“…beneath the clothes, we find a man... and beneath the man we find... his... nucleus.”-Nacho Libre Reference Text - Modern Biology Chapter / pgs

Modern Biology pgs

 The chemistry of living things involves the study of solutions

The chemical reactions of life occur mostly in aqueous solutions! solution A solution is a mixture in which one or more substances are uniformly mixed with another.  Solute:  Solute: the substance dissolved in the solution.  Solvent:  Solvent: The substance in which the solute is dissolved.

 Aqueous Solution: ◦ water is the solvent ◦ Very important to living things – most chemical reaction involve solutes dissolved in waterExamples:  Marine Microorganisms spend their entire lives in salt water – an aqueous solution  Plant get the nutrients they need through aqueous solutions found in moist soil  Cells exist in an aqueous solution

acidity or alkalinity – pH  An important aspect of a living system is its degree of acidity or alkalinity – pH !  pH is determined  pH is determined by the amount of Hydrogen - H + or hydronium - H 3 O + ions dissolved in a solution.

Water Water spontaneously DISSOCIATES or “breaks apart ” to form ions (charged particles). The “free” H + ion can react with another H 2 O molecule forming a “Hydronium ion”.

 If a compound “ionizes” or dissociated when dissolved in water and produces: acidic solution, or ACID. ◦ … a greater number of H + or H 3 O + ions, the solution is said to be an acidic solution, or ACID. alkaline solution, or BASIC. ◦ … a greater number of hydroxide OH - ions, it is said to be an alkaline solution, or BASIC.

Scientists have developed a scale to measure the relative concentration of hydronium ions and hydroxide ions in a solution: From:

 pH 0-6  Taste sour  Corrosive (burn things, eat away at materials ◦ *Acid rain can corrode stone and make bodies of water uninhabitable for life.  Example: lemon juice, coke, vinegar, stomach acid.

 pH 8-14  Bitter taste  Feels slippery  Corrosive ◦ *Also called alkaline* Example: ammonia, milk of magnesia, egg white

 If the number of hydroxide ions equals the number of hydronium ions  Neither acidic or basic  pH = 7.0 Example: PURE water

 The control of pH in organisms is very important - Complex buffering systems maintain the pH values of your body’s many fluids at normal levels - Neutralization !  Produced naturally by the body to maintain HOMEOSTASIS! ◦ Rolaids, Mylanta and Pepcid are all stomach acid neutralizers. ◦ Buffered aspirin ◦ Buffered aspirin helps reduce heartburn and upset stomach that aspirin may cause.