Chapter 6 Flashcards
Metabolism: Energy and Enzymes
Two Types of Energy
Kinetic:
Energy of motion
Mechanical
Potential:
Stored energy
Chemical - comprised of organic molecules
Relationship between chemical and mechanical energy
Animals convert chemical (potential) energy into a type of kinetic energy (mechanical). Example when a moose walks
First Law of Thermodynamics or Law of Conservation of Energy
Energy cannot be created or destroyed but energy can be changed from one form to another
What is an example of the First Law of Thermodynamics
Solar Energy flowing from the sun some is dissipated and becomes heat and other is converted by the plant into chemical (potential) energy. The moose converts a portion of this chemical energy into mechanical of motion and most of the chemical energy dissipates into heat.
Heat is
Disorderly energy that cannot be easily used
Second Law of Thermodynamics - Law of Entropy
Every energy transformation (solar to chemical, solar to heat, etc.) there is a loss of usable energy
Waste energy goes to increase disorder
Entropy - is a scientific concept that is most commonly associated with a state of disorder, randomness, or uncertainty.
Example of Entropy Law
The second law tells use that glucose tends to break apart into carbon dioxide and water over time. Because glucose is more organized and structured, and therefore less stable than its breakdown products.
Explain the importance of entropy to a living system
Organisms that consume potential energy that is originally provided by the sun and sun energy is converted to potential energy in a more stable form which is easily converted to mechanical energy. A living cell can function because it serves a a temporary repository of order, purchased at the cost of constant flow of energy
What is Metabolism?
Sum of cellular chemical reactions in cell
Reactants participate in a reaction
Products form as result of a reaction
Relationship between Reactants and Products
Reactants are substances that participate in a reactions, which products are the substances that form as a result of a reactions.
What is Free energy
Free energy is the amount of energy available to perform work
Metabolism includes two types of reactions
Exergonic Reactions - Products have less free energy than reactants —release energy
Endergonic Reactions - Products have more free energy than reactants —require an input of energy
What is ATP
Adenosine (Adenine and ribose) triphosphate - three phosphate groups
High energy compound used to drive metabolic reactions
Constantly being generated from ADP*
ADP - adenosine diphosphate composed of adenosine and two phosphate groups and is more stable and has lower potential energy.
What is the ATP Cycle
in cells ATP carries energy between exergonic reactions (release energy) and endergonic reactions.
When a phosphate group is removed by hydrolysis*, ATP releases the appropriate amount of energy for most metabolic reactions.
The hydrolysis of ATP releases previously stored energy allowing the change of in free energy to do work.
Creation of ATP from ADP and inorganic phosphate requires energy input from other sources
*is any chemical reaction in which a molecule of water breaks one or more chemical bonds
What are Coupled reactions
Energy released by an exergonic reaction captured in ATP
ATP is used to drive an endergonic reaction
in other words ATP breakdown is coupled to the energy requiring reaction, such that both the energetically favorable and unfavorable reactions occur in the same place, at the same time. ATP’s phosphate groups releases more energy than the amount consumed by the engergy-requireing reactions, the net reaction is exergonic, entropy increases, and both reactions proceed.
Work-Related Functions of ATP
Primarily to perform cellular work
Chemical Work - Energy needed to synthesize macromolecules
Transport Work - Energy needed to pump substances across plasma membrane
Mechanical Work - Energy needed to contract muscles, beat flagella, etc
What is an enzyme
is a molecule that speeds up a chemical reactions without itself being affected by the reaction.
Most enzymes are proteins.
Metabolic Pathways
Reactions usually occur in a sequence
Products of an earlier reaction become reactants of a later reaction
Such linked reactions form a metabolic pathway
Begins with a particular reactant, Proceeds through several intermediates, and Terminates with a particular end product
Each reaction in a metabolic pathway requires a unique and specific enzyme
The end product will not be formed unless ALL enzymes in the pathway are present and functional
What are substrates?
The reactants in an enzymatic reaction are called substrates for the enzyme.
The substrates for the first reaction are converted into products and those products then serve as the substrates for the next enzyme-catalyzed reactions.
Energy of Activation
Molecules frequently do not react with one another unless they are activated in some way
Energy must be added to at least one reactant to initiate the reaction Energy of activation
Enzyme Operation:
Enzymes operate by lowering the energy of activation
Accomplished by bringing the substrates into contact with one another
IMPORTANT to note that the enzyme has no effect on the energy content of the product, rather it only influences the rate of reaction
What are enzymes referred as?
The catalysts of chemical reactions
Enzyme-Substrate Complex
Only one small part of the enzyme, called the active site, associates directly with the substrate.
Induced fit model
Causes the active site to change shape
Shape change forces substrates together, initiating
bond
After the reaction has completed, the active site returns to its original state
Note only a small amount of enzyme is actually needed in the cell, because enzymes are not used up by the reaction; they are merely enable it to happen quicker.
What is the difference between Degradation and Synthesis
Degradation:
Enzyme complexes with a single substrate molecule
Substrate is broken apart into two product molecules
Synthesis:
Enzyme complexes with two substrate molecules
Substrates are joined together and released as a single product molecule
Factors Affecting Enzyme Activity
-Substrate concentration
Enzyme activity increases with substrate
concentration due to more frequent collisions
- Temperature
Enzyme activity increases with temperature
Body temperature of ectothermic animals (iguanas)
often limits their reaction
Body temperature of endothermic animals (polar
bears) promotes rates of reaction
-pH
Most enzymes perform optimally at a particular pH
