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BIOLOGY - EXCHANGE AND TRANSPORT SYSTEMS > DIGESTION AND ABSORPTION > Flashcards

DIGESTION AND ABSORPTION Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What do glands produce and what is their function

A

enzymes that hydrolyse large molecules into smaller ones for digestion

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2
Q

Why can’t large biological molecules be absorbed into the blood from the gut and give examples

A

too big to cross cell membrane, e.g. starch and proteins

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3
Q

What are carbohydrates broken down into during hydrolysis

A

disaccharides and then monosaccharies

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4
Q

What are fats broken down into during hydrolysis

A

fatty acids and monoglycerides

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5
Q

What are proteins broken down into during hydrolysis

A

amino acids

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6
Q

What does amylase catalyse

A

conversion of starch into maltose

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7
Q

Where is amylase produced and released

A

salivary glands (into mouth) and pancreas (into small intestine)

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8
Q

What are the major parts of the digestive system

A

1) oesophagus
2) stomach
3) ileum
4) large intestine
5) rectum
6) salivary glands
7) pancreas

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9
Q

What is the job of the oesophagus

A

carry food from mouth to the stomach

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10
Q

What is the stomach

A

muscular sac with an inner ayer that produces enzymes

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11
Q

What is the role of the stomach

A

to store and digest food, especially proteins

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12
Q

What is the ileum

A

long muscular tube

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13
Q

What is the role of the ileum

A

to further digest food by enzymes that are produced in its walls and by glands that release them into it

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14
Q

What adaptation does the ileum have

A

the inner walls are folded into villi to increase SA:V, which are then folded further into microvilli on the epithelial cells of each villus - means that there is a larger SA for absorption into blood stream

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15
Q

What is the role of the large intestine

A

to absorb water, mainly water secreted from the digestive glands

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16
Q

What is the role of the rectum

A

to store the faeces until being removed via the anus through egestion

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17
Q

Where are the salivary glands situated

A

near the mouth

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18
Q

What do salivary glands secrete via a duct into the mouth

A

enzyme amylase that hydrolyses starch into maltose

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19
Q

Where is the pancreas situated

A

below the stomach

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20
Q

What is the role of the pancreas

A

to secrete pancreatic juice that contains proteases, lipase and amylase

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21
Q

What are the 2 stages of digestion

A

1) physcial breakdown

2) chemical breakdown

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22
Q

What is physical breakdown

A

the break up of large pieces of food into smaller ones via structures such as the teeth or stomach wall

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23
Q

What does physical breakdown mean

A

the food is possible to ingest, and there is a larger SA:V for chemical breakdown

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24
Q

What is chemial breakdown

A

hydrolysis carried out by enzymes of large, insoluble molecules into smaller soluble ones

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25
Q

What are the 3 main types of digestive enzymes and what do they hydrolyse

A

1) carbohydrases (carbohydrates-monosaccharides)
2) lipases (lipids-fatty acids and glycerol)
3) proteases (proteins-amino acids)

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26
Q

What is the usual events that occur when hydrolysing a carbohydrate

A

enzymes hydrolyse the molecule into smaller sectioons, and other enzymes hydrolyse them into their monomers

27
Q

Explain the general process of starch digestion

A

1) amylase is produced in the mouth and pancreas which hydrolysis the alternate glycosidic bonds of the starch molecule, to produce maltose
2) Maltose is hydroyled by maltase (produced by lining of ileum) into alpha glucose

28
Q

How does starch digestion occur in humans

A

1) saliva that contains salivary amylase and mineral salts enters mouth from salivary glands and mixed with food, which hydrolyses it into maltose (salts help to maintain neutral pH= optimal for enzyme)

29
Q

How does starch digestion occur in humans 2

A

food enters stomach where conditions are acidic, whcih denatures amylase and stops further hydrolysis

30
Q

How does starch digestion occur in humans 3

A

passed into small intestine where it mixes with pancreatic juice which contains pancreatic amylase that hydrolyses any remaining starch into maltose. pH is maintained at neutral by alkaline salts produced by pancreas &intestinal wall (so amylase can function)

31
Q

How does starch digestion occur in humans 4

A

muscles in intestinal wall push food along the ileum whilst its epithelial lining produces maltase. Here it is a membrane bound disaccharidase, which hydrolyses maltose to alpha glucose

32
Q

Why is the maltase in ileum describedc as membrane-bound disaccharidase

A

it is not released into the lumen of the ileum but is part of the cell-surface membranes of the epithelial cells that line the ileum

33
Q

What are 2 other common disaccharies that are hydrolysed and what are they found in

A

1) sucrose - natural foods, fruits

2) lactose - milk

34
Q

What hydrolyses sucrose and descrbe

A

sucrase, breaks the single glycosidic bond to produce glucose and fructose

35
Q

What hydrolyses lactose and describe

A

lactase, breaks single glycosidic bond to produce glucose and galactose

36
Q

What are lipids hydrolysed by

A

lipases

37
Q

Where are lipases produced and where do they function

A

in the pancreas, work in small intestine

38
Q

How do lipases work

A

they hydrolse the ester bond found in triglycerides to form fatty acids and monoglycerides

39
Q

What is a monoglyceride

A

glycerol molecule with a single fatty acid molecule attached

40
Q

How and why are lipids emulsified

A

by bile salts, as it increases the lipids surface area

41
Q

Where are bile salts produced by

A

the liver

42
Q

What are micelles

A

the molecules formed after the monoglycerides fatty acids stick with the bile salts

43
Q

What do peptidases hydrolyse

A

proteins

44
Q

What are the types of peptidases

A

1) endopeptidases
2) exopeptidases
3) dipeptidases

45
Q

What do endopeptidases do

A

hydrolyse bonds WITHIN a protein - hydrolyse the bonds between amino acids in the central region of a protein molecule to form a series of peptide molecules

46
Q

Give 3 examples of endopeptidases and where theyre fromed/released

A

trypsin and chymotrypsin - synthesised in pancreas & secreted into small intestine
pepsin - released into stomach by cells in stomach lining

47
Q

What conditions does pepsin work best in and how are these met

A

acidic - provided by hydrochlorica acid in the stomach

48
Q

What do exopeptidases do

A

hydrolyse the bonds AT THE END of the protein molecules (terminal amino acids) meaning they progressively release dipeptides and single amino acids (remove single amino acids from proteins)

49
Q

What do dipeptidases do

A

hydrolyse bond between 2 amino acids of a dipeptide by hydrolysing the peptide bond between them

50
Q

Where are dipeptidases often located

A

in the cell-surface membrane of epithelial cells in the small intestine

51
Q

Are dipeptidases membrane-bound

A

yes

52
Q

What causes lactose intolerance

A

the production of very little/no lactase so the lactose cannot be hydrolysed

53
Q

What are the villi of the ileum located

A

between the lumen of the intestines, & the blood and other tissues inside the body

54
Q

How do villi increase efficiency of absorption

A

1) increase SA:V for diffusion
2) very thin walled = short diffusion distance
3) contain muscle so are able to move, so can maintain diffusion gradients by mixing the content of the ileu
4) well supplied with blood vessels so blood can carry away absorbed molecules and hence maintain diffusion gradient
5) epithelial cells possess microvilli, further increase SA:V

55
Q

How are amino acids and monosaccharides absorbed across cell membranes (w glucose, galactose, fructose)

A

diffusion and co-transport
glucose = absorbed via active transport with sodium ions via co-transporter protein
galactose = co-transport
fructose = facilitated diffusion

56
Q

How big are micelles

A

small, 4-7nm in diameter

57
Q

How do monoglycerides and fatty acids transport across cell membranes

A

micelles come into contact with epithelial cells lining villi of ileum and break down, releasing the non-polar lipid-soluble monoglycerides and fatty acids which diffuse across the membrane

58
Q

What happens to monoglycerides and fatty acids once they are inside the epithelial cells

A

transported to endoplasmic reticulum where they are recombined to form triglycerides

59
Q

What are chylomicrons

A

special particles adapted for the transport of lipids

60
Q

What happens to the triglycerides after the endoplasmic reticulum

A

continue in the golgi apparatus where they associate with cholesterol and lipoproteins to form chylomicrons

61
Q

How do chylomicrons move out of the epithelial cells

A

exocytosis

62
Q

What happens to the chylomicrons after they move out of the epithelial cells

A

enter lymphatic capillaries called lacteals that are found at the centre of each villus, then into the bloodstream

63
Q

How are amino acids absorbed across cell membranes

A

(similar way to glucose and galactose), sodium ions actively transported out of the epithelial cells into the ileum then diffuse back into the cells through sodium-dependant transporter proteins and carry amino acids with them

64
Q

What substance plays a role in the digestion and absorption of fatty acids

A

bile salts

BIOLOGY - EXCHANGE AND TRANSPORT SYSTEMS (11 decks)

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