Energy in Cells
Exergonic Reactions
Exergonic reaction: a reaction that releases energy
(products have lower energy than reactants).
Exo = out
An exothermic reaction is a type of exergonic reaction
that gives off energy in the form of heat.
But in biological systems,______________________
_____________________________________________,
rather than being given off in the form of heat.
Endergonic Reactions
Endergonic reaction: a reaction that requires
energy (products have greater energy than
reactants)
Endo = into
Coupled Reactions
Coupled reactions: energy from an exergonic
reaction is used to power an endergonic reaction
ATP
ATP is the energy currency of the cell.
Glucose and other food molecules contain a large
amount of energy, so they are first “converted” to
ATP to provide the energy needed for cell activities.
ATP is adenosine _____phosphate.
It is composed of adenine, ribose and
________ phosphate groups.
The bonds between the phosphate groups are high
energy bonds, which store chemical energy.
ATP is produced when a third phosphate group is
added to an ADP (adenosine diphosphate) which is a
molecule that has only two phosphate groups.
Energy is ___________ for this reaction, which comes
from the energy stored in food.
Energy is released when the bond attaching the
third phosphate group is broken, and this energy
can be used to power energy-requiring reactions.
ATP animation http://www.biologyinmotion.com/atp/index.html
Some Uses of the Energy:
•
•
•
•
__________________________
Active transport
Providing _________________________________
Movement
Discuss with your table partner:
There is a constant cycling between ATP and ADP in
the cell. On the next slide, review this ATP/ADP cycle
and explain which part of the cycle
o adds or loses a phosphate group from the
molecule
o requires energy vs. releases energy
o explain the source of energy for the energy
requiring reaction
o explain the uses of energy for the energy releasing
reaction
ATP/ ADP Cycle
ATP
Phosphate
group:
____________
Phosphate
group:
____________
Energy:
____________
Energy:
____________
ADP
Source of energy for energy requiring reaction:
_____________________________________________
Uses of energy from energy releasing reaction:
_______________________________________________
_______________________________________________
All of the major organic molecules can be used as
a source of energy for ATP.
Protein
Lipids (Fats and Oils)
Glucose is the molecule that is most readily utilized
for energy in cellular respiration.
Lipids have over __________ as much energy (which is
measured in calories) as do carbohydrates or proteins.
While proteins can be used as energy, the amino acids
from digested proteins are first used to build the
proteins needed in the cell.