University:
Indiana University South Bend
Course:
BIOL 211 | Biology
Academic year:

2023
Views:

72

Pages:

2
Author:

Minggu Pasti

Role of Envelope Proteins in Virus Insertion: Mechanisms of Host Cell Invasion and Infection Name : Minggu Menang Class : 19-A Important properties of viruses include : 1. Viruses have only 1 type of genetic material (RNA or DNA) which is enveloped by a protein envelope. The protein envelope is called the capsid. 2. For reproduction, only nucleic acid is required. 3. Viruses cannot grow or divide like other microbes. Virus Reproduction Viruses can only reproduce in living cells or tissues. Therefore, viruses infect bacterial cells, animal cells, or plant cells to reproduce. The way viruses reproduce is called proliferation or replication. In Bacteriophage, reproduction is divided into two types, namely the lytic cycle and the lysogenic cycle. In the lytic cycle, the virus will destroy the parent cell after successful reproduction, while in the lysogenic cycle, the virus does not destroy the bacterial cell but the virus integrates with the DNA of the bacterial cell, so that if the bacteria divide or multiply the virus also divides. In principle, the way viruses reproduce in animals and plants is similar to that of bacteriophage, namely through the phases of adsorption, synthesis, and lysis. a. Lytic infection / lytic cycle The lytic cycle goes through the following phases: 1. Adsorption and infection phase With the tip of its tail, the phage attaches to or infects a certain part of the bacterial cell wall, the area is called the receptor site (receptor spot). This area is unique to a particular phage, and other types of phages cannot attach to it. Bacterial invading viruses do not have enzymes for metabolism, but have lysozyme enzymes that function to damage or perforate the bacterial cell wall. 2. Replication phase (synthesis phase) Phage DNA conducts DNA formation (replication) using bacterial DNA as material, and forms a protein envelope. Hundreds of new DNA molecules of the virus complete with its envelope are formed. 3. Phage virus liberation phase - new phage / lysis phase After a new phage is formed, the bacterial cell will rupture (lysis), resulting in the release of a new phage. The number of these new viruses can reach about 200. The formation of bacteriophage particles takes about 20 minutes. b. Lysogenic infection / lysogenic cycle The lysogenic cycle goes through the following phases: 1. Adsorption and infection phase Phages attach to a specific place. The virus penetrates the bacteria and then secretes its DNA into the bacterial body. 2. Incorporation phase Viral DNA unites with bacterial DNA to form a prophage. In the prophage form, most genes are in the inactive phase, but at least one gene is always active. The active gene codes for a receptor protein that keeps some of the prophage genes inactive. 3. Cleavage phase When bacteria divide, the prophage also divides so that the two bacterial daughter cells also contain the prophage in their cells. This will continue as long as the bacterial cell containing the prophage divides.