This document discusses the biosynthesis of carbohydrates through gluconeogenesis and photosynthesis. It explains that gluconeogenesis allows animals to synthesize glucose from non-carbohydrate precursors like lactate, pyruvate, and amino acids in the liver and kidneys. Photosynthesis allows plants to synthesize glucose from carbon dioxide and water using light energy. Key steps in both processes are outlined, and it is noted that gluconeogenesis, while using similar pathways to glycolysis, requires bypassing some irreversible steps and is thus more energetically costly than glycolysis.

1. Biosynthesis of
Carbohydrates
Presented by:
Shashank Tripathi
M.Sc. (Environmetal Biotechnology)
Institute of environment & Sustainalble Development
Banaras Hindu University
Varanasi-221005

2. What is Biosynthesis?
The multistep, enzyme-catalysed process, where
substrates are converted into more complex
products in Living Beings.
The products which are produced as a result of
biosynthesis are necessary for cellular and
metabolic processes deemed essential for survival of
livings.

3. Topics to be cover:
 Gluconeogenesis
 Photosynthetic Carbohydrate Synthesis
 Biosynthesis of Glycogen, Starch and Sucrose

4. Biosynthesis of Glucose
 In animals Biosynthesis of Glucose take place through
Gluconeogenesis.
 In plants Biosynthesis of Glucose take place through
Photosynthesis.

5. Biosynthesis of Glucose in
Animals:
• The Gluconeogenesis

6. Importance of Gluconeogenesis:
It is universal pathway found in all animals, plants,
Fungi and microorganisms for synthesis of glucose.
To maintain our blood glucose levels (prevent
hypoglycemia)
In vertebrates Gluconeogenesis in Liver and Kidney
provides glucose for use y the brain, muscles and
erythrocytes.

7. Process by which glucose is made from non-
carbohydrates:
 Lactate
 Pyruvate
Amino acids (particularly Ala)
Glycerol (from triacylglyceride hydrolysis) enters
as dihydroxyacetone phosphate
Acetate

8. Brain is top priority!
1. Needs large amounts of energy
2. 2. Cannot store energy (very little glycogen storage)
3. 3. Not sensitive to insulin regulation
4. 4. Must have glucose for energy! Will not adapt to using
ketone bodies (fat) for energy until dire conditions arise
(weeks of fasting)

9. • The relevant features of the
pathway of gluconeogenesis
• Synthesis of glucose from
three and four carbon
precursors is essentially a
reversal of glycolysis.

10.  Net reaction:
2 pyruvate+2NADH+2ATP+2GTP+6 H2O + 2 H+
Glucose + 2 NAD+ + 4 ADP + 2 GDP + 6 Pi

11. Gluconeogenesis is not
simply reversal of
Glycolysis:
• Glycolysis is an ancient metabolic
pathway that is common to all forms
of cellular life, and can be performed
by all cells to obtain energy (a net of 2
ATP per glucose). In contrast,
gluconeogenesis is much more
specific; in humans, it is primarily
carried out in liver cells, as well as to
some extent in the adrenal cortex. It
also has a much more specific goal: to
produce glucose to be secreted into
the bloodstream when blood glucose
levels are low.
• The biochemical details of
gluconeogenesis are different from
those of glycolysis. The reason usually
given for this is that gluconeogenesis
needs to bypass the energetically
favorable/irreversible steps of
glycolysis.

12. Gluconeogenesis from Lactate:

13. Gluconeogenesis from Pyruvic Acid:

14. Gluconeogenesis is Energetically Costly:

15. Biosynthesis of Glucose in
Plants:
• The Photosynthesis

16. The Photosynthesis:
• Photosynthesis, the process by which
green plants and certain other
organisms transform light energy into
chemical energy.
During photosynthesis in green plants,
light energy is captured and used to
convert water, carbon dioxide, and
minerals into oxygen and energy-rich
organic compounds.
6CO2 + 6H2O ------> C6H12O6 + 6O2
Sunlight energy
Where: CO2 = carbon dioxide
H2O = water
Light energy is required
C6H12O6 = glucose
O2 = oxygen

17. Comparative Pathway
from PEP to Glucose-6-
phosphate in Animals
and Plants :