[Pages 57] | Aster Classes

Balbharati, solutions, for, Biology, 11th, Standard, Maharashtra State Board, Chapter 5, Cell Structure and Organization, Exercise, [Pages 57], Answer the following question,

Exercise | Q 2. (A) | Page 57

Answer the following question.

Plants have no circulatory system? Then how cells manage intercellular transport?

SOLUTION

1. Plant cells show the presence of plasmodesmata which are cytoplasmic bridges between neighboring cells.

2. This open channel through the cell wall connects the cytoplasm of adjacent plant cells and allows water, small solutes, and some larger molecules to pass between the cells.

In this way, though plants have no circulatory system, plant cells manage intercellular transport.


Is nucleolus covered by membrane?

SOLUTION

A nucleolus is a specialized structure present in the nucleus which is not covered by the membrane.


Fluid mosaic model proposed by Singer and Nicolson replaced Sandwich model proposed by Danielli and Davson? Why?

SOLUTION

1. The Davson–Danielli model of the plasma membrane of a cell, was proposed in 1935 by Hugh Davson and James Danielli.

2. The model describes a phospholipid bilayer that lies between two layers of globular proteins.

3. This model was also known as a ‘lipo-protein sandwich’, as the lipid layer was sandwiched between two protein layers.

4. But through experimental studies membrane proteins were discovered to be insoluble in water (representing hydrophobic surfaces) and varied in size. Such type of proteins would not be able to form an even and continuous layer around the outer surface of a cell membrane.

5. In case of Fluid-mosaic model, the experimental evidence from research supports every major hypothesis proposed by Singer and Nicolson. This hypothesis stated that membrane lipids are arranged in a bilayer; the lipid bilayer is fluid; proteins are suspended individually in the bilayer; and the arrangement of both membrane lipids and proteins is asymmetric.

Therefore, Fluid mosaic model proposed by Singer and Nicolson replaced Sandwich model proposed by Danielli and Davson.


The RBC surface normally shows glycoprotein molecules. When determining blood group do they play any role?

SOLUTION

1. Glycoproteins are protein molecules modified within the Golgi complex by having a short sugar chain (polysaccharide) attached to them.

2. The polysaccharide part of glycoproteins located on the surfaces of red blood cells acts as the antigen responsible for determining the blood group of an individual.

3. Different polysaccharide part of glycoproteins act as different type of antigens that determine the blood groups.

4. Four types of blood groups A, B, AB, and O are recognized on the basis of presence or absence of these antigens.


How cytoplasm differs from nucleoplasm in chemical composition?

SOLUTION

Smooth endoplasmic reticulum (SER):

1. Depending on cell type, it helps in the synthesis of lipids for e.g. Steroid secreting cells of the cortical region of the adrenal gland, testes and ovaries.

2. Smooth endoplasmic reticulum plays a role in detoxification in the liver and storage of calcium ions (muscle cells).

Rough Endoplasmic Reticulum (RER):

1. Rough ER is primarily involved in protein synthesis. For e.g. Pancreatic cells synthesize the protein insulin in the ER.

2. These proteins are secreted by ribosomes attached to rough ER and are called secretory proteins. These proteins get wrapped in a membrane that buds off from the transitional region of ER. Such membrane-bound proteins depart from ER as transport vesicles.

3. Rough ER is also involved in the formation of membrane for the cell. The ER membrane grows in place by the addition of membrane proteins and phospholipids to its own membrane. Portions of this expanded membrane are transferred to other components of the endomembrane system

1. A thick liquid enclosed by a cell membrane which surrounds the central nucleus in eukaryotes or nucleoid region in prokaryotes is known as cytoplasm.

2. The cytoplasm shows the presence of minerals, sugars, amino acids, t-RNA, nucleotides, vitamins, proteins, and enzymes.

3. The liquid or semiliquid substance within the nucleus is called the nucleoplasm.

4. Nucleoplasm shows the presence of various substances like nucleic acid, protein molecules, minerals, and salts.


Chapter 5: Cell Structure and Organization

EXERCISE [PAGES 57]

Balbharati, solutions, for, Biology, 11th, Standard, Maharashtra, State, Board Chapter 5, Cell Structure and Organization, Exercise, [Pages 57]

Exercise | Q 1. (A) | Page 57

Choose the correct option.

Growth of cell wall during cell elongation take place by ______.

Apposition

Intussusception

Both a & b

Superposition

SOLUTION 

Intussusception.


Cell Membrane is composed of ______.

Proteins and cellulose

Proteins and Phospholipid

Proteins and carbohydrates

Proteins, Phospholipid and some carbohydrates

SOLUTION

Proteins, Phospholipid and some carbohydrates


Plasma membrane is Fluid-structure due to presence of ______

Carbohydrates

Lipid

Glycoprotein

Polysaccharide

SOLUTION

Lipid


Cell Wall is present in———–.

Plant cell

Prokaryotic cell

Algal cell

All of the above

SOLUTION

All of the above


Plasma membrane is ______.

Selectively permeable

Permeable

Impermeable

Semipermeable

SOLUTION

Selectively permeable


Mitochondria DNA is _______________.

Naked

Circular

Double-stranded

All of the above

SOLUTION

All of the above


Lysosomes are not help full in ______.

Osteogenesis

Cellular digestion

Metamorphosis

Lipogenesis

SOLUTION

Lipogenesis


Which of the following set of organelles contain DNA?

Mitochondria, Peroxysome

Plasma membrane, ribosome

Mitochondria, chloroplast

Chloroplast, dictyosome

SOLUTION

Mitochondria, chloroplast


Golgi body is absent in______________.

Prokaryotes

Mature mammalian RBC

Akaryotes

All of the above

SOLUTION

All of the above


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