THE CHEMISTRY OF LIFE

Review/Background Information

Elements – pure substances that cannot be broken down any further. Atom – the smallest unit of an element. Important Words

Molecule – a substance made up of more than one atom. Compound – a substance made up of two or more different elements. Important Words

Ion – an atom that has a different number or electrons (and thus has a charge). Isotope – an atom that has a different number of neutrons. Important Words

Covalent Bond – a molecule where atoms share electrons. Ionic Bond – a compound where atoms transfer electrons. Important Words

The Atom “Parts” of the atom Electron (- charge) Proton (+ charge) Neutron (0 charge)

The basic structure of an atom

The Nucleus Central core Consists of protons and neutrons Contains most of the mass of the atom

The Protons Positively charged IN the nucleus Weigh 1 dalton

The Neutrons Are neutral (no charge) In the nucleus Weigh 1 dalton

The Electrons Negatively charged Weigh 1/2000 dalton (super tiny!) little or no mass Travel at very high speeds at various distances (energy levels) from the nucleus

Atomic Number - the # of protons Atomic Mass – the # of protons + Neutrons

Energy Levels Atoms have energy levels The 1 st level holds 2 electrons The next 6 levels hold 8 electrons (octet rule)

There are more than 100 elements (92 naturally occurring) The Periodic Table

Common Elements in Biology CalciumCa CarbonC ChlorineCl CopperCu FluorineF HydrogenH IodineI IronFe MagnesiumMg PhosphorusP NitrogenN OxygenO PotassiumK SiliconSi SodiumNa SulfurS TinSn ZincZn

The most frequently occurring elements in living things are: Oxygen (65%) Carbon (19%) hydrogen (10%) Nitrogen (3%)

Other important elements Sulfur Calcium Phosphorous Iron sodium

Sulfur Can be found in some amino acids.

Phosphorous A component of ATPForms DNA

Calcium Cell structure in prokaryotes and plants Necessary for healthy bones Involved in the transmission of nerve messages

Iron Helps form chlorophyll in plants Makes up hemoglobin (helps oxygen transport in red blood cells)

Sodium Can help in photosynthesis Helps transport glucose across the membrane

Water

Water is Important to Life! Water covers ¾ of the Earth. Water covers ¾ of the Earth. It is the most abundant compound in living things. It is the most abundant compound in living things. It is essential to life! It is essential to life!

What makes water special? Water is POLAR – the oxygen atom attracts more of the electrons than the hydrogen atoms do. Water is POLAR – the oxygen atom attracts more of the electrons than the hydrogen atoms do.

POLARITY

The structure of the water molecule Covalent bond The nucleus of oxygen is larger and has a greater charge (+8) than the hydrogen nucleus (+1). The electrons that are shared are found “closer” to the oxygen nucleus. This creates a polar molecule – the oxygen side is lightly negative and the hydrogen side is slightly positive.

This polarity results in hydrogen bonds Weak bond between the H of one molecule and the C of another molecule.

Hydrogen bonds Because of the bonds, water has some unique properties! Water “mini-lab”

Properties of Water 1. Cohesive properties 2. Thermal properties 3. Solvent properties

Cohesive properties Cohesion - Water molecules Sticking together

Cohesive properties The way plants transport water through their tissues is called transpiration and depends on the cohesive nature of water.

Thermal properties Water has a high specific heat capacity (the amount of heat required to change a substance’s temperature).

Thermal properties A body of water is thermostable. Water maintains its temperature relatively well and has less variation in temperature than air and land.

Thermal properties Water acts as a coolant. It absorbs heat before it evaporates and in doing so reduces body temperature. Heat from chemical reactions can be removed, to protect enzymes. Blood can carry heat to cold parts of the body.

Solvent properties Because water is polar, it is strongly attracted to ions. This has the effect of isolating one ion from another (which is commonly known as solubility). Dissolving Salt

Water is the solvent of blood, tissue fluid and cytoplasm. It allows the transport of soluble minerals, carbohydrates, amino acids, etc. that organisms need to survive.

Other unique things about water Water expands as it freezes Water expands as it freezes (ice floats) The universal solvent (lots of things can dissolve in it) The universal solvent (lots of things can dissolve in it) Adhesive Adhesive Part of biogeochemical cycles Part of biogeochemical cycles Essential to life Essential to life