Dramatic temperature changes can induce membrane remodeling involving changing f

Question

Dramatic temperature changes can induce membrane remodeling involving changing fatty acid structure in membrane phospholipids. This will occur during the transition from winter to spring and vice versa. The purpose of remodeling is to maintain a constant level of membrane fluidity in the cell. Which of the following describes the change you would see in the lipid bilayer of a bear when it comes out of hibernation (choose all that apply)?

The ratio of long to short fatty acid tails in membrane phospholipids decreases

The number of phospholipids in the membrane decreases

The ratio of long to short fatty acid tails in the membrane phospholipids increases

The number of phospholipids in the membrane increases

There is an increase in the saturation state of the fatty acid tails of membrane phospholipids

There is a decrease in the saturation state of the fatty acid tails of membrane phospholipids

Questions 7 and 8. You are a grad student studying the biochemical properties of 2 proteins, each containing ~ 270 amino acids. You entered their primary amino acid sequences into the protein database and generated the plots shown below in which the relative average hydrophobicity of amino acids are plotted on a scale of 1-10 (with 1 being very hydrophilic and 10 being very hydrophobic). The individual data points on the graph represent the average hydrophobicity of 5 amino acid blocks (for example, amino acids 1-5, 2-6, 3-7, etc), all the way along the protein. Match the graph with the type of protein you think it might be (choose ALL THAT APPLY from the list below).

Peripheral Membrane Protein

Transmembrane channel

Cell Surface Receptor

Lipid Anchored Protein

Transmembrane Anchor

7________ (choose all that apply)

8________(Choose all that apply)

Explanation / Answer

Please find the answers below:

Part 6: During hibernation, animals undergo long-term stabilization and stay non-motile in their positions and simultaneously conserve energy. In this scenario, the physiological state of the body needs to be maintained in order to support vital functions. Among all the vital functions, it remains highly important to maintain the physical state of cells as well. Since eukaryotic cells comprise of a fluid plasma membrane, it is highly important to preserve the fluidity of the membrane to support translocation of material across the membrane. In order to confirm this fluidity, the hibernating animals have the tendency to accumulate large amount of un-saturated fatty acids and phospholipids before onset of hibernation. These fatty acids and phospholipids help in constitution of the membrane fluidity and thus, regulate the structural integrity of cells. Thus, based upon this explanation, the correct choices are:

1. The number of phospholipids in the membrane increases

2. There is a decrease in the saturation state of the fatty acid tails of membrane phospholipids

Answer 7: According to the data, it can be seen that majority of the proteins are hydrophilic in nature. Such proteins are highly stable and soluble in water and show poor stability and solubility in fatty acids/lipids. Such proteins are thus abundant on the cytoplasmic side and the external surface of the plasma membrane. These proteins make up the receptors on the plasma membrane and cytoplasmic domains of many signalling proteins. However, a slight peak of hydrophobicity is also seen because the anchoring part of these proteins must be stable in lipids. Thus, the correct choices are:

Peripheral Membrane Protein and transmembrane receptors.

Answer 8: The hydrophobic proteins are those which are insobluble in water. Such proteins remain in integral part of the transmembranous structure of the plasma membrane owing to their solubility and stability in lipids. Examples of such proteins are channel proteins, anchor proteins etc such as voltage gated calcium channels. Thus, the correct choices are :

Transmembrane channel, lipid anchor and transmembrane anchor

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