Chapter 8 - Chapter 8 PHOTOSYNTHESIS...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 8 PHOTOSYNTHESIS Photosynthesis : (synthesis from light) biochemical process by which plants capture energy from sunlight and store it as carbohydrates It is the very basis of life on Earth converts light energy into chemical energy (stored in bonds of organic molecules) carried out by photoautotrophs these include green plants, algae, and a few bacteria Photosynthesis occurs in chloroplasts in green plants Chloroplast structure: Double membraned organelle Thylakoids arranged in stacks (grana) Surrounded by stroma OVERVIEW OF TWO MAIN COMPONENTS OF PHOTOSYNTHESIS : Photosynthesis can be divided into two pathways: Light reactions : produce ATP and NADPH Light-independent reactions Carbon Fixation uses ATP, NADPH + H + and CO 2 to produce sugars Calvin cycle, C 4 & CAM The Interactions of Light and Pigments When a photon and a pigment molecule meet, one of three things happens: The photon may be: Scattered or reflected Absorbed by molecule, Or it may pass through ( transmitted ) Molecules that absorb wavelengths in visible range are called pigments Plants look green because chlorophyll absorbs green light less effectively than other colors in sunlight Plants have two main chlorophylls: a & b . These absorb blue & red wavelengths, near ends of visible spectrum Accessory pigments absorb photons between red & blue wavelengths transfer energy to chlorophylls Ex. carotenoids , such as b-carotene, phycobilins Broaden usable spectrum An excited state is unstable àฏ the molecule will return to ground state
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
some absorbed energy is given off as heat rest given off as fluorescence Alternatively, pigment molecules may pass some of the absorbed energy to other pigment molecules Pigments are arranged in antenna systems , packed together into thylakoid membrane proteins Excitation energy is passed to pigments that absorb short wavelengths to those that absorb longer wavelengths Ends at reaction center pigment In plants, the pigment molecule in the reaction center is chlorophyll a Electrons of excited molecules are less tightly held by the nucleus àฏ more likely to be passed on in a redox reaction to an oxidizing agent (an electron acceptor) Chlorophyll becomes a reducing agent (loses electron), in the redox reaction PHOTOSYNTHETIC PIGMENTS Chlorophyll a
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern