Photosynthesis Flashcards
Reading for unit: Energy: pg. 218-221 Photosynthesis: pg. 222-227
Autotroph
An organism that creates it’s own food.
Chemoautotroph
An organism that derives energy from oxidation of inorganic compounds.
Heterotroph
An organism that cannot make it’s own food.
Cellular respiration
A catabolic pathway in which organic molecules are broken down to release energy for use by the cell.
Photosynthesis
Two-phase
Anabolic pathway in which the suns light energy is converted to chemical energy to be used by the cell.
Calvin Cycle
Light-independent reactions during phase two of photosynthesis in which energy is stored in organic molecules as glucose.
Light Dependent Reactions
The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH.
ATP and NADPH provide the energy needed to build high-energy sugars from low-energy carbon dioxide in the light-independent reactions.
Factors affecting Photosynthesis
- Temperature: Too hot or too cold, photosynthesis slows down or stops
- Water: Lack of water slows down or stops photosynthesis
- Light Intensity: Increased light = increase in rate, up to a certain level
- Amount of CO2: More carbon dioxide = faster rate of photosynthesis
In photosynthesis, what are the two major reactions that take place?
- Light dependent reactions
- Light independent reactions
In aerobic cellular respiration, what three major steps are involved?
- Glycosis
- Krebs Cycle
- Electron transport chain
Formula for Photosynthesis
6CO2 + 6H2O → C6H12O6 + 6O2
Formula for Cellular Respiration
C6H12O6 + 6 O2 –> 6 CO2 + 6 H2O + ATP
How does ADP become ATP and vice versa?
A phosphate is broken off (ATP –> ADP)
A phosphate is added (ADP –> ATP)
Photosystem II
Pigments absorb light
High energy electrons are passed to electron transport chain
As light continues to shine, more and more electrons are passed to transport chain
Enzymes break H2O into 2 electrons, 2 H+ ions and 1 oxygen atom
Electron transport chain
Electrons move into chain
Energy from electrons is used by proteins(ATP synthase) to pump H+ ions from stroma to thylakoid
(Electrons then pass to photosystem I)
Photosystem I
Electrons now have less energy (it was used to pump H+ across thylakoid membrane)
Pigments use energy from light to reenergize electrons
NADP+ molecules in the stroma pick up the high-energy electrons and H+ ions at the outer surface of the thylakoid membrane to become NADPH.
(These will be used in the light independent reactions)
Light-Independent Reactions
During light-independent reactions, ATP and NADPH molecules produced in the light-dependent reactions are used to produce high-energy sugars from carbon dioxide.
No light is required to power the light-independent reactions.
The light-independent reactions take place outside the thylakoids, in the stroma.
ATP synthase
ATP-making enzyme
ATP synthase adds a phosphate to a molecule called ADP to make ATP.
What is ATP used as?
ATP is used as an energy source for many chemical reactions in cells.
NADP+
Molecule used for energy transport within the cell
When two electrons and a hydrogen are added to NADP+, it becomes NADPH
NAPDH
A biological compound used to fuel many processes within a cell.
NADPH is produced when a molecule of NADP+ has one hydrogen and two electrons added to it.
NADPH can then donate its hydrogen, electrons, and energy to an enzyme or other molecule to fuel a cell process.
ATP
A molecule that is made up of adenosine and three phosphates.
Cells use ATP as a source of energy
Chlorophyll
The main light-absorbing molecule used to power photosynthesis.
Chlorophyll absorbs red and blue light, but it reflects green light.
(This is why many plants appear green.)
Stroma
The fluid found inside of a chloroplast.
