6.10 absorption of the products of digestion

Question 1

increase rate of reaction in the ileum

Answer 1

• microvilli and villi-> increase the surface area for absorption
• very thin walled-> short diffusion pathway
• muscles- maintain diffusion gradients
• blood vessels-> maintain a diffusion gradient

Question 2

absorption of amino acids

Answer 2

• sodium ions are actively transported out of epithelial cell into the blood
• maintains a concentration gradient into the cell
• sodium ions diffuse into cell by facilitated diffusion
• carries amino acids with it which goes against its concentration gradient
• amino acids are move out by facilitated diffusion into the blood

Question 3

absorption of monosaccharides e.g. glucose

Answer 3

• sodium ions are actively transported out of epithelial cell into the blood
• maintains a concentration gradient into the cell
• sodium ions diffuse into cell by facilitated diffusion
• carries glucose with it which goes against its concentration gradient
• glucose are move out by facilitated diffusion into the blood

Question 4

absorption of triglycerides (8)

Answer 4

• monoglycerides and fatty acids combine with bile salts= micelles
• come into contact with epithelial lining of ileum
• breaks down into monoglycerides and fatty acids
• diffuses through membrane
• goes to endoplasmic reticulum and recombined to triglycerides
• goes to Golgi apparatus and associate with cholesterol and lipoproteins= chylomicrons
• move out by exocytosis to lacteals
• goes to bloodstream

Question 5

The epithelial cells that line the small intestine are adapted for the absorption of glucose. Explain how.
[6 marks]

Answer 5

• Microvilli -> increased surface area;
• Many mitochondria -> produce ATP for active transport
• Carrier proteins for active transport;
• Channel / carrier proteins for facilitated diffusion -> Co-transport of sodium (ions) and glucose
• Membrane-bound enzymes digest disaccharides / produce glucose