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

Chapter 4Is the Earth Warming?

Photosynthesis

Copyright © 2007 Pearson Prentice Hall, Inc.

Photosynthesis• Photosynthesis

– Removes carbon dioxide from the air and turns it into sugar (food)

6 CO2 + 6 H2O + light energy C6H12O6 + 6 O2

carbon dioxide + water + light glucose + oxygen +energy

• In photosynthesis, plants use light energy to rearrange the atoms of CO2 and H2O 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 plantWater vapor is lost from leaves

Transpiration

When water evaporates, the forces of cohesion and adhesion create tensionTension causes water molecules from the xylem to be drawn out into the leaf to replace the water that has evaporatedThis, in turn, increases tension on the water molecules immediately below them in the xylemThis 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

http://www.youtube.com/watch?v=At1BJJDcXhk

• 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

http://academic.kellogg.edu/herbrandsonc/bio111/animations/0053.swf

The Light Reactionsand 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 http://www.science.smith.edu/

departments/Biology/Bio231/ltrxn.html

http://dendro.cnre.vt.edu/forestbiology/photosynthesis.swf\

“Calvin cycle”**Occurs in stroma

Uses CO2s,,, ATP, & NADPH

Produces Sugar

http://www.science.smith.edu/departments/Biology/Bio231/calvin.html

http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter39/calvin_cycle.html

C3, C4, and CAM Plants• Stomatal openings

through which plant cells bring CO2 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

C3, C4, and CAM Plants• C3 plants – normal

photosynthesis

• C4 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

Sugarcanecrabgrass

houseplants