Plastids and Chloroplast Structure
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Questions and Answers

What causes photorespiration to occur?

  • High levels of CO2
  • High temperatures only
  • Non-specificity of Rubisco (correct)
  • Low light intensity

    • Photorespiration results in energy production for the plant.

    False

    What happens to the CO2/O2 ratio when the stomata are closed?

    The CO2/O2 ratio decreases.

    Photoinhibition is produced by very high light intensity that causes __________________ of the PSII system.

    <p>over excitation</p> Signup and view all the answers

    Match the following terms related to undesired functions in photosynthesis with their descriptions:

    <p>Photorespiration = Waste of energy due to O2 fixation Photoinhibition = Damage caused by excessive light intensity Rubisco = Enzyme that binds CO2 and O2 Stomata = Regulate gas exchange in plants</p> Signup and view all the answers

    What is the primary function of chromoplasts in plants?

    <p>Pigment synthesis for color</p> Signup and view all the answers

    Chloroplasts are only found in flowering plants.

    <p>False</p> Signup and view all the answers

    What type of pigments are primarily found in chloroplasts?

    <p>Chlorophyll</p> Signup and view all the answers

    Chromoplasts contain the carotenoid named ______, which contributes to the red color of tomatoes.

    <p>lycopene</p> Signup and view all the answers

    Match each type of plastid with its primary content:

    <p>Chloroplast = Chlorophyll Chromoplast = Carotenoids Leukoplast = Starch or oil or proteins Elaioplast = Oils</p> Signup and view all the answers

    Which of the following structures are chloroplasts bounded by?

    <p>Two membranes</p> Signup and view all the answers

    Galactolipids found in chloroplast membranes are a type of carbohydrate.

    <p>False</p> Signup and view all the answers

    The average size of chloroplasts is approximately ______ micrometers long.

    <p>5 to 10</p> Signup and view all the answers

    What is the primary function of the inner chloroplast membrane (ICM)?

    <p>Regulate the transport of materials between the cytoplasm and the stroma</p> Signup and view all the answers

    The stroma contains ribosomes that are exclusively free and not attached to any membranes.

    <p>False</p> Signup and view all the answers

    What is the most abundant enzyme on Earth involved in photosynthesis?

    <p>Rubisco</p> Signup and view all the answers

    The __________ is a complex of membranes and fluid matrix in chloroplasts that contains starch and lipid droplets.

    <p>stroma</p> Signup and view all the answers

    Match each chloroplast component with its function:

    <p>Rubisco = CO2 fixation Plastoglobules = Thylakoid function support Nuclear genes = Protein encoding delivered post-translationally Transit peptide = Targets proteins to chloroplast subcompartments</p> Signup and view all the answers

    Which proteins are encoded by chloroplast genes?

    <p>Only 100 proteins</p> Signup and view all the answers

    Translocation complexes in chloroplasts are named TOC and TIC.

    <p>True</p> Signup and view all the answers

    How many subcompartments are there in a chloroplast?

    <p>Six</p> Signup and view all the answers

    What is the primary function of thylakoids in chloroplasts?

    <p>Photosynthesis</p> Signup and view all the answers

    Thylakoids are made up of 50% proteins and 40% lipids.

    <p>True</p> Signup and view all the answers

    What are the small stacks of thylakoids called?

    <p>Grana</p> Signup and view all the answers

    The internal space of a thylakoid is known as the __________.

    <p>lumen</p> Signup and view all the answers

    Which of the following glycosphingolipids is largely found in the thylakoid membrane?

    <p>Monogalactosyldiglyceride</p> Signup and view all the answers

    Match the types of pigments with their colors:

    <p>Carotenoids = Orange Xanthophylls = Yellow Chlorophyll = Green</p> Signup and view all the answers

    Which type of plastid is primarily responsible for storing starch?

    <p>Amyloplast</p> Signup and view all the answers

    Which structure anchors chlorophyll in the lipid bilayer?

    <p>Phytol tail</p> Signup and view all the answers

    Chloroplasts develop from proplastids upon exposure to suitable light intensity.

    <p>True</p> Signup and view all the answers

    All chlorophylls have the same basic structure but differ by side groups on the porphyrin ring.

    <p>True</p> Signup and view all the answers

    What is the function of protochlorophyll found in etioplasts?

    <p>It is a chlorophyll precursor.</p> Signup and view all the answers

    The _______ is an organelle that contains circular DNA and is bounded by two membranes.

    <p>plastid</p> Signup and view all the answers

    What type of plastid lacks genuine thylakoids and contains a prolamellar body?

    <p>Etioplast</p> Signup and view all the answers

    What are proplastids, and where are they primarily found?

    <p>They are colorless organelles found in young and dividing plant cells.</p> Signup and view all the answers

    Match the plastid with its primary function:

    <p>Chloroplast = Photosynthesis Amyloplast = Storage of starch Chromoplast = Pigment synthesis Etioplast = Light response preparation</p> Signup and view all the answers

    The _______ are plastids that are involved in the production of pigments.

    <p>chromoplasts</p> Signup and view all the answers

    Which wavelengths of light do chlorophyll pigments primarily absorb?

    <p>400 to 500 nm and 650 to 700 nm</p> Signup and view all the answers

    Chlorophyll reflects green light, which is why plants appear green.

    <p>True</p> Signup and view all the answers

    What is the primary role of carotenoids in chloroplasts?

    <p>Secondary light collectors and protect against excess energy.</p> Signup and view all the answers

    Chemoautotrophs do not use light energy; they utilize __________ to produce organic compounds.

    <p>energy of mineral compounds</p> Signup and view all the answers

    Match the following types of organisms with their energy source:

    <p>Photoautotrophs = Use light energy to produce organic compounds Chemoautotrophs = Use energy from mineral compounds Heterotrophs = Require organic compounds for nutrition Prokaryotic photoautotrophs = Have lamellar structures for photosynthesis</p> Signup and view all the answers

    What is a key function of chloroplasts?

    <p>Photosynthesis</p> Signup and view all the answers

    Prokaryotic photoautotrophs contain chloroplasts.

    <p>False</p> Signup and view all the answers

    What are the main outputs of photosynthesis in chloroplasts?

    <p>O2 and carbohydrates.</p> Signup and view all the answers

    Study Notes

    Plastids

    • Plastids are organelles found in higher plants and algae, characterized by two membranes enclosing a stroma.
    • Several types exist, including chloroplasts, amyloplasts, and chromoplasts.
    • Electron microscopy is needed to see their ultrastructure.
    • Proplastids are small, colorless, and found in young plant cells.
    • These eventually develop into various plastid types depending on environmental conditions.
    • Etioplasts are found in leaves grown in the dark.
    • They lack thylakoids, instead having a prolamellar body and flattened vesicles.
    • Leucoplastids are enlarged proplastids primarily involved in storage.
    • Amyloplasts store starch, frequently found in plant roots and other storage tissues.

    Chloroplast Structure

    • Chloroplasts are abundant in leaf mesophyll cells, and in other green tissues of higher plants, mosses, and algae.
    • They contain pigments that give plants their green color.
    • Chloroplast morphology varies with species, cell type, and light intensity.
    • Higher plants typically have lens-shaped chloroplasts (2-4 µm wide, 5-10 µm long).
    • Chloroplasts are typically observed in the range of 20-40 per plant cell.
    • Chloroplast membranes include an outer and inner membranes, with an intermembrane space between them of 7-10 nm.
    • The stroma contains circular DNA, ribosomes, tRNA, enzymes for DNA replication, transcription, and translation, as well as light-absorbing pigments.
    • Thylakoid membranes are internal membrane sacs that form grana.

    Chloroplast Functions

    • Chloroplasts are responsible for photosynthesis: capturing light energy, fixing CO2 and producing carbohydrates in plants.
    • The process is the inverse of cellular respiration.
    • Chloroplasts also store carbohydrates as starch, and create other types of sugars.
    • Some Chloroplasts carry out photorespiration where it leads to O2 consumption and CO2 release which is a wasteful process.
    • Photoinhibition is another undesired function where too much light damages the photosystems.

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