Amyloplast Function – Amyloplasts are organelles dedicated to the accumulation of starch in storage cells. They appear like the chloroplasts of Proplastiden and are bound by a double membrane. For more details, just refer to our explanation about the function of amyloplasts, Definition, Features, Complete below.

Definition of Amyloplast

Amyloplasts are organelles dedicated to the accumulation of starch in storage cells. They appear like the chloroplasts of Proplastiden and are bound by a double membrane.

Amyloplasts of some starchy tissues, such as from the endosperm of cereals, remains colorless under the action of light, while others, z. B. from potato tubers, under the action of light to form chloroplasts and chloroplasts in old tobacco leaves become amyloplasts.

In the year 1976, the amyloplast shell is believed to be a chloroplast like with the same membrane transporter, except that in amyloplasts, triosephosphate is converted to amyloplasts to provide a substrate for starch synthesis, from chloroplasts.

It has been shown that the inner membranes of young amyloplasts of barley and maize are highly infaginated and form tubules, lamellar stroma or vesicle.

Starch granules containing amyloplasts are very fragile and initial attempts to isolate intact amyloplasts for absorption studies have been very difficult..

Due to the difficulty of obtaining high yields of intact amyloplasts from starchy tissues, Other methods have been used to determine the compartmentalization of starch biosynthetic enzymes between amyloplasts and cytosol.

Specific enzyme immunolocalization is the most direct approach for determining enzyme compartmentalization. Kim et al.200 reported that AGPase in potato tubers appears to be closely related to starch granules when observed at microscopic light levels, indicating that it is a plastidlocalized enzyme.

This is confirmed by Kram et al.201, which showed by immunogold label and electron microscopy that the protein responding to increased antibody to AGPase from spinach leaves was distributed throughout the potato tuber amyloplast stroma..

They also reported that starch-branching enzymes were localized in amyloplasts in close contact with the surface of starch granules.. 200 Miller and Chourey202 reported that AGPase in the corn endosperm was also localized in amyloplasts, but the protein reacts with antibodies induced by SH2 and BT2.

AGPase large and small subunits are also present in the endosperm cell wall. Some proteins that react with antibodies are also distributed throughout the cytosol. 202 Proteins that react on the cell wall are not detected by antibodies directed at spinach leaves..

Villand and Kleczhowski203 described that in wheat endosperm specific antibodies to AGPase react with proteins in both the cytosol and amyloplastic.

AGPase in the cytosol occurs in a cluster-like pattern. They suggested that the amyl-located AGPase could be a “leaf-type” isozyme..

Barley endospermic studies only characterized amyloplast stromal proteins in potato tubers. 203 Differences in the AGPase compartment between potato tubers and cereal endosperms Villand and Kleczhowski suggest that the cereal endosperm has an alternative pathway for starch biosynthesis with ADP-Glc converted to amyloplasts to provide a substrate for starch synthesis..

Read Also : Chromoplast Function

Amyloplast Function

Amyloplasts are organelles found in plant cells. Amyloplasts are also plastids that produce and store starch in internal membrane compartments.

Menurut Journal of Experimental Botany, The main function of amyloplasts is as follows in the table ;

Amyloplasts are unpigmented or colorless organelles known as plastids, which converts glucose to starch and stores it in the stroma.

Amyloplasts are also responsible for starch storage in the cell stroma, especially in tubers and roots like potatoes. Eighty-five percent of Amyloplast protein is used for metabolic processes, energy storage, and unknown processes.

However, other proteins facilitate secondary and tertiary processes in amyloplasts. Menurut Journal of Experimental Botany, 289 proteins have been identified that aid in various processes in amyloplast cells.

These functions include nitrogen and sulfur metabolism, carbohydrate metabolism, cleavage of the cytoskeleton or plastids and facilitate other protein-associated reactions.

Amyloplasts also aid in nucleic acid reactions, as well as in transportation, signaling, and various other processes. More than half of protein helps metabolism and responds to stress.

Amyloplasts are also characterized by enzymes that support sulfur metabolism, amino acids and nucleic acids.

Function 12 percent protein unknown; However, understanding the biochemistry and flexibility of amyloplasts has led to a better understanding of plastid function in general.

Characteristics of Amyloplasts

Amyloplasts are responsible for the overall starch synthesis in plants. Amioplasts have the following characteristics::

1. Found in plant parenchyma tissue, which form the outer and inner layers of the stem and root; middle leaf layer; and soft tissue in fruits.
2. Being in a tissue that does not undergo photosynthesis, mis. B. root or seed endosperm. Amyloplasts are also present in special cell types at the root apex; Sel Collu- Mella
3. Amyloplasts develop from proplastids and share the process of binary fission. Mature amyloplasts produce an inner membrane that creates compartments for starch storage.
4. The size of the amyloplast itself depends on the amount of starch stored. Starch is a polymer of glucose that exists in two forms: amylopectin and amylose.
5. Starch grains consist of neatly arranged amylopectin and amylose molecules. The size and number of starch granules in amyloplasts varies depending on the plant species. Some contain single ball grains, while others contain many small details.

Type – Types of Amyloplasts

Plastids are organelles that work mainly in the synthesis of nutrients and the storage of biological molecules. Although there are different types of plastids specialized to work or perform certain roles, they have some common characteristics.

Plastids are found in the cytoplasm of the cell and are surrounded by a double lipid membrane. Plastids also have their own DNA and can replicate independently of the rest of the cell. Some plastids contain pigments and are colored, while others have no pigment and are colorless.

Plastids develop from immature, undifferentiated cells called proamyloplasts. Proamiloplasts grow into four special types of plastids: chloroplast, chromoplast, gerontoplast, dan leucoplast.

• Chloroplast

Green plastids are responsible for photosynthesis and energy production through glucose synthesis. They contain chlorophyll, green pigment that absorbs light energy.

Chloroplasts are generally found in specialized cells called protective cells located in the leaves and stems of plants. Protective cells open and close tiny pores called stomata to allow the gas exchange necessary for photosynthesis.

• Chromoplast

Plastids that have various colors (colorful) responsible for the production and storage of cartenoid pigments. Carotenoids produce red pigment, orange and yellow.

Chromoplasts are found mainly in ripe fruit, flower, Angiosperms roots and leaves. They are responsible for coloring the plants on the plants, used to attract pollinators.

Some of the chloroplasts found in immature fruits become chromoplasts when the fruit is ripe. This color changes from green to a carotenoid color, indicates that the fruit is ripe.

The change in leaf color in autumn is caused by the loss of chlorophyll from the green pigment, which reveals the color of the carotenoids at the base of the leaf. Amyloplasts can also be converted into chromoplasts by making the first transition to amylochromoplasts (starch containing plastids and carotenoids) and then become chromoplast.

• Gerontoplas

The plastids develop from the degradation of chloroplasts, what happens when plant cells die. In the process, chlorophyll decomposes which then becomes chloroplast, leaving only the cartotinoid pigments in the cells resulting from the gerontoplast.

• Leukoplas

Plastids do not have color and function to preserve nutrients. They are usually found in tissues that do not undergo photosynthesis, such as roots and seeds.

Types of leukoplasts, among them as follows :

Amyloplast: leukoplast which converts glucose into starch which is then used for storage. Starch is stored in the form of granules in amyloplast tubules, fruits, seeds, and stem.

Dense starch granules cause amyloplasts to settle in plant tissues in response to gravity. This pushes growth downwards.

Amyloplasts also synthesize transient starch. This type of starch is temporarily stored in the chloroplast and is used as energy at night when photosynthesis is not taking place. Transient starch is found mainly in tissues where photosynthesis occurs, like a leaf.

Elaioplas: leucoplans that synthesize fatty acids and store oil in microcompartments filled with lipids called plastoglobulins. They are important for the correct development of pollen.

Ethiopian: light sequestered chloroplasts that do not contain chlorophyll, but have precursor pigments for chlorophyll production. After exposure to light, chlorophyll is produced and etioplast becomes chloroplast.

Proteinoplasts: Also known as aleuroplasty, These leucoplasts store protein and will usually be in the seed.

Thus our discussion of the Amyloplast Function Material. Read also Vacuole Function. Hope it's useful.

The post Fungsi Amiloplas appeared first on YukSinau.co.id.