Lipid Digestion Absorption of glucose and amino acids from the EXAM QUESTIONS
Lipid digestion is done by lipase enzyme which is secreted by the pancreas. ileum lumen to the blood The epithelial cells that line the small intestine are adapted for absorption of
Lipid digestion takes place in the ileum glucose, explain how (6 marks)
The lipid digestion is aided by bile salts which is produced in the liver. The 1. Na+ move into lumen of the epithelial cell by facilitated
bile salts emulsifies the large lipid droplets into micelles which have a much diffusion through a carrier protein ● Microvilli increases surface area
larger surface area for faster digestion and lipid hydrolysis. The products of 2. This results in a protein shape change so that glucose can be ● Many mitochondria for production of ATP to release energy for active
lipid digestion (monoglycerides and fatty acids) remain associated with the simultaneously brought into the epithelial cells against its transport
micelles. The micelles then travel to and contact with the cell surface concentration gradient (active transport) in a process called ● Carrier proteins for active transport
membrane of the epithelial cells causing them to break apart. co-transport ● Channel proteins for facilitated diffusion
3. Glucose enters the blood by facilitated diffusion through a ● Carrier proteins for the co-transport of glucose and sodium ions (Symport)
Absorption of lipids carrier protein at the base of the cell ● Membrane bound enzymes - disacchardases hydrolyse disaccharide to
4. Na+ are actively transported out of the epithelial cells by a form glucose
carrier protein (the Na+/K+ pump)
● The monoglycerides and fatty acids diffuse through the 5. This removal of Na+ ions maintains the sodium ion
phospholipid bilayer into the epithelial cells of the ileum Suggest and explain 2 ways the cell surface membrane is adapted to allow rapid
concentration gradient needed to maintain the uptake of transport of nutrients: (2marks)
● They then recombine with the SER to form triglycerides which glucose
are then packaged into vesicles and transported to the Golgi Max 2
6. Glucose then moves into the blood by facilitated diffusion via a
apparatus channel protein
● The triglycerides then associate with proteins in the Golgi ● Membrane folded SO increases surface area for FASTER DIFFUSION
apparatus to form chylomicrons ● Large number of channel proteins for facilitated diffusion
● The chylomicrons then leave the Golgi apparatus via vesicles ● Large number of carrier proteins for active transport/co-transport
● The vesicles then fuse with the cell surface membrane at the
base of the epithelial cells
Explain how digestion of starch in the gut leads to an increase in the
● The chylomicrons leave the cell via bulk transport - exocytosis
concentration of glucose in the blood. Details of co-transport are not required. (3
● The chylomicrons then enter the lymphatic system
marks)
● Starch is hydrolysed by amylase/maltase/enzymes
EXAM QUESTIONS ● Produces glucose in the gut
Explain the advantage of lipid droplets and micelle formation (3marks) ● Which is small enough to cross the gut wall/cell membrane into the blood
● The droplets increase the surface area for lipase action
● So FASTER hydrolysis/digestion Suggest a method you could use to estimate the concentration of glucose in
Channel proteins Carrier proteins several different solutions that ALL turned brick red with Benedict’s Reagent in 3
● Micelles carry the fatty acids and monoglycerides through the
cell surface membrane of the intestinal epithelial cells minutes (1 mark)
Only involved in Involved in both facilitated diffusion and active Options:
facilitated transport and cotransport
Describe the role of the Golgi apparatus in the absorption of lipid diffusion and
absorption (3marks) osmosis ● Time how long it takes to go brick red
● Filter off and dry and weigh precipitate
Substance Substance binds to carrier protein then carrier
● Dilute glucose samples, use greater volume of Benedict’s reagent
● Golgi modifies and packages the triglycerides passes through a protein CHANGES SHAPE to transport
● And combines them with proteins water filled pore substance to other side of membrane
● Packaged for release / exocytosis // forms vesicles IGNORE references to colorimeter
Lipid digestion is done by lipase enzyme which is secreted by the pancreas. ileum lumen to the blood The epithelial cells that line the small intestine are adapted for absorption of
Lipid digestion takes place in the ileum glucose, explain how (6 marks)
The lipid digestion is aided by bile salts which is produced in the liver. The 1. Na+ move into lumen of the epithelial cell by facilitated
bile salts emulsifies the large lipid droplets into micelles which have a much diffusion through a carrier protein ● Microvilli increases surface area
larger surface area for faster digestion and lipid hydrolysis. The products of 2. This results in a protein shape change so that glucose can be ● Many mitochondria for production of ATP to release energy for active
lipid digestion (monoglycerides and fatty acids) remain associated with the simultaneously brought into the epithelial cells against its transport
micelles. The micelles then travel to and contact with the cell surface concentration gradient (active transport) in a process called ● Carrier proteins for active transport
membrane of the epithelial cells causing them to break apart. co-transport ● Channel proteins for facilitated diffusion
3. Glucose enters the blood by facilitated diffusion through a ● Carrier proteins for the co-transport of glucose and sodium ions (Symport)
Absorption of lipids carrier protein at the base of the cell ● Membrane bound enzymes - disacchardases hydrolyse disaccharide to
4. Na+ are actively transported out of the epithelial cells by a form glucose
carrier protein (the Na+/K+ pump)
● The monoglycerides and fatty acids diffuse through the 5. This removal of Na+ ions maintains the sodium ion
phospholipid bilayer into the epithelial cells of the ileum Suggest and explain 2 ways the cell surface membrane is adapted to allow rapid
concentration gradient needed to maintain the uptake of transport of nutrients: (2marks)
● They then recombine with the SER to form triglycerides which glucose
are then packaged into vesicles and transported to the Golgi Max 2
6. Glucose then moves into the blood by facilitated diffusion via a
apparatus channel protein
● The triglycerides then associate with proteins in the Golgi ● Membrane folded SO increases surface area for FASTER DIFFUSION
apparatus to form chylomicrons ● Large number of channel proteins for facilitated diffusion
● The chylomicrons then leave the Golgi apparatus via vesicles ● Large number of carrier proteins for active transport/co-transport
● The vesicles then fuse with the cell surface membrane at the
base of the epithelial cells
Explain how digestion of starch in the gut leads to an increase in the
● The chylomicrons leave the cell via bulk transport - exocytosis
concentration of glucose in the blood. Details of co-transport are not required. (3
● The chylomicrons then enter the lymphatic system
marks)
● Starch is hydrolysed by amylase/maltase/enzymes
EXAM QUESTIONS ● Produces glucose in the gut
Explain the advantage of lipid droplets and micelle formation (3marks) ● Which is small enough to cross the gut wall/cell membrane into the blood
● The droplets increase the surface area for lipase action
● So FASTER hydrolysis/digestion Suggest a method you could use to estimate the concentration of glucose in
Channel proteins Carrier proteins several different solutions that ALL turned brick red with Benedict’s Reagent in 3
● Micelles carry the fatty acids and monoglycerides through the
cell surface membrane of the intestinal epithelial cells minutes (1 mark)
Only involved in Involved in both facilitated diffusion and active Options:
facilitated transport and cotransport
Describe the role of the Golgi apparatus in the absorption of lipid diffusion and
absorption (3marks) osmosis ● Time how long it takes to go brick red
● Filter off and dry and weigh precipitate
Substance Substance binds to carrier protein then carrier
● Dilute glucose samples, use greater volume of Benedict’s reagent
● Golgi modifies and packages the triglycerides passes through a protein CHANGES SHAPE to transport
● And combines them with proteins water filled pore substance to other side of membrane
● Packaged for release / exocytosis // forms vesicles IGNORE references to colorimeter
