Chapter 4 Is the Earth Warming? Photosynthesis Copyright © 2007 Pearson Prentice Hall, Inc.

Photosynthesis –Removes carbon dioxide from the air and turns it into sugar (food) 6 CO H 2 O + light energy  C 6 H 12 O O 2 carbon dioxide + water + light  glucose + oxygen +energy In photosynthesis, plants use light energy to rearrange the atoms of CO 2 and H 2 O into carbohydrates

Photosynthesis Plants are not the only organisms that can photosynthesize Algae Photosynthetic bacteria can photosynthesize without chloroplasts

Xylem sap (water and dissolved minerals from soil) travel up inside a plant Water vapor is lost from leaves Transpiration

When water evaporates, the forces of cohesion and adhesion create tension  Tension causes water molecules from the xylem to be drawn out into the leaf to replace the water that has evaporated  This, in turn, increases tension on the water molecules immediately below them in the xylem  This causes water to move towards the leaves, and so on Transpiration relies on –The sun to cause evaporation –Hydrogen bonding Plants can modify the rate of transpiration by regulating stomata size cXhk

Chloroplasts are structures in plant cells that allow them to carry out photosynthesis

Pigment molecules called chlorophyll are on the surface of the thylakoid membrane Chlorophyll molecules absorb and capture light energy from the sun Chlorophyll gives plants their green color

The electromagnetic spectrum is made up of several types of light, each having a different energy level and wavelength andsonc/bio111/animations/0053. swf

The Light Reactions and Calvin Cycle Step 1: photo- –Light reactions Light energy is harvested Step 2: -synthesis –Calvin cycle Sugar is made

Uses  Water and light Produces  Oxygen, ATP, and NADPH Light Reaction**Occurs in thylakoid ments/Biology/Bio231/ltrxn.html

“Calvin cycle” **Occurs in stroma Uses  CO 2 s,,, ATP, & NADPH Produces  Sugar artments/Biology/Bio231/calvin.ht ml graw- hill.com/sites/ /student_vi ew0/chapter39/cal vin_cycle.html

C 3, C 4, and CAM Plants Stomatal openings through which plant cells bring CO 2 into leaves are surrounded by guard cells that open and close Water can also move through the stomatal openings in transpiration Photorespiration involves the closing of stomatal openings to prevent water loss

C 3, C 4, and CAM Plants C 3 plants – normal photosynthesis C 4 plants – live in hot climates; need to conserve water; can make sugar, but this takes more ATP than normal CAM plants –stored as acid until daytime Sugarcane crabgrass houseplants