Unit One “Science Introduction and Cellular Function” “Energy and Life”

Energy Energy – the ability to do work Potential Energy – the capacity to do work Kinetic Energy – energy of motion The study of energy is called “Thermodynamics” because the most convenient way to measure it is in the form of heat There are many other forms of energy: light, sound, radiation, electrical current etc.

Laws of Thermodynamics First Law – energy can be converted from one state to another but it is never destroyed, and it never disappears Second Law - the universe is tending toward disorder; no organisms or machine is 100% efficient in its use of energy Entropy – is a measure of the degree of disorder of a system; the second law can simply be stated as “entropy increases”

Chemical Reactions CO2 + H2O + Sunlight  C6H12O6 + ATP + O2 The substances to the left of the arrow are called the Reactants The substances to the right of the arrow are called the Products The arrow is synonymous with the word “Yields” Reactions either require energy as they go toward completion or release energy as they go toward completion

Chemical Reactions Endergonic/Endothermic – reactions that require energy to occur Exergonic/Exothermic – reactions that give off energy in the form of heat as they occur In endergonic reactions, there is more product energy than reactant energy; this makes it more difficult for reaction to occur In exergonic reactions, there is more reactant energy than product energy; this makes it easier for reaction to occur

Chemical Reactions A “spark” is always needed to start a reaction, whether it is an exergonic or endergonic reaction This “spark” is referred to as Activation Energy, and is the chemical nudge needed to initiate the reaction Recall from chapter 3 that proteins can be enzymes which act as Catalysts A Catalyst speeds up a reaction making go toward completion at a faster rate than it would on its own In a reaction that has a catalyst present, the activation energy is lower therefore speeding up the reaction

Proteins = Enzymes = Catalysts Enzymes regulate cellular function; they ensure reactions occur when they are needed The shape of the enzyme determines its effectiveness at regulating reactions Enzymes are effective only in a certain range in reference to temperature and pH The optimal temperature at which enzymes function is approximately 98.6 F/ 37 C The optimal pH at which enzymes function is from approximately 6 to 8 on scale (close to neutral)

Proteins = Enzymes = Catalysts Enzymes are often regulated by Feedback Inhibition = the product of the reaction acts to slow the effectiveness of the enzyme A good example of feedback inhibition is a factory assembly line Workers assemble a product Workers begin to assemble product too fast Workers are instructed to slow down production

Proteins = Enzymes = Catalysts Two types of Feedback Inhibition: Competitive Inhibitors – does not change the shape of the enzyme but renders it ineffective by interfering with its ability to communicate chemically Noncompetitive Inhibitors – changes the shape of the enzyme, and shape has everything to do with its effectiveness as a catalyst

ATP, the energy of the cell ATP = Adenosine Triphosphate ATP is the energy currency of the cell ATP has three main parts: 5 Carbon sugar (y), 3 Phosphate groups (g), and a Nitrogenous base (b)

ATP, the energy of the cell ATP releases energy for use by the cell via the loss a phosphate group The resulting molecule is ADP = Adenosine Diphosphate (“di” because it has lost a phosphate group) ATP powers many of the cell’s functions: Movement of the flagella Expulsion of waste Heat production

ATP, the energy of the cell In plants, ATP is produced via Photosynthesis and Cellular Respiration (to be discussed in more detail later) In animals, ATP is produced via Cellular Respiration (to be discussed in more detail later)