lipid digestion

• Micelles

  • Vesicles containing fatty acids, glycerol, monoglycerides, and bile salts formed after lipase digests triglycerides. They make fatty acids more soluble in water, assist in carrying fatty acids and monoglycerides to the epithelial cell, and help maintain a higher concentration of fatty acids compared to the epithelial cells of the ilium, aiding in absorption by simple diffusion
• Fatty acids being non-polar

  They are not water-soluble, making it difficult to transport through the solution in the lumen to reach the epithelial cell. Micelles make fatty acids more soluble in water, aiding in their transport to the epithelial cell
• High concentration of fatty acids in micelles compared to the epithelial cells of the ilium

  Essential for aiding the absorption of fatty acids by simple diffusion as they move down their concentration gradients
• How lipids are absorbed into the cells lining the ilium or the epithelial cells

  Fatty acids end by simple diffusion down their concentration gradient because they are non-polar and lipid-soluble, able to dissolve in the phospholipid bilayer of the cell membrane, and move in by simple diffusion. This explains how lipids are absorbed into the cells lining the ilium or the epithelial cells
• What happens once lipids are in the epithelial cell

  Fatty acids, monoglycerides, and glycerol need to be reassimilated into triglycerides, which can happen in the smooth endoplasmic reticulum or the Golgi body. Triglycerides may combine with a protein to form a chylomicron in the Golgi body or reform as triglycerides in the smooth endoplasmic reticulum
• How modified lipids leave the epithelial cell and are transported around the body

  Processed triglycerides or chylomicrons are released in a vesicle, which fuses with the cell membrane through exocytosis. The released vesicles are then absorbed by lacteals, lymphatic vessels, and transported around the body until reaching a blood vessel near the vena cava to re-enter the bloodstream
• Common exam questions linked to lipid absorption and transport
• Key marking points for describing how digested lipids are absorbed and transported to the ilium and the lymphatic system
• Importance of my cells in absorbing lipids into the epithelial cells of the ilium
• Vesicles are removed by exocytosis

  One option of a five mark question
• Importance of my cells in absorbing lipids into the epithelial cells of the ilium

  1. My cells are made of bile salts, fatty acids, monoglycerides, glycerol

  2. My cells make the fatty acids more soluble in water

  3. My cells carry the fatty acids to the epithelial cells of the ilium

  4. Fatty acids are absorbed into the cell by simple diffusion
• When lipids are digested

  1. First form smaller droplets

  2. Then my cells are formed
• Advantages of smaller droplets in lipid digestion

  • Increases surface area available for lipase to act on
  • Speeds up hydrolysis or digestion
• Advantages of my cells in lipid digestion

  • Bring fatty acids or monoglycerides and glycerol to the epithelial cell
  • Fatty acids are absorbed into the cell by simple diffusion
• Golgi apparatus involvement in the absorption of lipids

  1. Modifying triglycerides

  2. Combining proteins with triglycerides to make chylomicrons

  3. Packaging into vesicles for release by exocytosis
• Lipid digestion

  Lipase is produced in the pancreas and secreted into the duodenum and ilium. It breaks the Ester bonds between the glycerol and the three fatty acids in triglycerides. Bile salts, produced in the liver, emulsify lipids to form micelles, increasing the surface area for lipase to act on and enhancing the rate of digestion
• Micelle

  • Vesicles containing fatty acids, glycerol, monoglycerides, and bile salts formed after lipase digests triglycerides. They make fatty acids more soluble in water, assist in carrying fatty acids and monoglycerides to epithelial cells, and help maintain a higher concentration of fatty acids outside the epithelial cells compared to inside, aiding absorption by simple diffusion
• How fatty acids end by simple diffusion

  Non-polar fatty acids are lipid-soluble and can dissolve in the phospholipid bilayer of the cell membrane made up of phospholipids. This allows the fatty acids to move in by simple diffusion down their concentration gradient, aiding in the absorption of lipids into the epithelial cells lining the ilium
• Reassimilation of lipids in epithelial cells

  Fatty acids, monoglycerides, and glycerol in the epithelial cell need to be reassimilated into triglycerides. This process occurs in the smooth endoplasmic reticulum or the Golgi body, especially if the triglyceride is to be combined with a protein to form a chylomicron
• Transport of modified lipids out of epithelial cells

  Processed triglycerides or chylomicrons are released in vesicles, which move towards the cell membrane, fuse with it, and get released by exocytosis. These lipids are then absorbed by lacteals, lymphatic vessels, and transported around the body until they reach a blood vessel near the vena cava for re-entry into the bloodstream
• Common exam questions

  • Describe how digested lipids are absorbed and transported to the ilium and the lymphatic system. 2. Describe the importance of my cells in absorbing lipids into the epithelial cells of the ilium
• My cells are made up of biosol adults, fatty acids, and monoglycerides
• My cells carry the fatty acids to the epithelial cells of the ilium
• My cells make the fatty acids more water-soluble
• Fatty acids are absorbed into the cells of the ilium by simple diffusion
• Triglycerides or chylomicrons are formed after absorption
• Vesicles containing processed triglycerides or chylomicrons are released by exocytosis
• Processed lipids are absorbed by lacteals for transport in the lymphatic system
• Modified lipids are transported around the body until they reach a blood vessel near the vena cava for re-entry into the bloodstream
• Vesicles are removed by exocytosis

  One option of a five mark question
• Importance of my cells in absorbing lipids into the epithelial cells of the ilium

  1. My cells are made of bile salts, fatty acids, monoglycerides, glycerol

  2. My cells make the fatty acids more soluble in water

  3. My cells carry the fatty acids to the epithelial cells of the ilium

  4. Fatty acids are absorbed into the cell by simple diffusion
• When lipids are digested

  1. They first form smaller droplets

  2. Then my cells are formed
• Advantages of smaller droplets in lipid digestion

  Increases the surface area available for lipase to act on, speeding up hydrolysis or digestion
• Advantages of my cells in lipid digestion

  1. My cells bring the fatty acids or the monoglycerides and glycerol to the epithelial cell

  2. Fatty acids are absorbed into the cell by simple diffusion
• How Golgi apparatus are involved in the absorption of lipids

  1. Golgi apparatus modify triglycerides

  2. Combine proteins with triglycerides to make chylomicrons

  3. Package into vesicles for release by exocytosis