slide 8 Flashcards
Metabolism
The Energy of Life
The living cell
• Is a miniature factory where thousands of
reactions occur
• Converts energy in many ways
Metabolism
- Includes all of an organism’s chemical reactions
- Is a network of pathways
- Arises from interactions between molecules
An organism’s metabolism transforms
matter and
energy subject to the laws of thermodynamics
A metabolic pathway has many steps
These begin with a specific molecule or
molecules and end with a specific product
Each step is facilitated by a specific catalyst
A catalyst
is a substance that accelerates the rate of a chemical reaction without affecting the products of the reaction and without itself being altered or consumed by the reaction.
enzymes.
The catalysts in living
organisms are proteins called
enzymes
Metabolic pathways balance supply and demand.
• Speed up reactions when not enough product is present
• Slow down reactions when a surplus of product is present
• Products in one set of reactions are the starting molecules
in other sets of reactions.
Catabolic pathways
• Break complex molecules into simpler ones
• Release energy
e.g. hydrolysis
reactions
Anabolic pathways
• Build complicated molecules from simpler ones
• Consume energy
e.g. dehydration
reactions
Energy
– Is the capacity to cause change
– Exists in various forms, some can perform work
Kinetic energy
– Is the energy associated with motion
Potential energy
– Is stored in the location of matter
– Includes chemical energy stored in molecular
structure (chemical bonds)
There are many forms of energy
(light, heat, chemical, electrical,
etc.) but only two states:
Potential energy is stored energy
Kinetic energy is the energy
present in the motion of a body
1st law of thermodynamics
- energy is neither
created or destroyed, but can be transformed
from one form to another
2nd law of thermodynamics -
physical systems
tend to proceed to a state of greater disorder
(entropy)
Energy enters a biological system
is spent, transformed, and lost as heat.
Gibbs free energy is the energy available for
work in a system at uniform temperature.
Josiah Willard Gibbs
1839-1903
The free-energy change of a reaction tells us
whether the reaction occurs spontaneously.
During a spontaneous change free energy
decreases and the stability of a system increases
Spontaneous change:
- The free energy of the system decreases - The system becomes more stable - The released free energy can be harnessed to do work
exergonic reactions.
The majority of the reactions in living cells release
free energy and are called exergonic reactions.
endergonic reactions.
Many important reactions in cells, however,
require the addition of energy and are called
endergonic reactions
equilibrium,
Reactions in a closed system eventually reach
equilibrium, and can do no more work.
Equilibrium and Metabolism
Cells in our body experience a constant flow of materials in and out, preventing metabolic pathways from reaching equilibrium
