Energy and Metabolism

Reading Guide: Biology
Energy and Metabolism
8.1 The laws of thermodynamics describe how energy changes.
The Flow of Energy in Living Things
• Energy is ________________, ____________ energy is energy of motion, while
________________ is stored energy.
• ______________ is the process whereby an atom or molecule loses an electron, and -------- is the process whereby an atom or molecule gains an electron. Oxidation-reduction
reactions always take place together.
The Laws of Thermodynamics
• The First Law of Thermodynamics states that energy cannot be created or destroyed; it
can only change from one form to another.
• During each energy conversion, some energy dissipates into the environment as _____
• The Second Law of Thermodynamics states that disorder (__________) in the universe
is continuously increasing.
• Entropy is always increasing because, as more energy is used, more energy is converted
to heat.
Free Energy
• The amount of energy available to break and form chemical bonds is referred to as a
molecule's free energy
• Reactions in which the products contain less free energy than the reactants
Activation Energy
• ______________is the extra energy required to destabilize existing chemical bonds
• _______________increase the rate of reaction by_________________ but do not alter
the proportions of the _________________
8.2 Enzymes are biological catalysts.
• Cells use _____________ to lower activation energies. _______________ enzymes are
known, each catalyzing one or a few specific chemical reactions
How Enzymes Work
• Most enzymes are ____________ with one or more __________ where specific
substrates can bind, forming an _________________________.
Enzymes Take Many Forms
• Multienzyme complexes are noncovalently bonded assemblies of enzymes that catalyze
different steps of a reaction sequence, and can offer significant advantages in catalytic
• Not all biological catalysts are proteins; for example, certain reactions can be catalyzed
by ribosomes
Factors Affecting Enzyme Activity
• Several factors can affect the activity of an enzyme, including
8.3 ATP is the energy currency of life.
• The chief energy currency all cells use is a molecule called __________.
• Because of electrostatic repulsion, the covalent bonds between phosphates are unstable;
thus, ATP is an excellent energy donor.
8.4 Metabolism is the chemical life of a cell.
Biochemical Pathways: The Organizational Units of Metabolism
• _________________ refers to the total of all chemical reactions carried out by an
• Biochemical pathways occur when the _____________________ for the next reaction.
• To operate efficiently, a biochemical pathway must be coordinated and regulated by the
cell, and regulation often takes place as _________________.