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WGU Biochemistry prep for test
Terms in this set (100)
DNA replication is ___________, which allows each of the two strands to serve as a _______ for the new strands.
b. semiconservative, template
DNA replication is semiconservative, meaning that each new duplex has one original (parent) strand and one new strand. Because the two parent strands are separated during replication and the base pairing is predictable, each parent strand can serve as a template for the new strand synthesis.
Which of the following enzymes does NOT assist the DNA polymerase on the lagging strand to overcome its two problems? (Recall that the DNA polymerase can only make DNA in the 5'->3' direction, and it must bind a double-stranded nucleotide polymer before it can start making its own DNA polymer.)
Helicase unwinds the double stranded DNA to allow for replication, but this is not a problem for the DNA polymerase.
Several components of cigarette smoke, including benzopyrene, insert themselves (intercalate) into the DNA and lead to several types of mutations such as frameshift mutations, including both insertions and deletion. Which of the following repair pathways would be used to repair this type of damage?
c. Nucleotide Excision Repair
Nucleotide excision repair is used to repair deletions, insertions, and helix-distorting lesions, such as thymine dimers.
Maternal smoking during pregnancy is hazardous yet common in many places. Many studies have associated prenatal smoking to unhealthy physical and psychological outcomes for the baby. Researchers know that maternal smoking affects are epigenetic in nature. Which of the following events can be considered epigenetic in nature?
a. Changes in chromatin structure
Frame shift mutations are a kind of mutations which result from addition of deletion of a nucleotide base resulting in an altered reading frame and ultimately a different protein, than the one the gene originally encoded. Frameshift mutations are genetic changes because they alter the DNA sequence, whereas epigenetic changes do not alter the DNA sequence. Epigenetic changes are modifications to genomic structure (not sequence) that are caused by the external environment. These environmental factors affect the overall chromatin structure to allow more or less "access" to the DNA by gene expression machinery to turn the genes "on" or "off". In other words, epigenetics can alter gene expression without changing the underlying DNA sequences. The changes may or may not be heritable, depending on the location and circumstances.
Blood type is an example of what type of inheritance?
The genes that produce the A and B antigen proteins can both be expressed independently, and a heterozygote (someone with both genes) will be produce both A and B proteins - neither will dominate the other. The is an example of codominance.
What is the expected probability that a child will have an autosomal dominant disease if their father is heterozygous for the allele and their mother is homozygous for the normal allele?
If D is the disease-conferring dominant allele and d is the normal allele, the father has the genotype Dd and the mother's genotype is dd. Each child can only inherit a d allele from their mother, and they have a 50% chance of inheriting the D allele from their father. As a result, the expected probability that their child will inherit the disease is 50%.
The physical trait of lip protrusion exhibits a characteristic type of inheritance, as shown by the pedigree above. What type of inheritance best describes this inheritance pattern?
a. Incomplete dominance
The correct answer is incomplete dominance. The blending of the large and small lip protrusion into an intermediate, medium lip protrusion, as well as the presence of all three variations in the offspring, demonstrate a clear example of incomplete dominance.
The normal sequence of a section of the HLA-B27 gene, a genetic marker of the inflammatory disease Ankylosing spondylitis, is given below. Match each mutation of the sequence to the type of mutation it exhibits. A genetic code table is provided for your use in answering the question.
5'- CGG CAG AAU UUA -3'
5'- CAG CAG AAU UUA -3' - Missense mutation
5'- CGG CAG AAA UUU A-3' - Insertion
5'- CGG CAG AAC UUA -3' - Silent mutation
5'- CGG CAG AAU UA -3' - Deletion
5'- CGG UAG AAU UUA-3' - Nonsense mutation
Silent mutations are those in which the amino acid encoded doesn't change as a result of the mutation.
Missense mutations are those in which the amino acid encoded changes to a different amino acid as a result of the mutation.
Nonsense mutations are those in which the amino acid encoded changes to a stop codon as a result of the mutation, yielding a smaller protein.
Insertions are the inclusion of extra nucleotides compared to the original sequence. They can result in other mutations, such as nonsense mutations.
Deletions are the removal of nucleotides compared to the original sequence. They can result in other mutations, such as nonsense mutations.
PCR is a powerful tool that can do all of the following....
b. detect mutations that lead to disease
c. copy small segments of DNA, less than 6kb
d. amplify DNA from samples that have just a few cells
PCR's ability to amplify is powerful, and products can even be generated from samples with just a few cells. PCR is less reliable for amplifying large segments of DNA greater than 6 kb, though some careful changes to the techniques can allow it.
Which of the following is a required "ingredient" in a PCR
a. DNA nucleotides
b. DNA primers
c. DNA polymerase
The primers used in PCR are made from DNA, rather than RNA. RNA primers are used in DNA replication inside the cell, but the quick degradation of RNA makes it less useful for PCR reactions. Instead, PCR reactions contain primers made of DNA to anneal to the region of DNA that will be amplified and serve as a starting point for DNA polymerase.
Which of the following changes can be detected using PCR?
a. Differences in DNA sequence
Differences in DNA sequence can be detected since these changes can alter the ability of primers to anneal to the DNA. They can also be detected by DNA sequencing of the PCR product. Epigenetic changes are not detectable via PCR because they don't affect the DNA sequence.
A small segment of Kevin's green opsin gene is shown below. What would be the resulting mRNA sequence?
Kevin's opsin gene at nucleotide positions 936 to 941.
5'-G.C.C.T.A.G-3' (coding strand)
3'-C.G.G.A.T.C-5' (template strand)
This sequence is the same as the coding sequence, and the "T" bases have been replaced with "U", as is found in RNA.
The gene for blue opsin protein is located on chromosome 7, a non-sex chromosome. What kind of inheritance pattern would you expect to see with color blindness due to a mutated blue opsin?
a. An equal distribution of blue color blindness between males and females.
The blue opsin gene is located on a somatic (non-sex) chromosome, and therefore will be inherited with the same frequency for both sexes.
In Kevin's case, a specific kind of mutation in the opsin gene resulted in the premature termination of the translation process. This resulted in a shorter opsin protein than usual. What specific mutation could have caused this?
c. Nonsense mutations
Missense mutations are point mutations that change a single base pair in a codon such that the codon now encodes a different amino acid. In Kevin's case, a nonsense mutation, which is a point mutation that changes a single base pair in a codon to a stop codon resulted in termination of the translation signal. This further led to the synthesis of truncated protein.
After consultation with a genetic counselor and an examination of extended family history, the following pedigree was generated. Who did Kevin most likely inherit this mutation from?
a. Maternal grandfather
Red-green color blindness occurs more frequently in males than females because these genes are located on the X chromosome, and males inherit only one X chromosome and will express whatever alleles are on that chromosome. Females, on the other hand, inherit two X chromosomes, and thus have two alleles for each gene. If one of the alleles is mutated on one X chromosome, there is usually a correct allele on the other that can provide the needed gene. A woman must have two mutated opsin alleles to be color blind, while men need only one. This is known as sex-linked inheritance. Kevin inherited his Y chromosome from his father and his X chromosome from his mother, so his X chromosome with the defective opsin gene most likely came from his maternal grandfather and was passed to him by his mother. Thus, both grandfathers is not correct because his paternal grandfather would have contributed a Y chromosome.
The nonsense mutation that causes Kevin's color blindness could have resulted from a malfunction of __________.
b. DNA polymerase
Helicase unwinds the DNA during replication, but doesn't add or remove nucleotides. The correct choice is the DNA polymerase. DNA polymerase could have added an erroneous nucleotide, and it's proofreading activity could have missed it. While this type of event is rare, DNA polymerase is known to make a mistake that it doesn't correct about one in one hundred million!
Primary structure consists of the order of ______ in a protein. These are held together with ______ bonds that are formed by a ______ reaction.
a. Amino acids, peptide, dehydration
Several types of side chain interactions stabilize the tertiary structure of proteins, including which of the following?
c. Ion pairs, hydrophobic interactions, hydrogen bonds, disulfide bonds
The stability of a tertiary structure of a protein depends on the various interactions and bonds that occur between the side chains of different amino acids.
Which of the following statements is true about the secondary structure of proteins?
a. It includes alpha helices as a common form.
c. It includes beta pleated sheets as a common form.
d. It involves hydrogen bonding between the backbone atoms.
A secondary structure of protein consists of hydrogen bonds between backbone atoms, includes alpha helices and beta sheets as common forms.
In order to fulfill their function, proteins must fold in proper, three-dimensional conformations. Which one of the following molecules, available in a cell, is likely to help a protein fold properly?
Chaperones are helper proteins that ensure proper protein folding by stabilizing the polypeptide until the correct structure is fully formed.
Which of the following is true about a misfolded protein?
a. It can be degraded by the cell.
b. It can cause protein aggregation.
d. It can be the result of denaturation.
e. It will lose its normal function.
Misfolded proteins can be the result of denaturation, are usually degraded by the cell into amino acids, lose their normal function, and may even lead to detrimental protein aggregation, as in the case of Alzheimer's disease.
Which of the following amino acids would you expect to find in the interior of a protein most often?
Hydrophobic amino acids want to avoid water, and are most often found in the hydrophobic interior of the protein. While charged and polar amino acids can be found in the interior of the protein, they are also commonly found on the exterior of the protein where they can interact with water.
Which of the following amino acids would you expect to find most often on the exterior surface of a protein?
Aspartic acid is a charged amino acid that interacts well with water and is often found on the exterior surface of a protein.
Which part(s) of the amino acid below can be involved in peptide bond formation?
b. A - Amino group
Peptide bonds are formed between the amino group (A) and carboxylic acid group (B) of amino acids.
Which part(s) of the amino acid below contributes to tertiary structure stabilization?
c. D - R group
The backbone carboxylic acid is involved in peptide bond formation and primary structure. Tertiary structure is stabilized primarily by interactions between different R groups.
Drag the name of the protein structure level to the part of the amino acid that primarily contributes to that structure level.
Correct! The backbone of the amino acid participates primarily in primary and secondary structure while the R group stabilizes tertiary and quaternary structure.
In the pathway above, which compound could accumulate and trigger feedback inhibition?
c. End Product
The substrate is the start of the pathway, and therefore cannot inhibit anything before itself. While the amount of substrate could be reduced, and thereby slow product formation, the substrate itself is not part of feedback inhibition.
In order to regular the amount of a product from a pathway, cells often use feedback inhibition. When the end product is no longer needed (or needed at a reduced rate), the product begins to accumulate and bind to enzymes in the pathway. This binding can inhibit the action of that enzyme by noncompetitive inhibition, thus slowing the pathway and reducing the amount of product made.
A substrate binds to an enzyme at a specific site, referred to as a(n)_________________.
b. Active site
The active site of an enzyme is the site where the substrate specifically binds to the enzyme and the reaction is carried out.
You are in charge of designing a drug that inhibits the activity of a specific enzyme. An important criteria for the drug selection is to ensure that the drug is directly in competition with the original substrate when binding to the active site of the enzyme. Which of the following kind of inhibitor would be an ideal choice?
a. Competitive inhibitor
A competitive inhibitor competes with the substrate for access to enzyme's active site and inhibits the enzyme.
Which of the following factors can affect the protein folding and activity of an enzyme?
d. Reducing agents
Several factors can denature a protein and affect enzyme activity, including: reducing agents, pH, heat, and salt concentration.
One way a cell can avoid overproduction of a molecule is by using a particular type of inhibition in which the molecule itself acts as an inhibitor for an enzyme in its production pathway. This type regulation is known as ___________ inhibition.
The purpose of feedback inhibition in a cell is to prevent overproduction of the product. Feedback inhibition works by inhibiting an enzyme using the product of the very same reaction the enzyme catalyzes or a product from the same enzymatic pathway.
In the pathway above, what will happen to the levels of Second Intermediate Substrate if Enzyme 1 is inhibited as a result of feedback inhibition?
Inhibition of an enzyme earlier in the pathway will prevent the product(s) of that enzyme from forming, thereby preventing the action of subsequent enzymes and formation of their respective products. For example, inhibition of Enzyme 1 would lead to a decrease in First Intermediate Substrate, which then reduces the levels of Second Intermediate Substrate because Enzyme 2 has less substrate on which to act. Thus, the levels of Second Intermediate Substrate will decrease as a result of feedback inhibition.
What type of enzyme adds a phosphate to another molecule?
Protease enzymes break peptide bonds to digest proteins. Kinases add phosphates to molecules while phosphatases remove them.
Kinases are enzymes that use a phosphate donor, usually ATP, to add a phosphate to another molecule. Phosphatases have the opposite role - they remove phosphate groups from molecules.
Which of the following are possible effect(s) that phosphorylation/dephosphorylation can have on the activity of an enzyme?
b. Turn the enzyme "off".
c. Turn the enzyme "on".
Some enzymes are activated by phosphorylation while others are deactivated by the addition of a phosphate.
Adding or removing a phosphate group to an enzyme affects the activity, and the type of effect is specific to the enzyme. For some enzymes, phosphorylation activates the activity of the enzyme, while other enzymes can be deactivated by phosphorylation.
In the enzymatic cycle, the enzyme shape is changed when [Substrate binds] and resumes its original shape when [Product is released] after [Substrate is converted to product].
An enzyme is a catalyst, meaning that it can catalyze the same reaction over and over again. Substrate binding can alter the conformation (or shape) of an enzyme, so it must resume its original shape when product is released, after substrate is converted to product, to allow it to perform the same reaction again.
The rate of an enzyme reaction can be increased by which of the following:
b. Decreasing the activation energy of the reaction
Enzymes do not directly affect the temperature of a cell.
The rate (or speed) of a chemical reaction depends on the size of the activation energy barrier. Increasing temperature can provide the energy needed to get over the activation barrier, while lowering the temperature will reduce the available energy to overcome the barrier. However, enzymes cannot affect the temperature around them. Instead, enzymes decrease the activation energy of a reaction, thus allowing more reactions to take place at any given temperature.
Statins are a class of medications that target the enzyme HMG-CoA reductase in the pathway for cholesterol synthesis, as shown below.
Compared to a patient that is not on a statin medication, In a patient taking a statin medication the concentration of cholesterol would [decrease], the concentration of HMG-CoA would [increase], and the concentration of Acetoacetyl CoA would [stay the same].
Recall that inhibiting an enzyme generally leads to an increased concentration of the substrate of the inhibited enzyme and a decrease in its product (or products further down the pathway).
Deedra's dad has Alzheimer's Disease (AD) which is caused by a change in ______ structure.
AD is a manifestation of neuronal death and damage caused by malformed protein structures.
Proteins are crucial molecules with various functions in the cells. The structure of a protein directly impacts its function. Deedra's father has Alzheimers which is caused by a disturbance in the protein structure of at least two proteins, amyloid beta and tau.
Alzheimer's disease is caused by aggregation of the Amyloid beta peptide and tangle formation by the tau protein. What kinds of amino acids are likely to drive the formation of these protein aggregates?
Hydrophobic amino acids strive to avoid water and like to interact with other hydrophobic amino acids. Generally they are found in the interior of a protein. But, when there are too many misformed peptides with exposed hydrophobic surfaces, they tend to attract each other and result in protein aggregation.
Below is a schematic showing the synthesis and degradation of acetylcholine, an important neurotransmitter. If you were to design a drug to keep the acetylcholine concentration high, where would you target a drug inhibitor?
Acetylcholine is the substrate of the reaction and the desired chemical to preserve. However, since acetylcholine does not control its own production, it is ideal to target enzymes that can impact its concentration. Enzymes that produce acetycholine could be targeted for increased production, but this type of regulation is difficult to achieve with a drug. Instead, drugs usually inhibit specific enzymes.
Acetylcholinesterase is the enzyme which digests acetylcholine to acetate and choline. Acetylcholinesterase inhibition will decrease degradation of the acetylcholine, which will therefore increase the concentration of acetylcholine. Supplementation with excess acetate or choline may also help increase choline acetyltransferase activity and perhaps increase acetylcholine concentrations, but the only productive target for a drug inhibitor in this scheme is acetylcholinesterase.
After learning about Alzheimer's disease and one of the drugs used in its treatment, what other drug design strategies could you use to offer a treatment for AD?
a. Drugs that block the production of amyloid beta peptide
b. Drugs that break up the amyloid plaques
d. Drugs that inhibit the aggregation of protein structures
The more we are able to understand the molecular details of a disease and the enzymes involved in the disease pathway, the more opportunities one has to target the key molecules. Any of the options here could be a possible treatment in the case of AD.
Hemoglobin's cooperative binding behavior is key to its physiological function. The binding of which of the following molecules influences this behavior?
Binding of the first oxygen molecule to a hemoglobin subunit greatly enhances binding of the remaining oxygen molecules. All subunits communicate with each other and work in a unified fashion. This property is referred to as cooperativity.
Carbonic anhydrase is an important __________ present in the red blood cells that aids in efficient transportation of carbon dioxide in the form of _________, from tissues to lungs.
b. enzyme, bicarbonate ions
Carbonic anhydrase is an enzyme which catalyzes the conversion of carbon dioxide to bicarbonate ions. However, it does not transport carbon dioxide as is, but rather transports carbon dioxide by converting it to bicarbonate ions. This mechanism enables efficient transport of carbon dioxide by warding off bubble formation in the blood.
Hemoglobin's ability to bind or release oxygen depends on the pH of the environment. This behavior is known as the Bohr effect. Considering this, which of the following statements is true?
a. Hemoglobin binds to the oxygen at high pH and releases oxygen at low pH.
pH is a measure of H+ ion concentration. High pH indicates a more basic environment in which the H+ ion concentration is low, as seen in the lungs. Under these conditions, hemoglobin binds more oxygen. Low pH indicates an acidic environment in which the H+ ion concentration is high. Such conditions encourage the binding of H+ ions to hemoglobin and stabilizing a form of hemoglobin which decreases the affinity for oxygen, resulting in release of oxygen.
Hemoglobin acts as a buffer and controls the pH of the blood by binding to __________.
d. H+ ions.
H+ ions contribute to the acidity of blood. By binding to these ions, hemoglobin is able to act as a buffer and maintain the pH at an appropriate range.
In the lungs, the CO2 concentration is [low] and the pH is [high], while in the tissues, the CO2 concentration is [high] and the pH is [low].
In the lungs, CO2 concentration are low, resulting in decreased carbonic acid and higher pH. This creates a more basic (or alkaline) environment that promotes oxygen binding.In the tissues, CO2 concentration tends to be high, resulting in increased carbonic acid which lowers the pH. This creates an acidic environment that promotes oxygen release.
In locations where the pH is low, hemoglobin will be in the [T] state, allowing it to [release] oxygen more effectively.
At low pH, hemoglobin will be in the T, or tense, state to allow it to release oxygen more effectively to oxygen-starved tissues.
Increased levels of 2,3-BPG will [decrease] the affinity for oxygen by binding to and stabilizing the [T] state of hemoglobin. The action of 2,3-BPG allows hemoglobin to [release] oxygen more effectively, which is similar to the effect of [low] pH on the action of hemoglobin.
Increased levels of 2,3-BPG will Incorrect the affinity for oxygen by binding to and stabilizing the Correct state of hemoglobin. The action of 2,3-BPG allows hemoglobin to Incorrect oxygen more effectively, which is similar to the effect of Correct pH on the action of hemoglobin.
In comparison to adult hemoglobin, fetal hemoglobin has a [higher] affinity for oxygen because it [doesn't bind] 2,3-BPG well.
Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin because its structure does not bind 2,3-BPG well. As a result, the T state of fetal hemoglobin is not stabilized and it remains more readily in the R state, ready to bind oxygen even at lower concentrations.
Structurally, hemoglobin can bind ___ molecules of oxygen, all of which could potentially be replaced by carbon monoxide.
Hemoglobin has four subunits, all of which contain heme prosthetic groups. Each heme can bind an iron atom, and each iron atom can bind an oxygen molecule resulting in the binding of a total of four oxygen molecules. All four oxygen molecules can be potentially replaced by carbon monoxide.
Carbon monoxide outcompetes oxygen for attachment to the __________ group of hemoglobin where it is permanently, covalently attached.
Carbon monoxide has a higher binding affinity than oxygen to the heme group of hemoglobin. Such binding is irreversible.
As carbon monoxide binds to hemoglobin, the protein subunits change conformation to allow carbon monoxide to bind faster. This process is called __________.
d. positive cooperativity
Carbon monoxide does competitively inhibit the overall function of the hemoglobin protein.
Note that the question is referring to how the binding of one carbon monoxide molecule influences the conformation of the other subunits and increases the overall binding affinity for the hemoglobin molecule. Such a cooperative behavior exhibited by the subunits is referred to as positive cooperativity.
Carbon monoxide shifts the Oxygen-Hemoglobin Dissociation Curve to the left, while carbon dioxide shifts this curve to the right. Based on your knowledge of the Bohr Effect, which of the following statements is true?
b. Carbon dioxide decreases hemoglobin's affinity for oxygen, while carbon monoxide increases it
Carbon dioxide, released by the respiring cells, combines with the water molecules of plasma to form carbonic acid. Carbonic acid increases the H+ ion concentration (low or acidic pH). H+ ions stabilize the deoxy-conformation (T state) of hemoglobin and allow oxygen release and delivery to the tissues. On the other hand, carbon monoxide, which has a very high affinity for hemoglobin than oxygen, binds and maintains hemoglobin in oxy-conformation (R state). Oxy-conformation of HB is amenable to further binding of carbon monoxide and shifts the Oxygen-Hemoglobin Dissociation Curve to the left.
Glucose is a monosaccharide. It can be used as the raw material to build which one of the following molecules?
Glycogen is a polysaccharide made up glucose units.
Glycolysis is the conversion of glucose to pyruvate. Is this a catabolic process or an anabolic process?
Anabolic pathways refer to the synthesis of larger molecules from smaller ones, and they often require energy input from ATP.
Catabolic pathways refer to the breakdown of larger molecules into smaller ones and often produce ATP as a result. Glycolysis is a catabolic process. During glycolysis, a molecule of glucose is broken down into two molecules of pyruvate and two molecules of ATP are made in the process.
Which of the following is an accurate statement about glycolysis?
d. The final products of glycolysis are two molecules of pyruvate.
Glycolysis final products are two molecules of pyruvate.
Glucose is not the only food source that can make acetyl Co-A.
Various sources such as amino acids and fatty acids, in addition to glucose, can be catabolized to produce acetyl Co-A.
In the presence of oxygen, the end products of glycolysis have the potential to enter which one of the following pathways?
c. Citric acid cycle
In the presence of oxygen, pyruvate forms acetyl Co-A and enters the citric acid cycle, while fermentation occurs in the absence of oxygen.
In human cells, glycolysis takes place in the cytoplasm. The products of the glycolysis will enter the _________________ to continue with aerobic respiration.
The products of glycolysis enter the mitochondria to continue with aerobic respiration.
NADH and FADH2 are two cofactors made in the citric acid cycle. They then donate the ______________________ they gained in the citric acid cycle to the electron transport chain.
NADH and FADH2 donate electrons to the electron transport chain.
Aerobic respiration requires oxygen. Oxygen has a role in which of the following pathways:
b. Electron transport chain
Gluconeogenesis is building of new glucose molecules and is not involved in aerobic respiration.
Oxygen has a role as the terminal electron acceptor in the electron transport chain.
During periods of strenuous exercise the muscle cells can become anaerobic. Without oxygen, the electron transport chain cannot continue and the citric acid cycle slows down. In such situations, how do cells make ATP?
a. Pyruvate is transformed to lactate.
In the absence of oxygen, pyruvate is reduced to form lactic acid by fermentation.
The citric acid cycle could be inhibited by high concentrations of [NADH] due to feedback inhibition.
The citric acid cycle produces large amounts of NADH. If NADH is already abundant in the cell, the enzymes of the citric acid cycle that produce NADH will be inhibited by this product and slow the cycle.
Cyanide binds to complex IV of the electron transport chain, preventing electron transport. Which of the following would be the most immediate effect(s) of cyanide consumption
a. Oxygen would not be consumed by the ETC.
b. ADP will build up
c. Protons will not be pumped to the intermembrane space
Cyanide binds to the last complex of the electron transport chain, complex IV, which usually transfers electrongs to oxygen to create water and keep the flow of electrons going. By blocking complex IV, oxygen will not be consumed, which will prevent electron transport. As a result, NADH cannot be consumed by the ETC and will build up, and protons cannot be pumped into the intermembrane space of the mitrochondria. As a result, ATP production by ATP synthase will slow.
In an exercising muscle cell under anaerobic conditions, Incorrect from glycolysis is turned into --- in order to regenerate --- for further rounds of glycolysis, which produces --- ATP per round for the muscle cell to use. The Cori cycle allows --- to be turned into --- via gluconeogenesis in the liver at the expense of --- ATP. This means that, overall, the Cori cycle creates a deficit of ---ATP.
In an exercising muscle cell under anaerobic conditions, [pyruvate] from glycolysis is turned into [lactate] in order to regenerate [NAD+] for further rounds of glycolysis, which produces  ATP per round for the muscle cell to use. The Cori cycle allows [lactate] to be turned into [glucose] via gluconeogenesis in the liver at the expense of  ATP. This means that, overall, the Cori cycle creates a deficit of  ATP.
Which one of the following non-carbohydrate molecules has the potential to make a glucose molecule?
a. Amino acids
Some kinds of amino acids can create sugar molecules by the process of gluconeogenesis.
Carbohydrate loading is a common practice among endurance athletes. Often, three days before a big endurance event, they are known to eat large amounts of complex carbohydrates which leads to the storage of glycogen in their muscles. The stored glycogen increases their endurance by providing a steady supply of glucose during the event by the process of _______________.
Glycogenolysis is the breakdown of glycogen to release glucose. A further breakdown of glucose results in ATP production which helps with the prolonged physical activity in the athletes.
Insulin controls both carbohydrate and fat metabolism. Which of the following statements describes the effects of insulin?
a. Stimulates fatty acid production and storage
c. Stimulates the glucose uptake
d. Inhibits the glycogen breakdown
Insulin is responsible for several controls such as stimulating glucose uptake, inhibiting the glycogen breakdown and stimulating fat storage molecule synthesis.
True or False: The defining characteristic of diabetes is the lack of sufficient insulin production.
Not all cases of diabetes are due to a lack of insulin production. Diabetes could result from cells resistance to the insulin.
The complications of diabetes result from the accumulation of which of the following:
b. Advanced Glycation End-products (AGEs)
Glycogen is the glucose storage molecule. As such, it does not directly cause any complications in the diabetic patients.
Increased glucose levels will result in glycation of proteins, which will affect the function of a protein by making it more stiff and inflexible. Glycation can also lead to additional reactions that crosslink proteins together into advanced glycation end-products (AGEs), which can impair the function of the proteins and their associated organs.
The pancreas can regulate and maintain glucose homeostasis by secreting different hormones in response to varying blood glucose levels. The pancreas secretes insulin in response to high blood glucose levels, whereas ______________ is secreted in response to ________________ glucose levels.
b. glucagon, low
Yes, insulin is secreted by the pancreas in response to high glucose concentrations. But insulin is already listed for the subject. The other hormone secreted by the pancreas in response to glucose levels is the hormone glucagon.
While treatment with Metformin is beneficial for many individuals with type 2 diabetes, it does increase the risk of lactic acidosis (accumulation of lactate in the blood that results in lower blood pH) in those who take it. What effect of metformin directly contributes to this potential risk?
a. Decreased gluconeogenesis in the liver
Reduction in liver gluconeogenesis can help lower blood glucose levels in type 2 diabetics. However, it is not without some risk. Recall from the section on the Cori cycle that gluconeogenesis is essential for the conversion of lactate back to glucose after anaerobic fermentation in muscle and red blood cells. Treatment with metformin can, therefore, increase the risk of elevated lactate levels in the blood, a condition known as lactic acidosis because it lowers the blood pH.
A risk factor associated with the use of metformin in the treatment of diabetes is lactic acidosis. Acidosis is associated with [a decrease] in blood pH, due to [an increase] in the concentration of hydrogen ions (H+). Given this change in blood pH, hemoglobin is more likely to [release] oxygen.
Acidosis is associated with a decrease in blood pH, due to an increase in the concentration of hydrogen ions (H+). Given this change in blood pH, hemoglobin is more likely to release oxygen.
Which one of the following could result in better outcomes for type 2 diabetics?
c. An increased number of GluT4 transporters in the cell membrane
Gluconeogenesis is creation of more glucose and increasing the rate of gluconeogenesis will raise blood glucose and worsen the symptoms. Type 2 diabetes is often a result of decreased glucose uptake by the target cells. Increasing the translocation of GluT4 transporters can help lower blood sugar by allowing more glucose into the target cells.
Emma was prescribed metformin which is used to control blood glucose levels. One direct effect of metformin is inhibition of the ------------------------- pathway in the liver.
Metformin is a drug of choice for treating Type 2 diabetes. One of the direct actions of the drug in controlling the blood sugar levels is by inhibiting gluconeogenesis in the liver.
Emma has an A1C level of 7.0% in her blood. A1C is a form of__________________.
In the presence of excessive amounts of glucose in the blood, glucose makes a covalent bond to the hemoglobin protein in a reaction known as glycation. A1C is the glycated form of hemoglobin.
Myoglobin and hemoglobin each have different numbers of subunits and this affects their respective oxygen storage and delivery capabilities. How many subunits do myoglobin and hemoglobin each have?
b. One, Four
It's true that myoglobin consists of one subunit. However, hemoglobin consists of four subunits which contribute to its role in oxygen delivery.
Addition of ______________________alters the shape of the iron-heme complex, and therefore its absorption of light as indicated by its color change from dark purple (the color of hemoglobin in venous blood) to brilliant scarlet (the color of hemoglobin in arterial blood).
Oxygen binding alters the shape of the iron-heme complex, and therefore its light absorption properties as indicated by a color change.
Oxygen binding alters the structure of an entire hemoglobin tetramer, so the structures of oxyhemoglobin and deoxyhemoglobin are noticeably different. The oxyhemoglobin conformation is specifically referred to as the __________ state, whereas the deoxyhemoglobin conformation is referred to as the __________ state.
b. Relaxed or R and Tense or T
Oxygen binding causes a marked change in hemoglobin structure. In the presence of oxygen, hemoglobin is in the Relaxed state or R state. In the absence of oxygen, hemoglobin is in the Tense state or T state.
Patients with sickle cell anemia have atypical hemoglobin, which will distort the red blood cells into sickle shape during oxygen delivery. The substitution of a hydrophilic amino acid with a ____________amino acid in hemoglobin subunits results in the polymerization of hemoglobin, leading to the sickling of red blood cells.
Hydrophilic amino acids are water loving amino acids found on the surface of protein with no tendency towards polymerization. In case of sickle cell anemia, a hydrophilic amino acid - glutamate is substituted by a non polar-hydrophobic amino acid-valine, leading to polymerization of hemoglobin, fibril formation and eventually sickling of the red blood cells.
Hemoglobin consists of four protein subunits. Each subunit contains [a heme group] that holds [an iron atom], which can bind to [an oxygen moleule].
Hemoglobin protein consists of four protein subunits. Each subunit contains a heme group which binds an iron atom. The iron binds to oxygen, which can then be transported by hemoglobin.
When binding hemoglobin or myoglobin, CO binds in place of _________.
CO binds in place of oxygen.
Which one of these molecules is not considered a lipid?
a. Vitamin C
Vitamin C is a water-soluble vitamin and is not a lipid.
The acid portion of a fatty acid corresponds to which one of the following groups/molecules?
CH3 is considered as a methyl group and not an acid group.
COOH is a carboxylic acid group. A fatty acid consists of a hydrocarbon chain bound to the carbon atom of the COOH.
Saturated fatty acids have more _________________ than unsaturated fatty acids of the same length.
b. Hydrogen atoms
Both saturated and unsaturated fatty acids have the same number of oxygen atoms irrespective of their lengths because the only oxygen atoms are present as a part of the carboxylic acid group.
A carbon must always make four bonds. In an unsaturated fatty acid, the presence of double bonds between carbon atoms reduces the number of bonds available to bond with hydrogen. Consequently, an unsaturated fatty acid has fewer hydrogen atoms, than a saturated fatty acid of the same length.
How many hydrogens can be accommodated by the carbon (in bold) that is participating in the double bond:
Recall that carbon can form four bonds. The carbons that are participating in a double bond will bind to one hydrogen each. Notice that four out of three bond positions are already occupied by the carbon-carbon bonds.
True or False: Phospholipids that are part of a cell membrane contain only unsaturated fatty acids.
Phospholipids that make up the cell membrane contain two fatty acids attached to a glycerol backbone. An additional phosphate polar group bonds to the molecule and creates a polar end of the molecule. The two long chain fatty acids that are a part of the phospholipid can be of either variety - saturated or unsaturated fatty acids.
Which of the following is the fat storage molecule?
The specific fat storage molecule is a triglyceride, which consists of a glycerol backbone bound to three fatty acid chains.
Due to their amphipathic nature, phospholipids can form micelles and transport other lipids. The fatty acid chains that make up the phospholipids are the basis for their non-polar character, and the __________ is/are the basis of its polar nature.
d. phosphate group
Phospholipids have a phosphate group attached to the glycerol backbone that is the basis for their polar characteristic.
True or False: Acetyl-CoA can only be made from the beta oxidation of fatty acids.
Acetyl-CoA is central to metabolism. Carbohydrates, proteins, and fats can all produce Acetyl-CoA, though they use different pathways to make it.
Beta oxidation of a C14 fatty acid will make_______________ acetyl-CoA units after________ rounds of beta-oxidation.
a. seven, six
Each round of beta-oxidation results in the production of a two-carbon acetyl-CoA units, so the number of carbons in a fatty acid chain divided by two is how many acetyl-CoA units are made. The number of rounds needed is one less than the number of acetyl-CoA units produced because the last round of beta-oxidation produces two acetyl-CoA units. Thus, a C14 fatty acid will altogether make seven acetyl-CoA units after six rounds of beta oxidation.
Mammals and plants have the ability to synthesize their fatty acids. Which one of the following molecules is the precursor to building fatty acids?
Acetyl-CoA. Acetyl-CoA, which is the common product of many biomolecules, acts as a precursor for the synthesis of fatty acids. It provides the carbon atoms used in the synthesis of fatty acids.
Acetyl-CoA, a central molecule in metabolism, is produced in the mitochondrial matrix. However, it is used for the synthesis of fatty acids in the cytosol. The transport of the acetyl-CoA from the matrix to the cytosol occurs by the conversion of acetyl-CoA to_______________.
Acetyl-CoA combines with oxaloacetate to produce Citrate. Note that citrate is the first product produced in the citric acid cycle by the same reaction. Cells have the ability to mobilize citrate across the mitochondrial membrane. Thus, acetyl-CoA moves out of the mitochondria to the cytosol in the form of citrate. Once in the cytosol, the citrate is converted back to oxaloacetate and acetyl-CoA, and acetyl-CoA is utilized in fatty acid synthesis.
The inability to tolerate long-chain fatty acids in the diet could stem from a defect in________________.
c. beta-oxidation of long-chain fatty acids
All fats, carbohydrates, and proteins make acetyl-CoA, which is the precursor for the fatty acid synthesis. Intolerance towards a certain food stems from the inability to digest a specific biomolecule in that particular food.
Beta-oxidation of long-chain fatty acids. Beta-oxidation is a pathway that breaks down fatty acids into two carbon acetyl-CoA units that enter the citric acid cycle and electron transport chain, resulting in ATP production. Beta-Oxidation enzymes can be specific to chain lengths. Thus, a defect in an enzyme that is specific for long chain fatty acid beta-oxidation manifests as an intolerance towards foods containing long chain fatty acids.
Ketoacidosis is a dangerous outcome of uncontrolled diabetes. It is a result of the buildup of ketone bodies. What is the primary metabolic fuel that results in the build-up of the ketone bodies?
c. Fatty Acids
Glucose uptake by cells is impaired during diabetes, so glucose is not available for ATP production. Also, glucose does not contribute to ketone body formation.
Acetyl-CoA makes ketone bodies. During diabetes and under starvation conditions, the primary source for the acetyl-CoA is the fatty acids released from triglycerides. Acetyl-CoA typically enters the citric acid cycle or creates normal amounts of ketone bodies. However, in diabetic conditions, the citric acid cycle intermediates are being drawn out for the gluconeogenesis pathways. In such a situation, acetyl-CoA has limited oxaloacetate to enter the citric acid cycle. Instead, acetyl-CoA creates more ketone bodies, which acidifies the blood. Excessive production of these ketone bodies causes ketoacidosis.
Below is a diagram of the four steps of the beta oxidation cycle. Drag the correct small molecule to the step in the pathway to which it contributes.
The four steps of beta oxidation each involve a small molecule other than the fatty acid in the process, as shown below:
Fatty acid synthesis occurs in the ---, so its building block molecule acetyl-CoA must be transported out of the --- and into the --- using the --- transport system. The acetyl-CoA is then combined with --- with the help of the coenzyme molecule --- in order to form --- in the first committed step of fatty acid synthesis.
The correct answer is: Fatty acid synthesis occurs in the [cytosol], so its building block molecule acetyl-CoA must be transported out of the [mitochondria] and into the [cytosol] using the [citrate] transport system. The acetyl-CoA is then combined with [carbon dioxide] with the help of the coenzyme molecule [biotin] in order to form [malonyl‑CoA] in the first committed step of fatty acid synthesis.
If Zoey continues on her path of a no-fat diet, she could have a very poor wound healing response. Which one of the following lipid molecules can have an affect on this response?
Recall that phospholipids are crucial for cell membrane structure and fluidity. Additionally, in response to certain hormonal signals, certain fatty acids in the phospholipids are released from the cell membranes to produce other key lipid molecules such as eicosanoids. Eicosanoids play several roles in inflammation, fever, immunity and blood coagulation.
The nutritionist explains the importance of including diets rich in essential fatty acids. The essential fatty acids are __________________ fatty acids.
Certain kinds of polyunsaturated fatty acids such as omega-3 and omega-6 fatty acids are essential for health. The body can build most of the saturated fatty acids from the raw materials (acetyl-CoA) provided by other metabolites. However, we do not have the enzymes to add double bonds at certain positions (after C9, from the carboxylic acid end) in fatty acids as are found in the omega 3 and omega 6 fatty acids. Consequently, our body needs to obtain them from the diet. Essential fatty acids, as a part of phospholipids, play various key structural and functional roles.
True or False: Zoey can overcome any and all vitamin related deficiencies by supplementing her zero-fat diet with a daily supplement of multivitamins.
Fats are necessary to deliver the fat-soluble vitamins such as A, D, E and K. Absence of fat in the diet impact the absorption and delivery of the fat soluble vitamins that result in vitamin related deficiencies.
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