Biochemistry Unit 3 MCQs

Questions and Answers

Which of the following statements best helps explain how the lead ion causes inhibition of Aminolevulinate dehydratase (ALAD)?

It enhances the enzyme's activity.

It has no effect on the enzyme.

It increases the zinc ion concentration.

It changes the three-dimensional structure of the active site so that ALAD is no longer compatible with its substrate. (correct)

Which of the following statements correctly explains the observed effect of acetylcholine concentration on the rate of the enzyme-catalyzed reaction of Acetylcholinesterase (AChE)?

Acetylcholine has a competitive inhibitor.

The active site of AChE is specific for acetylcholine, and only one substrate molecule can occupy the active site at a time. (correct)

Enzyme concentration is the limiting factor.

Increasing substrate levels always leads to proportional increases in reaction rate.

Based on a model explaining enzyme-substrate interactions, which of the following statements best explains an enzyme's specificity for a particular substrate molecule?

Enzymes can change shapes to fit any substrate.

A molecule with positive charges interacts with negatively charged side chains in the enzyme's active site.

Substrates are non-specific and fit any active site.

A molecule with negative charges interacts with positively charged side chains in the enzyme's active site. (correct)

Which of the following best describes the contents expected to be contained in one of the five control test tubes in the catalase experiment?

pH 4 buffer solution and hydrogen peroxide only. Signup and view all the answers

Which test tubes are controls in the student's experiment investigating temperature on enzyme function?

Test tubes 1, 3, 5, and 7. Signup and view all the answers

Which statement best helps justify the inclusion of group 2 as one of the controls in the experiment investigating soil bacteria and plant defense enzymes?

It will show whether the changes observed in group 1 depend on the metabolic activity of soil bacteria. Signup and view all the answers

Which statement best helps justify the inclusion of test tube 5 in the pectinase experiment?

It will act as a control for test tube 6 by showing the effect of the presence or absence of the enzyme. Signup and view all the answers

What effect does adding urea have on the function of certain enzymes?

Function will be disrupted by adding the urea and regained by removing the urea. Signup and view all the answers

What will be the immediate result of adding more substrate to the reaction mixture?

The amount of product will increase until the reaction reaches its equilibrium point or until the substrate is used up by the reaction. Signup and view all the answers

Which statement best justifies the claim that reproductive behavior of European flycatchers is influenced by the availability of energy sources?

Caterpillar biomass availability coincides with fledging. Signup and view all the answers

Which statement best helps justify the researcher's claim about photosynthesis and thermodynamics?

The total system that includes photosynthetic organisms and the Sun becomes less ordered over time. Signup and view all the answers

Which statement provides reasoning that supports the claim that brown fatty tissue keeps an animal warm?

The uncoupling protein in this tissue reduces the proton gradient across the membrane and thus produces heat to warm the animal without ATP production. Signup and view all the answers

Which graph best represents data supporting the claim that spinach leaves capture the most energy from light waves in the range of 500 nm to 600 nm?

A graph showing the least amount of light absorbed at wavelengths between 500 nm and 600 nm. Signup and view all the answers

Which type of evidence best supports the claim about prokaryotic organisms contributing to the oxygen in Earth's early atmosphere?

Evidence that the cyanobacteria produced oxygen as a by-product of photosynthesis. Signup and view all the answers

Which statement best clarifies how the data support the researcher's claim regarding the herbicide's effect?

ATP synthase activity depends on a proton gradient across the thylakoid membrane. Signup and view all the answers

Which statement best establishes a connection between the observation of bacteria with plasmids and the researcher's claim?

Some plasmids contain antibiotic resistance genes. Signup and view all the answers

Which of the following statements best justifies the claim that phycobiliproteins allow cyanobacteria to survive better than green algae?

The additional pigments absorb light at wavelengths that green algae cannot absorb; this may allow cyanobacteria to capture more light energy for photosynthesis than green algae can in certain areas. Signup and view all the answers

Which of the following statements best helps justify the researcher's claim about yeast's ability to survive in different environments?

Yeast cells produce invertase, which is an enzyme that catalyzes the conversion of the disaccharide sucrose into glucose and fructose. Signup and view all the answers

What effect will a change from a moderately acidic environment (pH near 6) to a basic environment have on peroxidase activity?

Peroxidase activity will decrease. Signup and view all the answers

Which action will provide a negative control for the peroxidase investigation?

Repeating the experiment using heat-denatured peroxidase. Signup and view all the answers

Which statement best justifies using oxygen gas production to measure reaction rates in the peroxidase investigation?

The experiment can be repeated without guaiacol, which will reveal the effect of guaiacol on the reaction rates. Signup and view all the answers

Study Notes

Enzymes and Inhibition

Aminolevulinate dehydratase (ALAD) is inhibited by a lead ion, which alters its active site structure, preventing substrate compatibility.
Acetylcholinesterase (AChE) has an active site specific to acetylcholine; enzyme activity varies with substrate concentration due to saturation effects.

Enzyme Specificity and Interactions

Substrate specificity in enzymes involves favorable interactions between substrate molecules and amino acid side chains in the active site.
A negatively charged molecule interacts with positively charged side chains, influencing enzyme-substrate compatibility.

Experimental Design and Controls

Catalase functions best at specific pH levels; control test tubes contain only buffer and substrate, without the enzyme.
Control groups in experiments help determine the influence of experimental variables on enzyme activity, such as soil bacteria's impact on plant root enzymes.

Effects of Environmental Conditions

Salinity affects pectinase function; a control tube without the enzyme showcases its necessity for the reaction.
Urea disrupts an enzyme's structure, impairing function; removing urea restores its activity.

Reaction Dynamics

Adding more substrate increases product formation until reaction equilibrium is reached.
Young European flycatchers depend on caterpillar biomass for growth, linking reproductive behavior to energy source availability.

Photosynthesis and Energy Capture

Photosynthetic organisms capture solar energy without violating the second law of thermodynamics; the overall system becomes less ordered.
Brown fat mitochondria contain uncoupling proteins that allow uncontrolled proton leaking for heat production rather than ATP synthesis.

Antioxidant Enzymes and pH Influence

Peroxidase activity is impacted by pH; changing from mildly acidic to basic environments reduces enzyme effectiveness.
Control measures, such as using denatured peroxidase, validate the experiment's findings by assessing baseline activity levels.

Modifications and Experimental Accuracy

Utilizing oxygen production as a measurement can control for variables like the inclusion of guaiacol in peroxidase activity experiments.

Genetic Variation and Survival

Genetic diversity enables organisms to adapt to varying environments; plasmids in bacteria can convey antibiotic resistance, enhancing survival chances.

Unique Pigment Functions

Phycobiliproteins in cyanobacteria offer survival advantages in specific aquatic conditions, absorbing light at wavelengths inaccessible to green algae.

Enzyme Adaptability

Yeast produce enzymes like invertase, enabling them to metabolize diverse energy sources, contributing to their adaptability across environments.

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Description

Test your knowledge with this set of MCQs focused on Unit 3 of biochemistry. This quiz explores the role of enzymes like aminolevulinate dehydratase and the impact of metal ions on their activity. Challenge yourself and enhance your understanding of enzyme inhibition.