Photosynthesis Where does all that glucose come from? Chapter 3

How does it do that?

 Photosynthesis uses radiant energy from the sun to fix carbon dioxide into carbohydrates  The captured radiant energy is stored within the bonds of the carbohydrate as chemical energy What is it? CO 2 radiant energy Photosynthesis glucose

 Photosynthesis is used by many autotrophs to make their own food  egs. vascular plants, algae, cyanobacteria

That’s a lot of photosynthesis

Overall (Net) Equation O2O2 glucose CO 2 H2OH2O H+H+ H+H+ Energy CO 2 + H 2 O + energy  glucose + O 2 Photosynthesis

glucose + O 2  CO 2 + H 2 O + energy Overall (Net) Equation CO 2 H2OH2O H+H+ H+H+ Energy O2O2 glucose Cellular RespirationPhotosynthesis Photosynthesis and Cellular Respiration appear to be reverse processes, but they use very different mechanisms

Similarities  Both cellular respiration and Photosynthesis are similar in that both use: 1.electron transport chains 2.dissolved enzymes 3.membrane-enclosed space for chemiosmosis

Plant Tissues  Plants are made of various types of tissues  egs. Stem, leaves, roots, reproductive organs  The main site of photosynthesis is the leaves, although chloroplasts are found in all green plant parts

Leaves vascular bundle palisade mesophyll spongy mesophyll epidermis cuticle stomate EpidermisMesophyllVascular Bundles

Leaves  Leaves have 3 main types of tissues: 1.Epidermis  Usually one cell thick and secrets a waxy cuticle to prevent water loss  Pores called stomata found in lower epidermis epidermis vascular bundle palisade mesophyll cuticle spongy mesophyll stomate

Leaves 2.Mesophyll  Most photosynthesis occurs here  Two layers of parenchyma cells Palisade layer ◦Cell arrangement maximizes exposure to light Spongy layer ◦Loose arrangement of cells leaving air spaces for gas exchange epidermis vascular bundle palisade mesophyll cuticle spongy mesophyll stomate

Leaves 3.Vascular Bundles  Transport system of the plants  Contains xylem (water transport) and phloem (sugar transport) epidermis vascular bundle palisade mesophyll cuticle spongy mesophyll stomate

Opening/Closing Stomata  The guard cells (stomata) can be opened and closed to regulate gas exchange and minimize water loss in leaves Chloroplast Pore Guard Cells OPENCLOSED

Opening Stomata  To open the stomata:  Potassium ions (K + ) are actively pumped into the guard cells (uses ATP)  This causes the GCs to become hypertonic to their surroundings  Water is drawn into the GCs, increasing turgor pressure OPEN ATP K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ H2OH2O H+H+ H+H+ H2OH2O H+H+ H+H+ Cell is now hypertonic to surroundings

Closing Stomata  To close the stomata:  K + pumps deactivated allowing ions to diffuse out  Water drawn back out of the GC with the K + ions  Decrease in turgor pressure makes GCs go limp (flacid) ATP K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ OPEN

Closing Stomata  To close the stomata:  K + pumps deactivated allowing ions to diffuse out  Water drawn back out of the GC with the K + ions  Decrease in turgor pressure makes GCs go limp (flacid) K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ OPEN H2OH2O H+H+ H+H+ H2OH2O H+H+ H+H+ Cell is now hypotonic to surroundings

Closing Stomata  To close the stomata:  K + pumps deactivated allowing ions to diffuse out  Water drawn back out of the GC with the K + ions  Decrease in turgor pressure makes GCs go limp (flacid) OPEN H2OH2O H+H+ H+H+ H2OH2O H+H+ H+H+ CLOSED