1: What is function of the following organelles
Rough Endoplasmic, reticulum, ribosome, Golgi body.
2: What is the endosymbiotic theory? What evidence supports it?
1:
- Rough Endoplasmic Reticulum: It is responsible for the synthesis and packaging of proteins. It has ribosomes attached to its surface, which give it a rough appearance. It helps in the folding and modification of proteins before they are transported to their final destination.
- Ribosome: These organelles are responsible for protein synthesis. They read the genetic information carried by mRNA (messenger RNA) and use it to assemble amino acids into a specific sequence to form a protein.
- Golgi Body (Golgi Apparatus): It is involved in the processing, sorting, and packaging of proteins and lipids. It receives proteins from the rough endoplasmic reticulum, modifies them, and then directs them to their appropriate destinations within or outside the cell.
2:
The endosymbiotic theory proposes that eukaryotic cells (cells with a nucleus) evolved from a symbiotic relationship between primitive prokaryotic cells (cells without a nucleus), specifically the engulfment of one prokaryotic cell by another. This theory suggests that mitochondria and chloroplasts, both organelles found in eukaryotic cells, were once free-living prokaryotes that were engulfed by ancestral eukaryotic cells.
Evidence supporting the endosymbiotic theory includes:
- Mitochondria and chloroplasts have their own DNA, which is circular like the DNA found in prokaryotes.
- The size and structure of mitochondria and chloroplasts resemble prokaryotes.
- These organelles replicate independently, similar to prokaryotes undergoing binary fission.
- Antibiotics that target prokaryotic ribosomes also affect the ribosomes within mitochondria and chloroplasts.
- The similarities between prokaryotes and mitochondria/chloroplasts in terms of membrane structure and composition support the theory of endosymbiosis.
1:
- Rough Endoplasmic Reticulum: The rough endoplasmic reticulum (RER) is involved in the synthesis and processing of proteins. It has ribosomes attached to its outer surface, giving it a rough appearance. The ribosomes on the RER synthesize proteins that are then transported into the lumen of the RER for further modifications, such as folding and addition of carbohydrate groups.
- Ribosome: Ribosomes are cellular structures responsible for protein synthesis. They can be found either free-floating in the cytoplasm or attached to the rough endoplasmic reticulum. Ribosomes read the information in messenger RNA (mRNA) and use it to assemble amino acids into a polypeptide chain, which forms a protein.
- Golgi Body: The Golgi body, or Golgi apparatus, functions in processing, sorting, and modifying proteins and lipids that are produced by the cell. It consists of a series of flattened membrane sacs called cisternae. The Golgi body receives transport vesicles from the rough endoplasmic reticulum and modifies the proteins and lipids by adding or removing carbohydrate groups, lipids, or other modifications. It then sorts and packages them into vesicles for transport to their final destinations within the cell or outside of the cell.
2:
The endosymbiotic theory proposes that certain organelles, such as mitochondria and chloroplasts, were once free-living prokaryotic organisms that were engulfed by a host cell and developed a symbiotic relationship over time. This theory suggests that mitochondria and chloroplasts were once independent bacteria-like organisms that were engulfed by an ancestral eukaryotic cell, and through evolution, they became essential organelles in eukaryotic cells.
Evidence supporting the endosymbiotic theory includes:
1. Similarities in structure: Mitochondria and chloroplasts share striking similarities with bacteria in terms of size, shape, structure, and their own DNA.
2. Replication: Both mitochondria and chloroplasts have their own circular DNA, reproduce via binary fission (like bacteria), and have their own ribosomes for protein synthesis.
3. Independent DNA: Mitochondria and chloroplasts have their own genetic material, separate from the DNA found in the nucleus of eukaryotic cells. This genetic material is similar to bacterial DNA.
4. Double membrane: Both mitochondria and chloroplasts have double membranes, which could be explained by the engulfment of the original bacterial cells by the host cell.
5. Similar mechanisms: Mitochondria and chloroplasts have specific biochemical pathways and processes that are similar to those found in bacteria, providing further evidence of their shared evolutionary origins.
These pieces of evidence support the idea that mitochondria and chloroplasts were once free-living prokaryotes that became endosymbionts within eukaryotic cells, leading to the evolution of complex multicellular organisms.