What structures are present in a bacterial cell, but not in a plant or animal cell?

The process of transcription transcribes the sequence of the bases of genes present on DNA to mRNA which acts as a messenger molecule for the protein synthesis.

The process of transcription is mediated by the presence of enzymes which includes the main transcription enzyme called RNA polymerase. RNA polymerase attaches nucleotides to RNA strand.

The transcription process initiates in three stages: initiation, elongation and termination.

The initiation process begins when RNA polymerase binds to the promoter nucleotide sequence which is present at the start site or the upstream on DNA towards 5' end.

Thus, Option-B is the correct answer.

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3 years ago

The various parts of the endomembrane system serve different functions in the cell. In this activity, you will identify the role

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Answer:

1. protein synthesis - (b) rough ER

2. protein modification and sorting - (c) Golgi apparatus

3. macromolecule digestion - (d) lysosomes

4. lipid synthesis - (a) smooth ER

5. autophagy - (d) lysosomes

6. cisternal maturation - (c) Golgi apparatus

7. calcium ion storage - (a) smooth ER

8. poison detoxification - (a) smooth ER

Explanation:

Rough ER or rough endoplasmic reticulum with the help of ribosomes is responsible for protein synthesis and their subsequent transport to various other parts of the cell that is why both these organelles are also known as protein factory.

Soon after proteins are synthesized with the help of rough ER, they are transported to another network of organelle known as golgi apparatus. In golgi apparatus, the nascent protein is further modified and sorted. Modification and sorting of proteins help in identifying their final destination i.e. whether the protein is meant for mitochondria or plasma membrane or some other organelle. Maturation of cisternae also takes place in golgi apparatus.

Smooth ER or smooth endoplasmic reticulum is responsible for lipid synthesis, storage of calcium ions and poison detoxification. Most of the steroid hormones, triglycerols etc. are synthesized in the smooth endoplasmic reticulum. Smooth ER also stores calcium ions so that whenever they are required they can be sequestered back into the cytosol. Poison detoxification occurs in the smooth ER of liver because the enzymes present in the liver are capable of converting such hydrophobic substances into hydrophilic substances so that they could be easily secreted out of the body.

Lysosome is the organelle which is responsible for macromolecule digestion and autophagy. Lysosomes have very low pH and a lot of hydrolyzing enzymes which can easily digest macromolecules. Autophagy is a self degradable process in which damaged cells are eaten or destroyed by lysosomes so that their macromolecules could be broken down into their monomers so that they can be reused by our body.

3 0

3 years ago