1. Biochemical Reactions that Make and Break Molecules

2. Carbon—The Backbone of Biological Molecules
Although cells are 70–95% water, the rest consists mostly of carbon-based compounds.
Carbon is unparalleled in its ability to form large, complex, and diverse molecules.
Proteins, DNA, carbohydrates, and other molecules that distinguish living matter are all composed of carbon compounds.

3. Organic Molecules All organic molecules contain carbon.
Carbon has four valence electrons and forms four covalent bonds.
Functional groups are the parts of organic molecules usually involved in chemical reactions and give molecules unique properties.

4. Macromolecules These are large organic molecules
The four main types of macromolecules are
Carbohydrates – sugars and starches
Lipids – fats and waxes
Proteins
Nucleic acids – DNA and RNA
Most macromolecules are also polymers

5. Polymers and Monomers “poly” means “many”, “mono” means “one”
“mer” means “unit”
Each single unit is a monomer
So a polymer is a large molecule made of many monomers
For example:
sugar + sugar  starch
amino acid + amino acid  protein

6. Five Major Biochemical Reactions
Condensation
Hydrolysis
Neutralization
Redox
Phosphorylation

7. 1. Condensation Reactions
A condensation reaction builds polymers by joining monomers
When a bond is formed between two monomers a water molecule is also produced
This is also called a dehydration synthesis
Example:
Condensation of Sucrose +
+ H20

8. 2. Hydrolysis Reactions
A hydrolysis reaction breaks a polymer into monomers
Water is added to a molecule which causes a bond to break
The H+ is added to one monomer and the OH- to the other monomer
Example:
Hydrolysis of Sucrose

9. LE 5-2
Short polymer
Unlinked monomer
Dehydration removes a water
molecule, forming a new bond
Longer polymer
Dehydration reaction in the synthesis of a polymer
Review: making large molecules involves dehydration synthesis whereas breaking large molecules requires the use of water.
Why are we thirsty after eating a lot of spaghetti?
Hydrolysis adds a water
molecule, breaking a bond
Hydrolysis of a polymer

10. 3. Neutralization Reactions
A neutralization reaction occurs when acids (-COOH or H+) and bases (-OH) react to produce a salt and water.
Buffers are molecules or reactions that minimize changes in pH in a cell.
Buffers absorb excess H+ (acids) or OH- (bases)

11. 4. Redox Reactions Short form for reduction – oxidation reactions
“LEO goes GER”
Loss of Electrons is Oxidation
Gain of Electrons is Reduction
Common in metabolic reactions
Example in photosynthesis and respiration

12. 5a. Substrate-level Phosphorylation
ATP, adenosine triphosphate is the energy molecule of an organism.
Substrate-level phosphorylation is a type of chemical reaction that results in the formation and creation of ATP by the direct transfer and donation of a phosphate group to ADP from a reactive molecule.

13. 5b. Oxidative phosphorylation
Oxidative phosphorylation is a metabolic pathway that uses energy released by the oxidation of nutrients to produce ATP.

14. 5c. Photophosphorylation
Photophosphorylation is the production of ATP using the energy of sunlight.

15. ISOMERS
Just because a molecule has the same chemical formula is no reason to assume that it has the same shape or similar properties.
Isomers are compounds that have the same molecular formula but have different arrangements of atoms.
Two types of isomers:
Structural Isomers
Stereoisomers or geometric isomers

16. 1. Structural isomers – differ in connection of the atoms
LE 4-7a
1. Structural isomers – differ in connection of the atoms

17. LE 4-7b
2. Geometric isomers – a stereoisomer in which there is restricted rotation about a bond,
usually a C=C bond

18. LE 4-7c
L-isomer
D-isomer
Stereoisomers

19. Two stereoisomers of a drug may have different effects.
LE 4-8
L-Dopa (effective against
Parkinson’s disease)
D-Dopa
(biologically Inactive)
Two stereoisomers of a drug may have different effects.