Class Notes (810,237)
Canada (494,016)
Biology (6,684)
Lecture 6

2012.02.11 - Bio 1202 Lecture 6 Review Notes.docx

2 Pages
Unlock Document

Western University
Biology 1202B
Gardiner/ Murphy

Lecture 6  On hot, dry days plants close the stomata to conserve water, but this causes problems for photosynthesis  C3Plants: o Cotton, rice, spinach, lettuce, carrots, apples, etc. o Initial fixation of 2O occurs via rubisco o When their stomata re closed, CO l2vels drop as CO i2 consumed in the Calvin cycle o At the same time, O 2evels rise as the light reaction converts light to chemical energy o While rubisco normally accepts CO ,2when the stomata is closed the O /2O ra2io increases, and rubisco can add O to RuBP instead of CO 2 2 o When rubisco adds O to2RuBP, it splits into a 3-carb piece and a two-carbon piece in a process called photorespiration  The two-carbon fragment is exported from the chloroplast and degraded to CO 2 by the mitochondria and peroxisomes  Unlike normal respiration, this process requires no ATP or organic molecules  C4Plants: o Corn, sugarcane, crabgrass, pigweed, Russian thistle, etc. o They fix CO first in a four-carbon compound 2 o Mesophyll cells (spongy cells in leaf) incorporate C2 into organic molecules  The key enzyme (phosphoenolpyruvate carboxylase) adds CO to 2 phosphoenolpyruvate (PEP) to form oxaloacetate  PEP carboxylase has a very high affinity for C2 and can fix CO2efficiently when rubisco cannot
More Less

Related notes for Biology 1202B

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.