Download carbohydrate metabolism

Welcome to class of
Metabolism
Dr. Meera Kaur
What is metabolism?
• Metabolism is all the chemical reactions done by living organism.
Virtually all chemical reactions are catalyzed by enzymes.
• Catabolism is a part of metabolism– the breakdown of substances
by an organism. Many important catabolic reactions occur in the
mitochondria.
• Anabolism is another part of metabolism– the synthesis of
molecules used to build molecules for cell growth and multiplication.
Nutrients are also converted to their storage forms by anabolic
processes. Many anabolic reactions occur in cytoplasm.
• Cells usually employ different chemical reactions for the breakdown
and synthesis of the same molecule.
Carbohydrate metabolism
• Carbohydrate occupies central drama of the cell.
•
Supporting roles are played by fats and amino acids.
• The star of carbohydrate metabolism is glucose.
In carbohydrate metabolism, we will see: how is
glucose broken down inside the cell to produce
energy; how is it stored; how is the level of glucose
regulated in the blood; and, how defects in regulation
of blood glucose lead to diabetes.
Catabolism of glucose
• The paths that cells use to oxidize glucose completely to carbon
dioxide involve many individual chemical reactions. These reactions
occur in three different stages. These are:
- initial break down of glucose to pyruvate in glycolysis,
- further degradation of pyruvate to acetyl coenzyme A, and
- finally complete oxidation of acetyl coenzyme A to water and
carbon dioxide in the citric acid cycle.
• Glycolysis (Greek: glyco,sugar; lysis, splitting) is the sequence of
chemical reactions by which glucose, a six-carbon sugar is cleaved to
two molecules of pyruvate, a three-carbon acid. Also known as
glycolytic pathway or the Embden-Meyerhof pathway after the name
of two German biochemist Gustav Embden and Otto Meyerhof, who
proposed it in the latter part of the 19th century.
The reactions of glycolysis
The enzymes
that catalyze
the steps of
glycolysis are
found in the
cytoplasm of
the cells.
Hence,
glycolysis
occur in
cytoplasm.
.
Enolase
.
Formation of Acetyl coenzyme A
Two carbons of pyruvate are incorporated into acetyl
coenzyme A
• When an aerobic cell is operating with a good supply of oxygen,
pyruvate molecule flows into the mitochondria. Two of the
carbons of each pyruvate ion end up as acetyl CoA, and one
molecule of NAD+ is reduced to NADH. Carbon dioxide is
formed as waste product.
• A multi-enzyme complex is responsible for the formation of acetyl
CoA from pyruvate.
Gluconeogenesis
• The pathway by which lactate is converted to glucose
is called gluconeogenesis (Greek: gluco, glucose;
neo, new; genesis,creation). Gluconeogenesis is the
process for synthesis of glucose from noncarbohydrate source (lactate). This is an example of
anabolic or synthetic pathway.
Glycogen synthesis
Glycogen synthesis