CHAPTER 2

CHEMISTRY OF LIFE

Level of organisation

ATOM MOLECULE ELEMENT

COMPOUND SOLUTION

Water

Only 4 of the 90 elements make up more than 96% of the mass of the

human body. They are:

Carbon (C)

Hydrogen (H)

Oxygen (O)

Nitrogen (N)

Mixture and Solutions

When elements combine to form a compound, the elements no longer have their original properties.

A mixture is a combination of substance in which the individual components retain their properties. Ex: Sand and sugar

A solution is mixture in which one or more substances (solute) are distributed evenly in another substance (solvent). Ex: Kool-aid

*The concentration of solute is important to organisms

A suspension is a mixture of water and nondissolved materials

Acids and BasesAcids and Bases

Chemical reactions can occur only when conditions are right; they depend on the pH of the environment

pH is a measure of how acid or basic (alkaline) a solution is

A scale with values ranging from 0 to 14 is used to measure pH

ACID is any substance that forms hydrogen ions (H+) in water. Ex: HCl (H+) and (Cl-) has a pH of below 7

BASE is any substance that forms hydroxide ions (OH-) in water.

Ex: NaOH (Na+) & (OH-) has a pH above 7

H+ OH-

Buffers=dissolved compounds that control pH in the body

( HOMEOSTASIS)Buffers are weak acids or bases that

can react with strong acids or bases to prevent sharp sudden changes in pH.

Importance of Acids and Bases to Biological Systems

Chemical reactions in organisms depend on the pH of the environment

Ex: Pepsidase is an enzyme that works best in the acidic human stomach

Certain organisms require a certain pH environment for optimum (best) growth

Organism A__________

Organism B ---------------

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

4.5 10.5

0-8 6.5-14

Life Substances

1.Organic compounds are derived from living things and contain Carbon, must have Carbon and Hydrogen to be organic

2.Inorganic compounds are derived from nonliving things (ex: Water, Carbon Dioxide)

Carbon compounds: easily form 4 covalent bonds to create chains , rings, or branches

•Polymerization: when a large compound (polymer) is produced from smaller compounds (monomers) as the smaller compounds are joined together. •Macromolecules: large polymers

Condensation Reaction (dehydration synthesis) to make

or build, water is produced Hydrolysis to split, water is

added

1.Carbohydrates2. Lipids

3. Proteins4.Nucleic Acids

Carbohydrates

Composed of C (Carbon), Hydrogen (H), Oxygen (O) in

approximate ratio 1:2:1

Monosaccharide: single (simple) sugar Molecular formula for all 3: C6H12O6

GLUCOSE-Produced by plants through photosynthesis

FRUCTOSE-found in fruits GALACTOSE-found in milk

Disaccharides formed by 2 sugarsC12H22O11

Sucrose = glucose + FructoseMaltose = glucose + GlucoseLactose = glucose + Galactose

Polysaccharides formed by more than 2 sugars

Starch-storage for plants Glycogen-storage for

animals (liver) Cellulose-cell wall of plants

Chitin=cell wall of fungi

What makes them different from one another is the arrangement of the individual atoms (structural formulas)

Isomers – compounds that differ in structure but nor in molecular composition

Synthesis of Dissachharides

Glucose Fructose Sucrose Water

+ +

C6H12O6 C6H12O6C12H22O6 H2O

++

* Dehydration synthesis-water is squeezed out

+ +

Hydrolysis of Disaccharide

WaterSucrose FructoseGlucose

C6H12O6 C6H12O6C12H22O6 H2O

+

+

+

+

+

+

* Hydrolysis-water is added

Lipids: Fatty Compounds

Made of C, H, O w/ a greater # in C:H atoms and a smaller # of O atoms than carbohydrates (No uniform Ratio)Ex: fats, oils, waxes (do Not dissolve

in water)

Many common lipids are constructed of a unit of:

•Glycerol (3-Carbon Alcohol) combined by dehydration synthesis

•3 fatty acids-hydrocarbon chain with an Carboxyl Group -COOH

3 fatty acids-hydrocarbon chain with an Carboxyl Group -COOH

Hydrophilic End (water loving-carboxyl end that is polar)

Hydrophobic End (water fearing-hydrocarbon end that is nonpolar)

Functions: forms much of cell membrane to serve as a barrier between the inside and outside of the cell – energy storage for cells

Ex: waxes, triglycerides

Proteins: Organic Compounds made of C, H, O, N

Polymer made of amino acids (monomers); organisms have thousands of proteins

Amino Acids: 20 different kinds that form proteins-has 5 Groups:

a) Central C atomb) Single H atomc) Carboxyl Group (COOH)

d) Amine Group (NH2)

e) R Group (repeating CH2 + CH2 of different lengths)

Dipeptide: 2 amino acids bound together covalently by condensation reaction (a molecule of H2O is lost)-

held together by peptide bondsa) c)

e)d)

b)

Amino acid Amino acid

Dipeptide

Water

Polypeptide:

A long chain of amino acids held together by peptide bonds

Ex of Proteins: Insulin (hormone), hemoglobin, and enzymes

Nucleic Acids: complex organic Nucleic Acids: complex organic molecules that molecules that store important store important

informationinformation in the cell in the cell

2 important types of nucleic acids are 2 important types of nucleic acids are DNADNA and and RNARNA

1.1.DNA (deoxyribonucleic acid): DNA (deoxyribonucleic acid): stores stores essential info for almostessential info for almost all cell all cell activities-including activities-including cell divisioncell division

2.2.RNA (ribonucleic acid): RNA (ribonucleic acid): stores and stores and transfers info for proteinstransfers info for proteins

Nucleotides: monomers that make up both DNA & RNA-made up of 3 main

components:

Phosphate Group

Five-Carbon Sugar

Nitrogen Base (ring)