Mitochondria and chloroplasts are semiautonomous organelles. 

Chloroplasts and mitochondria are called semiautonomous organelles due to the following reasons :

1. They have DNA, RNA, ribosomes and  other materials required to synthesize their own essential proteins.

2. They manufacture their own enzymes.

3. They can multiply and give rise to new organelles of the same kind. .

 

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Write the functions of nuclear envelope, nuclear matrix  and nucleolus.


The nuclear envelope performs the following functions :

1. It maintains the shape of the nucleus.

2. It keeps the nuclear contents in place and distinct from the cytoplasm.

3. It regulates the flow of materials into and out of the nucleus by active transport and outpocketing.

4. Its pores allow the exit of ribosomal subunits.

Functions of nuclear matrix :

1. It maintains the shape of the nucleus.

2. Chromatin fibres are anchored to nuclear matrix.

3. The machinery for various nuclear activities such as transcription and replication is associated with the matrix.

Functions of nucleolus :

1. It is the site for rRNA synthesis.

 

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Briefly describe lysosomes. 

Lysosomes were discovered by Christian de Duve in 1955. These are small membrane bound cytoplasmic vesicles which are rich in hydrolytic enzymes. These help in digestion. They may arise from smooth endoplasmic reticulum or Golgi complex. Lysosomes are usually spherical vesicles bounded by a single unit membrane enclosing a dense matrix. The matrix of the lysosomes contain enzymes mainly hydrolytic enzymes like lipases, proteases which works at acidic pH. The lysosome helps in the digestion of proteins, carbohydrates and lipids. The lysosomes are sometimes known as suicide bags as they help in the digetion of damaged cell or its parts. 

 

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Differentiate between of gram +ve and gram -ve bacteria.

Gram +ve bacteria

Gram -ve bacteria

1. They remain coloured blue or purple with Gram stain even after washing with absolute alcohol or acetone.

2. The cell wall is 100-200A thick, single layered.

3.  The bacteria are less resistant to antibiotics.

4. They are mostly non-pathogenic.

 

1. They don't retain the stain when washed with absolute alcohol.

2. The cell wall is 70-120Å thick, two layered.

3.They are more resistant to antibiotics.

4. They are mostly pathogenic.

 

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Descrbe  cilia or flagella.

Cilia and flagella are hair-like outgrowths of the cell membrane. Clia are smaller structures while the flagella are longer. They are formed basal bodies which are centriole-like structures. Both help in movement of cell. The cilium and flagellum are covered with plasma membrane. They have a core called axoneme which has nine pairs of doublets of radially arranged peripheral microtubules and a pair of centrally located microtubules. This arrangement of microtubules is called 9+2 array. The central tubules are covered by a sheath and are connected to each other. The sheath is connected to one of the tubules of the peripheral doublet by a radial spoke. There ate nine radial spokes in total. The linkers connect the doublets to each other.

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