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The molecular consequences of the hemoglobin S mutation are that:
the hemoglobin S forms aggregates and fibrous precipitates when oxygen is released
Fetal hemoglobin contains:
two alpha subunits and two gamma subunits
Hemoglobin S, the abnormal form of hemoglobin responsible for sickle cell anemia, is the result of a mutation in the gene for the β subunit. This mutation results in the change of:
Each chain of hemoglobin can be viewed as existing in one of two states—the R state and the T state. What is the relationship of these states to oxygen binding?
Oxygen binds with greater affinity to the T state, converting it into the R state.
The binding of oxygen to myoglobin and hemoglobin has what effect on the heme iron?
The binding of oxygen partially balances the "pull" by the histidine ligand causing the iron to move toward the plane of the porphyrin ring.
The Fe brings the His with it and causes a considerable shift in the conformation of the protein.
A hemoglobin molecule contains:
Hemoglobin is also involved in transporting carbon dioxide from the tissues to the lungs. How is this accomplished?
Carbon dioxide reacts with an amino group to stabilize the R state.
Carbon dioxide reacts with the N-terminal amino group
Which of the following statements best describes how (2,3-BPG) reduces hemoglobin's affinity for oxygen?
2,3-BPG binds to positively charged Lys and His residues in the center of the hemoglobin, stabilizing the T (low-affinity) state.
The 2,3-BPG is highly negatively charged and forms salt bridges with positively charged His and Lys in the central cavity of the hemoglobin molecule. It binds with high affinity to the deoxygenated state and thus stabilizes the T state. When oxygen binds, conformational changes reduce the size of this central cavity, essentially kicking out the 2,3-BPG.
In fetal hemoglobin (HbF), the two α subunits are replaced with two γ subunits, resulting in fetal hemoglobin having a higher affinity for oxygen than the mother's normal adult hemoglobin. This increased oxygen affinity of HbF is due to:
decreased binding of 2,3-BPG.
The decreased affinity for 2,3-BPG makes the binding of oxygen more favorable in HbF.
The process of digestion in the stomach is carried out in two main ways. One way involves the _____ environment that exists in the stomach.
Enzymes that are activated by specific proteolytic cleavage are called
Studies of venom components of the South African pit viper helped in the development of drugs to combat:
Cholecystokinin (CCK) is a family of peptide hormones released from the _____. Increased levels of CCK lead to a feeling of satiety.
Which of the following is a complex carbohydrate?
What do micelles and chylomicrons have in common?
Acyl groups generated during metabolic processes involving carbohydrates and fatty acids are activated by attachment to
· Coenzyme A.
· Acetyl-CoA is generated during the degradation of both carbohydrates and fatty acids.
Which of the following contributes to the high phosphoryl-transfer potential of ATP?
· a resonance stabilization
· charge repulsion
· the ability of water to interact more favorably with the products of ATP hydrolysis than with ATP itself
Controlling the catalytic activity of enzymes is important in regulation of metabolic pathways. Two ways in which this may be accomplished are
For a given reaction of A (substrate) being converted to B (product), how might this reaction in the cell still proceed from A to B even if the ΔGo is positive?
Deplete product B to facilitate more B production.
The hydrolysis of ATP drives metabolism by
shifting the equilibrium of the reaction.
The equilibrium constant of an unfavorable reaction can be shifted by coupling that reaction to the hydrolysis of ATP.
What material in vertebrate muscle serves as a reservoir for high-energy phosphate groups?
The energetics favor transfer of phosphate to creatine phosphate when ATP is present in large amounts and the reverse when ATP is needed.
In a metabolic pathway:
During catabolic processes, the oxidation of energy-rich molecules often results in the reduction of NAD+ to NADH. What comparable molecule is the most commonly used reductant for reductive steps in anabolic processes?
Which of the following describes an important difference between NADH and NADPH?
Why can it be accurately said that the fatty acid is the more efficient energy storage molecule?
The glucose is more oxidized
Metabolic reactions and processes that break down material and transform fuels into cellular energy are referred to as _____ and those performing energy requiring biosynthetic processes as _____.
If you proceed long enough through a series of aerobic catabolic cellular reactions, ultimately what must appear as one of the products?
The energy for the phosphorylation of ADP to ATP can come from molecules with a higher phosphoryl transfer potential or from
ion gradients across membranes
are ionized at physiological pH, usually referred to as their carboxylate form, rather than the unionized acid.
The common types of membrane lipids are:
Phospholipids are composed of four components:
The ether linkages and branching structure of membrane lipids of extremophiles prevent hydrolysis and oxidation of membranes in harsh environments.
Inappropriate farnesylation is a cause of Hutchinson-Gilford progeria syndrome, a disease of premature aging.
Failure to remove a farnesyl group from the nuclear protein lamin results in a deformed nuclear membrane and impaired nuclear function.
C-5 hydroxyl group attacks carbon atom C-1 of the aldehyde group
intramolecular hemiacetal, a six- carbon ring, is called a pyranose
can react with hemoglobin, forming glycosylated hemoglobin (hemoglobin A1c), which are fully functional.
Cartilage is composed of the proteoglycan aggrecan and cartilage. The glycosaminoglycan component of aggrecan cushions joints by releasing water on impact, and then rebinding water.
Chitin, a glycosaminoglycan found in the exoskeleton of insects, is one of the most abundant carbohydrates in the world.
Hemoglobin is an allosteric protein that displays cooperativity in oxygen binding and release.
Myoglobin binds oxygen in muscle cells -not cooperative.
Oxygen binding is measured as a function of the partial pressure of oxygen (pO2).
Hb - sigmoidal Myoglobin - hyperbolic
Enteropeptidase, secreted by intestinal cells, converts inactive trypsinogen into active trypsin. Trypsin activates the other proenzymes.
movement of food from the stomach to the intestine stimulates the secretion of
A thermodynamically unfavorable reaction in a pathway can be made to occur by coupling it to a more favorable reaction.
is exergonic because the triphosphate unit contains two phosphoanhydride bonds that are unstable.
―the standard free energy of hydrolysis―is a means of comparing the tendency of organic molecules to transfer a phosphoryl group to an acceptor molecule.
Once the creatine phosphate stores are depleted, ATP must be generated by metabolic pathways.
Coenzyme A (CoA or CoASH) is an activated carrier of acyl groups such as the acetyl group.
The transfer of the acyl group is exergonic because the thioester is unstable.
Thioesters can not be stabilized by resonance structures like oxygen esters.
The B vitamins function as coenzymes.
Vitamins A, C, D, E, and K play a variety of roles, but do not serve a coenzymes.
used to assess energy status: energy charge and phosphorylation potential.
converts one molecule of glucose to 2 molecules of pyruvate with the generation of 2 molecules of ATP.
A dehydration reaction, catalyzed by enolase, results in the production of phosphoenolpyruvate (PEP)
Phosphoenolpyruvate is a high phosphoryl-transfer compound because the presence of the phosphate, traps the compound in the unstable enol tautomer.
The conversion of glucose into two molecules of ethanol
The NADH generated by glyceraldehyde 3-phosphate dehydrogenase is oxidized by alcohol dehydrogenase, regenerating NAD+.
Excess consumption is linked to obesity, fatty liver, and the development of type 2 diabetes. Excess acetyl CoA is synthesized and converted to fats.
Galactose is converted into glucose 6-phosphate by the galactose-glucose conversion pathway, which begins with the phosphorylation of galactose by galactokinase.
Galactose+ATP → glucose 1-phosphate+ADP+H+
Glucose 1-phosphate can be converted into glucose 6-phosphate by phosphoglucomutase.
A high level of ATP inhibits the enzyme by decreasing its affinity for fructose 6-phosphate.
AMP diminishes the inhibitory effect of ATP.
Five glucose transporters, termed GLUT1-5, facilitate the movement of glucose across the cell membrane.
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