Photosynthesis and the Leaf

Energy A.The sun is the source of energy for almost all life on Earth B.The sun’s energy is transferred into a useable form through photosynthesis C.Photosynthesis uses energy from the sun to convert water and carbon dioxide into high-energy sugar and oxygen

Photosynthesis & Respiration 3 Kinds of Respiration –1) external respiration- breathing, exchange of gases between atmosphere and lungs –2) internal respiration – exchange of O 2 between blood and body cells –3) cellular respiration – chemical reaction where O 2 molecules and broken down food molecules react to produce ATP in the mitochondria

Formula for Respiration C 6 H 12 O 6 + 6O 2  6H 2 O + 6CO 2 + energy Glucose + oxygen = water + carbon dioxide + ATP This is the process by which glucose molecules are broken down to release energy (ATP) Occurs inside the mitochondria of cells

The Respiration/Photosynthesis Cycle Produced by RespirationUsed in Photosynthesis CO 2 + energy Glucose + O 2 Used in RespirationProduced by Photosynthesis

Photosynthesis What kind of organisms carry out photosynthesis? A.They have pigments = light absorbing molecules B.Plants and other green organisms have specialized organelles that help with this process. This organelle is called chloroplast C.Photosynthesis takes place inside the chloroplast within leaf cells

Formula for Photosynthesis What goes in? What goes out? Start with the equation: 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 Carbon dioxide + water = glucose + oxygen

Light-dependent Reactions These reactions require light Take place in the thylakoid membranes Produces ATP, NADPH (electron carrier), and oxygen Calvin cycle The second cycle of photosynthesis Products from light- dependent reactions are synthesized into high energy glucose These reactions are also known as the light- independent reactions, because they do not require light

Leaf Structure A. Epidermis the top and bottom layers of the leaf Protects the inner tissue from injury or drying out

Leaves B. Cuticle waxy covering on the leaves secreted by the epidermis cells, prevents water from escaping Important because plants need water for photosynthesis

Leaves C. Stomata (pl. stoma) Pores scattered through the leaf epidermis Carbon dioxide enters through stoma and Oxygen is released through stoma Water vapor can also pass in and out of the stoma (dew) Stoma are generally open at night and closed during the day. Typically on underside of leaf

Leaves D. Guard Cells Crescent shaped cells which guard the stoma Responsible for opening and closing the stoma Guard cells pull stoma open when they become turgid (full of water)

Leaves E. Mesophyll Layers of cells inside the epidermis Most photosynthesis takes place inside this part of the leaf where the cells contain chloroplasts.

Leaves F. Leaf veins Vascular tissue in the leaves that contain xylem and phloem Evaporation from the leaves (transpiration) produces the suction that pulls water up the xylem delivering nutrients to other parts of the plant.

v=mYbMPwmwx88&feature=rel ated