Chapter 8.1: Energy and Life
• 8-1 ATP in a Molecule
(Source and Uses of Cell Energy)
8-1: Energy in a Cell
• Key Concepts:
– What is ATP?
– How does ATP provide energy for the cell?
– What is the role of ATP in cellular activities?
• Vocabulary:
– Adenosine triphosphate (ATP)
– Adenosine di- and monophosphate (ADP, AMP)
Cell Energy:
**Energy is essential to life!!
► all living things must be able to:
-produce energy;
-store energy for
future use;
-use energy in a
controlled way.
Which cellular activities
require energy…???
•
•
•
•
•
Active transport
Cell division
Movement of flagella or cilia
Production of proteins
Storage of proteins
8-1: Energy in a Cell
• Chemical Energy and ATP
– Energy can exist or be stored in many forms:
• Light
• Heat
• Electricity
• Chemical Compounds (CHEMICAL BONDS!)
8-1: Energy in a Cell
• ATP
– Adenosine TriPhosphate
• Adenine (N)
• 5-Carbon Sugar (Ribose)
• 3-phosphate groups
Phosphate groups…
• Phosphate groups are negatively
charged molecules…
• Molecules with the same charge repel
each other (they do not like being too
close to each other)
• This means that the 3 phosphate groups
on ATP are in a very unstable
arrangement!
ATP and Energy:
• This unstable arrangement of the 3
phosphate groups is like a compressed
spring…stored potential energy!
• The third phosphate group is so eager to
get away from the other two that, when
the bond is broken, energy is released…
• What is left over is a free phosphate group
and a lower energy molecule:
ADENOSINE DIPHOSPHATE (ADP)
8-1: Energy in a Cell
• ATP
– Adenosine TriPhosphate
• Adenine (N)
• 5-Carbon Sugar (Ribose)
• 3-phosphate groups
• ADP
– Adenosine DiPhosphate
• Adenine (N)
• 5-Carbon Sugar (Ribose)
• 2-phosphate groups
8-1: Energy in a Cell
• Energy in ATP is released when it is
converted to ADP (Fig. below).
• The characteristics of ATP make it an
exceptionally useful molecule that is used
by all types of cells as their basic energy
source.
ATP / ADP Cycle:
• When ATP is broken down, energy is
RELEASED and ADP is formed.
• When ADP binds with another phosphate,
energy is STORED and ATP is formed.
ATP / ADP Cycle:
ATP / ADP Cycle:
8-1: Energy in a Cell
• ATP:
– Efficient in transferring energy
– Not very good for storing large amounts of
energy long term.
– A single molecule of sugar stores more than
90 times a molecule of ATP.
How do cells use the energy
stored in ATP?
• Cellular proteins have a
specific site where ATP
can bind…
• When the ATP breaks down,
the energy is transferred to
the protein, enabling the protein
to DO WORK
(e.g. active transport, move, change shape)
Battery analogy:
• Sitting on a table, batteries are not of much
use…
• Put the batteries into a device (radio, cell
phone, etc.) and the stored energy in the
battery is put to use!
• When the battery is “dead” it can be
removed and recharged…
Battery analogy:
• The energy stored in ATP is available
when ATP is bound to a protein that will
use it;
• Once the ATP is “dead” (is not ADP), it is
released to be “recharged” back into ATP.
Summing up Questions
• What processes in the cell need energy from
ATP?
– Active transport
• How does ATP store energy?
– In its phosphate-to-phosphate bonds
• How can ADP be recycled to form ATP again?
– By adding a phosphate group
• How do proteins in cells access the energy stored
in ATP?
– They may have a pocket that ATP will fit into so that
when ATP releases energy the protein can use it