Digestion and absorption Flashcards
what is digestion?
relatively large, insoluble molecules are hydrolysed into smaller, soluble molecules that can be absorbed across the cell membranes into the blood stream and delivered into cells in the body.
what do enzymes do in digestion
catalyse the hydrolysis.
what do the small soluble molecules do?
provide the cells with energy (via resparation)
or build other molecules for cell growth, repair and function.
what do protiens form?
hydrolysed into amino acids
what do carbohydrates form?
hydrolysed into simple sugars
what do lipids form?
hydrolysed into fatty acids.
role of glands?
where are the sites of digestion?
role of small and large intestine?
produce digestive juices - salivary and pancreas has glands
stomach and small intestine - sites of digestion
Small intestine - site of absorbtion
Large intestine - site of water absorbtion
digestion of starch, say enzymes and where it occurs
lumen of gut
starch + amylase -> maltose
maltose + maltase - >
Inside epithelial cells of small intestine
glucose
digestion of proteins say enzymes and where it occurs
lumen of gut
protien + endopeptidase -> polypeptides
polypeptides + exopeptidase ->
inside cell surface membranes of epithelial cell
dipeptides
dipeptides + dipeptidase -> amino acids
digestion of lipids say enzymes and where it occurs
lumen of the small intestine
lipids +bile salts -> emulsified lipids
emulsified lipids + lipase -> fatty acids + glycerol
large fat globule -> emulsification
small fat droplets -> digestion
->fatty acids +glycerol
what does endopeptidase do and what is secreted with endopeptidase?
hydrolyses peptide bonds within polypeptide chains to produce dipeptides.
Hyddrochloric acid.
exopeptidase what does it do?
hydrolyses peptide bonds at the ends of polypeptide chains to produce dipeptides.
what does emulsification do?
increase surface area of fatty droplets for action of digestive enzymes.
absorption of amino acids
specific amino acid co-transport protiens (carrier protiens)
are found within the cell surface membrane of epithelial cells.
This only occurs when sodium ions are present
for every sodium ion ion that is transported into the cell, an amino acid is transported in.
This occurs via facilitated diffusion - movement of molecules down a concentration gradient
the concentration gradient of sodium ions from the lumen of the ileum into the epithelial cell is maintained by the active transport of sodium ions through the sodium-potassium pump at the other end of the cell.
absorption of monosaccharides
glucose carrier protien in the cell surface membrane of the small intestine.
sodium ions and glucose molecules are co-transported through facilitated diffusion.
the concentration gradient of sodium ions is maintained by the active transport of sodium ions in the sodium-potassium pump.
role of micelles in the absorption of lipids
products of lipid digestion:
fatty acids, monoglycerides and glycerol
absorbing these products:
monoglyverides and fatty acids associate with phospholipids and bile salts to form micelles (very small fat droplets)
monoglyverides and fatty acids are not very soluble
micelles break down and add to a pool of fatty acids and monoglycerides that are disolved in the small intestine surrounding epithelial cells.
enter epithelium by diffusion
non-polar
short fatty acid chains, how do they enter the blood?
directly into the blood via diffusion.
longer fatty acids what do they do?
recombine with monoglyverides and glyveriol to form triglycerides in endoplasmic reticulum
these are packaged into lipoprotiens called chylomicrons.
