BIO110 Connect, Biology
Indicate if the following statements about membrane proteins are true or false. 1. They can aid in the transportation of molecules across membranes. 2. They are used in DNA replication. 3. They can act as cell surface receptors. 4. They are totally water soluble. 5. They can be enzymes.
1. True 2. False 3. True 4. False 5. True
Describe the main components of a biological membrane by filling in the missing terms. Small amphipathic ______(1)______ are the most abundant molecules in a membrane. Larger ______(2)______ make up half of the mass of a membrane. Polar ______(3)______ are typically found attached to the outside of a membrane.
1. phospholipids 2. proteins 3. carbohydrates
0.2 mL of 2 mM sodium chloride added to 1.0 L water vs. 0.2 mL of 2 M sodium chloride added to 1.0 L wate
2 M Sodium Chloride
A single Na+/K+ ATPase pump is present in the plasma membrane of an artificial cell with an initial cellular environment of 1000 molecules of Na+ and 1000 molecules of ATP inside the cell, 1000 molecules of K+ outside the cell, and a net charge differential across the plasma membrane of 0. Assuming the only changes in the cellular environment are a result of the pump's actions, what would be the number of Na+, K+, and ATP molecules inside the cell after 100 cycles of the pump, and what would be the net charge differential (inside-outside) across the plasma membrane?
700 Na+; 200 K+; 900 ATP and −200 charge differential (inside-outside)
Administration of digoxin is not the only way to treat atrial fibrillation. From the list below, select all other plausible strategies to increase intracellular calcium concentrations. A)Administer a different inhibitor of the Na+/Ca2+ antiporter B)Administer an inhibitor of the Ca2+-ATPase pump, which removes Ca2+ from the cytosol C)Administer calcium chelators to reduce the extracellular Ca2+ concentration D)Administer calcium chloride to raise the extracellular Ca2+ concentration
A)Administer a different inhibitor of the Na+/Ca2+ antiporter B)Administer an inhibitor of the Ca2+-ATPase pump, which removes Ca2+ from the cytosol D)Administer calcium chloride to raise the extracellular Ca2+ concentration
N-linked protein glycosylation Which of the following is true of N-linked protein glycosylation? A)The carbohydrates are first attached to the lipid dolichol. B)It occurs entirely in the Golgi apparatus. C)It occurs primarily on proteins that are not secreted out of the cell. D)The carbohydrates are attached directly to the protein.
A)The carbohydrates are first attached to the lipid dolicho
Analyze a Defective Na+/K+ ATPase A defective Na+/K+ ATPase pump is isolated from a plasma membrane and studied. Careful measurements in the laboratory determine that the pump is able to hydrolyze ATP and transports 3 Na+ ions across the plasma membrane. The pump is also able to bind 2 K+ ions with high affinity. However, the pump is unable to shuttle K+ ions across the plasma membrane. Based on these observations, what is the most likely cause of the defect in this pump? A)The defective pump is unable to release phosphate B)The defective pump is locked into a rigid conformation and is unable to undergo conformational changes C)The defective pump is unable to release Na+ ions D)The defective pump is unable to bind K+ ions E)The defective pump is unable to bind ATP
A)The defective pump is unable to release phosphate
Describe the Na+/K+ ATPase Pump A)The sodium-potassium pump functions to pump sodium ions out of the cell and potassium ions into the cell. B)sodium ions into the cell and potassium ions out of the cell. C)sodium and potassium ions into the cell. D)sodium and potassium ions out of the cell. E)sodium and potassium ions in both directions across the cell membrane.
A)The sodium-potassium pump functions to pump sodium ions out of the cell and potassium ions into the cell.
Energy Source for Na+/K+ Pump What is the source of energy used to power the sodium-potassium pump? A)hydrolysis of ATP B)formation of ATP C)binding of ATP D)release of phosphate E)diffusion of Na+ down its gradient
A)hydrolysis of ATP
Small amphipathic___________ are the most abundant molecules in a membrane. A)phospholipids B)Nucleci acids C) Carbohydrates D) proteins
A)phospholipids
Membrane Permeability and Facilitated Diffusion Which of the following molecules are most likely to pass through the membrane by facilitated diffusion? A)urea and sucrose. B)H2O and O2. C)CO2 and O2. D)CO2 and H2O.
A)urea and sucrose.
The loss of what enzyme would be lethal to the cell?
Acyl transferase
The loss of this enzyme would result in membranes deficient in phosphatidylcholine
Choline phototransferase
The hormone insulin is a protein produced in the pancreas and then secreted into the blood stream after a meal to increase glucose uptake by tissues. Which of the following mechanisms would be used to secrete insulin from the pancreas? A)Active transport B)Facilitated diffusion C)Diffusion D)Endocytosis E)Exocytosis
E)Exocytosis
Secondary Active Transport of Sucrose Sugars can be transported into cells against their concentration gradient because of A)osmosis. B)simple diffusion. C)facilitated diffusion. D)antiport with Na+. E)symport with Na+.
E)symport with Na+.
Determine if each statement applies to facilitated diffusion, active transport, or both.
FACILITATED DIFFUSION: -Molecules move down their concentration gradient. ACTIVE TRANSPORT: -Molecules move against their concentration gradient. -Requires energy. BOTH: -Molecules move through a transport protein in the membrane. -Transport proteins are specific for the structures of individuals molecules.
Compare Facilitated and Simple Diffusion Unlike simple diffusion, facilitated diffusion requires energy expenditure by the cell. True False
FALSE
Unlike simple diffusion, facilitated diffusion requires energy expenditure by the cell.
False
0.2 mL of a 2 mM solution of the enzyme carbonic anhydrase added to 1.0 L water vs. 0.2 mL of 2 mM sodium chloride added to 1.0 L water
Sodium Chloride
The osmolarity of human plasma is a measure of the total amount of dissolved ions and proteins in the blood. The normal range for plasma osmolarity is 285-295 mOsm/L. Why can an injection of a 600 mOsm/L solution directly into a patient's bloodstream be very painful and dangerous?
The injection is hypertonic relative to blood causing cells to shrivel and become crenated.
Iron is important for the proper function of erythrocytes (i.e., red blood cells) and is transported in the blood plasma by a glycoprotein called transferrin. There are many transferrin-specific receptors on the surface of red blood cells. Based on this information, what is the primary means by which iron enters into erythrocytes?
The iron-transferrin complex enters by receptor-mediated endocytosis
If a cell is placed in an isotonic medium, there will be no net movement of water.
True
Facilitated diffusion requires a. enzymes. b. carrier proteins. c. lipid carriers. d. carbohydrate carriers. e. lipid or carbohydrate carriers.
b. carrier proteins.
Exocytosis is a process by which cells a. release substances from the cell through pores in the cell membrane. b. release substances from the cell via vesicles. c. release substances from the cell via carrier proteins. d. bring in substances from the outside via vesicles. e. bring in substances from the outside via pores in the cell membrane.
b. release substances from the cell via vesicles.
Which of the following is the most direct source of energy for cotransport? a. the movement of one of the transported substances up its concentration gradient b. the movement of one of the transported substances down its concentration gradient c. ATP hydrolysis d. ATP formation e. cotransport requires no energy
b. the movement of one of the transported substances down its concentration gradient
Aquaporin allows water molecules to move very rapidly across a plasma membrane. What would be the best definition of this process? a. Facilitated diffusion using a transporter b. Active transport using a transporter c. Facilitated diffusion using a channel d. Active transport using a channel
c. Facilitated diffusion using a channel
Of the three basic types of endocytosis, what is a unique feature of receptor-mediated endocytosis? a. it is used to transport material into the cell b. it is non-specific c. it involves clathrin-coated pits d. it involves transport of material into e. the cell through pores in the cell membrane e. it can be used both to import and export materials
c. it involves clathrin-coated pits
Sea water is approximately 3% salt. Sea water is hypertonic to tissues of freshwater fish. Their tissue contain - a. 3% salt b. more than 3% salt c. less than 3% salt
c. less than 3% salt
Red blood cells put in a hypertonic solution will a. not be affected in any way. b. form linear edges. c. shrivel and become crenated. d. be destroyed by hemolysis.
c. shrivel and become crenated.
Sugars can be transported into cells against their concentration gradient because of a. osmosis. b. simple diffusion. c. facilitated diffusion. d. antiport with Na+. e. symport with Na+.
e. symport with Na+.
The loss of this enzyme would severely reduce the exchange of lipids between the cytosol and the lumen
flippase
simple diffusion examples
gasses, ethanol, and small non polar molecules
Loss of these enzymes would prevent lipid transfer between the ER and mitochondria
lipid exchange proteins
Erythrocytes from an isotonic blood transfusion are transferred to an individual with abnormally high sodium in the blood. The most likely impact on the erythrocytes in this transfusion is
water will diffuse out of the cell, causing the cells to crenate
The Energetics of Coupled Transport Sucrose concentration is higher in the cytoplasm than in the extracellular environment. Na+ concentration is higher in the extracellular environment than in the cytoplasm. Animal cells can take up sucrose against its concentration gradient using a Na+/sucrose symporter. Indicate if the following statements are true or false. A. In the Na+/sucrose symporter, Na+ is also moving against its concentration gradient. B. For the symporter to work, the cell must first establish a Na+ concentration gradient. C. A symporter works by making the phospholipid bilayer more permeable to ions and sucrose. D. Moving sucrose against its concentration gradient is a form of active transport. E. A Na+/sucrose antiporter would be capable of moving sucrose into the cell while moving Na+ out of the cell. F. Since the Na+/sucrose symporter exchanges a single sucrose for a single Na+, it can also be considered a uniporter
A. In the Na+/sucrose symporter, Na+ is also moving against its concentration gradient.FALSE B. For the symporter to work, the cell must first establish a Na+ concentration gradient. TRUE C. A symporter works by making the phospholipid bilayer more permeable to ions and sucrose. FALSE D. Moving sucrose against its concentration gradient is a form of active transport. TRUE E. A Na+/sucrose antiporter would be capable of moving sucrose into the cell while moving Na+ out of the cell. FALSE F. Since the Na+/sucrose symporter exchanges a single sucrose for a single Na+, it can also be considered a uniporter. FALSE
Mammals like caribou that live in the arctic often have different lipids in the cells of their legs compared to the cells of their internal organs. Their legs get colder than their internal organs, which stay warmer. Indicate true or false which of the following adaptations you would expect to find in the lipids found in the cells of the legs of a caribou? A. The lipids would be more saturated. B. The fatty acyl tails of the phospholipids would be shorter. C. The membranes would contain more cholesterol
A. The lipids would be more saturated. FALSE B. The fatty acyl tails of the phospholipids would be shorter. TRUE C. The membranes would contain more cholesterol. TRUE
Membrane proteins Indicate if the following statements about membrane proteins are true or false. A. They can aid in the transportation of molecules across membranes. B. They are used in DNA replication. C. They can act as cell surface receptors. D. They are totally water soluble. E. They can be enzymes
A. They can aid in the transportation of molecules across membranes. TRUE B. They are used in DNA replication. FALSE C. They can act as cell surface receptors. TRUE D. They are totally water soluble. fFALSE E. They can be enzymes. TRUE
Health Implications of Facilitated Diffusion GLUT1 is a glucose transporter that is responsible for the facilitated diffusion of glucose across the blood-brain barrier. GLUT1 deficiency syndrome is a rare genetic disorder where mutations in the gene encoding GLUT1 reduce or eliminate the function of the GLUT1 protein. Affected individuals suffer from seizures along with a number of potential neurological problems. What is the link between GLUT1 dysfunction and these neurological complications? A)diffusion of glucose from the brain to the blood B)sporadic and uncontrolled diffusion of glucose from the blood to the brain C)excessive and constant diffusion of glucose from the blood to the brain D)insufficient diffusion of glucose from the blood to the brain
B) insufficient diffusion of glucose from the blood to the brain
Digoxin is an inhibitor of Na+/K+ ATPase that is used to treat irregular heartbeats (medical term: atrial fibrillation). Digoxin slows the heartbeat by raising intracellular calcium levels. What is the most reasonable explanation for how digoxin can raise intracellular calcium concentrations through inhibiting Na+/K+ ATPase? A)Na+/K+ ATPase acts to shuttle Ca2+ out of the cell. Digoxin inhibits Na+/K+ ATPase, preventing it from shuttling Ca2+ out of the cell. As a result, intracellular Ca2+ levels increase. B)Inhibiting Na+/K+ ATPase results in a lower than normal intracellular Na+ concentration. This reduces the effectiveness of the Na+/Ca2+ antiporter. As a result, intracellular Ca2+ levels increase. C)Inhibiting Na+/K+ ATPase results in a higher than normal intracellular Na+ concentration. This reduces the effectiveness of the Na+/Ca2+ antiporter. As a result, intracellular Ca2+ levels increase. D)Inhibiting Na+/K+ ATPase results in a lower than normal extracellular K+ concentration. This increases the effectiveness of a K+/Ca2+ symporter that drives the influx of both K+ and Ca2+. As a result, intracellular Ca2+ levels increase.
B)Inhibiting Na+/K+ ATPase results in a lower than normal intracellular Na+ concentration. This reduces the effectiveness of the Na+/Ca2+ antiporter. As a result, intracellular Ca2+ levels increase.
Compensating for Disfunction in Facilitated Diffusion GLUT1 deficiency syndrome is a rare genetic disorder where mutations in the gene encoding GLUT1 reduce or eliminate the function of the GLUT1 protein. Affected individuals suffer from seizures along with a number of potential neurological problems. What would be the most effective therapy to treat patients suffering from this disorder? A)Treat with drugs that will elevate ATP levels in the blood-brain barrier and promote the active transport of glucose by GLUT1 B)Switch to a diet containing carbohydrates other than glucose to circumvent the deficient transport C)Switch to a high glucose diet to overcome the deficient transport D)Regularly inject GLUT1 into the patient's blood to serve as a replacement for the deficient transporter
B)Switch to a diet containing carbohydrates other than glucose to circumvent the deficient transport
Requirements of Facilitated Diffusion Facilitated diffusion requires A)enzymes. B)carrier proteins. C)lipid carriers. D)carbohydrate carriers. E)lipid or carbohydrate carriers.
B)carrier proteins
Which of the following is the most direct source of energy for cotransport? A)the movement of one of the transported substances up its concentration gradient B)the movement of one of the transported substances down its concentration gradient C)ATP hydrolysis D)ATP formation E)cotransport requires no energy
B)the movement of one of the transported substances down its concentration gradient
Calculated the Charge Differential after Multiple Pump Cycles A single Na+/K+ ATPase pump is present in the plasma membrane of an artificial cell with an initial cellular environment of 500 molecules of Na+ and 1000 molecules of ATP inside the cell, 500 molecules of K+ outside the cell, and a net charge differential across the plasma membrane of 0. Assuming the only changes in the cellular environment are a result of the pump's actions, what would be the number of Na+, K+ and ATP molecules inside the cell after 10 cycles of the pump and what would be the net charge differential (inside - outside) across the plasma membrane? A)30 Na+; 20 K+; 900 ATP and -10 charge differential (inside - outside) B)30 Na+; 480 K+; 10 ATP and +20 charge differential (inside - outside) C)470 Na+; 20 K+; 990 ATP and -20 charge differential (inside - outside) D)300 Na+; 200 K+; 100 ATP and -100 charge differential (inside - outside) E)470 Na+; 480 K+; 10 ATP and +100 charge differential (inside - outside)
C) 470 Na+; 20 K+; 990 ATP and -20 charge differential (inside - outside)
Evaluate the Relative Impact of Na+/K+ ATPase Disfunction Which of the following dysfunctions in the Na+/K+ ATPase will have the most dramatic effect on the establishment of a concentration gradient? A)A reduction in the ability of ATP to bind to the pump B)A decrease in the Na+ binding affinity for the phosphate-bound form C)A reduction in the rate of ATP hydrolysis D)An increase in the K+ binding affinity in the phosphate-bound form
C) A reduction in the rate of ATP hydrolysis
Polar_____are typically found attached to the outside of a membrane. A)phospholipids B)Nucleci acids C) Carbohydrates D) proteins
C) Carbohydrates
Receptor Mediated Endocytosis Lipoproteins like LDL and HDL transport lipids and proteins through the blood stream. Receptors on cells can bind to the lipoproteins and remove them from the blood, using the lipids for energy and to produce membranes. Which of the following mechanisms would be used to move a lipoprotein into a cell? A)Active transport B)Facilitated diffusion C)Receptor-mediated endocytosis D)Endocytosis E)Exocytosis
C) Receptor-mediated endocytosis
Aquaporin allows water molecules to move very rapidly across a plasma membrane. What would be the best definition of this process? A)Facilitated diffusion using a transporter B)Active transport using a transporter C)Facilitated diffusion using a channel D)Active transport using a channel
C)Facilitated diffusion using a channel
Pumps The plasma membrane Ca2+-ATPase is a pump that functions in the primary active transport of Ca2+ out of the cell. What features do you expect of this pump and the cellular environment? Choose all that apply. A)It transports Na+ and K+ ions B)It is an antiporter C)The extracellular Ca2+ concentration is higher than the intracellular Ca2+ concentration D)It hydrolyzes ATP E)It is capable of undergoing a conformational change F)The affinity for Ca2+ is low when the enzyme is bound to phosphate G)It transports Ca2+ down its concentration gradient
C)The extracellular Ca2+ concentration is higher than the intracellular Ca2+ concentration D)It hydrolyzes ATP E)It is capable of undergoing a conformational change F)The affinity for Ca2+ is low when the enzyme is bound to phosphate
Larger ____________ make up half of the mass of a membrane. A)phospholipids B)Nucleci acids C) Carbohydrates D) proteins
D) proteins
Fluid mosaic model of membrane structure Which of the following is true of the fluid mosaic model of membrane structure? A)Membranes behave more like a solid than a liquid. B)Lipids can flip from one leaflet to another as easily as they can move laterally in a membrane. C)Proteins can easily move across membranes. D)Proteins can easily move laterally through membranes.
D)Proteins can easily move laterally through membranes.
A toxin that disrupted membrane antiport would prevent A)simultaneous movement of an amino acid and protons into the cell B)simultaneous movement of an amino acid and protons out of the cell C)coupling of the inward movement of water with the outward movement of protons D)coupling the outward movement of Ca2+ with the inward movement of Na+
D)coupling the outward movement of Ca2+ with the inward movement of Na+
Low-density lipoprotein (LDL) enters the cell via receptor-mediated endocytosis. What is the most likely reason why LDL is not simply transported into the cell using a channel or transporter protein?
LDL is too large for a channel or transporter protein
Which of the following molecules are most likely to pass through the membrane by facilitated diffusion? a. H2O and sucrose b. H2O and O2. c. CO2 and O2. d. CO2 and H2O.
a. H2O and sucrose
Simple diffusion is defined as the movement of a. molecules from areas of higher concentration to areas of lower concentration. b. molecules from areas of lower concentration to areas of higher concentration. c. water molecules across a membrane. d. gas molecules across a membrane. e. gas or water molecules across a membrane.
a. molecules from areas of higher concentration to areas of lower concentration.
When sugar is mixed with water, equilibrium is reached when Required information View the animation below, then complete the quiz to test your knowledge of the concept. Play Video When sugar is mixed with water, equilibrium is reached when a. molecules of sugar stop moving. b. water and sugar molecules are moving at the same speed. c. the dissolved sugar molecules are evenly distributed throughout the solution. d. there is the same number of water molecules as dissolved sugar molecules. e. water and sugar molecules are at an equal concentration.
c. the dissolved sugar molecules are evenly distributed throughout the solution.
A phospholipid will laterally diffuse in a plasma membrane faster than an integral membrane protein. What is the simplest explanation for this phenomenon? a. A phospholipid is more hydrophobic than an integral membrane protein b. A phospholipid has greater rotational movement than an integral membrane protein c. The enzyme Flippase can rapidly flip phospholipids across the bilayer but it cannot do the same for integral membrane proteins d. A phospholipid is smaller than an integral membrane protein
d. A phospholipid is smaller than an integral membrane protein
Which of the following is true of the fluid mosaic model of membrane structure? a. Membranes behave more like a solid than a liquid. b. Lipids can flip from one leaflet to another as easily as they can move laterally in a membrane. c. Proteins can easily move across membranes. d. Proteins can easily move laterally through membranes.
d. Proteins can easily move laterally through membranes.
Red blood cells put in a hypotonic solution will a. not be affected in any way. b. form linear edges. c. shrivel and become crenated. d. be destroyed by hemolysis
d. be destroyed by hemolysis
Certain white blood cells engulf microorganisms and digest them within the cell. A mutation that prevents this internalization would directly affect a. pinocytosis. b. osmosis. c. receptor-mediated exocytosis. d. phagocytosis. e. diffusion.
d. phagocytosis.
Osmosis is best defined as the movement of a. molecules from an area of high concentration to an area of lower concentration. b. molecules from an area of low concentration to an area of higher concentration. c. water molecules across a membrane from an area of low water to an area of higher concentration. d. water molecules across a membrane from an area of high water concentration to an area of lower concentration.
d. water molecules across a membrane from an area of high water concentration to an area of lower concentration.
The hormone insulin is a protein produced in the pancreas and then secreted into the blood stream after a meal to increase glucose uptake by tissues. Which of the following mechanisms would be used to secrete insulin from the pancreas? a. Active transport b. Facilitated diffusion c. Diffusion d. Endocytosis e. Exocytosis
e. Exocytosis
A cube of sugar in hot coffee vs. a cube of sugar in room temperature coffee
hot coffee
The loss of what enzyme would lead to membrane phospholipids with identical phosphate head groups?
phosphate
One gram of sodium chloride will take longer to dissolve in a solution of 2 M glucose than in a solution of pure water. What is the most reasonable explanation for this observation
sodium chloride will encounter a greater frequency of collisions in a 2 M glucose solution than in water, slowing its diffusion
facilitated diffusion examples
sugars, salts, proteins