I. Cell questions
Cell biology practice questions
There are a total of 72 cell biology practice questions, which are important content-oriented in the summary part of this chapter. Click the ‘Answer’ button to see the corresponding answers and explanations, and click the ‘Go back’ button to slove the next questions.
13. Which combination of the following describes RNA?
Answers
1. E
Monosaccharides are glucose, fructose, galactose, and ribose. Disaccharides are sucrose, maltose, and lactose. Polysaccharides are starch, glycogen, cellulose, and chitin.
2. D
All of the above except D belong to the subcategory of lipid. Glycogen polymerized glucose in animals belongs to the subcategory of sugar.
3. E
Main functions of vacuole are the storage of nutrients and waste molecules. Also, it is involved in the functions of keeping internal pH and osmotic balance.
4. B
Gap junction, which consists of pored membrane proteins, communicates with heart muscle cells and animal embryo cells.
7. A
Metabolism means the energy property of the chemical reaction to maintain a living organism. Metabolism has two pathways, the catabolic pathway and the anabolic pathway. Anabolic pathway is building complicated molecules from simple units.
8. A
Enzymes are biological catalysts, increasing the chemical reaction by lowering the activation energy without being used up.
9. E
During glycolysis, one glucose is converted into two pyruvates in cytosol. 2ATP are invested and 4ATP are harvested, so net 2ATP are harvested. Other harvesting products are 2NADH, 2H+, 2H2O.
11. B
The elements of protein are C, H, O, N, S and the elements of nucleotide are C, H, O, N, P. S (sulfate) is the least abundant element in living cells.
13. D
RNA and DNA strands are nucleic acids but RNA has unique characteristics, which are ribose sugar, uracil of bases, and single strand. Both DNA and RNA strands are linked by phosphodiester bonds.
14. B
Endocrine is the release of extracellular signals (hormones) into blood cells. Paracrine is local distance and diffusing signal through extracellular matrix to near target cells.
15. C
Receptors binding hydrophobic hormones such as steroid hormones are found inside of a cell and called intracellular reception.
16. E
Active transport means movement of substances from a low concentration area to a high concentration area such as sodium-potassium or electrogenic pump.
17. B
In hypotonic conditions water moves from outside the cell to inside the cell, and plants become turgid.
18. C
Reversal of internal conditions against outside environment change is called negative feedback. Positive feedback is change of internal conditions in the same direction as outside environmental change.
20. C
The activity of enzymes is influenced by the concentration of reactants, pH level, and temperature.
21. C
The light dependent reactions occur at the thylakoid membrane in chloroplasts and produce O2, ATP, and NADPH. The light independent reactions occur in stroma and produce glucose.
22. D
O2 is the final electron acceptor in the electron transport chain during cellular respiration. H2O splits into O2 and 2H+ in the photosystem II. The final product of the photosystem II is ATP and the product of the photosystem I is NADPH. During ATP synthesis in chloroplasts, H+ ions are diffused from lumen (thylakoid space) to stroma as an outward reaction, while during ATP synthesis in mitochondria, H+ ions are diffused from intermembrane space to mitochondrial matrix as an inward reaction. ADP can not move through the thylakoid membrane.
23. D
Glycolysis happens in the cytosol of cells. During fermentation process, lactate and ethanol are made and ATP energy is produced in the absence of oxygen. Krebs cycle works at aerobic metabolism in mitochondria.
25. D
Cell membranes are composed of phospholipids forming bilayers (hydrophilic and hydrophobic).
26. C
Phospholipid forms amphipathic bilayers of cell membranes. Triacylglycerol is a fat molecule, which is composed of glycerol and three fatty acid units. Cellulose is connected by microfibrils and is a component of cell walls of plants. Chitin, a nitrogenous sugar,is an important component of the cell walls of fungi.
27. B
Microtubules are components of centrosomes and centrioles. Microfilaments are two intertwined stranded structures used in myosin and actin filaments in muscle cells. Intermediate filaments have tensile strength from fibrous proteins and are used in protein subunits (keratin filaments) or formation of unclear lamina.
28. A
Active or inactive enzymes are regulated by phosphorylation, which involves protein kinases and phosphatases. Proteins that are inactivated by losing phosphate groups are a result of protein phosphatases.
31. E
Endocytosis means the movement of liquid, particles, and molecules by pinocytosis, phagocytosis, and receptor-mediated endocytosis. Autophagy means breaking down damaged organelles by lysosomes containing hydrolytic enzymes. Secretion means the movement of molecules from the inside to the outside of a cell.
33. B
The product of the Calvin cycle is G3P (glucose) and the products of the Krebs cycle are ATP, CO2, NADH, FADH.
34. E
Rubisco enzyme is used in the Calvin cycle to bind to RuBP and CO2 to make PGA, but acetyl CoA, which is combined with oxaloacetate acid to become citrate, is used in the citric acid cycle.
36. A
Fermentation is anaerobic respiration in cytosol. During fermentation ethanol, lactate, and NAD+ are produced. Production of lactate occurs in muscle cells. The production of Acetyl CoA happens in mitochondria. Regeneration of NADP+ occurs in chloroplasts.
37. E
All statements of above are common features of both mitochondria and chloroplasts except E. Mitochondria requires O2 as final electron receptors.This is found only in aerobic cellular conditions.
39. A
Primary structure uses only peptide bonds to form the linear of amino acids sequences, and secondary structure forms alpha helix and beta-pleated sheets using hydrogen bonds. Tertiary structure is formed by disulfide bonds, ionic bonds, hydrophobid interaction, and hydrogen bonds.
40. E
Endomembrane systems are involved in transport of protein and metabolic functions. This system contains nuclear envelope, rough ER, smooth ER, transport vesicles, golgi complex, lysomes, vacuoles, and cell membrane. Peroxisomes are not part of endomembrane system.
41. E
Ribosomes, cytoskeletons, and cell walls are present in both prokaryotic and eukaryotic cells. Nucleoids may be present in only prokaryotic cells. Centrioles and lysosomes appear in eukaryotic animal cells.
42. C
Pinocytosis engulfs liquid by the membrane and phagocytosis engulfs particles by the membrane. Endocytosis is the movement of large molecules into the membrane and exocytosis is the ejection of stuff outside the membrane.
43. C
The reaction of converting water and carbohydrates into glucose and oxygen is an endergonic reaction, whereas the opposite of this reaction is an exergonic reaction.
45. A
Chlorophyll is a primary pigment, which reflects blue-green light and absorbs violet-blue and red light. Chlorophyll b reflects green-yellow light as an accessory pigment. Carotenoid is also an accessory pigment and reflects yellow-red light.
46. C
The original source of electron is H2O, which is split into electron, hydrogen, and oxygen at photosystem II.
50. D
Correct steps on the scientific method:
Observation → hypothesis → predictions → experimentation → controls → conclusion
52. B
Chloroplast, mitochondria, and nucleus have a double membrane. Lysosome, smooth and rough ER, golgi complex, and peroxisome have a single membrane. Centriole and ribosome do not have membrane.
53. D
During competitive inhibition, since the inhibitor is bound to the active site the substrate cannot be bound to the active site. Substrates always can be bound to the active site.
54. B
C4 plants adapted in hot and dry conditions have spatial separations to fix CO2 in mesophyll cells for the working of the Calvin cycle in bundle sheath cells such as sugarcane and corn.
55. C
Spatial separation occurs in C4 plants. CAM plants have temporal separation (day and night) that CO2 enters into stomata during the night and then the Calvin cycle works with closed stomata during the day.
56. D
One glucose produces 2ATP in glycolysis, 2ATP in the citric acid (Krebs) cycle, and 32-34ATP in the electron transport chain.
57. B
Acetyl CoA is produced inside mitochondria membranes. In the cytoplasm ATP and pyruvates are produced by glycolysis, and ethanol and lactate are produced by fermentation.
58. D
Amino acid, a subunit of protein, is composed of an amino group, a carboxyl group, a functional group, α carbon, and hydrogen. It is not formed by dehydration synthesis.
59. D
Eukaryotic cells reproduce by mitotic and meiotic division and have internal membranous organelles such as nucleus and mitochondria. Prokaryotic cells reproduce asexually by binary fission and lack internal membranous organelles such as nucleoid and ribosome.
60. D
Chloroplasts synthesizing ATP do not belong to animal cells. Inside the double membranes of mitochondria is the called matrix, which is found in both animal and plant cells.
61. E
Substructures of chloroplasts are grana and stroma. The thylakoid disk, a single structure of the granum, contains thylakoid membrane and lumen. The thylakoid membrane contains photosystems and chlorophyll.
62. E
H2O, a source of electrons, is broken down into H+ and O2 at photosystem II. The final product of photosystem II is ATP, which is derived from the electron transport system.
65. D
Mitochondria and chloroplast are double membranes. Aerobic cellular respiration and CO2 production are characteristics of mitochondria only. Only chloroplasts produce NADPH.
67. D
The second messenger IP3 derived from PIP2 is bound to IP3-gated calcium channel to flow out Ca2+ from Endoplasmic Reticulum to cytosol.
68. B
Reduction is gaining hydrogen (electron) or losing oxygen, whereas oxidation is losing hydrogen (electron) or gaining oxygen. A, C, and D are gaining oxygen, thus they are oxidation.
69. C
Oxidative phosphorylation is the process of electron transport and chemiosmosis. ATP synthesis happens in chemiosmosis, which is located at thylakoid membrane in chloroplast and at inner membrane in mitochondria. Ubiquinone and cytochrome C carry electrons in the electron transport chain.
70. A
The citric acid cycle, also called the Krebs cycle, happens at the matrix of mitochondria. The Calvin cycle reaction occurs in stroma of chloroplasts.
72. C
The locomotion of H+ across a membrane through ATP synthase in chloroplast and mitochondrion is facilitated diffusion. The direction of H+ movement across the mitochondria membrane is from intermembrane space into matrix.