Chloroplast is the part of the plastid that contains the genetic material in the form of DNA and RNA. According to the explanation in the book “Biology Jl. 1 Ed. 5”, chloroplasts are known to contain many pigments that can make fruits and flowers have many colors.
Coroplasts also have the green pigment chlorophyll which along with enzymes and other molecules is useful for photosynthesis. This organelle has a lens-like shape with a size of 2 x 5 m. These organelles are usually found in leaf and other organs in green plants and eukaryotic algae.
Chloroplast Structure
Chloroplasts are known to be composed of several carbohydrate, fat, protein, chlorophyll, carotenoids, DNA, and RNA. The parts of the chloroplast are as follows.
1. Space Between Membranes
In the book “Smart Learning Biology for Class XI” it is explained that chloroplasts have two membrane units such as mitochondria. Each unit is trilaminar (consisting of three layers) between which there is an intermembrane space.
The space between the membranes is useful for separating the broad and inner membranes. The size of this membrane is approximately 10 cm.
2. Outer Membrane
The second structure of the chloroplast is the broad membrane. This component functions to regulate the entry and exit of solid or liquid materials on the membrane.
3. Inner Membrane
The third part of the chloroplast is the inner membrane. This part is often referred to as the main membrane. Its function is to limit the stroma and cytosol
4. Tylakoid
The thylakoids are a membrane system composed of flattened sacs. The thylakody is the site of the light reactions. This chloroplast structure is also responsible for capturing the sun in the process of photosynthesis.
In the book “Biology Jl. 1 Ed. 5”, explained that the thylakoids divide the chloroplast into two parts, namely the thylakoid space and stroma.
5. Stroma
The stroma is the fluid outside the thylakoids. This section serves as a dark reaction site and to store the products of photosynthesis in the form of starch.
6. Money
The grana are stacks of thylakoids that form a structure. Because it is a stack of thylakoids, this section also functions as a light reaction site.
7. Ribosomes
Ribosomes are the site for cells to make proteins. Quote from sehatq.com, ribosome function in plant cells and other living things, namely to make proteins and carry out protein synthesis in cells. Cells need to be produced in order to speed up biological processes.
Each ribosome is composed of RNA and protein. Ribosomes consist of two RNA-protein subunits, namely large and small subunits.
The two sub units are located overlapping with the large unique sub at the top. In the middle of the sub unit is RNA. Therefore, if described, the ribosome has a shape like food hamburger.
Each sub unit turns out to have a different function. The function of the small subunit of the ribosome is to read the message given by mRNA for amino acids. While the function of the large sub unit is to form peptide bonds.
8. Plasmid DNA
The next chloroplast structure is the DNA plastid. The function of this part is to replicate chloroplasts and help the chloroplast cell division.
9. Plastoglobula
This part is a chemical compound present in chloroplasts. Plastoglobules are arranged on globular -shaped lipis.
10. Pati
Starch is an organic compound of starch which is a product of photosynthesis in starch plant.
Functions of Chloroplasts
According to the explanation in the book “Smart Learning Biology for Class XI”, there are two functions of chloroplasts, namely:
- Plays a role in photosynthesis, namely in the light reactions (phosphorylation and photolysis) and the dark reactions in the formation of glucose.
- Plays a role in the process of protein synthesis (compiling chloroplasts).
Photosynthesis Process
It has been mentioned earlier that one of the functions of the chloroplast is to help the process of photosynthesis. The definition of photosynthesis is a physical and chemical process that generally occurs in plants. Chemically, the process of photosynthesis occurs through reactions such as the following:
6H2O + 6CO2 + light => C6H12THE6 (glucose) + 6O2
If we look at this reaction, we can understand that photosynthesis produces glucose and water. To produce these substances, plants need carbon dioxide, water and sunlight.
Although it looks simple, it turns out that photosynthesis occurs through two fairly long processes, namely the light and dark reactions. Quoting from “Photosynthesis Teaching Materials” by Ir. I. Wayan Wiraatmaja, MP, the following is the explanation.
Bright Reaction
In simple terms the light reaction can be interpreted as a process of photosynthesis that requires light. This reaction takes place in the grana. In the light reaction, light energy is converted into chemical energy and produces oxidants.
Dark Reaction
The dark reaction is a process of photosynthesis that does not require light but still requires carbon dioxide. This reaction occurs in the stroma. In the dark reaction, there is a cyclical reaction that forms sugar from the basic ingredients of carbon dioxide and energy (ATP and NADPH).
The energy used in the dark reactions is obtained from the light reactions. Therefore, the dark reaction occurs after the light reaction is complete. The dark cycle process does not require sunlight which aims to convert compounds containing carbon atoms into sugars.
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