Unit 1 of 5
Study guide for CLEP CLEP Biology — Unit 1: Molecular and Cellular Biology. Practice questions, key concepts, and exam tips.
153
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What is the primary role of the polarity of the water molecule in biological systems?
To decrease the boiling point of water, allowing it to exist in a liquid state at higher temperatures
To reduce the surface tension of water, making it less essential for biological systems
To increase the viscosity of water, making it more difficult for cells to function
To disrupt the formation of hydrogen bonds with other molecules, allowing it to play a minor role in biological processes
To facilitate the formation of hydrogen bonds with other water molecules, allowing it to play a crucial role in biological processes
Answer: E — The polarity of the water molecule allows it to form hydrogen bonds, which is essential for its role in biological processes, such as protein folding and cell signaling.
A scientist is analyzing the structure of a newly discovered molecule and finds that it contains the sugar ribose and the nitrogenous base uracil. Which of the following is the most likely identity of this molecule?
DNA
Protein
RNA
Carbohydrate
Lipid
Answer: C — The presence of ribose and uracil indicates that the molecule is RNA, as DNA contains deoxyribose and thymine instead.
A biochemist measures the reaction rate of an enzyme at various substrate concentrations. At low substrate concentrations, the rate increases linearly with substrate addition, but at high concentrations, the rate plateaus. Which of the following best explains this biphasic response?
High substrate concentrations competitively inhibit the enzyme by blocking allosteric sites
The enzyme undergoes feedback inhibition triggered by accumulating product molecules
The enzyme becomes denatured at high substrate concentrations, reducing its catalytic efficiency
Substrate molecules aggregate at high concentrations, preventing enzyme-substrate complex formation
All available enzyme active sites become saturated, and further substrate additions cannot increase the reaction rate
Answer: E — This question tests understanding of Michaelis-Menten kinetics. At low substrate concentrations, enzyme active sites are available, so reaction rate increases linearly (first-order kinetics). At high concentrations, all active sites are occupied, creating a plateau at Vmax (zero-order kinetics)..
Microorganisms that produce methane are
Methanogens
Phototrophs
Chemolithotrophs
Halophiles
Psychrophiles
Answer: A — Methanogens is correct because methanogens produce methane gas.
Which of the following types of cells lacks a true nucleus?
Prokaryotic cells
Eukaryotic cells
Plant cells
Animal cells
Fungal cells
Answer: A — Prokaryotic cells is correct because prokaryotes lack a true nucleus..
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