Immunology

Scientists stumble upon a model to study a lethal complication

More and more hospitalized patients with sepsis are being diagnosed with a deadly complication characterized by high levels of inflammation. A team of Yale researchers has uncovered clues to the cause of this complication—which ...

Cancer

Cancer cells' plasticity makes them harder to stop

When metastatic cancer cells need to avoid a threat, they simply reprogram themselves. Rice University scientists are beginning to get a handle on how they survive hostile environments.

Genetics

Two independent mechanisms are involved in tuberous sclerosis

The current idea about how tuberous sclerosis occurs places mTORC1, a protein complex that regulates cell metabolism, as the major driving force behind the disease. But according to a new study published in the Proceedings ...

Medical research

Fasting ramps up human metabolism, study shows

Fasting may help people lose weight, but new research suggests going without food may also boost human metabolic activity, generate antioxidants, and help reverse some effects of aging. Scientists at the Okinawa Institute ...

Immunology

Energizing the immune system to eat cancer

Immune cells called macrophages are supposed to serve and protect, but cancer has found ways to put them to sleep. Now researchers at the Abramson Cancer Center of the University of Pennsylvania say they've identified how ...

page 1 from 23

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.

This text uses material from Wikipedia, licensed under CC BY-SA