Category: Cell Biology Objective Questions

Cell Biology Multiple Choice Questions on “Chemical Composition of Membranes”.

1. The lipids present in cell membrane are _____________
A. Polar
B. Non- polar
C. Charged
D. Ampipathic
Answer: D
Clarification: The lipids that form the main constituent of cellular membrane has both hydrophobic and hydrophilic regions. They are made up of polar hydrophilic heads as well as non-polar hydrophobic tails made up of carbon chains.

2. The model of a lipid bilayer lined by a layer of protein molecules on both sides was put forward by _____
A. Davson and Danielli
B. Singer and Nicolson
C. Watson and Crick
D. None of the mentioned
Answer: A
Clarification: 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.

3. The phosphoglycerides in cell membrane are of the _________ type.
A. Triglyceride
B. Diglyceride
C. Monoglyceride
D. Polyglyceride
Answer: B
Clarification: 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.

4. Shingolipids is the derivative of ______________
A. Sphingosine
B. Shingomycin
C. Sphingoceramicin
D. Sphingolipid polymer
Answer: A
Clarification: Shingolipids are the derivative of sphingosine, an amino alcohol that contains a long hydrocarbon chain. Sphingosine is a ceramide linked to fatty acid by its amino group.

5. Which of the following is not a component of cell membranes?
A. Phosphodiglycerides
B. Sphingolipids
C. Cholesterol
D. Phosphotriglycerides
Answer: D
Clarification: Phospholipids present in cell membrane are diglycerides and not triglycerides. Triglycerides have three fatty acids and are not ampipathic in nature. It also consists of sphingolipid and cholesterol.

6. In animals, the amount of cholesterol present in cell membrane is ___________
A. 20%
B. 15%
C. 50%
D. 33.33%
Answer: C
Clarification: In animal cell, cholesterol constitutes up to 50% of the lipid molecules present in plasma membrane. In plants however, it is not yet discovered whether they lack cholesterols or not. Plant cells however have cholesterol-like sterol.

7. Which part of cholesterol molecule is not embedded in the lipid bilayer?
A. Hydroxyl end of cholesterol
B. Entire molecule of cholesterol
C. Hydrophobic rings
D. Hydroxyl end and ¹⁄₄th of the hydrophobic rings
Answer: A
Clarification: 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.

8. Which of the following is exoplasmic?
A. Phosphatidyl choline
B. Phosphatidyl serine
C. Phosphatidyl ethanolamine
D. Phosphatidyl inositol
Answer: A
Clarification: 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.

9. Which of the following facilitates binding of positively charged amino acid residues?
A. Phosphatidyl choline (PC.
B. Phosphatidyl serine (PS)
C. Phosphatidyl ethanolamine (PE)
D. Phosphatidyl inositol(PI)
Answer: B
Clarification: 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 PS on the outer surface of platelets can lead to blood coagulation.

10. Which of the following promote curvature of cell membrane?
A. Phosphatidyl choline (PC.
B. Phosphatidyl serine (PS)
C. Phosphatidyl ethanolamine (PE)
D. Phosphatidyl inositol(PI)
Answer: C
Clarification: PE promotes the curvature of cell membrane. This is important in the budding and fusion of cell membranes during maturation.

11. Carbohydrates present in cell membrane are generally ___________
A. Monosaccharides
B. Disachharides
C. Oligosaccharides
D. Polysaccharides
Answer: C
Clarification: 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.

12. Lipid rafts are ___________
A. Patches of glycoproteins in the lipid bilayer
B. Patches of cholesterol and sphingolipids in lipid bilayer
C. Patches of only cholesterol in lipid bilayers
D. Detached patches of proteins floating on the lipid bilayer
Answer: B
Clarification: 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.

Cell Biology Multiple Choice Questions on “Chloroplast Function – CO2 Fixation and Carbohydrate Synthesis in C3 Plants”.

1. Who discovered C3 cycle?
A. Melvin Calvin
B. Kolliker
C. Robert Brown
D. Rudolph Markus
Answer: A
Clarification: Melvin Calvin discovered the C3 cycle, otherwise known as Calvin cycle in photosynthesis pathway of Chlorella. He used radioisotope carbon – 14 to mark the path of the metabolism in the C3 plants.

2. Identify the following compound.

A. Ru5P
B. RuBP
C. R5P
D. Rpi
Answer: B
Clarification: RuBP is ribulose 1, 5-bisphosphate, a 5 carbon compound. RuBP is involved in the carbon fixation. RuBP is regenerated from Ru5P by phosphorylation and it renters the cycle through HMP shunt.

3. Which of the following is an example of C3 plants?
A. Sugarcane
B. Cactus
C. Wheat
D. Orchids
Answer: C
Clarification: The plants that undergo C3 cycle to fix CO₂ in the atmosphere by photosynthesis is called C3 plants. These plants are spread to around 85% in the plant kingdom.

4. C3 plants grown in cold climates.
A. True
B. False
Answer: A
Clarification: The C3 plants are most commonly found in temperate and cold regions. They can do photosynthesis efficiently in cold climates, where there is less loss of water.

5. Calvin cycle occurs in the cytoplasm of the cell.
A. True
B. False
Answer: B
Clarification: Calvin cycle takes place in the stroma of the chloroplast of the cell. The stroma contains the necessary energy compounds for the preparation of carbohydrate.

6. What is the final product of the Calvin cycle?
A. Sedoheptulose
B. Erythrose
C. Glucose
D. Ribose
Answer: C
Clarification: The Calvin cycle produces three carbon sugar molecules by taking 3 molecules of CO₂ from the atmosphere. These three carbon sugars are later converted to six-carbon sugar called glucose.

7. How many ATP molecules are required to produce one molecule of glucose?
A. 18
B. 15
C. 12
D. 9
Answer: A
Clarification: Calvin cycle uses 18 molecules of ATP and 12 molecules of NADPH to synthesize one molecule of glucose. These ATP and NADPH are produced from the light reactions of photosynthesis.

8. Which of the following enzyme is used to fix CO₂ through Calvin cycle?
A. Ribose -1, 5- bisphosphate carboxylase
B. Ribulose -1, 6- bisphosphate carboxylase
C. Ribose -1, 6- bisphosphate carboxylase
D. Ribulose -1, 5- bisphosphate carboxylase
Answer: D
Clarification: Ribulose -1, 5- bisphosphate carboxylase is an enzyme commonly known as RuBisCO. It aids in the fixation of CO₂ by absorbing the carbon from it and converting it to carbohydrate.

9. Which redox-regulated protein controls the functioning of Calvin cycle?
A. CP4
B. CP8
C. CP12
D. CP16
Answer: C
Clarification: The redox regulated protein CP12 controls the carbon fixation on Calvin cycle. It consists of 80 amino acids and it is found in most of the photosynthetic organisms.

10. How many times should the Calvin cycle happen, in order to obtain one glucose molecule?
A. 2
B. 4
C. 3
D. 6
Answer: D
Clarification: The Calvin cycle needs to be repeated six times to produce one glucose molecules. Glucose being a six carbon atoms gets its carbon atoms from G3P complex. The first five G3P molecules are regenerated and only the sixth G3P molecule completes the glucose.

Cell Biology Questions & Answers for Examson “Cytoplasmic Membrane Systems – Plant Cell Vacuoles”.

1. 90% of the volume of a plant cell is occupied by the vacuole.
A. True
B. False
Answer: A
Clarification: Many cells of a plant are occupied by 90% of the vacuole. Most of the cell’s sugars, proteins and other biomolecules are stored temporarily in the vacuole.

2. In plant cells, by-products of the metabolic pathways are stored in _____________
A. vacuole
B. mitochondrion
C. chloroplast
D. nucleus
Answer: A
Clarification: Vacuoles store many toxic compounds of the cell including by-products of metabolic pathways. Unlike animal cells, plant cells isolate the toxic by-products (by storing them in the vacuole) from the rest of the cell rather than discharging them.

3. Which of the following is a toxic by-product stored in the plant cell vacuole that is clinical importance?
A. oxytocin
B. sialic acid
C. digitalis
D. tonoplast
Answer: C
Clarification: Digitalis is a toxic by-product stored in the plant cell vacuole, used to treat congestive heart failure and heart rhythm problems.

4. Tonoplast is a ___________
A. membrane
B. toxic compound
C. sphingolipid
D. glycoprotein
Answer: A
Clarification: Tonoplast is the membrane that bounds the vacuole. It contains many active transport system that pumps ions into the vacuole.

5. Water enters the vacuole by ____________
A. reverse osmosis
B. osmosis
C. active diffusion
D. passive diffusion
Answer: B
Clarification: Due to high concentration of ions in the vacuole, water enters by osmosis. Hydrostatic pressure exerted by the vacuole provides mechanical strength to the plant cell.

6. Plant vacuoles are also sites of intracellular digestion.
A. True
B. False
Answer: A
Clarification: Similar to lysosomes present in the animal cells, plant cells contain vacuoles for intracellular digestion. Plant vacuoles have many of the same acid hydrolases as present in the lysosomes.

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Cell Biology Multiple Choice Questions on “Chemical Basis of Life – Nucleic Acids”.

1. Which monomers compose the strands of nucleic acids?
A. Amino acids
B. Ribose
C. Functional groups
D. Nucleotides
Answer: D
Clarification: The strands of nucleic acids are composed of monomeric units called nucleotides. Nucleic acids are mainly the storage sites for genetic information and also have structural and catalytic functions.

2. What are the types of nucleic acids are found in living organisms?
A. deoxyribonucleic acid & nucleotide acid
B. deoxyribonucleic acid & ribonucleic acid
C. ribonucleic acid & nucleotide acid
D. ribonucleic acid & nucleoside acid
Answer: B
Clarification: Two types of amino acids are found in living organisms namely DNA (deoxyribonucleic aciD. and RNA (ribonucleic aciD.. DNA is the carrier of genetic information in animals and RNA plays this role in viruses.

3. How many types of nucleotides are present?
A. 1
B. 2
C. 3
D. 4
Answer: D
Clarification: There are four types of nucleotides present in a DNA (or RNA. strand. DNA consists of adenine, guanine, cytosine and thiamine; RNA on the other hand consists of uracil instead of thiamine and other three nucleotides are similar.

4. Purines and pyrimidines are different molecules.
A. True
B. False
Answer: A
Clarification: Purines and pyrimidines are the two types of nitrogenous bases found in nucleic acids. Pyrimidines are small molecules consisting of one ring and purines are larger containing two rings in their molecules.

5. Ribozymes are _____________
A. cell organelle
B. enzymes
C. nucleotide
D. nucleoside
Answer: B
Clarification: Ribozymes are RNA enzymes that perform a catalytic activity. Ribosomal RNAs don’t function as genetic carriers but serve a structural function. One subunit of ribosomal RNA acts as a catalyst in addition reaction of amino acids in the protein synthesis; these are called ribozymes.

6. ATP and GTP are __________
A. cells
B. receptors
C. nucleotides
D. nucleic acids
Answer: C
Clarification: Adenosine triphosphate (ATP) and guanosine triphosphate (GTP) are nucleotides of utmost importance in organisms. The energy present in living organisms is stored in the form of ATP and GTP binds to a variety of proteins called G proteins to turn on their activities.

Cell Biology Multiple Choice Questions on “Cellular Membranes – Structure and Function of Membrane Proteins”.

1. Which of the following is covalently attached to a lipid molecule in cell membrane?
A. Integral protein
B. Transmembrane protein
C. Peripheral protein
D. Lipid-anchored protein
Answer: D
Clarification: 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.

2. Integral proteins are also known as ____________
A. Intrinsic proteins
B. Glycosylated proteins
C. Transmembrane proteins
D. Bilayer proteins
Answer: C
Clarification: 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.

3. The concept of transmembrane proteins was obtained from the results of which technique?
A. Freeze-fraction replication
B. Freeze-fracture replication
C. Fraction replication
D. None of the mentioned
Answer: B
Clarification: 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.

4. Transmembrane domain of a transmembrane protein is present as _______________
A. Alpha-helix
B. Beta-sheet
C. Triple beta-sheet
D. None of the mentioned
Answer: A
Clarification: The transmembrane domain of a cell membrane protein is the part that spans through the lipid bilayer of cell membrane. It mainly consists of a chain of about 20 non-polar amino acids arranged in an alpha- sheet structure.

5. Hydropathy plot helps to _______________
A. Identify hydrophobic amino acids
B. Determine arrangement of amino acids in a transmembrane protein
C. Provides an average hydrophobicity of short peptide segments
D. All of the mentioned
Answer: D
Clarification: 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.

6. The channel in a membrane protein by which an ion or molecule can be transported in and out of the cell membrane is known as ___________
A. Permeation pathway
B. Permeate channel
C. Permeation channel
D. Channel pathway
Answer: A
Clarification: 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.

7. Greater degree of unsaturation in fatty acids of cell membrane _________
A. Lowers the transition temperature
B. Raises the transition temperature
C. Has no effect on transition temperature
D. Doubles the transition temperature
Answer: A
Clarification: The lipid is converted from a liquid crystalline phase to a frozen crystalline phase. The temperature at which this change occurs is called transition temperature. The greater degree of unsaturation in fatty acids lower the transition temperature and it quickly achieves the crystalline frozen state due to high unsaturation.

8. GPI- anchored proteins show particular affinity towards ________
A. Cholesterol
B. Hydrophobic tail
C. Lipid rafts
D. Phosphatidylserine
Answer: C
Clarification: 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.

9. FRAP is a technique to detect ___________
A. Membrane proteins
B. Transporting ions
C. Cholesterol patches
D. Cannot be determined
Answer: A
Clarification: 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.

10. Antibody -coated gold particles are used in _______________
A. FRAP
B. SPT
C. X-ray crystallography
D. Cannot be determined
Answer: B
Clarification: 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.

Cell Biology Questions and Answers for Experienced peopleon “Chloroplast Function – CO2 Fixation and Carbohydrate Synthesis in C4 Plants”.

1. Who discovered C4 cycle?
A. Hatch and Slack
B. Kolliker
C. Robert Brown
D. Rudolph Markus
Answer: A
Clarification: Hatch and Slack discovered the C4 pathway in the year 1966. It is also called a Hatch – Slack pathway. The pathway produces four carbon sugar molecules.

2. What is the enzyme used in the conversion of pyruvate to phosphoenolpyruvate?
A. Pyruvate monophosphate dikinase
B. Pyruvate orthophosphate dikinase
C. Pyruvate monophosphate reductase
D. Pyruvate orthophosphate reductase
Answer: B
Clarification: This reaction is the first step in the Hatch – Slack pathway. The enzyme pyruvate orthophosphate dikinase is used to convert pyruvate to phosphoenolpyruvate along with ATP.

3. Which of the following leaf anatomy is a characterization of C4 plants?
A. Piezo anatomy
B. Norman anatomy
C. Kranz anatomy
D. Richard anatomy
Answer: C
Clarification: Kranz has the meaning “wreath” in German anatomy. There are two rings surrounding the vascular bundle. The inner ring is made of bundle sheath while the outer ring is made up of mesophyll cells.

4. Which of the following is an example of C4 plants?
A. Sugarcane
B. Wheat
C. Rice
D. Cactus
Answer: A
Clarification: The plants that produce four carbon sugar molecules by taking atmospheric CO₂ is known as C4 plants. These plants undergo Hatch – Slack pathway.

5. What is the final product of the C4 cycle?
A. Aspartate
B. Malate
C. Oxalate
D. Acetate
Answer: B
Clarification: Malate is formed as a final product of the C4 pathway. Malate in the final step regenerates the pyruvate and fixes CO₂.

6. Where does the C4 pathway take place?
A. Bundle sheath
B. Xylem
C. Mesophylls
D. Phloem
Answer: C
Clarification: The C4 pathway takes place in the mesophyll cells of the plant system. They are dark reaction and does not require light to take place. The Calvin cycle on the other hand takes place on the bundle sheath.

7. The C4 plants grow in the cold climate places.
A. True
B. False
Answer: A
Clarification: The C4 plants are better suited to grow in the hot climate regions and are less suitable to grow in the cooler regions. They are only 3% of the total vascular plants.

8. The total carbon dioxide fixation done by the C4 plants is _________
A. 3%
B. 13%
C. 23%
D. 33%
Answer: C
Clarification: They are more efficient than C3 plants in the carbon dioxide fixation in the atmosphere. They usually grow in higher temperature regions where the activity of the enzyme RuBisCO is high.

9. Which enzyme plays the role of a catalyst in CO₂ fixation in C4 plants?
A. Carbonic mutase
B. Carbonic reductase
C. Carbonic anhydrase
D. Carbonic dehydrogenase
Answer: C
Clarification: Carbonic anhydrase is an enzyme, which plays the role of catalyst in the first CO₂ fixation step of C4 pathway. It helps the CO₂ molecule to bind to the active site of RuBisCO.

10. What is the chemical formula for oxaloacetic acid?
A. C₄H₃O₅
B. C₄H₄O₅
C. C₄H₄O₆
D. C₃H₄O₅
Answer: B
Clarification: The oxaloacetic acid is formed when phosphoenolpyruvate reacts with CO₂. This is the first product of the pathway which is a four carbon compound.

11. C4 pathway uses 5 ATP molecules and 4 NADPH molecules as the energy source.
A. True
B. False
Answer: B
Clarification: The C4 pathway uses 5 ATP and 2 NADPH molecules as its energy source. This is higher than the energy requirement in Calvin cycle but C4 can be effective under hot and less water content.

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