Lecture 23 - Glucose as a fuel molecule #1

Question 1

What is glucose?

Answer 1

A hexose simple sugar monosaccharide

Question 2

What is hexose?

Answer 2

6 Carbons

Question 3

What are the 3 types of drawn conformations of glucose?

Answer 3

Ring, Open, Chair

Question 4

What is the chemical structure of glucose?

Answer 4

C6H12O6

Question 5

What is a carbohydrate?

Answer 5

A large macromolecule / polysaccharide

Question 6

What are sources of glucose from carbohydrates?

Answer 6

Starch from plants and glycogen from meat

Question 7

What is starch?

Answer 7

A polymer made up of up to 1 million glucose units joined by glycosidic bonds

Question 8

What are the two forms of starch?

Answer 8

Amylose and amylopectin

Question 9

What is the structure of amylose?

Answer 9

A linear polymer of glucose units

Question 10

What is the structure of amylopectin?

Answer 10

A branched polymer of glucose units

Question 11

What is glycogen?

Answer 11

A branched polymer of glucose units

Question 12

What is a disaccharide?

Answer 12

Two monosaccharides joined by a glycosidic bond

Question 13

What are some examples of disaccharides?

Answer 13

Sucrose, lactose, maltose

Question 14

What is the structure of sucrose?

Answer 14

A glucose bound to a fructose by a glycosidic bond

Question 15

Where are disaccharides found in the diet?

Answer 15

Fruit and raw sugar

Question 16

What enzyme cleaves glycosidic bonds from polysaccharides to disaccharides?

Answer 16

Amylase through hydrolysis

Question 17

What enzymes cleave the glycosidic bonds from disaccharides to monosaccharides?

Answer 17

Specific enzymes e.g. sucrase for sucrose

Question 18

What is the end result of digestion of carbohydrates?

Answer 18

Glucose in the GI tract

Question 19

Are sugars polar or non polar?

Answer 19

Highly polar

Question 20

Are sugars water or lipid soluble?

Answer 20

Water

Question 21

How do glucose molecules cross the lipid membrane?

Answer 21

through specific transporter proteins anchored in the membrane

Question 22

What are the two types of transport?

Answer 22

Active and facilitated transport

Question 23

What is active transport?

Answer 23

The movement molecules against a concentration gradient, requiring energy input

Question 24

What is facilitated transport?

Answer 24

The movement of molecules down a concentration gradient, not requiring energy input

Question 25

What transporter protein transports glucose via active transport across the apical membrane in the GI tract?

Answer 25

The sodium-glucose linked transporter (SGLT) (facilitative)

Question 26

What moves down their concentration gradient through the SGLT?

Answer 26

Na+ (into cell from GIT)

Question 27

What moves up their concentration gradient through the SGLT?

Answer 27

Glucose (into cell from GIT)

Question 28

What transporter protein, found on the baso-lateral membrane transports glucose via facilitated transport across the membrane into the interstitial fluid?

Answer 28

GLUT2 (facilitative)

Question 29

What transporter protein, located on the baso-lateral membrane, creates the low concentration gradient without the cell?

Answer 29

Na+/K+ ATPase - Na+ pumped out of cell - K+ pumped into cell (Active) - energy from ATP hydrolysis

Question 30

What happens to the K+ that was pumped into the cell via the Na+/K+ ATPase?

Answer 30

returns to interstitial fluid, down concentration gradient, through a channel protein to be used by the Na+/K+ ATPase pump again.

Question 31

How is glucose used as a fuel molecule?

Answer 31

It is oxidised in glycolysis (in all organisms) which usually occurs in the cytoplasm in eukaryotes

Question 32

Why is glucose essential as fuel for red blood cells?

Answer 32

RBCS do not have mitochondria and can therefore not utilise other pathways

Question 33

What is the energy requirement in the brain?

Answer 33

120g of glucose per day

Question 34

Do brain cells have mitochondria?

Answer 34

Yes

Question 35

What is the traditional view on why the brain favours glucose?

Answer 35

Glucose easily crosses the blood-brain barrier and fats do not

Question 36

What is the modern hypothesis as to why the brain prefers glucose?

Answer 36

It is safer, providing a quicker source of ATP without the risk of damage

Question 37

Why is glucose favoured as a energy molecule in the eye cells?

Answer 37

High amounts of blood vessels and mitochondria would refract the light, so these are limited and glucose does not require either

Question 38

Which muscle cells use fats as fuel?

Answer 38

Red muscle cells, for endurance

Question 39

Which muscle cells use glucose as fuel?

Answer 39

White muscle cells, for sprinting