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