Related topics: genes · protein · cells · amino acids · diabetes

New understanding of the inner world of lysosomes

Researchers at Duke-NUS Medical School and colleagues in Singapore have identified a protein that transports degraded membrane lipids out of lysosomes, cellular organelles that are the breakdown factories of cells. The findings, ...

Did life get its start in micaceous clay?

In mythologies and origin stories around the world, various cultures and religions point to clay as the vessel of life, the primordial material that creator gods imbued with a self-sustaining existence. Nowadays we have biology ...

Mysterious soil virus gene seen for first time

In every handful of soil, there are billions of bacteria, fungi, and viruses, all working to sustain the cycle of life. Understanding how these microorganisms interact with one another helps scientists analyze soil health, ...

Team investigates sex-determination mechanisms in birds

Scientists have known that sex-determination in vertebrates happens in the germ cells, a body's reproductive cells, and the somatic cells, the cells that are not reproductive cells. Yet they have not fully understood the ...

Bird neurons use three times less glucose than mammalian neurons

Birds have impressive cognitive abilities and show a high level of intelligence. Compared to mammals of about the same size, the brains of birds also contain many more neurons. Now a new study reported in Current Biology ...

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Metabolism

Metabolism is the set of chemical reactions that occur in living organisms to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories. Catabolism breaks down organic matter, for example to harvest energy in cellular respiration. Anabolism, on the other hand, uses energy to construct components of cells such as proteins and nucleic acids.

The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed into another by a sequence of enzymes. Enzymes are crucial to metabolism because they allow organisms to drive desirable but thermodynamically unfavorable reactions by coupling them to favorable ones, and because they act as catalysts to allow these reactions to proceed quickly and efficiently. Enzymes also allow the regulation of metabolic pathways in response to changes in the cell's environment or signals from other cells.

The metabolism of an organism determines which substances it will find nutritious and which it will find poisonous. For example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals. The speed of metabolism, the metabolic rate, also influences how much food an organism will require.

A striking feature of metabolism is the similarity of the basic metabolic pathways between even vastly different species. For example, the set of carboxylic acids that are best known as the intermediates in the citric acid cycle are present in all organisms, being found in species as diverse as the unicellular bacteria Escherichia coli and huge multicellular organisms like elephants. These striking similarities in metabolism are most likely the result of the high efficiency of these pathways, and of their early appearance in evolutionary history.

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