zigya tab
What is a mesosome in prokaryotic cell? Mention the functions that it performs.

Mesosome is a specialised membranous structure formed by the invagination of plasma membrane in prokaryotes. These extensions are
in the form of vesicles, tubules and lamellae. 

The mesosome performs the following functions -:

1. Help in respiration, secretion processes by  increasing the surface area of the plasma membrane and enzymatic content.

2. Helps in DNA replication and distribution to daughter cells. 

4. Help in cell wall formation.

 

349 Views

Advertisement

Multicellular organisms have division of labour. Explain.


Unlike unicellular cells which have only one cells that perform all the functions, multicellular organisms have many cells. In multicellular organisms the cells perform specific functions. All the cell performing similar function are organized into group to form tissues. This is called division of labour as different functions are performed by different group of cells. For example the nervous tissue conducts signals to all parts of the body while epitheliat tissur forms the covering of the body and provides protection.  

 

284 Views

Advertisement
What are the characteristics of prokaryotic cells?

Characteristics of Prokaryotic cell are as follows:

1. The nucleus is not bounded by a membrane.

2. Their genetic material is naked and present in the form of nucleoid in the cytoplasm.

3. They are generally smaller and divide more rapidly as compared to the eukaryotic cell.

4. They are usually surrounded by cell wall except for mycoplasma.

5. Besides genomic DNA many prokaryotic cell have small circular DNA called plasmids outside the genomic DNA.

6. Eukaryotic organelles or membrane bound organelles are not found in the prokaryotic cells. The ribosomes found in these are of 70S type. 

7. Mesosomes which are the invaginations of plasma membrane may be present.

8. They have special inclusion bodies. 

 

 

 

216 Views

 Cell is the basic unit of life. Discuss in brief.

A single cell is capable of performing all the functions and life process. It can perform all the metabolic activities required to sustain life. The organ and tissues in multicellular organisms is made up of cells.The cell is the smallest unit that can survive independently and perform all the vital functions of life. Hence, cells are called basic unit of life

331 Views

What is a centromere ? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.

Centromere is a primary constriction present in the chromosome. It provides orientation to chromosome and marks the space for attachment of chromosomal fibres during cell division. The centromere has disc shaped structures called kinetochores on the sides of it.

Depending upon the location of centromere in a chromosome, the chromosome is classified  into the following four types :

(a) Telocentric: Centromere is present at the terminals.

(b) Acrocentric: Centromere is present near the terminals resulting in two short arms and two long arms. 

(c) Sub- metacentric : Centromere divides the chromosomes into two unequal arms. It lies either below centre or above centre.

(d) Metacentric : Centromere divides the chromosomes into two equal arms with the centromere in the middle.

 

 

What is a centromere ? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.

 

What is a centromere ? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.

 

1287 Views

Advertisement