Cell The Unit of Life Test - 30

Endoplasmic reticulum helps in mechanical support and enzyme transport. Smooth endoplasmic reticulum synthesises lipids which form an integral part of the plasma membrane and helps in mechanical support. The rough endoplasmic reticulum synthesises enzymatic proteins which are transported to Golgi apparatus for further modification.

The ribosomes can be free within the cytoplasm of a cell or attached to endoplasmic reticulum. The function of the ribosome is protein synthesis. There are two varieties in ribosomes and are classified according to sedimentation coefficients- 70S and 80S ribosomes.

Hydrilla plant shows the presence of cellulosic cell wall surrounding its cell membrane. 
Mango tree is an angiosperm plant. It shows the presence of thick cellulosic cell wall.  
Cactus is a xerophytic plant. It shows the presence of thick, cellulosic cell wall. Cell wall prevents the loss of water from plant body. 
Bacteria shows cell wall around its cell membrane. The bacterial cell wall is made up of peptidoglycan. Thus, the correct answer is option A.

• The cell wall is a unique structure present in plant cells. It is found as an outer covering to the plasma membrane. 
• It is absent in animal cells.

• RNA is found everywhere- nucleus, nucleolus, mitochondria, chloroplasts, ribosomes, cytoplasm, etc. RNAs are 3 different types- mRNA, tRNA and rRNA. mRNA and tRNA are found in the cytoplasm and rRNA in the nucleus.
• The ribosomes can be free within the cytoplasm of a cell or attached to the endoplasmic reticulum but do not present inside the nucleus. RNA and ribosomes act together resulting in the synthesis of proteins.

 Hence, the correct answer is option C.

Golgi apparatus is the membranous stacks that involved in the formation of lysosomes, where lysosomes are the suicidal bags of cells with hydrolytic enzymes present in it.
Nucleus, mitochondria and plastids have own DNA and thus, transcription and translation processes are possible for them. Thus, they are able to synthesis their own structural proteins.
Translation is the process of synthesis of proteins in ribosomes.
Mitochondria is the power house of the cell because it serves as the site for ATP synthesis. ATP is synthesized inside mitochondria through the process of Kreb's cycle. Thus, the correct answer is option D.

Functions of endoplasmic reticulum (ER):
1. ER transport materials within the cell. So, called as an intracellular highway.
2. Forms the skeletal framework.
3. Active transport of cellular materials.
4. Metabolic activities due to the presence of different enzymes.
5. Provides increased surface area for cellular reactions. 
6. Formation of nuclear membrane during cell division.

Lysosomes are the small membrane-bounded organelles that contain hydrolytic enzymes. Lysosomes digest the old or dead organelle and foreign particles and thus called as garbage disposal of the cell. Lysosomes are represented morphologically diverse organelle defined by the common function of degrading the intracellular material.

The prokaryotic cell has the primitive nucleus, with the disorganized genetic material. They lack membrane-bounded organelles. Centrosomes are absent in prokaryotes because they divide by asexual method of reproduction like binary fission. They have a cell wall made up of peptidoglycan. They have 70S ribosomes for protein synthesis.
So, the correct answer is option D.