Chapter 2

The Chemistry of Life

Objectives 2-1

1. Differentiate between atoms and elements.

2. Analyze how compounds are formed.

3. Distinguish between covalent bonds, ionic bonds, and hydrogen bonds.

I. Nature of Matter

A. Atoms – Smallest unit of matter that cannot be broken down by chemical means.

1. All matter consists of atoms.

2. Atoms consist of protons, neutrons and electrons.

I. Nature of Matter Cont.

a. Protons – positive charge in nucleus

b. Electrons – tiny, negative charge outside nucleus

c. Neutrons- neutral charge in nucleus

The Atom

I. Nature of Matter Cont.

B. Elements – pure substance made of one kind of atom1. Represented by symbols2. Elements differ in the number of protons.3. Isotopes – atoms of the same element with different numbers of neutrons

Periodic Table of Elements

I. Nature of Matter Cont.

C. Chemical bond – force that joins more than one atom1. Compound – Two or more elements chemically joined2. Covalent Bonds – two or more atoms share electrons

a. A molecule is held together with covalent bonds.

I. Nature of Matter Cont.

b. Electrons are grouped in different levels.

i. The outer level determines bonding.ii. The max. outer level for hydrogen and helium has two electrons.iii. The max. outer level for all other elements is eight.

Covalent bond

I. Nature of Matter Cont.

c. An atom is stable when its outer electron level is full.

d. Atoms react readily when outer electron level is not full.3. Hydrogen Bonds – weak chemical bonds between polar molecules.

I. Nature of Matter Cont.

a. Polar molecule – partially negative end and partially positive end

b. Partial positive end of one molecule is attracted to the partial negative end of another.

I. Nature of Matter Cont.

4. Ionic Bonds – attraction between positively charged ions and negatively charged ions.

I. Nature of Matter Cont.

a. Atoms that lack full outer electrons levels will donate or accept electrons to have a full outer electron level.

b. Ion – atom with an unequal number of protons and electrons.

Ionic Bond

II. Water and Solutions• Objectives

–Analyze the properties of water.

–Describe how water dissolves substances.

–Distinguish between acids and bases.

II Water and SolutionsA. Water in living things

1. Storage of energy

a. Changes in water temperature happen slowly.

b. Aids in maintaining homeostasis.

2. Cohesion and adhesion

A. Cohesion- attraction between substances of the same kind due to hydrogen bonding.

B. Adhesion- attraction between different substance due to polarity.

ex: Capillary action

Cohesion

Adhesion

B. Aqueous Solutions- one substance is evenly distributed through water.1. Polarity

a. Ionic compounds and polar molecules dissolve in water.

b. Ions become surrounded by water.c. Nonpolar molecules do

not dissolve in water.

Surface Tension

Hydrogen Bonding

Nonpolar vs. Polar

Cell Membrane

2. Acids and Basesa. Hydrogen ion (H+) –

Broken water molecule forms a positively charged ion

b. Hydroxide ion (OH-) – Broken water molecule forms a negatively charged ion c. Acid- a compound that forms hydrogen ions in water

Acids and Bases

2. Acids and bases cont.d. Base – a compound that forms hydroxide ions in water or decreases the number of hydrogen atomse. pH scale – 0 to 14

i. 0 to 7- acidicii. 7 – neutraliii. 7-14 – basiciv. Factor of 10 scale

pH Scale

III. Chemistry of Cells

2-3 Objectives• Summarize the characteristics

of organic molecules.

• Compare the structure and function of organic macromolecules.

Carbon Compounds:Most non-water matter in your

body is made of organic compounds containing carbon.

4 Classes of Organic Compounds:

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

A. Carbohydrates:1) Organic compounds made of

Carbon, Hydrogen, & Oxygen in a 1:2:1 ratio

A. Carbohydrates:2) Key source of energy

3) Found in most foods, including fruits, vegetables, and grains

A. Carbohydrates:4) Made of single sugars called

monosaccharides…2 sugars are disaccharides.

5) Starch is a carbohydrate that stores energy in plants

A. Carbohydrates:6. Glycogen is a carbohydrate

made by animals to store energy

A. Carbohydrates:7. Cellulose is an indigestible

carbohydrate that provides structural support for plants

B. Lipids:1. Mostly insoluble in water2. Include fats, phospholipids,

steroids, and waxes

B. Lipids:3. Important part of cell

membranes

4. Fats are lipids that store energy

FatsFatsa. Contain 3 fatty acids bonded

to a glycerol molecule backbone

FatsFatsb. Glycerol is a 3-carbon organic

molecule

c. A fatty acid is a long chain of carbon atoms with attached hydrogen atoms

FatsFatsd. Unsaturated fats – liquid at

room temperature. Contain double bonds.

e. Saturated Fats – Solid at room temperature. No double bonds.

Fat

C. Proteins1. Protein – large molecule formed by

linked amino acids.

2. Twenty amino acids make up all proteins.

a. Order and number of amino acids determine protein.

b. Amino acids fold and twist into a compact protein.

Hemoglobin

C. Proteins3. Importance

a. Structural

b. Enzymes- speed up chemical reactions

c. Immune system

d. Muscle contraction

Actin and Myosin

D. Nucleic Acids1. Nucleic Acid – long chain of

nucleotides, codes for genetic information.

2. Nucleotides – contains a sugar phosphate back bone and a base.

a. There are 4 bases

b. Variation on pattern and number of bases creates genetic variation.

DNA

D. Nucleic Acid3. DNA – deoxyribonucleic acid,

two strands form a double helix. Contained in chromosomes.

4. RNA – Ribonucleic acid, single or double stranded, involved in manufacture of proteins.

E. ATP1. ATP – Adenosine

Triphosphate, Energy storage molecule used by all living things.

2. Cells require ATP to function.

ATP

IV. Energy and Chemical Reactions

Objectives

Evaluate the importance of energy to living things.

Relate energy and chemical reactions.

Describe the role of enzymes in chemical reactions.

IV. Energy and Chemical Reactions

Energy- the ability to change or move matter.

Types- heat, light, mechanical, chemical,

Chemical reactions convert store or release energy.

A. Energya. Depicted by chemical equations

B. written: reactants products

i. reactant is starting material

ii. Product- newly formed substance

B. Energy in Chemical Reactions

1. Energy is absorbed or released during a chemical reaction.

2. Metabolism is the sum total of all chemical reactions.

C. Activation Energy1. Activation energy – energy

needed to begin a chemical reaction.

Activation Energy

D. Enzymes1. Enzymes – substance that

increase the speed of a chemical reaction or lower the activation energy.

a. Most are proteins.

b. Without enzymes chemical reaction would not happen quickly enough to sustain life.

Enzymes

D. EnzymesEx: CO2 + H2O H2CO3\

c. Carbonic anhydrase converts carbon dioxide and water to hydrochloric acid and back.

D. Enzymes2. Enzymes are highly specific.

a. Substrate- the substance on which an enzyme acts.

b. Active site – deep fold on enzyme at which the substrate attaches.

D. Enzymesc. Process

i. Substrate(s) attach(es) to enzymes active site changing the enzymes shape.

ii. Enzyme reduces the activation energy of the reaction

iii. Substrate leaves and enzyme returns to the starting position.

D. Enzymes

d. Factors that affect an enzymes shape affect its activity.

i. Temperature

ii. pH

Temp. affects enzymes