The "Mastering Concepts" boxes are valuable summaries of the main ideas in these sections of the text.

Objectives:

After studying this material you should be able to:

1. Describe the energy transformations that occur in a chloroplast as light energy is converted to the chemical bond energy of carbohydrate.

2. Draw a sketch of a chloroplast and indicate where these energy transformations take place.

3. List the inputs (raw materials) and outputs (products) of the light reactions and the Calvin Cycle.

4. Describe the role of ADP, ATP, NADP, and NADPH in linking the light reactions and Calvin Cycle.

5. Describe the role of enzymes in the process of photosynthesis
6. List the environmental factors that would affect photosynthesis and use your diagram from Objective 2 to indicate where and how they would have their affect. (What is the relationship between stomatal opening, temperature, water loss, and CO2 availability?)
7. Explain what the plant does with the carbohydrate that is produced by photosynthesis.

Photosynthesis Links

The Virtual Cell developed by Mat Lexa right here at the U of I.

Professor Govindjee's web page
Professor Govindjee, here at UIUC, is one of the leaders in the field of photosynthesis research and education. There are some web resources in his section on "Teaching Material on Photosynthesis, UIUC" for those who would like a little more detail and a different perspective.

THE PHOTOSYNTHETIC PROCESS Web Paper by U of I plant Biology professors John Whitmarsh and Govindjee

Chloroplast Structure (see Lewis, figure 8.6, pg. 151)

• Outer membrane

• Inner membrane systems
  • Thylakoid membranes

  • Thylakoid space (within the thylakoids)

  • Granum(a) (stack(s) of thylakoids membranes)

• Stroma (the liquid area outside the thylakoid membranes)

  Chloroplast diagram from The Photosynthetic Process by Dr.s John Whitmarsh and Govindjee

  Chloroplasts from the MIT Hypertext Cell Biology Book

  Chloroplast Membranes The Virtual Cell by Matej Lexa

The Photochemical (Light) Reactions
(see Lewis, figure 8.10, pg. 155)

• Capture of light energy
  • Thylakoid membranes

  • Photosystems II and I

  • Chlorophyll and accessory pigments

    Light absorbance and Photosynthesis
    Whitmarsh & Govindjee fig. 5

    Light absorption by Photosystems II and I
    from The Virtual Cell by Matej Lexa

• Energy Transformations
  • flow of Electrons
    • Splitting of water molecules

    • Release of oxygen molecules

    • Accumulation of H+ in thylakoid Spaces

    • Reduction of NADP to NADPH (see Lewis pg 120)

  • Production of ATP (see Lewis pg 119)
    • ATP synthase (Lewis Figure 8.10, b, pg. 155)

    • Powered by flow of H+

    • ADP + Phosphate ---> ATP

    Energy transformations in the thylakoid membranes. Whitmarsh & Govindjee fig. 3.

    Animation of energy transformations during the light reactions
    By Govindjee and Matej Lexa (This requires quite a bit of memory)

    Model of ATP Synthase in action
    from The Virtual Cell by Matej Lexa

• Summary of Light reactions: Light energy ---> usable Chemical energy (ATP & NADPH)

The Biochemical Reactions: The Calvin Cycle (see Lewis, figure 8.12, pg. 158)

• "Fixing" CO2
  • Cyclic series of enzyme reactions

  • Rubisco (the enzyme that fixes CO2)

  • Stomates and CO2 availability

  • Addition of CO2 to a 5 carbon compound

• Production of Carbohydrate
  • Energy input from ATP (ATP ---> ADP + Phosphate)

  • Addition of H+ and energy

  • Production of carbohydrates for storage, transportation, and biosynthesis

  • Recycling of 5 carbon compound to fix more CO2

• Summary of Calvin Cycle:
  Fig. 16 Whitmarsh & Govindjee

  Energy of ATP and NADPH used to fix CO2 and produce carbohydrate.

Photosynthesis: Summary

This is what it all distills down to - Lewis figure 8.13, pg. 159

Light Reactions
Light energy + H2O + Pigments	--->O2 released
ADP+Phosphate+NADP-->	ATP + NADPH-->	ADP+Phosphate+NADP
	CO2 + enzymes + RUBP-->	Carbohydrate + enzymes + RUBP
Light Independent Reactions