Pentose Phosphate Pathway and Fructose Metabolism

Pentose Phosphate Pathway and Fructose Metabolism


Oxidative reactions leading from glucose 6phosphate to ribose 5-phosphate Non-oxidative reactions leading to the formation of intermediates of glycolysis Glycogen structure and function Glycogen synthesis and breakdown Suggested reading: Lippincotts Biochemistry, 6th edition, pages 125-135, 145-155, glycogen

glucose glucose 6-phosphate glycolysis pentose

phosphate pathway FUNCTIONS OF THE PENTOSE PHOSPHATE PATHWAY Provide reduced NADP for synthetic reactions, e.g. fatty acid synthesis and reduction of glutathione

Provide pentose phosphate for nucleic acid synthesis GLYCOGEN FUNCTION AND LOCATION Glycogen serves as a storage form of carbohydrate In a well fed individual the concentration per gram tissue is highest in liver but the glycogen in liver can be depleted by a 24 hour fast.

Glycogen is less readily depleted in muscle and there is more total glycogen in muscle than in any other tissue of the body. Brain has a very low glycogen concentration. The brain is largely dependent upon circulating glucose for the carbohydrate that it requires. GLYCOGEN STRUCTURE Glycogen is a polysaccharide in which

glucosyl residues are joined by glycosidic links. The major linkage between glucosyl residues are 1-> 4 with branch points in the chain that are 1-> 6 and occur at an average spacing of 8 to 12 1 -> 4 links. UDP

glycogen UDP-glucose phosphate glucose 1-phosphate glucose

glucose 6-phosphate glycolysis pentose phosphate pathway

GLYCOGEN SYNTHESIS Glucose 6-phosphate is converted to glucose 1-phosphate in a reversible reaction catalyzed by phosphoglucomutase Glucose 1-phosphate + UTP -> UDP-glucose + pyrophosphate catalyzed by UDP-glucose pyrophosphorylase Glycogen synthase catalyzes the transfer of

glucose from UDP-glucose to glycogen with the formation of an alpha 1-> 4 link. Branch points are formed by glycogen branching enzyme (amylo 1-4 -> 1-6 transglucosylase). GLYCOGEN BREAKDOWN Alpha 1-> 4 links in glycogen are broken by a phosphorolytic cleavage that requires

inorganic phosphate and produces glucose 1phosphate. The reaction is catalyzed by the enzyme glycogen phosphorylase. Branch points are cleaved by a hydrolytic reaction that produces free glucose and is catalyzed by glycogen debranching enzyme. This enzyme also has a transferase activity that can transfer a small oligosaccharide near a branch point to a longer alpha 1-> 4 linked chain.

REGULATION OF GLYCOGEN METABOLISM Glycogen metabolism is regulated by the activities of glycogen synthase and glycogen phosphorylase. Phosphorylation by protein kinases activates glycogen phosphorylase and inactivates glycogen synthase. The phosphorylation is reversed by phosphoprotein phosphatase activity.

Glucagon and epinephrine increase glycogen breakdown by activating adenylate cyclase. This produces 35-cyclic AMP which activates protein kinase A. Downloaded from: StudentConsult (on 4 December 2011 07:14 PM) 2005 Elsevier LECTURE OBJECTIVES

After studying this lecture material you should be able to Describe the functions of the pentose phosphate pathway Distinguish the oxidative and non-oxidative parts of the pentose phosphate pathway Describe glycogen structure and function Distinguish the reactions in glycogen synthesis and breakdown

Describe how regulation of glycogen metabolism involves the phosphorylation status of glycogen synthase and glycogen phosphorylase

Recently Viewed Presentations

  • 5.1 Writing Linear Equations in Slope-Intercept Form 5.2 ...

    5.1 Writing Linear Equations in Slope-Intercept Form 5.2 ...

    Write the equation of the line. y= mx + b y = (-2/3)x + 2 Step 1: First find the y-intercept. Substitute the slope m and the coordinates of the given point (x, y) into the slope-intercept form, y =...
  • Haz Mat Awareness 2012 - 2013 - Google Sites

    Haz Mat Awareness 2012 - 2013 - Google Sites

    The front white pages: Response information instead of instructions to use. Added Information. Inside front cover is the shipping papers document. Page 1 is a brief "How To" for anyone who has never used the ERG, not a detailed instruction...
  • Unit 3 - Home - Thomas County Schools

    Unit 3 - Home - Thomas County Schools

    John Brown Essay. Paragraph 3. Harper's Ferry incident. Raid the arsenal at Harper's Ferry. Steal guns and give them to slaves. John Brown and three sons died. Two sons killed during the fighting. Third son hung for treason. John Brown...
  • IHSAA Diving Judges Clinic 2008

    IHSAA Diving Judges Clinic 2008

    Biased judging is an offence against the concept of sportsmanship and fair competition. ... The dive should be performed at an appropriate distance from the board. The Flight Stage 1 - The Purpose. To start the execution of the dive.
  • Pesticides: The Problems and The Solutions

    Pesticides: The Problems and The Solutions

    Based on common sense safety rules Uses alternative measures to enact pest-control Mechanical trapping devices Pesticides and Children Children have still-developing internal organs Children eat and drink more then adults relative to their weight Childhood behaviors facilitate the consumption of...
  • BLR's Safety Training Presentations

    BLR's Safety Training Presentations

    Electrical (Fire): Use of electrical power that results in electrical overheating or arcing to the point of combustion or ignition of flammables, or electrical component damage Common Hazards and Descriptions Electrical (Static/ESD): The moving or rubbing of wool, nylon, other...
  • Are we at Northside united?

    Are we at Northside united?

    What we mean by "Diversity" in the Church. NOT FALSE DOCTRINES - The Lord God does not believe in unity in false doctrine. There is no such thing as a united church with many doctrines.
  • Diseño Curricular

    Diseño Curricular

    Modelos curriculares. M. Simbólico. Relacionado de acuerdo a la teoría y a la practica enfocado a la resolución de problemas curriculares. Se debe elaborar de acuerdo al contexto de los alumnos, sus medios y lo debe elaborar un especialista