4.1 Chemical Energy and ATP
KEY CONCEPT
All cells need chemical energy.
4.1 Chemical Energy and ATP
Objectives
• Recognize the importance of ATP as an energy-carrying
molecule.
• Identify energy sources used by organisms.
4.1 Chemical Energy and ATP
Vocabulary
• ATP
– Adenosine Triphosphate
- High-energy molecule that contains, within its bond, energy
that cells can use.
• ADP
– Adenosine Diphosphate
- Low-energy molecule that can be converted to ATP.
• Chemosynthesis
– A process by which ATP is synthesized by using
chemicals as an energy source instead of light
4.1 Chemical Energy and ATP
The chemical energy used for most cell processes is
carried by ATP.
• Molecules in food store chemical energy in their bonds.
Starch molecule
Glucose molecule
4.1 Chemical Energy and ATP
• ATP transfers energy from the breakdown of food
molecules to cell functions.
– Energy is released when a phosphate group is removed.
– ADP is changed into ATP when a phosphate group is
added.
phosphate removed
4.1 Chemical Energy and ATP
Organisms break down carbon-based molecules to
produce ATP.
• Carbohydrates are the molecules most commonly broken
down to make ATP.
– not stored in large amounts
– up to 36 ATP from one
glucose molecule
adenosine
triphosphate
tri=3
adenosine
di=2
diphosphate
4.1 Chemical Energy and ATP
• Fats store the most energy.
– 80 percent of the energy in your body
– about 146 ATP from a triglyceride
• Proteins are least likely to be broken down to make ATP.
– amino acids not usually needed for energy
– about the same amount of energy as a carbohydrate
4.1 Chemical Energy and ATP
A few types of organisms do not need sunlight and
photosynthesis as a source of energy.
• Some organisms live in places
that never get sunlight.
• In chemosynthesis, chemical
energy is used to build
carbon-based molecules.
– similar to photosynthesis
– uses chemical energy
instead of light energy
4.1 Chemical Energy and ATP
Question/Answer
• How are ATP and ADP alike?
– They both contain adenosine and phosphate groups
• How are the different?
– ATP has three phosphate groups
– ADP has two phosphate groups
• Why is this difference important?
– The extra bond is a potential source of energy
4.1 Chemical Energy and ATP
Question/Answer
• Describe the relationship between energy stored in food
and ATP.
– Food molecules store chemical energy in their bonds.
Food is broken down into smaller molecules that are
broken down further to transfer this energy to ATP.
• How do lipids and carbohydrates differ in ATP
production?
– Lipids provide more ATP than carbohydrates do
• How are chemosynthetic organisms and plants similar as
energy sources?
– Both chemosynthetic organisms and plants make their
own food and both are eaten by other organisms that
cannot make their own food.