8

Q1. Name the two cells which lack a nucleus.

Solution

The cells which lack a nucleus are as follows:

Mammalian erythrocytes

Sieve tube cells of vascular plants

Q2. Which element remain united at the critical ion level of two subunits of ribosome?

Solution

Magenesium is the constituent of chlorophyll, middle lamella and are connected with phosphate transfer in respiration, binding of ribosomes and DNA and RNA synthesis.

Q3. Give the significance of the following:    

Quasi fluid nature of lipid  

The fluid nature of the membrane  

Solution

Quasi fluid nature of lipid: It enables the lateral movement of proteins within the lipid bilayer.  

The fluid nature of the membrane: It enables functions such as cell growth, secretion, endocytosis, cell division and formation of intercellular junction.  

Q4. Name the plastids which store proteins.

Solution

Aleuroplasts

Q5. Draw a well-labelled diagram of the chloroplast.

Solution

Chloroplast:  

Q6. What was the drawback of the cell theory proposed by Schleiden and Schwann?

Solution

The cell theory which was explained by Schleiden and Schwann could not explain how new cells were formed.

Q7. Explain the structure of a centrosome.

Solution

The centrosome consists of two centrioles which lie perpendicular to each other. Each centriole has a cart-wheel-like organisation. Each centriole is made of nine peripheral tubulin fibrils which are evenly spaced. Each of the peripheral fibrils is a triplet. The adjacent triplets are linked. The central part of the proximal region of each centriole is called a hub. The hub is connected to peripheral triplets by proteinaceous spokes.

Q8. Write the compositions of the cell walls of the following:

Cell wall of algae

Plant cell wall

Solution

Cell wall of algae: Cellulose, mannans, galactans, calcium carbonate

Plant cell wall: Cellulose, hemicelluloses, lignin, pectin, proteins etc.

Q9. Name any two carotenoid pigments.

Solution

The carotenoid pigments are xanthophyll and carotene.

Q10. Name the scientist who first described a live cell.

Solution

Anton Von Leeuwenhoek first described a live cell.

Q11. Draw a diagram of a mitochondrion and label any four parts.  

Solution

Mitochondrion:        

Q12. What are mesosomes?

Solution

Mesosomes are essential infoldings of the cell membrane, a unique characteristic of prokaryotic cells.

Q13. Name any one cell organelle which is not bound by the membrane.

Solution

Ribosome

Q14. How are food vacuoles formed in protists?

Solution

In protists, food vacuoles are formed by engulfing food.

Q15. What are the three layers bound by the cell envelope in prokaryotic cells?

Solution

The three layers bound by the cell envelope in prokaryotic cells are the outer glycocalyx, the middle cell wall and the inner plasma membrane.

Q16. Write the name of the structure which connects the cytoplasm of two cells. OR Name the structure which traverses the cytoplasm and the middle lamella to connect two neighbouring cells through their cytoplasm.

Solution

Plasmodesmata connect the cytoplasm of two cells.

Q17. Name the following:

Plastids which store oil

Plastids which store proteins

Plastids which store starch

Solution

Plastids which store oil - Elaioplasts

Plastids which store proteins - Aleuroplasts

Plastids which store starch - Amyloplasts

Q18. Write the functions of the cytoskeleton.  

Solution

Functions of cytoskeleton:    

It provides mechanical support and motility to the cell.  

It maintains the shape of the cell.  

Q19. What is the main arena of the cell and state its function.  

Solution

The cytoplasm is the main arena of the cell, and it is the site for many metabolic activities which occur within the cell.  

Q20. State the functions of the cell wall in a prokaryotic cell.

Solution

Functions of the cell wall in a prokaryotic cell are as follows:

It determines the shape of the cell.

It provides strong structural support to prevent the cell from bursting or collapsing.

Q21. Describe the interphase nucleus.

Solution

The nucleus of the interphase shows the nuclear matrix, presence of one or more nuclei and loose indistinct network of chromatin.

Q22. Describe the two types of membrane proteins.

Solution

Two types of membrane proteins are as follows:

Integral membrane proteins: They are partially or totally buried in the membrane.

Peripheral membrane proteins: They are present on the surface of the membrane.

Q23. Define plasmids.

Solution

Plasmids are small circular DNA found outside the genomic DNA in bacteria.

Q24. Name the largest cell.

Solution

Egg of an ostrich.

Q25. What is the length of mycoplasma which is the smallest cell?

Solution

0.3 micron in length.

Q26. Who observed for the first time that the plants are composed of different kinds of cells which form the plant tissues?

Solution

Matthias Schleiden observed for the first time that the plants are composed of different kinds of cells which form the plant tissues.

Q27. State the compartments of the intracellular space formed due the endoplasmic reticulum.

Solution

The two compartments of the intracellular space formed due the endoplasmic reticulum are

Luminal compartment

Extraluminal compartment

Q28. State the three parts of the bacterial flagellum.

Solution

The three parts of the bacterium flagellum are filament, hook and basal body.

Q29. What study helped scientists to deduce the possible structure of the cell membrane?

Solution

The study of human red blood cells helped scientists to deduce the structure of the cell membrane.

Q30. Who proposed the fluid mosaic model of the cell membrane?

Solution

Singer and Nicolson proposed the fluid mosaic model of the cell membrane.

Q31. Write the names of any four prokaryotic cells.

Solution

Blue-green algae Mycoplasma PPLO (Pleuro-Pneumonia-Like Organisms) Bacteria

Q32. Name the process by which mitochondria divide.

Solution

Mitochondria divide by fission.

Q33. Why are the endoplasmic reticulum, Golgi complex, lysosomes and vacuoles collectively called the endomembrane system?

Solution

The functions of the endoplasmic reticulum, Golgi complex, lysosomes and vacuoles are coordinated. Hence, they are collectively called the endomembrane system.

Q34. State the site of enzymes in chloroplasts.

Solution

Stroma of the chloroplast.

Q35. Define tonoplast.

Solution

The tonoplast is the thin membrane which covers the vacuole.

Q36. Name the smallest cell found.

Solution

Mycoplasma

Q37. State the function of the primary cell wall found in young plants.

Solution

The function of the primary cell wall found in young plants is growth.

Q38. Define capsule.

Solution

When the glycocalyx is in the form of a thick and tough layer around the prokaryotic cell it is called a capsule.

Q39. State the functions of the cell wall.

Solution

Functions of the cell wall:

Provides shape to the cell.

Protects the cell from mechanical damages and infections.

Helps to enable cell-to-cell interaction.

Q40. When is the glycocalyx called a slime layer?  

Solution

The glycocalyx is called a slime layer when it is in the form of a loose sheath.  

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