Introduction Living organisms require a constant supply of energy. Sun light is the ultimate energy source. Two groups of organisms depend on different sources of energy.

Autotrophs (self-feeders) They convert sunlight into chemical energy by the process of photosynthesis. They are producers in the food chain. Include: algae and higher plants.

Heterotrophs (other-feeders) They eat other organisms. They depend on autotrophs for their energy, directly or indirectly. Heterotrophs are consumers and decomposers in the food chain. Animals are heterotrophs.

Photosynthesis Converts the inorganic substances water and carbon dioxide into the organic nutrient glucose. Oxygen is a waste product. Occurs in all green plant tissue.

Photosynthesis Simplified Formula Light & chloroplasts 6CO 2 + 6H 2 O > C 6 H 12 O 6 + 6O 2

Site of Photosynthesis

Leaf’s Parts and Layers 1 Blade-increases surface area to catch sun light Petiole-connects the blade to the stem Cuticle-a waxy layer on the upper and lower surfaces of the leaf. It reduces water loss. Epidermis - upper and lower – Protect the internal tissues – These cells do not have chloroplasts

Leaf’s Parts and Layers 2 Mesophyll- 2 types: Palisade mesophyll- cells are rich in chloroplasts. Spongy mesophyll (contains air spaces, for gas exchange. Stomata - small pores for gas exchange, on lower surface of leaf. Stoma (one pore) has a pair of guard cells surrounding the opening.

Leaf’s Parts and Layers 3 Veins of the leaf have structural and transport function Xylem transports water and minerals from the roots to the leaves Phloem transports organic nutrients from the leaves to the roots, and from the roots to the leaves.

Chloroplasts Are cell organelles. Contain membrane-enclosed structures called thylakoids. Stacks of thylakoids are called grana. Chlorophyll (green pigments) molecules are located in the thylakoids. Stroma is the space between thylakoid grana, and it does not contain chlorophyll.

Chloroplasts

Photosynthesis Takes place in the chloroplast. Chlorophyll is activated by light energy. Photosynthesis can be divided into two sub- processes: 1. Light dependent reaction. 2. Light independent reaction, which is called the Calvin Cycle.

Summary of Photosynthesis Light-dependent Light-independent

The Light Dependent Reaction 1 Takes place in the thylakoids. Light energy is transferred to electrons in chlorophyll molecules. An activated electron leaves the chlorophyll molecule. The electrons that came from chlorophyll move through the electron transport chain (ETC), generating ATP.

The Light Dependent Reaction 2 The chlorophyll molecule that has lost an electron then pulls an electron from a water molecule. The water molelcule splits into hydrogen and oxygen, and an oxygen molecule O 2 is released.

The Light Independent Reaction Occurs in the stroma The reactions are called the Calvin cycle: 1. Conversion of CO 2 into glucose. 2. ATP provides the energy. Most of the glucose is quickly converted to starch.

The presence of starch in a leaf indicates that photosynthesis has occurred. The presence of glucose is not as good an indicator of photosynthesis, because the glucose is rapidly converted to starch after it is made.

Pigments Chlorophyll B - reflects green and yellow light (absorbs red and violet light). Chlorophyll A - reflects green and blue light Carotenes - reflect orange and dark yellow light Xanthophylls – reflect yellow and brown light

Paper Chromatography Paper chromatography is based on small differences in the solubility of pigments. If high solubility, pigments move faster. If low solubility, pigments move slower.