Question 1

Which of the following changes in metabolic flux would be expected to occur during long periods without food?

Accepted Answer

During long periods without food, the body starts to break down its own protein (muscle tissue) to release amino acids which can then be used as an energy source. This is known as protein degradation. Therefore, option D is the correct choice.

Option A is incorrect because during periods without food, the body needs to use stored fat as an energy source, so the release of fatty acids from adipose tissue would actually increase, not decrease. Option B is incorrect because gluconeogenesis (the production of glucose from non-carbohydrate sources) would increase during periods without food to maintain blood glucose levels. Option C is incorrect because in the absence of glucose, the liver starts producing ketone bodies as an alternative energy source, so ketogenesis would actually increase, not decrease.

Question 2

Neuronal samples from wild-type mice were monitored in the absence and presence of leptin via Western blotting.The data are shown below.Choose the answer that correctly identifies the NPY/AGRP neuronal samples obtained in the absence and then the presence of leptin.

Accepted Answer

The answer of Neuronal samples from wild-type mice were monitored...

Question 3

The set point can be increased as a result of

Accepted Answer

A sedentary lifestyle can lead to a decrease in metabolic rate, which can cause the body to increase its set point in order to conserve energy.

Question 4

PPARs have a variety of functions in lipid metabolism that include all EXCEPT

Accepted Answer

PPARs do not decrease insulin sensitivity, in fact, they have been shown to have insulin-sensitizing properties.

Question 5

What might occur if a mutation in the leptin receptor causes it to be always activated,even in the absence of leptin?

Accepted Answer

The answer of What might occur if a mutation in...

Question 6

Leptin is a

Accepted Answer

Leptin is an adipocyte peptide hormone that plays a key role in regulating energy balance, appetite, and metabolism. It is mainly produced by adipose tissue and acts on the hypothalamus in the brain to reduce food intake and increase energy expenditure. Leptin deficiency or resistance can lead to obesity and metabolic disorders.

Question 7

During periods of starvation,gluconeogenesis increases in the liver.Which of the following is a major substrate for glucose biosynthesis under these conditions?

Accepted Answer

During periods of starvation, the body begins to break down muscle tissue to produce amino acids, primarily alanine. Alanine is then transported to the liver where it is converted to glucose through gluconeogenesis. Therefore, alanine is a major substrate for glucose biosynthesis during starvation. Glutamate and urea are not major substrates for gluconeogenesis, and fatty acids are mainly used for energy production in tissues such as muscle and adipose tissue.

Question 8

A lack of energy balance may lead to

Accepted Answer

A lack of energy balance, specifically, consuming more calories than the body needs, is a major risk factor for the development of type 2 diabetes. Type 1 diabetes is an autoimmune disease that is not caused by a lack of energy balance, while a BMI value of less than 30 actually indicates a healthy weight or even underweight status, not obesity. Increased skeletal muscle breakdown may occur for various reasons, but is not directly related to an energy imbalance.

Question 9

The graph below shows the relative changes in concentration of glucose,fatty acids,and ketone bodies during 40 days of starvation.Choose the answer that correctly labels the data on the graph.

Accepted Answer

The graph shows that during 40 days of starvation, the concentration of glucose decreases rapidly while the concentration of ketone bodies increases. This is indicative of the body shifting from glucose as its primary energy source to utilizing ketone bodies. The concentration of fatty acids also increases, but not as rapidly as ketone bodies. Therefore, X = ketone bodies, Y = glucose, and Z = fatty acids.

Question 10

Which of the following neurons is a second-order neuron and therefore does NOT respond directly to leptin?

Accepted Answer

Orexigenic neurons are second-order neurons that do not directly respond to leptin. They are influenced by first-order neurons like NPY and AGRP, which do respond to leptin.

Question 11

The average amount of adipose tissue the body maintains at physiological homeostasis is known as the

Accepted Answer

The average amount of adipose tissue that the body maintains at physiological homeostasis is known as the set point. This is the point at which the body weight and fat mass are maintained despite changes in energy intake and expenditure. Energy balance refers to the equilibrium between energy intake and energy expenditure. Adipose energy balance is a term that is not commonly used in physiology, and BMI (body mass index) is a measure of body fat based on height and weight, but it does not reflect the body's physiological regulation of fat mass.

Question 12

Which of the following is NOT one of the three peroxisome proliferator-activated receptor nuclear receptor proteins that function in metabolic homeostasis?

Accepted Answer

The answer of Which of the following is NOT one...

Question 13

Thrifty genes are __________ during times of starvation and __________ when physical activity is low.

Accepted Answer

Thrifty genes are beneficial during times of starvation as they promote fat storage and energy conservation, but detrimental when physical activity is low because they can lead to obesity and related health issues.

Question 14

Enzyme activities after PPAR signaling were monitored in both liver and skeletal muscle.When compared with activities before PPAR signaling,which of the following would have been found to increase in liver but NOT in skeletal muscle?

Accepted Answer

Transketolase is involved in the pentose phosphate pathway, which is more active in the liver due to its role in biosynthesis and detoxification processes. PPAR signaling enhances this pathway in the liver but not in skeletal muscle.

Question 15

When basal metabolic rates are decreased and appetite is increased,which type of neurons are likely activated?

Accepted Answer

When basal metabolic rates are decreased and appetite is increased, orexigenic neurons are likely to be activated. These neurons produce the hunger-stimulating hormone ghrelin which increases appetite and food intake. Anorexigenic neurons on the other hand, suppress appetite and food intake. POMC is a precursor protein that plays a role in regulating energy balance and metabolism but does not directly activate or suppress appetite.

Question 16

The net effect of leptin signaling in humans includes

Accepted Answer

Leptin signaling in humans results in decreased appetite, as it signals to the brain that enough energy has been taken in and the body no longer needs to consume food. It does not lead to decreased basal metabolic rates or increased set point, and its effects on thrifty gene expression are still being studied.

Question 17

Analysis of enzyme activity in both liver and muscle cells on insulin exposure would show a decrease in the activity of

Accepted Answer

Insulin decreases the activity of glycogen phosphorylase, which is responsible for the breakdown of glycogen into glucose-1-phosphate.

Question 18

DB mice display the __________ phenotype and express __________ leptin levels when compared with OB mice.

Accepted Answer

The answer of DB mice display the __________ phenotype and...

Question 19

Analysis of enzyme activity in both liver and muscle cells on insulin exposure would show an increase in the activity of which of the following?

Accepted Answer

The answer of Analysis of enzyme activity in both liver...

Question 20

Human gene variants favoring individuals with a capacity to store extra fat during times of feast are known as

Accepted Answer

The human gene variants that favor individuals with the ability to store extra fat during times of feast are known as thrifty genes. These genes were thought to have evolved in response to periods of feast and famine during human evolution. Individuals with these genes were better able to survive during times of food scarcity by storing excess calories as fat. However, in modern times, with a constant abundance of food, these genes have contributed to the rise of obesity and related health problems.

Quiz 19: Metabolic Integration