1. Carbon and the Molecular Diversity of Life
Chapter 04

2. Why study Carbon? All of life is built on carbon Cells ~72% H2O
~25% carbon compounds
carbohydrates
lipids
proteins
nucleic acids
~3% salts
Na, Cl, K…
Why do we study carbon -- is it the most abundant element in living organisms?
H & O most abundant
C is the next most abundant

3. Carbon: The Backbone of Life
Carbon enters the biosphere through the action of plants, which use solar energy to transform atmospheric CO2 into the molecules of life. These molecules are passed along to animals that feed on plants.

4. What type of compounds are considered organic?

5. Organic Chemistry
The branch of chemistry that specializes in the study of carbon compounds.

6. What 5 atoms are most commonly combine with carbon to form organic molecules?

7. Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur
CHNOPS
Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur

8. Carbon
What are the key properties of carbon that make it a good choice for life?

9. It has four valence electrons
Properties of Carbon
It has four valence electrons

10. Properties of Carbon It can form up to 4 covalent bonds
These can be single, double, or triple covalent bonds

11. Properties of Carbon It likes to bond with itself, unlike most atoms
Thus it can form large molecules
These molecules can be chains, branches, or ring-shaped

12. Variations in Carbon Skeletons
How can you create variations in carbon skeletons?
Change the length of the carbon skeleton.
The skeleton may be straight, branched, or arranged in closed rings
Alter the number and location of double bonds.
Change the elements or groups with which carbon bonds.

13. Diversity of Molecules
Substitute other atoms or groups around the carbon
ethane vs. ethanol
H replaced by an hydroxyl group (–OH)
nonpolar vs. polar
gas vs. liquid
biological effects!
ethane (C2H6)
ethanol (C2H5OH)

14. Hydrocarbons Combinations of C & H only non-polar
not soluble in H2O
Hydrophobic
Can undergo reactions that release a relatively large amount of energy
methane (simplest HC)

15. Isomers 6 carbons 6 carbons 6 carbons
Molecules with same molecular formula but different structures (shapes)
different chemical properties
different biological functions
Same formula but different structurally & therefore different functionally. Molecular shape determines biological properties.
Ex. Isomers may be ineffective as medicines
6 carbons
6 carbons
6 carbons

16. Types of Isomers

17. Structural Isomer

18. Geometric Isomer

19. Enantiomer or Stereoisomer

20. Form Affects Function stereoisomers
Structural differences create important functional significance
amino acid alanine
L-alanine used in proteins
but not D-alanine
medicines
L-version active
but not D-version
sometimes with tragic results…
stereoisomers

21. Form Affects Function Thalidomide
prescribed to pregnant women in 50s & 60s
reduced morning sickness, but…
stereoisomer caused severe birth defects

22. Chemical Groups
There are SEVEN chemical groups most important in biology
Hydroxyl
Carbonyl
Carboxyl
Amino
Sulfhydryl
Phosphate
Methyl
6 of the 7 chemical groups are considered functional groups
Methyl group is NOT a functional group because it does not participate in chemical reactions, instead it acts as a recognizable tag on biological molecules

24. Functional Groups
parts of organic molecules that are involved in chemical reactions
give organic molecules distinctive properties
 hydroxyl  amino
 carbonyl  sulfhydryl
 carboxyl  phosphate
Affect reactivity
makes hydrocarbons hydrophilic
increase solubility in water

25. Viva la difference!
Basic structure of male & female hormones is identical
identical carbon skeleton
attachment of different chemical / functional groups
interact with different targets in the body
different effects
For example the male and female hormones, testosterone and estradiol, differ from each other only by the attachment of different functional groups to an identical carbon skeleton.

26. Hydroxyl –OH organic compounds with OH = alcohols
names typically end in -ol
ethanol

28. Carbonyl C=O if C=O at end molecule = aldehyde
O double bonded to C
if C=O at end molecule = aldehyde
if C=O in middle of molecule = ketone

30. Carboxyl compounds with COOH = acids –COOH fatty acids amino acids
C double bonded to O & single bonded to OH group
compounds with COOH = acids
fatty acids
amino acids

31. Carboxyl Group How did it get its name?
COOH - This group consists of a carbon atom that is bonded to both a carbonyl and a hydroxyl group.
Why is this group acidic?
It donates H+
Compounds with this group are called carboxylic acids

33. Amino compounds with NH2 = amines amino acids NH2 acts as base
N attached to 2 H
compounds with NH2 = amines
amino acids
NH2 acts as base
ammonia picks up H+ from solution

35. Sulfhydryl compounds with SH = thiols
S bonded to H
compounds with SH = thiols
SH groups help stabilize protein structure through disulfide bridges

36. Disulfide Bridge

38. Phosphate connects to C through an O
–PO4
P bound to 4 O
connects to C through an O
lots of O = lots of negative charge
highly reactive
transfers energy between organic molecules
ATP, GTP, etc.