nutrition in humans

Question 1

what is ingestion?

Answer 1

-the process in which food is taken into the body

Question 2

what is digestion?

Answer 2

-chemical digestion is the hydrolysis of large, insoluble food into smaller, soluble nutrients by enzymes
-physical digestion is the breaking up of food into smaller pieces, which increases the surface area to volume ratio of food, so that enzymes can hydrolyse the food more quickly

Question 3

what is absorption?

Answer 3

-the process which small and soluble nutrients move from the lumen of the alimentary canal into the blood stream surrounding the alimentary canal

Question 4

what is assimilation?

Answer 4

-the process where absorbed nutrients are used to create new protoplasm or used to release energy
-occurs at the liver, eg. detoxification of alcohol

Question 5

what is egestion?

Answer 5

-the process where undigested food/ faeces is removed from the body
-faeces is stored at the rectum, and egested at the anus

Question 6

what happens in the mouth?

Answer 6

physical digestion
-chewing of food by teeth, physically breaks up food into smaller pieces
-smaller food pieces have a larger surface area to volume ratio, which allows enzyme salivary amylase to hydrolyse starch more quickly into maltose

chemical digestion
-salivary amylase in saliva catalyses the hydrolysis of starch into maltose
-optimal pH 7.0 and temperature 37ºC

Question 7

what happens in the oesophagus?

Answer 7

-muscular tube
-rhythmic wave-like contractions of the muscles to mix and propel the contents of the alimentary canal is called peristalsis
-longitudinal muscles on the outer side, circular muscles on the inner side

Question 8

what happens in the stomach?

Answer 8

functions
-temporary storage of food
-carries out physical and chemical digestion
-absorbs alcohol easily

physical digestion
-peristalsis causes food to break up into even smaller pieces

-gastric juice secreted by the stomach contains hydrochloric acid and the inactive pepsinogen

functions of hydrochloric acid
-activates inactive pepsinogen into active pepsin
-creates an acidic optimal pH 2.0 for pepsin
-acidic pH denatures salivary amylase, so starch digestion stops in the stomach

chemical digestion
-pepsin is a protease enzyme that catalyses the hydrolysis of proteins into polypeptides

Question 9

what happens in the small intestine?

Answer 9

functions
-most chemical digestion occurs at the duodenum at the start of the small intestine
-absorption of most nutrients occurs mainly at the ileum at end of the small intestine