1. The Molecules of Life
Chapter 3

2. Dietary Sugars The average American consumes Lactose is milk sugar
about 45 kg of sugar (about 100 lb) per year,
mainly as sucrose and high-fructose corn syrup.
Lactose is milk sugar
Lactose intolerance is common
Inability to break down lactose in small intestine
Transit to the large intestine where bacteria use it to produce gas
Solutions
Avoid dairy products
Consume lactase pills along with food

3. Cell composition Mostly water Organic (Carbon-based) molecules
Small molecules
Fuels
Raw materials
Large molecules
Cell structure
Machinery of life
Categories:
Proteins, lipids, nucleic acids, carbohydrates

4. Carbon Chemistry - 1
Four electrons in outer shell  four groups attach to each carbon atom
Endless diversity of carbon skeletons
Carbon-carbon
Carbon – hydrogen
Carbon – other functional groups
Straight or branched chains

5. Carbon Chemistry - 2 Hydrocarbons
Contain only carbon and hydrogen atoms
Methane, ethane, propane, butane, pentane, hexane, heptane…
Straight or branched chains
Single or double or triple bonds
Fuels
Structural elements

6. Functional Groups
Other combinations of atoms that attach to a hydrocarbon chain
Hydroxyl
Carboxyl
Amino
Phosphate
Many others
Diverse compounds
Sugars
Amino acids
Nucleotides
Lipids

7. Macromolecules Giant Three types: Polymers Carbohydrates Proteins
Nucleic Acids
(Lipids)
Polymers
Long chains of smaller subunits

8. Carbohydrates Monomers: simple sugars; monosaccharides Disaccharides
simple sugars that cannot be broken down by hydrolysis into smaller sugars
Glucose
Fructose
Disaccharides
Two sugars joined together through saccharide bonds
Dehydration reaction
Sucrose – table sugar – glucose + fructose
Lactose – milk – glucose + galactose
Polysaccharides
Long chains
Starch: poly glucose; plant storage
Glycogen: poly glucose; animal storage
Cellulose: poly glucose; plant cell walls

9. Fats & Lipids - Structure
hydrophobic, unable to mix with water.
Fats: A typical fat, or triglyceride, consists of
a glycerol molecule,
joined with three fatty acid molecules,
If the carbon skeleton of a fatty acid has fewer than the maximum number of hydrogens, it is unsaturated or the maximum number of hydrogens, it is saturated.
A saturated fat has no double bonds and all three of its fatty acids saturated.
Most animal fats have a high proportion of saturated fatty acids, can easily stack, tending to be solid at room temperature, and contribute to atherosclerosis, in which lipid-containing plaques build up along the inside walls of blood vessels.
Most plant and fish oils tend to be high in unsaturated fatty acids and liquid at room temperature.
Hydrogenation
adds hydrogen,
converts unsaturated fats to saturated fats,
makes liquid fats solid at room temperature, and
creates trans fat, a type of unsaturated fat that is particularly bad for your health.

10. Steroids very different from fats in structure and function
The carbon skeleton is bent to form four fused rings.
Steroids vary in the functional groups attached to this set of rings, and these chemical variations affect their function.
Cholesterol is
a key component of cell membranes and
the “base steroid” from which your body produces other steroids, such as estrogen and testosterone.
Synthetic anabolic steroids
are variants of testosterone,
mimic some of its effects,
can cause serious physical and mental problems,
may be prescribed to treat diseases such as cancer and AIDS, and
are abused by athletes to enhance performance.
Most athletic organizations now ban the use of anabolic steroids because of their health hazards and unfairness, by providing an artificial advantage.

11. Fats and Lipids: Uses
Fats perform essential functions in the human body including
energy storage,
cushioning, and
Insulation
Lipids:
Essential parts of cell membranes
Hydrophobic: separates living things into compartments
Provide structural support for animal cells
Steroids:
Critical hormones that regulate life processes
Reproductive hormones: testosterone, estrogen
Metabolic hormones

12. Proteins - composition
Long strands of amino acids
50% of the dry weight of a cell
Perform most cellular functions
Amino acid:
Central carbon with 1 amino group (-NH2), one carboxyl group (-COOH) and one other “R” group, along with its lone hydrogen
20 common in living things: be able to name three
Joined together through peptide bonds
Another dehydration reaction – yields water

13. Proteins - Structure
Primary structure is the sequence of amino acids; many possibilities
a chain of 10 amino acids could be 2010 different sequences
Secondary structure: regular folding or twisting of the chain
Held in position by hydrogen bonds
Tertiary structure: folding this chain back on itself
More hydrogen bonds
Some proteins contain more than one chain: quaternary structure

14. Proteins - uses Enzymes: mediate the chemical reactions in a cell
Structural proteins: support the cell’s shape and size
Chaperones protect and mediate transport of other molecules

15. Protein Shape (conformation)
Depends on the sequence of amino acids
Sickle Cell Anemia
Affected by temperature and pH
Fever – some protein denaturation
Alzheimers disease;
Prions are small proteins that infect mammals and alter the folding of their own proteins
mad cow disease

16. Nucleic Acids - Composition
Polymers of nucleotides
Nucleotide
Sugar + base + phosphate
Phosphate = PO4-3
Base = Nitrogenous molecule hangs attached to the sugar-phosphate backbone
adenine (A), cytosine (C), guanine (G), and either thymine (T) (DNA) or uracil (U) (RNA)

17. Main Categories of Nucleic Acid
DNA:
sugar = deoxyribose
Bases = A,C, G and T
Usually double stranded
Found in the nucleus
Very stable; carries genes
RNA:
sugar = ribose
Bases = A, C, G and U
Usually single stranded
Found everywhere in the cell
Copied from the DNA

18. Nucleic Acids – Structure
Polynucleotide
Alternating Sugar-phosphate chain
Base hangs off the chain at the sugar molecule
Chain twists to form a helix or spiral
Structure
Primary structure: the sequence of nucleotides
Secondary structure: the spiral chain
Tertiary structure: the folding back on itself when combined with chaperone proteins: found in chromosomes

19. Nucleic Acids Uses
DNA: encodes the genome, the instructions for living things
Parts list: the sequences of all the proteins in a cell
Instruction manual for assembling and using those proteins
RNA:
Copied from the DNA for use
Makes up the protein synthesis machinery
Some viruses use RNA as their genetic material
Chromosomes
Long fibers in the cell nucleus
DNA + proteins + small RNAs
Gene: a specific stretch of DNA that programs the amino acid sequence of a polypeptide