The Chemistry of Life.

You know about atoms and molecules from Chemistry.

But there’s nothing ALIVE about chemistry.

It’s just chemicals in a beaker.

So what’s so special about the molecules of life?

It’s a case of emergent properties.

That is, as biological molecules come together and interact, new and surprising properties

emerge that you wouldn’t predict.

You can think of biology in terms of a structural hierarchy.

Atoms - molecules - cells - tissues - organs - pretty soon you have a multicellular organism

with a metabolism.

Let’s start with atoms.

Especially CHNOPS.

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur.

These are the elements that make up 98% of living matter on earth.

We can study the behavior of these individual atoms, but things get more interesting when

these atoms interact.

Bonds are formed and broken.

We see the emergence of chemical behavior.

Some of these atoms stay bonded together, forming biological molecules.

There are 4 main kinds of biological molecules:

Proteins, Carbohydrate, Lipids, and Nucleic Acids.

Proteins are polymers of amino acids.

That is, amino acids strung together to form a chain.

These strings of amino acids fold into 3 dimensional shapes that do most of the work of life.

With proteins, and all biological molecules, the key to remember is that the 3D structure

determines the function.

Think of how a key fits into a lock.

The shapes have to be just right for the key and the lock to do their jobs.

The jobs of proteins include structure, like collagen, enzyme catalysts that control the

rate of reactions, signalling, like some hormones, immune function, like antibodies and antibody

receptors...I could go on...all day.

Carbs (carbohydrates) are sugars and polymers of sugars.

These are used for energy, and to build biological structures.

Lipids are nonpolar molecules, like fats, oils, and phospholipids.

These are important for energy storage, for cushioning, and for structures like cell membranes.

Nucleic Acids include DNA and RNA.

These store genetic information.

It’s important to note these are all carbon-based molecules.

This is why we say we are carbon-based lifeforms.

The skeletons of biological molecules are made up of carbon atoms, covalently bonded

together in very stable structures.

Hanging off the outside of the molecules are functional groups - small chemical species

like OH or CH3.

Think of the carbon skeleton giving biological molecules their general 3D shape, and the

functional groups like flags hanging off, participating in chemical reactions.

We see another level of complexity emerge when these biological molecules interact with

each other.

We get enzymes controlling reaction rates.

We get DNA replication, and genetics.

We get cells.

And within cells, we have an incredibly diverse set of chemical reactions that are controlled

and run at just the right rates to keep us all alive.

That’s what biochemistry is.

The building blocks of Life Itself.

Our new Biology series will cover all of these topics in more depth.

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