Photosynthesis How plants make glucose molecules Photosynthesis the

Photosynthesis: How plants make glucose molecules…

Photosynthesis • the process of creating chemical energy from solar energy (sunlight) • Stores energy in the bonds of sugar (glucose) • occurs in all producers/plants/autotrophs • takes place in the chloroplasts • uses chlorophyll, a green pigment

Organisms get the organic nutrients they need in two basic ways: 1. Autotrophs are organisms that are capable of synthesizing organic nutrients from simple inorganic substances (e. g. , green plants & algae) 2. Heterotrophs are organisms that cannot synthesize their own organic nutrients (e. g. , animals)

Photosynthesis occurs in chloroplasts

Parts of the Chloroplast: 1. Grana – stacks of thylakoids • Chlorophyll is located here • Light – Dependant reactions occur here (LIGHT rxns. ) 2. Thylakoids – flattened sacs of photosynthetic membranes that make up the grana 3. Stroma – region surrounding grana • Light – Independent reactions occur here (DARK rxns)

A word about pigments… • Pigments are chemical compounds which reflect only certain wavelengths of visible light • This makes them appear “colorful” • They also absorb certain wavelengths of light which we cannot see • Several pigments are embedded into the membranes of the chloroplast

• Chlorophyll A is the most important photosynthetic pigment • Other pigments are present in the leaf: – Chlorophyll B (yellow & green) – Carotenoids (orange & red) – Xanthophylls (yellow & brown)

• Chlorophyll A looks green because it reflects green light, and absorbs red and blue light • the energy from the red and blue light is absorbed and used for photosynthesis • the green light we see is reflected from the plant and cannot be used to do photosynthesis.

Electromagnetic Spectrum:

…so the solar energy called “visible light” Creates energy for photosynthesis to occur

Photosynthesis Equation: 6 H 2 O + 6 CO 2 -----sunlight------> C 6 H 12 O 6+ 6 O 2

Parts of the leaf to know: 1. Upper epidermis – single layer of cells containing few or no chloroplasts; covered by cuticle 2. Cuticle – waxy covering of leaf 3. Palisades layer – elongated cells in the leaf where photosynthesis occurs 4. Spongy layer – loosely packed, irregular cells; temporary storage of sugars & amino acids

5. Stomates – openings in the epidermis of leaves that allow the exchange of respiratory gases 6. Guard cells – regulate water loss through stomates 7. Xylem – transports water throughout the leaf 8. Phloem – food storage in the leaf 9. Spongy mesophyll – below the palisades layer; filled with cells with air spaces between them

Stoma

Photosynthesis involves 2 reactions: 1. The light-dependent reaction (needs light) 2. The light-independent reaction (does not need light)

2 reactions in Photosynthesis: 1. The light-dependent reaction happens in the thylakoid membrane and converts light energy to chemical energy Water (H 2 O) enters the thylakoid and oxygen (O 2) is given off

• The energy obtained in the light reaction is stored in a chemical called ATP (adenosine triphosphate), a compound used by cells for energy storage

2. The light-independent reaction takes place in the stroma within the chloroplast CO 2 is converted to glucose This rxn does not need light to occur But it does need the products of the light rxn (ATP & electron carriers) to produce the glucose These rxns are also called the Calvin Cycle

Thanks for the glucose!!