Question 1

Ketone bodies are produced in the kidneys,and since they are small molecules that can hydrogen bond with water,they are readily soluble in blood and urine.

Accepted Answer

Ketone bodies are primarily produced in the liver, not the kidneys, although they are indeed soluble in blood and urine due to their ability to hydrogen bond with water.

Question 2

A glucogenic amino acid may also be a ketogenic amino acid.

Accepted Answer

Some amino acids can be both glucogenic and ketogenic, meaning they can be converted into glucose as well as ketone bodies. Examples include isoleucine, phenylalanine, threonine, tryptophan, and tyrosine.

Question 3

The overall result of transamination and oxidative deamination is to remove an amino group from an amino acid and form an ammonium ion,NH₄⁺.

Accepted Answer

Transamination transfers an amino group from an amino acid to an α-keto acid, and oxidative deamination removes an amino group from an amino acid, converting it into an ammonium ion.

Question 4

The breakdown of amino acids forms NH₄⁺,which enters the urea cycle to form urea,and a carbon skeleton that is metabolized to either pyruvate,acetyl CoA,or an intermediate in the citric acid cycle.

Accepted Answer

The breakdown of amino acids involves deamination, where the amino group is removed. This amino group is converted into ammonia, which then enters the urea cycle to form urea. The remaining carbon skeleton of the amino acid can indeed be metabolized into pyruvate, acetyl CoA, or an intermediate in the citric acid cycle, depending on the specific amino acid. This process is crucial for energy production and the disposal of nitrogen waste in the body.

Question 5

Transamination removes the amino group from an amino acid,leaving a carbon skeleton that contains only carbon,hydrogen,and oxygen atoms.

Accepted Answer

Transamination involves the transfer of an amino group from an amino acid to a keto acid, resulting in the formation of a new amino acid and a new keto acid. The original amino acid is left as a carbon skeleton that typically contains only carbon, hydrogen, and oxygen atoms.

Question 6

In oxidative deamination,glutamate is re-converted to α-ketoglutarate,which can undergo transamination with another molecule of an amino acid and the cycle repeats.

Accepted Answer

In oxidative deamination, glutamate is indeed converted back to α-ketoglutarate, which can then participate in transamination reactions with other amino acids, allowing the cycle of amino acid deamination and transamination to continue. This process is crucial for the removal of amino groups from amino acids and their eventual excretion from the body in a less toxic form, such as urea.

Question 7

Ketogenesis is the synthesis of ketone bodies from acetyl CoA.

Accepted Answer

Ketogenesis is the metabolic process by which ketone bodies are produced as a result of fatty acid breakdown. This process occurs primarily in the liver mitochondria where acetyl CoA is converted into ketone bodies, including acetoacetate, β-hydroxybutyrate, and acetone, which can be used as alternative energy sources by various tissues, including the brain, during periods of low glucose availability.

Question 8

Gluconeogenesis is simply the reverse of glycolysis.

Accepted Answer

Gluconeogenesis involves the generation of glucose from non-carbohydrate precursors, and while it shares some steps with glycolysis, it is not simply the reverse. It includes unique steps and enzymes to bypass the irreversible steps of glycolysis.

Question 9

Catabolism of a fatty acid produces more than twice the energy per gram as glucose (in terms of moles of ATP generated).

Accepted Answer

Fatty acid catabolism generates more ATP per gram than glucose because fats are more reduced than carbohydrates, allowing for more energy to be extracted during their oxidation.

Question 10

Glycolysis occurs when the body has depleted its supplies of glucose and stored glycogen,and occurs during sustained physical exercise and fasting.

Accepted Answer

Glycolysis is the process of breaking down glucose for energy and occurs regardless of the body's supplies of glucose and glycogen. It is a primary metabolic pathway for energy production that happens continuously, not only during sustained physical exercise and fasting.

Question 11

Step [1] of the β-oxidation of a fatty acid is considered an oxidation reaction even though the product has no additional C-O bonds.

Accepted Answer

The first step of β-oxidation involves the removal of hydrogen atoms (dehydrogenation) from the fatty acid, which is a type of oxidation reaction, even though it does not directly result in the formation of C-O bonds.

Question 12

The major products of glycolysis are glucose and ATP.

Accepted Answer

The major products of glycolysis are pyruvate, ATP, and NADH; glucose is the substrate, not a product.

Question 13

Low carbohydrate diets such as the Atkins diet induce the catabolism of stored fat for energy production to assist in weight loss.

Accepted Answer

Low carbohydrate diets like the Atkins diet reduce the intake of carbohydrates, leading the body to break down stored fat for energy, a process known as ketosis, which assists in weight loss.

Question 14

An abnormally high concentration of ketone bodies can lead to ketoacidosis-that is,an increase in the blood pH caused by the increased level of β-hydroxybutyrate and acetoacetate.

Accepted Answer

Ketoacidosis leads to a decrease in blood pH due to the increased level of β-hydroxybutyrate and acetoacetate, which are acidic.

Question 15

In fermentation,the six carbon atoms of glucose are converted to three molecules of ethanol.

Accepted Answer

In fermentation, one molecule of glucose (six carbon atoms) is typically converted into two molecules of ethanol and two molecules of carbon dioxide, not three molecules of ethanol.

Question 16

When acetyl CoA levels exceed the capacity of the citric acid cycle,acetyl CoA is converted to ketone bodies.

Accepted Answer

When acetyl CoA levels exceed the capacity of the citric acid cycle, such as during periods of high fat oxidation or low carbohydrate availability, acetyl CoA is diverted to the production of ketone bodies in the liver. This process provides an alternative energy source for tissues like the brain.

Question 17

The urea cycle is a multistep pathway that converts ammonium ions to urea,(NH₂)₂C=O,in the kidneys.

Accepted Answer

The urea cycle occurs in the liver, not the kidneys, and is responsible for converting ammonia to urea for excretion.

Question 18

The rate of glycolysis decreases when the body's ATP concentration is high.

Accepted Answer

Glycolysis is regulated by feedback inhibition, where high levels of ATP inhibit the activity of key enzymes in the pathway, thus decreasing the rate of glycolysis when energy (ATP) is abundant.

Question 19

When oxygen is plentiful,pyruvate is converted to acetyl CoA,which can enter the citric acid cycle.

Accepted Answer

When oxygen is available, pyruvate is transported into the mitochondria where it is converted into acetyl CoA. Acetyl CoA then enters the citric acid cycle (also known as the Krebs cycle or TCA cycle) to be broken down for energy production.

Question 20

The products that result when alanine is subjected to transamination followed by oxidative deamination are properly indicated below.

Accepted Answer

The answer of The products that result when alanine is...

Quiz 24: Carbohydrate,lipid,and Protein Metabolism