Bch211 - Exam 2

Enzymes are sensitive to temperature because they are proteins. Proteins have a specific three-dimensional structure that is crucial for their function. High temperatures can disrupt this structure, causing the enzyme to lose its shape and therefore its function. This process is called denaturation. Therefore, it is true that enzymes can be denatured by high temperatures.

During anabolism, energy is consumed as the body builds complex molecules from simpler ones. Anabolic processes require energy input to synthesize substances like proteins, nucleic acids, and carbohydrates. This energy is obtained from the breakdown of ATP molecules, which release energy when their high-energy phosphate bonds are hydrolyzed. Therefore, it is correct to say that energy is generally consumed during anabolism.

In noncompetitive inhibition, the inhibitor binds to an allosteric site on the enzyme, causing a change in the enzyme's shape and reducing its activity. This means that the maximum velocity (Vmax) of the enzyme-catalyzed reaction is decreased, as the inhibitor is able to bind to the enzyme regardless of whether the substrate is present or not. Therefore, the value of Vmax changes in noncompetitive inhibition.

Reactions requiring energy often occur with the simultaneous hydrolysis of ATP. ATP is known as the energy currency of the cell and is used to fuel various cellular processes. Hydrolysis of ATP releases energy by breaking the high-energy phosphate bond, converting ATP into ADP (adenosine diphosphate) and inorganic phosphate (Pi). This energy is then utilized by the cell to perform various energy-requiring reactions, such as muscle contractions, active transport, and synthesis of macromolecules. Therefore, ATP is essential for providing the energy needed for cellular activities.

Diastereomers are stereoisomers that have different configurations at one or more chiral centers, but are not mirror images of each other. This means that they can have two or more chiral centers, as stated in the correct answer. The other options are incorrect because they either limit the number of chiral carbons or incorrectly describe the relationship between diastereomers.

A metal ion required for enzyme activity is called a cofactor. Cofactors are non-protein molecules that bind to enzymes and are essential for their proper functioning. Metal ions, such as zinc, iron, and magnesium, can act as cofactors by assisting in catalytic reactions or stabilizing the enzyme's structure. Cofactors are necessary for the enzyme to perform its biological function efficiently and are often involved in key metabolic processes within cells.

The lock-and-key model explains the property of specificity in enzymes. According to this model, enzymes have a specific shape or "lock" that only fits with a specific substrate or "key". This means that enzymes can only catalyze specific reactions by binding to specific substrates. The lock-and-key model helps to explain why enzymes are highly specific in their function and can only interact with certain molecules, leading to the property of specificity.

Aspirin acts as an irreversible inhibitor of the COX 1 enzyme, not the COX 2 enzyme. It covalently modifies the enzyme, inhibiting its ability to produce prostaglandins and thromboxanes. This irreversible inhibition is what gives aspirin its long-lasting effects. COX 2 inhibitors, on the other hand, selectively target the COX 2 enzyme, reducing inflammation and pain without affecting COX 1 and its protective effects on the stomach lining.

D-monosaccharides are preferred by human cells because they are easily metabolized and utilized for energy production. Human cells have specific enzymes that can only recognize and process D-monosaccharides, making them the preferred form. L-monosaccharides, on the other hand, are not recognized by these enzymes and cannot be efficiently metabolized by human cells. Therefore, D-monosaccharides are the preferred form for human cells.

When ATP is hydrolyzed to ADP, it undergoes a chemical reaction that releases energy. This release of energy leads to an increase in the number of possible microstates or arrangements of particles, resulting in an increase in entropy. Therefore, the correct answer is that entropy increases when ATP is hydrolyzed to ADP.

The active site of an enzyme is the specific region where the substrate molecule binds and undergoes a chemical reaction. This site is typically a small, three-dimensional pocket within the enzyme's structure that is complementary in shape to the substrate. The active site plays a crucial role in catalyzing the conversion of the substrate into a product by facilitating the necessary chemical reactions. It provides a favorable environment for the substrate to interact with the enzyme, promoting the formation of the transition state and lowering the activation energy required for the reaction to occur.

An enzyme is a biological catalyst that speeds up chemical reactions in living organisms without being consumed in the process. It lowers the activation energy required for a reaction to occur, allowing it to happen more quickly. Enzymes are not activators, carbohydrates, or lipids, but rather a specific type of protein that plays a crucial role in various metabolic processes.

Monosaccharides are the simplest carbohydrates because they consist of a single sugar unit. They are the building blocks of more complex carbohydrates such as oligosaccharides and polysaccharides. Monosaccharides are small, soluble molecules that can be easily absorbed and used by the body for energy. Examples of monosaccharides include glucose, fructose, and galactose.

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The turnover number refers to the number of substrate molecules that an enzyme can convert into product per unit time. In this case, a single molecule of the enzyme acted on 21000 molecules of substrate in 15 minutes. Therefore, the turnover number can be calculated by dividing the number of substrate molecules (21000) by the time (15 minutes), which gives us 1400. This means that the enzyme is capable of converting 1400 substrate molecules into product per minute.

The cyclic form of glucose is formed through the reaction of the aldehyde group with the hydroxyl group, resulting in the formation of a hemiacetal. In this reaction, the aldehyde group acts as the electrophile, while the hydroxyl group acts as the nucleophile. The reaction forms a cyclic structure with a hemiacetal linkage between the carbon atom of the aldehyde and the oxygen atom of the hydroxyl group. This cyclic form is important in glucose metabolism and plays a crucial role in various biological processes.

A noncompetitive inhibitor is a molecule that binds to an enzyme at a site other than the active site. This means that it does not compete with the substrate for binding to the active site. Instead, it binds to a different site on the enzyme, causing a conformational change that affects the enzyme's activity. This type of inhibition does not affect the affinity of the enzyme for the substrate (Km), but it reduces the maximum rate of reaction (Vmax). Therefore, the correct answer is "binds at a site other than the active site."

A cofactor is a non-protein molecule or ion that is required for the proper functioning of an enzyme. It can bind to the enzyme and assist in the catalysis of a reaction. In the given equation, the blank is most likely referring to a molecule or ion that is needed for the enzyme to function, making "cofactor" the correct term to fill in the blank.

Sucrose is a disaccharide because it is composed of two monosaccharides, glucose and fructose, joined together by a glycosidic bond. Disaccharides are carbohydrates that consist of two sugar molecules bonded together. Glucose, galactose, and fructose are monosaccharides, meaning they are single sugar molecules.

The sign of Gibbs Free Energy is negative ("-") when energy is released, not positive ("+"). This is because Gibbs Free Energy represents the maximum amount of work that can be obtained from a system at constant temperature and pressure. When energy is released, the system is becoming more stable and the Gibbs Free Energy decreases, resulting in a negative sign.

Inhibition is classified as noncompetitive when the inhibitor binds to a different site on the enzyme than the substrate, and the binding of the inhibitor causes a change in the enzyme's conformation, rendering it unable to catalyze the reaction effectively. In this case, "Hindrate" is an inhibitor that alters the apparent Vmax of the enzyme without affecting the Km, indicating that it binds to a different site on the enzyme than the substrate. Therefore, the correct answer is that "Hindrate" is a noncompetitive inhibitor.

In the induced-fit model of substrate binding to enzymes, the active site changes its conformation to fit the transition state. This means that the active site of the enzyme undergoes a structural change in order to accommodate the transition state of the substrate. This conformational change is crucial for the enzyme to properly bind and catalyze the reaction, as it allows for optimal interactions between the active site and the substrate's transition state. By adapting its shape to fit the transition state, the enzyme enhances the efficiency and specificity of the reaction.

The conditions required for maximum enzyme function are called "optimum conditions". These conditions refer to the specific pH, temperature, and substrate concentration at which an enzyme functions most efficiently. Enzymes are highly sensitive to changes in these factors, and any deviation from the optimum conditions can result in a decrease in enzyme activity. Therefore, maintaining the optimum conditions is crucial for maximizing enzyme function. The other options mentioned, such as low pressure, high temperature, room conditions, and standard conditions, are not specifically related to enzyme function and do not accurately describe the conditions required for maximum enzyme activity.

An increase in enzyme concentration would increase the rate of the reaction because enzymes act as catalysts, meaning they speed up the rate of a reaction without being consumed in the process. By increasing the concentration of enzymes, there are more available to catalyze the reaction, leading to a higher reaction rate. This is particularly true under saturation conditions, where the substrate concentration is already high enough that all available enzyme active sites are occupied. Therefore, increasing the enzyme concentration is the most effective way to further increase the rate of the reaction.

Ribose is a monosaccharide that is used to form nucleic acids. Nucleic acids, such as DNA and RNA, are composed of nucleotides, which consist of a sugar molecule (ribose or deoxyribose), a phosphate group, and a nitrogenous base. Ribose is a key component of RNA, where it helps in the formation of the sugar-phosphate backbone of the molecule. Therefore, ribose is the correct answer as it is specifically involved in the synthesis of nucleic acids.

The induced-fit theory suggests that enzymes can undergo conformational changes in order to accommodate the substrate. This means that the enzyme's active site is not rigidly shaped like a lock, but rather can change its shape to fit the substrate like a glove. This theory explains how enzymes can enhance the efficiency of chemical reactions by bringing the substrate molecules closer together and creating an optimal environment for the reaction to occur.

Starch is correctly called a complex carbohydrate because it is made up of long chains of glucose molecules. Complex carbohydrates are polysaccharides, which means they consist of multiple sugar molecules bonded together. Starch is a common form of energy storage in plants and is found in foods like potatoes, rice, and bread. Sucrose, fructose, and lactose are all examples of simple carbohydrates, as they consist of one or two sugar molecules and are typically found in fruits, table sugar, and dairy products, respectively.

Coenzymes are small molecules that work together with enzymes to facilitate various biochemical reactions in the body. They assist enzymes in catalyzing reactions by acting as carriers of chemical groups or electrons. Many vitamins serve as precursors for coenzymes, meaning they are converted into coenzymes once inside the body. Therefore, coenzymes are a common function of many vitamins in the body, as they play a crucial role in ensuring the proper functioning of enzymes and metabolic processes.

The optimum pH of an enzyme refers to the pH at which the enzyme exhibits maximum activity. In this case, the correct answer is 6.5, indicating that the enzyme has the highest activity at pH 6.5. This suggests that the enzyme functions most efficiently under slightly acidic conditions.

The given answer states that B-D-Lactose is a reducing sugar. This is because lactose contains a free anomeric carbon, which is the carbon that can open up and form a hemiacetal or hemiketal. In the case of lactose, the anomeric carbon is the carbon in the glucose residue. This carbon can undergo mutarotation, meaning it can interconvert between the alpha and beta forms, allowing it to reduce certain oxidizing agents. Therefore, B-D-Lactose is considered a reducing sugar.

Enzymes can reduce the net energy of a reaction by lowering the activation energy required for the reaction to occur. They do this by stabilizing the transition state, making it easier for the reactants to reach the necessary energy level for the reaction to proceed. This allows the reaction to occur more quickly and efficiently. Enzymes themselves are not consumed or used up in the reaction, but rather they can be reused multiple times.

The Lineweaver-Burk plot is used to determine the kinetic parameters of an enzyme-catalyzed reaction, including the Michaelis-Menten constant (Km). The y-intercept of the Lineweaver-Burk plot represents 1/Vmax, where Vmax is the maximum reaction rate. In this case, the y-intercept is 1.91 (sec/millimole), which means that 1/Vmax = 1.91 (sec/millimole). The slope of the plot represents Km/Vmax. Given that the slope is 75.3 L/sec, we can calculate Km by rearranging the equation: Km = slope / y-intercept = 75.3 L/sec / 1.91 (sec/millimole) = 39.4 millimolar (mM). Therefore, the correct answer is 39.4 millimolar (mM).

Sugars which contain an aldehyde group that can be oxidized are called reducing sugars. This is because the aldehyde group can undergo oxidation reactions, where it loses electrons and becomes oxidized. Reducing sugars are able to donate electrons to other molecules, making them good reducing agents. This property is important in various biological processes, such as glycolysis and the Maillard reaction. Glycosides are a different type of sugar compound that consist of a sugar molecule bonded to a non-sugar molecule. Simple sugars and oxidizing sugars do not specifically refer to sugars with an aldehyde group that can be oxidized.

Glycogen is a polysaccharide that serves as a storage form of glucose in animals. Structurally, glycogen is most similar to amylopectin. Both glycogen and amylopectin are highly branched polysaccharides composed of glucose units. They have a similar structure with many branches, allowing for efficient storage and release of glucose molecules when needed. Sucrose, amylose, and cellulose have different structures and are not as similar to glycogen as amylopectin is.

The overall energy change for the reaction AC can be determined by adding the individual energy changes of the reactions AB and BC. Since the energy change of AB is +15 Joule/mol and the energy change of BC is -25 Joule/mol, the overall energy change of AC would be +15 Joule/mol + (-25 Joule/mol) = -10 Joule/mol.

The given structure is shown in the beta (B) anomeric form. Anomeric forms refer to the different spatial arrangements of a cyclic sugar molecule, specifically the orientation of the hydroxyl group attached to the anomeric carbon atom. In this case, the hydroxyl group is in the beta position, which means it is oriented in the opposite direction as the substituent attached to the anomeric carbon.

Competitive inhibitors are molecules that compete with the substrate for binding to the active site of an enzyme. They do not change the maximum velocity (Vmax) of the enzyme-catalyzed reaction, but they do affect the affinity of the enzyme for the substrate, resulting in an increase in the apparent Km value. Additionally, competitive inhibitors interfere with substrate binding by occupying the active site, preventing the substrate from binding and reducing the enzyme's catalytic activity. Therefore, the correct answer is "This type of inhibitor both changes the Km and interferes with substrate binding."

A noncompetitive inhibitor is an inhibitor that binds to an enzyme at a site other than the active site. This means that it does not compete with the substrate for binding to the active site, but instead binds to a different site on the enzyme. This binding alters the enzyme's shape and function, preventing the substrate from binding and inhibiting the enzyme's activity. Therefore, a noncompetitive inhibitor is the correct answer because it binds to the enzyme at a site other than the active site.

The Lineweaver-Burk plot is useful in the analysis of enzymatic reactions because it allows for easier identification of points that deviate from a straight line compared to a curve. This is important in determining the validity of the data and assessing the accuracy of the experimental results. By plotting the reciprocal of the reaction rate against the reciprocal of the substrate concentration, any deviations from a straight line can be easily observed, indicating potential errors or inconsistencies in the data.

The given carbohydrate can be classified as a ketopentose because it is a five-carbon sugar with a ketone functional group. Ketopentoses have a ketone group (C=O) attached to one of the carbon atoms in the sugar molecule. This distinguishes them from aldopentoses, which have an aldehyde group (CHO) attached to one of the carbon atoms. The classification as a ketopentose indicates the specific structure and functional group present in the carbohydrate.

Enzyme induction refers to the synthesis or production of an enzyme in response to a cellular need. When the cell requires a particular enzyme to perform a specific function or to respond to changes in its environment, it can induce the production of that enzyme. This process allows the cell to regulate its enzyme levels and adapt to different conditions. Allosteric production, feedback control, and biofeedback are not accurate terms to describe this phenomenon.

The given structure has a glycosidic linkage between the first carbon of one sugar molecule and the fourth carbon of the adjacent sugar molecule. This type of linkage is called an alpha-1,4-glycosidic linkage.

Cellulose is a polysaccharide that contains B(14) linkages. It is a major component of plant cell walls and provides structural support to plants. Unlike glycogen, amylopectin, and amylose, which are all composed of glucose molecules linked by alpha(1-4) glycosidic bonds, cellulose is made up of glucose molecules linked by beta(1-4) glycosidic bonds. This difference in linkage results in a different structure and function for cellulose compared to the other polysaccharides listed.

The correct answer is "a D form". This means that the structure shown is in the D form configuration. The D form refers to the spatial arrangement of certain molecules, particularly sugars. In the D form, the hydroxyl group (-OH) on the highest-numbered chiral carbon is on the right side. This is in contrast to the L form, where the hydroxyl group is on the left side. Therefore, based on the given information, the structure shown is in the D form configuration.

If an inhibitor changes the slope of the Lineweaver-Burk graph, but not the x-intercept, it indicates non-competitive inhibition. In non-competitive inhibition, the inhibitor binds to a different site on the enzyme than the substrate, and both the enzyme-substrate complex and the enzyme-inhibitor complex are formed. This type of inhibition does not compete with the substrate for binding to the enzyme and therefore does not affect the x-intercept, which represents the affinity of the enzyme for the substrate. The change in slope indicates that the inhibitor affects the reaction rate without affecting the affinity of the enzyme for the substrate.

The Lineweaver Burke plot is used to analyze enzyme kinetics. It plots the reciprocal of the reaction rate against the reciprocal of the substrate concentration. In this plot, the slope of the line represents the enzyme's activity. If everything else has a higher slope, anything lower than it represents the activation space, indicating that the reaction is spontaneous. On the other hand, everything above it represents the inhibition space, indicating that the reaction is nonspontaneous. Therefore, option 1 is the correct answer.