Mitochondria

Mitochondria Peroxisomes and glyoxisomes[Documenttitle]
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SUBMITTEDTO: Mrs.RAKHSHANDAAFRIDI
SUBMITTEDBY: SADIASAEED
ROLL#: 381611063
DISCIPLINE: BS-ZOOLOGY(V)
SUBJECT: CELLANDMOLECULARBIOLOGY
TOPIC: MITOCHONDRIA,PEROXISOMES,GLYOXISOMES

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DATE: 31-10-2018
are organelles found in the cytoplasm of all eukaryotic cells. They vary
considerably in shape and size, but are all composed of four compartments: a smooth outer
membrane, a convoluted inner membrane that forms recognizable structures called cristae, the
intermembrane space, and the matrix. Mitochondria are the "powerhouses" of cells; their function is
to convert energy found in nutrient molecules and store it in high-energy phosphate bonds in a
molecule called , which is the universal energy-yielding component necessary
for the reactions that modulate many fundamental cellular processes. Mitochondrial ATP is produced
through the process of oxidative phosphorylation, a process that uses molecular oxygen as the final
electron acceptor.

3
Mitochondria are thought to have originated from an ancient symbiosis that resulted when a
nucleated cell engulfed an aerobic prokaryote. The engulfed cell came to rely on the
protective environment of the host cell, and, conversely, the host cell came to rely on the
engulfed prokaryote for energy production.
Over time, the descendants of the engulfed prokaryote developed into mitochondria, and the
work of these organelles — using oxygen to create energy — became critical to eukaryotic
evolution.
The shape of mitochondria varies according to the functional stages of the cell. In general,
these organelles are filamentous or granular. A long mitochondrion may swell at one end to
assume the form of a. At other times, mitochondria may become vesicular by the
appearance of a central clear zone. The size of mitochondria is also variable; however, in
most cells the width is relatively constant (about 0.5 µm), and the length is variable,
reaching a maximum of 7 µm. They are uniformly distributed throughout the cytoplasm,
but there may be exceptions. For example, in certain muscle cells, mitochondria are grouped
like rings or braces around the I-band of the myofibril, or in sperm they are wrapped tightly
around the flagellum.

4
The number of mitochondria in a cell depends on the type and functional state of the cell. A
normal liver cell contains between 1,000 and 1,600 mitochondria, but this number
diminishes during regeneration and also in cancerous state. The number may be as high as
3,00,000 in some oocytes, and some algal cells may contain only one mitochondrion.
In a 1981 review of the history of mitochondria in the Journal of Cell Biology, authors Lars
Ernster and Gottfried Schatz note that the first true observation of mitochondria was by
Richard Altmann in 1890. While Altmann called them “bioblasts,” their current, visually
descriptive name was given by Carl Benda in 1898, based on his observations of developing
sperm. “Mitochondria” derives from two Greek words: “mitos” meaning thread, and
“chondros” meaning granule. As described by Karen Hales, a professor of biology at Davidson
College, in Nature Education, these organelles are dynamic, and constantly fuse together to
form chains, and then break apart. Individual mitochondria are capsule shaped, with an
outer membrane and an undulating inner membrane, which resembles protruding fingers.
These membranous pleats are called cristae, and serve to increase the overall surface area of
the membrane. When compared to cristae, the outer membrane is more porous and is less
selective about which materials it lets in. The matrix is the central portion of the organelle
and is surrounded by cristae. In some cases, the matrix contains a finely filamentous
material, or highly dense small granules. These granules contain phospholipids, which give
them an affinity for calcium. Within the matrix small ribosomes (55S), circular DNA, some
soluble proteins and lipids are present.

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Mitochondria are unlike most organelles (with an exception of plant chloroplasts) in that
they have their own set of DNA and genes that encode proteins. They vary in size and
structure. According to Sloan, the genomes of most flowering plants are about
100,000 base pairs in size, and can be as large as 10 million base pairs. In contrast,
mammalian genomes are about 15,000 to 16,000 base pairs in size.
Cristae: In general, the mitochondrial crests are incomplete septa or ridges that do not
interrupt the continuity of the inner chamber; thus, the matrix is continuous within the
mitochondrion. The cristae of animal cells are usually lamellar or plate-like, but in many
protozoa and in steroid synthesizing cells including the adrenal cortex and corpus luteum,
they occur as regularly packed tubules. The cristae greatly increase the area of inner
membrane. In liver cell mitochondria, the cristae membrane is 3-4 times greater than the
outer membrane area. The number of cristae may also vary in different cell types. For
example, mitochondria of heart, kidney and skeletal muscle cells have more extensive cristae
arrangements but the non-myelinated axons of rabbit brain have only one crista.

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If a mitochondrion is allowed to swell and break in a hypotonic solution and is then
immersed in phospho-tungstate, the inner membrane in the crest appears covered by
particles of 8.5 nm. These particles have a stem linking each with the membrane These
particles are called ‘elementary’ or ‘F1‘ or F0-F1‘ particles and are regularly spaced at
intervals of 10 nm on the inner surface of these membranes. There may be 104
-
105
elementary particles per mitochondrion. Actually these particles correspond to a special
ATP synthase involved in the coupling of oxidation and phosphorylation.Electron micrographs
revealed that the inner membrane bound F1 particle or the enzyme ATP synthase consists of
two major portions the F1 head piece, which consists of five different subunits, alpha (α),
beta (β), gamma (γ), delta (δ) and epsilon (ε), with the probable ratio of 3α : 3β : 1δ : 1γ :
1ε; and the F0 base piece.The F0 base piece remains embedded in the membrane and consists
of three different subunits in the ratio of 1a : 2b : 12c. The b subunit of F0 extends into the
head piece and forms the stalk (stem).
The presence of such F1 particles on the matrix side (M) confers to the inner mitochondrial
membrane, a characteristic asymmetry that is of fundamental importance to its function
i.e., formation of ATP.
Structuralvariationindifferentcelltype
Beyond the acknowledged membrane arrangement, the morphology, and indeed distribution
of the organelle, varies enormously among cell types. The conventional description of
mitochondrial structure is derived largely from electron microscopy (EM) studies and
characterizes mitochondria as spherical or short rod structures positioned in various parts of
the cytoplasm. However, the significant extent to which mitochondria differ between cells is
only beginning to be acknowledged. Mitochondria in fibroblasts are usually long filaments (1-
10 μm in length with a fairly constant diameter of ∼700 nm), whereas in hepatocytes

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mitochondria are more uniformly spheres or ovoid. In native vascular smooth muscle,
mitochondria are ovoid or rod-shaped organelles, whereas in the endothelium a tubular
mitochondrial network exists. Even within individual cells, mitochondrial structure varies. In
skeletal muscle, mitochondria are ovoid structures and two populations may exist – one
positioned close to the sarcolemma, the other embedded among the myofibrils. The sub
sarcolemma mitochondria are rounder and smaller than those embedded among the
myofibrils. In pancreatic acinar cells there are three different regional groups of functionally
unconnected mitochondria; one group in the peripheral basolateral region close to the
plasma membrane, another around the nucleus and a third positioned in the periphery of
the granular region separating the granules from the basolateral area.
The three distinct mitochondrial groups may serve various functions as implied by the
observation that each group is activated independently by specific types of cytosolic
Ca2+
signals. In cardiac myocytes there are also three distinct populations: perinuclear,
subsarcolemmal and interfibrillar. Mitochondria in the perinuclear region are more rounded
in appearance and densely packed than elsewhere.
Mitochondria have long been known to participate in the process of cell injury associated
with metabolic failure. Only recently, however, have we come to appreciate the role of
mitochondria as primary intracellular targets in the initiation of cell dysfunction. In addition
to ATP synthesis, mitochondria are also critical to modulation of cell redox status, osmotic
regulation, pH control, and cytosolic calcium homeostasis and cell signaling. Mitochondria are

8
susceptible to damage by oxidants, electrophiles, and lipophilic cations and weak acids.
Chemical-induced mitochondrial dysfunction may be manifested as diverse bioenergetic
disorders and considerable effort is required to distinguish between mechanisms involving
critical mitochondrial targets and those in which mitochondrial dysfunction is secondary and
plays only a modulatory role in cell injury.
The mitochondrial membranes can be separated by density gradient centrifugation. The
outer membrane is separated by causing a swelling which can be brought about by breakage
followed by contraction of inner membrane and matrix.
Certain detergents like digitonin and lubrol are often used for this purpose. When outer
membrane is removed with digitonin, the so-called mitoplast is formed. Mitoplast includes
the inner membrane with unfolded cristae and matrix. The isolated outer membrane is
revealed by negative staining as a ‘folded bag’ with smooth surface (Fig. 3.15). The mitoplast
has pseudopodic processes and is able to carry out oxidative phosphorylation.
The outer membrane fraction has 40% lipid content and has more cholesterol and higher
phosphatidyl inositol compared to the inner membrane which has only 20% lipid content
and higher cardiolipin.

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The lipid/protein ratio of outer membrane is about 0.8 and about 0.3 in the inner
membrane. The outer membrane contains the channel protein porin of 29,000 Daltons
which is absent in the inner membrane. On the other hand, the outer membrane lacks the
elementary particles that are prominent in the inner membrane.
The gross chemical composition of the mitochondria varies in different animal and plant
cells. In general, mitochondria are found to contain 65 to 70% proteins, 25 to 30% lipids,
0.5% RNA and small amount of DNA.
The lipid content’ of mitochondria are composed of 90% phospholipids, 5% or less cholesterol
and 5% free fatty acids and triglycerides. The inner membrane is rich in the phospholipid,
called cardiolipin that makes the membrane impermeable to various ions and small
molecules.
The enzyme composition of mitochondrial compartments and membranes are shown in
Table 3.2:

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a. Mitochondria function as energy-transducing organelle into which the major degradation
products of cell metabolism penetrate and are converted into chemical energy (ATP) that is
used in various activities of the cell.
The process of energy transformation that occur in mitochondria are based on three co-
ordinated steps:
i. Krebs cycle, carried out by a series of soluble enzymes present in the matrix, which
produces CO2 by decarboxylation and removes electrons from the metabolites.
(ii) The respiratory chain or electron transport system, which captures the pairs of electrons
and transfers them through a series of electron carriers, which finally leads by combination
with activated oxygen to the formation of H2O.
(iii) A phosphorylating system, tightly coupled in the respiratory chain, which at three points
gives rise to ATP molecules.
b. In the mitochondria of all cells, the outer membrane enzymes mediate the movement of
free fatty acids into the mitochondrial matrix. In the matrix, each fatty acid molecule is
broken down completely by a cycle of reactions, called P-oxidation that trims two carbons
from its carboxyl end, generating one molecule of acetyl-CoA in each turn of cycle. This
acetyl-CoA is fed into Krebs cycle for further oxidation.

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c. Besides the ATP production, mitochondria perform certain biosynthetic or anabolic
functions. It contains DNA and the machinery needed for protein synthesis. Therefore, it can
make different proteins of its own. These proteins include subunits of ATP synthase, portions
of the reductase and three of the seven subunits in cytochrome oxidase. The synthesis of
heme (needed for myoglobin, hemoglobin) begins with a mitochondrial reaction catalyzed by
the enzyme delta or d-aminolaevulinic acid synthetase. Likewise, some early steps in the
conversion of cholesterol to steroid hormones in the adrenal cortex are also catalyzed by
mitochondrial enzymes.
The sensitivity of mitochondria to permeability transition and apoptotic signaling are the
most extensively documented The mitochondrial permeability transition pore (mPTP) is
presumed to consist in a multiprotein complex located in the IMM, which is modulated by
interactions with OMM proteins he mitochondrial permeability transition
pore (mPTP or MPTP; also referred to as PTP, mTP or MTP) is a protein that is formed in
the inner membrane of the mitochondria under certain pathological conditions such
as traumatic brain injury and stroke. Opening allows increase in the permeability of
the mitochondrial membranes to molecules of less than 1500 Daltons in molecular weight.
Induction of the permeability transition pore, mitochondrial membrane permeability
transition (mPT or MPT), can lead to mitochondrial swelling and cell
death through apoptosis or necrosis depending on the particular biological setting.

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The composition and regulation of the mitochondrial PTP (mPTP) is still a matter of
debate, but putative mPTP components include cyclophilin D (CypD) and the adenine
nucleotide translocase (ANT), and postulated regulatory proteins include hexokinase, creatine
kinase, and peripheral benzodiazepine receptor (PBR) Although the full details of these events
are still only partially characterized and are in need of further clarification it is established
that irreversible opening of the mPTP in a high conductance mode occurs in response to
diverse cellular stressors such as matrix Ca2+
, loss of membrane potential, and ROS leading
to the release of proapoptotic factors inducing cell death .Furthermore, because
mitochondrial respiration becomes uncoupled when the mPTP is open, prolonged
permeability transition can lead to ATP depletion and bioenergetic crisis contributing to cell
death.
Inner membrane permeability
The inner membrane is freely permeable to oxygen, carbon dioxide, and water only.[8]
It is
much less permeable to ions and small molecules than the outer membrane, creating
compartments by separating the matrix from the cytosolic environment. This

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compartmentalization is a necessary feature for metabolism. The inner mitochondrial
membrane is both an electrical insulator and chemical barrier. Sophisticated ion
transporters exist to allow specific molecules to cross this barrier. There are
several antiport systems embedded in the inner membrane, allowing exchange
of anions between the cytosol and the mitochondrial matrix
Mitochondrial biogenesis is the process by which cells increase mitochondrial mass. It was
first described by John Holloszy in the 1960s, when it was discovered that
physical endurance training induced higher mitochondrial content levels, leading to greater
glucose uptake by muscles.[3]
Mitochondrial biogenesis is activated by numerous different
signals during times of cellular stress or in response to environmental stimuli, such as aerobic
exercise. The ability for a mitochondrion to self-replicate is rooted in its evolutionary history.
It is commonly thought that mitochondria descend from cells that
formed endosymbiotic relationships with α-protobacteria, they have their own genome for
replication.[5]
However, recent evidence suggests that mitochondrial may have evolved
without symbiosis.[6]
The mitochondrion is a key regulator of the metabolic activity of the
cell, and is also an important organelle in both production and degradation of free
radicals.[7]
It is reckoned that higher mitochondrial copy number (or higher mitochondrial
mass) is protective for the cell.
Mitochondria are produced from the transcription and translation of genes both in the
nuclear genome and in the mitochondrial genome. The majority of mitochondrial protein
comes from the nuclear genome, while the mitochondrial genome encodes parts of
the electron transport chain along with mitochondrial rRNA and tRNA. Mitochondrial
biogenesis increases metabolic enzymes for glycolysis, oxidative phosphorylation and

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ultimately a greater mitochondrial metabolic capacity. However, depending on the energy
substrates available and the REDOX state of the cell, the cell may increase or decrease the
number and size of mitochondria.[8]
Critically, mitochondrial numbers and morphology vary
according to cell type and context-specific demand, whereby the balance between
mitochondrial fusion/fission regulates mitochondrial distribution, morphology, and function
Fusion and fission
Mitochondria are highly versatile and are able to change their shape through fission and
fusion events. Definitively, fission is the event of a single entity breaking apart, whereas
fusion is the event of two or more entities joining to form a whole. The processes of fission
and fusion oppose each other and allow the mitochondrial network to constantly remodel
itself If a stimulus induces a change in the balance of fission and fusion in a cell, it could
significantly alter the mitochondrial network. For example, an increase in mitochondrial
fission would create many fragmented mitochondria, which has been shown to be useful for
eliminating damaged mitochondria and for creating smaller mitochondria for efficient
transporting to energy-demanding areas.
In mammals, mitochondrial fusion and fission are both controlled by GTPases of the
dynamin family.[8][14]
The process of mitochondrial fission is directed by Drp1, a member of
the cytosolic dynamin family.[8][9]
This protein forms a spiral around mitochondria and
constricts to break apart both the outer and inner membranes of the organelle.
The processes of fusion and fission allow for mitochondrial reorganization.
PGC-1α, a member of the peroxisome proliferator-activated receptor gamma (PGC) family
of transcriptional coactivators, is the master regulator of mitochondrial biogenesis. It is
known to co-activate nuclear respiratory factor 2 (NRF2/GABPA), and together with NRF-
2 coactivates nuclear respiratory factor 1 (NRF1).[16][17]
The NRFs, in turn, activate the
mitochondrial transcription factor A (tfam), which is directly responsible for transcribing

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nuclear-encoded mitochondrial proteins.[16][17]
This includes both structural mitochondrial
proteins as well as those involved in mtDNA transcription, translation, and repair.[]
PGC- 1β,
a protein that is structurally similar to PGC-1α, is also involved in regulating mitochondrial
biogenesis, but differs in that it does not get increased in response to exercise. While there
have been significant increases in mitochondria found in tissues where PGC-1α is
overexpressed, as the cofactor interacts with these key transcription factors, knockout mice
with disrupted PGC-1α are still viable and show normal mitochondrial abundance. Thus,
PGC-1α is not required for normal development of mitochondria in mice.
Mitochondria
Peroxisomes were identified as organelles by the Belgian cytologist Christian de Duve in
1967[6]
after they had been first described by a Swedish doctoral student, J. Rhodin in
1954. A peroxisome is a type of organelle known as a microbody, found in virtually
all eukaryotic cells.[2]
They are involved in catabolism of very long chain fatty acids, branched
chain fatty acids, D-amino acids, and polyamines, reduction of reactive oxygen species –
specifically hydrogen peroxide[3]
– and biosynthesis of plasmalogens. They also contain
approximately 10% of the total activity of two enzymes in the pentose phosphate pathway,
which is important for energy metabolism. Other known peroxisomal functions include
the glyoxylate cycle in germinating seeds ("glyoxysomes") photorespiration in
leaves,[5]
glycolysis in trypanosomes ("glycosomes"), and methanol and/or amine oxidation
and assimilation in some yeasts.

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Analyzing the structures of peroxisomes has helped figure their function and role in the
biological world. Peroxisomes are derived from the endoplasmic reticulum and replicate by
fission. This organelle is surrounded by a lipid bilayer membrane which encloses the
crystalloid core. The bilayer is a plasma membrane which regulates what enters and exits the
peroxisome. There are at least 32 known peroxisomal proteins, called peroxins, which carry
out peroxisomal function inside the organelle.
Peroxisomes can be derived from the endoplasmic reticulum and replicate by
fission.[13]
Peroxisome matrix proteins are translated in the cytoplasm prior to import.
Specific amino acid sequences (PTS or peroxisomal targeting signal) at the C-
terminus (PTS1) or N-terminus (PTS2) of peroxisomal matrix proteins signals them to be

17
imported into the organelle. There are at least 32 known peroxisomal proteins,
called peroxins,[14]
which participate in the process of peroxisome assembly. Proteins do not
have to unfold to be imported into the peroxisome. The protein receptors, the
peroxins PEX5 and PEX7, accompany their cargoes (containing a PTS1 or a PTS2 amino
acid sequence, respectively) all the way into the peroxisome where they release the cargo and
then return to the cytosol – a step named recycling. A model describing the import cycle is
referred to as the extended shuttle mechanism.[15]
There is now evidence that ATP hydrolysis
is required for the recycling of receptors to the cytosol. Also, ubiquitination appears to be
crucial for the export of PEX5 from the peroxisome, to the cytosol.
Peroxisomes contain at least 50 different enzymes, which are involved in a variety of
biochemical pathways in different types of cells. Peroxisomes originally were defined as
organelles that carry out oxidation reactions leading to the production of hydrogen peroxide.
Because hydrogen peroxide is harmful to the cell, peroxisomes also contain the
enzyme catalase, which decomposes hydrogen peroxide either by converting it to water or by
using it to oxidize another organic compound. A variety of substrates are broken down by
such oxidative reactions in peroxisomes, including uric acid, amino acids, and fatty acids. The
oxidation of fatty acids (Figure 10.25) is a particularly important example, since it provides
a major source of metabolic energy. In animal cells, fatty acids are oxidized in both
peroxisomes and mitochondria, but in yeasts and plants fatty acid oxidation is restricted to
peroxisomes.
The oxidation of a fatty acid is accompanied by the production of hydrogen peroxide (H2O2)
from oxygen. The hydrogen peroxide is decomposed by catalase, either by conversion to
water or by oxidation of another organic compound (designated AH2).

18
In addition to providing a compartment for oxidation reactions, peroxisomes are involved in
lipid biosynthesis. In animal cells, cholesterol and dolichol are synthesized in peroxisomes as
well as in the ER. In the liver, peroxisomes are also involved in the synthesis of bile acids,
which are derived from cholesterol. In addition, peroxisomes contain enzymes required for
the synthesis of plasmalogens—a family of phospholipids in which one of the hydrocarbon
chains is joined to glycerol by an ether bond rather than an ester bond Plasmalogens are
important membrane components in some tissues, particularly heart and brain, although
they are absent in others.
The plasmalogen shown is analogous to phosphatidylcholine. However, one of the fatty acid
chains is joined to glycerol by an ether, rather than an ester, bond. Peroxisomes play two
particularly important roles in plants. First, peroxisomes in seeds are responsible for the
conversion of stored fatty acids to carbohydrates, which is critical to providing energy and
raw materials for growth of the germinating plant. This occurs via a series of reactions
termed the glyoxylate cycle, which is a variant of the citric acid cycle. The peroxisomes in
which this takes place are sometimes called glyoxysomes.
Plants are capable of synthesizing carbohydrates from fatty acids via the glyoxylate cycle,
which is a variant of the citric acid cycle. As in the citric acid cycle, acetyl CoA combines
with oxaloacetate to form citrate, which is converted to isocitrate. However, instead of being
degraded to CO2 and α-ketoglutarate, isocitrate is converted to succinate and glyoxylate.
Glyoxylate then reacts with another molecule of acetyl CoA to yield malate, which is
converted to oxaloacetate and used for glucose synthesis.

19
The Work of Harry Beevers(in 1961)  They analyzed the linear sucrose gradients of
endosperm homogenates and showed that the glyoxylate cycle.  Enzymes were found in an
organelle fraction that was not mitochondria .  Beevers and Breidenbach called these new
organelles glyoxysomes. Beevers and their postdoctoral fellow was Bill Breidenbach.
Glyoxysomes are specialized peroxisomes found in plants (particularly in the fat storage
tissues of germinating seeds) and also in filamentous fungi. Seeds that contain fats and oils
include corn, soybean, sunflower, peanut and pumpkin.[1]
As in all peroxisomes, in
glyoxysomes the fatty acids are oxidized to acetyl-CoA by peroxisomal β-oxidation enzymes.
When the fatty acids are oxidized hydrogen peroxide (H2O2) is produced as oxygen (O2) is
consumed.[1]
Thus the seeds need oxygen to germinate. Besides peroxisomal functions,
glyoxysomes possess additionally the key enzymes of glyoxylate cycle (isocitrate
lyase and malate synthase) which accomplish the glyoxylate cycle bypass

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.
Thus, glyoxysomes (as all peroxisomes) contain enzymes that initiate the breakdown of fatty
acids and additionally possess the enzymes to produce intermediate products for the
synthesis of sugars by gluconeogenesis. The seedling uses these sugars synthesized from fats
until it is mature enough to produce them by photosynthesis. Glyoxysomes also participate in
photorespiration and nitrogen metabolism in root nodules. Succinate produced in
Glyoxysomes is ultimately converted to sucrose in the cytosol. It is presumed that presence
of glyoxysomes in senescent organs is in response to the mobilization of membrane lipids.
Glyoxysomes have the following characteristics:
(1) They have a single membrane.
(2) They have high equilibrium density in sucrose gradient centrifugation.
(3) Their matrix (internal content) is finely granular
The glyoxysomes were shown to be the site of b -oxidation in castor bean endosperm (Cooper
& Beevers, 1969b; Hutton & Stumpf, 1969). Glyoxysomes isolated from this tissue oxidized
palmitoyl-CoA to acetyl-CoA with a concomitant reduction of NAD+
and uptake of oxygen.
Addition of [14
C] oxaloacetate during this reaction resulted in the formation of [14
C] citrate
and [14
C] malate from palmityl-CoA indicating that the acetyl-CoA produced by the b -
oxidation process was consumed in the glyoxyllate cycle also located in the organelle (Cooper

21
& Beevers, 1969b). Similarly, ricinoleate, linoleate and palmitate were oxidized by
glyoxysomes of castor bean with the formation of acetyl-CoA, and three enzymes of the b -
oxidation complex, crotonase, b -ketothiolase, and b -hydroxyacyl dehydrogenase were
found to be located specifically in the organelle (Hutton & Stumpf, 1969). The activity of
the b -oxidation complex in this tissue during the germination of the seed was found to
parallel the increase in activity of the glyoxylate cycle enzymes indicating that an integrated
system for lipid utilization develops together with the formation of the glyoxysome.
Convert acetyl CoA into succinate for the synthesis of carbohydrates.
 Fatty acid → Carbohydrates  In Microorganisms in the absence of glucose this cycle
allows cells to utilize carbon compounds as a carbon source. Absent in lipid-poor seed such as
the pea. Role In Glyoxylate Cyclic Present in plants e.g. (Oil rich seeds) Soya beans, Castor
beans, Sunflower bea. Present at the time of Germination (Plant seedling)  Removed in
living plants when they become able to produce their own food from photosynthesis 
Energy comes from the stored fatty acids Fatty acid → Carbohydrates  Glyoxysomes
undergo catabolism & anabolism of lipids. Catabolism carried by the enzymes present in
glyoxysomes (Glyoxylate Cycle) Contain material to begin formation of new plants Form
epicotyl & hypocotyl.

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Temporary structures • When body sustain itself (roots & shoots are developed) they are
removed • Seeds → Germination → Plant body.
Enzymes involve in Glyoxylate Cycle
The glyoxylate cycle utilizes five enzymes that are following:
 Citrate synthase
 Aconitase
 Isocitrate lyase
 Malate synthase
 Malate dehydrogenase
 https://micro.magnet.fsu.edu
 https://www.ncbi.nlm.nih.gov
 https://biologydictionary.net
 https://www.slideshare.net/Dilippandya/glyoxysomes

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