Glucogen Synthesis and Regulation Flashcards
Diffrence in function and structure of glucose vs glycogen
Glycogen is polymer of glucose
monosaccharide vs polysaccharide
Gluocse - 10g
glucose can instead be stored as glycogen - 400g in tissue stores
as glucose is osmatically active but glucagon has low osmarlity
What is liver glycogen responsible for?
The liver is sensitive to blood glucose concentration
Glucogen conc is larger per gram in liver then muscle but there are more muscles then liver
liver maintains constant levels of glucose in the blood using insulin ang glycagon
What is muscle glycogen responsible for?
rapid source of glucose for muscle contraction
The muscle is sensitive to energy needs of the tissue
It is sensitive to adrenaline, calcium, AMP, ATP
How is glycogen used as fuel in muscle for exercise?
Glycogen in muscle is broken down and degraded into glucose 6-p then it enters glycolyissis to provide energy for contraction
Describe glycogen’s structure?
Glycogen has a branched structure
a 1-4 glycoside linkages
a 1-6 glycoside linkages
End - terminal end
When glycogen starts - resducing end of polymer
Features of biosynthetic pathways
* ATP or UTP or GTP (input of energy needed) are needed as cofactors (to ‘drive the reactions forward’)
* one or more enzyme reactions will be irreversible, and alternative enzymes are used for the ‘opposite direction’
* enzyme reactions at the beginning or end of the pathway are tightly regulated
What are the first stages of glycogen synthesis from glucose?
STEP 1
Glycose to glycogen
- ATP used
step 1
Glucose ——-> Glucose 6-phosphate <——> Glucose 1-phosphate
Enzymes
- hexokinase
-glucokinase
- phosphoglucomutase
Step 2 of glycogen synthesis from glucose?
slide 11
FORMATION OF UDP GLUCOSE
Transferase enzyme
GLUCOSE-1-P + UTP ———————————> PPi (phosphate) + UDP Glucose
- Put in energy (Anabolic pathway)
Step 2 of glycogen synthesis from glucose?
slide 12
ADDITION OF GLUCOSE UNIT TO PROTEIN PRIMER
UDP-glucose + Protein Primer (GLYCOGENIN)
————–> UDP
- Use glycogen synthase
Step 3 of glycogen synthesis from glucose?
slide 13
UDP-glucose used and UDP removed
Glucose released and forms a 1-4 glycosidic linkages between glucose
Step 4 of glycogen synthesis from glucose?
slide 14
BRANCH POINTS are introduced into the structure of glycogen
- branches off from glucose
- forms a 1-6 bond
How the branched structure of glycogen formed?
Glycogen synthase and branching enzyme produce the branched structure of glycogen
branching enzyme introduces site for new chains
Glycogen synthase enzyme extends the straight chains
Site of action of branching enzyme - about 5 units
How is Glycogen synthase regulated?
**By Phosphorlylation
How is glycogen synthase activated?
Activated - By dephosphorlyation
Protein phosphatase used
Phosphate removed
How is glycogen synthase inactivated?
Inactivated byphosphorlation
* Protein Kinase Used
* ATP used
* Pi added