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ZZZ AS level: Biology > Digestion and absorption > Flashcards

Digestion and absorption Flashcards

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1
Q

what is digestion?

A

process which large molecules are hydrolysed by enzymes into smaller molecules which can be absorbed and assimilated

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2
Q

what is ingestion?

A

process by taking food into body through the mouth (eat)

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3
Q

what is assimilation?

A

the conversion of absorbed food into a substance required for the body

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4
Q

what is egestion?

A

final act of digestion which eliminates solid/liquid waste material from digestive tract via the anus

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5
Q

what is another term for egestion?

A

defecation

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6
Q

name the seven major parts of the digestive system

A
  • salivary glands
  • oesophagus
  • stomach
  • pancreas
  • large intestine
  • small intestine
  • rectum
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7
Q

mnemonic for major parts of digestive system

A
  • So
  • Ollie
  • Stopped (eating)
  • Pringles
  • Like
  • Some
  • Rookie
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8
Q

location/ function of salivary glands

A
  • situated near mouth

- pass secretions via a duct in mouth which contains amylase

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9
Q

function of oesophagus

A

carries food from mouth to stomach

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10
Q

description/ function of stomach

A
  • muscular sac with inner layer producing protease

- stores and digest food

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11
Q

location/ function of pancreas

A
  • situated below stomach

- produces secretion called pancreatic juice containing protease, lipase and amylase

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12
Q

function of large intestine (colon)

A
  • absorbs water from secretions of digestive glands
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13
Q

function of small intestine (ileum)

A
  • digests food by enzymes

- inner walls folded into villi to aid absorption of products into bloodstream

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14
Q

functions of rectum

A
  • temporary storage for faeces

- removed via anus in egestion

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15
Q

what is the overall name for enzymes used in digestion and what process do they use to split molecules?

A
  • hydrolases

- hydrolysis: split molecules by adding water

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16
Q

what are the two stages to digestion?

A
  • physical breakdown - churning

- chemical breakdown - digestion

17
Q

what are three types of molecules digested?

A
  • carbohydrates
  • lipids
  • proteins
18
Q

which enzymes are involved in the digestion of carbohydrate?

A
  • salivary amylase
  • pancreatic amylase
  • maltase (membrane-bound disaccharidase)
19
Q

what pH does amylase work best in and how does the body maintain the optimum pH?

A
  • alkaline conditions
  • salivary amylase: contains mineral salts to keep pH at neutral
  • pancreatic amylase: alkaline salts produced by pancreas and intestinal wall to maintain pH
20
Q

explain the process of carbohydrate digestion

A

saliva enters mouth through glands

  • mixes with food during chewing
  • saliva contains salivary amylase which hydrolyses starch to maltose
  • swallowed by stomach
  • stomach acid denatures salivary amylase
  • passed into small intestine
  • mixes with pancreatic juice containing amylase which hydrolyses starch to maltose
  • muscles in intestinal wall pushes food along ileum
  • epithelial lining produced maltase (membrane-bound disaccharidase)
  • hydrolyses maltose into alpha-glucose
21
Q

name two others disaccharides that are digested in diet

A
  • sucrose

- lactose

22
Q

how is sucrose hydrolysed?

A

sucrase

- glucose + fructose

23
Q

how is lactose hydrolysed?

A
  • lactase

- glucose +galactose

24
Q

what type of enzymes hydrolyse lipids?

A
  • lipase
25
Q

where is lipase produced and what does it do?

A

produces in pancreas

- hydrolyses ester bond in triglycerides - fatty acid + monoglyceride

26
Q

how does lipase split the lipid up?

A
  • split into micelles
  • emulsified by bile salts
  • surface area increased - increased enzyme reaction rate
27
Q

how are micelles (triglycerides) absorbed?

A
  • micelles come into contact with epithelial cells - release monoglycerides and fatty acids
  • as they are non-polar, they diffuse across cell membrane
  • recombine on SER to form triglyceride
  • in Golgi triglycerides combines with cholesterol and lipoproteins to form chylomicrons
  • secreted out of cell by exocytosis
  • enter lacteals (lymphatic capillaries)
  • emptied into blood stream via thoracic duct
  • ## either used by blood or transported to liver and split into HDL and LDL
28
Q

what enzymes are involved in protein digestion?

A

peptidases (proteases)

29
Q

what three peptidases are used?

A
  • endopeptidase
  • exopeptidase
  • dipeptidase
30
Q

explain process of protein digestion

A
  • endopeptidase hydrolyses peptide bonds between amino acids in central region to split into peptides
  • exopeptidase hydrolyses peptide bonds between terminal amino acids to release dipeptides and single amino acids
  • dipeptidase hydrolyses dipeptides into two monopeptide
31
Q

what is dipeptidase described as?

A

membrane bound

ZZZ AS level: Biology (21 decks)

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