AN INTRODUCTION TO METABOLISM

metabolic pathways
2. Organisms transform energy
3. Organisms live at the expense of free

energy
4. ATP powers cellular work by coupling exergonic reactions to endergonic reactions

to Proteins, Glucose to Starch

simpler compounds.
This energy is stored in organic molecules until need

to do work in the cell.
Anabolic pathways consume energy to build complicated molecules from simpler compounds.
The energy released by catabolic pathways is used to drive anabolic pathways.

to move matter against opposing forces.
Energy is also used to

rearrange matter.
Kinetic energy is the energy of motion.
Objects in motion, photons, and heat are examples.
Potential energy is the energy that matter possesses because of its location or structure.
Chemical energy is a form of potential energy in molecules because of the arrangement of atoms.

occur without outside help.
The processes can be used to perform

work.
Nonspontaneous processes can only occur if energy is added to a system.
Spontaneous processes increase the stability of a system and nonspontaneous processes decrease stability.
Free energy is the portions of a system’s energy that is able to perform work when temperature is uniform throughout the system.

based on free energy.
An exergonic reaction proceeds with a net

release of free energy and delta G is negative.

Fig. 6.6a

its surroundings.
Endergonic reactions store energy,
delta G is positive, and
reaction are

nonspontaneous.

Fig. 6.6b

work:
Mechanical work, contraction of muscle cells, and movement of chromosomes
Transport

work, pumping substances across membranes against the direction of spontaneous movement
Chemical work, driving endergonic reactions such as the synthesis of polymers from monomers

the nitrogenous base adenine, the sugar ribose, and a chain

of three phosphate groups.