10. Energetics, mitochondrion Flashcards
metabolis, aerobic anaero
metabolism
The coordinated processes of material uptake, conversion of materials and excretion of
substances taking place between the living system and its environment, which provides the
living being with adequate building materials and energy.
Aerobic, anaerobic
Aerobic: A process that requires the presence of oxygen in the air or a living organism whose
metabolism requires oxygen. Anaerobic: A process that does not require oxygen to happen or
a living organism that does not require oxygen for its metabolism.
glycolisis , oxidative phos
glycolysis
The glycolysis is a series of enzyme-catalyzed catabolic reactions in the cytosol of the cells, in
which sugars, especially glucose, are partially degraded. The energy released from the process
is stored in ATP molecules (and NADH). Two pyruvate molecules and netto two ATP
molecules are created from one glucose molecule. (Pyruvate is fermented into lactic acid or
ethanol in the absence of oxygen, otherwise it can enter into the tricarboxylic acid cycle.)
oxidative phosphorylation
During the so-called terminal oxidation catabolic products (mainly the products of glycolysis),
protons accumulate outside the inner membrane of mitochondrion and flow back to the matrix
of the mitochondrion across specific proton channels of ATP synthase (F0F1 ATPase) enzymes,
and the released energy is used to synthesize ATP from ADP and inorganic phosphate
ATP, Synthase
ATP (Adenosine triphosphate)
A nucleotide containing adenine, which is a vital source of chemical energy in all living
organisms. Adenine is bound to a D-ribose (making an adenosine) and the D-ribose also carries
three phosphate groups linked with linear covalent bonds. The second and third phosphate
groups are linked with a high energy acid anhydride bond. Because of this latter feature, ATP
is capable of storing energy, which can be used by cells.
ATP synthase
The ATP synthase is a molecule complex localized in the inner membrane of mitochondria and
catalyses the synthesis of ATP from ADP and inorganic phosphate (Pi). It has two main parts:
the membrane spanning proton channel (F0) and the ATP synthetizing (F1) part. For ATP synthesis, the energy is supplied by the passive proton flow across the F0 proton channel, driven
by the electrochemical potential gradient of the proton. At high ATP concentrations the
synthase can work in reverse direction, acting as a proton pumping ATPase
chemostatic, mitochondrion
Chemiosmotic theory
The energy released during the electron transport via the complexes of the respiratory chain in
the inner mitochondria membrane drives protons actively to the intermembrane space (by
proton pumps); therefore the proton concentration in the intermembrane space (and in the
cytoplasm) is higher than in the matrix. (Similar proton gradient is created across the thylakoid
membrane of chloroplast during the reactions of light-dependent part of the photosynthesis.)
The movement of protons along their electrochemical potential through the special proton
channel of ATP synthetize drives the phosphorylation of ADP to ATP.
mitochondrion
The mitochondrion is an organelle with variable shape, size and number in eukaryotic cells and
has endosymbiotic origin. The majority of energy production of cells happens in mitochondria.
They are bounded by two membranes having different compositions. The invaginations of inner
membrane containing cardiolipin are the christae. The mitochondrial DNA and mitochondrial
ribosomes and the enzyme collection of citric acid cycle are localized in the matrix. The electron
transport chain necessary for the terminal oxidation and the ATP-synthase are located in the
inner membrane.
respiratori chan , citochrome
respiratory chain
The respiratory chain is localized in the inner membrane of mitochondria and is composed of
proton pumping molecules which are easily oxidised and reduced and also hem containing
cytochrome proteins. The electron transport chain receives electrons from high energy NADH
produced in the citric acid cycle and while electrons go through the components of the
respiratory chain to the final electron acceptor, the O2 molecules (in case of aerob respiration),
protons are pumped from the matrix to the intermembrane space by the released energy. At the
end of the chain, the electrons together with the electron acceptor oxygen and protons returned
across the inner membrane during ATP synthesis create H2O molecules.
cytochromes
Complex iron containing proteins, in which the iron is contained in the molecule called hem,
similarly to haemoglobin. The central iron ion of the hem can undergo redox reactions: reduced
by electron capture (Fe33+ + e → Fe2 +) or oxidized by electron loss. Cytochromes are members
of the enzyme systems of both the terminal oxidation and of photosynthesis. In apoptotic cells
Cytochrome C is released from mitochondria into the cytosol and initiates a caspase cascade
thereby inducing programmed cell death.
thermogenic, porin
Thermogenin (UCP)
The thermogenin is a protein in the inner membrane of mitochondrion which works as a proton
transporter in brown adipose tissues. Its main role is to produce heat by short cutting the proton
gradient and thus maintaining the constant core temperature of cold adapted animals (seals,
whales). In humans, it can be found in brown adipose tissues of infants.
porin
The porins are channel-forming transmembrane proteins localized in the outer membrane of
mitochondria (and also in the membrane of Gram-negative bacteria). The porins make the outer membrane permeable to small molecules (≤5 kDa). Therefore, the concentrations of ions and
small molecules are practically the same in the intermembrane space and in the cytoplasm.
cardiolipin, mito DNA
cardiolipin
Cardiolipin is a diphosphatidylglycerol, which has four fatty acid chains. This special lipid
component of the inner mitochondrial membrane reduces the proton-permeability of the
membrane and thus facilitates the production of proton gradients. Its other role is to stabilize
the conformation of the protein complexes (e.g. cytochrome C) of the respiratory chain.
mitochondrial DNA
Mitochondrial DNA is circular, double-stranded DNA and has many copies in each
mitochondrion. It is derived from the circular genomes of the bacteria that were engulfed by
the early ancestors of today’s eukaryotic cells according to endosymbiotic theory. mtDNA does
not have chromosomal structure, and does not contain histones. In most multicellular
organisms, mtDNA is inherited from the mother.
Coding of mitochondrial proteins
Some of the proteins of the mitochondrion are coded by its own genome, the mitochondrial
DNA. The human mitochondrial DNA codes for 13 proteins and further 24 RNA molecules.
The majority of mitochondrial proteins is coded by the genomic (nuclear) DNA and their
synthesis is carried out on the cytoplasmic ribosomes from where they are transported into the
mitochondria. The genetic code used in mitochondrial DNA is unique, it shows some alterations
compared to the universal code used in prokaryotes or eukaryotes, and it can vary among
different species.
proofs for the bacterial origin of mitochondria
Mitochondria have their own DNA, whose structure are different from the genomic DNA (they
are circular, present in many copies, not organized into chromosomes, generally contain no
introns and are transcribed from common promoter).
The size of mitochondria is similar to the size of the majority of bacteria (~ 1 µm).
Mitochondria are bounded by two membranes which are different from each other both in their
chemical compositions and structure: The composition of the outer membrane is similar to that
of the host cell membrane, whereas the composition of the inner membrane to that of the
bacterial membranes.
The genetic code of the mitochondria is different from the universal code in some cases.
The size and sensitivity to antibiotics of mitochondrial ribosomes are similar to that of bacterial
ribosomes.
The mitochondrial heat-shock proteins (Hsp60) are similar to bacterial hsp proteins.
The mitochondria divide independently from the host cells by binary fission, like bacteria
