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Alimentary System > Nutrient Digestion - Carbohydrates, Proteins, Fats, Vitamins and Minerals > Flashcards

Nutrient Digestion - Carbohydrates, Proteins, Fats, Vitamins and Minerals Flashcards

1
Q

What are the only three sugars that can be taken up across the gut epithelia?

A

Monosaccharides - glucose, galactose and fructose

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2
Q

What bonds are broken between disaccharide monomers to form simpler molecules?

A

Glycosidic

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3
Q

Disaccharides are broken down to their constituent monomers through the use of what?

A

Brush border enzymes

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4
Q

What are the three dietary disaccharides and their constituent monomers?

A

Lactose - glucose and galactose
Sucrose - glucose and fructose
Maltose - glucose monomers

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5
Q

What are the enzymes responsible for breaking down disaccharides into their constituent monomers?

A

Lactase breaks down lactose
Sucrase breaks down sucrose
Maltase breaks down maltose

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6
Q

The alpha-1,4-glycosidic bonds between the glucose monomers of starch are broken down by what?

A

The bonds are hydrolysed by amylases in saliva and in the pancreas

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7
Q

Why can’t animals break down cellulose?

A

The beta-1,4-glycosidic bonds between the glucose monomers of cellulose can only be broken down by cellulase, which is an enzyme that no animals have the capability to express

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8
Q

What breaks down glycogen?

A

Alpha-amylase

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9
Q

What are the three mechanisms through which monosaccharides are absorbed across intestinal epithelial cells?

A

Transcellular
Paracellular
Vectorial Transport

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10
Q

What is the route that most nutrients will take when absorbed across intestinal epithelial cells?

A

Transcellular - lipid soluble molecules which can cross apical and basolateral membranes

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11
Q

What route of absorption across intestinal epithelial cells involves molecules of the right shape and size crossing through the tight junctions between epithelial cells?

A

Paracellular

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12
Q

What transport mechanism is used for water soluble molecules which cannot transport across the lipid membrane?

A

Vectorial transport

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13
Q

What transport mechanism involves the use of transporter proteins?

A

Vectorial transport

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14
Q

What are peptides?

A

Polymers of amino acids, 3-10 amino acids in length

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15
Q

Polymers of amino acids in chains with a length of 10 or more amino acids are what?

A

Proteins

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16
Q

What bonds need to be hydrolysed between proteins in order to convert them to peptides and amino acids for digestion?

A

Peptide

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17
Q

What enzymes hydrolyse peptide bonds?

A

Proteases and peptidases

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18
Q

Where do endopeptidases act?

A

Somewhere in the middle of the protein

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19
Q

Where do exopeptidases act?

A

Only on the terminal amino acids of a protein, removing amino acids one at a time

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20
Q

How are amino acids and small peptides absorbed across gut epithelia?

A

Transported in/out by a pump

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21
Q

What does the SAAT1 pump do?

A

Binds to a sodium molecule and an amino acid at the apical membrane and pumps both into the cell

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22
Q

The movement of sodium through the cell and the ion gradient it creates causes what?

A

The movement of water in the same direction as sodium, through the tight junctions

23
Q

What is PepT1?

A

A protein coupled transporter which transports dipeptides and tripeptides as well as a hydrogen ion into the cell

24
Q

What can penicillin transport into the gut epithelial cells?

A

Tripeptides

25
Q

Almost all fat is ingested in the form of

A

triacylgylcerol

26
Q

What is triacylglycerol broken into during digestion?

A

Monoglyceride and fatty acids

27
Q

All fat digestion takes place _ through the use of _

A

in the small intestine

through the use of pancreatic lipase

28
Q

What will happen when pancreatic lipase is digesting triaclyglycerols which are present as large lipid droplets?

A

Pancreatic lipase is water soluble but not lipid soluble so can only work on the outer surface of the lipid droplet, it will therefore be unable to digest all the fat

29
Q

What is the name for fat in stools?

A

Steatorrhoea

30
Q

What does emulsification of ingested fats do?

A

Divides large lipid droplets (triaclyglycerols) into smaller droplets, increasing surface area available to pancreatic lipase and making fat digestion more manageable

31
Q

What three things does emulsification require?

A

Mechanical disruption
Smooth muscle contraction
An emulsifying agent

32
Q

What is the purpose of an emulsifying agent?

A

To stop the reformation of smaller lipid droplets into large lipid droplets

33
Q

What is the purpose of bile salts and phospholipids in fat digestion?

A

Both prevent the re-formation of small droplets of fat produced by emulsification into larger droplets

34
Q

Bile salts and phospholipids are secreted in

A

bile

35
Q

What feature of bile salts and phospholipids makes them effective at preventing the reformation of large lipid droplets?

A

They are amphipathic - non-polar portions associate with non-polar interior of the droplet leaving the polar portions exposed at the surface which repel other small lipid droplets

36
Q

What are the components of micelles?

A

Bile salt
Monoglyceride
Fatty acids
Phospholipids

37
Q

What is the purpose of micelles in fat digestion?

A

Enhance fat absorption by taking fat molecule to the microvilli of the epithelia for absorption

38
Q

What happens once fatty acids and monoglycerides enter the smooth ER after entering epithelial cells?

A

They are reformed into triacylglycerol droplets which are emulsified

39
Q

What are the fat soluble vitamins?

A

A, D, E and K

40
Q

What are the water soluble vitamins and how are they absorbed?

A

B group, C and folic acid

Absorbed by passive diffusion or carrier-mediated transport

41
Q

How is vitamin B12 absorbed?

A

It binds to an intrinsic factor in the stomach to form a complex which is absorbed via a specific transport mechanism in the distal ileum

42
Q

What does a vitamin B12 deficiency cause?

A

Pernicious anaemia

43
Q

What percentage of daily ingested iron is absorbed across the intestine into the blood?

A

10%

44
Q

Iron ions are incorporated into what, in order to be stored intracellularly?

A

Ferritin

45
Q

For how long does iron stay bound in ferritin?

A

Until the cell containing the ferritin dies, at which point the iron is expelled from the body

46
Q

What happens to unbound iron?

A

It is transported across the serous membrane where it binds to transferrin and is taken to the liver for storage

47
Q

What 3 pairs of glands secrete saliva?

A

Parotid
Submandibular
Sublingual

48
Q

What are the components of saliva?

A 
Water
Mucins 
Alpha-amylase 
Electrolytes 
Lysozyme
49
Q

What are the functions of water in saliva?

A

Softens, moistens and dilutes particles

50
Q

What is the function of mucins in saliva?

A

To combine with water to form mucous which acts as a lubricant

51
Q

What is the function of alpha-amylase in the saliva?

A

Catalyses the breakdown of polysaccharides into disaccharides + glucose

52
Q

What is the function of electrolytes in the saliva?

A

Control the tonicity and pH

53
Q

What is the function of lysozyme in the saliva?

A

Bacteriocidal - cleaves the polysaccharide component of any bacterial cell wall ingested

Alimentary System (29 decks)

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