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

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