Question 1

The plasma membrane consists mainly of:

Accepted Answer

Correct answer is C

Question 2

For cell membrane, name "plasmalemma" was given by?

Accepted Answer

Correct answer is D

Question 3

Most abundant Lipid in cell membrane is:

Accepted Answer

Correct answer is A

Question 4

If beet root is kept in cold water, anthocyanin does not come out due to plasma membrane.

Accepted Answer

Anthocyanin pigment cannot come outside due to impermeability of plasma membrane.

Question 5

Which of the following layer is present nearest to plasma membrane in plant cell?

Accepted Answer

Secondary wall situated near the plasma membrane. After the formation of primary wall.

Question 6

Keeping in view the fluid mosaic model for the structure of cell membrane, which one of the following statements is . correct with respect to the movement of lipids and proteins from one lipid mono layer to the other (described as flip flop movement)?

Accepted Answer

Correct answer is D

Question 7

Lipid molecule in plasma membrane are arranged in:

Accepted Answer

According to fluid mosaic model, the arrangement of lipid molecules in plasma membrane is head parallel. It means head of both lipid layer towards the outside.

Question 8

Who proposed "fluid mosaic model" for plasma membrane?

Accepted Answer

Correct answer is D

Question 9

Ion carriers are located in:

Accepted Answer

Surface of plasma membrane has the ion carriers which participates in exchange of ions.

Question 10

How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?

Accepted Answer

Neutral solutes move across the membrane by the process of simple diffusion along the concentration gradient i.e., from higher concentration to the lower concentration. Polar molecules cannot pass through the nonpolar lipid bilayer, they require carrier proteip of the membrane to facilitate their transport across the membrane. In facilitated diffusion, molecules are transported along concentration gradient by help of ion channels and permeases and it does not involve energy expenditure (passive transport).

Question 11

Select the correct statement from the following regarding cell membrane.

Accepted Answer

According to the fluid mosaic model of cell membrane structure proposed by Singer and Nicolson (1972). Plasma membrane contains about 50–60%proteins and 50–40% lipids. Lipids form a bilayer with hydrophilic heads pointing outwards. Cell membrane allows transport of some molecules by passive transport, e.g., water, neutral solutes while some are transported actively, e.g., Na+/K+ pump.

Question 12

Keeping in view the ‘fluid mosaic model’ for the structure of cell membrane, which one of the following statement is correct with respect to the movements of lipids and proteins from one lipid monolayer to the other (described as flip-flop movement)?

Accepted Answer

According to fluid mosaic model, there is rapid internal motion involving flexing, within each lipid molecule a rapid lateral diffusion of the lipids is possible and a slow ‘flip-flop’ motion, i.e., a transfer of lipid molecules from one side of the bilayer to the other, is also possible. The lipid molecules might also rotate about their axes. The proteins of the membrane are concerned with the enzymatic activity of the membrane, with transport of molecules, and with a receptor function whereas, the lipid bilayer provides the permeability barrier.

Question 13

In fluid mosaic model of plasma membrane :

Accepted Answer

In fluid mosaic model of plasma membrane, phospholipids form a bimolecular layer in the middle part.

Question 14

Plasma membrane is made up of :

Accepted Answer

Every living cell is externally covered by a thin transparent, electron microscopic, elastic semipermeable membrane called cell membrane. It is composed of lipids (mostly phospholipid), proteins (peripheral and integral) and carbohydrates (glycoprotein and glycolipids).

Question 15

The lipid molecules present in plasma membrane have polar heads and non-polar tails (as shown in figure). Which option represents the correct arrangement of lipids in lipid bilayer?

Accepted Answer

Lipids are arranged in bilayers and proteins are embedded in it. Lipids are arranged within the membrane with polar head towards the outer side while hydrophobic tails towards the inner side.

Question 16

A biomembrane consists of lipids, proteins carbohydrates and water. These lipid molecules are :

Accepted Answer

A biomembrane consist of lipids (20-79%) proteins (20-70%), carbohydrates (1-5%) and water (20%) The lipid molecules are amphiatic or amphipathic, that is, they possess both polar hydrophilic (water loving) and non-polar hydrophobic (water repelling) ends.

Question 17

Mesosomes are the infoldings of cells membrane, whichI. helps in cell wall formation, DNA replication and respirationII. increases the surface area of plasma membraneIII. are present in both prokaryotic and eukaryotic cellsChoose the correct option :

Accepted Answer

A special membranous structure is the mesosome which is formed by the extensions of plasma membrane into the cell. There extensions are in the form of vesicles, tubules and lamellae They help in cell wall formation, DNA replication and distribution to daughter cell. They also help in respiration and secretion processes to increase the surface area of the plasma membrane and enzymatic content.

Question 18

Cell membrane was discovered by Schwann (1838) but it was named by :

Accepted Answer

Cell membrane was discovered by Schwann (1838) but it was named by Nageli and Cramer (1855).

Question 19

According to widely accepted ‘fluid mosaic model’ cell membranes are semi-fluid, where lipids and integral proteins can diffuse randomly. In recent years, this model has been modified in several respects. In this regard, which of the following statement is incorrect?

Accepted Answer

According to fluid mosaic model, proteins cannot undergo flip-flop movements in the lipid bilayer.

Question 20

The transport of metabolities across the biomembrane occurs through :

Accepted Answer

Transport of metabolites across the biomembrane occurs through(i) Passive Transport : Transport of molecules across plasma membrane along the concentration gradient This could occur through simple diffusion or through facilitated diffusion (with the aid of some carriers of channels) (ii) Active Transport : Movement of molecules against the concentration gradient with the help of energy (ATP) (iii) In case of bacteria, plasma membrane forms the extensions to form special membranous structures called mesosomes. It plays an important role in respiration. In some prokaryotes, like cyanobacteria, membrane extension froms chromatophores, which contains pigments.

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Solution for Class 11, Biology, Cell: The Unit of Life

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