The Working Cell
How Cells
Get Energy
Life Depends on Energy
What is energy?
1st Law of
Thermodynamics
Two types of
energy?
2nd Law of
Thermodynamics
2nd Law in Action
Food Energy
Calorie

Energy needed to raise 1 g by 1 ºC
Food is in kcal
Metabolism
How can we get energy from foods we
eat?
Where is the potential energy in foods?
 How does the potential energy in foods get
converted to kinetic energy useable by
cells?

ATP: Adenosine
triphosphate
The tail of ATP is vary unstable

This means greater potential energy
When a phosphate is transferred to another
molecule, energy is released
Energy Coupling
Chemical energy is
‘harvested’ from food
molecules

Where’s the energy in
food?
This energy is used to
recycle ADP to ATP
Enzymes
Your metabolism and
ETC are controlled
and catalyzed by
enzymes
What are enzymes?
How do they work?
Activation Energy
For a reaction to occur, an energy barrier must
be surmounted
Enzymes make the energy barrier smaller
Induced-Fit Model
Enzymes are
substrate specific
Substrates bind to
active sites
Substrates are
altered slightly by
induced fit
Induced fit favors
the reaction
How Enzymes Work
Enzyme Inhibition
Some molecules affect enzyme
function
Competitive
Non-competitive
Feedback Inhibition
Diffusion
Molecules never
stay still
Diffusion moves
molecules ‘down
concentration
gradient’
Osmosis
Diffusion of water molecules
Osmoregulation
Osmoregulation
Passive & Facilitated
Transport
Active Transport
Signal Transduction
Pathway
Active Transport
What about molecules that are too big
to pass through a transport protein?
Endocytosis