Chemistry in Biology

Chemistry in Biology

Atoms, Elements, Compounds

Atoms are the building blocks of matter.The nucleus is at the center of the atom.

Positively charged particles called protons and particles with no charge called neutrons are located in the nucleus.

Electrons with negative charges are located outside the nucleus.

Atoms contain an equal amount of protons and electrons and have a total charge of zero.

ElementsAn element is a substance that cannot be broken

down by physical or chemical means.

Elements are organized in a periodic table based

on the arrangement of their electrons.

The four most common elements in living things

are Carbon, Hydrogen, Oxygen and Nitrogen.

Isotopes, Radioactive Isotopes

Atoms of the same element that have different numbers of neutrons are called isotopes.

If an atom is unstable, the nucleus can decay and give off radiation – these are called radioactive isotopes.

Carbon-14 is a radioactive isotope that is found in all living things. Scientists can determine how old an object is by determining how much Carbon 14 is in the object.

Compounds

A compound is a pure substance formed

when two or more different elements

combine. Compounds can not be broken

down by physical means.

Water is the compound H2O.

Table salt is the compound NaCl.

Hydrocarbons are compounds made of Carbon and Hydrogen.

Methane CH4 is a hydrocarbon.

Chemical Bonds

Chemical bonds hold substances togetherby either sharing or donating electronsbetween atoms.

Covalent bonds form when electrons areshared between atoms.

A molecule is a compound held together bycovalent bonds.

Covalent Bonds

Sometimes atoms will form more than one

covalent bond between their electrons,

double or triple bonds.

Ions

Ions form when atoms gain or lose electrons.

Some ions are positively charged Na+ and someions are negatively charged Cl-

Ionic BondsAn ionic bond forms through the electrical

force between oppositely charged ions.

Substances that form from ionic bonds are

called ionic compounds.

Chemical Reactions

A chemical reaction is the process by which atoms orgroups of atoms in substances are reorganized intodifferent substances.

A chemical equation shows the reactants and theproducts.

In a balanced equations, mass is conserved and coefficients show that the number of atoms of eachelement is the same before and after the reaction.

Energy of Reactions

Activation energy is the minimum amount

of energy need for reactants to form

products in a chemical reaction.

Exothermic Reaction Endothermic Reaction

Enzymes

A catalyst is a substance that lowers the

activation energy to start a reaction.

Enzymes are biological catalysts that

speed up the rate of chemical reactions in

biological processes.

Most enzymes are proteins. Temperature and pH changes can alter the shape of an enzyme and lower its activity.

Enzyme/Substrate/Product

Substrates are the substances acted

on by enzymes. They bind at the active

site.

The “lock and key” model

Water is a Polar Molecule

In water, electrons spend more time near

the oxygen nucleus than the hydrogen

nuclei. Molecules that have an unequal distribution of charges are called polar molecules.

In water, the electrical attraction between the negative oxygen side of one water molecule and the positive side of the other water molecule form hydrogen bonds.

Section 6-3 Water and Solutions

Solutions and Suspensions

A solution is a homogenous mixturebecause it has a uniform composition.

A suspension is a heterogenous mixturebecause it does not have a uniformcomposition and the particles settle out.

A colloid is also a heterogenous mixturebecause it does not have a uniformcomposition but in a colloid the particles do not settle out.

Section 6-3 Water and Solutions

Water – solvent of lifeThe polarity of water makes itan excellentsolvent.

A solution is a mixture ofsubstances that is the samethroughout.

The solvent is the substancein greater quantity in asolution.

The solute is the substancethat dissolves in the solvent.

Acids and Bases

Substances that release Hydrogen (H+) ions

when they are dissolved in water are called acids.

Substances that release Hydroxide (OH-)

ions when they are dissolved in water are

called bases.

pH

The amount of H+ or OH- ions in a solutiondetermines the strength of an acid or base.

pH measures the concentration of H+ions in a solution.

Acidic solutions have pHs lower than 7Basic solutions have pHs higher than 7A pH of 7 is neutral (distilled water)

pH and Buffers

A buffer is a mixture that can react withacids or bases to keep the pH in a particularrange.

The Building Blocks of Life

Organic chemistry is the study of organic

compounds containing carbon.

Carbon has four outer electrons and so can

form four covalent bonds with other atoms.

Macromolecules

• Macromolecules are large molecules made by joining smaller organic molecules together.

• Polymers are made of repeating units of monomers.

Section 6-4 The Building Blocks of Life

Monomer

Polymers

Carbohydrates andLipids provide structureand support, Nucleicacids store andcommunicate geneticinformation, whileProteins provide a widevariety of functions.

The four major categories of macromolecules are Carbohydrates, Lipids, Proteins and Nucleic Acids.

•Tree of Life Macromolecules

Carbohydrates

Carbohydrates contain Carbon, Hydrogen

and Oxygen.

Simple sugars like Glucose are called monosaccharides.

Two simple sugars joined together are called a disaccharide. Ex: Sucrose.

Many sugars covalently connected in a chain are called a polysaccharide.

Polysaccharides: Glycogen

Cellulose

Chitin

Lipids

Lipids are made mostly of Carbon andHydrogen. The monomers are called fatty acids.

Lipids are non-polar molecules like fats andoils.

Saturated fatty acids haveno double bonds in the chain.

Unsaturated fatty acids have one or more

double bonds in the chain.

Section 6-4 The Building Blocks of Life

Phospholipids and Steroids

A special lipid called a phospholipid is

important for cell membranes.

Other lipids are called steroids

and include cholesterol and

hormones like estrogen and

testosterone.

Proteins

Proteins are chains of monomers calledamino acids held together by peptidebonds.

Proteins contain Carbon, Nitrogen,Hydrogen, Oxygen and sometimes Sulfur.

There are 20 different amino acids.

Proteins

The many shapes formed by proteins allow

proteins to provide functions ranging from

support and transport to communications,

speeding up reactions and control of cell

growth.

Proteins can form a variety of 3-dimensionalstructures.

Nucleic Acids

Nucleic Acids are made of monomers called

nucleotides.

Nucleic acids are made of Carbon, Nitrogen,

Oxygen, Phosphorus and Hydrogen.

Nucleic Acids like DNA and RNA store

genetic information.