Photosynthesis – Lesson 3

Plant Types

Review

In the chemiosmotic synthesis of ATP, H+ diffuses through ATP synthase from the _____ to the _____

(a)Stroma to the thylakoid(b)Thylakoid to the Stroma

Review

Rubisco:(a)Reduces CO2 to G3P

(b)Adds CO2 to RuBP during carbon fixation

Cyclic electron flow in the chloroplast results in the production of:

(a)ATP (c) Oxygen(b)NADPH (d) None of the above

Compare and Contrast:

Versus:

C3 Plants

• Cool, moist environments• Examples:

C3 Plants

• Called “C3” because the 1st organic product of the Calvin Cycle is a 3-carbon mol. (3-phosphoglycerate)

• When [CO2] is low, rubisco takes in O2. This is called “photorespiration” and does not produce ATP or NADPH

• RuBP + O2 → Phosphoglycolate + 3-phosphoglycerate

• Why would a C3 plant do this?

Photorespiration

C4 Plants

• Hot, dry environments• Examples:

C4 Plants

• First product after carbon fixation gives a 4-carbon compound (oxaloacetate)

• Has unique leaf anatomy with 2 kinds of photosynthetic cells: (1) Bundle Sheath Cells and (2) Mesophyll Cells

• Mesophyll cells take in CO2, but Calvin Cycle occurs within Bundle Sheath only

C4 Plants

CAM Plants

• Hot, dry, arid environments • Examples:

CAM Plants

• Crassulacean Acid Metabolism• Open stoma during night and close during day

(why?)• CO2 is incorporated into organic acids at night

• Mesophyll cells of CAM plants store organic acids they make at night in their vacuoles until morning

Homework

• Read Section 3.4 in your text (pages 168-171)• Finish cheat sheet for Light Reactions and

Calvin Cycle• Start your cheat sheet for C4 and CAM plants

only (not C3)• Plant Chromatography Lab: postponed until

next week

Tomorrow:

You will have a review period to work on the following:

• Cheat sheets • Readings for lab• Catching up on missed homework• Reviewing photosynthesis lessons (1 – 3) in

preparation for a quiz next week (exact day of quiz TBA)