Biochemistry

Organisms that grow only in the absence of oxygen, avoid the gas by living in highly reduced environments such as soil.

They use fermentative processes to satisfy their energy requirements.

Depend on fermentation for their energy needs, possess detoxifying enzymes and antioxidant molecules that protect against oxygen's toxic producsts.

Not only possess the mechanics needed for detoxifying oxygen metabolites, they can also generate energy by using oxygen as an electron acceptor when the gas is present.

Are highly dependent on oxygen for energy production

They protect themselves from the potentially dangerous consequences of exposure to oxygen with elaborate mechanisms composed of enzymes and antioxidant molecules.

Facultative anaerobes and obligate aerobes.

In eukaryotes these processes occur within the mito.

- is a metabolic pathway in which 2 carbon fragments derived from organic fuel molecules are oxidized to form CO.

- the coenzymes NAD⁺ and FAD are reduced to form NADH and FADH₂, which act as electron carriers.

Is a mechanism by which electrons are transferred from reduced coenzymes to an acceptor (Q₂)

In oxidative phosphorylation, the energy released by electron transprot is captured in the form of a proton gradient that drives the synthesis of ATP, the energy currency of living orgnaisms.

Redox reactions occur when electrons are transferred between an electron donor (reducing agent) and an electron acceptor (oxidizing agent).

the tendency for a specific substance to gain electrons

The coenzyme forms of the vitamin molecules nicotonic acid and riboflavin are universal electron carriers.

• - There are two coenzyme forms of nicotinic acid:
• 1) nicotinamide adenine dinucleotide (NAD)
• 2) nicotinamide adenine dinucleotide phosphate (NADP)

oxidized: NAD⁺ and NADP⁺

reduced: NADH and NADPH

• 1) Electrons
• 2) Dehydrogenases

• - They catalyze hydride transfer reactions
• - Many dehydrogenases that catalyze reactions involved in energy generation use the coenzyme NADH
• -The enzymes that require NADPH usually catalyze biosynthetic reactions
• - A small number of dehydrogenases can use either NADH or NADPH

CH₃CH₂OH + NAD⁺ <-------> CH₃COH + NADH + H⁺

• - During this reactions NAD⁺ accepts a hydride ion from ethanol, the substrate molecule undergoing oxidation.
• - The product depronates to form the acetaldehyde molecule.

• Vitamin B₂ is a component of 2 coenzymes:
• 1) Flavin mononucleotide (FMN)
• 2) Flavin adenin dinucleotide (FAD)

FMN and FAD function as tightly bound prosthetic groups in a class of enzymes known as the flavoproteins.

Flavoproteins are a diverse group of catalysts: they funciton as dehydrogenases, oxidases, and hydroxylases.

Succinate dehydrogenase: it catalyzes the oxidation of succinate to form fumerate, important in energy production.

Electron flow may be used to generate and capture energy in aerobic respiration

Energy may also be used to drive electron flow in photosynthesis. (NADP⁺ is a more phosphorylated version of NAD⁺)

Most the aerobic cell's free energy is captured by the mitochondrial electron transport chain (ETC).

In this process, electrons are tranferred from a redox pair with a more negative potential (NADH/NAD⁺) to those with more positive reduction potentials.

The last component int he system is the H₂O/ half of O₂.