3.3.3 Digestion And Absorption Flashcards
2 substances formed when 2 amino acids join together
Dipeptide
Water
How does a change in the primary structure of a globular protein cause a different 3D structure?
Sequence of amino acids is changed causing change in tertiary structure
Hydrogen bonds/ionic/disulfide form in different places
During an experiments when 2 visking tubing (partially permeable) tubes contains equal concentrations of starch and amylase were placed in a water bath. How would a solution with a PH of 8 be contain more liquid than one with a lower pH of 2 after being left for a while?
The starch is hydrolysed into maltose faster which lowers the water potential allowing water to enter via osmosis
The addition of a respiratory inhibitor stops the absorption of amino acids. Explain why.
Respiratory inhibitors reduce the amount of ATP released during respiration meaning ATP isn’t available for active transport so the amount of sodium ions increase in the cell. So no diffusion gradient for sodium to move into cell with amino acid.
Formation and role of micelles in absorption of lipids
Lipid broken down by lipase
Produces monoglycerides and fatty acids
Stick to bile salts forming micelles
Enable products to transported to small intestine surface for absorption
Micelle breaks down + components absorbed by simple diffusion
Explain the advantages of lipid droplet and micelle formation.
Droplets increase surface area
So faster hydrolysis of lipids
Micelles carry fatty acids and glycerol through membrane
Suggest how Golgi apparatus is involved in the absorption of
lipids.
Modifies triglycerides
Combines triglycerides with proteins
Packaged for release
Endopeptidase
In stomach
Hydrolyses internal peptide bonds
Proteins to peptides
Exopeptidase
Hydrolyse terminal peptide bonds
Peptides to dipeptides
Absorption of glucose and amino acids
Glucose or amino acid moves into epithelium cell with sodium ion Using a carrier protein
Sodium ions moves down concentration gradient
Sodium ions actively transported out of epithelium cell into blood Potassium ions move in opposite direction
Maintaining low concentration of sodium ions in epithelial cell Glucose/amino acids diffuse into blood using a protein
Absorption of triglycerides
Fatty acids and monoglycerides diffuse across phospholipid membrane Transported to ER
Triglycerides reformed
Transferred to Golgi apparatus
Combined with cholesterol and lipoprotein To form chylomicrons
Move out of epithelial cells
By exocytosis
Into lacteals in centre of villus
Digestion of lipids
Bile salts From liver/gall bladder Emulsifies lipid into micelles Increase surface area for lipase to work on Lipase From pancreas Hydrolyses ester bonds Lipid to fatty acids and monoglycerides
Digestion of starch
Amylase Hydrolyses alternate glyosidic bonds Starch to maltose In mouth and small intestine Maltase Membrane bound disaccharidase on small intestine Hydrolyses maltose to glucose
