Category: Cell Biology Objective Questions

Cell Biology Multiple Choice Questions on “Chloroplast Structure and Function – Light Absorption”.

1. Energy absorbed from sunlight is stored as chemical energy in which of the following biomolecules?
A. ATP, ADP
B. ATP, NADPH
C. NAD, FAD
D. NADH₂, ATP
Answer: B
Clarification: Energy from sunlight is absorbed and saved in the form of chemical energy in two types of biomolecules in plants namely ATP and NADPH. ATP is the cell’s primary source of energy and NADPH is the cell’s primary source of reducing power.

2. Which types of molecules are synthesized in light-independent (dark) reactions?
A. proteins
B. glycolipids
C. carbohydrates
D. nucleic acids
Answer: C
Clarification: The second stage of events involved in photosynthesis is referred to as light-independent (dark) reactions. In these carbohydrates are synthesized from carbon dioxide using energy stored in ATP and NADPH.

3. Photon of light of higher wavelength has _____________ energy.
A. higher
B. lower
C. intermittent
D. dissipated
Answer: A
Clarification: Energy and wavelength are inversely related, therefore photon of higher energy will have lower wavelength and photon of lower energy will have higher wavelength.

4. Pigments absorb light of particular wavelengths.
A. True
B. False
Answer: A
Clarification: Pigments are compounds that appear visibly colored because they only absorb light of particular wavelengths. Chlorophyll is a green colored pigment found in chloroplasts of plants.

5. Which part of the chlorophyll is responsible for absorption of light?
A. hydrophobic phytol chain
B. porphyrin ring
C. thylakoid membrane
D. outer membrane
Answer: B
Clarification: Chlorophyll has two parts; porphyrin ring and hydrophobic phytol chain. Porphyrin ring functions in the absorption of light and the hydrophobic phytol chain maintains the integration of chlorophyll in photosynthetic chain.

6. Which atoms are present in the porphyrin of a chlorophyll molecule?
A. iron
B. magnesium
C. calcium
D. sulphur
Answer: B
Clarification: In myoglobin and hemoglobin the porphyrins contain iron (heme groups) whereas porphyrins present in chlorophyll contain magnesium atom.

7. What are carotenoids?
A. pigments
B. cell organelles
C. terrestrial plants
D. granulated thylakoids
Answer: A
Clarification: Carotenoids are accessory light-absorbing pigments found in terrestrial plants. β-carotene is a carotenoid. These pigments absorb in blue and green regions of the spectrum.

8. Carotenoids dissipate absorbed energy as heat.
A. True
B. False
Answer: A
Clarification: Carotenoids function as secondary light absorbers during photosynthesis and draw excess away from excited chlorophyll molecules (to prevent the formation of singlet oxygen) to dissipate it as heat.

9. Which of the following type of spectrum is a plot of efficiency of different types of wavelengths in bringing about the photosynthesis?
A. absorption spectrum
B. action spectrum
C. efficiency spectrum
D. reflection spectrum
Answer: B
Clarification: Action spectrum is a plot of relative rate of photosynthesis induced by lights of different wavelengths. The spectrum identifies wavelengths that are effective in inducing a physiological response.

10. Which of the following contains a linear system of conjugated double bonds?
A. β-carotene
B. chlorophyll
C. chloroplast
D. thylakoid
Answer: A
Clarification: β-carotene is a carotenoid, a pigment that acts as accessory light absorber during photosynthetic reaction. It has a linear system of conjugated double bonds.

Cell Biology Multiple Choice Questions on “Cytoplasmic Membrane Systems – Endoplasmic Reticulum”.

1. The membranes of rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER) are continuous.
A. True
B. False
Answer: A
Clarification: There are two types of endoplasmic reticulum, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). It has been found that fluorescently labeled proteins and lipids can diffuse from one type of ER to another suggesting that their membranes are continuous.

2. Which of the following biomolecules are not synthesized by the endoplasmic reticulum?
A. Proteins
B. Lipids
C. Nucleic acids
D. Cholesterol
Answer: C
Clarification: The primary function of endoplasmic reticulum is the synthesis of proteins. However certain lipids and cholesterol molecules are also synthesized in ER.

3. All the cells contain the same ratio of rough and smooth endoplasmic reticulum.
A. True
B. False
Answer: B
Clarification: Ribosomes are associated with the cytosolic space of rough endoplasmic reticulum hence they are more actively involved in protein synthesis. In cells that secrete large amount of proteins e.g. the cells of kidneys and salivary glands, more number of RER are present. Hence the ratios of SER and RER vary depending on the cell type.

4. Detoxification of organic compounds like barbiturates and ethanol in the liver is carried out by ________________
A. smooth endoplasmic reticulum
B. sarcoplasmic reticulum
C. rough endoplasmic reticulum
D. nucleus
Answer: A
Clarification: Detoxification of organic compounds is carried out by the smooth endoplasmic reticulum, chronic use of compounds such as barbiturates and ethanol can lead to proliferation of SER in liver cells.

5. Which enzymes are responsible for detoxification of organic compounds carried out by the smooth endoplasmic reticulum?
A. Dehydrogenases
B. Oxygenases
C. Nucleases
D. Ribonucleases
Answer: B
Clarification: Oxygen transferring enzymes – oxygenases (including cytochrome P450) carry out the detoxification of organic compounds and are synthesized in the smooth endoplasmic reticulum.

6. Sarcoplasmic reticulum is found in ________________
A. liver cells
B. kidney cells
C. muscle cells
D. neurons
Answer: C
Clarification: Smooth endoplasmic reticulum sequesters calcium ions within the cytoplasm of the cell and controlled release of Ca²⁺ from the SER of cardiac and skeletal muscle cells triggers contraction. Smooth endoplasmic reticulum (SER) in the aforementioned cells is known as sarcoplasmic reticulum.

7. The signal sequence that determines whether a protein will be synthesized on a free ribosome or ribosome attached to endoplasmic reticulum is located at _______
A. N-terminal
B. C-terminal
C. hydrophobic tail
D. hydrophilic tail
Answer: A
Clarification: There are two locations in a cell where a protein can be synthesized depending upon its type and function. The signal that directs the synthesis of a protein to a free ribosome or ribosome attached to the endoplasmic reticulum is found in the C-terminal of the protein.

8. In the image below, endoplasmic reticulum is depicted by ________

A. a
B. b
C. c
D. d
Answer: A
Clarification: The endoplasmic reticulum is a membranous structure containing sacs called cisternae. The organelle is associated with ribosomes and lies in close vicinity with the nucleus.

9. In yeast cells, protein transport across the endoplasmic reticulum membrane occurs __________
A. perpendicularly
B. discontinuously
C. co-translationally
D. post-translationally
Answer: D
Clarification: Polypeptide is synthesized in the ribosome and if appropriate signal is present in its C-terminal it moves to the ER membrane during the synthesis, this is called co-translational movement. In post-translational movement, the nascent polypeptide reaches the ER membrane after complete synthesis. Unlike mammalian cells post-translational movement of the polypeptides is observed in the yeast cells.

10. In mammalian cells, the signal recognition particle (SRP) consists of ____ distinct polypeptides and one small RNA molecule.
A. 2
B. 4
C. 6
D. 8
Answer: C
Clarification: The hydrophobic signal present in the nascent polypeptide is recognized by the SRP which then binds to the SRP receptor and transports the peptide to the endoplasmic reticulum membrane. The signal recognition particle (SRP) consists of 6 distinct polypeptides and one small 7S RNA.

11. Translocon is a ____________
A. polypeptide
B. protein channel
C. receptor
D. recognition particle
Answer: B
Clarification: Translocon is a protein-lined channel embedded in the membrane of the endoplasmic reticulum. The nascent polypeptide moves through this channel from the ribosome to the ER lumen.

12. Which of the following enzyme present in the rough endoplasmic reticulum removes the signal sequence from nascent polypeptides?
A. signal oxidase
B. signal peptidase
C. olisaccharyltransferase
D. luciferase
Answer: B
Clarification: After the nascent polypeptide reaches the cisterna of endoplasmic reticulum, it is acted upon by a variety of enzymes. One such enzyme is signal peptidase which removes the hydrophobic signal sequence from the peptide.

13. The cysteine residues present in the reduced form in peptides that enter the endoplasmic reticulum lumen are converted into ____________ when they leave the compartment.
A. hydrolyzed bonds
B. hydrophobic bonds
C. disulfide bonds
D. hydrophilic bonds
Answer: C
Clarification: Disulfide bonds play an important role in the stability of proteins. When the proteins enter ER lumen they contain cysteine residues in the reduced form (-SH) which is converted to oxidized disulfide bonds (-SS-) when they leave the ER, a reaction catalyzed by protein disulfide isomerase (PDI).

14. Hydrophobic transmembrane segments of which proteins are not synthesized in the endoplasmic reticulum?
A. integral membrane proteins
B. lysosomal proteins
C. steroids
D. secretory proteins
Answer: A
Clarification: Unlike secretory and lysosomal proteins, integral membrane proteins are not completely synthesized in the endoplasmic reticulum. One more or hydrophobic segment of these proteins are shunted directly from the translocon to the phospholipid bilayer.

15. Glycolipids are synthesized in the ER and ____________
A. Nucleus
B. Golgi complex
C. Mitochondrion
D. Plasma membrane
Answer: B
Clarification: Most membrane lipids are synthesized entirely in the endoplasmic reticulum with a few exceptions, one being glycolipids. The synthesis of glycolipids begins in the ER and completes in the Golgi complex.

Cell Biology Multiple Choice Questions on “Chemical Basis of Life – Acids, Bases and Buffers”.

1. Which of the following is released when a Hydrogen atom loses an electron?
A. Nucleus
B. Proton
C. Charge
D. Ion
Answer: B
Clarification: Whenever a hydrogen atom releases a shared electron in solution, a proton is also released. For example, acetic acid undergoes dissociation reaction to release acetate ion and a proton.

2. Which of the following is an example of amphoteric molecule?
A. Acetic acid
B. Malic acid
C. Sugars
D. Water
Answer: D
Clarification: Water is an example of both an acid and a base, and is therefore an amphoteric molecule. It can accept a proton thereby acting as a base and can also donate a proton acting as an acid.

3. Acids that lose a proton easily are weak acids.
A. True
B. False
Answer: B
Clarification: The strength of an acid is measured by the relative ease by which it loses a proton. The more readily the proton is lost, more strong is the acid. An example of a strong acid is Hydrogen Chloride which readily transfers its protons to water.

4. What is the full form of pH?
A. Positive hydrogen
B. Potential Hydrogen
C. Positron
D. Proton of hydrogen
Answer: B
Clarification: The acidity of a compound is measured by the concentration of hydrogen ions and is expressed in terms of pH- potential hydrogen. pH equals negative logarithmic concentration of protons.

5. A solution having a pH of 6 has a proton concentration of _______
A. 10^-6 M
B. 10⁶ M
C. 6 M
D. 0.6 M
Answer: A
Clarification: pH equals negative logarithmic concentration of protons. Since the pH scale is logarithmic, an increase of one pH unit corresponds to ten-fold decrease in hydrogen ion/ proton concentration.

6. What is the concentration of pure water?
A. 55.51 M
B. 25.51 M
C. 55 M
D. 25 M
Answer: A
Clarification: The concentration of pure water is always 55.51 Molar. On the basis of this universal value ion-product constant Kw for water is calculated, which is a constant value at 25℃.

7. In presence of an acid, amino group can be ____________
A. Polarized
B. Washed away
C. Protonated
D. Replaced
Answer: C
Clarification: In presence of an acid, amino group can be Protonated because an acid release proton, thereby increasing the hydrogen ion concentration in its vicinity and this can result in disruption of the protein activity to which amine group is attached.

8. Buffers react with _______________ ions.
A. hydrogen, hydroxyl
B. magnesium, calcium
C. potassium
D. sodium
Answer: A
Clarification: Buffers react with free hydrogen and free hydroxyl ions resisting changes in the pH and protecting cells and solutions from destroying. Buffers are also routinely used in laboratories.

9. Buffers usually contain ________________ with its conjugate ____________
A. weak base, acid
B. strong base, acid
C. weak acid, base
D. strong acid, base
Answer: C
Clarification: Buffers are used for resisting changes in the pH. A buffer usually contains a weak acid and its conjugate base. Even slight changes in pH can halt biological reactions.

10. Carbonic acid and bicarbonate ions buffer which of the following?
A. Cytosol
B. Cytoplasm
C. Blood
D. Lymph
Answer: C
Clarification: Carbonic acid and bicarbonate ions buffer the blood and hold its pH at 7.4. Carbonic acid is a weak acid and bicarbonate ions are basic in nature. A change in pH of the blood can lead to abnormalities.

Cell Biology Multiple Choice Questions on “Cellular Membranes – Lipids and Fluidity”.

1. Fluidity and viscosity are the same.
A. True
B. False
Answer: B
Clarification: Fluidity and viscosity are not the same and they are inversely related. Fluidity is a measure of ease of flow and viscosity is the resistance to flow.

2. Which of the following attributes of the membrane is most affected at the transition temperature?
A. size
B. fluidity
C. internal composition
D. internal environment
Answer: B
Clarification: At the transition temperature, the bilayer distinctly changes from liquid crystalline phase to crystalline gel. This occurs when the temperature is lowered from a standard warm temperature of 37⁰C.

3. The ___________ the degree of unsaturation of the fatty acids of the bilayer, the ___________ the temperature before the bilayer gels.
A. greater, lower
B. greater, more
C. lesser, higher
D. lesser, higher
Answer: A
Clarification: When the number of unsaturated fatty acids in the membrane is more, lower the transition temperature at which the membrane gels.

4. Which of the following molecules affects the mobility of fatty acyl chains in the plasma membrane?
A. starch
B. glycogen
C. cholesterol
D. carbohydrates
Answer: C
Clarification: Cholesterol disrupts the packing between fatty acyl chains and interferes with their mobility. It makes the membrane durable while decreasing the permeability of the membrane.

5. Which of the following occurs in the membrane, when the temperature is lowered?
A. denaturation
B. desaturation
C. saccharification
D. glycolysis
Answer: B
Clarification: When the temperature of the surrounding is lowered, the cells respond metabolically. Membrane remodeling takes place to make the cell more cold resistant. This takes place by desaturation of fatty acyl chains to form double bonds.

6. Lipid rafts are patches of cholesterol and ________________
A. carbohydrates
B. amino acids
C. lipids
D. sphingolipids
Answer: D
Clarification: Lipid rafts are the patches of cholesterol and sphingolipids. When membrane lipids are extracted from the membranes to synthesize artificial membranes in vitro, cholesterol and sphingolipids tend to self-assemble.

7. Cell fusion can be performed on two cells from different species.
A. True
B. False
Answer: A
Clarification: Cell fusion is a technique to fuse two cells from different species to form one cytoplasm and one single continuous plasma membrane.

8. In the experiments to demonstrate the mobility of membrane proteins, which cells were fused with human cells?
A. mouse cells
B. drosophila cells
C. tumor cells
D. bacterial cells
Answer: A
Clarification: The first experiments to demonstrate that membrane proteins can move within the plane of the membrane used fused cells of human and mouse. These were performed in 1970 at the John Hopkins University.

9. Which phenomena are made use of in the technique FRAP?
A. electrostatic
B. photothermal
C. hybridization
D. fluorescence
Answer: D
Clarification: Fluorescence recovery after photobleaching (FRAP) is a technique in which integral membrane proteins are labeled with a fluorescent dye, after which they are irradiated by a laser beam.

10. Which type of molecules are used in SPT?
A. organic dye
B. inorganic dye
C. antibodies
D. gold particles
Answer: D
Clarification: In the technique of single-particle tracking (SPT), individual membrane proteins are labeled with antibody conjugated gold particles and their movement is traced using computer-enhanced microscopy.

11. The use of optical tweezers in membrane biology was done to confirm the ________________ nature of membranes.
A. self-replicating
B. elastic
C. inelastic
D. photo-responsive
Answer: B
Clarification: 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.

12. The sperm cell is covered by a _____________
A. sheath
B. cell wall
C. continuous membrane
D. discontinuous membrane
Answer: C
Clarification: Of all the cells in mammals, sperms are the most highly differentiated. A mature sperm is divided into three regions head, midpiece and tail; all having their specific functions. The sperm is covered by a continuous plasma membrane that contains a mosaic of specialized domains.

13. Hemolysis is associated with which type of cells?
A. hepatocytes
B. germ cells
C. somatic cells
D. red blood cells
Answer: D
Clarification: 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.

14. Band 3 and glycophorins are membrane proteins that contain ________________
A. carbohydrates
B. sterols
C. lipids
D. nucleic acids
Answer: A
Clarification: Band 3 and glycophorins are carbohydrate-containing membrane proteins. Band 3 gets its name from the position in electrophoretic gel; it is present in the membrane as a homodimer.

15. Which is the first membrane protein to have its amino acid sequence determined?
A. Glycophorin A
B. Glycophorin B
C. Glycophorin C
D. Glycophorin D
Answer: A
Clarification: 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.

Cell Biology Multiple Choice Questions on “Chloroplast Structure and Function – Chloroplast and Photosynthetic Pigments”.

1. Who first discovered chloroplast?
A. J Rhodin
B. Robert Porter
C. Camillo Golgi
D. Konstantin Mereschkowski
Answer: D
Clarification: Chloroplast are small cell organelles found in both eukaryotic and some prokaryotic photosynthetic organisms. They were first discovered by Konstantin Mereschkowski in 1905.

2. What is the diameter of a chloroplast?
A. 1 – 2 micrometer
B. 2 – 4 micrometer
C. 4 – 6 micrometer
D. 6 – 10 micrometer
Answer: C
Clarification: Chloroplasts are generally 4 – 6 micrometer in diameter and 2 – 4 micrometer in thickness. These chloroplasts are round, oval and disc shaped organelles.

3. The mass of chloroplast DNA is __________
A. 10 – 15 million daltons
B. 50 – 100 million daltons
C. 80 – 130 million daltons
D. 25 – 125 million daltons
Answer: C
Clarification: The chloroplasts have their own DNA, which is circular in shape that forms a ring like structure. A single chloroplast DNA has a mass of about 80 – 130 million daltons.

4. The number of chloroplasts found in Arabidopsis thaliana is _____________
A. 100
B. 150
C. 50
D. 200
Answer: A
Clarification: Arabidopsis thaliana commonly known as mouse-ear cress has around 100 chloroplasts in each cell. The number of chloroplasts in each organism differ from species to species depending on the need of energy from photosynthesis.

5. Identify A and B from the below figure.

A. A – Lumen; B – Thylakoids
B. A – Thylakoids; B – Lumen
C. A – Stroma; B – Grana
D. A – Grana; B – Stroma
Answer: B
Clarification: Thylakoids resemble the structure of a coin, a stack of thylakoids looks like a stack of coins known as grana. The lumen is a connection between two or more grana.

6. The sunlight is captured by the membrane of thylakoids.
A. True
B. False
Answer: A
Clarification: The membrane of thylakoids is responsible for photosynthesis. They entrap the solar energy and provide it for the photosynthesis.

7. Which pigment is responsible for the process of sunlight?
A. Chlorophyll a
B. Chlorophyll b
C. Xanthophyll
D. Anthocyanin
Answer: A
Clarification: Chlorophyll a is the pigment, which primarily helps in photosynthesis. Xanthophyll and Anthocyanin are the pigments responsible for yellow and blue colour in plants respectively.

8. Which pigment constitutes majorly in absorbing sunlight for photosynthesis?
A. Chlorophyll a
B. Chlorophyll b
C. Xanthophyll
D. Anthocyanin
Answer: B
Clarification: Chlorophyll b is a pigment, which is yellow in colour. This pigment is responsible for the vast absorption of sunlight. It is present in the light absorbing antenna of the plants.

9. Which of the following organisms has photosynthetic pigments in it?
A. Yeast
B. Nitrosomonas
C. Spirulina
D. Phosphobacter
Answer: C
Clarification: The spirulina, which belongs to the community of cyanobacteria, commonly known as blue green algae, has photosynthetic pigments in it. They predominantly contain chlorophyll a.

10. What is the chemical formula of chlorophyll a?
A. C₄₅H₇₂MgN₄O₅
B. C₅₅H₇₂MgN₄O₅
C. C₅₅H₇₂MnN₄O₅
D. C₄₅H₇₂MnN₄O₅
Answer: B
Clarification: The chlorophyll a contains a magnesium ion complex, which forms a ring structure called the Chlorin ring. It has a molar mass of 893.51 g•mol⁻¹.

11. Chloroplast divide by binary fission.
A. True
B. False
Answer: A
Clarification: Chloroplasts cannot be synthesized by the cell itself. They have their own DNA and it divides by binary fission process like prokaryotes.

12. What disease is caused by the dysfunction of chloroplast?
A. Leaf spot
B. Blight spot
C. Leaf variegation
D. Powdery mildew
Answer: C
Clarification: Leaf variegation is caused by the deficiency of chloroplast due to mutation. Blight spot, Leaf spot and Powdery mildew are caused by fungi.

Cell Biology Multiple Choice Questions on “Cytoplasmic Membrane Systems – Golgi Complex”.

1. Golgi complex has a cisternae of diameter _________
A. 0.5-1 mm
B. 0.5-1 nm
C. 0.5-1 pm
D. 0.5-1 μm
Answer: D
Clarification: The Golgi complex was discovered by Camillo Golgi for which he was awarded Nobel Prize in 1908. It consists of flattened, disk-like membranous cisternae of diameter 0.5 to 1 μm.

2. Cis-Golgi network (CGN) is closer to the endoplasmic reticulum than the trans-Golgi network (TGN).
A. True
B. False
Answer: A
Clarification: Cis-Golgi network is the entry face closes to endoplasmic reticulum (ER) and trans-Golgi network is the opposite face to the ER. The CGN primary functions to sort out the proteins that are to be sent back to ER and those that proceed further in the Golgi complex.

3. Which of the following parts of Golgi complex directs the proteins to their final intracellular destinations?
A. tubules
B. cis-Golgi network
C. trans-Golgi network
D. medial cisternae
Answer: C
Clarification: Trans-Golgi network (TGN) is the final station in the Golgi complex where the proteins are sorted out based on their final intracellular destinations.

4. Which protein families do not mechanically support the Golgi complex?
A. Keratin
B. Actin
C. Spectrin
D. Ankyrin
Answer: A
Clarification: The Golgi complex is mechanically supported by a scaffold or a peripheral membrane skeleton consisting of a variety of protein families – ankyrin, actin, spectrin.

5. Newly synthesized membrane proteins enter the cis face of the Golgi complex and leave from the trans face.
A. True
B. False
Answer: A
Clarification: The newly synthesized membrane and lysosomal proteins from the endoplasmic reticulum enter the Golgi complex through the cis face and reach the trans face, getting modified throughout the way.

6. Which of the following is located at the trans end of the Golgi stack?
A. ascorbic acid
B. methanoic acid
C. sialyl-transferase
D. dehydrogenase
Answer: C
Clarification: The enzyme sialyl-transferase is located at the trans face of the Golgi stack and it places sialic acid at the terminal position of the glycoprotein chains.

7. Which of the following is not completely synthesized in the Golgi complex of a cell?
A. Pectins
B. Hemicellulose
C. N-linked oligosaccharides
D. O-linked oligosaccharides
Answer: C
Clarification: Pectins and hemicelluloses found in the plant cell wall as well as O-linked oligosaccharides are synthesized completely in the Golgi complex. The synthesis of N-linked oligosaccharides begins in the endoplasmic reticulum (ER).

8. How many models of movement of materials through the Golgi complex exist?
A. 1
B. 2
C. 3
D. 4
Answer: B
Clarification: There two models with contrasting views on the movement of materials through the Golgi complex namely “Cisternal maturation model” and “Vesicular transport model”.

9. What is responsible for the transport of materials from the cis cisternae to the trans cisternae of the Golgi complex?
A. active diffusion
B. passive diffusion
C. translocon
D. transport vesicles
Answer: D
Clarification: The materials such as membrane proteins and other proteins are transported from the cis cisternae to the trans cisternae by means of vesicles that bud from the rims of cisternae stack.

10. While moving from cis cisternae to the trans cisternae, which molecule does not leave the cisternal lumen?
A. membrane proteins
B. procollagen
C. oligosaccharides
D. lysosomal proteins
Answer: B
Clarification: Procollagen molecules are the precursors of extracellular collagen found in fibroblasts. They move from cis cisternae to the trans cisternae without ever leaving the cisternal lumen.