Digestion and Absorption: starch and glucose

Question 1

what is digestion

Answer 1

where large insoluble food molecules are hydrolyzed into smaller soluble molecules which can then be absorbed

Question 2

what are carbohydrates hydrolysed into

Answer 2

simple sugars

Question 3

what does the salivary glands release to help starch digestion

Answer 3

salivary amalyse

Question 4

what does the pancreas release to help starch digestion

Answer 4

pancreatic amalyse

Question 5

explain the process of starch digestion

Answer 5

• food enters the mouth and is broken up by teeth (mechanical digestion) and then mixed with saliva
• salivary amylase starts to hydrolyse glycosidic bonds in the starch producing maltose
• the salivary amylase then denatures in the stomach due to ph
• in the small intestine, pancreatic amylase continues to hydrolyse the starch to maltose
• maltose is then hydrolysed into glucose by the membrane-bound maltase. This enzyme is embedded into the cell surface of the epithelial cells that line the ileum
• glucose is then absorbed in the ileum

Question 6

what are the two types of diffusion

Answer 6

-simple diffusion
-facilitated diffusion

Question 7

monosaccharides are absorbed into epithelial cells by ________

Answer 7

co-transport

Question 8

explain the absorbtion of glucose

Answer 8

• sodium ions are actively transported out of epithelial cells into the blood (this requires energy)
• this creates a concentration gradient of sodium ions between ileum and the epithelial cells
• sodium ions and glucose enter by facilitated diffusion using co-transporter proteins. The co-transporter has two binding sites, one specific to sodium and one specific to glucose. Sodium diffuse into the cell down the concentration gradient and glucose moves into the cell against its concentration gradient
• glucose moves into the blood by facilitated diffusion

Question 9

explain three ways that the epithelial cells are adapted to their function

Answer 9

1. they contain microvilli which increase the surface area for absorption. This means there is a large number of co-transport proteins for a fast rate of absorption
2. they contain many mitochondria to produce the large amount of ATP they need for the active transport of sodium
3. they have blood vessels going all the way into the microvilli, giving it a good blood supply. This maintains the concentration gradient