mitochondrial and chloroplast information

1. By ,
Dr. Huma Jawed
Ph.D, Pharmacology
Cell Organelles’ Functions
Mitochondria &
Chloroplast

2. Body Obtain Energy From Food
• Cells require constant supply of energy.
• Most important fuel molecules are sugars.
• Plants make their own sugars from CO2 (photosynthesis)
• Animals obtain sugars & other organic molecules that can
transform into sugars by eating plants & other organisms.
• In any case the process by which sugar are broken down to
generate energy is similar to both types

3. Harvesting of Energy: ATP & NADH:
• Harvest energy from the chemical bond & oxidized to CO2 &
water (cell respiration).
• When energy require, captured “high energy” as covalent
bonds hydrolyzed and produces energy such as ATP &
NADH (Nicotinamide adenine dinucleotide; coenzyme),
FADH2 (flavin adenine dinucleotide; redox cofactor;
(activated carrier).
• These carriers in turn serve as portable source of chemical
group & electron needed for biosynthesis.

4. Breakdown and utilization of sugar & Fat:
• If fuel molecules such as sugar oxidized to CO2 & water in a single
step, it cause releases of energy in the form of heat.
• Cell’s enzyme synthesis system maintain degradation step by step in
strictly controlled series.
• Animal Cell generate ATP by two ways.
1- Energetically favorable enzyme catalyzed reactions involve in
breakdown of food, they are directly couple to the energetically
unfavorable reaction ADP+ Pi  ATP
Food  ATP generation
2- Other activated carriers (oxidative phosphorylation), generate ATP in
mitochondria.
• Release energy save in the
form of ATP bonds other
activated carriers. & make
available to do useful work for
the cell.

5. Food molecules are breakdown in 3 stages:
• Proteins, fat & polysaccharides,
breakdown (catabolism) into smaller
molecules, cell use them either for
source of energy or as building block
for making organic molecules.
• Rough estimation that about 109
molecules of ATP are constantly
consume & replace in 1-2 min.
• Glycolysis extract energy from
splitting sugars.
• Glycolysis ATP (even without O2)
• 6 carbon atom Sugar 
2 x (3 carbon atom pyruvate) +
2 ATP & 2 NADH

6. Glycolysis produce both ATP & NADH

10. Formation of Acetyl CoA
• Organic molecules convert into Acetyl CoA
(another activated carrier).
1-Pyruvate Dehydrogenase Complex:
a)Pyruvate dehydrogenase
b)Dihydrolipoyl transacetylase
c) Dihydrolipoyl dehydrogenase
2-Fatty Acid Oxidation:

12. The Citric Acid Cycle Generate NADH (oxidation of
Acetyl CoA to CO2)
• Citric acid cycle also called Tricarboxylic acid cycle (TCA) or Krebs cycle
• Almost (2/3) carbon oxidation occur in citric acid cycle (major end product ATP & NADH)
• NADH are passed to ETC in the inner mitochondrial membrane.
• TCA itself not use O2 but require to proceed as ETC essentially require O2

14. Electron Transport Chain (ETC): synthesis of
majority ATP
Final stage of food breakdown is oxidative phosphorylation

15. Mitochondria: Inner, Outer Membrane
& Inter Membrane Spaces
• Outer membrane contain many transport protein making
“porins” or aqueous channel through lipid bilayer
• Inner membrane is impermeable, only those small molecules
crosses that have transport carrier protein for them. Like
pyruvate, fatty acid
• Inner membrane is the site of oxidative phosphorylation & in
contain transporter proteins, proteins of ETC, the proton pump,
& ATP synthase,
• Inner membrane is highly convoluted forming a series of
infoldings (Cristae) , in cardiac muscle cells’ mitochondria these
cristae infolding are much more than mitochondria of liver cells.

16. Proton Pumped across Inner Membrane by
Proteins in ETC
• ETC or respiratory chain carries oxidative
phosphorylation, present in number of copies.
• Each contain over 40 protein grouped into 3 large
respiratory Enzyme Complexes
• These complexes each contain multiple individual
proteins including transmembrane protein that anchor
the complex family in the inner mitochondrial
membrane.
• Three Main Respiratory Enzyme Complexes:
1- NADH dehydrogenase complex.
2- Cytochrome c reductase complex.
3- Cytochrome c oxidative complexes. `

17. Respiratory Enzyme Complexes
• Each complex contains metal ions & other chemical group
these respiratory complexes accompanied by the pumping
of protons. Thus each complex can be thought as a proton
pump.
• Pumping of proton generate H+ gradient i.e. pH gradient &
voltage gradient (membrane potential)

18. Mitochondria: Energy by Membrane Based
Mechanism
• Two linked reactions
1- electrochemical proton gradient
2- generate ATP by using this proton gradient
• In eukaryotes, mitochondria present in large
numbers produce ATP ( about 1000-2000 in
liver cells)
• Mitochondrial dysfunction causes various
pathologies including myoclonic epilepsy etc.
• Muscles and nerve cell are very sensitive to
these changes as they need much ATP to
function normally.

19. Rapid Conversion of ADP to ATP in mitochondria maintain
as high ATP/ADP ratio in cell

21. Chloroplast & Photosynthesis
• All organic material in cell produced by photosynthesis.
• Photosynthesis is series of light driven reactions that
synthesize organic molecule from CO2.
• Plant & algae & photosynthetic bacteria use electron from
water & energy from sunlight to convert atmospheric CO2
into organic compounds
• Water molecules splits & release O2 gas in atmosphere.
(help in oxidative phosphorylation in all types of cells).
• In plants, photosynthesis is carried in a specialized
intracellular organelle –chloroplast, which contain light
capturing pigment such as green colour pigment-
chlorophyll.
• Photosynthesis occur in day light hours
CO2  Sugar (carbon fixation)

22. Chloroplast Resembles Mitochondria
but have Thylakoid
• Chloroplast are larger than mitochondria.
• It has highly permeable outer membrane & much
less permeable inner membrane in which various
trans-protein embedded.
• In the inner membrane of the chloroplast does not
have photosynthesis machinery. Instead, light
capturing systems, ETC & ATP synthase are all
present in Thylakoid membrane.
• Matrix is
called Stroma.

23. Photosynthesis generate & Consume
ATP & NADPH
Stage 1: Similar oxidative phosphorylation
• Thylakoid membrane harness the energy of
electron transport to proton pump into
thylakoid space. This gradient help in ATP
synthesis. (also called ‘”Light reaction”)
• High energy is denoted to ETC from
chlorophyll.
• 2nd difference: electron not transfer to O2 but
to NADP+ to form NADPH (Nicotinamide
adenine dinucleotide phosphate.)
Stage 2:
• ATP & NADPH use to drive the synthesis of
sugar from CO2.
• These carbon fixation reactions occur in
absence of light so called “dark reaction”.
• It begin in stroma, lead to form 3 carbon
sugar “Glyceraldehyde 3-phosphate (G3P)”.
• This sugar can transport to cytosol, where use
to produce sucrose and other organic
molecules in the leaves.

24. Chlorophyll molecules absorb the energy of sunlight
• Visible light is a form electromagnetic
radiation of many wavelength (400-700nm).
• Most chlorophyll best absorb light in the blue
& red wavelength & that absorb least green
colour lights that is why look green to us.
• Chlorophyll harness energy harvest from
sunlight.
• When light strike the chlorophyll, the
electron excited & perturbed. This high
energy is unstable.
• Chlorophyll are associated with specific set of
photosynthesis protein in the thylakoid
membrane.

25. Excited Chlorophyll Transfer Energy
into Reaction Center
Antenna

27. Carbon Fixation: Calvin Cycle
• ATP & NADPH can not transport into cytosol.
• Therefore, convert to sugar molecules.
• This process is called “Carbon Fixation”.
• In this process, CO2 is attached to one of the sugar
Ribulose 1,5-bisphosphate
(5 carbon molecule)
• This fixation lead to the formation of
2 molecules of 3 carbon sugar
“Glyceraldehyde 3-phosphate”, by
Using enzyme Ribulose bisphosphate
Carbooxylase (Rubisco).
Carbon Fixation Cycle:
• A part of regeneration of
Ribulose 1,5-bisphosphate.
• many ATP & NADPH consume
• G3P, final product provide the
starting material for other
Sugars & organic molecules.

28. Sugar Can be store As Starch & Fats/consume for
ATP Generation:
• G3P generated by carbon fixation in the stroma used in
number of ways depending upon need.
• Most of the sugar converted to starch.
• Starch is store as a large
granule in chloroplast
• Some sugar converted
into fats within the stroma
& store as fat droplets.
• At night, these starch and
fat breakdown into sugar
& Fatty acid
(respectively), which are
then exported to cytosol
for metabolic need.

29. • Then it coupled to oxidative
phosphorylation.
Continue……
 Sugar (G3P) can be enter into glycolytic cycle.
 Some G3P can be converted
into another most important
sugar , sucrose (disaccharide)
 It transported between plants cells,
like, glucose that transported in
blood, it is exported from the leaves
via vascular bundles to provide
carbohydrate to the rest of the
plant.