digestion and absorption Flashcards
what are CARBOHYDRATES broken down into?
disaccharides and then monosaccharides (sugars)
what are LIPIDS/FATS broken down into?
fatty acids and glycerol (monoglycerides)
what are PROTEINS broken down into?
amino acids
what are CARBOHYDRATES broken down BY?
amylase and membrane-bound disaccharidases (enzyme)
HOW are CARBOHYDRATES broken down by AMYLASE?
- AMYLASE is an enzyme that catalyses the conversion of STARCH (polysaccharide) into MALTOSE (disaccharide)
- this involves the HYDROLYSIS of the GLYCOSIDIC BONDS in starch
WHERE is AMYLASE produced?
in the salivary glands and the pancreas
HOW are CARBOHYDRATES broken down by MEMBRANE-BOUND DISACCHARIDASES?
- membrane-bound disaccharidases are enzymes attached to the cell membrane of epithelial cells lining the ileum (small intestine)
- they break down disaccharides into monosaccharides
- this involves the hydrolysis of glycosidic bonds
what is MALTOSE catalysed by?
maltase
what is SUCROSE catalysed by?
sucrase
what is LACTOSE catalysed by?
lactase
what are the MONOSACCHARIDE PRODUCTS of MALTOSE?
glucose + glucose
what are the MONOSACCHARIDE PRODUCTS of SUCROSE?
glucose + fructose
what are the MONOSACCHARIDE PRODUCTS of LACTOSE
glucose + galactose
what are LIPDS broken down BY?
lipase and bile salts
HOW are LIPIDS broken down by LIPASE?
- LIPASE enzymes catalyse the breakdown of LIPIDS into MONOGLYCERIDES (glycerol) and FATTY ACIDS
- this involves the HYDROLYSIS of ESTER BONDS in lipds
where is LIPASE made?
pancreas
where does LIPASE WORK?
small intestine
where does AMYLASE WORK?
mouth and small intestine
HOW do BILE SALTS help in the breakdown of LIPIDS?
- BILE SALTS emulsify lipids = cause lipids to form small droplets
- bile salts increase the available surface area for lipase to work on as small lipids droplets have a LARGER surface area than one big lipid droplet
where are BILE SALTS produced?
liver
what are PROTEINS broken down BY?
endopeptidases and exopeptidases (proteases/peptidases)
what are PEPTIDASES?
enzymes that catalyse the conversion of PROTEINS into AMINOA CIDS by HYDROLYSING the PEPTIDE BONDS between amino acids
how are PROTEINS broken down by ENDOPEPTIDASES?
ENDOPEPTIDASES hydrolyse peptide bonds WITHIN a protein
how are PROTEINS broken down by EXOPEPTIDASES?
- EXOPEPTIDASES hydrolyse peptide bonds AT THE END of protein molecules
- they remove single amino acids from proteins
what are 3 examples of ENDOPEPTIDASES?
TRYPSIN, PEPSIN, CHYMOTRYPSIN
where are TRYPSIN and CHYMOTRYPSIN synthesised and secreted to?
they are SYNTHESISED in the PANCREAS and SECRETED to the SMALL INTESTINE
where is PEPSIN produced and released to?
pepsin is PRODUCED by cells in the STOMACH LINING and is RELEASED into the STOMACH
what CONDITIONS does PEPSIN work in?
pepsin ONLY works in ACIDIC CONDITIONS which is provided by HYDROCHLORIC ACID in the stomach
what are DIPEPTIDASES?
- DIPEPTIDASES are exopeptidases that work on DIPEPTIDES
- they separate 2 amino acids that make up a dipeptide by HYDROLYSING the PEPTIDE BONDS between them
where are DIPEPTIDASES located?
the CELL-SURFACE MEMBRANE of EPITHELIAL CELLS in the SMALL INTESTINE
how are GLUCOSE and GALACTOSE absorbed across cell membranes?
glucose and galactose are absorbed by ACTIVE TRANSPORT with SODIUM IONS via a CO-TRANSPORTER PROTEIN
how is FRUCTOSE absorbed across cell membranes?
fructose is absorbed via FACILITATED DIFFUSION through a DIFFERENT transporter protein to glucose and galactose
how are MONOGLYCERIDES and FATTY ACIDS absorbed across cell membranes?
- MICELLES help to move monoglycerides and fatty acids towards the epithelium
- micelles constantly break up and reform so can release monoglycerides and fatty acids
- micelles are NOT taken across the epithelium
- monoglycerides and fatty acids are LIPID-SOLUBLE so can diffuse directly across the epithelial cell membrane
how are AMINO ACIDS absorbed across cell membranes?
- amino acids are absorbed via CO-TRANSPORT
- SODIUM IONS are ACTIVELY TRANSPORTED out of the ileum epithelial cells into the blood
- this creates a sodium ion CONCENTRATION GRADIENT
- sodium ions can then DIFFUSE from the lumen of the ileum into the epithelial cells through SODIUM DEPENDENT TRANSPORTER PROTEINS, carrying the amino acids with them