Biology 1401: Chapter 5 Membranes
- 1.
The plasma membrane is a thin sheet of phosphate lipid embedded with
- A.
Proteins
- B.
Carbohydrates
- C.
Polymers
- D.
Nucleotides
- E.
Sodium and potassium ions
Correct Answer
A. ProteinsExplanation
The plasma membrane is composed of a thin sheet of phosphate lipid that is embedded with proteins. These proteins play a crucial role in various cellular processes such as transport of molecules, cell signaling, and cell adhesion. They also act as receptors for hormones and other signaling molecules. Additionally, some proteins in the plasma membrane form channels that allow the passage of specific ions and molecules. Therefore, proteins are an essential component of the plasma membrane and are responsible for its structure and function.Rate this question:
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- 2.
If a cell has the same concentration of dissolved molecules as of its outside environment, the cell's condition is called as being
- A.
Isotonic
- B.
Hypertonic
- C.
Hypotonic
- D.
Hydrophobic
- E.
Hydrophilic
Correct Answer
A. IsotonicExplanation
When a cell has the same concentration of dissolved molecules as its outside environment, it is in an isotonic condition. In an isotonic solution, there is no net movement of water across the cell membrane, as the concentration of solutes inside and outside the cell is balanced. This means that the cell maintains its shape and size without gaining or losing water.Rate this question:
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- 3.
Which of the following does not influence membrane fluidity?
- A.
A decrease in temperature
- B.
The addition of cholesterol
- C.
Hydrogen bonding of water holding the membrane together
- D.
Introduction of double bonds into fatty acids
- E.
An increase in temperature
Correct Answer
C. Hydrogen bonding of water holding the membrane togetherExplanation
Hydrogen bonding of water holding the membrane together does not influence membrane fluidity because it is a separate mechanism that helps stabilize the structure of the membrane. Membrane fluidity is primarily influenced by temperature, the addition of cholesterol, and the introduction of double bonds into fatty acids. A decrease in temperature decreases fluidity, while an increase in temperature increases fluidity. The addition of cholesterol helps regulate fluidity by reducing it at high temperatures and increasing it at low temperatures. The introduction of double bonds into fatty acids increases fluidity by creating kinks in the fatty acid chains.Rate this question:
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- 4.
A type of transport of a solute across a membrane, up its concentration gradient, using protein carriers driven by the expenditure of chemical energy is known as
- A.
Osmosis
- B.
Diffusion
- C.
Facilitated transport
- D.
Active transport
- E.
Exocytosis
Correct Answer
D. Active transportExplanation
Active transport is the correct answer because it involves the movement of solutes across a membrane against their concentration gradient, which requires the expenditure of energy. This energy is provided by ATP, a molecule that stores and releases chemical energy. Protein carriers are used in active transport to transport the solutes across the membrane. Osmosis is the movement of water molecules across a membrane, diffusion is the movement of solutes from an area of high concentration to an area of low concentration, facilitated transport is the movement of solutes across a membrane with the help of specific proteins, and exocytosis is the process of releasing molecules from a cell by fusion of vesicles with the cell membrane.Rate this question:
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- 5.
The cell's transactions with the environment mediated by its plasma membrane include all of the following except
- A.
Ingesting food as molecules and sometimes as entire cells
- B.
Returning waste and other molecules back to the environment
- C.
Responding to a host of chemical cues
- D.
Directing the synthesis of various food-digesting proteins
- E.
Passing of messages to other cells
Correct Answer
D. Directing the synthesis of various food-digesting proteinsExplanation
The cell's plasma membrane mediates its transactions with the environment, including ingesting food, returning waste, responding to chemical cues, and passing messages to other cells. However, directing the synthesis of various food-digesting proteins is not a transaction that is mediated by the plasma membrane. This process occurs within the cell's cytoplasm and is regulated by the cell's genetic material and intracellular machinery.Rate this question:
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- 6.
Which of the following properties is not true of membrane phospholipids?
- A.
The hydrophobic tails are oriented towards the interior.
- B.
The hydrophilic heads are oriented towards the exterior.
- C.
Only the saturated fatty acids are always present.
- D.
Once they are incorporated they remain in the membrane permanently.
- E.
The bilayers made up of them are randomly interspersed with proteins.
Correct Answer
C. Only the saturated fatty acids are always present.Explanation
The correct answer is "Only the saturated fatty acids are always present." This statement is not true because membrane phospholipids can contain both saturated and unsaturated fatty acids. Unsaturated fatty acids have double bonds in their carbon chains, which can introduce kinks and increase fluidity in the membrane. Therefore, the presence of unsaturated fatty acids in membrane phospholipids is essential for maintaining the fluidity and flexibility of the membrane.Rate this question:
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- 7.
The fluid nature of the membranes is attributed to a lateral movement of
- A.
Protein channels.
- B.
Phospholipid molecules.
- C.
Antigen molecules.
- D.
Pumps such as the proton pump.
- E.
The entire lipid bilayer.
Correct Answer
B. pHospHolipid molecules.Explanation
The fluid nature of the membranes is attributed to a lateral movement of phospholipid molecules. Phospholipids are the main components of cell membranes and they have a hydrophilic (water-loving) head and hydrophobic (water-repelling) tail. This structure allows them to form a bilayer, with the hydrophilic heads facing outward towards the aqueous environment and the hydrophobic tails facing inward. The phospholipid molecules can move laterally within the membrane, which gives the membrane its fluidity. This fluidity is important for various cellular processes, such as the movement of proteins and other molecules within the membrane.Rate this question:
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- 8.
On the outer surface of the plasma membrane there are marker molecules that identify the cell-type. Often these molecules are
- A.
ATP.
- B.
Amino acids.
- C.
Nucleotides.
- D.
Carbohydrate chains.
- E.
Inorganic ions.
Correct Answer
D. Carbohydrate chains.Explanation
Carbohydrate chains are marker molecules found on the outer surface of the plasma membrane that help identify the cell-type. These chains, also known as glycoproteins or glycolipids, are composed of sugar molecules attached to proteins or lipids. They play a crucial role in cell recognition and communication, allowing cells to interact with each other and with their environment. ATP, amino acids, nucleotides, and inorganic ions are important molecules in cellular processes, but they do not serve as marker molecules on the plasma membrane.Rate this question:
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- 9.
Which of the following protein classes are not found as membrane proteins?
- A.
Transport channels
- B.
Hormones
- C.
Receptors
- D.
Enzymes
- E.
Identify markers
Correct Answer
B. HormonesExplanation
Hormones are not found as membrane proteins because they are signaling molecules that are secreted by glands into the bloodstream to target distant cells. They travel through the bloodstream and bind to specific receptors on the surface of target cells, initiating a cellular response. Unlike membrane proteins, hormones are not directly embedded in the cell membrane but rather act as signaling molecules that interact with membrane proteins and initiate intracellular signaling pathways.Rate this question:
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- 10.
The following are all functions of a typical plasma membrane except
- A.
Transport of water and bulk material.
- B.
Selective transport of certain molecules and material.
- C.
Reception of information.
- D.
Expression of cellular identify.
- E.
Synthesis of DNA.
Correct Answer
E. Synthesis of DNA.Explanation
The plasma membrane is responsible for various functions in a cell, including selective transport of molecules, reception of information, and expression of cellular identity. However, synthesis of DNA is not a function of the plasma membrane. DNA synthesis occurs in the nucleus of the cell, where the DNA is replicated during cell division. The plasma membrane does not play a direct role in this process.Rate this question:
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- 11.
The movement of substances to regions of lower concentration is called
- A.
Active transport.
- B.
Diffusion.
- C.
Osmosis.
- D.
Pumping.
- E.
Exocytosis.
Correct Answer
B. Diffusion.Explanation
Diffusion is the movement of substances from regions of higher concentration to regions of lower concentration. It occurs passively, without the need for energy input. Active transport, on the other hand, requires energy to move substances against their concentration gradient. Osmosis is a specific type of diffusion that refers to the movement of water molecules across a selectively permeable membrane. Pumping and exocytosis are processes that involve the active movement of substances across cell membranes. Therefore, the correct answer is diffusion.Rate this question:
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- 12.
If two solutions have unequal concentrations of a solute, the solution with the lower concentration is called
- A.
Isotonic.
- B.
Hypertonic.
- C.
Hypotonic.
- D.
Hypnotic.
- E.
Osmosis.
Correct Answer
C. Hypotonic.Explanation
When two solutions have unequal concentrations of a solute, the solution with the lower concentration is called hypotonic. In a hypotonic solution, there is a higher concentration of water molecules outside the cell compared to inside the cell. This causes water to move into the cell through the process of osmosis, leading to cell swelling or bursting.Rate this question:
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- 13.
In bacteria, fungi, and plants the high internal pressure generated by osmosis is counteracted by the mechanical strength of their
- A.
Plasma membranes.
- B.
Organelles.
- C.
Cytoskeletons.
- D.
Cell walls.
- E.
Flagella.
Correct Answer
D. Cell walls.Explanation
In bacteria, fungi, and plants, the high internal pressure generated by osmosis is counteracted by the mechanical strength of their cell walls. The cell walls provide a rigid structure that prevents the cells from bursting under osmotic pressure. The cell walls act as a protective barrier and help maintain the shape and integrity of the cells. This is why cell walls are the correct answer in this context.Rate this question:
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- 14.
The actual transport of protons by the proton pump is mediated by a transmembrane protein which undergoes a change in its
- A.
Conformation.
- B.
Amino acid sequence.
- C.
Net charge.
- D.
Solubility.
- E.
Immunity.
Correct Answer
A. Conformation.Explanation
The correct answer is "conformation." The explanation for this is that the actual transport of protons by the proton pump is facilitated by a transmembrane protein. This protein undergoes a change in its conformation, or shape, which allows it to transport the protons across the membrane. The change in conformation is crucial for the protein's function as a proton pump, as it enables the protein to bind to and transport the protons effectively.Rate this question:
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- 15.
The process often thought of as "cell eating" is
- A.
Osmosis.
- B.
Pinocytosis.
- C.
Phangocytosis.
- D.
Diffusion.
- E.
Active transport.
Correct Answer
C. pHangocytosis. -
- 16.
Carrier-mediated transport is also called
- A.
Facilitated diffusion.
- B.
Active transport.
- C.
Exocytosis.
- D.
Endocytosis.
- E.
Phagocytosis.
Correct Answer
C. Exocytosis. -
- 17.
Osmosis can only occur if water travels through the
- A.
Cell wall.
- B.
Semi-permeable membrane.
- C.
Vacuole.
- D.
ER.
- E.
Cytoskeleton.
Correct Answer
B. Semi-permeable membrane.Explanation
Osmosis is the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration through a semi-permeable membrane. The semi-permeable membrane allows the passage of water molecules but restricts the movement of solute particles. Therefore, osmosis can only occur if water travels through the semi-permeable membrane. The other options mentioned, such as the cell wall, vacuole, ER, and cytoskeleton, are not directly involved in the process of osmosis.Rate this question:
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- 18.
The type of transport that is specific, which requires specific carrier molecules and energy is
- A.
Exocytosis.
- B.
Facilitated diffusion.
- C.
Active transport.
- D.
Endocytosis.
- E.
Osmosis.
Correct Answer
C. Active transport.Explanation
Active transport is the process of moving molecules or ions across a cell membrane against their concentration gradient, from an area of lower concentration to an area of higher concentration. This process requires the use of carrier molecules, such as proteins, to transport the molecules or ions across the membrane. Additionally, active transport also requires the input of energy in the form of ATP. Therefore, active transport is the type of transport that is specific, requires specific carrier molecules, and energy.Rate this question:
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- 19.
In a single sodium-potassium pump cycle, ATP is used up with the result that
- A.
3 sodium ions leave and 2 potassium ions enter.
- B.
1 sodium ion enters and 1 potassium ion leaves.
- C.
1 sodium ion leaves and 1 potassium ion enters.
- D.
3 sodium ions enter and 2 potassium ions leave.
- E.
Sodium and potassium ions enter and water leaves.
Correct Answer
A. 3 sodium ions leave and 2 potassium ions enter.Explanation
During a single sodium-potassium pump cycle, ATP is used up to transport 3 sodium ions out of the cell and 2 potassium ions into the cell. This pump is responsible for maintaining the concentration gradients of sodium and potassium across the cell membrane, as it moves sodium ions against their concentration gradient and potassium ions with their concentration gradient. This active transport process is essential for various cellular functions, including nerve impulse transmission and muscle contraction.Rate this question:
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- 20.
The accumulation of amino acids and sugars in animal cells occurs through
- A.
ATP pumps.
- B.
Sodium-potassium pumps.
- C.
Glucose pumps.
- D.
Coupled transport.
- E.
Proton pumps.
Correct Answer
D. Coupled transport.Explanation
Coupled transport refers to the process by which two or more substances are transported across a cell membrane simultaneously, using the energy from one substance moving down its concentration gradient to power the movement of another substance against its concentration gradient. In the case of the accumulation of amino acids and sugars in animal cells, coupled transport allows these molecules to be taken up against their concentration gradients, with the energy provided by the movement of ions such as sodium or hydrogen. This process is essential for the uptake of nutrients and maintaining cellular homeostasis.Rate this question:
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- 21.
Cholesterol functions in the plasma membrane to
- A.
Transport ions.
- B.
Serve as an energy molecule.
- C.
Maintain fluidity.
- D.
Mediate steroid action.
- E.
Maintain hypertension.
Correct Answer
C. Maintain fluidity.Explanation
Cholesterol is an important component of the plasma membrane and plays a crucial role in maintaining its fluidity. It helps to regulate the fluidity of the membrane by preventing it from becoming too rigid or too fluid. This is important for the proper functioning of the membrane, as it allows for the movement of molecules and ions across the membrane, as well as the interaction of proteins within the membrane. Cholesterol also helps to stabilize the membrane and protect it from damage. Therefore, the correct answer is maintain fluidity.Rate this question:
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- 22.
The Fluid Mosaic Model proposed by Singer and Nicolson in 1972 included that
- A.
The cell membrane was composed of lipids and proteins.
- B.
The cell membrane was composed of a phospholipid bilayer between two layers of globular proteins.
- C.
The cell membrane was composed of a phospholipid bilayer with globular proteins actually inserted into the bilayer.
- D.
The cell membrane was composed of a phospholipid bilayer but the polar ends of the phospholipid molecules were reversed.
Correct Answer
C. The cell membrane was composed of a pHospHolipid bilayer with globular proteins actually inserted into the bilayer.Explanation
The Fluid Mosaic Model proposed by Singer and Nicolson in 1972 suggested that the cell membrane is made up of a phospholipid bilayer with globular proteins embedded within the bilayer. This means that the proteins are not just attached to the surface of the membrane, but are actually inserted into the lipid bilayer. This model also implies that the membrane is fluid, allowing for movement of the lipids and proteins within it.Rate this question:
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- 23.
Membrane proteins serve many functions. One of the functions is transportation of substances across the membrane. If a cell biologist placed cells into an environment in which a chemical has been added that blocks the function of these transport proteins, which process will be blocked?
- A.
Active transport
- B.
Osmosis
- C.
Diffusion
- D.
Phagocytosis
- E.
Pinocytosis
Correct Answer
A. Active transportExplanation
If the function of transport proteins is blocked, the process that will be blocked is active transport. Active transport is the movement of substances across a cell membrane against their concentration gradient, requiring the use of energy. Since the chemical added blocks the function of transport proteins, it will prevent the active transport of substances across the membrane. Osmosis, diffusion, phagocytosis, and pinocytosis are not dependent on transport proteins and will not be affected by the chemical.Rate this question:
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- 24.
For the process of diffusion to occur, molecules must
- A.
Move from areas of high concentration to areas of lesser concentration until an equilibrium is reached.
- B.
Move from areas of low concentration to areas of higher concentration until an equilibrium is reached.
- C.
Remain stationary until their molecular motion allows for an equilibrium to be reached.
- D.
Move from areas of high concentration to areas of lesser concentration until facilitated transport can assist the molecular equilibrium.
- E.
Move from areas of high concentration to areas of lesser concentration until an equilibrium is reached by active transport.
Correct Answer
A. Move from areas of high concentration to areas of lesser concentration until an equilibrium is reached.Explanation
Diffusion is the process by which molecules move from areas of high concentration to areas of lower concentration until an equilibrium is reached. This occurs due to the random motion of molecules, where they move freely and collide with each other. As a result of these collisions, molecules tend to spread out and distribute evenly throughout a given space. This movement continues until the concentration of molecules becomes equal in all areas, which is known as equilibrium. Therefore, the correct answer is that molecules must move from areas of high concentration to areas of lesser concentration until an equilibrium is reached.Rate this question:
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- 25.
Facilitated diffusion is an important method for cells in obtaining necessary molecules and removing other ones. Requirements for facilitated diffusion include which of the following?
- A.
The carrier molecule must be specific to the molecule that is transported. The direction of movement is always with the concentration gradient, never against the gradient.
- B.
The carrier molecule is nonspecific to the molecule that is transported. The direction of movement is always with the concentration gradient, never against the gradient.
- C.
The carrier molecule is nonspecific to the molecule that is transported. The direction of movement is always against the concentration gradient, never with the gradient.
- D.
The carrier molecule must be specific to the molecule that is transported and an ATP molecule must be attached to the specific carrier. The direction of movement is always against the concentration gradient, never with the gradient.
Correct Answer
A. The carrier molecule must be specific to the molecule that is transported. The direction of movement is always with the concentration gradient, never against the gradient.Explanation
Facilitated diffusion is a process by which molecules move across a cell membrane with the help of specific carrier molecules. These carrier molecules are specific to the molecule being transported, meaning they can only bind to and transport a particular molecule. The direction of movement in facilitated diffusion is always with the concentration gradient, meaning molecules move from an area of higher concentration to an area of lower concentration. This is because the carrier molecules facilitate the movement of molecules down their concentration gradient, requiring no energy input.Rate this question:
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- 26.
Which of the following types of solutions to cause blood cell lysis (bursting)?
- A.
Hypertonic
- B.
Isotonic
- C.
Hypotonic
- D.
Osmotic
Correct Answer
C. HypotonicExplanation
A hypotonic solution has a lower solute concentration compared to the inside of the blood cells. When blood cells are placed in a hypotonic solution, water molecules move into the cells through osmosis. This causes the cells to swell and potentially burst, leading to blood cell lysis.Rate this question:
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- 27.
Which of the following is not a component of an animal cell membrane?
- A.
Phospholipids
- B.
Polynucleotides
- C.
Aquaporins
- D.
Glycolipids
- E.
Cholesterol
Correct Answer
C. AquaporinsExplanation
Aquaporins are not a component of an animal cell membrane. Aquaporins are specialized proteins that function as water channels, allowing for the movement of water molecules across cell membranes. While phospholipids, polynucleotides, glycolipids, and cholesterol are all components of the animal cell membrane, aquaporins are not.Rate this question:
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- 28.
As a scientist you perform an experiment in which you create an artificial cell with a selectively permeable membrane through which only water can pass. You put a 5M solution of glucose into the cell and you place that into a beaker of water. What observations do you expect to see?
- A.
Water moves out of the cell.
- B.
Glucose moves out of the cell.
- C.
No net change in cell weight.
- D.
Water moves into the cell.
- E.
Glucose moves into the cell.
Correct Answer
D. Water moves into the cell.Explanation
When a selectively permeable membrane is present, only water molecules can pass through it, while larger molecules like glucose cannot. In this case, the artificial cell contains a 5M solution of glucose, which means that the concentration of glucose inside the cell is higher than in the surrounding beaker of water. As a result, water molecules will move from an area of lower concentration (the beaker) to an area of higher concentration (the cell) through osmosis. Therefore, the observation that is expected to be seen is that water moves into the cell.Rate this question:
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- 29.
As a scientist you perform an experiment in which you create an artificial cell with a selectively permeable membrane through which only water can pass. You put a 5M solution of glucose into the cell and you place that into a beaker of 10M glucose. What observations do you expect to see?
- A.
Water moves out of the cell.
- B.
Glucose moves out of the cell.
- C.
No net change in cell weight.
- D.
Water moves into the cell.
- E.
Glucose moves into the cell.
Correct Answer
A. Water moves out of the cell.Explanation
In this experiment, the artificial cell has a selectively permeable membrane that only allows water to pass through. The concentration of glucose inside the cell is lower (5M) compared to the concentration outside the cell (10M). According to the principle of osmosis, water will move from an area of lower solute concentration (inside the cell) to an area of higher solute concentration (outside the cell) to equalize the solute concentrations. Therefore, water will move out of the cell, resulting in a decrease in cell weight.Rate this question:
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- 30.
Which of the following is not a part of the sodium-potassium pump?
- A.
Three sodium ions bind to the cytoplasmic side of the protein.
- B.
Three sodium ions are translocated out of the cell.
- C.
Phosphate facilitates potassium ion binding to transport protein.
- D.
Two potassium ions are transported into the cell.
- E.
ATP binds to the protein which becomes phosphorylated (ADP is released).
Correct Answer
C. pHospHate facilitates potassium ion binding to transport protein.Explanation
The sodium-potassium pump is a membrane protein responsible for maintaining the concentration of sodium and potassium ions inside and outside of the cell. It works by binding three sodium ions on the cytoplasmic side of the protein, which are then translocated out of the cell. Simultaneously, two potassium ions are transported into the cell. ATP binds to the protein, causing it to become phosphorylated and release ADP. The correct answer states that phosphate facilitates potassium ion binding to the transport protein, which is not a part of the sodium-potassium pump process.Rate this question:
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