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The correct choice is (d) emulsifier

For EXPLANATION: There are various techniques that can be used to fuse two different CELLS and all of these are BASICALLY used to either modify the surface of plasma membrane or attach to it (inactivated viruses). EMULSIFIERS however do NEITHER and are hence not used in cell fusion.

Right option is (c) Giant SQUID

For explanation: The first research on ACTION potential and nerve impulses was carried on the axons of giant squid in the late 1940s and early 1950s by ALAN HODGKIN, Andrew Huxley, and Bernard KATZ.

Right answer is (a) Glycophorin A

The best I can explain: Glycophorin A is the FIRST membrane protein to have its amino acid sequence DETERMINED. Other glycophorins are present in lesser AMOUNT in the membranes. Glycophorin A has carbohydrates ATTACHED that account for 60% of its weight.

Right OPTION is (B) Phosphatidyl serine (PS)

Easiest explanation: PS, concentrated in the inner leaflet of cell membrane, has a negative charge at physiologic pH and thus binds positively charged amino acid residues of lysine and arginine. The appearance of PS on the outer surface of aging lymphocytes marks the CELLS for destruction by MACROPHAGES. Appearance of PSon the outer surface of platelets can lead to BLOOD coagulation.

Right ANSWER is (a) Davson and Danielli

To explain I would say: The model of a lipid bilayer lined by a layer of PROTEIN molecules on both sides was the concept put forward by SCIENTISTS Hugh Davson and James Danielli. However, the FLUID mosaic model of CELL membrane was put forward by S. Jonathan Singer and Garth Nicolson. Watson and Crick put forward the structure of DNA double helix.

The correct answer is (b) Sodium

The BEST explanation: DEPOLARIZATION is the flow of sodium ions into the MEMBRANE. These are positively charged and REDUCE the polarity of a cell with respect to EXTERNAL environment and are therefore cause depolarization.

Right option is (a) LIGHT energy

To explain I WOULD say: Halobacterium salinarium is a halophilic archaebacterium, which takes on a purple colour when grown under anaerobic conditions. This is DUE to the presence of bacteriorhodopsin, a proton pump which DEPENDS on light energy. The absorption of light in the RETINAL group of bacteriorhodopsin results in conformational change and a proton from the retinal group moves to the cell exterior.

Correct option is (d) RED blood cells

Easy explanation: Hemolysis is the phenomenon when red blood cells are placed in a dilute HYPOTONIC solution which MAKES the uptake water and RESULTANT swelling. When they swell up, they become leaky and the CONTENTS flow out of the cells.

Right ANSWER is (c) TRANSMEMBRANE proteins

The best explanation: Integral proteins are also known as transmembrane proteins as they pass entirely through the LIPID BILAYER. Transmembrane proteins have domains that protrude both from extracellular side and CYTOPLASMIC side of the cell membrane.

The correct option is (d) All of the mentioned

The explanation is: A hydropathy plot is a method by which transmembrane SEGMENTS of a protein can be identified if the amino acid SEQUENCE of the protein is known. Hydropathy plot assigns each site with a value to measure the hydrophobicity of an amino acid at a site and also at its NEIGHBOURS. This HELPS to determine the arrangement of amino acid in the transmembrane domain, based on its hydrophobic character.

Correct option is (d) bi-concave

The best I can EXPLAIN: The PERIPHERAL proteins of the PLASMA membrane of an erythrocyte are located on the internal surface and make up a fibrillar membrane skeleton, which plays a major role in DETERMINING the bi-concave SHAPE of an erythrocyte.

Correct choice is (b) elastic

The best I can explain: The INTEGRAL membrane proteins are tagged with antibody-coated beads that PROVIDE for HANDLES that can be GRIPPED by laser beam. The experiments concluded that membrane barriers are elastic in NATURE.

The correct choice is (c) Lipid rafts

The explanation is: CHOLESTEROL and sphingolipids tend to self-assemble into microdomains highly ordered than surrounding lipid of cell membrane. Microdomains float within the fluid environment and are known as lipid rafts. Some proteins tend to BECOME CONCENTRATED in the ordered microdomains and others remain outside the boundaries. GPI- anchored PROTEIN SHOW particular fondness towards the microdomains.

Right ANSWER is (a) Alpha-helix

To explain I WOULD say: TRANSMEMBRANE proteins extend on both sides of the membrane and are present mostly as alpha helices and clusters of helices CALLED the Helical bundle. Some proteins are also present as beta barrel. They are made up of beta sheets that ROLLS up into a tube like shape.

Correct ANSWER is (a) Hydroxyl end of cholesterol

The best explanation: Cholesterol MOLECULES are oriented with their SMALL hydrophilic hydroxyl groups TOWARD the membrane surface and the remainder of molecule embedded in LIPID bilayer. The hydrophilic rings of a cholesterol molecule are flat and rigid and interfere with the fatty acid tails of phospholipids.

The correct option is (d) malaria

Easiest explanation: Glycophorin is the receptor utilized by the protozoan that causes malaria, PROVIDING a PATH for entry into the blood cells. Consequently, those who LACK glycophorin A and B are immune against the DISEASE.

Right CHOICE is (a) Membrane proteins

Easy explanation: Fluorescence recovery after photo bleaching (FRAP) is a process by which researchers follow the movement of proteins in cell membranes. A particular membrane protein can be LABELED USING a specific probe, such as a fluorescent antibody. If the labeled proteins are MOBILE, RANDOM movement of these molecules produce a gradual reappearance of fluorescence in an irradiated circle.

The correct option is (b) Diglyceride

To ELABORATE: Membrane glycerides, which CONTAIN a phosphate GROUP has two fatty ACIDS. Therefore, they are phosphor-diglycerides. Only two of the hydroxyl groups of the glycerol are esterified to a hydrophilic phosphate group.

Correct answer is (b) SPT

The explanation is: Single particle tracking or SPT is a method by which individual membrane protein molecules are labeled. Proteins are labeled with antibody-coated gold particles (approximately 40 nm in size). The MOVEMENT of the labeled molecules is FOLLOWED on computer-enhanced VIDEO microscopy.

Right option is (b) False

Easiest explanation: A membrane potential of -70 mV is PRESENT in NEURONS. However this phenomena is not specific to neurons, membrane potential exists in other types of cells as WELL from anywhere between -15 to -100 mV.

The correct answer is (c) DENDRITES

Explanation: The FINE extensions from cell body of the NEURONS are called dendrites which receive information from external sources, USUALLY other neighboring neurons.

Right option is (a) axon

The explanation is: Axon is a single prominent extension that EMERGES from the cell BODY and is RESPONSIBLE for conducting outgoing impulses AWAY from the cell and towards other cells.

The correct ANSWER is (C) plant root hair

Best explanation: Overton placed plant root hair in different solutions containing different solutes.He concluded that more lipid-soluble the solute, more rapidly it would ENTER the root hair cells.

The correct choice is (a) LIGANDS

To explain: Receptors present on the cellular membrane are responsible for RECEIVING the SIGNALS that come from extracellular environment. These signals are received and the corresponding action is GENERATED upon binding of specific MOLECULES called ligands on the receptors. The ligands have complementary structure with the receptors.

Right choice is (a) CELL

Best explanation: The main function of the plasma membrane is compartmentalization, to enclose all the ORGANELLES of the cell and thereby SEPARATE them from external HYDROPHILIC environment.

Correct answer is (d) 3:2

Best explanation: The sodium potassium pump is an active TRANSPORTER that USES ATP to TRANSPORT Na and K ions across a membrane. With each ATP used the pump exports 3 Sodium ions while it imports 2 Potassium ions into the cell.

Correct choice is (a) K^+

The explanation is: K^+ is the ion that is found in most abundance in cells. It also has the GREATEST PERMEABILITY through cell membrane and as a result, it is PUMPED FASTER than any other ion through the cell membrane by active or passive transport.

Right OPTION is (a) True

Explanation: Cell fusion is a technique to FUSE two cells from different species to FORM ONE cytoplasm and one single CONTINUOUS plasma membrane.

Right OPTION is (d) Receptors

The best I can explain: Receptors present on the plasma membrane face OUTWARDS in the extracellular environment and are RESPONSIBLE for RESPONDING to signals received by cell. These signals are received in the form of small molecules that bind to the receptor consequently generating an orchestration of intracellular action.

The correct answer is (d) Changes conformation, TRANSPORTS molecules and facilitated diffusion

Easy explanation: Facilitated diffusion is a method by which molecules are diffused across the cell MEMBRANE with the help of an intermediate protein called facilitative transporter. The DIFFUSING substance binds selectively to this membrane-spanning protein that facilitates in diffusion PROCESS. It undergoes conformational change, exposing the solute to the other surface of the membrane.

The correct answer is (a) PERMEATION pathway

To explain I would say: Transmembrane PROTEINS act as CHANNELS from the intracellular and extracellular transport of ions and molecules. The CHANNEL through which the transport is done is called permeation pathway as it helps in the permeation of solutes and ions through the membrane.

The correct ANSWER is (a) PHOSPHATIDYL choline

For explanation I would say: The phospholipids of cell membrane are composed of phosphatidyl choline (PC), phosphatidyl serine (PS), phosphatidyl ethanolamine (PE) and phosphatidyl inositol (PI). PC is exoplasmic and present towards the extracellular FLUID. PS, PE and Pi are CYTOSOLIC and located towards the cytoplasm.

The CORRECT option is (a) True

The best I can explain: FRAP is a technique that can be used to monitor the MOVEMENTS of MOLECULES across the plasma membranes of a living cell under a light MICROSCOPE.

Right ANSWER is (b) lipids

The explanation: Myelin sheath surrounds the axon which EXTENDS from the soma of a NEURON. Myelin sheath is composed mainly of lipids and their function is to PREVENT loss of impulses.

Correct option is (c) PHOSPHATIDYL ethanolamine (PE)

Easy explanation: PE PROMOTES the curvature of CELL membrane. This is important in the budding and FUSION of cell membranes during maturation.

The correct option is (b) Freeze-fracture REPLICATION

The explanation: The concept that transmembrane proteins PENETRATE through the membrane was obtained from the results of freeze-fracture replication. In this procedure, a FROZEN solid tissue is fractured with a knife blade and metals are deposited on their exposed surfaces to form shadowed REPLICA. This is viewed under ELECTRON microscope and it looks like a path strewn with pebbles, called as membrane-associated particles.

Correct option is (d) Lipid-anchored protein

Explanation: Lipid-anchored PROTEINS are located outside the lipid bilayer on EITHER the extracellular or CYTOPLASMIC SURFACE. They are covalently linked to lipid molecules in the CELL membrane. Peripheral proteins are associated to the cell membrane surface by non-covalent bonds.

Correct ANSWER is (d) 33.33%

EXPLANATION: Animal cell membrane is made up of 50% PROTEIN and 50% Lipids. 60% of all lipids in the membrane are cholesterol molecules. About one THIRD of the cell membrane is made up of cholesterol(1/3rd of 100%= 33.33%).

Correct option is (c) myelin SHEATH

For explanation: Saltatory conduction OCCURS due to the PRESENCE of lipid-rich myelin sheath on the length of the axon. Due to this the action potential jumps from one NODE to the other, resulting in faster action potential TRANSMISSION.

The correct option is (C) 2, 1

The explanation is: The VACUOLE H+-ATPase pump and the vacuole H^+-phosphatase pump are membrane proteins on the vacuole membrane that helps in the active transport of H^+ IONS inside the vacuole. With the HYDROLYSIS of one ATP molecule, two H^+ ions can pass through the H^+-ATPase pump. HOWEVER, with the hydrolysis of one pyrophosphate molecule, one H^+ ion can pass through the H+-pyrophospatase pump.

Right option is (b) PATCHES of cholesterol and sphingolipids in lipid bilayer

Explanation: When MEMBRANE LIPIDS are extracted from cell and used to produce artificial lipid bilayers, cholesterol and sphingolipids tend to self-assemble into microdomains HIGHLY ordered than surrounding lipid. Microdomains float within the fluid environment and are known as lipid rafts.

Correct answer is (d) K^+

The best I can explain: K^+ has the HIGHEST permeability in RESTING nerve cells. Most of the ion channels open in the membrane of a resting nerve cell are selective for potassium, REFERRED to as potassium leak channels.

Right option is (b) 1972

To elaborate: The FLUID mosaic model proposed in 1972 by S. Jonathan SINGER and Garth Nicolson of the University of California, San Diego. This model has served as the CENTRAL DOGMA of membrane BIOLOGY for over three decades.

Right option is (b) Mechano-gated channels

Explanation: The conformational CHANGE of mechano- gated channels DEPEND on mechanical forces that are applied to the membrane. These mechanical forces such as STRETCH tension forces the CHANNEL to open the pathway for the transport of ions and SOLUTES.

Correct OPTION is (c) Oligosaccharides

To elaborate: The modification of membrane proteins by addition of CARBOHYDRATES occurs by a PROCESS called glycosylation. The carbohydrate of glycoproteins is present as short, branched hydrophilic oligosaccharides. In contrast to long-chained polysaccharides, they only have upto 15 sugars PER CHAIN.