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Biology > Digestion and absorption > Flashcards

Digestion and absorption Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Role of the oesophagus?

A

carries food from the mouth to the stomach

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2
Q

Role of the stomach?

A

stores and digests food. Has glands which produce enzymes for protein digestion

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3
Q

Role of the ileum (small intestine)?

A

food is digested by enzymes produced in the walls and glands of the small intestine. Inner walls are folded into villi, with small projections called microvilli which give a large surface area, for rapid absorption into the bloodstream

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4
Q

Role of the large intestine?

A

absorbs water

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5
Q

Role of the salivary glands?

A

secrete amylase, which hydrolyses starch into maltose

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6
Q

Role of the pancreas?

A

secretes pancreatic juice containing protease, lipase and amylase

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7
Q

Why is it necessary to digest polymers?

A
  • need to be small enough to pass into the bloodstream from the small intestine
  • need to be soluble for absorption
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8
Q

What are physical and chemical digestion?

A

physical - large pieces of food are broken down into smaller pieces by physical structures, which increases surface area for chemical digestion

chemical - large, insoluble molecules are broken down into smaller, soluble molecules by enzymes through hydrolysis reactions

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9
Q

What is the substrate of amylase?

A

starch

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10
Q

What is the substrate of maltase?

A

maltose

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11
Q

What is the substrate of lactase?

A

lactose

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11
Q

What is the substrate of lipase?

A

triglycerides

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11
Q

What is the substrate of sucrase?

A

sucrose

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12
Q

What is the substrate of exopeptidase?

A

polypeptides and dipeptides

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13
Q

What is the substrate of endopeptidase?

A

polypeptides

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14
Q

What is the product of starch?

A

maltose

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14
Q

What is the substrate of dipeptidase?

A

dipeptides

15
Q

What is the product of maltose?

A

glucose

16
Q

What are the products of sucrose?

A

glucose and fructose

17
Q

What are the products of triglycerides?

A

glycerol and 3 fatty acids

17
Q

What are the products of lactose?

A

glucose and galactose

18
Q

What are the products of polypeptides?

A

shorter polypeptide chains and dipeptides

19
Q

What are the products of dipeptides?

A

amino acids

20
Q

Where is amylase produced?

A

salivary glands and pancreas

21
Q

Where dissacharidases (maltase, lactase, sucrase) produced?

A

epithelial lining of ileum

22
Q

Where is lipase produced?

A

pancreas

23
Q

Where is endopeptidase produced?

A

stomach and pancreas

24
Q

Where is exopeptidase produced?

A

pancreas

25
Q

Where is dipeptidase produced?

A

epithelial lining of ileum

26
Q

What is the site of digestion of starch?

A

mouth and duodenum

27
Q

What is the site of digestion for disaccharides?

A

epithelial lining of ileum

28
Q

What is the site of digestion of triglycerides?

A

duodenum

29
Q

What is the site of digestion of short polypeptide chains and dipeptides broken down by endopeptidase?

A

stomach and duodenum

30
Q

What is the site of digestion of dipeptides and amino acids broken down by exopeptidase?

A

dueodenum

31
Q

What is the site of digestion of amino acids broken down by dipeptidase?

A

epithelial lining of ileum

32
Q

How are carbohydrates digested?

A
  • amylase produced in the salivary glands will begin to hydrolyse starch into maltose
  • food is swallowed and enters the stomach where conditions are acidic. The acid denatures amylase which prevents further hydrolysis
  • food passes into the small intestine and mixes with pancreatic juice containing amylase which hydrolyses the remaining starch into maltose
  • maltose is hydrolysed into alpha glucose by maltase produced in the lining of the ileum
33
Q

How are lipids digested?

A
  • lipids are hydrolysed by lipase enzymes produced in the pancreas which breaks ester bonds found in triglycerides
  • lipoids are firstly split into micelles by bile salts produced in the liver
  • this is called emulsification and increases surface area for faster digestion of lipids
34
Q

How are proteins digested?

A
  • endopeptidases hydrolyse peptide bonds between amino acids in the centre of a polypeptide
  • exopeptidase hydrolyse peptide bonds on the terminal amino acids of a peptide molecule
  • dipeptidases hydrolyse peptide bonds between 2 amino acids in a dipeptide
35
Q

How is the small intestine adapted for efficient exchange?

A
  • microvilli provide a large surface area which accelerates the rate of absorption
  • one cell thick epithelial layer/villi for a short diffusion distance
  • constant movement of internal medium (blood constantly flowing and good blood supply) and external medium (food in lumen of gut) so concentration gradient remains steep
36
Q

How is the small intestine specialised for exchange?

A
  • membrane bound disaccharides and dipeptidases
  • muscle tissue for contraction to move along food
  • elastic tissue for expansion and stretching to fit more food
  • lacteals to absorb fat
  • lots of mitochondria for active transport and energy release
37
Q

How are amino acids absorbed into the bloodstream from the epithelial cells?

A

Through co-transport

  • sodium potassium pump - sodium moves out of cell by active transport, low concentration of Na+ inside and high concentration of Na+ in the blood
  • sodium ions and amino acids move from the lumen into epithelial cells. Larger di/tripeptides move in by H+ ions - these proteins are not fully digested
  • di/endo/exopeptidases break down dipeptides into amino acids
  • amino acids move out of epithelial cells into the bloodstream through a carrier protein - they are too large to move out through diffusion
38
Q

How are lipids absorbed and transported from the ileum into the lymph vessels?

A
  • lipase enzymes hydrolyse lipids into glycerol and fatty acids
  • after hydrolysis, bile salts remain associated with lipid molecules and form micelles which are water soluble and move around in the lumen
  • micelles make fatty acids more soluble
  • micelles come into contact with epithelial cells lining the villi of the ileum and maintain a higher concentration of fatty acids and monoglycerides to the lining of the ileum
  • fatty acids and monoglycerides absorbed by diffusion into epithelial cells
  • monoglycerides and fatty acids are transported to the endoplasmic reticulum where they are recombined to form triglycerides
  • triglycerides associate with cholesterol and lipoproteins to form chylomicrons which move out of the epithelial cells by exocytosis
  • chylomicrons enter a lacteal (lymph capillary) and lymph transports them away from the intestine

Biology (21 decks)

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