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MAIN BIO > 3.2.2 Digestion and Absorption > Flashcards

3.2.2 Digestion and Absorption Flashcards

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Biology 101 flashcards
1
Q

The duodenum is connect to the _____

A

stomach

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2
Q

The ileum is connect to the _____

A

large intestine

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3
Q

How is food physically broken down?

A

By teeth in the mouth and by muscular stomach

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4
Q

How is food chemically broken down?

A
  • Hydrolysis of large insoluble molecules into small soluble molecules
  • Carried out by specific enzymes
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5
Q

What are carbohydrates broken down into?

A

Disaccharides and then monosaccharides

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6
Q

What are lipids broken down into?

A

Fatty acids and monoglycerides

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7
Q

What are proteins broken down into?

A

Amino acids

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8
Q

Name 2 enzymes that break down carbohydrates

A
  • Amylase
  • Membrane-bound disaccharidases
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9
Q

What reaction does amylase catalyses?

A

Conversion of starch into maltose

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10
Q

Where is amylase produced & where is it released to?

A
  • Salivary glands - release amylase into mouth
  • Pancreas - releases amylase into small intestine
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11
Q

What are membrane-bound disaccharidases?

A

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

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12
Q

What reaction do membrane-bound disaccharidases catalyses?

A

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

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13
Q

Fill in the blanks

A
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14
Q

What reaction does lipase catalyse?

A

Hydrolysis of lipids into monoglycerides and fatty acids

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15
Q

Where is lipase made and where does it work?

A

Pancreas - works in small intestine

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16
Q

Where are bile salts produced?

A

Liver

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17
Q

What do bile salts do?

A
  • Emulsify lipids
    • Cause lipids to form small droplets
18
Q

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

A
  • Several small lipid droplets have bigger SA than single large droplet
  • Lipase can digest lipids faster
19
Q

What happens after the lipid has broken down?

A

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

20
Q

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

A
  • Endopeptidases
  • Dipeptidases
  • Exopeptidases
21
Q

What do endopeptidases do?

A

Break polypeptides into smaller peptide chains

22
Q

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

A

Synthesised in pancreas and secreted into small intestine

23
Q

Where is pepsin (endopeptidases) synthesised and secreted into?

A

Released into stomach by cells in stomach lining

24
Q

What do exopeptidases do?

A
  • Act to hydrolyse peptide bonds at ends of protein molecules
  • Remove terminal amino acids
25
Q

What are dipeptidases?

A

Exopeptidases that work specifically on dipeptides

26
Q

What do dipeptidases do?

A
  • Hydrolses dipeptides into amino acids
  • Breaks peptide bond between them
27
Q

Where are dipeptidases located?

A

In cell-surface membrane of epithelial cells in small intestine

28
Q

How is glucose and galactose absorbed?

A

By active transport with sodium ions via co-transporter protein

29
Q

How is fructose is absorbed?

A

Via facilitated diffusion through different transporter protein

30
Q

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

A
  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
31
Q

How are amino acids absorbed?

A

By co-transport (similar to glucose)

32
Q

Describe how amino acids are absorbed by co-transport

A
  • Na+ ions actively transported out of ileum epithelial cells in blood
  • Creates Na+ concentration gradient between lumen and cell
  • Na+ can diffuse from lumen into epithelial cells through sodium-dependent transporter proteins, carrying amino acids with them
33
Q

Name two ways the concentration gradient between the inside of the ileum and blood is maintained

A
  • Constant circulation of blood
  • Ileum has muscles which uses peristalsis to keep food moving along the gut
34
Q

Describe how in detail how monoglycerides and fatty acids are absorbed and how they’re transported around the body

A
  1. Micelles help to move monoglycerides and fatty acids towards epithelium
    • ∵ micelles constantly break up and reform they can ‘release’ monoglycerides and fatty acids = allows them to be absorbed
      • ∵ lipid-soluble = can diffuse directly across epithelial cell membrane
  2. Monoglycerides and fatty acids transported to ER & combine to form triglycerides
  3. Triglycerides associated with cholesterol and lipoproteins = form chylomicrons (lipid transport structures)
  4. Chylomicrons enter lacteal (part of lymphatic system) by exocytosis
  5. Only drain into bloodstream near heart
35
Q

The walls of the small intestine have lots of finger-like projections called ____

A

villi

36
Q

The epithelial cells on the surface of the villi have folds in their cell-surface membranes called ______

A

microvilli

37
Q

Explain the presence of bile in the colon (large intestine) (2)

A
  • Secreted by the liver
  • Bile passes unchanged from small intestine to colon
38
Q

Suggest why the peptides released when gluten is digested cannot by absorbed by facilitated diffusion (2)

A
  • Too big/wrong shape
  • Cannot pass through channel protein
39
Q

Describe the function of part X

A

Transports chylomicrons

40
Q

Suggest an advantage of having muscle cells in the villi (2)

A
  • Enables villi to move
  • Increased contact with food
41
Q

Suggest how chylomicrons leave the epithelial cells. Give an reason for your answer. (2)

A
  • Exocytosis
  • Too large to leave by other methods

MAIN BIO (39 decks)

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