Carbohydrates metabolism research

3. During digestion, carbohydrates are broken
down into simple sugars that can
transported across the intestinal wall into
the cardiovascular system to transport
throughout the body. Carbohydrate
digestion begins in the mouth with the
action of salivary amylase on starches and

4. Glycogen metabolism:
Glycogen: formed from branched D-glucose units linked by 1,4 and 1 ,6 glycosidic bonds. It is
the major storage form of glucose in liver and muscle. It found in the cytosol in many cell
types.
The glycogen metabolism consists of two processes:
1) Glycogen synthesis, which called glycogenesis
2) Glycogen degradation, which called glycogenolysis

5. Glycogen Function:
• The synthesis and
breakdown of
glycogen regulated
to provide the
energy requirements
of the muscle cell.
In muscle
• The synthesis and
breakdown of
glycogen regulated
to maintain blood
glucose levels.
In liver

6. Glycolysis:

8. Gluconeogenesis
is the synthesis of new glucose molecules from noncarbohydrate
precursors, which include pyruvate, lactate, glycerol, or the amino acids
alanine or glutamine. This process occurs primarily in the liver during
periods of low glucose, that is, under conditions of fasting, starvation, and
low carbohydrate diets.

10. Metabolism of Other Important Sugars:
Several sugars other than glucose are important in vertebrates.
Such as fructose, galactose, and mannose .They are also energy
sources. The metabolism of fructose, an important component of
the human diet, discussed below:

11. Fructose Metabolism:
Dietary sources of fructose include fruit, honey, and sucrose. Fructose, second source
of carbohydrate in the human diet, can enter the glycolytic pathway by two ways:
In the liver:

12. In Muscle And Adipose Tissue

14. Krebs cycle
A series of enzymatic reactions in aerobic organisms
involving oxidative metabolism of acetyl units and
producing high-energy phosphate compounds, which
serve as the main source of cellular energy.

15. Steps Of The Citric Acid Cycle:
Step 1. acetyl CoA joins with oxaloacetate,
releasing the CoA group and forming citrate (citric
acid).
Step 2. citrate is converted into its isomer, iso
citrate. This is actually a two-step process,
involving first the removal and then the addition of
a water molecule.
Step 3. isocitrate is oxidized and releases a
molecule of carbon dioxide α-ketoglutarate. During
this step, NAD+ is reduced to form NADH. The
enzyme catalyzing this step, isocitrate
dehydrogenase, is important in regulating the
speed of the citric acid cycle.

16. Step 4. The fourth step is similar to the third. In this
case, it’s α-ketoglutarate that’s oxidized and releasing a
molecule of carbon dioxide in the process. Forming the
unstable compound succinyl CoA. The enzyme
catalyzing this step, α-ketoglutarate dehydrogenase, is
also important in regulation of the citric acid cycle.
Step 5. CoA of succinyl CoA is replaced by a
phosphate group, which is then transferred to ADP to
make ATP. The molecule produced in this step is called
succinate.

17. Step 6. succinate is oxidized, forming another
molecule called fumarate. In this reaction, two
hydrogen atoms—with their electrons—are
transferred to FAD producing FADH2.
Step 7. water is added to the fumarate molecule,
converting it into malate molecule.
Step 8. oxaloacetate is regenerated by oxidation
of malate. Another molecule of NAD+ is reduced
to NADH in the process.

18. The electron transport chain (ETC)
The electron transport chain (ETC) uses the NADH and
FADH2 produced by the Krebs cycle to generate ATP. It is occurs
in the inner mitochondrial membrane.
The electron transport chain consists of:
- Series of four enzyme complexes (Complex I – Complex IV).
- Two coenzymes (Coenzyme Q and Cytochrome c), which act as
electron carriers and proton pumps used to transfer H+ ions into
the space between the inner and outer mitochondrial membranes.

19. The components of the (ETC):
1) NADH
2) Flavoproteins
3) Coenzyme Q (CoQ)
4) Cytochromes
5) Iron-Sulfur Proteins
6) Copper Proteins

20. Complexes of electron
transport chain
Complex I (NADH dehydrogenase)
 The first complex contains iron-sulfurs center and FMN.
 accepts electrons from NADH to regenerate NAD.
 pumps protons each pair of electrons results in the movement of about 4 H+ from
the matrix to the inter membrane space.
 donates electrons to Coenzyme Q

21. Complex II (Succinate Dehydrogenase)
Succinate dehydrogenase is one of the enzymes in the TCA cycle. It is the only
TCA cycle enzyme fixed in the mitochondrial inner membrane.
Complex III (Coenzyme Q-dependent cytochrome c reductase)
 Complex III accepts electrons from Coenzyme Q.
 it is a proton pump.
 It contains several heme prosthetic groups.
 The electrons that Complex III receives are donated one at a time to a soluble heme
containing electron carrier protein called cytochrome c. it is located in the inter
membrane space.

22. Complex IV (Cytochrome c oxidase)
 Cytochrome c oxidase accepts electrons from cytochrome c.
 Complex IV is the terminal part of the electron chain and transfers electrons directly
to oxygen.
 It is a proton pump.

23. Oxidative stress:
Oxidative stress occurs when there is an imbalance in the
cells due to either an increase in free radicals or a decrease in
antioxidants.
Oxidative stress is involved in the pathogenesis of diseases,
including atherosclerosis, hypertension, diabetes mellitus,
and malignancies.
Oxidative stress is harmful because oxygen free radicals
attack biological molecules such as lipids, proteins, and
DNA.

25. Glucose-6-Phosphate dehydrogenase deficiency:
It is a condition in which red blood cells break down when the body is
exposed to certain drugs (such as Antimalarial drugs, Aspirin,
Nonsteroidal anti-inflammatory drugs), certain foods (such as fava beans)
or the stress of infection.
It occurs when a person does not have enough of an enzyme called glucose-
6-phosphate dehydrogenase. This enzyme helps red blood cells work
correctly. Too little G6PD leads to the destruction of red blood cells. This
process is called hemolysis.