced in the mouth and the pancreas (secreted into the duodenum)
Amylases digest starch into smaller sugars
Define Proteases
Proteases are a group of enzymes that break down proteins into amino acids in the stomach and small intestine (with the enzymes in the small intestine having been produced in the pancreas)
Define Lipases and its roles
lipase enzymes are produced in the pancreas and secreted into the duodenum
They digest lipids into fatty acids and glycerol
How is a low pH helpful in the stomach?
The low pH kills bacteria in food that we have ingested as it denatures the enzymes in their cells, meaning they cannot carry out any cell reactions to maintain life
Pepsin, produced in the stomach, is an example of an enzyme which has a very low optimum pH - around pH 2
The hydrochloric acid produced in the stomach ensures that conditions in the stomach remain within the optimum range for pepsin to work at its fastest rate
Where is amylase secreted?
Amylase is secreted into the alimentary canal in the mouth and the duodenum (from the pancreas) and digests starch to maltose (a disaccharide)
Where is Maltose digested?
Maltose is digested by the enzyme maltase into glucose on the membranes of the epithelium lining of the small intestine
Where does the protein digestion takes place
Pepsin is produced in the stomach and breaks down protein in acidic conditions
Trypsin is produced in the pancreas and secreted into the duodenum where is breaks down protein in alkaline conditions
Explain the function of villi
Microvilli on the surface of the villus further increase surface area for faster absorption of nutrients
Wall of the villus is one cell thick meaning that there is only a short distance for absorption to happen by diffusion and active transport
Well supplied with a network of blood capillaries that transport glucose and amino acids away from the small intestine in the blood
Lacteal runs through the centre of the villus to transport fatty acids and glycerol away from the small intestine in the lymph
