Absorption

Question 1

What are 4 adaptations of cells to increase the rate of substance exchange

Answer 1

Thin walls for a short diffusion distance

Large surface area

Good blood supply

Steep concentration gradient

Question 2

What is the role of Amylase?

Answer 2

Hydrolyses starch to maltose

Question 3

Why are the disaccharidases and lipase membrane bound?

Answer 3

For a short diffusion distance

Enzymes can be used repeatedly

Question 4

What is the role of Maltase

Answer 4

Hydrolyses maltose to glucose

Question 5

What is the role of Lipase

Answer 5

Hydrolyses triglycerides into monoglycerides and 2 fatty acids

Question 6

What is the role of Sucrase

Answer 6

Hydrolyses sucrose into glucose and fructose

Question 7

What is the role of Lactase

Answer 7

Hydrolyses lactose into glucose and galactose

Question 8

Name the three parts of the small intestine in order.

Answer 8

Duodenum

Jejunum

Ileum

Question 9

What happens in the duodenum of the small intestine

Answer 9

Bile from the liver is released to neutralise stomach acid

Pancreas releases digestive enzymes

Question 10

What happens in the Jejunum of the small intestine?

Answer 10

Lots of diffusion and facilitated diffusion occur as there is a higher concentration in the lumen than epithelial cells.

Question 11

What happens in the ileum of the small intestine?

Answer 11

Active transport and co-transport takes place as there is a lower concentration of nutrients in the lumen than epithelial cells.

Question 12

What are some adaptations of villi to aid absorption?

Answer 12

Very thin membrane so shorter diffusion pathway

Very large surface area

Presence of capillaries maintains a good blood supply

Question 13

What are the benefits of microvilli?

Answer 13

Give an enormous surface area for absorption

Give more space for channel/carrier proteins

Question 14

Describe carbohydrate digestion

Answer 14

Salivary amylase enters the mouth and mixes with food, starts hydrolysing starch to maltose

Food enters the stomach, pH is too low for amylase, it denatures

Pancreatic amylase hydrolyses the remaining starch to maltose in the small intestine

Food enters the ileum and disaccharides are hydrolysed by membrane bound disaccharidases

Question 15

What is the role of endopeptidases

Answer 15

Hydrolyse peptide bonds between amino acids in the central region of a protein molecule, forming a series of peptide molecules

Question 16

What is the role of exopeptidases?

Answer 16

Hydrolyse peptide bonds on the terminal amino acids of peptide molecules. They progressively release dipeptides and single amino acids

Question 17

Endo- and exopeptidases are….

Answer 17

Membrane-bound

Question 18

Describe the absorption of monosaccharides and amino acids, call monosaccharides and amino acids “nutrients”

Answer 18

Sodium ions are actively transported out of ileum epithelial cells into the blood - setting up a sodium ion concentration gradient between the lumen and epithelial cells

Nutrients are co-transported alongside sodium ions from the lumen into epithelial cells

Nutrients move via facilitated diffusion from epithelial cells into the blood

Question 19

What is the role of bile salts?

Answer 19

Break up lipids into smaller droplets

So lipase can easier digest triglycerides into monoglycerides and fatty acids, which form micelles

Question 20

Describe the absorption of triglycerides

Answer 20

Micelles are broken down to release fatty acids and monoglycerides

Fatty acids and monoglycerides can diffuse into epithelial cells lining the ileum

Triglycerides reform inside the cells’ endoplasmic reticulum

They are then packaged into chylomicrons in the Golgi body for transport

Chylomicrons are released from epithelial cells via exocytosis into lacteals

Chylomicrons are transported via the lacteals in the lymphatic system to the blood.

Question 21

What are lacteals?

Answer 21

Lymphatic vessels in the villi

Question 22

Where do useful amino acids go after absorption?

Answer 22

Sent straight to body cells to be used in the synthesis of proteins

Question 23

Where do non-useful amino acids go after absorption?

Answer 23

Changed into urea by the liver