[HDS] human digestive system Flashcards
what are enzymes?
enzymes are biological catalysts that speed up chemical reactions without undergoing any chemical changes themselves
what is the primary function of enzymes in cells?
enzymes build up and break down complex substances in cells
how are enzymes different from other chemicals involved in reactions?
enzymes are required in minute amounts, and they remain chemically unchanged at the end of the reactions they catalyse
are enzymes specific in their actions?
yes, enzymes are highly specific in action, only catalysis specific chemical reactions
(eg. amylase for starch only, lipase for lipids only)
what happens to enzymes at extreme pH levels?
they lose their shape in a process known as desaturation, which is irreversible
what is the digestive system composed of?
the alimentary canal, the associated organs and glands
name the organs in the alimentary canal
mouth, oesophagus, stomach, small intestine, large intestine, rectum and anus
what are the associated organs and glands?
liver, gall bladder and pancreas
describe the process of digestion
digestion breaks down large, insoluble food substances into small, soluble simple molecules that can be absorbed by body cells
what is the role of the mouth in digestion?
(three roles)
- chewing (physical digestion) breaks food into smaller pieces
- salivary glands produce saliva containing salivary amylase, which digests starch into maltose
- the tongue forms chewed food into a small ball for swallowing
what is peristalsis?
it is a wave-like muscle contraction that propel food along the oesophagus
where does peristalsis occur?
in the oesophagus
what happens in the stomach during digestion?
- gastric glands secrete gastric juice containing hydrochloride acid and pepsin
- pepsin digests proteins into polypeptides
- churning action (physical digestion) mixes food with gastric juices, forming chyme
what is bile?
bile is an alkaline, greenish-yellow liquid
where is bile produced and stored in?
bile is produced in the liver and stored in the gall bladder
what is the role of bile in digestion?
- neutralise acidic chyme from the stomach
- emulsifies lipids, breaking large fat droplets into tiny ones, increasing the rate of lipid digestion
what is pancreatic juice?
pancreatic juice is an alkaline secretion from the pancreas
what enzymes does pancreatic juice contain?
pancreatic amylase, trypsin and pancreatic lipase
what do the walls of the small intestine contain?
it contains glands that secrete digestive enzymes including carbohydrates, peptidase and intestinal lipase
what is the function of the large intestine in digestion?
it absorbs water and mineral salts from undigested matter, forming faeces
where is faeces stored and expelled from?
faeces is stored in the rectum and expelled through the anus in egestion
describe the overall sequence of process in the digestive system
ingestion>digestion>absorption>elimination
what is the purpose of chewing in the mouth during digestion?
it break downs solid food into smaller pieces, increasing the surface area to volume ratio and facilitating digestion by enzymes
how does churning in the stomach contribute to digestion?
it mixes food with gastric juices, which increases the surface area to volume ratio, enhancing the rate of protein digestion by pepsin. a liquid called chyme is produced
