Chapter 3: Water, Carbohydrates,

Lipids, Proteins, Nucleic Acids

Dr. Amy Rogers

• Human body is 2/3 water by weight • On Earth, life first appeared in water

What is it about WATER???

Properties of Water

n Solvent: Polar & charged solutes

n Specific Heat: great insulator

n Temperature/Density: Ice floats!

n Surface Tension: Walk on water? Sure!

Water as a Solvent

Hydrophilic: “water loving”

interacts with water

Polar or Ionic Solute

Hydrophobic molecules

• Do not dissolve in water • Crucial for maintaining biological “compartments”

Water is a good insulator

Imagine you are winter camping in the Rocky Mountains. To keep warm, you can take one of these items into your

sleeping bag with you:

Water bottle heated to 100oF vs.

Aluminum brick heated to 100oF

Specific Heat:

The amount of energy required to raise the temperature of a substance by 1o C

Heat buffering by water maintains (relatively) stable

temperatures on earth and in animals’ bodies

The important macromolecules for cells:

n  Carbohydrates

n  Lipids n  Proteins

n  Nucleic Acids

Polymers

n  Many complex organic molecules are polymers

(large molecules made up of

many similar or identical subunits)

Simple Carbohydrates

n  Monosaccharides (Simple sugars) e.g, glucose, fructose, deoxyribose

• Note ending of sugar names is usually -ose

Complex Carbohydrates

n  Polysaccharides e.g., starch, glycogen, cellulose, chitin

n Polymers of thousands of sugars

n Bread, cereal, pasta

Complex Carbohydrates: Starch

• Massive polymer of glucose • Energy storage in many plants

• When energy is needed, starch is degraded back into glucose

Complex Carbohydrates: Glycogen

• Main form of carbohydrate storage in animals

• In humans, kept primarily in liver and muscle

Complex Carbohydrates: Cellulose

• Rigid

• Cell walls of many organisms:

• Trees, cotton, grasses…

• Easily the most abundant carbohydrate on earth!

• Mammals cannot digest it

• Major source of insoluble fiber

Lipids n  Fats, oils, cholesterol, hormones n  Made of C, H, O like carbohydrates but

relatively much more H than O

n Relatively insoluble in water

n  Not all are polymers

Lipids

n  Uses: n  Long-term energy storage n  Insulation n  Hormones n  Separation of biological compartments

(membranes)

Energy Storage

n  Carbohydrates & Lipids are both used by cells to store energy for future use

Lipids (fats)

n  All membranes are made of lipids n  Cell membrane, nuclear membrane

Proteins: Workers of the world, united

n  Need something done? Call a protein!

n About ½ dry weight of a cell

n  Enzymes: mediate chemical reactions n  Messengers, transporters, defenders, movers, structure

builders, poisons, communicators…….

Proteins are Polymers

n  Proteins are long chains of smaller subunits called amino acids

n  Like letters of the alphabet, they can be strung together in any sequence or length to create a spectacular variety of proteins

Amino Acids make polypeptides

Proteins: 3D is key

n  A long straight chain of amino acids is energetically unstable: BONDS will form

n  Polypeptides fold into a specific conformation

n  Unique 3D shape of proteins is CRUCIAL for their function

Nucleotides & Nucleic Acids

n  Subunit: nucleotides n  Nucleotide ATP is vital energy carrier n  You will learn much more about ATP soon

Phosphate group

Sugar “Base”: A, T, G, C

Nucleotides & Nucleic Acids

n  Nucleotide polymer: Nucleic acid (DNA, RNA)

n  Information molecule n  Blueprint for protein manufacture n  Cell’s “hard drive”