| Talk in general about plastids. | Several types found in plants, bounded by two membranes that enclose a stroma. seen by LM but ultrastructure is only seen by EM, in stroma there are several circular DNA molecules, ribosomes, tRNA and all enzymes that are associated with DNA, In addition to membrane bounded sacks that comprise the photosynthesis chain and light absorbing molecules (pigments), they proliferate by binary fission. |
| Talk about the different types of plastids. | Etioplast, Chloroplast, Chromoplast, proteoplast, and amyloplast, are all plastids derived from the same proplastid, but occupy different ultrastructures and functions.
Elaioplastids (oil) poteoplastids (proteins) |
| Talk about proplastids. | small colorless organelles containing irregular membranous structures that correspond to primitive thylakoids, found in meristems and have two membranes inner one is origin of thylakoid membranes. Their differentiation into different plastid types is light intensity dependent, |
| Talk about Etioplasts. | etioplasts prevalent in leaves that grow in dark contain yellow pigments named protochlorophyll which is a chlorophyll precursor. ellipsoid structure and do not contain genuine thylakoids. Instead, they have a prolamellar body and certainly flattened vesicles that are considered as primary thylakoids, developed into chloroplast upon light exposure |
| Talk about Leucoplast. | Enlarged proplastids found in internal tissues as well as epidermis, amyloplast is an example abundant in storing tissues such as roots and play a role in gravity detection (growth direction) almost destroyed by accumelation of large starch granules. Outer membranes is the only remained element that delimits the stroma which contains several starch granules composed of concentric layers of starch, even outer membrane could rupture when granules become bigger such as in potato tuber. |
| Talk about chromoplast. | Elongate irregular structures containing carrotenoids responsible for yellow red and orange color of plant organs such as roots, petals and fruits, carrot roots orange color is due to orange chemicals carotenoids (beta) that are present in chromoplast, tomato color is due to lycopene rich chromoplasts pegments are form of lipid droplets in chromoplast stroma. |
| Talk in general about chloroplast | Found in green tissues of higher plants, especially abundant in leaf of mesophyll cells. Found in bryophytes and algae, rich in chlorophyll pigments which are responsible for green color but they also contain different types of pigments.
Variable in size and shape, number depending on species cell type and physiology. |
| Talk about chloroplast structure in general. | Lens shaped approximatly 2-4 microm diameter and 5-10 microm long, numbering 20-40 per cell simpler plants contain one or few chloroplasts irregular in shape, by contrast vascular plants have many chloroplasts. |
| Talk about chloroplast membrane. | Two membranes bounded, thick membranes with wide intermembrane space outer chloroplast membrane (OCM) like OMM contains porins which makes it permeable to a variety of molecules, other proteins are also present in the OCM. ICM is far less permeable, and has different properties since they differ in composition, so the ICM regulates transport of molecules from stroma to cytosol and vice versa |
| Talk about chloroplast stroma. | Contain a complex system of membranes whose structure, organization and density differ depending on species cell types and physiology. Called lamella suspended in stroma.
Stroma contains a variety of particles such as strach granules resulting from polymerization of glucose produced by photosynthesis and lipid droplets. There are several copies of circular DNA and its accessory molecules, (ribosomes may be free or attached to thylakoids, In addition there is Rubisco (ribulose biphosphate carboxylase) which is the most abundant enzyme on earth, which catalyze CO2 fixation necessary for glucose formation. |
| Talk about the protein import to chloroplast. | Similar to mitochondria up to 100 proteins are encoded by chloroplast DNA, however proteins are also translated by free ribosomes of the cytosol and imported to one of the six subcompartments of the chloroplast (ICM, OCM, Intermembrane space, lamella lumen, lamella membrane, stroma)
Proteins have a very specific address code that takes it towards the specific subcompartment where it will do its job (transported by translocases TOC (outer membrane) and TIC (inner protein) in addition it involved chaperons that help folding and processing in stroma.) address code is at N terminous. |
| Talk in general about thylakoids. | Inner membrane system has disk-shaped sacks called thylakoids, bounded by a lipid bilayer and arranged in orderly piles called grana (granum means sack) Each pile is about 40 60 grana, having 2 to 100 thylakoids.
Certain thylakoids called stroma thylakoids extend laterally and interconnect grana to one another.
Role is photosynthesis (reduction of NADP) and photophosphorylation |
| Talk about thylakoid membrane. | Lipid bilayer contains a little amount of phospholipids and a high amount of specific glycolipids called monogalactosyl diacylglycerol. Two fatty acids of this molecule are unsaturated so membrane is fluid enough to allow interaction between photosynthetic chain elements, Among the membrane proteins the ATP synthase is present(cF1 stromal face cF0 intrinsic) organization is similar to the IMM one, intermembrane space of thylakoid is called lumen. |
| Talk about the photosynthetic chain. | Metabolic chain present in thylakoids membrane which also contains light absorbing pigments named chlorophyll, carotenoids, and xanophylls. |
| Talk about chlorophylls. | Found in thylakoid membrane Structure is the same among different types, is the same consists of Mg containing green porphyrin ring (similar to the iron of Hb) linked to a phytol tail (hydrocarbon tail) anchored in the lipid bilayer, all chlorophylls have the same structure but differ by side groups of the porphyrin ring.
They absorb light because of their alternating double bond resulting in the electronic cloud, but they do not absorb all wavelengths, specific absorption peaks, they reflect green light making the plants green. |
| Talk about carotenoid pigments in chloroplast. | Found in thylakoid membrane serve as secondary light collectors, terpenes, and absorb light in addition they absorb excess energy in order to prevent formation of O2 singlet that destroys biological molecules, all this diversity in light absorbers helps in effieciently have a better light absorbing spectrum.
They are complexed with proteins named photosynthetic systems (PSI and PSII) |
| Talk about Autotrophs and Heterotrophs ways of survival. | Organisms having chloroplasts are photoautotrophs capable of making their own organic compounds by photosynthesis and light energy while chemoautotrophs do not have chloroplast, and heterotrophs require onrganic compounds produced by autotrophs to grow, prokaryotic photoautotrophs do not have chloroplasts instead have lamella. |
| Talk about photosynthesis. | Absorption of light and fixation of CO2 producing glucose and O2 which is the reverse of mitochondrial cell respiration, oxidation reduction reactions which involve proton and electron transfer from H2O to CO2 which is therefor reduced into carbohydrate., glucose produced is used to synthesize lipids proteins and nucleic acids for plant cells. Two phases light dependent phase and light independent one |
| Talk about light dependent phase of photosynthesis. | In thylakoid by photosynthetic chain elements resposible for photolysis, which is splitting of H2O from the thylakoid lumen into O2 protons and electrons. Resulting protons and electrons are carried by Coenxzymes (NADP--NADPH) simuntanously there is generation of a proton gradient in the thylakoid lumen which leads to the activation of ATP synthase which will convert ADP to ATP towards the stroma in a process called photophosphorylation. |
| Talk about light independent photosynthetic reactios. | ATP and NADPH are used to reduce CO2 into glucose through Calvin cycle in stroma, which occurs within the chloroplast while other compartments get their ATP from mitochodria cell respiration.
Includes Rubisco that fixes atmospheric CO2 on a substrate which is ribulose biphosphate. Glucose is finally polymerized and converted into fructose and sucrose for distribution to all cells of the plant. |
| Talk about the undesired functions of chloroplast. | Photorespiration, leads to consumption of O2 and release of CO2 cosidered as a waste of energy.
Results from the non specificity of Rubisco |
