Digestion and absorption

• Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels.

  1. Micelles contain bile salts and fatty acids;

  2. Makes fatty acids more soluble in water

  3. Fatty acids absorbed by diffusion;

  4. Triglycerides reformed in cells and chylomicrons form;

  5. Vesicles move to cell membrane;
• Describe the structure of proteins

  1. Structure is determined by relative position of amino acid interactions;

  2. Primary structure is sequence of amino acids;

  3. Secondary structure formed by hydrogen bonding between amino acids;

  4. Tertiary structure formed by interactions between R groups;

  5. Creates active site in enzymes

  6. Quaternary structure formed by interactions and bonds between polypeptides;
• Explain the function of this ATP hydrolase

  1. ATP to ADP + Pi releases energy;

  2. Energy allows ions to be moved against a concentration gradient
• The movement of Na+ out of the cell allows the absorption of glucose into the cell lining the ileum. Explain how.

  1. Maintains a concentration gradient for Na+ from ileum into cell;

  2. Na+ moving in by co transport, brings glucose with it
• Describe the role of micelles in the absorption of fats into the cells lining the ileum.

  1. Micelles include bile salts and fatty acids;

  2. Make the fatty acids more soluble in water;

  3. Carry fatty acids to lining of the ileum;

  4. Maintain higher concentration of fatty acids to

  lining of the ileum;

  5. Fatty acids absorbed by diffusion;
• Describe the role of enzymes in the digestion of proteins in a mammal.

  1. Hydrolysis of peptide bonds;

  2. Endopeptidase hydrolyses peptide bonds in the middle of polypeptide and produces shorter polypeptides

  3. Exopeptidases hydrolyses peptide bonds at the end of polypeptide and produces dipeptides

  4. Dipeptidase hydrolyses the peptide bond on dipeptide and produces single amino acids
• Name the process by which fatty acids and glycerol enter the intestinal epithelial cell.

  Diffusion
• Explain the advantages of lipid droplet and micelle formation.

  1. Droplets increase surface areas for lipase action;

  2. So faster hydrolysis of triglycerides;

  3. Micelles carry fatty acids and glycerol through membrane to intestinal epithelial cell;
• How is the Golgi apparatus involved in the absorption of lipids

  2. Modifies and processes triglycerides;

  3. Combines triglycerides with proteins;

  4. Packaged for exocytosis
• Cells lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions. Explain how.

  1. Sodium ions actively transported from ileum cell to blood;

  2. Maintains diffusion gradient for sodium to enter cells from gut and with it, glucose;

  3. Glucose enters by facilitated diffusion with sodium ions;
• Maltose is hydralysed by the enzyme maltase

  Explain why maltase catalyses only this reaction

  
  

  1. Active site of maltase has a specific active site complementary to maltose
  2. So only maltose can fit
  3. To form an enzyme-substrate complex