Chloroplast | Structure, Chloroplast Function | [email protected]
It is this pigment that imparts a green color to plant parts, and serves to capture light energy. A detailed account of the structure and functions of. The chloroplast, found only in algal and plant cells, is a cell organelle that by existing as free-living cyanobacteria that had a symbiotic relationship with a cell, . Structure and function of mitochondria and chloroplasts. Mitochondria are found inside of your cells, along with the cells of plants. scientists think host cells and bacteria formed endosymbiotic relationships long ago, when individual host.
Function of Chloroplasts Chloroplasts are the part of plant and algal cells that carry out photosynthesis, the process of converting light energy to energy stored in the form of sugar and other organic molecules that the plant or alga uses as food. Photosynthesis has two stages. In the first stage, the light-dependent reactions occur. These reactions capture sunlight through chlorophyll and carotenoids to form adenosine triphosphate ATP, the energy currency of the cell and nicotinamide adenine dinucleotide phosphate NADPHwhich carries electrons.
The second stage consists of the light-independent reactions, also known as the Calvin cycle.
In the Calvin cycle, the electrons carried by NADPH convert inorganic carbon dioxide and to an organic molecule in the form of a carbohydrate, a process known as CO2 fixation. Carbohydrates and other organic molecules can be stored and used at a later time for energy. Chloroplasts are essential for the growth and survival of plants and photosynthetic algae. Like solar panels, chloroplasts take light energy and convert it into a usable form that powers activities.
Chloroplasts - Show Me the Green
However, a few plants no longer have chloroplasts. One example is the parasitic plant genus Rafflesia, which obtains its nutrients from other plants—specifically, Tetrastigma vines. Since Rafflesia gets all of its energy from parasitizing another plant, it no longer needs its chloroplasts, and has lost the genes coding for the development of the chloroplast over a long period of evolutionary time. Rafflesia is the only genus of land plant known to be lacking chloroplasts.
Structure of Chloroplasts Chloroplasts, like mitochondria, are oval-shaped and have two membranes: Between the outer and inner membrane is a thin intermembrane space about nanometers wide.
The space within the inner membrane is called the stroma. While the inner membranes of mitochondria have many folds called cristae to absorb surface area, the inner membranes of chloroplasts are smooth. Instead, chloroplasts have many small disc-shaped sacs called thylakoids within their stroma.
In vascular plants and green algae, the thylakoids are stacked on top of one another, and a stack of thylakoids is called a granum plural: The thylakoids contain chlorophylls and carotenoids, and these pigments absorb light during the process of photosynthesis.
Light-absorbing pigments are grouped with other molecules such as proteins to form complexes known as photosystems. The two different kinds of photosystems are photosystems I and II, and they have roles in different parts of the light-dependent reactions. In the stroma, enzymes make complex organic molecules that are used to store energy, such as carbohydrates. The stroma also contains its own DNA and ribosomes that are similar to those found in photosynthetic bacteria.
For this reason, chloroplasts are thought to have evolved in eukaryotic cells from free-living bacteria, just as mitochondria did.
pdl-inc.info: Cell Structure: Chloroplasts
Billions of years ago, a eukaryotic cell engulfed a cyanobacteria, which survived inside the cell, and later on evolved to become the chloroplast. Plants and certain algae are characterized by the unique ability of photosynthesis, the synthesis of food molecules in the presence of sunlight.
This ability is conferred through the presence of specialized organelles called chloroplasts, commonly referred to as the 'kitchens' of plant cells. Chloroplasts are plastids that contain a network of membranes embedded into a liquid matrix, and harbor the photosynthetic pigment called chlorophyll.
It is this pigment that imparts a green color to plant parts, and serves to capture light energy. A detailed account of the structure and functions of chloroplasts has been provided below. Structure Chloroplasts are located in the parenchyma cells of plants as well as in autotrophic algae.Chloroplasts - Structure
Although their dimensions are almost similar in all plants, the algal chloroplasts show a variation in their size as well as shape.
The major components of a chloroplast are as illustrated and explained below.
Chloroplast - Definition, Function and Structure | Biology Dictionary
Envelope The chloroplast envelope is double-membrane structure comprising an outer and an inner membrane. Each of these membranes is a phospholipid bilayer, and is 6 - 8 nm thick. A 10 - 20 nm thick space present between the two membranes is known as intermembrane space. Stroma The aqueous matrix present inside this double-membrane envelope is called the stroma. The internal components as well as several solutes are dispersed into the stroma.
The stroma is especially rich in proteins, and contains several enzymes necessary for vital cellular processes. The chloroplast DNA is also present in the stroma along with ribosomes and other molecules required for protein synthesis. Starch synthesized through photosynthesis is stored in the stroma in the form of granules. Thylakoids In addition to the two membranes that form the envelope, chloroplasts contain a third internal membrane system called thylakoid membrane.
Thylakoids are the internal, membrane-bound compartments formed by such thylakoid membranes. The internal portion of the thylakoid is called the thylakoid lumen, and contains plastocyanins and other molecules required for the transport of electrons. Grana Some of the thylakoids are arranged in the form of discs stacked one above the other.
These stacks are termed grana, and are connected to each other through inter grana thylakoids and stroma thylakoids. Photosystems Present in the thylakoid membranes, these are the structural and functional units for harnessing solar energy.