The Chemistry of Life

The Nature of Matter

Atom: An atom is the smallest unit of matter that cannot be broken down by chemical means.

Element: An element is a pure substance made of only one kind of atom.

Chemical Bonding Compound: A compound is a substance made of the joined

atoms of two or more different elements. For example, when sodium (Na) atoms and chlorine (Cl) atoms bond, the compound sodium chloride (table salt) forms.

Molecule: A molecule is a group of atoms held together by covalent bonding.

Chemical Bonds Covalent Bond: Formed when two or more molecules SHARE

electrons.

Ion: An atom or molecule that has gained (-) or lost (+) an electron.

Ionic Bond: Occur when two ions of opposite charges interact

to form a bond.

Water Cohesion: An attraction between substances of the same kind.

Molecules at the surface of water are linked by hydrogen bonds like a crowd of people holding hands.

Surface Tension: This is caused by cohesion. It is the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area. Ex: water droplets beading up instead of spreading out.

Adhesion: An attraction between different substances. Ex: water forming a meniscus instead of being level in a graduated cylinder.

Adhesion & Cohesion of Water

The Chemistry of Cells

Most matter in your body that is not water is made up of organic compounds. Organic compounds contain carbon atoms that are covalently bonded to other elements – typically hydrogen, oxygen, and other carbon atoms.

The 4 primary elements of your body are Hydrogen, which forms 1 bond, Oxygen, which forms 2 bonds, Nitrogen, which forms 3 bonds, and Carbon, which forms 4 bonds.

You can remember this by remembering H - 1

O - 2

N - 3

K - 4

Classes of Organic Compounds

Four principal classes of organic compounds are found in living things:

Carbohydrates

Lipids

Proteins

Nucleic Acids

Without these compounds, cells could not function.

Carbohydrates

Organic compounds made up of carbon, hydrogen, and oxygen atoms.

They are a key source of energy and found in most foods.

The building blocks of carbohydrates, or carbs, are single sugars called monosaccharides. (Ex: glucose and fructose)

Disaccharides are double sugars formed from two monosaccharides. (Ex: sucrose, a.k.a. table sugar)

Polysaccharides are large molecules made up at least 3 monosaccharides. (Ex: starch)

Lipids Organic compounds mostly insoluble (won’t dissolve) in water.

Examples include fats, phospholipids, steroids, and waxes.

Important part of the structure and function of the cell membrane.

Fats are lipids that store energy.

Saturated fatty acids all of the carbons in the chain except for the on the end are bonded to 2 hydrogen atoms. These fats are solid at room temperature.

Unsaturated fatty acids are not as straight as saturated fats and have kinks in their structure. These fats are liquid at room temperature.

Proteins

A protein is usually a large molecule formed by smaller molecules which are linked together. These smaller molecules are called amino acids.

Amino acids are the building blocks of proteins.

20 different amino acids are found in proteins.

Some proteins are enzymes and promote chemical reactions.

Other proteins have important structural functions. (Ex: collagen in skin, ligaments, tendons, and bones)

Nucleic Acids

All of your cells contain nucleic acids.

A nucleic acid is a long chain of smaller molecules called nucleotides.

A nucleotide has 3 parts: a sugar, a base, and a phosphate group.

There are 2 types of nucleic acid DNA: two strands of nucleotides that spiral

around each other. Chromosomes are made up of this material.

RNA: one strand of nucleotides or base paired nucleotides. It can also act as an enzyme promoting chemical reactions.

Adenosine Triphosphate (ATP)

This is a single nucleotide with 2 extra energy-storing phosphate groups.

When food molecules are broken down inside cells, some of the energy in the molecules is stored temporarily in ATP.

Cells need a steady supply of ATP to function.

Death is the direct result of the cessation (ending) of ATP production.

ATP is the major energy currency of cells because it powers cellular processes necessary for life.

Enzymes

Enzymes are substances that increase the speed of chemical reactions.

Most enzymes are proteins.

Enzymes are catalysts, which reduce the activation energy of a chemical reaction.

Enzymes increase the speed of a chemical reaction by lowering the activation energy of the reaction.

You can think of it like pushing a car up a hill. Once you get the car to the top of the hill, it will roll down (the chemical reaction). It would take a while if done alone, but if Arnold Schwarzenegger (the enzyme) came and helped push, the effort (activation energy) required would be much lower and the task (the reaction) would be completed much faster!

Enzymes & Activation Energy

The energy required for a chemical reaction to proceed is much lower when an enzyme is present!

Enzyme Specificity (pickiness) A substance on which an enzyme acts during a chemical reaction is called a substrate. Enzymes

can only act on specific substrates.

An enzyme’s shape determines its activity. Typically, an enzyme is a large protein with one or more deep folds on its surface. These folds form pockets called active sites and this is where the chemical reaction takes place.

Steps to Enzymatic Action: A substrate attaches itself to an enzyme’s active site.

The enzyme reduces the activation energy of the reaction.

The enzyme is not changed by the reaction.

Enzyme Action

Factors Affecting Enzyme Function

Anything that can change the shape of an enzyme can affect the enzyme’s activity.

Enzymes usually operate most efficiently within a certain range of temperatures and pH values.

How much enzyme and how much substrate is present will affect an enzymes function. If there is very little of either then the chemical reactions will not proceed much quicker than normal.