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Multiple Choice
Which statement about the sidedness of the plasma membrane is correct?
A
Parts of proteins that are exposed on the cytoplasmic side of the endoplasmic reticulum are also exposed on the cytoplasmic side of the plasma membrane.
B
The asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is being constructed.
C
Every integral membrane protein has a specific orientation in the plasma membrane.
D
The two lipid layers may differ in specific lipid composition.
E
All of the listed responses are correct.
Verified step by step guidance
1
Understand that the plasma membrane is asymmetrical, meaning that the two sides of the membrane can have different compositions and functions.
Recognize that proteins synthesized in the endoplasmic reticulum (ER) maintain their orientation when they are transported to the plasma membrane. This means that parts of proteins exposed to the cytoplasm in the ER will also be exposed to the cytoplasm in the plasma membrane.
Acknowledge that the asymmetrical distribution of proteins, lipids, and carbohydrates is established during the construction of the membrane, particularly in the ER and Golgi apparatus, and maintained as they are transported to the plasma membrane.
Understand that integral membrane proteins have a specific orientation in the membrane, which is crucial for their function. This orientation is determined during their synthesis and insertion into the membrane.
Recognize that the two lipid layers of the plasma membrane can have different lipid compositions, contributing to the membrane's asymmetry and functional specialization.