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Week 10 > digestion and absorption > Flashcards

digestion and absorption Flashcards

1
Q

measures taken to help the public with a balanced diet

A

traffic light system
break down into diagrams

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2
Q

carbohydrate function

A

energy source

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3
Q

carbohydrate source

A

bread, pasta, rice, cereals, potatoes

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4
Q

protein function

A

growth and repair

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5
Q

protein source

A

meat, fish, dairy, lentils, nuts, seeds, tofu

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6
Q

fat/ lipid function

A

long term energy store; insulation

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7
Q

protein source

A

meat, cheese, cream, fish, nuts, avocado, coconut

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8
Q

vitamins function

A

vitamin specific
A - vision
C - antioxidant
D - Ca absorption

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9
Q

vitamin source

A

examples are also vitamin specific
A - liver, sweet potato
B - vegetables
C - citrus
D - only fish/ sun

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10
Q

mineral function

A

mineral-specific
Ca - bone mineralisation
Fe - oxygen transport

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11
Q

mineral source

A

mineral specific
Ca - milk
Fe - red meat
K - bananas

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12
Q

fibre function

A

effective bowel function

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13
Q

fibre source

A

plants (fruit, vegetables, nuts, cereals)

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14
Q

water function

A

hydration

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15
Q

what are the different types of dietary fats

A

fatty acids
phospholipids
cholesterol

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16
Q

fatty acids info

A

saturated/ unsaturated
saturated source: animal foods (meat, dairy)
unsaturated: mainly from plants (rape seed, nuts..)

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17
Q

phospholipids info

A

sex hormones
bilayer
bile salts

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18
Q

cholesterol info

A

2 fatty acid chains, glycerol, phosphate group
plants + animals (dairy, palm)

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19
Q

what does eating too many fats lead to

A

atherosclerosis (MI, stroke)
obesity - risk factor for many other conditions

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20
Q

what are the 9 essential amino acids

A

phenylalanine
valine
tryptophan
threonine
isoleucine
methionine
histidine
leucine
lysine

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21
Q

carbohydrates - monosaccharides

A

glucose, fructose, galactose

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22
Q

carbohydrates - disaccharides

A

sucrose = glucose + fructose
maltose = glucose + glucose
lactose = glucose + galactose
joined by glycosidic bond

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23
Q

carbohydrates - polysaccharides

A

more tan 10 monomers typically
starch: amylose linear
amylopectin branched
A 1 -> 4 glycosidic bond
A 1 -> 6 beta 1,4 linkage in branched

24
Q

carbohydrates - fibre

A

plant cell walls -> cellulose
beta 1,4 linkage
large straight chains
cannot be digested

25
Q

digestion definition

A

the process by which food is broken down into components simple enough to be absorbed in the intestine

26
Q

where are enzymes for digestion secreted

A

glandular cells in mouth
chief cells in stomach
exocrine cells in pancreas
enzymes bound to the apical membrane of enterocytes

27
Q

salivary secretions

A

where: parotid, submandibular and sublingual salivary glands
- moistens food
- starts the digestion of carbohydrates (a-amylase)
starts the digestion of lipids (minor: lingual lipase)

28
Q

stomach structure in digestion

A

start of protein digestion
chief cells: secrete pepsinogen
parietal cells: HCl secretion
- denatures proteins
- activates pepsin (=endopeptase)
these cells are present in the pits in the epithelium of the stomach lining

29
Q

what is a zymogen

A

zymogens are inactive precursors that are subsequently activated by cleavage of one/ a few specific peptide bonds
- the inactive precursor is called a zymogen (or a proenzyme)
- e.g. pepsinogen (inactive) -> pepsin (active)
- prothrombin -> thrombin

30
Q

role of pancreas in digestion

A

exocrine: pancreatic juice (enzymes and alkali secretions
endocrine: secretion of insulin + glucagon

31
Q

examples of zymogens

A

trypsin -> proteins ( + other proteases)
chymotrypsin (proteins)
carboxypeptidase (proteins)
elastase (proteins (elastin))
phospholipase (phospholipids)

32
Q

examples of non-proteolytic enzymes

A

a-amylase (starch)
lipase (triglycerides)
ribonuclease (RNA)
deoxyribonuclease (DNA)

33
Q

role of the liver in digestion

A

produces and secretes bile
- emulsification
stored in gallbladder (released into duodenum)
micelles

34
Q

what are bile salts

A

synthesised from cholesterol ->cholic acid, chenodeoxycholic acid
conjugated to amino acid (glycine or taurine) -> secreted
amphipathic (contain both hydrophobic (cholesterol)/ hydrophilic faces (amino acid conjugate)
detergent action on dietary fat -> ^ SA for digestion

35
Q

what are the functions of fat salts

A

emulsification of lipid aggregates
solubilisation and transport of lipids in aqueous environment

36
Q

what are the three sections of the small intestine

A

duodenum, jejunum, ileum

37
Q

what is the function of the duodenum

A

mixing secretion from pancreas, liver and duodenum with food
neutralisation of stomach acid (HCl)
pepsin inactivation
further digestion
absorption

38
Q

what is the function if the jejunum

A

completing breakdown
nutrient absorption

39
Q

what is the function of the ileum

A

nutrient absorption

40
Q

what are brush border enzymes

A

integral part of the membrane (not free in lumen)
peptidases
lactases
sucrase
maltase

41
Q

what do chief cells secrete

A

secrete pepsinogen

42
Q

what do parietal cells secrete

A

HCl
- denatures proteins
activates pepsin (= endopeptase)

43
Q

what is mastication

A

mechanical digestions, moistens food

44
Q

what is a bolus

A

broken down and moistened food

45
Q

digestion in the mouth

A

carbohydrates - primary digestion
- starch broken down by a-amylase to maltotriose, maltose and a-limit dextrin
proteins - nothing
lipids - lingual lipase present but minor contribution

46
Q

what is chyme

A

food that is being churned in the stomach with gastric juice

47
Q

digestion in the stomach

A

carbohydrates - nothing
proteins - primary digestion
- HCl denatures proteins + activates pepsin
- endopeptidase that cleaves proteins to smaller peptides
lipids - gastric lipase present but minor contribution

48
Q

digestion in the duodenum

A

CARBOHYDRATES
a-amylase further digests starch
brush border disaccharides (maltase, sucrase, lactase)
= monosaccharides
PROTEINS
cleaves by trypsin (activates other enzymes), chymotrypsin, elastase, carboxypeptidases
produces increasingly smaller peptides/ dipeptides
brus border peptides produce dipeptides/ amino acids
LIPIDS
pancreatic juice digests lipids into monoglycerides and fatty acids
phospholipase digests phospholipids to lysolecithin + fatty acids

49
Q

explain passive absorption

A

slow
needs conc. gradient or charge gradient

50
Q

explain facilitated transport

A

slightly faster
involved membrane carrier
controllable

51
Q

explain active transport

A

uses energy
fast
uses membrane carrier
controllable

52
Q

explain formation of micelles

A

formed in the lumen with the aid of bile salts
water soluble

53
Q

explain absorption of lipids

A

micelles formed
diffuse to the apical brush border epithelial cells
- contents released and diffuse down their conc. gradient into the cell
if the fatty acid chains are short they diffuse directly into the bloodstream
everything else in chylomicrons
- move to basolateral membrane and exit via exocytosis
- too large to enter vascular capillaries so are secreted into lymphatics
carried to thoracic duct
empties into the bloodstream`

54
Q

explain the activation of pancreatic zymogens

A

enterokinase -> trypsinogen -> trypsin -> all others

55
Q

explain the process of absorption of monosaccharides

A

glucose + galactose
- Na/ glucose transporter -> SGLT1
- Na+/K+ pumps on basolateral membrane shovel out Na+ molecules to create a conc. gradient (maintaining)
GLUT5 facilitated transport protein for fructose
GLUT2 out of the cell

56
Q

explain the absorption of amino acids

A

similar to monosaccharides
Na+ dependent amino acid transporters
Na+/ K+ pump maintains the Na+ gradient in the cell
dipeptides/ tripeptides
- cotransport with H+
- further digested inside the cell
facilitated diffusion basolateral membrane

Week 10 (3 decks)

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