Multiple Choice
Which eukaryotic organelle is described as a membranous channel extending inward from the muscle fiber membrane and plays a key role in transmitting action potentials?
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2. Cell Chemistry & Cell Components
Introduction to Eukaryotic Organelles
Multiple Choice
Which of the following best describes a key difference between beta-keratin and alpha-keratin in eukaryotic cells?
A
Alpha-keratin contains more sulfur than beta-keratin.
B
Alpha-keratin is a carbohydrate, while beta-keratin is a lipid.
C
Beta-keratin is only found in mammals, while alpha-keratin is found in birds and reptiles.
D
Beta-keratin forms rigid structures like feathers and scales, while alpha-keratin is found in flexible structures like hair and skin.
Verified step by step guidance1
Understand the context of keratin proteins: Keratin is a structural protein found in eukaryotic cells, and it plays a key role in forming protective structures such as skin, hair, feathers, and scales.
Differentiate between alpha-keratin and beta-keratin: Alpha-keratin is primarily found in mammals and contributes to flexible structures like hair and skin. Beta-keratin, on the other hand, is found in birds and reptiles and contributes to rigid structures like feathers and scales.
Analyze the sulfur content: Alpha-keratin contains a higher proportion of sulfur due to the presence of cysteine residues, which form disulfide bonds. This is not the defining difference between alpha-keratin and beta-keratin, but it contributes to the flexibility of alpha-keratin.
Clarify the chemical composition: Both alpha-keratin and beta-keratin are proteins, not carbohydrates or lipids. This eliminates the option suggesting a difference in macromolecule type.
Conclude the key difference: The defining characteristic is the structural role of each type of keratin—alpha-keratin is associated with flexible structures, while beta-keratin is associated with rigid structures.
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