Digestion & Absorption

Question 1

Principle dietary nutrients

Answer 1

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

Question 2

Monosaccharides

Answer 2

• Glucose
• Galactose
• Frutose
  (all are 6C sugars)

Question 3

Lactose is composed of

Answer 3

Glucose + Galactose (lactase)

Question 4

Sucrose is composed of

Answer 4

Glucose + Fructose (sucrase)

Question 5

Maltose is composed of

Answer 5

Glucose + Glucose (maltase)

Question 6

Disaccharides

Answer 6

• 2 monosaccharides linked together by glycosidic bond

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

Question 7

Polysaccharides

Answer 7

1. Starch
2. Cellulose
3. Glycogen

Question 8

Plant carbs

Answer 8

Starch & Cellulose

Question 9

Animal carbs

Answer 9

Glycogen

Question 10

Starch

Answer 10

• 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)

Question 11

Cellulose

Answer 11

• 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))

Question 12

Glycogen

Answer 12

• Animal storage form of glucose

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

Question 13

Animals can only digest

Answer 13

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

Question 14

Paracellular

Answer 14

Absorbed in tight junctions (water)

Question 15

Transcellular

Answer 15

Goes through the cell

Question 16

Vectorial transport

Answer 16

Through transport proteins

Question 17

SGLT1 & GLUT2 transport:

Answer 17

glucose & galactose

Question 18

GLUT1 found in

Answer 18

RBC

Question 19

SGLT1 found in

Answer 19

Kidney

Question 20

Describe the primary active transport system

Answer 20

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

Question 21

Fructose transport system

Answer 21

GLUT5 and then GLUT2 transports fructose

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

Question 22

What are peptides

Answer 22

Small proteins

3-10 amino acids in length

Question 23

Proteins undergo

Answer 23

Post-translation modification

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

Question 24

What are proteases/peptidases

Answer 24

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

Question 25

What do Endopeptidases do?

Answer 25

Breaks peptide bonds in central region

Question 26

What do Exopeptidases do?

Answer 26

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

Question 27

Describe the secondary active transport system

Answer 27

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

Question 28

Dipeptides and tripeptides transport

Answer 28

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

Question 29

All ingested fat is in the form of

Answer 29

Triaglycerol

Question 30

Fat digestion in small intestine is by

Answer 30

Pancreatic lipase

Question 31

Is lipase a water-soluble enzyme?

Answer 31

Yes

Question 32

Emulsification:

Answer 32

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

Question 33

What does emulsification require?

Answer 33

- Mechanical disruption of large lipid droplets into small droplets - Emulsifying agent - prevents small droplets reforming into large droplets

Question 34

Bile secretes:

Answer 34

bile salts + phospholipids

Question 35

Absorption of lipase digestion products is enhanced by formation of

Answer 35

Micelles

Question 36

Micelles are

Answer 36

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

Question 37

Micelles formed from:

Answer 37

bile salt + monoglycerides + fatty acids + phospholipids

Question 38

Polar portions of molecules form at

Answer 38

micelle surface

Question 39

Non-polar portions form

Answer 39

micelle core

Question 40

Micelle breakdown process

Answer 40

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

Question 41

After entering epithelial cells fatty acids & monoglycerides enter

Answer 41

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

Question 42

Triacylglycerol droplets coated within amphiphatic protein =

Answer 42

Emulsification

Question 43

Triacylglycerol droplets transported through cell in

Answer 43

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

Question 44

Extracellular fat droplets =

Answer 44

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

Question 45

Chylomicrons pass into lacteals between

Answer 45

endothelial cells

Question 46

Fat-soluble vitamins:

Answer 46

A,D,E,K

Question 47

Water-soluble vitamins:

Answer 47

B,C & folic acid

Question 48

Vitamin B12

Answer 48

large charged molecule

Question 49

Vitamin B12 binds to

Answer 49

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

Question 50

B12 deficiency =

Answer 50

Pernicious anaemia (failure of RBC maturation)

Question 51

Iron enters duodenum cells via

Answer 51

divalent metal transporter (DMT1)

Question 52

Iron ions incorporated into

Answer 52

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

Question 53

Unbound iron moved into blood & binds with

Answer 53

transferrin (protein)

Question 54

Hyperaemia leads to

Answer 54

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

Question 55

Anaemia leads to

Answer 55

decrease ferritin, more iron released to blood