GI physiology (week 2)

Question 1

why do we store things as macromolecules?

Answer 1

the reduce the osmotic challenge (osmosis depends on the number of molecules, not the size)

Question 2

name the 3 hexose sugars and where are they absorbed?

Answer 2

glucose, fructose, and galactose

small intestine

Question 3

what are the disaccharides and what are they formed from?

Answer 3

lactose - glucose and galactose

sucrose - glucose and fructose

maltose - glucose and glucose

Question 4

what are the types of starch and what are they broken down by?

Answer 4

a-amylose: glucose in straight chain

amylopectin: highly branched glucose chain

amlyases hydrolise the bonds (saliva and pancreas)

Question 5

what type of bonds are in cellulose and what breaks them?

Answer 5

B 1-4 glycosidic bonds, bacteria which have cellulase

Question 6

what two membranes do the epithelial cells have?

Answer 6

basolateral and apical membranes

Question 7

what do transporters allow us to transport into the epithelial cells?

Answer 7

water soluble molecules (e.g. glucose) and ions

Question 8

what is the transporter that brings glucose to the lumen called?

Answer 8

SGLT1 (in the apical membrane of small intestine), and needs 2 sodium to bind to it as well to cause a conformational change for it to work). It is the sodium gradient that brings it in as constant because of Na-K pump

Question 9

what is the glucose transporter on the basolateral membrane called?

Answer 9

glut-2 (uses secondary active transport)

Question 10

what 2 sugars does SGLT-1 transport?

Answer 10

glucose and galactose

Question 11

what is the intestinal fructose transporter?

Answer 11

Glut-5 and leaves the cell into the blood same as glucose (through glut-2)

Question 12

what are the two types of exopeptidases and where do they work on?

Answer 12

aminopeptidases - works on the terminal amino acids

carboxypeptidases - works on the carboxyl end

Question 13

what is triacylglycerol broken down into and by which enzyme?

Answer 13

pancreatic lipase (water-soluble enzyme - so can only work on outside of droplets)

monoglyceride + 2 fatty acids

Question 14

what does emulsification require?

Answer 14

smooth muscle in stomach to cause mechanical disruption

emulsifying agents (bile salts and phospholipids)

Question 15

what does a micelle consist of and what happens when it enters the acid microclimate?

Answer 15

product of digestion - bile salts, fatty acids, monoglycerides, and phospholipids.

acid microclimate has low pH and takes away micelle hydrogen ion which releases free fatty acids to diffuse across intestine

Question 16

what does saliva consist of?

Answer 16

mucins (protein) + water = mucus, A-amylase (breaks A-glyosidic bonds), electrolytes (tonicity and pH), and lysozyme

Question 17

what are the salivary glands?

Answer 17

parotid - in front of the ear

sublingual - under the tongue

submandibular - under the jaw

these are all exocrine glands

Question 18

describe serous and mucous alveoli

Answer 18

serous secretes lysozymes and mucous secretes mucin

Question 19

describe the parasympathetic and sympathetic control of the glands

Answer 19

parasympathetic - cranial nerves 7 (facial) and glossopharyngeal nerves 9 - creates watery saliva

sympathetic - small volume, thick saliva, has a high mucous content (if stimulate A1 receptors, causes high mucus content. if stimulate B1 receptors, high amylase content)