Absorption

Question 1

What are micelles?

Answer 1

Micelles are circular formations that are made up of phospholipid tails.

Question 2

Where are sodium-dependent co-transporter proteins located?

Answer 2

The epithelial cell membrane

Question 3

Describe the formation of micelles.

Answer 3

After larger, lipid molecules have been broken down into monoglycerides and fatty acids, bile salts are secreted by the liver. The bile salts associate with the monoglycerides and fatty acids to form micelles.

Question 4

What substances are secreted by the liver to form micelles?

Answer 4

Bile salts.

Question 5

What happens to the co-transporter proteins when amino acids or monosaccharides bind?

Answer 5

Conformational change

Question 6

How are monosaccharides transported into the epithelial cells in the ileum?

Answer 6

Using transporter cells

Question 7

Where is lipase produced?

Answer 7

The pancreas

Question 8

Where are bile salts produced?

Answer 8

In the liver.

Question 9

What is the process of forming micelles called?

Answer 9

Emulsification.

Question 10

In which organs does the digestion of proteins take place?

Answer 10

Small intestine & The stomach

Question 11

What enzymes catalyse the hydrolysis of peptide bonds at the ends of proteins?

Answer 11

Exopeptidases

Question 12

Describe the active transport of sodium ions into the blood

Answer 12

1. Sodium-dependent co-transporter proteins are located in the epithelial cell membranes.
2. The co-transporter proteins actively transport sodium ions into the blood.
3. This causes the concentration of sodium ions in the epithelial cells to decrease.

Question 13

What substances do the bile salts associate with to form micelles?

Answer 13

Monoglycerides & Fatty acids

Question 14

Define digestion.

Answer 14

The hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across cell
membranes.

Question 15

Which enzymes are involved in
carbohydrate digestion? Where are they
found?

Answer 15

● Amylase in mouth
● Maltase, sucrase, lactase in
membrane of small intestine

Question 16

What are the substrates and products of

the carbohydrate digestive enzymes?

Answer 16

● Amylase → starch into smaller polysaccharides
● Maltase → maltose into 2 x glucose
● Sucrase → sucrose into glucose and fructose
● Lactase → lactose into glucose and galactose

Question 17

Where are lipids digested?

Answer 17

The small intestine

Question 18

What needs to happen before lipids can

be digested?

Answer 18

They must be emulsified by bile salts produced by the liver. This breaks down large fat molecules into smaller, soluble molecules called micelles, increasing
surface area.

Question 19

How are lipids digested?

Answer 19

Lipase hydrolyses the ester bond between the monoglycerides and fatty acids.

Question 20

Which enzymes are involved in protein

digestion? What are their roles?

Answer 20

● Endopeptidases= break between specific
amino acids in the middle of a polypeptide.

● Exopeptidases= break between specific amino
acids at the end of a polypeptide.

● Dipeptidases= break dipeptides into amino
acids.

Question 21

How are certain molecules absorbed into
the ileum despite a negative
concentration gradient?

Answer 21

Through co-transport

Question 22

Which molecules require co-transport?

Answer 22

Amino acids and monosaccharides

Question 23

Explain how sodium ions are involved in

co-transport.

Answer 23

Sodium ions (Na+) are actively transported out of the cell into the lumen, creating a diffusion gradient. Nutrients are then taken up into the cells along with Na+ ions.

Question 24

Why do fatty acids and monoglycerides

not require co-transport?

Answer 24

The molecules are nonpolar, meaning they can easily diffuse across the membrane of the epithelial cells.