The Chemistry of Life

Ch. 6

• Atoms are the basic building blocks of all matter.

• Elements are the 118 fundamental units of matter that can’t be broken down into simpler substances.

• 96% of the human body is made up of Carbon, Hydrogen, Oxygen and Nitrogen.

• Elements are identified by symbols based on their name. (ex. Fe for Iron from Ferrum)

• Certain elements such as Iron and Copper, called trace elements, are found in the body in small amounts.

• Plants absorb them through their roots and animals get them from food.

• An atom has a nucleus containing protons(p+) and neutrons(n0) with a cloud of electrons(e-) held in place by the attractive force of opposite charges.

\• Electrons exist around the nucleus in regions known as energy levels which can hold a certain number of electrons.

• Ex.

1st energy level 2e-

2nd energy level 8e-

3rd energy level 18e-

4th energy level 32e-

• As atoms get larger they fill these energy levels with e- in a certain order, from lowest to highest.

• Atoms contain equal numbers of e- and p+ and therefore have no net charge.

• The properties of elements differ because of the fact that they have a different atomic #, which is the number of protons in the nucleus.

• While the # of p+ and e- are the same, the # of n0 may differ.

• Elements may have a variety of isotopes which are atoms with differing numbers of n0.

• Ex. Carbon-12 and Carbon-14

• Many isotopes are radioactive and are unstable. They are especially useful in medicine and industry.

• Most elements in nature are found combined with other elements to form compounds.

• There are two types of compounds: ionic and covalent.

• Ionic compounds are a result of an attraction between atoms that occurs when electrons are transferred. This creates more stability and a net charge or ion is created. Ex. NaCl

• Covalent compounds are formed when an attraction occurs due to the atoms sharing electrons to achieve stability.

• Ex. CO2, glucose, H2O.

• When covalent bonds form they create molecules, which are a group of atoms chemically combined and having different properties than the individual atoms.

• Ionic bonds form compounds that have different properties than the individual atoms as well. Most ionic compounds are formed when a metal transfers an electron(s) to a nonmetal so that it can achieve a more stable electron structure.

• Chemical equations show how chemicals react to form new compounds. An equation must be balanced to show that no atoms were lost or gained in the chemical reaction. Coefficients are placed in front of the compound to adjust the total number of atoms.

• Mixtures are a combination of substances in which the individual components retain their own properties.

• Ex. Dirt, blood

• Solutions are mixtures in which one or more substances (solutes) are distributed evenly in another substance (solvent).

• Ex. saltwater

• Chemical reactions occur only when conditions are right. Reactions may depend on available energy, temperature or a certain concentration of a substance dissolved in solution.

• Chemical reactions can also depend on the pH of a solution.

• The pH is a measure of how acidic or basic a solution is. A scale ranging with values from 0-14 is used to measure pH.

• An acid is a substance that forms Hydrogen ions (H+) in water.

• The pH of an acid is less than 7 and will turn blue litmus paper red.

• A base is a substance that forms Hydroxide ions (OH-) in water.

• The pH of a base is more than 7 and turns red litmus paper blue.

• Water, because of its unique properties is the most important compound in living organisms.

• Water dissolves substances and allows them to be transported to the cell.

• Water is a polar molecule even though it is covalent.

• This is because oxygen has a stronger attraction for electrons than does Hydrogen.

• The electrons are pulled closer to Oxygen as a result and leave Hydrogen with a partial positive charge.

• All objects in motion possess kinetic energy.

• Particles behave like ping pong balls and constantly collide and rebound.

• This can be observed with a microscope and pollen grains and is called Brownian motion.

• Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.

• The rate of diffusion can be affected by temperature, pressure and solution concentration.

• When the movement of molecules continues but there is no net change in concentration the solution is said to be in dynamic equilibrium

• Diffusion is one the methods that materials move in and out of the cell.

• When materials move from higher to lower concentration they are said to move with the gradient.

• Oxygen also moves into the capillaries of the lungs by diffusion.

• Carbon has four valence electrons .

• These electrons form four covalent bonds in order to become stable.

• It can form single double or triple bonds with other carbon atoms and can form a huge number of structures.

• Carbon structures that have the same chemical formula but different three dimensional structures are called isomers. Ex. Glucose and fructose.

• Carbon can form large biomolecules such as proteins.

• Cells build biomolecules by bonding small molecules together to form chains called polymers.

• Carbohydrates are biomolecules composed of carbon, hydrogen and oxygen with a ratio of about two H and one O for every C.

• The simplest type of carbohydrate is called a monosaccharide. Ex. Glucose and fructose

• Simple polymers can be formed by condensation reactions where water forms from a H and –OH from two smaller molecules.

• The opposite occurs with the addition of H2O and is called hydrolysis.

• Two monosaccharide molecules can combine to form a disaccharide, which is a two sugar carbohydrate.

• Glucose and fructose combine to form sucrose by a condensation reaction.

• The largest carbohydrate molecules are polysaccharides.

• These are composed of many monosaccharide subunits.

• Ex. Starch, glycogen and cellulose.

• Starch consists of branched chains of glucose units and is used as energy by plant cells and food reservoirs in seeds and bulbs.

• Glycogen is a highly branched polymer stored in the liver

• Cellulose is another glucose polymer that forms the cell walls of plants and gives plants structural support. Its structure looks like a chain link fence.

• Lipids are large biomolecules made mostly of carbon and Hydrogen with a small amount of Oxygen. They are insoluble, nonpolar and not attracted to water molecules (hydrophobic). Ex. Fats, oils, wax steroids.

• A fatty acid is along chain of carbon and hydrogen.

• If all the carbons are bonded to other carbons it is said to be saturated.

• If a double bond is present it is said to be unsaturated.

• Fatty acids with more than one double bond are called polyunsaturated.

• Lipids are very important for the proper functioning of organisms.

• Cells use lipids for energy storage, insulation and protective coverings.

• Proteins provide structure for tissues and organs and carry out cell metabolism.

• A protein is a large complex polymer composed of carbon , hydrogen, oxygen, nitrogen and sometimes sulfur.

• The basic building blocks of proteins are amino acids. There are about 20 common amino acids.

• These building blocks, in various combinations, make literally thousands of proteins.

• Amino acids have peptide bonds that is covalent and is formed when a water molecule is removed.

• An enzyme is a protein that changes the rate of a chemical reaction.

• Enzymes are involve in almost all metabolic processes.

• A nucleic acid is a complex biomolecule that stores celluar information in the form of a code.

• Nucleic acids are polymers made up of smaller subunits called nucleotides.

• Nucleotides are arranged in three groups: a nitrogenous base, a simple sugar and a phosphate group.

• Ex. DNA-deoxyribonucleic acid

• RNA- ribonucleic acid

• DNA is the master copy of an organisms information code.

• The info in DNA contains the instructions used to form all of an organisms enzymes and structural proteins.

• RNA is a nucleic acid that forms a copy of DNA used in making proteins.