3.3.3 Digestion And Absorption Flashcards Preview

AQA A Level Biology (yr 12 content) > 3.3.3 Digestion And Absorption > Flashcards

Flashcards in 3.3.3 Digestion And Absorption Deck (15)
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1
Q

What is digestion?

A

hydrolysis of large molecules into smaller molecules that can be absorbed across the cell membrane

2
Q

Which enzymes are involved in carbohydrate

digestion? Where are they found?

A

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

3
Q

Amylase breaks down ….

A

starch into smaller polysaccharides

4
Q

maltase breaks down …..

A

maltose into 2 glucose molecules

5
Q

Sucrase breaks down ….

A

sucrose into glucose and fructose

6
Q

Lactase breaks down …..

A

Lactose into glucose and galactose

7
Q

Where are lipids digested?

A

Small intestine

8
Q

What needs to happen before lipids can be

digested?

A
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.
9
Q

How are lipids digested?

A

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

10
Q

Which enzymes are involved in protein digestion?

What is their role?

A

● 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.

11
Q

How are certain molecules absorbed into the ileum

despite a negative concentration gradient?

A

Through co-transport.

12
Q

Which molecules require co-transport?

A

Amino acids and monosaccharides.

13
Q

Explain how sodium ions are involved in

co-transport.

A

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.

14
Q

Why do fatty acids and monoglycerides not require

co-transport?

A

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

15
Q

Explain the process of co transport of glucose in the lumen.

A
  • sodium ions are actively pumped from the cytoplasm of the epithelial cells via channel proteins into the surrounding tissue fluid
  • sodium ions diffuse from lumen into epithelial cell,down conc gradient carrying the glucose molecules with them.