Transcript H ions

Electron Transport System
As mentioned, electron transport system (ETS) takes place in the inner
membrane or cristae of the mitochondrion where a series of
Cytochromes and Coenzymes act as carrier molecules and transfer
electrons.They accept high-energy electrons (NADH,FADH formed in
Krebs cycle), then pass these electrons to the next molecule in the
system. Electrons lose energy as they pass down the ETS. Some of
energy is used to pump protons (H ions) into the outer compartment of
mitochondrion.
Each NADH molecule is highly energetic, which accounts for the
transfer of 6 protons (3ATP) into the outer compartment of
mitochondrion.FAD transfers 4 protons (2ATP).
Electrons pass from NAD to FAD to the Cytochromes and Coenzymes,
some of energy is capable of driving the formation of ATP from ADP
and inorganic phosphate. This ATP production is called oxidative
phosphorylation. The final acceptor of electrons is an oxygen atom.
The electron-oxygen combination then reacts with two hydrogen ions to
form water molecule.
Oxidative phosphorylation occurs in mitochondria by what is called
chemiosmosis mechanism (H ions "protons" will diffuse from an area
of high proton concentration to an area of low concentration.
ATP from Respirationِ
1-From Glycolysis
The reaction from Glucose to Fructose -1,6 diphosphate requires 2 ATP
Glucose + 2 ATP
Fructose -1,6 diphosphate +2 ADP
Then Fructose -1,6 diphosphate converts to pyruvic produces 4 ATP
2molecules from each Triose sugar acid that
1,3 diphosphoglyceric acid + ADP
3-phosphglyceric acid+ ATP
Phosphoenolpyruvic acid + ADP
pyruvic acid + ATP
i.e Glucose is broken down to 2 molecules of Pyruvic acid
+ net (2ATP) + 2 pairs of H ions
4 H ions produced will go subsequently through oxidative
phosphorylation to produce 3 ATP per unit
So, 4H= 2 pairs
2X 3ATP= 6 ATP
Total ATP= 2 +6= 8ATP
2- In initial step, the formation of Acetyle Co A:
Coversion of Acetyle Co A from Pyruvic acid produces 2
pairs of H ions
2NADH2, these H ions will go through oxidative
phosphorylation to produce 3 ATP per each pair of H ions
i.e 2 X 3ATP= 6ATP
3- From Krebs Cycle
Isocitric
Oxalosuccinic acid
α- ketogltaric acid
Succinic
Malic
NADH+ H+
succinyle CoA NADH + H +
Fumaric FADH + H+
Oxaloacetic
3ATP
NADH+ H+
2ATP
3ATP
Plus 1 ATP resulted from GTP formation during the conversion of
Succinic CoA to Succinic acid
Overall ATP from krebs = 12X2= 24ATP
3ATP
The oxidation of glucose to carbon dioxide plus water
yields 38 ATP
Glycolysis
8 ATP
Acetyle CoA
6 ATP
Krebs
Total
24 ATP
38 ATP
Substances that cells need can be taken up from their surrounding either
by passive or by active transport
Passive transport:
Moving molecules across the cell membrane, does not need energy
Types:
1-Simple diffusion: The movement of molecules from an area of high
concentration to an area of low concentration. Water, oxygen, carbon
dioxide, ethanol and urea are examples of molecules that readily cross cell
membranes by simple diffusion. They pass either directly through the lipid
bilayer or through pores created by certain integral membrane proteins. The
relative rate of diffusion is roughly proportional to the concentration
gradient across the membrane. For example, oxygen concentrations are
always higher outside than inside the cell and oxygen therefore diffuses
down its concentration gradient into the cell; the opposite is true for
carbon dioxide. There are several factors affecting this movement
through a membrane:
a-Permeability of the membrane
b- The concentration gradient.
2- Facilitated Diffusion:
Carrier Proteins and Ion Channels Glucose, sodium ions and chloride ions are just a few
examples of molecules and ions that must efficiently get across the plasma membrane but
to which the lipid bilayer of the membrane is impermeable. Their transport must therefore
be "facilitated" by proteins that embedded within the cell membrane and provide an
alternative route. Facilitated diffusion does not require expenditure of metabolic energy
and transport is again down an electrochemical gradient.
3-Osmosis:
Is another kind of passive transport. It is a special case of diffusion by
which cells obtain water. The movement of water will be from the area of
high water concentration to the area of low water concentration.
Hypertonic Solutions:
contain a high concentration of solute relative to another solution (e.g.
the cell's cytoplasm). When a cell is placed in a hypertonic solution, the
water diffuses out of the cell, causing the cell to shrivel.
Hypotonic Solutions:
contain a low concentration of solute relative to another solution (e.g.
the cell's cytoplasm). When a cell is placed in a hypotonic solution, the
water diffuses into the cell, causing the cell to swell and possibly explode.
Active transport:
The extracellular concentration of nutrients such as sugar and
inorganic salts is often low. The cellular membrane are not very
permeable to these nutrients, which are hydrophilic, water soluble, and
hence do not dissolve in membrane lipids. Passive uptake, which does
not require energy, tends to be inadequate for a cell’s nutrient needs.
Cells through active up take (need energy) improve the nutrient up take
by bringing these nutrients from a dilute source and can accumulate
them inside the cell to concentration much higher than that outside. The
membrane contains carrier proteins having carrier sites, which are
similar to the active site of an enzyme ( ATPase) into which the
transported molecules or ions fits. The carrier is thought to change
shape within the membrane, moving bound molecule or ion to the other
side the cell and releasing it.