Practice Questions

Propose a scientific reason why the relative abundance of carbon and hydrogen is significantly higher in living organisms compared to the non-living Earth's crust.

Justify why a continuous increase in substrate concentration does not lead to an infinite increase in the velocity of an enzyme-catalyzed reaction.

Justify why a protein is considered a heteropolymer, while cellulose is considered a homopolymer.

Name the two fractions obtained when a living tissue is ground with trichloroacetic acid ($Cl_3CCOOH$) and filtered.

Name the most abundant protein in the animal world and the most abundant protein in the whole biosphere.

Identify the three chemically distinct components of a nucleotide.

Define biomacromolecules and list two examples.

Name the specific type of covalent bond that links amino acids together in a protein.

Analyze the structural and functional relationship between an apoenzyme and a holoenzyme.

Compare and contrast saturated and unsaturated fatty acids based on their chemical structure and provide one example of each.

An enzyme catalyzes the transfer of an amino group from an amino acid to a keto acid. Analyze which of the six major classes of enzymes this catalyst belongs to and justify your classification.

Critique the method of determining the inorganic composition of a living tissue by burning it to 'ash'. What crucial information is lost in this process, and why is a different method required for organic analysis?

Evaluate the statement: 'Lipids are not strictly macromolecules, yet they are found in the acid-insoluble fraction.' Justify your evaluation based on their molecular weight and behavior during chemical analysis.

Evaluate the significance of the quaternary structure of a protein, using human hemoglobin (Hb) as an example. How does this level of organization contribute to its function which a single polypeptide chain might not achieve?

Design a graphical representation to compare the activation energy of a reaction with and without an enzyme. Your design must illustrate an exothermic reaction and clearly label the substrate (S), product (P), transition state, activation energy without enzyme ($E_{au}$), and activation energy with enzyme ($E_{ac}$).

Evaluate the roles of primary and secondary metabolites in a plant. Critique the notion that secondary metabolites are simply 'waste products' by providing examples of their ecological and human-welfare importance.

Explain why lipids are considered part of the acid-insoluble fraction despite having a molecular weight of less than 800 Da.

List the four levels of protein structure and briefly describe what the primary structure represents.

Describe the general structure of an $\alpha$-amino acid.

Describe how temperature and pH affect the activity of an enzyme.

Compare the relative abundance of Carbon (C) and Silicon (Si) in the Earth's crust versus the human body, as shown in Table 9.1. Analyze the significance of this difference for living organisms.

Demonstrate how a generic $\alpha$-amino acid with the structure R-CH($\text{NH}_2$)-COOH exists as a zwitterion in a solution of neutral pH.

Analyze why lipids, which have a molecular weight not exceeding $800$ Da and are therefore not strictly macromolecules, are found in the acid-insoluble fraction during the chemical analysis of a living tissue.

Compare the primary and tertiary structures of a protein. Analyze why the tertiary structure is considered absolutely necessary for the biological activities of proteins.

Compare the chemical composition of a nucleotide found in DNA with a nucleotide found in RNA.

Examine the relationship between substrate concentration and enzyme activity as depicted in a velocity vs. substrate concentration graph. Analyze why the reaction rate reaches a maximum velocity ($V_{\text{max}}$) and does not increase further with an additional increase in substrate concentration.

Apply the concept of activation energy to explain how enzymes bring about such high rates of chemical conversions.

Design an experiment to qualitatively identify the presence of protein, starch (a polysaccharide), and a simple sugar (monosaccharide) in three unknown food samples labeled A, B, and C. Justify the choice of reagents for each test.

Analyze the statement: 'A protein is a heteropolymer, not a homopolymer.'

Analyze the functional differences between primary and secondary metabolites, using one example for each to illustrate your points.

Create a classification scheme in the form of a simple flowchart to distinguish between a nitrogenous base, a nucleoside, and a nucleotide. Provide one specific example for each category.

Propose a reason why certain nucleic acids that act as enzymes are called 'ribozymes', and state the central biological concept their discovery challenged.

Based on the structure of a fatty acid, formulate an explanation for why lipids are generally insoluble in water. Distinguish between the properties of saturated and unsaturated fatty acids in your explanation.

Explain the difference between a nucleoside and a nucleotide. Provide one example of each.

Define the term 'zwitterion' in the context of amino acids.

Explain the difference between a homopolymer and a heteropolymer, using one example for each from the chapter.

Summarize the key differences between primary and secondary metabolites, providing two examples for each.

List the six major classes of enzymes according to the international classification system.

Formulate a hypothesis to explain why competitive inhibitors are effective as drugs to control bacterial pathogens. Design a simple in-vitro experiment to test if a new chemical, 'Compound X', acts as a competitive inhibitor for a specific bacterial enzyme.

A new enzyme is discovered that functions optimally at $95^{\circ}\text{C}$. Propose a likely natural source for this enzyme and justify why its tertiary structure remains stable at such high temperatures, unlike most enzymes from mesophilic organisms.

An enzyme is isolated from a thermophilic organism that lives in hot vents at $85^{\circ}\text{C}$. Analyze what would happen to its catalytic activity if the temperature is first lowered to $40^{\circ}\text{C}$ and then raised back to $85^{\circ}\text{C}$.

Compare the mechanism of a competitive inhibitor with the normal binding of a substrate to an enzyme's active site. Apply this comparison to explain the inhibition of succinic dehydrogenase by malonate.

Explain the role of co-factors in enzyme function and describe the three main types.

Examine the structural reason why starch forms a blue-colored complex with iodine molecules while cellulose, also a polymer of glucose, does not.

Create a hypothetical dipeptide using the amino acids Glycine and Alanine, where Glycine is the N-terminal amino acid. Draw its structure and clearly label the peptide bond, the N-terminus, and the C-terminus.