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Q and complex ii

Complex II directly receives FADH 2 , which does not pass through complex I. The compound connecting the first and second complexes to the third is ubiquinone    (Q). The Q molecule is lipid soluble and freely moves through the hydrophobic core of the membrane. Once it is reduced, (QH 2 ), ubiquinone delivers its electrons to the next complex in the electron transport chain. Q receives the electrons derived from NADH from complex I and the electrons derived from FADH 2 from complex II, including succinate dehydrogenase. This enzyme and FADH 2 form a small complex that delivers electrons directly to the electron transport chain, bypassing the first complex. Since these electrons bypass and thus do not energize the proton pump in the first complex, fewer ATP molecules are made from the FADH 2 electrons. The number of ATP molecules ultimately obtained is directly proportional to the number of protons pumped across the inner mitochondrial membrane.

Complex iii

The third complex is composed of cytochrome b, another Fe-S protein, Rieske center (2Fe-2S center), and cytochrome c proteins; this complex is also called cytochrome oxidoreductase. Cytochrome proteins have a prosthetic group of heme. The heme molecule is similar to the heme in hemoglobin, but it carries electrons, not oxygen. As a result, the iron ion at its core is reduced and oxidized as it passes the electrons, fluctuating between different oxidation states: Fe ++ (reduced) and Fe +++ (oxidized). The heme molecules in the cytochromes have slightly different characteristics due to the effects of the different proteins binding them, giving slightly different characteristics to each complex. Complex III pumps protons through the membrane and passes its electrons to cytochrome c for transport to the fourth complex of proteins and enzymes (cytochrome c is the acceptor of electrons from Q; however, whereas Q carries pairs of electrons, cytochrome c can accept only one at a time).

Complex iv

The fourth complex is composed of cytochrome proteins c, a, and a 3 . This complex contains two heme groups (one in each of the two cytochromes, a, and a 3 ) and three copper ions (a pair of Cu A and one Cu B in cytochrome a 3 ). The cytochromes hold an oxygen molecule very tightly between the iron and copper ions until the oxygen is completely reduced. The reduced oxygen then picks up two hydrogen ions from the surrounding medium to make water (H 2 O). The removal of the hydrogen ions from the system contributes to the ion gradient used in the process of chemiosmosis.

Chemiosmosis

In chemiosmosis, the free energy from the series of redox reactions just described is used to pump hydrogen ions (protons) across the membrane. The uneven distribution of H + ions across the membrane establishes both concentration and electrical gradients (thus, an electrochemical gradient), owing to the hydrogen ions’ positive charge and their aggregation on one side of the membrane.

If the membrane were open to diffusion by the hydrogen ions, the ions would tend to diffuse back across into the matrix, driven by their electrochemical gradient. Recall that many ions cannot diffuse through the nonpolar regions of phospholipid membranes without the aid of ion channels. Similarly, hydrogen ions in the matrix space can only pass through the inner mitochondrial membrane through an integral membrane protein called ATP synthase ( [link] ). This complex protein acts as a tiny generator, turned by the force of the hydrogen ions diffusing through it, down their electrochemical gradient. The turning of parts of this molecular machine facilitates the addition of a phosphate to ADP, forming ATP, using the potential energy of the hydrogen ion gradient.

Questions & Answers

prove starch in a mango leaf
Ruth Reply
prove starch in a leaf
Ruth
draw and name the plant cell
Nalongo
wat is classification
Nalongo
levels of classification
Nalongo
classification of what
Ezenwa
Nidhipal
Nidhi
Identify the caste of termites or Honey bees
Mensah Reply
Soldier Winged reproductive Worker King and queen
Franklina
what is biology
Jackson Reply
biology is a study of living organism
Brilliant
what is the myelin sheath?
description on how an enzyme such as pepsin breaks down a substrate
linister Reply
what is biology
Kanzy Reply
study of life
Tufail
the study of life..meaning studying all aspects of life in humans,animals and everything inside the global
Nalukui
study of life
Memory
is the branch of science which deal with the study of living and non living things
David
Is the study of living organisms or living things
Franklina
draw the taxonomic hierarchy of classification
KC Reply
Kingdom Class Order Family Genus Species
Franklina
explain the following bush burning, deforestation, over grazing
Thomas Reply
what is biodiversity
Tracy
No idea
nana
Please what are alleles
nana
Deforestation: this is the cutting down of trees without planting new ones
Brilliant
over grazing is the continuously planting of crops in one particular land.
Friday
what is afforestation
Friday
Bush burning is the removal of the natural vegetation cover, that protects the soil surface through the use of fire. Deforestation is the actor process of establishing a forest especially on land not previously forested.
Franklina
Over grazing is the practice of grazing toi many livestock for too long a period on a land unable to recover its vegetation.
Franklina
what is physiology
Joseph Reply
the study of physical things
Nalukui
dealing with those things which you can see by your neck eyes
Odwa
Further explanation please
nana
the study of things tt interact with time,energy
David
Is the scientific study of chemistry and physics of the structure of the body
Franklina
can a lactating mother get pregnant
Elias Reply
what is cell
Deng Reply
the basic building blocks of all living matter...
Izzati
cell is a basic unit of life
MAI
building blocks ie cells not a cell there4 a cell is the basic unit of biotic things
David
Cell is a basic unit of life
Malekhotla
A cell is the basic structural and functional unit of life
Franklina
A cell is the basic unit of life,it include both plant and animals need a cell
Thomas
what's microscope
Emmanuel Reply
is any instrument that use to wiew or to see the small object that you can't see with our naked eye
MR
is any instrument used to magnifie small object
Memory
Is an instrument that produces an enlarged image of an object or specimen that is too small to be seen with our naked eye
Franklina
what is the function of the spinal cord
Gaone Reply
For responsible of movement and sensation
Franklina
A cell is the structural and fictional unit of life
Evelyn Reply
what is tidal volume
Erick
tidal volume is the volume of each breath measured during inspiration or expiration or averged for the entire respiratory cycle
Gaone
Give function of the long strands of slippery or jelly like substance in eggs of the amphibians in water ?
Erick
the long strands of slippery or jelly like substance him eggs of amphibians in water helps in keeping the eggs moist and protection from predators
Gaone
sorry not him in
Gaone
what's is microscope
Emmanuel
How do bacteria useful?
Bisirikirwa
how can plant feed other animals
Nana Reply
After the animals has death and decayed then the plant used the nutrients to manufacture there food.
Yusuf
Plants and animals depends on each other. Meaning, plants help animals with greens and fruits or vegetables while animals provides nutrients when dead and decayed. Therefore,as you see the food web and food chain, you'll have more.
Jairenaririko

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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