Define what is respiration
Differentiate aerobic from anaerobic respiration
Explain the 4 main stages of aerobic respiration
Explain the process of fermentation
Define what is respiration
Differentiate aerobic from anaerobic respiration
Explain the 4 main stages of aerobic respiration
Explain the process of fermentation
Photosynthesis and respiration are reactions that complement each other in the environment. They are in reality the same reactions but occurring in reverse. While in photosynthesis carbon dioxide and water yield glucose andoxygen, through the respiration process glucose and oxygen yield carbon dioxide and water.
They work well since living organisms supply plants with carbon dioxide which undergoes photosynthesis and produces glucose and these plants and bacteriagive out oxygen which all living organisms need for respiration.
Photosynthesis is a process that converts carbon dioxide into organic compounds in presence of sunlight. Respiration is the set of metabolic reactions that take in cells of living organisms that convert nutrients like sugar into ATP (adenosine tri phosphate) and waste products.
Processes in photosynthesis are divided on basis of requirement of sunlight while respiration processes are divided on basis of requirement of oxygen. Hence in photosynthesis you have the light dependent reactions and the dark reactions while inrespiration there is aerobic respiration and anaerobic respiration.
In photosynthesis light dependent reactions, ultra violet light strikes chlorophyll pigments which excites electrons leading to separation of oxygen molecules from carbon dioxide. In the dark reactions, carbon molecules now independent of oxygen are converted into carbohydrates and stored in plant cells as energy and food source. In aerobic cellular respiration oxygen is utilized to convert organic compounds into energy and in anaerobic respiration converts organic compounds into energy without using oxygen.
Cellular respiration ppt, describes generalities about energy and ATP, and the three stages of cellular respiration: Gylolisis, Krebs Cylce and Electron transport chain.
This is brief discussion on the Respiration and Types of respiration.
total process of glycolysis, citric acid cycle. This will help you to understand the respiration complete process of respiration
Cellular Respiration CR Chapter 8 And 9 version 2.0MrJewett
Energy of Reactions, Cellular Respiration (Gylcolysis, Krebs Cycle, based on Campbell & Reece Biology Chapters 8 & 9
Oxidative Phosphorylation slides added (earlier ones corrected), and Fermentation slides also
The prime cause and treatment of cancer somayeh zaminpira - sorush niknamianbanafsheh61
This meta-analysis research has gone through more than 200 studies from 1934 to 2016 to find the differences and similarities in cancer cells, mostly the cause. The most important difference between normal cells and cancer cells is how they respire. Normal cells use the sophisticated process of respiration to efficiently turn any kind of nutrient that is fat, carbohydrate or protein into high amounts of energy in the form of ATP. This process requires oxygen and breaks food down completely into harmless carbon dioxide and water. Cancer cells use a primitive process of fermentation to inefficiently turn either glucose from carbohydrates or the amino acid glutamine from protein into small quantities of energy in the form of ATP. This process does not require oxygen, and only partially breaks down food molecules into lactic acid and ammonia, which are toxic waste products. The most important result is that fatty acids or better told fats cannot be fermented by cells. This research mentions the role of ROS and inflammation in causing mitochondrial damage and answers the most important questions behind cancer cause and mentions some beneficial methods in preventing and treatment of cancer.
Photosynthesis and respiration are reactions that complement each other in the environment. They are in reality the same reactions but occurring in reverse. While in photosynthesis carbon dioxide and water yield glucose andoxygen, through the respiration process glucose and oxygen yield carbon dioxide and water.
They work well since living organisms supply plants with carbon dioxide which undergoes photosynthesis and produces glucose and these plants and bacteriagive out oxygen which all living organisms need for respiration.
Photosynthesis is a process that converts carbon dioxide into organic compounds in presence of sunlight. Respiration is the set of metabolic reactions that take in cells of living organisms that convert nutrients like sugar into ATP (adenosine tri phosphate) and waste products.
Processes in photosynthesis are divided on basis of requirement of sunlight while respiration processes are divided on basis of requirement of oxygen. Hence in photosynthesis you have the light dependent reactions and the dark reactions while inrespiration there is aerobic respiration and anaerobic respiration.
In photosynthesis light dependent reactions, ultra violet light strikes chlorophyll pigments which excites electrons leading to separation of oxygen molecules from carbon dioxide. In the dark reactions, carbon molecules now independent of oxygen are converted into carbohydrates and stored in plant cells as energy and food source. In aerobic cellular respiration oxygen is utilized to convert organic compounds into energy and in anaerobic respiration converts organic compounds into energy without using oxygen.
Cellular respiration ppt, describes generalities about energy and ATP, and the three stages of cellular respiration: Gylolisis, Krebs Cylce and Electron transport chain.
This is brief discussion on the Respiration and Types of respiration.
total process of glycolysis, citric acid cycle. This will help you to understand the respiration complete process of respiration
Cellular Respiration CR Chapter 8 And 9 version 2.0MrJewett
Energy of Reactions, Cellular Respiration (Gylcolysis, Krebs Cycle, based on Campbell & Reece Biology Chapters 8 & 9
Oxidative Phosphorylation slides added (earlier ones corrected), and Fermentation slides also
The prime cause and treatment of cancer somayeh zaminpira - sorush niknamianbanafsheh61
This meta-analysis research has gone through more than 200 studies from 1934 to 2016 to find the differences and similarities in cancer cells, mostly the cause. The most important difference between normal cells and cancer cells is how they respire. Normal cells use the sophisticated process of respiration to efficiently turn any kind of nutrient that is fat, carbohydrate or protein into high amounts of energy in the form of ATP. This process requires oxygen and breaks food down completely into harmless carbon dioxide and water. Cancer cells use a primitive process of fermentation to inefficiently turn either glucose from carbohydrates or the amino acid glutamine from protein into small quantities of energy in the form of ATP. This process does not require oxygen, and only partially breaks down food molecules into lactic acid and ammonia, which are toxic waste products. The most important result is that fatty acids or better told fats cannot be fermented by cells. This research mentions the role of ROS and inflammation in causing mitochondrial damage and answers the most important questions behind cancer cause and mentions some beneficial methods in preventing and treatment of cancer.
Cellular Energy Transfer (Glycolysis and Krebs Cycle) and ATPmuhammad aleem ijaz
This presentation is all about Cellular Energy Transfer with reference to Glycolysis and Kreb Cycle with all their stages involved.
It also includes ATP production in the body, its importance, structure.
Also contains a comparison of energy production in Krebs and Glycolysis cycle.
Introducing the Evolutionary Cell Memory (ECM) Hypothesis banafsheh61
This research study has gone through more than 34 sample tumors in Violet Cancer Institute (VCI) to find the cancer
cells’ resemblances to the primitive eukaryote cells in 3.5 billion years ago before the entrance of the mitochondria
into the eukaryote cells as endosymbionts. Nearly all the samples showed that the mitochondria inside the cells were
not working properly. Their cristae were damaged or the mitochondria did not work or better said “shut down”
inside the cancer cells. This study introduces a new hypothesis called the Evolutionary Cell Memory (ECM) based on
the Lamarckian Evolutionary Hypothesis and the Evolutionary Metabolic Hypothesis of Cancer introduced by the
Somayeh Zaminpira and Sorush Niknamian in 2017.
Complete E material on Fundamentals of Biochemistry [2+1]; (32 Lectures)Pradipta Banerjee
Complete Study Material for UG and PG students (especially, useful for B.Sc. Agriculture; B.Sc. Biochemistry students) . Topics covered: Importance of Biochemistery, Buffer, pH, Carbohydrates, Amino acids, Nucleic Acids, Proteins, Lipids, Lipid Metabolism, Carbohydrate Metabolism
This is an up to date study material for UG & PG students. It describes about Crop-water relationship; absorption; transpiration; stomatal physiology; theories of water uptake; diffusion; osmosis; nutrient uptake mechanism
Intellectual Property Rights Notes for B.Sc. & M.Sc. StudentsPradipta Banerjee
GATT, WTO, WIPO, TRIPS, BERNE convention, Madrid Protocol, Budapest Treaty, Copyright, Trademark and its types, Service mark, GI, Industrial design, Integrated circuits
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
1. Theory
Introduction to crop physiology and its importance in Agriculture; Plant cell: an Overview; Diffusion and osmosis; Absorption of water,
transpiration and Stomatal Physiology; Mineral nutrition of Plants: Functions and deficiency symptoms of nutrients, nutrient uptake mechanisms;
Photosynthesis: Light and Dark reactions, C3, C4 and CAM plants; Respiration: Glycolysis, TCA cycle and electron transport chain; Fat
Metabolism: Fatty acid synthesis and Breakdown; Plant growth regulators: Physiological roles and agricultural uses, Physiological aspects of
growth and development of major crops: Growth analysis, Role of Physiological growth parameters in crop productivity.
Practical
Study of plant cells, structure and distribution of stomata, imbibitions, osmosis, plasmolysis, measurement of root pressure, rate of transpiration,
Separation of photosynthetic pigments through paper chromatography, Rate of transpiration, photosynthesis, respiration, tissue test for mineral
nutrients, estimation of relative water content, Measurement of photosynthetic CO2 assimilation by Infra Red Gas Analyser (IRGA).
References
1. Taiz, L. and zeiger,E. 2010. Plant Physiology 5th edition, Sinauer Associates, Sunderland, MA, USA. 2. Gardner, F.P., Pearce, R.B., and
Mitchell, R.L. 1985. Physiology of Crop Plants, Scientific Publishers, Jodhpur. 3. Noggle, G.R. and Fritz, G.J., 1983. Introductory Plant Physiology.
2nd Edition. Prentice Hall Publishers, New Jersey, USA
Fundamentals of Crop Physiology [ASPH1201]
Pradipta Banerjee, Ph.D.
Dept. of Biochemistry & Crop Physiology
CUTM, Paralakhemundi, Odisha
2. 1. What are Respiratory substrates
2. Aerobic Respiration (mitochondria)
3. Anaerobic respiration (cytosol)
4. Oxidation of carbohydrates in 3 phases: Glycolysis, TCA cycle, ETS or Terminal respiration
5. Why TCA cycle is link between carbohydrate and protein metabolism?
6. TCA is an amphibolic pathway. Explain why?
7. Oxidative and substrate level phosphorylation
8. Significance of Pentose Phosphate Pathway
9. What is Pasteur Effect?
10. What is Crabtree Effect?
11. What is Extinction Point?
12. What is Bioluminescence
13. What is Respiratory Quotient?
14. Factors affecting Respiration in plants
FIND OUT…
3. The minimum amount of oxygen, at which aerobic respiration takes place & anaerobic respiration become extinct
is called as extinction point.
The ratio of the volume of CO2 released to the volume of O2 taken in respiration is called RQ. Value of RQ
depends upon the type of respiratory substrate used & measured by Ganong's respirometer.
4. The Crabtree Effect (named after the English biochemist Herbert Grace Crabtree) occurs in metabolically
adapted cell lines that are grown in hypoxic/anaerobic conditions with high glucose.
These cells have a reduced need for oxidative phosphorylation by the TCA cycle and depend on glycolysis as
their major source of energy instead of mitochondria; therefore these cells also have a reduced susceptibility
to mitochondrial toxicants.
The addition of galactose circumvents the Crabtree Effect and increases the reliance of cells on
mitochondrial oxidative phosphorylation; these cells are more sensitive to mitochondrial toxicity.
Crabtree Effect
When the concentration of oxygen is lowered, respiration of mitochondria decreases, and aerobically
produced CO2 declines with an increase in fermentation, which is related to the low-oxygen consequences and
a rise in overall CO2 production causing glycolysis increase, known as the Pasteur effect
Pasteur Effect
5. Outline of Respiratory Metabolism
1. Glycolysis or EMP (Embden-Meyerhof-Parnas) Pathway or Hexose Diphosphate
Pathway
2. Pentose Phosphate Pathway
3. TCA Cycle
4. ETS
7. In animals, excess glucose is converted to its storage form, glycogen (plant – starch), by glycogenesis. When glucose
is needed as a source of energy or as a precursor molecule in biosynthetic processes, glycogen is degraded by
glycogenolysis. Glucose can be converted to ribose-5-phosphate (a component of nucleotides) and NADPH (a
powerful reducing agent) by means of the pentose phosphate pathway. Glucose is oxidized by glycolysis, an energy-
generating pathway that converts it to pyruvate. In the absence of oxygen, pyruvate is converted to lactate. When
oxygen is present, pyruvate is further degraded to form acetyl-CoA. Significant amounts of energy in the form of
ATP can be extracted from acetyl-CoA by the citric acid cycle and the electron transport system. Note that
carbohydrate metabolism is inextricably linked to the metabolism of other nutrients. For example, acetyl-CoA is
also generated from the breakdown of fatty acids and certain amino acids. When acetyl-CoA is present in excess, a
different pathway converts it into fatty acids.
General Outline of Carbohydrate metabolism
16. The first phase of the
pentose phosphate pathway
consists of two oxidations
that convert glucose 6-
phosphate to ribulose 5-
phosphate and reduce
NADP+ to NADPH. The
second phase comprises
non-oxidative steps that
convert pentose phosphates
to glucose 6-phosphate,
which begins the cycle
again.
Entry of glucose 6-
phosphate either into
glycolysis or into the
pentose phosphate pathway
is largely determined by the
relative concentrations of
NADP and NADPH.
PENTOSE PHOSPAHTE PATHWAY
17. General scheme of the pentose phosphate pathway. NADPH formed in the oxidative phase is used to reduce glutathione, GSSG and
to support reductive biosynthesis. The other product of the oxidative phase is ribose 5-phosphate, which serves as precursor for
nucleotides, coenzymes, and nucleic acids. In cells that are not using ribose 5-phosphate for biosynthesis, the non-oxidative phase
recycles six molecules of the pentose into five molecules of the hexose glucose 6 phosphate, allowing continued production of NADPH
and converting glucose 6-phosphate (in six cycles) to CO2.
Non-oxidative phase
PENTOSE PHOSPAHTE PATHWAY
23. The citric acid cycle is amphibolic, serving in both
catabolism and anabolism; cycle intermediates
can be drawn off and used as the starting material
for a variety of biosynthetic products.
The citric acid cycle (Krebs cycle, TCA cycle) is a
nearly universal central catabolic pathway in
which compounds derived from the breakdown of
carbohydrates, fats, and proteins are oxidized to
CO2, with most of the energy of oxidation
temporarily held in the electron carriers FADH2
and NADH. During aerobic metabolism, these
electrons are transferred to O2 and the energy of
electron flow is trapped as ATP.
26. Substrate Level Phosphorylation
Substrate level phosphorylation involves the
enzyme catalyzed transfer of inorganic
phosphate from a molecule to ADP to form ATP.
The synthesis of ATP via ETS with oxygen as
terminal electron acceptor, is known as
oxidative phosphorylation and it takes place
in mitochondria.
27. Organization of the
electron transport chain
and ATP synthesis in the
inner membrane of plant
mitochondria.
In addition to the five
standard protein complexes
found in nearly all other
mitochondria, the electron
transport chain of plant
mitochondria contains five
additional enzymes marked
in green. None of these
additional enzymes pumps
protons. Specific inhibitors,
rotenone for complex I,
antimycin for complex III,
cyanide for complex IV, and
salicylhydroxamic acid
(SHAM) for the alternative
oxidase, are important tools
to investigate the electron
transport chain of plant
mitochondria.
Electron Transport Chain
28. ATP is the energy carrier used by cells to drive living processes, and chemical energy conserved during the
citric acid cycle in the form of NADH and FADH2 (redox equivalents with high-energy electrons) must be
converted to ATP to perform useful work in the cell. This O2-dependent process, called oxidative
phosphorylation, occurs in the inner mitochondrial membrane.
The Electron Transport Chain catalyses a flow of electrons from NADH to O2,the final electron acceptor
of the respiratory process. For the oxidation of NADH, the overall two-electron transfer can be written as
follows: NADH + H+ + 1⁄2 O2 → NAD+ + H2O
For each molecule of sucrose oxidized through glycolysis and the citric acid cycle pathways, 4 molecules of
NADH are generated in the cytosol and 16 molecules of NADH plus 4 molecules of FADH2 (associated with
succinate dehydrogenase) are generated in the mitochondrial matrix. These reduced compounds must be
re-oxidized or the entire respiratory process will come to a halt.
Electron Transport Chain – Key Points
29. Each step of ETS is characterized by decrease in energy level
The carriers presumably operate in order of an increasing tendency to undergo
reduction (reducing potential becomes increasingly positive from NADH through
cyctochrome a3
Electron Transport Chain – Key Points
30. Complex I (NADH dehydrogenase). Electrons from NADH generated in the mitochondrial matrix during the citric
acid cycle are oxidized by complex I (an NADH dehydrogenase). The electron carriers in complex I include a tightly
bound cofactor (flavin mononucleotide [FMN], which is chemically similar to FAD; and several iron–sulfur centers.
Complex I then transfers these electrons to ubiquinone. Four protons are pumped from the matrix to the
intermembrane space for every electron pair passing through the complex.
Ubiquinone, a small lipid-soluble electron and proton carrier, is located within the inner membrane. It is not
tightly associated with any protein, and it can diffuse within the hydrophobic core of the membrane bilayer.
Complex II (succinate dehydrogenase). Oxidation of succinate in the citric acid cycle is catalyzed by this complex,
and the reducing equivalents are transferred via the FADH2 and a group of iron–sulfur proteins into the ubiquinone
pool. This complex does not pump protons.
Complex III (cytochrome bc1 complex). This complex oxidizes reduced ubiquinone (ubiquinol) and transfers the
electrons via an iron–sulfur center, two b-type cytochromes (b565 and b560), and a membrane-bound cytochrome
c1 to cytochrome c. Four protons per electron pair are pumped by complex III.
Cytochrome c is a small protein loosely attached to the outer surface of the inner membrane and serves as a mobile
carrier to transfer electrons between complexes III and IV.
Components of Electron Transport Chain
31. Complex IV (cytochrome c oxidase). This complex contains two copper centers (CuA and CuB) and cytochromes a
and a3. Complex IV is the terminal oxidase and brings about the four-electron reduction of O2 to two molecules of
H2O. Two protons are pumped per electron pair.
Both structurally and functionally, ubiquinone and the cytochrome bc1 complex are very similar to plastoquinone and
the cytochrome b6 f complex, respectively, in the photosynthetic electron transport chain.
The FoF1-ATP synthase (also called complex V) consists of two major components, F1 and Fo. F1 is a peripheral
membrane protein complex that is composed of at least five different subunits and contains the catalytic site for
converting ADP and Pi to ATP. This complex is attached to the matrix side of the inner membrane. Fo is an integral
membrane protein complex that consists of at least three different polypeptides that form the channel through which
protons cross the inner membrane. The passage of protons through the channel is coupled to the catalytic cycle of the
F1 component of the ATP synthase, allowing the ongoing synthesis of ATP. For each ATP synthesized, 3 H+ pass
through the Fo from the intermembrane space to the matrix down the electrochemical proton gradient.
…Components of Electron Transport Chain