Energy and metabolism Section 1.3

Energy and metabolism  Energy is the ability to do work. Living organisms must continually capture, store and use energy to carry out the functions of life.  Metabolism refers to the sum of all *anabolic and catabolic processes in a cell or organism. *anabolic means to build, catabolic to break down

Thermodynamics  Is the study of energy  Energy is classified as either: Kinetic  energy possessed by moving objects  comes in many forms (thermal/heat, mechanical, electromagnetic and electrical) Potential  stored energy  ex: gravitational potential energy, and chemical potential energy

First Law of Thermodynamics: Energy cannot be created or destroyed but only converted from one form into another.

Types of reactions: 1.Exergonic reaction: also known as exothermic is a reaction where energy is liberated. Ex: cellular respiration

Types of reactions:  Endergonic reaction: also known as endothermic is a reaction that absorbs and uses more energy than is released. Ex: photosynthesis

Activation Energy  Most reactions do not occur spontaneously. They require activation energy (E A ) which is the energy needed to strain and break the reactants bonds and kick start the action.

ATP  Adenosine triphosphate (ATP) is the primary source of free energy in living cells. It is made of adenine (a nitrogenous base) + ribose (a 5 carbon sugar) + a chain of 3 phosphate groups.

 When a cell needs energy for an endothermic reaction it uses the enzyme ATPase to catalyse the hydrolysis of an ATP molecule. The result is an ADP molecule (adenosine diphosphate), a molecule of inorganic phosphate, P i, and the release of 31kJ/mol of free energy which can now be used as activation energy for an endothermic reaction.

 ATP recycles some of its own produced free energy to make more ATP.  A single working muscle cell uses about 600 million ATP molecules per minute!

Homework  Questions 1,2,3,4,5a,10 on page 68