Digestion 1

Question 1

What are the 6 types of membrane transport?

Answer 1

• Simple Diffusion
• Facilitated Diffusion
• Active Transport
• Receptor Mediated Endocytosis
• Pinocytosis (cell drinking like pint)
• Exocytosis

Question 2

What is the action of an antiporter?

Answer 2

EXCHANGE - A goes in, B goes out

Question 3

What is the action of a symporter?

Answer 3

COTRANSPORT - A and B simultaneously go in/out

Question 4

Endocytosis is _______ and therefore is ________.

Answer 4

receptor mediated and therefore is specific and saturable.

Question 5

Where do endosomes originate?

Answer 5

The golgi aparatus

Question 6

What is endo/exocytosis fundamental to and what is it exploited by?

Answer 6

Fundamental to neurotransmission, signal transduction and regulation of plasma membrane activities

Exploited by viruses, bacteria and toxins to gain entry into the cell

Question 7

What is the key structural component of the human small intestine?

Answer 7

Villi

Question 8

What 2 types of cells are villi covered in?

Answer 8

Mature cells (enterocytes) and mucus producing goblet cells

Question 9

Histologically, what type of cells are enterocytes?

Answer 9

Columnar epithelial cells

Question 10

Thousands of what are present of on the luminal surface of each enterocyte?

Answer 10

Thousands of Microvilli

Question 11

What are enterocytes responsible for?

Answer 11

Absorption and some digestion

Question 12

What do the microvilli provide?

Answer 12

A large surface area to facilitate absorption

Question 13

What must happen to large globules of dietary fat before digestion can occur?

Answer 13

globules must be emulsified

Question 14

By which enzyme does partial lipid hydrolysis occur in the stomach?

Answer 14

gastric lipase

Question 15

Why is partial lipid hydrolysis in the stomach slow?

Answer 15

due to separate aqueous and lipid phases

Question 16

What is the abbreviation for a triacylglyceride molecule?

Answer 16

TAG

Question 17

Where does emulsification happen?

Answer 17

In the stomach

Question 18

What does the fat globule contain?

Answer 18

TAGs, Cholesterol esters, phospholipids

Question 19

What 2 major components of bile are necessary for the breakdown on the fat globule?

Answer 19

Bile salts and phospholipids

Question 20

What component of bile breaks down the big fat globule into the small fat droplet?

Answer 20

Phospholipids

Question 21

What does the breakdown into small fat droplets allow for?

Answer 21

Allows the small fat droplets to interact with the watery secretion (intestinal chyme)

Question 22

What component of bile facilitates the binding of the co-factor for pancreatic lipase and also the breakdown of the small fat droplet into the even smaller micelle?

Answer 22

Bile salts

Question 23

What is the name of the co-factor which helps pancreatic lipase to further break down the small fat droplet?

Answer 23

Co-lipase

Question 24

What does pancreatic lipase break the small fat droplet into?

Answer 24

FFAs and MAGs

Question 25

What are the other pancreatic enzymes which breakdown the cholesterol esters and the phospholipids of the big fat globule?

Answer 25

PLA2 and Carboxyl Ester Lipase

Question 26

What hormone stimulates the release of bile and pancreatic enzymes for digestion of big fat globules in the small intestine?

Answer 26

CCK

Question 27

What occurs when the small fat droplets start to get broken down into FFAs and MAGs?

Answer 27

Fat soluble vitamins are absorbed and micelle formation occurs

Question 28

What are the 5 products of lipid digestion?

Answer 28

- Fatty Acids - MAGs and DAGs - Cholesterol - Phospholipids - Glycerol

Question 29

What is the function of micelles?

Answer 29

To deliver the products of lipid digestion to the brush border of the enterocytes where they diffuse into the cell

Question 30

How are TAGs and CEs formed again inside the enterocyte?

Answer 30

- TAGs are re-synthesised by acyltransferases - phospholipids are acylated into phosphatic acid and then into TAG - Cholesterol is acylated by acyltransferases to form cholesterol esters

Question 31

What do the TAGs and CEs inside the enterocyte join with and to produce what?

Answer 31

TAGs and CE join with apolipoprotein to produce a chylomicron

Question 32

Where do these chylomicrons go next?

Answer 32

Lacteal --> lymph --> back into circulation at the thoracic duct

Question 33

Give examples of MONOSACCHARIDES

Answer 33

glucose, galactose, fructose

Question 34

Give examples of DISACCHARIDES

Answer 34

maltose, sucrose, lactose

Question 35

Give examples of POLYSACCHARIDES

Answer 35

starch, glycogen

Question 36

What must happen to di- and polysaccharides before absorption?

Answer 36

Digestion

Question 37

How are disaccharides digested/broken down and where?

Answer 37

Disaccharides are broken down by specific disaccharidases on the intestinal brush border

Question 38

How are polysaccharides digested/broken down?

Answer 38

Polysaccharides require salivary and pancreatic enzymes for digestion

Question 39

What are the names of the specific disaccharidases for the examples of disaccharides already given?

Answer 39

maltase, sucrase, lactase

Question 40

What is the one disaccharidase that is non-inducible?

Answer 40

Lactase

Question 41

What is the rate limiting step for the absorption of disaccharides with inducible disaccharidases?

Answer 41

Transport of the monomeric sugars

Question 42

What is the rate limiting step for the absorption of disaccharides with non-inducible disaccharidases?

Answer 42

hydrolysis

Question 43

By what mechanism are primary monosaccharides (glucose, galactose, fructose) absorbed?

Answer 43

Carrier-mediated mechanisms

Question 44

What is the function of the Sodium-Dependent Glucose Transporter?

Answer 44

To transport glucose (and galactose) into the enterocyte across the brush border.

Question 45

What is the function of the Sodium-Independent GLUT5?

Answer 45

To transport fructose into the enterocyte across the brush border.

Question 46

What is the function of the GLUT2?

Answer 46

To transport glucose, galactose and fructose into the blood from the enterocyte.

Question 47

What maintains the concentration of sodium for the sodium-dependent glucose transporter?

Answer 47

Na+/K+ ATPase

Question 48

Give 1 example of why the relationship between sodium and glucose has vast clinical consequences

Answer 48

Dehydrated patients where found to absorb sodium much better when glucose was also provided

Question 49

The GLUT family have been looked at when the studying the pathogenesis of which disease?

Answer 49

Diabetes Melitus