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WGU Biochemistry OA Exam | Questions with 100% Correct Answers
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WGU Biochemistry OA Exam | Questions with 100% Correct Answers
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WGU Biochemistry OA Exam |Questions with 100% Correct Answers
Alzheimer 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 - The Amyloid-beta plaque and tau protein become misfolded,
exposing hydrophobic amino acids on their exterior. When hydrophobic amino
acids are exposed to water, they actively seek out ways to avoid that water. One
way to do this is to find other exposed hydrophobic amino acids, located on other
misfolded proteins. When misfolded proteins begin to gather, they form
aggregates, ultimately resulting in neuronal cell death.
As a piece of bacon is heated in a skillet on the stove, you observe that the
appearance of the bacon changes. You may even notice that the bacon
becomes crispy if left in the skillet. What type of bonds or interactions in
proteins are susceptible to temperature changes? Why?
'Hydrophobic interactions. As the temperature increases, as it does in the skillet,
the atoms in the proteins in bacon begin to move more rapidly. This causes the
hydrophobic areas of the protein to become exposed'. While hydrophobic
interactions do involve hydrocarbons, like oil, oil does not complete dissipate
when cooked. Hydrophobic interactions are instead disrupted by the heat due to
the movement of atoms in the proteins.
Which property of enzymes is illustrated in the final step of the enzymatic cycle?
Enzymes are reusable. - In the final step of the enzymatic cycle, the product is
released and the enzyme is able to bind to a new substrate and begin the
cycle again.
In the enzyme cycle, which step immediately follows induced fit?
Formation of the enzyme-product complex - The induced fit refers to the
conformational change that the enzyme undergoes when it binds to the substrate
,to form the enzyme-substrate complex. Therefore, the enzymatic cycle step that
occurs after the induced fit is the formation of the enzyme-product complex.
Which type of inhibition occurs when a particular drug binds to the active site of
an enzyme?
Competitive - Competitive inhibitors compete with the substrate to bind to the
active site of the enzyme.
Salivary amylase, an enzyme responsible for partial digestion of
carbohydrates, has optimum activity at a pH value of 6.8.
What is the impact on the activity if the pH is decreased to 4.0?
Significantly decrease - A drop in pH from 6.8 to 4.0 is a significant change in pH.
Recall that the hydrogen bonds and ionic bonds that hold protein structures
together can be broken by changes in pH. The disruption in protein structure
due to this pH change will also significantly decrease amylase activity.
Lipase is an enzyme with an optimum temperature of 98.6°F and an optimum
pH of 7.0 in the duodenum in the human body. If a person is experiencing a
fever of 99.8°F, what will increase the activity of the lipase enzyme?
Decrease in temperature - An enzyme will have the highest activity when it is
under optimal conditions. In this case, the fever of 99.8 is above the optimal
temperature, so lowering the temperature will increase activity.
Low levels of glutathione are associated with neurological, immunological,
and cardiovascular impairments. Two enzymatic reactions are involved in the
synthesis of glutathione. In the second enzymatic reaction, glutathione
synthetase converts glycine to glutathione. What would potentially decrease
risks associated with low levels of glutathione?
'Feedback'. - The keywords here are that glutathione accumulates and binds to an
enzyme in the pathway to prevent synthesis. Feedback inhibition occurs when a
product of a pathway turns into an inhibitor of an enzyme earlier in the pathway.
Which class of enzymes impacts protein function by temporarily removing a
phosphate?
,Phosphatase- Phosphatases are enzymes that remove phosphate groups from the
substrates.
How does the activation energy of enzyme-catalyzed reactions compare to
those of corresponding uncatalyzed reactions?
The activation energy of enzyme-catalyzed reactions are lower than the
uncatalyzed reaction - The activation energy is the amount of energy needed to
get the reaction started and over the energy hill to form products. Enzymes
reduce the amount of energy needed to start the reaction or lower the amount of
energy needed to climb the energy hill.
A final product of a four-step metabolic pathway serves as a noncompetitive
inhibitor, binding to an enzyme in this pathway and temporarily turning off
the pathway. Which enzyme is most likely to be targeted by the inhibitor?
The first enzyme in the pathway - The final product's structure is more unlike
the substrate for the first enzyme in the pathway than any other, and thus the
least likely to fit the active site of enzyme 1.
The enzyme glucokinase only binds its substrate glucose and converts glucose
into the product glucose-6-phosphate. Which property of enzymes is
described by this scenario?
Specificity - Enzymes have a high degree of specificity. They will bind to one
specific class of molecules and usually catalyze only one type of reaction.
Which one of the following paths requires less activation energy to convert the
reactants into the products? The options include the path indicated by a bold
line, and the path indicated by a dotted line.
In presence of an enzyme-Dotted line - The path with the bold line represents the
one with the higher amount of energy needed to get the reaction started and
over the energy hill to form products, or a higher activation energy. For the path
represented by the dotted line, the reactants need less energy to climb the hill,
or a lower activation energy, to get the reaction over the hill to form products.
Select True or False: the lower the activation energy for a reaction, the
faster the reaction rate.
, T- If less energy is needed to get the reaction over the energy hill, it goes faster.
Enzymes help bring all of the items needed for a reaction together in the best
way, so less energy is needed for the reaction to get started. This lowers the
activation energy for the reaction and speeds up the reaction so that it can go
much faster than if the enzyme were not present.
How do enzymes eliminate the need for high temperatures to complete a
reaction?
The need for high temperatures is eliminated by lowering the activation energy
needed for the reaction - Kinetic energy is the energy of motion. When heat is
added to a reaction, it causes the particles to move faster, and the temperature
typically increases. The presence of the enzyme actually lowers the amount of
heat needed for the reaction, or lowers the amount of kinetic energy needed for
the reaction to occur.
An enzyme that adds a phosphate group is a _________ . An enzyme that
removes a phosphate group is known as a __.
kinase, phosphatase
Which level of protein structure provides enzymes with their substrate
specificity?
Tertiary structure
Which of the following characteristic of an enzyme is responsible for speeding
up the reaction?
They decrease activation energy - Enzymes are called catalysts, which means they
help speed up a reaction, and they are not used up by the reaction. They have the
right amino acids in the right places to help change the substrate into product,
and they still have these amino acids when the reaction is over. All of these
factors assist the enzyme in lowering the activation energy, which means that less
energy is required to start the reaction (or get it over the energy hill) than when
the enzyme is not present. Therefore, when the enzyme lowers the activation
energy this results in a faster reaction.
A substrate binds to an enzyme at a specific site, which is referred to as a(n) .
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