Digestion and absorption

Question 1

How does glucose and amino acids move into the small intestine

Answer 1

Moved into the small intestine by co-transport

Question 2

Role of sodium ions

Answer 2

NA+ are actively transported out of epithelial cells lining of the ileum into the blood by sodium potassium pump. This creates a concentration gradient of sodium in the lumen. As a result sodium ions and glucose/amino acids move by facilitated diffusion into the epithelial cell from the lumen via co-transporter protein. This creates a higher concentration gradient of glucose in epithelial cell So glucose moves out of the cell into the blood by facilitated diffusion through a protein channel

Question 3

How are lipids digested

Answer 3

-bile salts are produced in the liver
-Bile salts emulsify lipid to smaller lipid droplets
-Increasing surface area (to volume ratio) of lipids speeds up action of lipases
-Lipase made in the pancreas, released to small intestine
-Lipase hydrolyses lipids → monoglycerides + fatty acids by breaking ester bonds
-Monoglycerides, fatty acids and bile salts stick together to form micelles

Question 4

Describe the mechanism for absorption of lipids by the cells lining the
ileum.

Answer 4

-Monoglycerides and fatty acids diffuse out of micelles (in lumen) into epithelial cell. Because lipid soluble

-Monoglycerides and triglycerides recombine to triglycerides which aggregate into globules

-Globules coated with proteins to form chylomicrons

-Leave via exocytosis and enter lymphatic vessels

-Return to blood circulation

Question 5

Importance of diffusion in digestion and absorption

Answer 5

If glucose doesn’t diffuse out of the cell by facilitated diffusion into the blood then glucose can be used by the body for aerobic respiration. This is because there won’t be any glycolysis of glucose if glucose is not present. in turn this effects metabolic processes as glucose is needed for aerobic respiration in order for mitochondria to make ATP to release energy for processes such as the co-transport of glucose itself and to move substances against concentration gradient.

Question 6

Importance of diffusion in digestion and absorption

Answer 6

If glucose doesn’t diffuse out of the cell by facilitated diffusion into the blood then glucose can be used by the body for aerobic respiration. This is because there won’t be any glycolysis of glucose if glucose is not present. in turn this effects metabolic processes as glucose is needed for aerobic respiration in order for mitochondria to make ATP to release energy for processes such as the co-transport of glucose itself and to move substances against concentration gradient. Also talk about importance of amino acids( in forming proteins such as enzymes)

If lipids are not absorbed into the blood by diffusion then we would lack cell surface membranes as we need fatty acids to form the phospholipid bilayer. These are crucial for cells as they maintain a different environment on each side of the cell or compartmentalisation of cell. Also very important as phospholipid bilayer is needed for phagocytosis as it can bend to take up different shapes to form vesicles