protein and lipid digestion Flashcards
define digestion
mechanical and chemical (hydrolysis) break down of nutrients into small, soluble molecules that can be absorbed through the lining if the ileum into the blood
what are the characteristics of the ileum
- Villi + microvilli - large surface area
- One cell thick- Short diffusion distance
give the general steps of breaking down a protein 3
1) denature protein + unravel polypeptide
2) hydrolyse amino acid chains
what enzyme is used in the stomach during protein digestion
what does it do
endopeptidases
hydrolyses peptide bonds between amino acids in the middle of the polypeptide chain
what is the importance of amino acid chains being broken into shorter chains in the stomach
it means there will be more ends to be hydrolysed later on
give features of endopeptidases
optimum ph 2
secreted in inactive form - activated by stomach acid
given in inactive form so it doesn’t digest body + other enzymes
why is the stomach muscular
so it can churn
distributing and mixing endopeptidases
what enzyme is used in protein digestion in the small intestine
and what do they do
exopeptidases
they hydrolyse peptide bonds between specific amino acids at ends of the polypeptide chains
producing dipeptides
what enzyme is used in protein digestion in the lining of the small intestine
dipeptidases
they hydrolyse peptide bonds between dipeptides into amino acids
what is another word for surface cells
epithelium cells
describe pancreatic juice and its role
Ph 8 - slightly alkaline to neutralise stomach acid, deactivate endopeptidases, and allow other digestive enzymes to work
describe gastric juice from stomach and its role
Ph2
activates endopeptidases
kills bacteria
denatures proteins
what is the role of mucus in the stomach
Protects the stomach lining from being digested by the acidic environment and enzymes
describe the structure of an epithelium cell of the ileum
lumen of gut
microvilli boarder
main body of cell
blood capillaries in musoca
describe how amino acids are transported into the cell
Na+ ions diffuse into cell
causing charge which cotransports amino acids into cell with molecules of Na+
how is low Na+ concentration inside of cell maintained in order keep Na+ ions diffusing into cell
they are actively transported out using a sodium potassium pump
maintaining electrochemical concentration gradient
how do amino acids leave cell and move into blood
facilitated diffusion using a transport protein
how is bile prepared before it can pass into epithelium cells
it is emulsified into small lipid droplets using lipases
it is then stored into micelles (small sphere containing bile salts + fatty acids) making fatty acids soluble
