Chapter 2 ChemistryWhat does chemistry have to do with biology?

Laws of chemistry -Laws of chemistry -govern thegovern the structure & function structure & function ofof all all livingliving thingsthings.

EXAMPLE of a chemical in the body:

This crystal is uric acid, normally found in urine. It displays double refraction under a microscope with polarized light.

All organisms are

made of matter –

In living things matter is constantly being rearranged through changes called

chemicalchemical reactionsreactions

Everything in the universe is made of matter

• Matter- anything that occupies space and has

mass.

• Mass- the quantity of matter in an object-the total number of sub-atomic particles (electrons,

protons and neutrons) in the object.

**The chemical properties of matter depend on its organization at the following levels:

Subatomic Atomic Molecular

A. The Subatomic level(inside the atom)

• Inside the Nucleus:

1. Proton- positively charged particle

2. Neutron- neutral, no electrical charge

• Outside the nucleus

3. Electron –small, negatively charged particles

The Total electrical charge of atom is zero

* Atoms are composed mostly of empty space - between nucleus and the orbiting electrons

• Electrons – high energy particles with very little mass.– move around outside the nucleus at very high

speeds in areas called orbitals.

• An orbital- is a region around the nucleus that indicates the probable location of an electron.

Isotopes• All atoms of an element have the same

# of protons.• All atoms of an element do not necessarily

have the same # of neutrons.

• Isotopes are atoms of the same element with a different # of neutrons.– The additional neutrons change the mass of the atom.– Most elements are a mixture of isotopes.

B. Atomic level- atoms of each element

1.1. ElementElement -A substance

that cannot be broken down

by chemical means. Elements

are defined by their number

of protons (Atomic Number)

Example- an atom of Hydrogen,

(H -1)Oxygen (O -8), Carbon (C-6)

*The number of electrons in the outer most energy level determine bonding properties

Elements in Living things-Elements in Living things- • Approx. 25 elements occur in living things.

• 6 elements of critical importance:

–Carbon – Hydrogen – Nitrogen Carbon – Hydrogen – Nitrogen

– – Oxygen – Phosphorous - SulfurOxygen – Phosphorous - Sulfur• “CHNOPS”

• These are found in the 4 major groups of ORGANIC ORGANIC molecules:

– Carbohydrates Carbohydrates - Lipids- Lipids

– Proteins Proteins -Nucleic Acids-Nucleic Acids

In the Human BodyNote the amounts of “CHNOPS” plus Ca

The Periodic table

Groups or “Families”Groups or “Families”• vertical columns in the periodic table

• these elements share characteristics & traits

• groups have similar configurations of the outermost electron shells of their atoms.

• Example: Group 14 is the carbon group- Each of the elements in this group has 4 electrons in its outer energy level.

• That leaves 4 empty spots for additional electrons- so they form 4 chemical bonds

C. Molecular level

1. Compound- a pure substance made up of atoms of two or more elements

**Most elements undergo chemical reactions- combine in ways that arrange their atoms so the outer electron shell is full & stable

**Compounds have specific formulas

Molecule- the simplest part of a substance that retains all of the properties of the substance and can exist in a free state

2. Chemical bonds–atoms want to form stable molecules

- Covalent BondsCovalent Bonds – some elements are more stable when sharing electrons

- Ionic BondsIonic Bonds-- some elements really want to lose or gain an electron- forming cation (+) or anions (-)

Covalent Bonds

Formed when 2 or more atoms share one or more pairs of electrons *Example- water

Forming ions

Ionic BondsForm when a positively and a negatively charged particle called IONS attract each other

These positive and negative IONS form when an atom loses or gains an electron to become “stable” and have a complete # of electrons in the outer shell Example- LiF

II. Energy transfer in Living Things

A. Definition of EnergyEnergy- the ability to do work or cause change

B.B. Free EnergyFree Energy –the energy in a system that is available for work

For example, in the cell, it is the amount of energy available to fuel cell processes.

Energy can be converted- breakfast food (chemical E) -to thermal E & mechanical E

C. C. Chemical ReactionsChemical Reactions-many complex chemical reactions occur in living things every second

• Reactant:Reactant: substances that enter a chemical reaction

• Product:Product: substances produced by chemical reactions

Example: Chemical reaction in body

Reactants & Products CO2 + H20 == H2CO3 Reactants ProductsReaction is reversible-

shows the

reaction of water and

carbon dioxide to

carbonic acid in blood

Which are the reactants & which are Which are the reactants & which are products in each reaction. Is this reaction products in each reaction. Is this reaction

reversible? Explain.reversible? Explain.

Photosynthesis:Photosynthesis:•6CO2 + 6H2O + Energy (sun) C6H12O6 +

6O2

Cellular metabolism:Cellular metabolism:C6H12O6 + 6O2 6CO2 + 6H2O + Energy

(ATP)

D. Energy for reactions

1. Activation Energy- The amount of energy needed to start a chemical reaction

2. Catalysts & Enzymes – chemical substances which are able to lower the amount of activation energy needed for a reaction.

3.3. Enzymes-Enzymes- are biological catalysts- they lower the activation Energy needed for chemical reactions in living things.

Why are enzymes so important?

Features of a catalyzed reactionFeatures of a catalyzed reaction

Lower activation E needed for reaction w/ catalyst

Enzymes and chemical reactions in the body

• Lactase is one of many hard working enzymes. It breaks up the chemical bond holding the sugar lactose together.

• What happens if you don’t have enough of this enzyme in your body?

III. Water & SolutionsIII. Water & Solutions

• A. A. PolarityPolarity–Water is a polar molecule

–Polar molecules -have an uneven uneven distribution of chargedistribution of charge, though they have a , though they have a net zero chargenet zero charge..

• Electrons in a water molecule are shared unevenly between hydrogen and oxygen

Uneven electron sharing in the covalent bond in water

http://www.ciese.org/curriculum/waterproj/images/watermolecule.jpg

Solubility of Water• The polarity of water makes it

effective at dissolving other polar substances such as sugars, ionic compounds, and some proteins.

• Water is considered the Universal Universal SolventSolvent because so many things can dissolve in it.

• (non-water soluble means it is not polar- like oil, fats & other lipids)

Hydrogen Bond

• is the force of attraction between a hydrogen molecule with a partial positive charge and another atom or molecule with a partial or full negative charge

III. C. Solutions Definitions 1. Solution- a mixture in which one or more

substances are uniformly distributed in another substance.

2. Solute – the substance dissolved in the solvent.

3. Solvent – the substance in which the solute is dissolved.

Example: salt is the solute, and water is the solvent

4. Concentration-4. Concentration- the measurement of the amount of solute in a fixed amount of solution.

Example- a 5 % sugar solution contains 5 grams of sugar + enough water to make 100 ml of solution.

**Concentration increases with amount of Dissolved solute

5. Saturated Solution- solution in which

no more solute can dissolve.

6. Aqueous Solution- water is the solvent

What aqueous solutions can you think of that are important to living things?

B. Acids & BasesB. Acids & BasesWater forms ions:

H2O H+ + OH-

The H+ then combines with another water to make H3O+Called a hydronium ionThe OH- is called a Hydroxide ion

1. Acid – Has more H+ (Hydronium ions)

2. Base – Has more OH- (Hydroxide ions)

pH scalepH scale• The pH scale

measure the amount of H+ (acid)

or OH- (base) in a solution

• A change of 1 pH unit shows a tenfold increase in H+ or H3O+ ions.

• For Example -a pH of 5 has 10 times more H+ than pH 6

What Ph is an acid? A base? What pH is Neutral?

4. Buffers- chemicals that neutralize small amounts of either acids or bases.

• If you put both an acid and a base into the same container of water, they tend to cancel out the effects of one another. • For example, if both HCl and NaOH are placed in water, the Na+ and Cl- ions combine to form NaCl (table salt), and the

H+ and OH- ions combine to form H2O (water).

• Buffers in the body are very important- you have very acidic stomach fluid and basic blood.

Buffering in the body

This figure shows the major organs that help control the blood concentrations of CO2

and HCO3-, and thus help

control the pH of the blood.Removing CO2 from the blood

helps increase the pH.Removing HCO3

- from the

blood helps lower the pH.

pH indicators

» pH test strips ( Litmus » papers) are quick and » work by color change

Indicators are usually organic compounds which change color in relation to the concentration of hydrogen ions.

Tasting acids and bases (Note: NEVER taste an unknown solution)

Acids - Vinegar and citrus solutions have a sour taste. Bases - Baking soda & unsweetened

chocolate have a bitter taste.

Sour Taste Receptors Bitter Taste Receptors

The sides of the tongue have adapted to taste sour substances. The taste buds at the back of the tongue have adapted to taste bitter substances. Other receptors are specialized for tasting sweet and salty.