Chapter 8
An Introduction to Metabolism
Metabolism
• Metabolism is the sum of all chemical reactions in
your body.
• If a reactions breaks things down, it is catabolic
• If a reaction builds things up, it is anabolic
Energy
• Energy is the capacity to cause change.
• Energy of motion is kinetic energy
• Energy that is stored is potential energy
• Potential energy that is released during a chemical
reaction is chemical energy
Energy is released or
consumed
• In an exergonic reaction energy is
released.
• When you break things down, you
release energy
• All catabolic reactions are exergonic
• Cellular respiration is exergonic.
• These are spontaneous reactions
• Delta G (a measure of free energy)
is negative
Energy is released or
consumed
• In an endergonic reaction energy is
absorbed.
• When you build things, you need
energy
• All anabolic reactions are endergonic
• Photosynthesis is endergonic
• These are non-spontaneous reactions
• Delta G is positive
Making and breaking bonds
• Making bonds is called dehydration synthesis. You
take away water to make a new bond.
• Breaking bonds is called hydrolysis. You add water
to break a bond.
Introducing ATP
• ATP is adenosine triphosphate
• It is composed of a nitrogenous
base called adenine, a ribose
sugar, and a chain of 3
phosphate groups
• Energy is stored in the bonds
between the phosphate groups.
• When a bond is broken between
the Ps, it releases energy
ATP to ADP to ATP
• To get the energy,
hydrolysis occurs to
break off 1 P, turning
ATP into ADP
• During cellular
respiration, energy
from food is used to
add the P back on to
ADP to make more
ATP
Enzymes!
• Enzymes are proteins. They are catalysts that speed
up chemical reactions by lowering the amount of
energy needed for those reactions to start (activation
energy)
Enzyme terms
• The thing an enzyme binds
to and acts on is called the
substrate.
• The place where the enzyme
binds is the active site.
• Enzymes are specific and
only fit to their own substrate
like a key into a lock
• Enzymes are reusable and
are used over and over
Factors affecting enzymes
• 1. Temperature
• 2. pH
• 3. Salinity
Factors affecting enzymes
• Some enzymes need helpers:
• Cofactors are INORGANIC and bind to the
enzymes to make them work (zinc, iron, copper,
minerals)
• Coenzymes are ORGANIC and bind to the enzyme
to make them work (vitamins)
Factors affecting enzymes
• Inhibitors block enzyme action
• Competitive inhibitors bind to
the active site of the substrate so
that the enzyme can’t get in
• Non-competitive inhibitors bind
somewhere on the substrate,
changing the shape of the active
site, so enzymes no longer fit