Photosynthesis

Energy & Life Energy, energy, ENERGY! Autotrophs vs. heterotrophs

Chemical Energy & ATP One of the principle compounds that cells use to store and release energy is: – Adenosine triphosphate (ATP) Storing energy: – ADP + P Releasing energy: – Breaking the bond between the 2 nd and 3 rd phosphate. Active Transport, protein synthesis, movement…..firefly?

Investigating Photosynthesis van Helmont: – Soil, seedling, and water Priestley: – Candle, jar, sprig of mint Ingenhousz: – In the absence of light….

Photosynthesis: An Overview Plants use the energy of sunlight to convert water and carbon dioxide into high energy sugars and O 2, a waste product. Requires sunlight, water, and carbon dioxide. Overall equation: 6 CO H 2 0  C 6 H 12 O O 2 Occurs in the leaves of plants in organelles called chloroplasts.

Leaf Structure Photosynthesis occurs (mostly) in the palisade layer. Gas exchange of CO 2 and O 2 occurs at openings called stomata surrounded by guard cells on the lower leaf surface.

Chloroplast Structure Inner membrane called the thylakoid membrane. Thickened regions called thylakoids. A stack of thylakoids is called a granum. (Plural – grana) Stroma is a liquid surrounding the thylakoids.

Pigments Chlorophyll a is the most important photosynthetic pigment. Other pigments are also present in the leaf. – Chlorophyll b – Carotenoids (orange / red) – Xanthophylls (yellow / brown) These pigments are embedded in the membranes of the chloroplast in groups called photosystems. Light = energy! Any compound that absorbs light also absorbs energy. Chlorophyll absorbs light and transfers that energy to electrons in the chlorophyll molecule: LET PHOTOSYNTHESIS BEGIN!!!!

Photosynthesis: The Chemical Process Occurs in two main phases. – Light reactions – Dark reactions (aka – the Calvin Cycle) Light reactions are the “photo” part of photosynthesis. Light is absorbed by pigments. Dark reactions are the “synthesis” part of photosynthesis. Trapped energy from the sun is converted to the chemical energy of sugars.

Light Reactions Light-dependent reactions occur on the thylakoid membranes. – Light and water are required for this process. – Energy storage molecules are formed. (ATP and NADPH) – Oxygen gas is made as a waste product.

Dark Reactions Dark reactions (light-independent) occur in the stroma. – Carbon dioxide is “fixed” into the sugar glucose. – ATP and NADPH molecules created during the light reactions power the production of this glucose.

The Reactions of Photosynthesis Follow along with handout

The Reactions of Photosynthesis

Factors Affecting Photosynthesis Water Temperature Light intensity