Photosynthesis

Biology 100/101
Lecture 7: Photosynthesis

Text Readings in Lewis	Review questions	"To think about"
Chapter 3 Proteins & Enzymes Pages 48-53 Chapter 6 Energy, ATP, NADPH Pages 113-122 Chapter 8 Photosynthesis Pages 145-165	Page 124 Questions 11,12, &13 Page 165-6 1,2,3, 6 & 14	Page 165 questions 1, 2, 3, & 10

Answers to many of these questions can be found on the "Answers to End-of-Chapter Questions" page at the text website.

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:

Explain how the process of photosynthesis is involved in a gain in plant biomass.
Draw a sketch of a chloroplast identifying structural components and indicate where the photosynthetic energy transformations take place.
Describe the energy transformations that occur in a chloroplast as light energy is converted to the chemical bond energy of carbohydrate.
List the inputs (raw materials) and outputs (products) of the light reactions and the Calvin Cycle.
Describe how the light-dependent reactions and Calvin Cycle, are linked.
Describe the role of enzymes in the process of photosynthesis

Explain how the following environmental factors affect photosynthesis; stomatal opening, temperature, light intensity, water availability, and CO2 availability.

Explain what the plant does with the carbohydrate that is produced by photosynthesis.

Photosynthesis Links

Photosynthesis - The Basic Reaction

CO2 + H2O + Light Energy
Carbon Progenitor (RuBP)
Chloroplast Machinery ---> Simple
Sugars + O2

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
(see Lewis, figure 8.10, pg. 155)

Capture of light energy by chlorophyll
- Thylakoid membranes in granal stacks, stroma
- Chlorophyll, accessory pigments, and reaction centers (Photosystems II and I)
- Why are plants green?
Energy Transformations in thylakoid membranes
- 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
  - ATP synthase (Lewis Figure 8.10, b, pg. 155)
  - Powered by flow of H+
  - ADP + Phosphate (Pi) ---> ATP
  Model of ATP Synthase in action
  from The Virtual Cell by Matej Lexa

The Light-Independent Reactions or The Calvin Cycle
Incorporation of gaseous CO2 into solid carbohydrates in stroma of chloroplasts. (see Lewis, figure 8.12, pg. 158)

Incorporating or "Fixing" CO2 in stroma of the chloroplasts
- Cyclic series of enzyme reactions
- Rubisco (the enzyme that fixes CO2)
- Stomates and CO2 availability
- Addition of CO2 to a 5 carbon compound (RuBP)
Production of Carbohydrate
- Energy input from ATP (ATP ---> ADP + Phosphate)
- Addition of H+ and energy
- 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 figure 8.13, pg. 159 (with modifications)