Announcements &
Assignments

Lecture Objectives

Photosynthesis Web Resources

Basic Reaction
of Photosynthesis

Biomes and Productivity

The Big Picture

Light Dependent
Reactions

Calvin Cycle

Summary
(What to Know)

Lecture Syllabus

IB 100/101 Home Page

Announcements & Assignments

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

Answers to many of these questions can be found at the Text On-Line Learning Center

You may also ask questions and see answers to your classmates' questions in Web Crossing in the "Talk to Steve and Ed" discussion.

Objectives:

1. Explain how the process of photosynthesis is involved in net primary production and an increase in plant biomass.
2. Draw a sketch of a chloroplast, identify the structural components, and indicate where the photosynthetic energy transformations of the light reactions and the Calvin cycle take place.
3. List the inputs (raw materials) and outputs (products) of the light dependent reactions and the Calvin Cycle.
4. Describe how the light-dependent reactions and Calvin Cycle are chemically and energetically linked.
5. Describe the role of enzymes in the process of photosynthesis.
6. Explain how the following factors affect photosynthesis: stomatal opening, temperature, light intensity, water availability, and CO2 availability.
7. Explain what the plant does with the carbohydrate that is produced by photosynthesis.

Photosynthesis - The Basic Reaction

Lecture activity

• Get into groups with one or two other students
• From your understanding of biomes and the basic equation of photosynthesis, write down the factors you predict to be limiting the rate of photosynthesis and Net Primary Productivity (NPP) for trees in:

Biomes of North America

• Tiaga (boreal forests)
• Deserts
• Tropical forests

PRINT YOUR NAME and SIGN your name in a corner of the paper
Include the name of your discussion or lab instructor
(or the day and time of your section if you draw a blank)

Photosynthesis, the big picture

• Why are plants green? (Text, Pg. 102, fig. 6.4)
• Where does photosynthesis happen? (Text, Pg. 104, fig. 6.7)
• Chlorophyll (Text, Pg. 102, fig. 6.4)
• Chlorophyll, accessory pigments, and reaction centers (Photosystems II and I) (Text, Pg. 104, fig. 6.8)
• Light Absorbance by pigments (Text, Pg. 102, fig. 6.6 - modified)
• Light absorbance and Photosynthesis

The Light-Dependent Reactions

The conversion of light energy from the sun into usable chemical energy (ATP & NADPH) in the thylakoid membrane of the chloroplasts of plants

• An animated trip into a chloroplast. from The College of Education, University of Missouri-Columbia
• The control buttons at the bottom of this animation and the one below allow you to start, stop, step forward or backwards, and rewind.
• The Virtual Cell - Cut open the cell and zoom in on the green chloroplasts to see the arrangement of pigment and protein molecules
• Light Dependent Reactions in the Thylakoid Membranes (Text, Pg. 107, fig. 6.11)
• NAD (Text, Pg. 93, fig. 5.13)
• ATP (Text, Pg. 90, fig. 5.12)
• Model of ATP synthase in action
  from The Virtual Cell by Matej Lexa

• Summary of Energy transformation in the light reactions

• Light energy starts the process
• Flow of Electrons
• Splitting of water molecules provides electrons
• Release of oxygen molecules from water
• Accumulation of H+ in thylakoid spaces
• Reduction of NADP to NADPH by adding electrons and H+
• Production of ATP using the H+ in thylakoid spaces
• ATP synthase enzyme
• Powered by flow of H+ from the thylakoid spaces
• ADP + Phosphate (Pi) ---> ATP
• Animated Summary of the Light Reactions from Prof. Govindjee here at the U of I
• Light Reactions from The College of Education, University of Missouri-Columbia

The Calvin Cycle

Incorporation (fixing) of gaseous CO2 into solid carbohydrates in stroma of chloroplasts.

• Calvin Cycle (Text, Pg. 110, fig. 6.12)
• Cyclic series of enzyme reactions
• Rubisco (the enzyme that fixes CO2)
• Enzyme action (Text, Pg. 94, fig. 5.16)
• Addition of CO2 to a 5 carbon compound (RuBP)
• Leaf anatomy and CO2 availability (Text, Pg. 525, fig. 26.12)
• Stomates and CO2 availability (Text, Pg. 519, fig. 26.5)
• Production of carbohydrate
• Energy input from ATP
  (ATP from the light reactions ---> ADP + Phosphate back to the light reactions)
• Addition of H+ and energy from NADPH
  (NADPH from the light reactions ---> NADP back to the light reactions
• Production of carbohydrates for storage, transport, and biosynthesis
• Recycling of 5 carbon compound to fix more CO2

Photosynthesis: Summary

This is what it all distills down to - (Lewis, Pg. 105, fig. 6.9)