The
intermembrane space is the region between the
inner membraneThe inner membrane is the biological membrane of an organelle or Gram-negative bacteria that is within an outer membrane....
and the
outer membraneThe bacterial outer membrane is found in Gram-negative bacteria. Its composition is distinct from that of the cytoplasmic membrane - among other things, the outer leaflet of the membrane include a complex lipopolysaccharide whose lipid portion acts as an endotoxin - and it is linked to the cell's...
of a
mitochondrionIn cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5–10 micrometers in diameter...
or a
chloroplastChloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.The word chloroplast is...
. The main function of the intermembrane space is oxidative
phosphorylationPhosphorylation is the addition of a phosphate group to a protein or other organic molecule. Phosphorylation turns many protein enzymes on and off, causing or preventing the mechanisms of diseases such as cancer and diabetes....
.
Channel
proteinProteins are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer chain are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues...
s called
porinPorins are beta barrel proteins that cross a cellular membrane and act as a pore through which molecules can diffuse. Unlike other membrane transport proteins, porins are large enough to allow passive diffusion, i.e., they act as channels that are specific to different types of molecules...
s in the
outer membraneThe bacterial outer membrane is found in Gram-negative bacteria. Its composition is distinct from that of the cytoplasmic membrane - among other things, the outer leaflet of the membrane include a complex lipopolysaccharide whose lipid portion acts as an endotoxin - and it is linked to the cell's...
allow free movement of
ionAn ion is an atom or molecule where the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge...
s and small
moleculeA molecule is defined as an electrically neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds. Molecules are distinguished from polyatomic ions in this strict sense...
s into the intermembrane space. This doesn't means that it is essentially continuous with the
cytosolThe cytosol or intracellular fluid is the liquid found inside cells. In eukaryotes this liquid is separated by cell membranes from the contents of the organelles suspended in the cytosol, such as the mitochondrial matrix inside the mitochondrion...
in terms of the solutes relevant for the functioning of these
organelleIn cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid membrane....
s.
EnzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at...
s destined for the
mitochondrial matrixIn the mitochondrion, the matrix contains soluble enzymes that catalyze the oxidation of pyruvate and other small organic molecules.The mitochondrial matrix also contains the mitochondria's DNA and ribosomes. The word "matrix" stems from the fact that this space is viscous, compared to the...
or the
stromaStroma may refer to:*Stroma, Scotland, an island off the northern coast of Scotland*Stroma , the connective, functionally supportive framework of a biological cell, tissue, or organ...
can pass through the intermembrane space via transport through [1]s. These are known as
translocaseTranslocase is a general term for an enzyme that assists in moving another molecule, usually across a membrane.Translocases are most common secretion system in Gram positive bacteria.Examples include:...
of the outer mitochondria membrane (
TOMTom or TOM may refer to:*Tom , a diminutive of Thomas or Tomás *Tom or Tom Anderson, one of the founders of MySpace*Tom *Tom , a 1994 American sitcom...
) and
translocaseTranslocase is a general term for an enzyme that assists in moving another molecule, usually across a membrane.Translocases are most common secretion system in Gram positive bacteria.Examples include:...
of the inner mitochondrial membrane (
TIMTim may refer to:Names*Timothy or Tim, for short.People*Tim, the Oldenburg Baby, abortion survivor*Tim , popular K-pop solo singer*Tiny Tim , American singer, ukulele player, and musical archivist*Timati, a Russian hip-hop singer...
) in
mitochondriaIn cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5–10 micrometers in diameter...
and
translocaseTranslocase is a general term for an enzyme that assists in moving another molecule, usually across a membrane.Translocases are most common secretion system in Gram positive bacteria.Examples include:...
of the outer chloroplast membrane (TOC) and
translocaseTranslocase is a general term for an enzyme that assists in moving another molecule, usually across a membrane.Translocases are most common secretion system in Gram positive bacteria.Examples include:...
of the inner chloroplast membrane (TIC) in
chloroplastChloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.The word chloroplast is...
s. It tends to have a low
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
because of the proton gradient which results when
protonThe proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom but is also stable by itself and has a second identity as the hydrogen ion, H
+...
s are pumped from the
mitochondrial matrixIn the mitochondrion, the matrix contains soluble enzymes that catalyze the oxidation of pyruvate and other small organic molecules.The mitochondrial matrix also contains the mitochondria's DNA and ribosomes. The word "matrix" stems from the fact that this space is viscous, compared to the...
into the intermembrane space during electron transport. The structures responsible for this are
coenzyme QCoenzyme Q10 is a 1,4-benzoquinone, where Q refers to the quinone chemical group, and 10 refers to the isoprenyl chemical subunits.This oil-soluble vitamin-like...
, NADH coenzyme Q
oxidoreductaseIn biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule to another .- Reactions :...
complex (complex I), succinate-coenzyme Q
oxidoreductaseIn biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule to another .- Reactions :...
complex (complex II), and coenzyme Q-
cytochromeCytochromes are, in general, membrane-bound hemoproteins that contain heme groups and carry out electron transport.They are found either as monomeric proteins or as subunits of bigger enzymatic complexes that catalyze redox reactions...
c
oxidoreductaseIn biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule to another .- Reactions :...
complex (complex III).
Intermembrane space of mitochondria
Because of channels in the
outer membraneThe bacterial outer membrane is found in Gram-negative bacteria. Its composition is distinct from that of the cytoplasmic membrane - among other things, the outer leaflet of the membrane include a complex lipopolysaccharide whose lipid portion acts as an endotoxin - and it is linked to the cell's...
of the mitochondria, the content of the intermembrane space is similar to that of the content of the cytoplasm.
Intermembrane space of chloroplast
The intermembrane space of the
chloroplastChloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.The word chloroplast is...
is extremely small, somewhere from 10-20 nm thick.