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Example Questions
Example Question #1 : Transport Proteins
How does an increase in carbon dioxide affect oxygen transport in hemoglobin?
Hemoglobin will have a lower oxygen affinity, which means that subunit cooperation will be lost
Hemoglobin will have a greater oxygen affinity, which allows for a greater release of oxygen into tissue
Hemoglobin will have greater oxygen affinity, which allows more oxygen to be carried
Hemoglobin will have a lower oxygen affinity, which allows for a greater release of oxygen into tissue
Hemoglobin will have a lower oxygen affinity, which allows for a greater release of oxygen into tissue
A high carbon dioxide concentration will decrease the pH and produce the Bohr effect. These conditions will cause a slight conformational change in hemoglobin that results in a lower oxygen binding affinity. However, since the partial pressure of oxygen in the lungs in so high, most of the available oxygen will be loaded on to the hemoglobin anyway. Since the oxygen affinity is lowered, the hemoglobin will release the oxygen more freely, resulting in a greater oxygen to load in tissue. Functioning hemoglobin always has four cooperative subunits.
Example Question #2 : Transport Proteins
Which of the following steps list in chronological order, the creation of a transport vesicle from a membrane via clathrin coating?
The clathrin coat is assembled, the membrane buds out, the vesicle forms, the clathrin coat is disassembled, dynamin pinches the vesicle
The clathrin coat is assembled, the membrane buds out, the vesicle forms, dynamin pinches the vesicle, the clathrin coat is disassembled
The vesicle forms, dynamin pinches the vesicle, the clathrin coat is assembled, the clathrin coat is disassembled, the membrane buds out
The membrane buds out, the clathrin coat is assembled, the vesicle forms, dynamin pinches the vesicle, the clathrin coat is disassembled
The membrane buds out, the vesicle forms, dynamin pinches the vesicle, the clathrin coat is assembled, the clathrin coat is disassembled
The clathrin coat is assembled, the membrane buds out, the vesicle forms, dynamin pinches the vesicle, the clathrin coat is disassembled
The process of creating transport vesicles via clathrin coats proceeds in distinct steps. Before any budding occurs of the membrane, clathrin attaches to it, bound to adaptin which is attached to a transmembranal cargo receptor. (Cargo molecules are what trigger the creation of the vesicle in the first place.) The clathrin coating is believed to cause the membrane to bud. After the vesicle forms, dynamin uses GTP to pinch the vesicle off, and it is only then that the clathrin coat disassembles and we have a transport vesicle.
Example Question #1 : Transport Proteins
Which of the following lists these molecules in order of increasing permeability to a lipid bilayer?
Glucose, carbon dioxide, water, sodium ion
Carbon dioxide, water, glucose, sodium ion
Glucose, carbon dioxide, sodium ion, water
Sodium ion, glucose, water, carbon dioxide
Sodium ion, glucose, carbon dioxide, water
Sodium ion, glucose, water, carbon dioxide
Charged molecules do not permeate the lipid bilayer easily at all. So despite its small size, among our choices, a sodium ion passes least easily through. Polar molecules also have a hard (but less difficult) time passing through, and the larger the molecule, the harder that becomes, so after the sodium ion comes glucose, followed by water, which is polar but much smaller. Small, hydrophobic molecules -- such as carbon dioxide -- diffuse through most easily, because they can pass through the longest (hydrophobic) part of the membrane.
Example Question #1 : Transport Proteins
Which type of transport does not require a protein?
Osmosis
Passive transport
Active transport
Facilitated diffusion
Osmosis
There are two types of transport: passive transport and active transport. Active transport requires an expenditure of energy and a protein pump. Passive transport includes simple diffusion and facilitated diffusion. Diffusion is the movement of a substance from an area of high concentration to one of low concentration. Simple diffusion is the name for the diffusion process which does not require a protein; facilitated diffusion is the name for the diffusion process which requires a carrier protein for transport. Osmosis is the simple diffusion of water and thus does not require protein.
Example Question #41 : Biochemistry
Which of the following amino acids coordinates the heme ring in hemoglobin?
Arginine
Glycine
Histidine
Phenylalanine
Lysine
Histidine
In hemoglobin, the nitrogen group on the amino acid Histidine coordinates the heme ring in hemoglobin by binding to an iron atom located in the middle of the heme ring.
Example Question #1 : Transport Proteins
A nonspecific hexagonal structure that functions to allow movement of molecules between adjacent cells is termed a(n) __________.
tight junction
transport protein
desmosome
integrin
gap junction
gap junction
A gap junction is a hexagonal protein that openly connects two adjacent cells. It is nonspecific, meaning it allows various different molecules and ions to travel through it. This type of transport is important for rapid communication between adjacent cells. For instance, gap junctions serve an important function in the heart - allowing the many cells present there to act as a functional syncytium. Integrins and tight junctions do not allow the passage of molecules between adjacent cells.
Example Question #3 : Transport Proteins
GLUT (glucose transporters) proteins transport glucose from the blood to cells. Which of the following statements about them are true?
I. GLUT proteins are integral membrane proteins.
II . GLUT proteins have their amino and carboxyl termini on the extracellular side of the plasma membrane.
III. Binding of glucose to the transporter protein leads to a conformation change and the transport of glucose to the inner side of the membrane.
IV. GLUT-1, GLUT-3, and GLUT-4 proteins are ubiquitous; GLUT-2 is found in the liver, pancreas and kidney.
II, III, and IV
I and II
I, II, and III
II and III
I, III, and IV
I, III, and IV
GLUT are integral membrane proteins.The proteins cross the membrane having the amino and carboxyl termini on the cytoplasmic side of the plasma membrane. Binding of glucose to the transporter leads to a conformational change, transport of glucose to the other side of the membrane. GLUT-1, GLUT -3 and GLUT-4 are present in most tissues; GLUT-2 is found in the liver, pancreas and kidney.
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