Exam 5 content

Question 1

what are olgiosaccharides?

Answer 1

contain two or more monosaccharides linked by o-glycosidic bonds

Question 2

What are dissacharides?

Answer 2

two monosaccharides joined by o-glycosidic bonds

Question 3

What do glycosyltransferases do?

Answer 3

catalyze the formation of glycosidic bonds

Question 4

What is the monosaccharide substrate for glycosyltransferases activated by?

Answer 4

Uridine diphosphate (UDP)

Question 5

What are large polysaccharides called if all the monomer are the same

Answer 5

homopolymer

Question 6

How are glucose molecules linked together to form glycogen?

Answer 6

linked by alpha-1,4- glycosidic bonds with branches formed by alpha-1,6,glycosidic bonds every 12 glucose molecules

Question 7

What is amylose

Answer 7

storage form of glucose in plants it is a linear polymer linked by alpha-1,4- glycosidic bonds

Question 8

What is amylopectin

Answer 8

branched polymer with and alpha-1,6- glycosidic bond for every 30 alpha-1,4-glycosidic bonds

Question 9

What is glucose stored as glycogen?

Answer 9

because storing glucose molecule increases the osmotic pressure leading to more water inside the cell which can lead to swelling and lysis while storing it ass glycogen only has the osmostic pressure of one molecule.

Question 9

How is cellulose linked together

Answer 9

B-1,4-glycosidic bonds which creates a straight chain which can interact with other cellulose to form fibrils While starch and glycogen create cylinders which are suitable for storage

Question 10

where are the largest stores of glycogen found?

Answer 10

in the liver and the muscle

Question 11

What are the 4 enzymes involved in glycogen breakdown?

Answer 11

• glycogen phosphorylase
• transferase
• a-1,6-glucosidase
• phosphoglucomutase

Question 12

What does glycogen phosphorylase do?

Answer 12

degrades glycogen from the non-reducing ends of the glycogen molecules yielding glucose-1-phosphate (cannot do near branch has to be atleast 4 away)

Question 13

what does transferase do?

Answer 13

shift the small olgiosaccharide near the branch point to a nearby chain making the glucose moieties more accesible to the phosphorylase

Question 14

What does a-1,6-glucosidase do?

Answer 14

it is the debranching enzyme cleave the a-1,6- bond at the branch point releasing a free glucose (not glucose-1-phosphate)

Question 15

What does phosphoglucomutase do?

Answer 15

forms glucose-6-phosphate from glucose-1-phosphate with the use of a glucose 1,6-bisphosphate intermediate (see 144 is phosphoryl group carrier important for this reaction)

Question 16

What is the key regulatory enzyme for the degradation of glycogen?

Answer 16

Glycogen Phosphorylase

Question 17

What are the two from glycogen phosphorylase that exist in?

Answer 17

The less active form which is the B form and the more active a form

Question 18

What does the a form have that the b form does not have?

Answer 18

a phosphorylated serine-14 residue

Question 19

What is the relationship between liver phosphorylase and muscle phosphorylase?

Answer 19

They are isozymes

Question 20

What equilibrium does the a form and b form display

Answer 20

R-T equilibrium

Question 21

In the B form which state is favored

Answer 21

T state

Question 22

In the A form which state is favored

Answer 22

R state

Question 23

What is the default state of liver phosphorylase? and why is this state favored

Answer 23

A form R state to maintain adequate blood levels of glucose

Question 24

What is the negative regulator of liver phosphorylase and what does it do?

Answer 24

Glucose facilitates the transition from the R state to the T state

Question 25

What is the default state of muscle phosphorylase and why?

Answer 25

b form T state because under mst condition muscle phosphorylase b is inactive

Question 26

What is the regulation for muscle phosphorylase?

Answer 26

When energy is needed, there is an increase in AMP levels, and the phosphorylase binds to the AMP, which stabilizes the R state The T state of the phosphorylase is stabilized by ATP and glucose-6-phosphate

Question 27

What is glycogen phosphorylase phosphorylated or stimulated by?

Answer 27

G-protein signaling pathways of hormones glucagon and epinephrine

Question 28

What is phosphorylase kinase responsible for?

Answer 28

The conversion of glycogen phosphorylation from the unphosphorylated b state to the a state

Question 29

When is the phosphorylase kinase the most active?

Answer 29

The delta subunit of the phosphorylase kinase is the calcium receptor so it is most active when it is phosphorylated and bound to calcium

Question 30

What are the mechanisms that turn off glycogen degradation?

Answer 30

1. GTPase 2. pphosphodiesterase --> cAMP into AMP 3. protein phosphatase 1 which removes phosphoryl groups from phosphorylase kinase and glycogen phosphorylase

Question 31

What correlates with the onset of fatigue?

Answer 31

glycogen depletion