3.2.2 Digestion and Absorption Flashcards Preview

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Flashcards in 3.2.2 Digestion and Absorption Deck (41)
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1

The duodenum is connect to the _____

stomach

2

The ileum is connect to the _____

large intestine

3

How is food physically broken down?

By teeth in the mouth and by muscular stomach

4

How is food chemically broken down?

  • Hydrolysis of large insoluble molecules into small soluble molecules 
  • Carried out by specific enzymes

5

What are carbohydrates broken down into?

Disaccharides and then monosaccharides

6

What are lipids broken down into?

Fatty acids and monoglycerides

7

What are proteins broken down into?

Amino acids 

8

Name 2 enzymes that break down carbohydrates 

  • Amylase
  • Membrane-bound disaccharidases

9

What reaction does amylase catalyses?

Conversion of starch into maltose

10

Where is amylase produced & where is it released to?

  • Salivary glands - release amylase into mouth
  • Pancreas - releases amylase into small intestine

11

What are membrane-bound disaccharidases?

Enzymes that are attached to cell membranes of epithelial cells lining the ileum

12

What reaction do membrane-bound disaccharidases catalyses?

Hydrolysis of disaccharides (e.g. maltose, sucrose, lactose) into monosaccharides (e.g. glucose, fructose and galactose)

13

Fill in the blanks

14

What reaction does lipase catalyse?

Hydrolysis of lipids into monoglycerides and fatty acids

15

Where is lipase made and where does it work?

Pancreas - works in small intestine 

16

Where are bile salts produced?

Liver

17

What do bile salts do?

  • Emulsify lipids
    • Cause lipids to form small droplets

18

What is the benefit of bile salts causing lipids to form small droplets?

  • Several small lipid droplets have bigger SA than single large droplet
  • Lipase can digest lipids faster

19

What happens after the lipid has broken down?

Monoglycerides and fatty acids stick with bile salts to form tiny structures called micelles

20

Name the different proteases (or peptidases) that break down proteins

  • Endopeptidases 
  • Dipeptidases
  • Exopeptidases 

21

What do endopeptidases do?

Break polypeptides into smaller peptide chains

22

Where are trypsin and chymotrypsin (endopeptidases) synthesised and secreted into?

Synthesised in pancreas and secreted into small intestine

23

Where is pepsin (endopeptidases) synthesised and secreted into?

Released into stomach by cells in stomach lining

24

What do exopeptidases do?

  • Act to hydrolyse peptide bonds at ends of protein molecules 
  • Remove terminal amino acids

25

What are dipeptidases?

Exopeptidases that work specifically on dipeptides

26

What do dipeptidases do?

  • Hydrolses dipeptides into amino acids
  • Breaks peptide bond between them

27

Where are dipeptidases located?

In cell-surface membrane of epithelial cells in small intestine

28

How is glucose and galactose absorbed?

By active transport with sodium ions via co-transporter protein

29

How is fructose is absorbed?

Via facilitated diffusion through different transporter protein

30

Describe how glucose is absorbed from lumen (middle) of ileum by co-transport

  1. Na+ ions actively transported out of ileum epithelial cells into blood by sodium-potassium pump
    1. = creates concentration gradient
    2. Higher conc. of Na+ in lumen than inside cell
  2. Causes Na+ to diffuse into epithelial cell by facilitated diffusion (down their concentration gradient)
    • Via sodium-glucose co-transporter proteins
  3. Glucose absorbed with Na+ against their concentration gradient
    • = concentration of glucose inside cell increases
  4. Glucose diffuses out of cell into blood, down its concentration gradient through protein channel by facilitated diffusion

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