Nutrient digestion

Question 1

what are the 3 monosaccharides?

Answer 1

glucose
galactose
fructose

Question 2

what is the bond between two monosaccharides to form a disaccharide called?

Answer 2

glycosidic bond

Question 3

where is amylase found

Answer 3

saliva

pancreas

Question 4

Which type of glycosidic bond is found in starch?

Answer 4

alpha- 1,4

Question 5

Which type of glycosidic bond is found in cellulose?

Answer 5

Beta- 1,4

Question 6

In regards to the cells that line the intestine, what is the name for the side that faces inside the lumen

Answer 6

brush border/apical surface

Question 7

In regards to the cells that line the intestine, what is the name for the side that faces into the lumen

Answer 7

apical membrane/brush border - specialised for absorption

Question 8

what is required to absorb glucose?

Answer 8

Sodium

without the sodium potassium ATPase creating a Na+ gradient you cannot absorb glucose

Question 9

what is the SGLT1 protein

Answer 9

A secondary active transporter molecule involved in glucose transport.

Takes Na+ and glucose into the cell. Gets it’s energy from the Na+ gradient created by the Na+/K+ pump on the basolateral membrane

Question 10

what is GLUT-2 and what is it’s function?

Answer 10

It is a facilitator of diffusion. It is a carrier protein that sits in the basolateral membrane in the intestine

no energy required

Question 11

what is the name of the fructose transporter in the small intestine?

Answer 11

GLUT 5

Question 12

what is the main difference between glucose and fructose movement across the membrane?

Answer 12

when glucose moves across there is already sodium transport and so there is also water movement but with fructose there is no Na+ movement so no H20 movement

Question 13

what are proteases or peptidases

Answer 13

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

Question 14

what is an endopeptidase

Answer 14

chops a peptide chain in half each time and reduces it in size that way

Question 15

what is an exopeptidase

Answer 15

chops off the peptide bond at each end of the chain reduces it in size that way

Question 16

dipeptide transport overview

Answer 16

NHE3 is on every epithelial cell. It takes in Na+ and pushes out H+ making acid microclimate outside cell

this drives PepT1 protein (dipeptide)

Question 17

what form is almost all ingested fat in?

Answer 17

triacylglycerol

Question 18

where is fat digested and with which enzyme?

Answer 18

small intestine
pancreatic lipase (water soluble)

Question 19

Is digestion of fat a slow or fast process?

Answer 19

slow - it can only take place at the surface of a fat/lipid droplet however enzyme catalyst can speed this up

Question 20

chemical equation for fat digestion?

Answer 20

triacylglycerol —> monoglyceride + 2 fatty acids

Question 21

what does emulsifcation require?

Answer 21

mechanical disruption of large lipid droplets ie vigorous mixing to break down fat droplets (smooth muscle contraction in our gut grinds and mixes lumenal contents)

emulsifying agent - ie bile salts and phospholipids, amphiphatic molecules

Question 22

what product enhances the process of absorption?

Answer 22

formation of micelles

Question 23

what is a micelle? role?

Answer 23

bile salt + monoglycerides + fatty acids + phospholipids

it transports fats to the surface (fat taxi) and releases them there. Micelles do not pass through (too big)– only the fat molecules

Question 24

where do FA’s and monoglycerides enter to when they enter an epithelial cell? what happens here

Answer 24

smooth endoplasmic reticulum (sER) they are reformed into triacylglycerols

Question 25

How are triacylglycerol droplets transported through a cell?

Answer 25

in vesicles formed from sER membrane

Question 26

What do chylomicrons pass into which transports them through in-between endothelial cells?

Answer 26

They pass into lacteals as they can't get through the tight junctions of the capillary basement membrane. So, this means the fat passes into the lymphatic system and not into the blood. The fat and fat soluble vitamins form chyle (this fluid contains lymph and emulsified fats, or free fatty acids). Lymphatic vessels then transport them into the blood.

Question 27

name 4 fat soluble vitamins

Answer 27

A D E K

Question 28

Name some water soluble vitamins. How are they absorbed?

Answer 28

B group C group Folic acid Absorbed either by passive diffusion or carrier-mediated transport.

Question 29

What's so special about vitamin B12?

Answer 29

Vitamin B12 is a large charged molecule that binds to intrinsic factor in the stomach. Your body doesn't produce B12 so it must be acquired from our diet. It is absorbed in the distal ileum.

Question 30

What can B12 deficiency lead to?

Answer 30

Pernicious anaemia (failure of RBC maturation which is needed for efficient O2 carrying). Treatment - injections

Question 31

How is iron transported through cells?

Answer 31

Iron is transported across the brush border membrane via DMT1 into duodenal enterocytes. It is incorporated into ferritin (a protein-iron complex which acts to store iron intracellularly). Unbound iron goes into the blood and binds to transferrin which takes it to the liver to prevent toxicity.

Question 32

what is ferritin?

Answer 32

intracellular iron storage - creates a cage like structure around the iron

Question 33

what does iron bind to in the blood?

Answer 33

transferrin

Question 34

What is the link between Hyperaemia and Anaemia with ferritin levels?

Answer 34

Hyperaemia => Increased ferritin levels = more iron bound in the duodenal enterocytes in protein-iron complex ie more iron being stored away. Can be released when needed. Anaemia => Decreased ferritin levels so there is more iron released into the blood. RBCs need iron to form normally and carry O2 efficiently but in anaemia there aren't enough RBCs for iron to attach to.

Question 35

Give 3 examples of emulsifying agents

Answer 35

Bile salts Phospholipids Amphiphatic molecules

Question 36

When/why does a micelle release its content/break down?

Answer 36

The micelle moves into acid microclimate which removes the charge off free fatty acids, destabilising their structure The micelle then releases its contents which pass through the membrane without it.

Question 37

function of golgi apparatus in fat digestion

Answer 37

fat molecules are trafficked through the G.A which sorts them to make sure they go where they need to go.

Question 38

what is a lacteal and what is their importance

Answer 38

a branch of the lymphatic system they take fat molecules into the lymphatic system and prevent them from getting into the blood circulation

Question 39

How does iron get absorbed in the duodenum?

Answer 39

it binds to DMT1 receptor in the brush border

Question 40

What is the basolateral membrane?

Answer 40

the term basolateral refers to the membrane on the base and sides of the cell. The basolateral membrane forms a barrier between the cell and the blood and/or other cells