Leptin Is a Circulating Hormone That Is Produced by Fat

question 17

Multiple Choice

Leptin is a circulating hormone that is produced by fat cells and plays a role in body metabolism and obesity.It normally binds to receptors in the brain and inhibits appetite.Studies have demonstrated that when obese mice that are leptin deficient are injected with leptin they quickly lose their excess weight.Interestingly,however,many overweight people have high levels of leptin in their bloodstream.Why do you think that the high levels of leptin in obese individuals are insufficient to curb their appetite?

• A)Paracrine signaling may be disrupted in obese people with high levels of leptin.
• B)Obese people who have high levels of leptin may have a leptin receptor with decreased sensitivity.
• C)The form of leptin released by obese people may lack protein kinase activity.
• D)In obese people with high levels of leptin,the leptin is a non-functional second messenger.

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Definitions:

Fluid-Mosaic Model

Model for the plasma membrane based on the changing location and pattern of protein molecules in a fluid phospholipid bilayer.

Phospholipid Bilayer

The fundamental structure of biological membranes, consisting of two layers of phospholipids that create a barrier around cells.

Glycolipids

Molecules consisting of a carbohydrate bonded to a lipid, play key roles in cell recognition and membrane structure.

Blood Type

A classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells.