knowverseWhy do water molecules stick together? How does carbon form so many different molecules? Try 10 questions on the chemistry that supports living cells.
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Carbon, hydrogen, oxygen and nitrogen are major components of biological matter. Organisms also need other elements in smaller quantities.
While many elements are essential, just four of them make up a staggering 96 percent of all living matter.
From the Knowverse course text.
Trace elements are required in small amounts. Iron is one example, and its small quantity does not make it unimportant.
Some of these are called trace elements because an organism only requires a minute quantity of them.
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Oxygen's stronger pull on shared electrons creates a partial negative charge on the oxygen side and a partial positive charge on the hydrogens.
Because the oxygen atom is much stronger, it pulls the charges closer to itself and away from the hydrogen atoms.
From the Knowverse course text.
Hydrogen bonds between neighbouring water molecules produce cohesion.
This phenomenon, where hydrogen bonds hold water substances together, is called cohesion.
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In a dehydration reaction, a new bond connects two monomers while releasing one water molecule into the surroundings.
For every single bond formed in a polymer chain, one molecule of water is released into the surrounding environment.
From the Knowverse course text.
Carbon can form four covalent bonds, allowing chains, branches and rings.
The reason carbon is such a powerful builder lies in its unique ability to form four covalent bonds with other atoms.
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Cellulose forms rigid fibers that enclose plant cells and give structural strength to plant tissues.
In plants, a polysaccharide called cellulose is the main building material for the tough walls that enclose plant cells.
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Bent unsaturated fatty acid tails cannot pack as closely as straight tails. This helps many such oils remain liquid.
Because unsaturated fats are bent, they can't pack closely enough to form a solid, which is why they stay as liquid oils.
From the Knowverse course text.
Enzymes catalyze biological reactions without being consumed. Most are proteins, although some RNA molecules also act as catalysts.
A catalyst is a chemical agent that selectively speeds up a reaction without being consumed by the reaction.
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Messenger RNA carries a copy of genetic instructions to the protein-building machinery. It does not build proteins by itself.
RNA functions in the synthesis of proteins that are coded for by the DNA.
From the Knowverse course text.
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Living organisms depend on chemical elements in very different amounts. Carbon, hydrogen, oxygen and nitrogen are major components of biological matter. Trace elements are needed in much smaller quantities, but small amounts can still matter: iron helps blood carry oxygen. The quantity needed tells us little about how essential an element is.
Water is polar because oxygen attracts the shared electrons more strongly than hydrogen does. The resulting partial charges allow neighbouring molecules to form hydrogen bonds. Their attraction produces cohesion. Carbon supplies another useful property: its four covalent bonds allow chains, branches and rings, creating varied frameworks for biological molecules.
This results in the oxygen side having a slightly negative charge, while the hydrogen side becomes slightly positive.
From the Knowverse course text.
Cells link smaller units called monomers into polymers. In the dehydration reactions described here, joining units releases water. Carbohydrates include simple sugars and larger chains with different jobs. Cellulose strengthens plant cell walls. Lipids are built differently from true polymers, and their properties depend partly on the structures of their fatty acid tails.
Bends in unsaturated fatty acid tails can prevent close packing, helping many oils remain liquid at room temperature. Proteins consist of amino acid chains folded into functional shapes. Many act as enzymes, speeding reactions without being consumed. DNA stores genetic information, while messenger RNA carries instructions used to make proteins.
A catalyst is a chemical agent that selectively speeds up a reaction without being consumed by the reaction.
From the Knowverse course text.
Sources: Chemistry of the Biosphere. Each question or step includes an excerpt from the course.
