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structure of chloroplast


how the structure of chloroplast enables them to carry out their functions
Mind Map by jake1445, updated more than 1 year ago
Created by jake1445 over 6 years ago

Resource summary

structure of chloroplast
  1. Photosynthesis occurs in organelles called chloroplast, this is its structure:
    1. Most are disc shaped and between 2-10 um long
      1. Has a double membrane, also called an envelope, the intermembrane space is 10-20 nm wide
        1. Outer membrane is permeable to many small ions while the inner one is less permeable
          1. Inner one has transport proteins embedded in it and is folded into lamellae which are stacked up to make a granum. Many granums are a grana
            1. Between granas are intergranal lamellae. Granas can be seen with light microscopes
              1. Grana consist of stacks of flattened membrane compartments called thylakoids. These absorb light and synthesise ATP during the light depended stage. Can be seen via electron microscope
        2. Stroma is a fluid filled matrix. Reactions of the l.d.s. occur here because the needed enzymes are there. It also contains starch grains, oil droplets, as well as DNA and prokaryote type ribosomes
      2. Adaption:
        1. Inner membrane has transport proteins the controls entry and exit of substances between stroma and cytoplasm of cell
          1. The many grana gives a large S.A for photosynthetic pigments, electron carriers and ATP synthase enzymes all of which are in the LDS
            1. Photosynthetic pigments are molecules that absorb light energy. Each pigment absorbs a range of wavelengths in the visible region while other wavelengths are reflected. They're in thylakoid membranes arranged in funnel shaped structures called photosystems and held in place by proteins. Normally the primary pigment is chlorophyll a while the accessory pigments consist of molecules of chlorophyll b and carotenoids
              1. Chlorophylls: mixture of pigments of similar molecular structure. They have a long phytol chain (hydrocarbon) and a porphyrin group like the one found in haemoglobin except here it has mg instead of fe
                1. Light hits chlorophyll and causes a pair of electrons from Mg to become excited. There are 2 types of chlorophyll a, P680 or P700, both are yellow - green and absorb red light at slight different wavelengths (absorption peaks).
                  1. Both are at the centre of the photosystems as they're primary pigment reaction centre. P680 has an absorption peak of 680nm and is found in photosystem II while P700 has an absorption peak of 700nm and is found in photosystem I
                    1. Chlorophyll a absorbs blue light of a wavelength of 450nm and chlorophyll b absorbs 500nm-640nm so blue to green
                2. Accessory pigments:
                  1. Carotenoids reflect yellow and orange light but absorb blue . Also doesnt have a porphyrin group so is not directly involved in LDS
                    1. They absorb light wavelengths that chlorophylls cant and pass on the energy from that light to the chlorophyll a at the base of the photosystem
                      1. Carotene orange and xanthophyll yellow are the main carotenoid pigments
                3. Proteins in grana hold photosystems in place
                  1. Stroma has enzymes needed to catalyse reactions of LDS in photosynthesis
                    1. Grana surrounded by stroma so products from LDS can pass to stroma for LIS
                      1. DNA in chloroplast can be used by the ribosomes there to make some of the proteins needed for photosynthesis
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