Biology Class 6

“The Energy of Life”_ I.

_________Biology

6th Class

Energy – The ability to do work >>> Measured in Calories Sources of Energy Ultimately all energy depends on energy from: 1. The Sun 2. Inorganic Chemicals

2 Types of Energy Consumers * Photoautotrophs – use sunlight to make energy (plants, algae, cyanobacteria) • Chemoautotroph – use inorganic chemicals to make energy (certain bacteria) II. Biochemical Reactions 1. Metabolism – chemical reactions that change or transform energy in cells B. Anabolic (synthesis) Reactions – building large molecules from small ones 1. Require energy (endergonic) – products contain more energy than reactants C. Catabolic (degredation) Reactions – break down large molecules into small ones 1. Release energy (exergonic) – products contain less energy than reactants III. Molecules Involved in Energy Transformations A. ATP (adenosine triphosphate) – Energy Currency of Cells Cells couple ATP formation and breakdown into other reactions B. Enzymes (biological catalysts) Proteins that speed up chemical reactions without being altered in the process They accomplish this by decreasing the activation energy

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Enzymes are: Highly Specific – active site on enzyme binds to specific substrates Reusable Enzymes can be affected by: Temperature pH Salt Concentration Negative Feedback (feedback inhibition) ** There are two negative feedback mechanisms: 1. Competitive inhibition 2. Non Competitive Inhibition

(Positive feedback rarely affects enzyme activity)