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Greta C.
PhD Student at the University of Louisville
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Nutrition
TutorMe
Question:

Do you think that a person who consumes a diet that consists of moderate carbohydrate intake would have a more or less stable blood sugar concentration than that of a person who consumes a diet high in carbohydrates? Explain your answer.

Greta C.
Answer:

A person who consumes a diet that consists of moderate carbohydrate intake will have a more stable blood sugar concentration than a person who consumes a diet relatively high in carbohydrates. Carbohydrates come in a variety of forms, but ultimately all forms of carbohydrates are converted to glucose in the body. Blood sugar (or blood glucose) is regulated by a negative feedback mechanism. This means that a stimulus (blood glucose levels) is continuously monitored by a sensor. This sensor will compare the current levels to a control, or the normal level that should exist. If the sensor reports a disturbance that is outside normal limits, it activates a response via an effector(s). In this example, the effectors are the hormones insulin and glucagon. Insulin is the hormone that lowers blood glucose and glucagon is the hormone that raises blood glucose. If a person continuously eats a high carbohydrate diet, then this negative feedback loop will be continuously activated because of the high blood sugar levels. The body will need to constantly release insulin to attempt to decrease blood sugar concentrations. This causes unstable blood sugar concentrations because levels rise very high after consumption but then drop drastically due to the high amount of insulin release. In a person that consumes an appropriate amount of carbohydrates, insulin release is much smaller and blood sugar is easier to regulate within normal limits.

Health and Medicine
TutorMe
Question:

Compare and contrast these two forms of body composition measurement: hydrostatic weighing (hydrodensitometry) and skinfold measurements. Name a population for which each measure would be best utilized and explain why.

Greta C.
Answer:

Hydrostatic weighing is currently considered the gold standard measurement for determining body composition. It is an indirect method and provides a two compartment model. Skinfold measurements are widely available and easily administered. This method is doubly indirect and also provides a two compartment model. Hydrostatic weighing is not nearly as widely available as skinfold testing. This method is usually performed in a lab by a highly trained technician. This option is usually more expensive and time consuming. Equations for hydrostatic weighing are derived from cadaver studies, making them highly accurate (+/- 3% margin of error). Skinfold measurements are available at almost any health or fitness facility. It is relatively inexpensive and is reliable if performed by a trained technician. If performed correctly this test has a similar margin of error to hydrostatic weighing (+/- 3.5%). Both methods break down the subject's composition into fat mass and fat free mass. Hydrostatic weighing would be most appropriate for athlete's participating in a high level of competition or someone who needs a very accurate measurement. For example, wrestlers may need to prove their body fat percentage to compete at a certain weight class. Skinfold measurements are more appropriate for anyone that wants a relatively accurate and affordable test. For example, someone that wants to begin an exercise routine could have skinfold measurements taken before and after their 12-week program to compare results.

Anatomy
TutorMe
Question:

The composition of intracellular fluid and extracellular fluid is very different. The plasma membrane of the cell separates these two components. Explain the "fluid mosaic model" of plasma membrane structure and give one example of a mechanism that a cell may use to transport substances across this membrane.

Greta C.
Answer:

The plasma membrane consists of two components: lipids and proteins. In the "fluid mosaic model," lipids make up the "fluid." Two types of lipids exist in the plasma membrane, phospholipids and cholesterol. Phospholipids have a long hydrocarbon tail and a carboxyl group. The hydrocarbon tail is hydrophobic, or water fearing. The carboxyl group is hydrophilic, or water loving. All the phospholipids form a lipid bilayer, so that the hydrophobic tails are oriented towards each other and the carboxyl groups are oriented towards the aqueous media. Cholesterol is the other lipid component of the plasma membrane. Cholesterol scatters itself among the phospholipids, ensuring that the fatty acid chains do not stick together and adding both flexibility and rigidity to the membrane. The "mosaic" component of this model is protein. There are two types of proteins in the plasma membrane: integral and peripheral. Integral proteins are embedded in the lipid bilayer, meaning they are available to both the inside and outside of the cell. Peripheral proteins do not cross the bilayer and may face either the ECF or ICF, but not both. An example of transport across the plasma membrane is the usage of an integral protein (creating a channel) to transport water-soluble molecules or ions across the membrane without touching the hydrophobic portion of the bilayer.

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