Exam__1_Study_Guide_2015 - AGECO121PlantStress: Fall2015 #1...

This preview shows page 1 - 4 out of 9 pages.

AGECO 121 Plant Stress:  It’s Not Easy Being Green Fall 2015 Study Guide and Summary for Exam #1 The following is a summary of many of the major points for Section 1 of this course It may be to a plant’s advantage to inhabit and be adapted to a “stressful” environment if it reduces competition with other plants/animals. An advantage that plants have over animals is that plants make their own food by photosynthesis . The basic reaction of photosynthesis in chemical symbols: CO 2 + H 2 O => CH 2 O + O 2 Basic photosynthetic reaction in words: Carbon dioxide and water are consumed and sugar and oxygen created. The oxygen ( O 2 ) gas released by photosynthesis comes from the splitting of water ( H 2 O) molecules. The CO 2 absorbed during photosynthesis ends up initially in the form of a 3-carbon sugar-acid called PGA . Can you think of 10 ways that you use or depend on photosynthesis? How about 20 ways? 30 ways?? More??? Plants are green because they contain large amounts of chlorophyll Chlorophyll appears green to our eyes because it is a pigment that absorbs the blue and red part of the spectrum and mostly reflects and transmits the green and yellow colors. A light absorption spectrum for chlorophyll is a graph of relative light absorbing effectiveness of chlorophyll at each wavelength (color) of light.
An action spectrum for photosynthesis is a graph of relative photosynthetic activity amount of oxygen released at each wavelength (color) of light. The action spectrum for photosynthesis tells you which colors of light are responsible for powering photosynthesis. The similarity of the photosynthesis action spectrum with the chlorophyll light absorption spectrum indicates that chlorophyll is likely the major light-absorbing pigment for photosynthesis. Measurable products of photosynthesis include oxygen (O 2 ) gas, sugar, and “biomass” (body weight) of the plant. Chloroplasts are self-contained “organelles” of plant cells. They are bordered by a membrane envelope and contain a complex stacked membrane structure inside where the light absorption and photosynthetic reactions occur. You should know the typical structure of a leaf in cross-section and what are the functions of the different cell types and structures. ( 这个自己记一下然后背 ) C3 plants are called C3 plants because the first detectable product of photosynthesis is a 3-carbon sugar acid called PGA . Rubisco is an enzyme. Enzymes facilitate chemical reactions that would otherwise not proceed very well, if at all. Rubisco converts CO 2 into sugar . RUBISCO attaches CO 2 to existing sugar molecules to make them bigger , and thereby creates more sugar (captured energy) for the plant .
Living things on earth are “carbon-based” because all the major bio-molecules (DNA, carbohydrates, proteins, and fats) contain a “backbone” of carbon atoms. Carbon atoms are the “girders” upon which life forms are constructed.

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture