Summary
Summary
- Course
- Institution
- Book
Summary “Biochemistry: A Short Course” (John L. Tymoczko) Section 11 (H24, H25 and H26). This summary is made for the course “Cell to Molecule” of the Veterinary Medicine Study.
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
More summaries for
-
Biochemistry A Short Course 3rd Edition Tymoczko Test Bank
-
TEST BANK for Biochemistry: A Short Course, 4th Edition, John Tymoczko, Berg, Gregory Gatto, Lubert Stryer | Complete 41 Chapters
-
Testbank of tymoczko biochemistry course 3rd edition
Seller
Follow
ankejesse
Reviews received
Content preview
Section 11 - Glycogen Metabolism and thePentose Phosphate Pathway
Chapter 24 - Glycogen Degradation
● Glycogen → large, branched polymer of glucose residues
○ Most glucose residues are linked by α-1,4-glycosidic bonds
○ Branches at about every 12th residue are created by α-1,6-glycosidic bonds
○ Not as energy-rich as fatty acids
○ The readily mobilized glucose from glycogen is a good source of energy for
sudden, strenuous activity → can also be used for anaerobic activity
○ Main sites of storage: Liver and skeletal muscle
○ In the liver, glycogen synthesis and degradation are regulated to maintain the
concentration of glucose in the blood required to meet the needs of the
organism as a whole
24.1 - Glycogen Breakdown Requires Several Enzymes
● Efficiënt breakdown of glycogen to provide glucose 6-phosphate for further
metabolism requires 4 enzyme activities
○ 1 to degrade glycogen
○ 2 to remodel glycogen so that it remains a substrate for degradation
○ 1 to convert the product of glycogen breakdown into a form suitable for further
metabolism
● Phosphorylase cleavers glycogen to release glucose 1-phosphate
○ Glycogen phosphorylase (key regulatory enzyme in glycogen breakdown)
■ Cleaves its substrate by the addition of orthophosphate (Pi) to yield
glucose 1-phosphate
● Phosphorolysis: the cleavage of a bond by the addition of Pi
■ Glycogen(n) + Pi ⇌ glucose 1-phosphate + glycogen(n-1)
■ Phosphorylase catalyzes the sequential
removal of glycosyl residues from the
nonreducing ends of the glycogen
molecule
● Pi splits the glycosidic linkage
between C-1 of the terminal
residue and C-4 of the adjacent one
■ The phosphorolytic cleavage of glycogen is energetically
advantageous because the released sugar is already phosphorylated
, ● A debranching enzyme is also needed for the breakdown of
glycogen
○ α-1,6-glycosidic bonds are not susceptible to
cleavage by phosphorylase → stops cleaving α-1,4
linkages when it reached a residue 4 residues away
from a branch point
○ Transferase shifts a block of 3 glucosyl residues
from one outer branch to another → exposes a
single glucose residue joined by an α-1,6-glycosidic
linkage
○ α-1,6-glucosidase (debranching enzyme)
hydrolyzes the α-1,6-glycosidic bond → release of
a free glucose molecule
○ The free glucose molecule is phosphorylated by
hexokinase
● Phosphoglucomutase converts glucose 1-phosphate into glucose 6-phosphate
○ To catalyze this shift → enzyme exchanges a phosphoryl group with the
substrate
○ The active site of mutase contains a phosphorylated serine residue
■ The phosphoryl group is transferred from the serine residue to the C-6
hydroxyl group of glucose 1-phosphate to form glucose
1,6-biphosphate
■ The C-1 phosphoryl group of this intermediate → shuttled to the same
serine residue → formation of glucose 6-phosphate and the
regeneration of the phosphoenzyme
● The liver contains glucose 6-phosphatase → the muscle does not
○ A major function of the liver is to maintain a nearly constant concentration of
glucose in the blood
○ Glucose 6-phosphatase enables glucose to leave the liver instead of
phosphorylated glucose
■ Cleaves the phosphoryl group to form free glucose and Pi
■ Glucose 6-phosphatase + H2O → glucose + Pi
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller ankejesse. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.27. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
70055 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now