7.3 Energy Transformation 

•Fats are catabolised by hydrolysis to free fatty acids and glycerol. The glycerol enters glycolysis and thefatty acids are broken down by betaoxidation to release acetyl-CoA, which then is fedinto the citric acid cycle. Fatty acids release more energy upon oxidation thancarbohydrates because carbohydrates contain more oxygen in their structures.

Amino acids are either used to synthesizeproteins and other biomolecules, or oxidized to urea and carbon dioxide as a source ofenergy. The oxidation pathway starts with the removal of the amino group by a transaminase. The aminogroup is fed into the urea cycle, leaving adeaminatedcarbonskeleton in the form of a keto acid. Several of these keto acids areintermediates in the citric acid cycle, for example the deamination of glutamateforms α-ketoglutarate. The glucogenic amino acids can also be converted intoglucose, through gluconeogenesis.

In oxidative phosphorylation, the electrons removed from organicmolecules are transferred to oxygen and the energy released is used to make ATP. This is done in eukaryotes by a series of proteins in the membranes ofmitochondria called the electron transport chain. In prokaryotes, these proteins arefound in the cell's inner membrane. These proteins use the energy released frompassing electrons from reduced molecules like NADH onto oxygen to pump protonsacross a membrane. Pumping protons out of the mitochondria creates a protonconcentration difference across the membrane and generates an electrochemicalgradient. This force drives protons back into the mitochondrion through thebase of an enzyme called ATP synthase. The flow of protons makes the stalksubunit rotate, causing the active site of the synthase domain to change shape and phosphorylateadenosine diphosphate - turning it into ATP.

•Chemolithotrophy is a type of metabolism found inprokaryotes where energy is obtained from the oxidation of inorganic compounds. These organisms can use hydrogen,reduced sulfur compounds (such as sulfide, hydrogensulfide and thiosulfate), ferrous iron (FeII) or ammonia as sources of reducing power and they gain energy from the oxidationof these compounds with electron acceptors such as oxygen or nitrite. These microbial processes are importantin global biogeochemical cycles such as acetogenesis, nitrification and denitrification and are critical for soil fertility.

fructose ['frʌktəus] n. 果糖

pyruvate [pai'ru:veit] n. 丙酮酸盐

metabolic pathway 代谢途径

acetyl-CoA 乙酰辅酶A

citric acid cycle柠檬酸循环，三羧酸循环

lactate ['lækteit] n. 乳酸

lactate dehydrogenase 乳酸脱氢酶

catabolise [kə'tæbəlaiz] v.（使）分解代谢

fatty acid 脂肪酸

glycerol ['glisərəul] n. 甘油

beta oxidation β-氧化作用

chemolithotrophy [keməli'θɔtrəfi] n. 化能自养型

inorganic compound 无机化合物

sulfur compound 含硫化合物

sulfide ['sʌlfaid] n. 硫化物

hydrogen sulfide 硫化氢

thiosulfate [θaiəu'sʌlfeit] n. 硫代硫酸盐

ferrous ['ferəs] n. 亚铁，二价铁

reducing power 还原力

electron acceptor 电子受体

nitrite ['naitrait] n. 亚硝酸盐

biogeochemical cycle 生物地化循环

acetogenesis ['æsitəu'dʒenəsis] n. 乙酸形成

nitrification [naitrəfi'keiʃən] n. 硝化作用

denitrification [di:naitrifi'keiʃən] n. 脱氮作用,反硝化作用

oxidative phosphorylation 氧化磷酸化

electron transport chain 电子传递链

ATP synthase ATP合成酶

synthase ['sinθeis] n. 合成酶

adenosine diphosphate 腺苷二磷酸