digestion 3.3.3 Flashcards
name components of digestive system
salivary glands
tongue
epiglottis
oesophagus
liver
stomach
gall bladder
pancreas
duodenum
ileum
colon
rectum
anus
what does saliva consist of
mucin
amylase
mineral salts
peristalsis definition
involuntary contraction or relaxation of muscles
what happens in the oesophagus
peristalsis of the circular muscle contracts and relaxes to push food down
what does the liver do
produces bile
what does bile contain (and function of components)
bile salts - aids digestion of fats
mineral salts - neutralise stomach acid
function of gall bladder
stores bile
function of stomach
produces enzymes
stores and digests food
pancreas function
produces pancreatic juices
ileum structure and function
longest part of small intestine
enzymes produced in wall
inner walls have villi
colon (large intestine) function
absorbs water (via osmosis)
absorbs mineral and vitamins
function of duodenum (first section of small intestine)
receives secretions from the liver and pancreas
further digestion occurs
physical breakdown of food
slicing and chewing action of the teeth
increases surface area for enzyme action
continues with churning action caused by contraction of muscles in the stomach wall
chemical digestion of food
enzyme hydrolyse molecules into smaller soluble molecules
why are multiple enzymes needed for molecules to be chemically digested
enzymes are specific so more than one is needed to hydrolyse a large molecule
one enzyme will hydrolyse a large molecule into sections and then the other will hydrolyse these sections into their monomers
carbohydrases function
hydrolyse carbohydrates ultimately to monosaccharides
lipases function
hydrolyse lipids into glycerol and fatty acids
proteases function
hydrolyse proteins ultimately to amino acids
starch digestion
salivary glands secrete salivary amylase
amylase hydrolyses starch into maltose
duodenum has pancreatic juices which contains pancreatic amylase which hydrolyses starch
peristalsis moves food along the intestine membrane bound maltase
hydrolyses maltose into alpha glucose
what do the mineral salts in salvia do
maintain a pH 7
what do disaccharidase enzymes do
hydrolyses disaccharides into monosaccharides
3 disaccharidase enzymes
sucrase
lactase
maltase
what does sucrase breakdown (and into what)
sucrose to glucose and fructose
what does lactase breakdown
lactose to glucose and galactose
what does maltase breakdown
maltose to alpha glucose
which enzymes break down proteins
peptidases (proteases)
what do endopeptases do
hydrolyse peptide bonds between amino acids in the central region of the molecule
where are endopeptidases found
in the stomach
what do exopeptidases do
hydrolyse the peptide bonds on the terminal amino acids of the peptide molecule to release dipeptidases and single amino acids
where are exopeptidases found
the duodenum
what do dipeptidases do
hydrolyse the bond between the dipeptide to release amino acids
where are dipeptidases found
they are membrane bound
found on epithelial cells lining the ileum
what do lipases do
hydrolyse lipids
where are lipases produced
the pancreas
what do lipases do
hydrolyse the ester bond to form fatty acids and monoglycerides
what is the structure of a monoglyceride
a glycerol with one fatty acid attached
what does bile do
emulsifies large fat droplets to small droplets called micelles
this increases the surface area of the lipids
where are bile salts made
liver
where are bile salts stored
gall bladder
order of lipid digestion
bile emulsifies large lipid globules to small lipid globules
lipase hydrolyses ester bond
forms fatty acids and glycerol
where are sucrase lactase and maltase made
ileum epithelial cells
where does the absorption of hydrolysed products of digestion occur
in the ileum
structure of ileum wall (4)
folded
villi
thin walls
lined with epithelial cells
adaptations of the ileum
villi increase surface area for diffusion
thin wall reduces diffusion pathway
blood vessels carry away absorbed material maintaining the gradient
microvilli increase surface area for absorption
where are microvilli
on the epithelial cells lining the villi on the ileum wall
how are glucose and amino acids absorbed into the epithelial cell
co transport
how are glucose and amino acids moved from the ileum epithelium cell to the blood
facilitated diffusion
explain the transport of amino acids/glucose from the lumen of the ileum into the bloodstream (sodium potassium pump)
1 sodium ions transported out of epithelial cell membrane into the blood via the sodium potassium pump (ATP)
2 this maintains a low concentration of sodium ions inside the epithelial cell compared to the gut lumen
3 sodium ions diffuse down a concentration gradient from the lumen into the epithelial cell by facilitated diffusion
4 brings a glucose/amino acid molecule with it by co transport via carrier protein against concentration gradient
5 glucose/amino acids pass into the blood via facilitated diffusion
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels (5 marks)
Micelles contain bile salts and fatty acids
Maintain higher concentration of fatty acids to cell/lining of the ileum
Fatty acids absorbed by diffusion
Triglycerides formed in cells
Vesicles move to cell membrane
