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yr2 > Digestion & Absorption > Flashcards

Digestion & Absorption Flashcards

1
Q

Principle dietary nutrients

A
  • Carbs
  • Protein
  • Fat
  • Vitamins
  • Mineral
  • Water (absorbed through skin)
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2
Q

Monosaccharides

A
  • Glucose
  • Galactose
  • Frutose
    (all are 6C sugars)
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3
Q

Lactose is composed of

A

Glucose + Galactose (lactase)

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4
Q

Sucrose is composed of

A

Glucose + Fructose (sucrase)

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5
Q

Maltose is composed of

A

Glucose + Glucose (maltase)

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6
Q

Disaccharides

A
  • 2 monosaccharides linked together by glycosidic bond

- Broken down to constituent monomers by brush border enzymes in small intestine

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7
Q

Polysaccharides

A
  1. Starch
  2. Cellulose
  3. Glycogen
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8
Q

Plant carbs

A

Starch & Cellulose

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9
Q

Animal carbs

A

Glycogen

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10
Q

Starch

A
  • Plant storage form of glucose
  • α-amylose: glucose linked in straight chains
  • Amylopectin: glucose chains highly branched
  • Glucose monomers linked by α-1,4 glycosidic bonds hydrolysed by amylases (saliva, pancreas)
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11
Q

Cellulose

A
  • Constituent of plant cell walls
  • Unbranched, linear chains of glucose monomers linked by β-1,4 glycosidic bonds
  • Dietary fibre (no enzymatic digestion in vertebrates - require bacteria (cellulase))
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12
Q

Glycogen

A
  • Animal storage form of glucose

- Glucose monomers linked by α-1,4 glycosidic bonds

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13
Q

Animals can only digest

A

α-1,4 glycosidic bonds (starch, glycogen) using amylase

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14
Q

Paracellular

A

Absorbed in tight junctions (water)

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15
Q

Transcellular

A

Goes through the cell

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16
Q

Vectorial transport

A

Through transport proteins

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17
Q

SGLT1 & GLUT2 transport:

A

glucose & galactose

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18
Q

GLUT1 found in

A

RBC

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19
Q

SGLT1 found in

A

Kidney

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20
Q

Describe the primary active transport system

A

Na pumped out of cell, into blood and creates a gradient.
Na will then move into cell from lumen and bring glucose with it using sodium glucose transporter
Glucose transported into blood by GLUT2 transporter
Water goes into blood through osmotic gradient through tight junction
Secondary active transport system

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21
Q

Fructose transport system

A

GLUT5 and then GLUT2 transports fructose

Does not require Na, so no water uptake due to no Na uptake

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22
Q

What are peptides

A

Small proteins

3-10 amino acids in length

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23
Q

Proteins undergo

A

Post-translation modification

e.g addition of CHO = glycoprotein; Lipid = lipoprotein

24
Q

What are proteases/peptidases

A

Enzymes which hydrolyse peptide bonds and reduce proteins/peptides to amino acids

25
Q

What do Endopeptidases do?

A

Breaks peptide bonds in central region

26
Q

What do Exopeptidases do?

A

Break peptide bonds at terminal ends of protein (amino peptidases (amino end) & carboxypeptides (carboxyl end))

27
Q

Describe the secondary active transport system

A

Na pumped into blood, Na gradient made and amino acid moves in with Na into cell by sodium amino acid transporter (SAAT1)
Amino acid moved into blood through its own transporter
Water moved into blood through tight junction
Golgi apparatus processed the amino acids in the cell

28
Q

Dipeptides and tripeptides transport

A

Dipeptides and tripeptides can be absorbed through PepT1 transporter that moves in peptide with hydrogen molecule
Hydrogen then pumped out with sodium hydrogen exchanger (NHE3), Na moved into cell from lumen
Na moved out of cell through sodium potassium pump
Peptide moves into blood through an unknown transporter

29
Q

All ingested fat is in the form of

A

Triaglycerol

30
Q

Fat digestion in small intestine is by

A

Pancreatic lipase

31
Q

Is lipase a water-soluble enzyme?

A

Yes

32
Q

Emulsification:

A

Dividing large lipid droplets into smaller droplets (1mm diameter) - increased surface area & accessibility to lipase action

33
Q

What does emulsification require?

A
  • Mechanical disruption of large lipid droplets into small droplets
  • Emulsifying agent - prevents small droplets reforming into large droplets
34
Q

Bile secretes:

A

bile salts + phospholipids

35
Q

Absorption of lipase digestion products is enhanced by formation of

A

Micelles

36
Q

Micelles are

A

similar to emulsion droplets but much smaller (4-7µm diameter)

37
Q

Micelles formed from:

A

bile salt + monoglycerides + fatty acids + phospholipids

38
Q

Polar portions of molecules form at

A

micelle surface

39
Q

Non-polar portions form

A

micelle core

40
Q

Micelle breakdown process

A
  1. Release of small amounts of free fatty acids & monoglycerides into solution
  2. There diffuse across plasma membrane to be absorbed
  3. Micelles are not absorbed
41
Q

After entering epithelial cells fatty acids & monoglycerides enter

A

smooth endoplasmic reticulum (here they are reformed into triacylglycerols by enzymes located within the sER)

42
Q

Triacylglycerol droplets coated within amphiphatic protein =

A

Emulsification

43
Q

Triacylglycerol droplets transported through cell in

A

Vesicles formed from sER membrane and then is processed by Golgi & exocytosed into ECF as chylomicrons

44
Q

Extracellular fat droplets =

A

Chylomicrons (also contain phospholipids, cholesterol & fat-soluble vitamins)

45
Q

Chylomicrons pass into lacteals between

A

endothelial cells

46
Q

Fat-soluble vitamins:

A

A,D,E,K

47
Q

Water-soluble vitamins:

A

B,C & folic acid

48
Q

Vitamin B12

A

large charged molecule

49
Q

Vitamin B12 binds to

A

intrinsic factor in stomach to form complex (which is absorbed via specific transport mechanism in distal ileum)

50
Q

B12 deficiency =

A

Pernicious anaemia (failure of RBC maturation)

51
Q

Iron enters duodenum cells via

A

divalent metal transporter (DMT1)

52
Q

Iron ions incorporated into

A

ferritin (protein-iron complex –> intracellular iron store)

53
Q

Unbound iron moved into blood & binds with

A

transferrin (protein)

54
Q

Hyperaemia leads to

A

increase ferritin, more bound in cell and wont be in blood

55
Q

Anaemia leads to

A

decrease ferritin, more iron released to blood

yr2 (9 decks)

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