MCAT® (Medical College Admission Test®)

A. Enzymes increase the free energy of the reactants.. B. Enzymes decrease the activation energy of the reaction.. C. Enzymes are consumed in the reaction.. D. Enzymes shift the equilibrium position of the reaction..

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Explanation

Enzymes act as catalysts that speed up biochemical reactions by lowering the activation energy required for the reaction to proceed, without being consumed in the process.

Mushkovic BIOLOGY - Biological and Biochemical Foundations of Living Systems

During glycolysis, which molecule is directly converted into pyruvate?

A. Glucose. B. Fructose-1,6-bisphosphate. C. Glyceraldehyde-3-phosphate. D. Acetyl-CoA.

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Explanation

Glycolysis converts glucose into two molecules of pyruvate through a series of steps. Glyceraldehyde-3-phosphate is an intermediate that is directly converted into pyruvate in the later stages of glycolysis.

Mushkovic BIOLOGY - Biological and Biochemical Foundations of Living Systems

Which of the following statements about the fluid mosaic model of cell membranes is correct?

A. Phospholipids form a rigid bilayer.. B. Proteins are embedded within and can move laterally through the lipid bilayer.. C. Carbohydrates are only found on the intracellular side of the membrane.. D. Cholesterol is absent in eukaryotic cell membranes..

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Explanation

The fluid mosaic model describes the cell membrane as a flexible structure where lipids and proteins can move laterally within the layer, contributing to the membrane's fluidity.

Mushkovic BIOLOGY - Biological and Biochemical Foundations of Living Systems

In the central dogma of molecular biology, which process involves the synthesis of RNA from a DNA template?

A. Replication. B. Transcription. C. Translation. D. Reverse transcription.

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Explanation

Transcription is the process where an RNA molecule is synthesized from a DNA template, following the base pairing rules.

Mushkovic BIOLOGY - Biological and Biochemical Foundations of Living Systems

Which organelle is primarily responsible for the production of ATP through oxidative phosphorylation?

A. Nucleus. B. Endoplasmic reticulum. C. Mitochondrion. D. Lysosome.

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Explanation

The mitochondrion is known as the powerhouse of the cell, where ATP is produced through oxidative phosphorylation during cellular respiration.

Mushkovic BIOLOGY - Biological and Biochemical Foundations of Living Systems

What is the role of the enzyme DNA ligase in DNA replication?

A. Unwinding the DNA double helix. B. Adding nucleotides to the growing DNA strand. C. Sealing nicks and joining Okazaki fragments on the lagging strand. D. Synthesizing RNA primers.

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Explanation

DNA ligase is responsible for joining Okazaki fragments on the lagging strand by sealing the nicks in the sugar-phosphate backbone, ensuring the DNA is continuous.

Mushkovic BIOLOGY - Biological and Biochemical Foundations of Living Systems

Which of the following is a correct statement about the function of ribosomes?

A. Ribosomes are involved in the transcription of DNA to mRNA.. B. Ribosomes are the site of lipid synthesis.. C. Ribosomes facilitate the translation of mRNA into proteins.. D. Ribosomes modify and package proteins for secretion..

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Explanation

Ribosomes are the cellular structures where translation occurs, converting the genetic information in mRNA into a sequence of amino acids to form proteins.

Mushkovic BIOLOGY - Biological and Biochemical Foundations of Living Systems

What is the primary function of the sodium-potassium pump in animal cells?

A. Generating ATP. B. Maintaining the resting membrane potential. C. Facilitating the passive diffusion of sodium and potassium ions. D. Transporting glucose into cells.

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Explanation

The sodium-potassium pump actively transports sodium ions out of the cell and potassium ions into the cell, which is crucial for maintaining the resting membrane potential and cell volume.

Mushkovic BIOLOGY - Biological and Biochemical Foundations of Living Systems

Which metabolic pathway directly produces NADPH and ribose-5-phosphate?

A. Glycolysis. B. Citric Acid Cycle. C. Pentose Phosphate Pathway. D. Beta-oxidation.

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Explanation

The pentose phosphate pathway generates NADPH for anabolic reactions and ribose-5-phosphate for nucleotide synthesis, without directly producing ATP.

Mushkovic BIOLOGY - Biological and Biochemical Foundations of Living Systems

In a hypothetical organism, a mutation in the gene encoding for histone H1 results in defective chromatin structure. Which cellular process would most likely be affected?

A. Protein synthesis. B. DNA replication. C. Glycolysis. D. RNA splicing.

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Explanation

Histone H1 is involved in the packaging of DNA into chromatin. Defective chromatin structure would most directly affect DNA replication, as tightly packed chromatin must be loosened to allow replication machinery access to the DNA.

Mushkovic BIOLOGY - Chemical and Physical Foundations of Biological Systems

What is the primary function of myoglobin in muscle cells?

A. Transport oxygen from the lungs to tissues. B. Store oxygen for use during periods of high metabolic demand. C. Facilitate the breakdown of glucose. D. Catalyze the conversion of ADP to ATP.

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Explanation

Myoglobin is an oxygen-binding protein in muscle cells that stores oxygen and releases it during periods of high metabolic demand, ensuring a continuous supply of oxygen for aerobic respiration.

Mushkovic BIOLOGY - Chemical and Physical Foundations of Biological Systems

Which of the following describes the type of bonding and interaction within a DNA double helix?

A. Ionic bonds between phosphate groups. B. Hydrogen bonds between complementary nitrogenous bases. C. Covalent bonds between ribose sugars. D. Van der Waals interactions between nitrogenous bases.

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Explanation

The DNA double helix is stabilized by hydrogen bonds between complementary nitrogenous bases (adenine with thymine, and cytosine with guanine).

Mushkovic BIOLOGY - Chemical and Physical Foundations of Biological Systems

Which principle explains the increase in pressure observed in a closed system when temperature is increased, assuming volume remains constant?

A. Boyle's Law. B. Charles's Law. C. Dalton's Law. D. Gay-Lussac's Law.

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Explanation

Gay-Lussac's Law states that the pressure of a given mass of gas varies directly with the absolute temperature when the volume is constant.

Mushkovic BIOLOGY - Chemical and Physical Foundations of Biological Systems

During oxidative phosphorylation, the energy for ATP synthesis is directly provided by:

A. The flow of electrons along the electron transport chain. B. The reduction of NAD+ to NADH. C. The establishment of a proton gradient across the inner mitochondrial membrane. D. The splitting of water molecules.

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Explanation

The energy for ATP synthesis during oxidative phosphorylation comes from the proton gradient established across the inner mitochondrial membrane, which drives ATP synthase.

Mushkovic BIOLOGY - Chemical and Physical Foundations of Biological Systems

What is the main role of the enzyme carbonic anhydrase in red blood cells?

A. Transporting oxygen. B. Catalyzing the conversion of carbon dioxide to bicarbonate. C. Facilitating the absorption of glucose. D. Synthesizing hemoglobin.

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Explanation

Carbonic anhydrase catalyzes the reversible conversion of carbon dioxide and water to bicarbonate and protons, which is crucial for CO2 transport in the blood.

Mushkovic BIOLOGY - Chemical and Physical Foundations of Biological Systems

Which of the following is true regarding the relationship between Gibbs free energy (ΔG) and the spontaneity of a chemical reaction?

A. A reaction with ΔG > 0 is spontaneous.. B. A reaction with ΔG = 0 is at equilibrium.. C. A reaction with ΔG < 0 is non-spontaneous.. D. A reaction with ΔG = 0 has no change in entropy..

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Explanation

When ΔG = 0, the system is at equilibrium, and there is no net change in the concentration of reactants and products.

Mushkovic BIOLOGY - Chemical and Physical Foundations of Biological Systems

In an electrolytic cell, which of the following occurs at the cathode?

A. Oxidation. B. Reduction. C. Electron flow into the anode. D. Positive ions migrate away from the cathode.

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Explanation

In an electrolytic cell, reduction occurs at the cathode, where electrons are gained by the species being reduced.

Mushkovic BIOLOGY - Chemical and Physical Foundations of Biological Systems

What type of intermolecular force is primarily responsible for the high boiling point of water?

A. London dispersion forces. B. Dipole-dipole interactions. C. Hydrogen bonding. D. Ionic bonding.

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Explanation

Hydrogen bonding, which occurs between the hydrogen atom of one water molecule and the oxygen atom of another, is the primary force responsible for water's high boiling point.

Mushkovic BIOLOGY - Chemical and Physical Foundations of Biological Systems

In the context of enzyme kinetics, what does a low Km value indicate about an enzyme's affinity for its substrate?

A. Low affinity. B. High affinity. C. No affinity. D. It depends on the enzyme's Vmax.

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Explanation

A low Km value indicates high affinity of an enzyme for its substrate, meaning the enzyme can achieve its maximum catalytic efficiency at low substrate concentrations.

Mushkovic BIOLOGY - Chemical and Physical Foundations of Biological Systems

Which of the following statements about the photoelectric effect is correct?

A. The kinetic energy of emitted electrons increases with increasing light intensity.. B. No electrons are emitted below a certain threshold frequency, regardless of light intensity.. C. Electrons are emitted even at zero frequency if the light intensity is high enough.. D. The number of emitted electrons decreases with increasing light frequency..

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Explanation

According to the photoelectric effect, electrons are emitted from a material only if the incident light has a frequency above a certain threshold, regardless of the light's intensity.

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Shah Jahan

Mushkovic