Digestion Flashcards
What is digestion?
Is a process in which relatively large, insoluble biological molecules in food (such as starch, proteins) are hydrolysed into smaller, soluble molecules that can be absorbed across the cell membranes into the bloodstream and delivered to cells in the body.
What do enzymes do during digestion?
They catalyse the hydrolysis.
What are the soluble molecules used for?
Either to provide cells with energy (via respiration) or to build other molecules for cell growth, repair, and function.
The human digestive system includes the following:
Glands - the salivary glands and glands in the pancreas produce digestive juices.
The stomach and small intestine - the sites of digestion
The liver - produces bile.
Small intestine - the site of absorption
Large intestine - site of water reabsorption
What is the function of the mouth?
Contains teeth which break food into smaller pieces and increase its surface area to volume ratio.
The food is shaped into a bolus (ball) by the tongue and lubricated in saliva so it can be swallowed easily.
(Carbohydrate digestion starts here)
What is the function of the oesophagus?
A hollow tube with muscular walls through which food passes from the mouth to the stomach.
Contractions of the smooth wall of the oesophagus help the food to move down towards the stomach.
What is the function of the stomach?
(Protein digestion starts here)
Glandular tissues produce enzymes and stomach acid.
Muscular tissue churns food, mixing it with enzymes and acids.
The purpose of acid during digestion
The acid helps to unravel proteins to enable enzyme activity, as well as lowering the pH which is optimal for stomach enzymes to work.
A lower pH is detrimental to many types of microorganisms which may be present in food.
What is the function of the small intestines?
Soluble food molecules are absorbed into the bloodstream across the wall of the small intestine (by diffusion and active transport) - mainly in the jejunum and ileum.
Water function also occurs here.
The three sections that the small intestine is divided into.
Duodenum, the jejunum and the ileum.
Adaption of the small intestine
Wall of small intestine contains smooth muscle tissue - which rhythmically contracts to move food along.
Why is the ileum long and lined with finger-like vili
To increase the surface area over which absorption can take place.
What is the space in which food passes?
The lumen
The function of the duodenum
Carbohydrate, protein and lipid digestion occurs mainly here.
What is the function of the large intestine?
Any water remaining in food that was not able to be digested (such as cellulose, found in plant fibre) is absorbed here, along with vitamins and minerals.
