What are plastids

\( \newcommand\) • • • • • • • • • • • What do plants have to do that animals don't? Many plant cells are green. Why? Plant cells also usually have a distinct shape. The rigid exterior around the cells is necessary to allow the plants to grow upright. Animal cells do not have these rigid exteriors. There are other distinct differences between plant and animal cells. These will be the focus of this concept. Special Structures in Plant Cells Most organelles are common to both animal and plant cells. However, plant cells also have features that animal cells do not have: a cell wall, a large central vacuole, and plastids such as Plants have very different lifestyles from animals, and these differences are apparent when you examine the structure of the plant cell. Plants make their own food in a process called photosynthesis. They take in carbon dioxide (CO 2) and 2O) and convert them into sugars. The features unique to plant cells can be seen in Figure In addition to containing most of the organelles found in animal cells, plant cells also have a cell wall, a large central vacuole, and plastids. These three features are not found in animal cells. The Cell Wall A cell wall is a rigid layer that is found outside the Microtubules guide the formation of the plant cell wall. Cellulose is laid down by enzymes to form the primary cell wall. Some plants also have a secondary cell wall. The secondary wall contains a lignin, a secondary cell component in plant cells that have completed ...

Organelles, called plastids, are the main sites of photosynthesis in eukaryotic cells. Chloroplasts, as well as any other pigment containing cytoplasmic organelles that enables the harvesting and conversion of light and carbon dioxide into food and energy, are plastids. Found mainly in eukaryotic cells, plastids can be grouped into two distinctive types depending on their membrane structure: primary plastids and secondary plastids. Primary plastids are found in most algae and plants, and secondary, more-complex plastids are typically found in plankton, such as diatoms and dinoflagellates. Exploring the origin of plastids is an exciting field of research because it enhances our understanding of the basis of photosynthesis in green plants, our primary food source on planet Earth. Where did plastids originate? Their origin is explained by endosymbiosis, the act of a unicellular heterotrophic protist engulfing a free-living photosynthetic cyanobacterium and retaining it, instead of digesting it in the food vacuole (Margulis 1970; McFadden 2001; Kutschera & Niklas 2005). The captured cell (the endosymbiont) was then reduced to a functional organelle bound by two membranes, and was transmitted vertically to subsequent generations. This unlikely set of events established the ancestral lineages of the eukaryote supergroup "Plantae" (Cavalier-Smith 1998; Rodriguez-Expeleta et al. 2005; Weber, Linka, & Bhattacharya 2006), which includes many photosynthetic algae and land plants. The...

Cell Wall, Plasma Membrane, and Middle Lamella Figure \(\PageIndex\): The image above shows cells in the epidermis of a red pepper. Two locations are circled and labeled as plasmodesmata. In each of these circles, there is a section of the cell wall that appears to be missing. This is where a section of the plasma membrane traverses through a channel in the middle lamella and cell walls of both cells. Photo by Maria Morrow, The Nucleus Figure \(\PageIndex\): The large, golden, globose structure is an onion cell nucleus, magnification 3000x. Berkshire Community College Bioscience Image Library, CC0, via Wikimedia Commons. Chloroplasts Chloroplasts are plastids that contain green pigments called chlorophylls. Figure \(\PageIndex\): A diagram of chloroplast anatomy. There are two membranes, the outer and inner membrane, that enclose this structure. Within, there are stacks of flat discs. Each stack is called a granum and each individual disc is a thylakoid. The grana float within a jelly-like matrix called the stroma. Artwork by Nikki Harris, Chromoplasts Chromoplasts are plastids that do not contain chlorophyll, but do contain other pigments, such as carotenoids. Carotenoid pigments reflect colors like yellow, orange, and red. Figure \(\PageIndex\): In this image of red pepper epidermal cells, the chromoplasts are larger and easier to distinguish. Each cell is filled with circular, red discs. These are chromoplasts that contain carotenoids. Photo by Maria Morrow, Leucoplasts...

What are Plastids? Plastids are the largest cell organelle in plants. These are responsible for photosynthesis and act as storage devices for starch and help in the synthesis of various molecules like fatty acids and terpene. Types of Plastids and Functions of Plastids Plastids are further divided into 3 types that have different functions and some have biological pigments as well. • 1. Leucoplasts • 2. Chromoplasts • 3. Chloroplasts Leucoplasts These colourless Plastids possess internal lamellae and do not contain photosynthetic and grana pigments. These are found near cells that are not exposed to sunlight like underground stems, seeds, rhizomes, roots and are used to store food materials. These can be subdivided into 3 categories: • i) Proteinoplast or Aleuroplast – Responsible for storing proteins. • ii) Amyloplast – Store and synthesize carbohydrates. • iii) Elaioplast or Lipidoplast or Oleoplast – These store oils and lipids. Chromoplasts Coloured Plastids found in petals and fruits having fat-soluble carotenoid pigments are Chromoplasts. These are non-green in colour and give part of plant colours like red, yellow, orange. The various colours imparted help in attracting pollinators. If you have ever seen a non riped tomato or chill, it is green in colour. These turn red after ripening due to the replacement of chlorophyll molecules in chloroplasts (lycopene in tomatoes and capsanthin in chillies) and that is how chloroplasts are changed to chromoplast. Chloroplasts ...

\( \newcommand\) • • • • • • Plastids may derive from cyanobacteria engulfed via endosymbiosis by early eukaryotes, giving cells the ability to conduct photosynthesis. Key Points • Chloroplasts, chromoplasts, and leucoplasts are each a type of plastid. • Plastids in eukaryotes derive from primary endosymbiosis with ancient cyanobacteria. • Chlorarachniophytes are a type of algae that resulted from secondary endosymbiosis, when a eukaryote engulfed a green alga (which itself was a product of primary endosymbiosis with a cyanobacterium). • Plastids share several features with mitochondria, including having their own DNA and the ability to replicate by binary fission. Key Terms • chloroplast: an organelle found in the cells of green plants and photosynthetic algae where photosynthesis takes place • thylakoid: a folded membrane within plant chloroplasts from which grana are made, used in photosynthesis • plastid: any of various organelles found in the cells of plants and algae, often concerned with photosynthesis Plastids Some groups of eukaryotes are photosynthetic: their cells contain, in addition to the standard eukaryotic organelles, another kind of organelle called a plastid. There are three type of plastids: chloroplasts, chromoplasts, and leucoplasts. Chloroplasts are plastids that conduct photosynthesis. Chromoplasts are plastids that synthesize and store pigments. Leucoplasts are plastids located in the non-synthetic tissues of a plant ( e.g., roots) and generally sto...