Chapter 8: Photosynthesis
Jan 21, 2016
Chapter 8: Photosynthesis
“Energy cannot be created of destroyed, it can only be changed
from one form to another.” –Albert Einstein
Autotrophs
• Organisms that make their own food
• Example: plants
Heterotrophs
• Organisms that cannot use the sun’s energy directly and they must obtain energy from the foods they consume
• Example: Animals,
Question: Is a mushroom an autotroph or a heterotroph?
Answer: Heterotroph because it obtains food by decomposing
other organisms
Chemical Energy and ATP
• Energy comes in many forms: light, heat, electrical.
ATP
• Adenosine triphosphate: is one of the principal compounds used to store and release energy
Storing ATP vs. Releasing ATP
• Storing: When a cell has energy available it can store small amounts of it by adding a phosphate group to ADP molecules producing ATP
• ATP is like a fully charged battery
Releasing energy
• Simply by breaking the chemical bond between the second and third phosphates energy is released
Biochemical Energy
Active transport across the cell membrane Examples:
-Sodium Potassium Pump-Providing movement for motor proteins-Synthesis of proteins and nucleic acids
Question: Do cells keep large amounts of ATP or small amounts
in the cell at all times
Answer: Cells only keep a small amount of ATP in the cell at all
times.
Photosynthesis
• Is the process used by plants and other organisms to convert light energy, normally from the Sun, into chemical energy that can be later released to fuel the organism’s activities
• Takes place in the chloroplast, which is typically found in the leaves of plants
The Photosynthesis Equation
Parts of the chloroplast
Light Dependent reaction
• Chloroplast contain saclike photosynthetic membranes called thylakoids
•
Light dependent Reaction
• Stacks of thylakoid is known as grana• Proteins in the thylakoid membrane organize
chlorophyll and other pigments into clusters known as photosytems. – Photosystems: light-collecting units of chloroplast
Lights and Pigments
• White light which is sunlight is actually a mixture of different wavelength of light.
• Pigments: plants gather the sun’s energy with light absorbing molecules known as pigments
• Chlorophyll: there are two main types of cholorphyll a and b
Question: Why are plants Green?
Question: Why do leaves change colors?
Light Independent Reaction
• Or the Calvin cycle takes place in the stroma
Light dependent Rxn vs. Light Independent ( Dark) Rxn
• Light: takes place in the thylakoid membrane
• Produce oxygen and convert ADP and NADP+ into the energy carriers ATP and NADPH
• Dark: Calvin cycle takes place in the stroma
• Uses ATP and NADPH from the light rxn to produce high energy sugars
• http://www.butler.edu/herbarium/fallcolor/leaveschange.htm