Water, pH and Biological Molecules
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Water, pH and Biological Molecules. What’s so special about water?. It’s a great solvent. It hold’s tons of heat. It has high surface tension. Its less dense as a solid than a liquid. Water as a Solvent. Dissolving table salt (sodium chloride).

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What’s so special about water?

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Water, pH and Biological Molecules

What’s so special about water?

It’s a great solvent.

It hold’s tons of heat.

It has high surface tension.

Its less dense as a solid than a liquid.

Water as a Solvent

Dissolving table salt (sodium chloride)

This means that ice forms an insulating blanket over water.

Water Is Lighter as Solid than as a Liquid

Water Has High Surface Tension

The attraction of one water molecule for another also accounts for ability to hold huge amounts of heat.

pH is a Big Deal

pH is a measure of proton (hydrogen ion or H+) concentration .

Low pH = lots of H+s, high pH = few H+s.

In biology, keeping H+ levels within a narrow range is critically important.

An acid produces H+

A base absorbs H+

Acids and Bases

Carbon’s Cool

Carbon is the central atom of life.

Because carbon contains 4 electrons in its outer shell, it can pair in many ways with many different atoms in an “attempt” to fill its outer shell.


amino acids


Carbon is the Central Atom of Life.

Some Useful Nomenclature

In Biology, Shape Matters

Its not just chemical formula, it’s the shape of the molecule that lets it do its “job”.

Never forget the axiom – structure dictates function.

Some biological molecules.

Ah, That Smell!

Once again, shape matters. It’s the good fit between odorant and receptor molecule that lets us detect aromas.

Four Major Classes of Biological Molecules

Molecules of Life

How do you build a cell?

Start with water, add lots of small carbon-containing molecules and …….

Rules of the Game

Macromolecules are built by linking a set of building blocks (monomers) together into long chains (a polymer).

Each hexagon is this figure is a monomeric building block linked together to form a polymer.

Macromolecules Are Built By Linking a Set Of Building Blocks (Monomers) Together Into Long Chains (A Polymer).

Glucose: A Simple Carbohydrate Used For Energy Production and as a Building Block For Complex Carbohydrates

Linking Simple Sugars – the First Step to a Polymer and the Last Step to Some Familiar Compounds

Some Familiar and Important Complex Carbohydrates

Note the way complex macromolecule are built by linking simple repeating units.

Carbohydrates are Central Players in Energy Production and Storage




Lipids are Hydrophobic Molecules That Exist In Three Primary Forms

Space-filling model of a fat

A fatty acid

Fats Are Made By Linking Fatty Acid Chains to Glycerol, a Three Carbon Molecule

Fats are Used in Energy Storage and Production

Where are the double bonds?

The Degree Of Saturation In A Fat Affects Its Physical And Nutritional Properties



Where are the double bonds?


The Degree Of Saturation In A Fat Affects Its Physical And Nutritional Properties

Note the four ring structure common to all sterols.

Sterols Are Part of Cellular Membranes and Act as Hormones

Sterols As Hormones

Estrogen, testosterone, progesterone, and corticosteriods (cortisol) are all steroid hormones.

A heavily muscled Linford Christie who was disqualified from international competition after testing positive for a banned steroid.

Sterols As Hormones

“Designer steroids” are major sporting news where they have been used illegally in track and field, baseball, football and countless other sports.

Phospholipids are Building Blocks of Cellular Membranes

The hydrophilic head group and hydrophobic tails are the keys to phospholipid function.

Hydrophilic Head Group And Hydrophobic Tails Are The Keys To Phospholipid Function

Phospholipids have a Jekyll and Hyde personality.

Phospholipids Form Biological Membranes


Proteins are THE key elements of life. Forget DNA, proteins rule.

Remember the principle - structure determines function.

Since proteins are the key players of the cell, it follows that protein structure determines cell function.

Some of the Diverse Functions of Proteins

Strands of the Protein Keratin Create Hair

Proteins are Linear Chains of Linked Amino Acids

A Common Thread and a Unique Identity

Peptide bonds

Amino Acids, Peptide Bonds, Polypeptides, Protein

Proteins are linear chains of 20 different building blocks called amino acids.

Amino acids are linked by peptide bonds – a form of covalent bond.

Proteins are Folded Structures Whose Shape (and therefore function) Depends on Amino Acid Sequence

Nucleic Acids

There are two kinds of nucleic acids, DNA and RNA. Both are involved in the storage and flow of information from gene to gene product.


Nucleotides are DNA and RNA Building Blocks

ATP, the cell’s primary energy currency.

Nucleotides are Important in Their Own Right

Nucleotides fuel the cell and coordinate its metabolism.

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