Structure of Integral and Peripheral Proteins Quiz

The function of a membrane protein refers to its role in various cellular processes. Cell division is not a function of membrane proteins. Membrane proteins are involved in intercellular transportation, cell adhesion, and cell interaction, which are essential for communication, signaling, and maintaining the structural integrity of cells. However, cell division is primarily regulated by specific proteins and enzymes that are not necessarily associated with the cell membrane.

The correct answer is 76% because the inner membrane of the mitochondria is primarily composed of proteins, which make up a significant portion of its structure. These proteins play crucial roles in various functions of the mitochondria, such as electron transport and ATP synthesis. The remaining percentage is made up of lipids, including phospholipids and cholesterol, which provide structural support to the membrane.

Peripheral proteins are the protein types that avoid coming into contact with the phospholipid bilayer's hydrophobic core. Unlike integral proteins, which are embedded within the membrane, peripheral proteins are loosely bound to the surface of the membrane. This positioning allows them to interact with the hydrophilic heads of the phospholipids, avoiding contact with the hydrophobic tails in the core of the bilayer. Peripheral proteins often serve as receptors or enzymes and can be easily detached from the membrane without disrupting its structure.

DNA polymerase is not found in peripheral membranes because it is primarily located in the nucleus, where it carries out the replication of DNA. Peripheral membranes, on the other hand, are located at the periphery of the cell and are involved in processes such as signal transduction and membrane trafficking. Therefore, DNA polymerase does not belong to the category of proteins found in peripheral membranes.

Peripheral proteins are the loosely connected cytoskeleton proteins with the cytosolic face of the bilayer. These proteins are not embedded within the lipid bilayer like integral proteins, but rather associate with the membrane indirectly through electrostatic interactions or by being anchored to integral proteins. They can be easily detached from the membrane without disrupting the lipid bilayer. Peripheral proteins play important roles in cell signaling, membrane trafficking, and maintaining cell shape and structure.

Peripheral membrane proteins are proteins that are temporarily attached to the cell membrane through weak interactions, such as electrostatic forces or hydrogen bonding. These proteins can easily detach from the membrane and move within the cell or interact with other proteins. This reversibility allows peripheral membrane proteins to dynamically regulate various cellular processes, such as signal transduction and membrane trafficking. In contrast, anchored proteins are permanently attached to the cell membrane, while membrane proteins and intrinsic proteins are broad categories that can include both reversible and irreversible binding to the cell membrane.

A transmembrane protein refers to a protein that spans across the cell membrane, with portions of it on both the inside and outside of the cell. G proteins are a type of transmembrane protein that play a crucial role in signal transduction, relaying signals from cell surface receptors to intracellular pathways. GPCRs (G-protein coupled receptors), glycophorin, and bacteriorhodopsin are all examples of transmembrane proteins, but G protein specifically refers to a class of proteins involved in signal transduction.

Integral membrane proteins are also referred to as intrinsic proteins because they are embedded within the lipid bilayer of the cell membrane. These proteins have hydrophobic regions that interact with the hydrophobic core of the membrane, allowing them to span across the membrane. They play crucial roles in various cellular processes such as transport of molecules across the membrane, cell signaling, and cell adhesion.

G proteins are a type of protein that are found in peripheral membranes. They are involved in signal transduction, relaying signals from cell surface receptors to intracellular signaling pathways. G proteins play a crucial role in various cellular processes such as cell growth, differentiation, and metabolism. Therefore, out of the given options, G proteins are the correct answer as they are specifically known to be found in peripheral membranes.

The correct answer is 18%. Myelin is a substance that covers the nerve axons and is composed of both protein and lipids. While the exact composition may vary, on average, approximately 18% of the myelin membrane is made up of protein.