1. BIOCHEMISTRY

2. Life requires ~25 elements
4 elements make up 96% of living matter:
• carbon (C) • hydrogen (H)
• oxygen (O) • nitrogen (N)
4 elements make up most of remaining 4%:
• phosphorus (P) • calcium (Ca)
• sulfur (S) • potassium (K)

3. This tendency drives chemical reactions…
Chemical reactivity
Atoms tend to
complete a partially filled valence shell or
empty a partially filled valence shell
This tendency drives chemical reactions…
and creates bonds – –

4. Bonds in Biology Weak bonds Strong bonds Hydrogen bond hydrogen bonds
H2O
Bonds in Biology
Weak bonds
hydrogen bonds
attraction between + and –
hydrophobic & hydrophilic interactions
Strong bonds
covalent bonds –
H2 (hydrogen gas)
Covalent bond

5. Covalent bonds Why strong? Forms molecules 2 atoms share electrons
both atoms hold onto electrons
stable
Forms molecules H
Oxygen – H O
H — H
H2 (hydrogen gas)
H2O (water)

6. Multiple covalent bonds
atoms can share >1 pair of electrons
double bonds
triple bonds
Very strong bonds H
H–C–H –

7. 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

8. Chemistry of Life Organic chemistry is the study of carbon compounds
C atoms are building blocks
4 stable covalent bonds
Carbon chemistry = organic chemistry
Why is it a foundational atom?
What makes it so important?
Can’t be a good building block if you only form 1 or 2 bonds. H C H H H

9. Hydrocarbons Combinations of C & H non-polar not soluble in H2O stable
hydrophobic
stable
very little attraction between molecules
methane (simplest HC)

10. Hydrocarbons can grow

11. Isomers
Molecules with same molecular formula but different structures (shapes)
different PROPERTIES and 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

12. Functional groups
parts of organic molecules that are involved in chemical reactions
give organic molecules distinct properties
 hydroxyl  amino
 carbonyl  sulfhydryl
 carboxyl  phosphate
affect reactivity
makes hydrocarbons hydrophilic
increase solubility in water

13. Viva la difference!
Basic structure of male & female hormones is identical
identical carbon skeleton
attachment of different 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.

14. Hydroxyl
–OH
alcohols
names typically end in –ol
Example = ethanol

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

16. Carboxyl –COOH C double bonded to O & single bonded to OH group acids
fatty acids
amino acids

17. Amino -NH2 compounds with NH2 = amines base amino acids
ammonia picks up H+ from solution

18. Sulfhydryl –SH S bonded to H compounds with SH = thiols
SH groups stabilize the structure of proteins

19. Phosphate –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.