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”