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Chapter 18: Problem 4

Briefly outline the role of UDPG in glycogen biosynthesis.

Short Answer

Expert verified
UDPG is an activated glucose donor, formed from glucose-1-phosphate and UTP, used by glycogen synthase to extend the glycogen chain.

Step by step solution

01

- Understand UDPG

UDPG stands for uridine diphosphate glucose. It is a nucleotide sugar and acts as a glucose donor in the process of glycogen biosynthesis.
02

- Formation of UDPG

UDPG is formed from glucose-1-phosphate and UTP (uridine triphosphate) in a reaction catalyzed by the enzyme UDP-glucose pyrophosphorylase.
03

- Role in Glycogen Synthase Reaction

UDPG serves as an activated form of glucose. It donates glucose molecules to the growing glycogen chain through the action of the enzyme glycogen synthase.
04

- Extension of Glycogen Chain

Glycogen synthase transfers the glucose unit from UDPG to the non-reducing end of the glycogen molecule, extending the polysaccharide chain.
05

- Release of UDP

Once the glucose is added to the glycogen, UDP (uridine diphosphate) is released as a byproduct.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

UDP-glucose
UDP-glucose, also known as uridine diphosphate glucose, plays a critical role in glycogen biosynthesis. It is a molecule that combines glucose with uridine diphosphate, forming a high-energy compound ready for use. UDP-glucose acts as a glucose donor, meaning it transfers glucose units to the growing glycogen chain. This process is crucial for storing energy in the body, particularly in the liver and muscles. In summary:
  • UDP-glucose is a high-energy sugar nucleotide.
  • It donates glucose to glycogen chains for energy storage.
Glycogen Synthase
Glycogen synthase is the key enzyme responsible for forming glycogen from glucose. This enzyme catalyzes the transfer of glucose from UDP-glucose to the growing glycogen chain. Glycogen synthase is highly specific, ensuring that glucose units are added to the non-reducing end of the glycogen molecule. It operates in conjunction with other enzymes to regulate glycogen synthesis efficiently. Key points include:
  • Glycogen synthase adds glucose units from UDP-glucose to glycogen.
  • It is specific to the non-reducing ends of glycogen.
Glucose Donor
In the context of glycogen biosynthesis, a glucose donor is a molecule that provides glucose units to be added to glycogen. UDP-glucose is an excellent example of such a donor. It supplies the glucose that glycogen synthase uses to extend glycogen chains. This donation process is fundamental for maintaining energy reserves in cells. Highlights include:
  • UDP-glucose is the key glucose donor in glycogen biosynthesis.
  • It ensures a consistent supply of glucose for glycogen formation.
Uridine Diphosphate Glucose
Uridine diphosphate glucose (UDPG) has a pivotal role in the metabolic pathway of glycogen synthesis. It is formed from glucose-1-phosphate and UTP (uridine triphosphate) through the action of the enzyme UDP-glucose pyrophosphorylase. Once formed, UDPG donates glucose to the growing glycogen chain in a reaction catalyzed by glycogen synthase. After the glucose transfer, UDP (uridine diphosphate) is released as a byproduct. Key points to remember:
  • UDPG is created from glucose-1-phosphate and UTP.
  • It donates glucose to glycogen chains, facilitating energy storage.
  • UDP is released as a byproduct after glucose transfer.

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