An Introduction to Metabolism 

An organism's metabolism transforms matter and energy subject to the laws of thermodynamics 

- METABOLISM: the totality of an organism's chemical reactions= catabolic + anabolic 

- CATABOLIC PATHWAY: leads to the release of energy by the breakdown of complex molecules to simpler compounds (hydrolysis) 

- ANABOLIC PATHWAYS: consume energy to build complicated molecule from simple energy dehydration reactions

- ENERGY: compacity to do work and it comes in multiple forms 

    1. KENETIC ENERGY: movement 

    2. POTENTIAL ENERGY:  something an object can have if it has stored energy as a result of its position or structure 

    3. CHEMICAL ENERGY: a form of potential energy is stored in molecules and the amount of energy depends on the chemical bonds 

- THERMODYNAMICS: study of energy transformations that occur in matter 

    1. FIRST LAW OF THERMODYNAMICS: energy of the universe is constant and that energy can be transferred and transformed, but not created or destroyed. 

    2. SECOND LAW OF THERMODYNAMICS: every energy transfer increases entropy (amount of disorder or randomness) in the universe 

The free-energy change of a reaction tells us whether or not the reaction occur spontaneously

- FREE ENERGY: the part of a system's energy that is able to perform work when the temperature of a system is uniform 

   1. EXERGONIC REACTION: energy is released 

   2. ENDERGONIC REACTION: absorbs energy

- ATP powers cellular work by coupling exergonic reactions to endergonic reactions

- ENERGY COUPLING: the use of exergonic processes to drive an endergonic process

- the primary source of energy for cells in energy coupling is ATP 

   - when ATP transfers a phosphate group through hydrolysis, it becomes ADP

Enzymes speed up metabolic reactions by lowering energy barriers 

- CATALYSTS: substances that can change the rate of reaction without being altered in the process 

- ACTIVATION ENERGY: the amount of energy it takes to start a reaction 

- ENZYMES: macromolecule that are biological catalysts. Enzymes speed up reactions by lowering the activation energy the reactant the enzyme acts on is the substrate

- ACTIVE SITE: where the enzyme binds to the substrate 

- ENZYME- SUBSTRATE COMPLEX: when the enzyme is bonded to the substrate

    - the substrate is then converted into products and is released from the enzyme 

- changes in the shape of an enzyme will inhibit its functions

- COFACTOR: non protein helpers 

- COENZYME: organic cofactors 

- COMPETITIVE INHIBITORS: inhibitors that compete with the substrate for the active site on the enzyme 

- NONCOMPETITIVE INHIBITORS: changes the shape of the enzyme not allowing the substrate to bind to the active site 

Regulation of enzyme activity helps control metabolism 

- ALLOSTERIC SITE: a specific binding site that isn't the active site, that once bound to changes the shape of the enzyme 

- FEEDBACK INHIBITION: increases the efficiency of the pathway by turning it off when the end product accumulates in the cell