1. Photosynthesis (8.1 and 8.2)

2. Chemical Energy and ATP
Energy is the ability to do work
Organisms must be able to obtain and use energy
Adenosine triphosphate
ATP – composition
Adenine,
ribose (5-C sugar)
3 phosphate groups
ADP
Has 2 phosphate groups

3. Storing and Releasing Energy
Storing energy
Storing small amounts of energy
can be done by adding the 3rd
phosphate group to ADP to make ATP
ADP is like a rechargeable battery
that powers the cell
Releasing Energy
Breaking the chemical bonds in ATP can release energy
ATP can easily store and release energy by breaking and re-forming the bonds between the phosphate groups – very useful and efficient energy source for cells

4. Using Biochemical Energy
Carry out active transport
Sodium (Na+) –potassium (K+) pumps
Energy for muscle cell contractions
and movement
Movement of cilia and flagella
Synthesis of proteins
Responses to chemical signals on cellular surfaces
Produce light (fireflies)
Glucose is a better energy storage molecule than ATP

5. Heterotrophs and Autotrophs
Cannot make their own food
Consume other organisms to
obtain nutrients used for energy
Autotrophs
Make their own food by capturing
the energy from the sun
Energy is stored in food molecules produced
Photosynthesis – capturing the sun’s energy to produce high-energy carbohydrates (sugars and starches)

6. Chlorophyll and Chloroplasts
Light
White light is actually a mixture of
different wavelengths (colors)
Visible spectrum: ROYGBIV
Pigments
Light-absorbing molecules
Photosynthetic organisms use pigments to capture the sun’s energy
Chlorophyll a and b
Absorb well in the blue-violet and red regions of the spectrum but not green
Green light is reflected to plants appear green

7. Chloroplasts The organelle where photosynthesis takes place
Thylakoids – saclike photosynthetic membranes
Chlorophyll is located here
Grana - interconnected thylakoids arranged in stacks
Stroma
Fluid portion, outside the thylakoids

9. Energy Collection Chlorophyll is a special pigment
It absorbs the light energy from the sun
A large fraction of the energy
absorbed is transferred directly to
electrons in the chlorophyll molecule
itself
The energy levels of the electrons are
raised allowing a steady supply of
high-energy electrons allowing
photosynthesis to proceed

11. High-Energy Electrons
Highly reactive and require a special “carrier” molecule
An electron “carrier” is a compound that can accept a pair of high-energy electrons and transfer them, along with their energy, to another molecule

12. Carrier Molecules NADP+ Nicotinamide adenine dinucleotide phosphate
Holds two high-energy electrons along with a hydrogen ion (H+)
NADP+ converted to NADPH which allows some of the energy from the sun to be trapped in chemical form
Can also carry energy to other parts of the cell
Helps to build high0energy molecules such as glucose

13. Overview of Photosynthesis
Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen

14. Light Reactions Light-Dependent Reactions
Require direct involvement of light and light-absorbing pigments
Use energy from sunlight to produce energy-rich compounds like ATP
In the thylakoid membranes of the chloroplasts
Oxygen is released as a byproduct

15. Light Reactions Light-Independent Reactions
ATP and NADPH produced from the light-dependent reactions are used to produce
high-energy sugars from CO2
No light is needed
Takes place outside of the
thylakoids in the stroma

16. Photosynthesis – Both Rxns

17. Factors Affecting Photosynthesis
Light - intensity
Water/CO2 Concentration - concentration
Temperature – optimal range