Introduction to Nutrition Chapter 8
If you are concerned about your drinking or that of a friend or relative you can contact:
National Drug and Alcohol Treatment Referral Routing Service, 1-800-662-HELP. Alcoholics Anonymous Substance Abuse and Mental Health Services Administration, Al-Anon/Alateen, for families and friends of alcoholics and alcohol abusers
When adequate oxygen is present in a cell, mitochondria can make lots of ATP (aerobic metabolism).....
When the cell's oxygen supply is inadequate to support the functioning of mitochondria. the cell can obtain ATP by using a pathway that does not require oxygen (anaerobic metabolism).
Furthermore, women take longer to metabolize alcohol than men. Thus, a woman who drinks the same...
amount of alcohol as a man will have a higher BAC 1 hour after consuming the alcohol.
This chemical difference explains why an ounce of pure fat provides more energy than...
an ounce of pure carbohydrate. Although fatty acids have the potential to yield larger amounts of energy than glucose, human cells cannot metabolize them to make glucose.
Side effects of a ketogenic diet may include....
constipation, hypoglycemia, hunger, vomiting, lack of energy, elevated blood lipids, and kidney stones.
As a result, abnormal glucose metabolism occurs in all cases of GSD. Signs and symptoms of the...
disorder include hypoglycemia (low blood glucose), fatigue, irritability, and liver and kidney enlargement
Thus, insulin helps maintain normal blood glucose levels by...
enabling the entry of glucose into many kinds of cells
Once alcohol enters liver cells, the normal metabolic processing of glucose....
fatty acids and amino acids slows down, and the catabolism of alcohol becomes the cell's top priority.
If a person with a fatty liver contineus to consume alcohol, he or she eventually is...
likely to develop cirrhosis of the liver, which permanently damages the liver.
In the first step of this process, most of the alcohol is converted to...
acetyldehyde, a highly toxic substance. However, the enzyme aldehyde dehydrogenase helps convert acetaldehyde to acetate, a less toxic substance.
When certain cells, such as a muscle cell, need ATP, they can take up fatty acids from the bloodstream. Fatty....
acids undergo catabolism in the mitochondria. While these lipids are still in the cell's cytoplasm they are prepared for catabolism "activated" by binding to coenzyme A. The activation process require energy from two ATP.
Caffeine is a stimulant drug because it increases the...
activity of the nervous system. The drug, however, can cause unpleasant side effects, including anxiety, restlessness, tremors, rapid heart rate, and sleep disturbances.
When glucose is unavailable (such as during starvation), most cells even brain cells can....
adapt to the altered metabolic state and catabolize acetoacetate and beta-hydroxybutyrate for energy.
Alcohol affects every in the body, and when consumed in excess, the...
drug damages every system in the body, particularly the gastrointestinal, nervous, and cardiovascular systems.
Thus, thyroid hormone levels increase during times of growth and development. When food is not available, such as...
during periods of starvation, thyroid hormone production decreases. This response is important because it helps conserve the body's fuel stores.
Insulin resistance in muscle cells and adipocytes occurs because the...
insulin receptors no longer function properly. Thus, obesity is highly associated with insulin resistance, a condition that can lead to type 2 diabetes
Muscle cells lack the enzyme that is required for the final step in glycogenolysis, which prepares an....
intermediate form of glucose for release into the bloodstream.
Glucose, fat and amino acids work together to fuel the body under a variety of physical conditions. Understanding how the pathways and actions of the metabolic hormones are...
interrelated will help you recognize what can happen to the body's nutritional status during disease states.
This process helps maintain blood glucose levels within normal limits, but the...
supply of liver glycogen is limited and becomes depleted over the course of about 12 hours.
When cells have adequate amounts of ATP available and more fuel molecules than necessary...
to meet their immediate needs, these extra sources of energy are stored, rather than catabolized.
A current drinker consumed at least one alcohol-containing drink in the 30 days prior to the survey. In 2015...
6.5% of Americans who were 12 years of age or older were heavy drinkers.
The fatty acids that are typically in foods contain more carbon atoms than the...
6 carbon glucose molecule, so fatty acids have the potential to form more acetyl CoA, NADH, and FADH2 molecules during their catabolism than glucose.
Step 4 of the citric acid cycle:
During the next series of reactions, one ATP forms from GTP (a related compound), and the four carbon intermediates release hydrogen ions that are picked up by FAD and NAD+.
The steps by which the electron transport chain produces water and ATP during aerobic energy metabolism: Step 1
Electrons (e-) from the hydrogen ions are passed through the chain that includes the iron-containing cytochromes
FAD can pick up two hydrogen ions along with two electrons. When this reaction occurs....
FAD becomes FADH2. NAD+ and FAD shuttle hydrogen ions and electrons to a place within cells where their energy can be extracted
The 3 major events that occur in the complete breakdown of glucose that results in the production of CO2, H2O, and ATP:
Glycolysis, Citric acid cycle, ETC
Step 3 of the ETC:
Most important, some of the energy released during the electron transfer is used to bind a Pi group to ADP, forming ATP.
The glycerol and fatty acid molecule exit adipocytes and enter the bloodstream. The fatty acids binds to...
albumin, a protein that is water soluble and serves as a carrier molecule. Once bound to albumin, the fatty acid circulates to tissues, where it can be picked up and used for energy.
The chemical pathway that initiates the breakdown of glucose and produces some ATP occurs in the cytoplasm. Mitochondria are...
are organelles that synthesize most of the ATP that cells need to function. Are the "powerhouses" inside of cells that catabolize macronutrients and transfer the energy released from these molecules to ATP.
If a person's diet does not supply adequate amounts of these vitamins, his or her cells will...
be unable to synthesize the coenzymes necessary catabolism. When this occurs, cells cannot convert enough pyruvate into acetyl CoA to meet their needs.
Most of the energy released by the breakdown of macronutrients is....
captured in chemical form as adenosine triphosphate (ATP). ATP is a high energy phosphate compound. When an enzyme "cleaves" (breaks) the bond between the last two phosphate groups of ATP, the high-energy molecule loses some of its power.
Under normal conditions, human cells, rely heavily on glucose to function properly. Cells in the...
central nervous system (CNS) are highly dependent on glucose, rather than fatty acids or amino acids , to meet their energy needs.
The acetyl CoA molecules that form during beta-oxidation enter the...
citric acid cycle and are catabolized to produce ATP. Furthermore, the NADH and FADH2 molecules that result from beta-oxidation and the citric acid shuttle energy-containing ions to the electron transport chain to generate even more ATP.
During certain catabolic processes, macronutrient molecules release hydrogen ions (H+) that...
contain high-energy electrons (e-). Two different coenzymes accept and transport the ions.
Although caffeine increases alertness, the compound does not provide any energy (calories). Simply consuming an energy drink that..
contains caffeine and other naturally occurring stimulants may reduce feelings of fatigue, but it will not lead to having more energy.
In addition to caffeine, energy drinks may contain B vitamins and other dietary supplements, including taurine, a...
derivative of the amino acid cysteine, and guarana, an herbal product.
During this process, two NADH and four ATP molecules form. Several steps in the glycolytic pathway can...
flow in either direction. In most cells, however, pyruvate cannot be used to re-form glucose because the cells lack the unique set of enzymes that are required for reversing the glycolytic pathway.
Acetyl coenzyme A is often referred to simply as "acetyl CoA". Because glycolysis resulted in the...
formation of two pyruvate molecules, two molecules of acetyl CoA can be formed from one molecule of glucose
By substracting the two ATP needed to spark glycolysis from the...
four ATP that are formed, the cell gains only two ATP ( 4 ATP produced- 2ATP used = 2 ATP gained). Thus, glycolysis does not provide much ATP.
When the body need energy but its cell do not have a direct source of...
glucose readily available, the cells can obtain the monosaccharide by glycogenolysis, the breakdown of glycogen into glucose molecules.
To access and use the energy stored in "biological fuels" such as...
glucose, cells utilize specific chemical reactions that occur in sequence called chemical pathways.
Anabolic reactions include building glycogen from glucose molecules, triglycerides from...
glycerol and free fatty acids, and proteins from amino acids.
Over the past few years, consumption of energy drinks that contain has...
grown in the US, especially among teens and young adults.
Some individuals are born with a form of glycogen storage disease (GSD), an inborn error of metabolism. Each form of...
gsd results from a defect that relates to an enzyme involved in carbohydrate metabolism.
Chemical energy, for example, can change into...
heat energy, which explains why a car's engine heats up as it burns gasoline and muscles warm up during exercise.
Heat comprises some of the energy that is released: "Heat of metabolism"...
helps the body maintain its normal temperature. Cells use the remaining energy to power chemical reactions.
In muscle tissue, glycogenolysis releases glucose molecules, but the glucose is...
in an intermediate form that cannot leave the muscle cells.
An inborn error of metabolism is an inherited metabolic defect. There are many kinds of..
inborn errors metabolism, including phenylketonuria and homocysteinuria.
Energy metabolism
involves the chemical pathways that enable the human body to obtain and use energy from macronutrients and alcohol
These particular coenzymes have forms of the B vitamins niacin or riboflavin in their chemical structures. Niacin is...
is a component of the coenzyme nicotinamide adenine dinucleotide (FAD).
Energy
is the capacity to perform work. Energy has many forms, including chemical, mechanical, electrical, heat, solar, and nuclear energy.
Metabolism
is the sum of all chemical reactions that occur in living cells, including the reactions that release energy from biological fuels, synthesize proteins, and eliminate waste products. Can be catabolic or anabolic.
The Cori cycle is an energy-requiring pathway in that...
it requires the energy of six ATP to make glucose from lactate. Therefore, the Cori cycle is too inefficient to continue indefinitely.
Catabolic reactions are considered "downhill" because they result in the release of...
more energy than is used to initiate the reactions.
Human cells use pyruvate in two major ways, depending on the availability of oxygen. When the body has access to plenty of oxygen, the....
pyruvate molecules enter mitochondria. Within a mitochondrion, pyruvate undergoes conversion into a two-carbon compound, acetyl coenzyme A.
Having an adequate supply of glucose for energy is important because....
red blood cells, the brain, and the nervous system rely predominately on glucose as a fuel source.
Catabolism
refers to metabolic pathways that break down larger molecules into smaller ones. Examples: breakdown of glucose, fatty acid, and amino acid molecules to form carbon dioxide and water.
Most chemical reactions that occur in living cells require specific enzymes that facilitate (catalyze) the reactions, but...
the enzymes remain unchanged as a result of the process. Reactions involved in metabolic pathways also require the activity of specific enzymes.
After activation, fatty acids must pass through the outer and inner mitochondrial membranes with...
the help of a molecule called carnitine.
Triglycerides are the most energy dense, and...
the human body stores more energy in fat cells than in its glycogen stores.
The first phase glucose catabolism occurs in a series of chemical reactions called. glycolysis. Glycolysis ultimately leads to ATP production from...
the oxidation of glucose. Oxidation involves the loss of electrons during chemical reactions. In many instances, oxygen participates in oxidative reactions by chemically combining with a substance
Acetyl CoA is a key molecule in metabolism. The oxidation of acetyl CoA is.....
the second phase of glucose catabolism. When cells need energy, acetyl CoA enters the citric acid cycle. The citric acid cycle is a complex series of chemical reactions that converts the two-carbon acetyl CoA molecules into CO2 and H2O molecules.
ATP yields for each NADH and each FADH2 that enter the electron transport chain are not precisely know. Biochemists estimate...
the values to be approximately 2.5 ATP for NADH and 1.5 for FADH2. The complete catabolism of one glucose molecule yields approximately 30 to 32 molecules of ATP
If glucose is unavailable, however, most cells are resourceful in that...
they can metabolize more than one fuel for energy. Although we focus on glucose catabolism, cells can also use fructose and galactose to synthesize ATP, particularly in the liver.
Coenzymes that contain the B vitamins.....
thiamin, riboflavin, niacin, pantothenic acid, and vitamin B-6 participate in several of the reactions that release energy macronutrients.
Under anaerobic conditions, each molecule of pyruvate converts to latic acid, another three-carbon molecule. Lactic acid releases...
two H+, forming lactate as a result. Cells, especially vigorously contracting muscles, release lactate into the bloodstream.
As of 2015, the U.S. Food and Drug Administration (FDA) was aware of...
two deaths that were linked to overdoses of caffeine.
The NADH and FADH2 that result from beta-oxidation yield about four ATP. To illustrate what happens...
we will use palmitic acid, a saturated fatty acid with 16 carbon atoms. After entering a mitochondrion, enzymes cleave the activated palmitic acid molecule repeatedly into 2 carbon segments.
Common symptoms of these deficiencies include "lack of energy" (fatigue) and...
weakness because cells are unable to metabolize macronutrients for energy.
The major events that occur in the complete oxidation of fatty acids that result in the production of CO2, H20, and ATP: (4)
Acetyl CoA molecules enter the citric acid cycle and undergo catabolism for ATP production. NADH and FADH2 transfer electrons to the electrons are accepted by oxygen, producing water and releasing energy for the synthesis of ATP.
When sleeping, your cells make...
ATP by breaking down triglycerides stored in adipocytes and the glucose derived primarily from glycogen stored in liver and muscle cells.
Phosphorylation reactions, however, require the input of some energy. The recycling of...
ATP from ADP and Pi is essential for meeting the energy demands of cells. The catabolism of macronutrients ( and alcohol) supplies energy to produce ATP.
Epinephrine
Catabolic, Increases glycogenolysis and gluconeogenesis, Increases lipolysis
Glucagon
Catabolic, increases glycogenolysis and gluconegenesis
Step 2 of Citric Acid Cycle:
Citrate is converted to an intermediate compound that undergoes oxidation and loses a carbon atom in the form of CO2. NAD+ becomes NADH, and the five-carbon intermediate molecule, alpha-ketoglutarate, forms.
The major events that occur in the complete oxidation of fatty acids that result in the production of CO2, H20, and ATP: (1)
Hormone sensitive lipase facilitates the removal of three fatty acids from the glycerol "backbone" of a triglyceride molecule. The free fatty acids enter the bloodstream and bind to albumin for transport to cells, particularly muscle cells. After being transported to muscle tissues, fatty acids are released from albumin and enter the muscle cell.
The major events that occur in the complete oxidation of fatty acids that result in the production of CO2, H20, and ATP: (2)
In the cell's cytoplasm, a fatty acid binds to coenzyme A, forming an activated fatty acid. Carnitine shuttles the activated fatty acid into the region of the mitochondrion where beta-oxidation beta-oxidation occurs.
The major events that occur in the complete oxidation of fatty acids that result in the production of CO2, H20, and ATP: (3)
In the mitochondrion, the activated fatty acid is catabolized by beta-oxidation. During beta-oxidation, the fatty acid molecule is cleaved into 2 carbon segments that are converted into acetyl CoA. Each cleavage reaction produces one NADH and one FADH2 molecule.
Cortisol
Increases glycogenolysis and gluconeogenesis, increases lipolysis, and increases proteolysis
Thyroid hormone
Regulates metabolic rate
Citric acid cycle:
The 2 acetyl CoA molecules formed in the previous step undergo conversion in the citric acid cycle, combining with oxaloacetate. During the cycle, intermediates form: NAD+ and FAD pick up hydrogen ions and their electrons to become NADH and FADH2, and more CO2 is released. Each molecule of acetyl CoA that enters the cycle result in one molecule of ATP.
Glycolysis:
Under aerobic conditions, a 6 carbon glucose molecule undergoes glycolysis, forming 2 to 3 carbon pyruvate molecules in the cytoplasm. Two ATP molecules are utilized, and 4 ATP molecules are formed in the process, for a net gain of 2 ATP.
When a person drinks an alcohol-containing beverage, his or her stomach and small intestine rapidly absorb the drug. When alcohol is consumed with meals, food delays its...
absorption from the stomach and slows the rate at which substance enters the bloodstream.
In patients with poorly controlled diabetes mellitus, glucose cannot enter cells and...
be converted to pyruvate. Because of the lack of pyruvate, cells catabolize more fat for energy, and acetyl CoA molecules accumulate.
Actions of each metabolic hormone depends on the body's metabolic state, which...
can be categorized as either absorptive (when the digestive tract is not active).
Ketogenic amino acids, such as leucine and tryptophan, have carbon skeletons that...
can be converted into acetyl CoA. Ketogenic amino acids cannot be used to make glucose because the step that converts pyruvate to acetyl CoA is not reversible.
Compared to aerobic metabolism , however, the amount of...
energy made under low-oxygen conditions is much less
In contrast, the intestinal tract absorbs alcohol faster when it is...
in carbonated beverages, such as beer, "sparkling" wines, and drinks made by mixing carbonated soft drinks with liquor.
Insulin directs liver and muscle cells to slow down their glycogenolysis rates and...
increase their rates of glycogenesis. Such actions shift glucose molecules into storage as glycogen. Insulin also increases the fatty acid uptake and triglyceride synthesis of adipocytes.
If a person consumes excessive amounts of alcohol in one session, such as during a drinking binge, the...
liver's ability to metabolize the drug using the alcohol dehydrogenase pathway is overwhelmed. When this occurs, a secondary pathway for processing alcohol, the microsomal ethanol-oxidizing system (MEOS), takes over.
The vicious cycle results in metabolic syndrome. Having excess body fat is a...
major risk factor for developing metabolic syndrome and type 2 diabetes. Thus, people can reduce their risk of both conditions by keeping their weight within a normal range.
The rate of glycolysis slows because the glycolytic pathway requires NAD+ to...
metabolize glucose molecules. When NADH accumulates in liver cells, more pyruvate is converted to lactic acid. Because of these changes, ATP production from glucose is impaired.
When glucose enters cells that need energy, the...
monosaccharide undergoes glycolysis and is rapidly catabolized for ATP production.
The cells of a person with GSD are unable to synthesize one or more of the enzymes needed to....
or degrade glycogen properly. Thus, the person's muscle and/or liver cells may store improperly formed glycogen or abnormal amounts of the polysaccharide, depending on the type of GSD
Anabolism
refers to metabolic pathways that build larger molecules from smaller ones.
Respiration in the lungs and perspiration from the skin eliminate a small percentage of the alcohol; that is why you can...
smell alcohol when you are around someone who has been drinking.
The process of glycogenesis involves the help of...
specific enzymes that bind single glucose molecules together into long branched chains of glycogen.
The body stores limited amounts of glycogen, and...
storage sites can fill up quickly.
The body is also able to store excess energy for future use, primarily in...
two forms (fat and glycogen). The availability of ATP in your cells determines the fate of the macronutrient molecules that you consume in your next meal or snack .
Although these metabolic responses are necessary for survival, the starving person is in a...
very dangerous metabolic states and will likely die if the lack of access to nourishing foods continues.
The adrenal glands also produce epinephrine, commonly called...
"adrenaline." Epinephrine stimulates catabolism by increasing glycogenolysis in the liver and muscle, as well as by increasing triglyceride breakdown (lipolysis) in adipose tissue.
The breath of a person with ketoacidosis with ketoacidosis typically has....
"fruity" or acetone odor. If untreated, ketoacidosis can lead to coma (loss of consciousness) and death. Proper management of diabetes, including regular testing of blood glucose levels, is crucial for preventing ketoacidosis.
Insulin
-anabolic, increases glycolysis and glycogenesis, increases glucose and amino acid uptake and glycogenesis and protein synthesis.
A standard drink (approximately 12 ounces of beer, 5 ounces of wine, or 1 1/2 ounces of liquor) contains ...
13 to 14 grams of alcohol
Moreover, coma and even death can occur as the brain loses control over lung and heart functioning. According to results of a national study conducted in 2015...
52% of people who were 12 years of age or older in the US were current drinkers of alcohol.
The primary result of glucagon's activity is an increase in blood glucose levels. Cortisol is...
a catabolic hormone made in the adrenal cortex of the adrenal glands, which are located on the top of the kidneys.
Alcohol poisoning can cause the heartbeat to slow down and the lungs to stop functioning, resulting in death. Additionally, if...
a comatose person vomits, his or her stomach contents can enter their lungs, causing the person to choke to death.
Binge drinking increases a person's blood alcohol concentrations rapidly and to...
a point at which signs of alcohol. An individual suffering form alcohol poisoning is confused, passes out and cannot be aroused (camatose), breathes slowly and irregularly, and has pale or blueish skin.
Another fuel that the body can use for energy is ethanol...
a simple two-carbon molecule that is more commonly called "alcohol". Alcohol is soluble in water, and alcoholic beverages generally contain a considerable amount of water.
This enzyme cleaves the three fatty acids from the glycerol backbone of...
a triglyceride molecule in lipoproteins. As a result, the free fatty acids and glycerol can enter cells.
After the liver releases VLDL into the bloodstream, adipocytes and other cells can...
access the lipoproteins' lipid contents, particularly fatty acids, through the action of lipoprotein lipase.
In the liver, the influx of fatty acids stimulates triglyceride synthesis. The excess fat can...
accumulate in liver cells and lead to a condition called nonalcoholic fatty liver.
Under normal conditions, liver cells convert small amounts of acetyl CoA to...
acetoacetate, beta-hydroxybutyrate, and acetone. These compounds, collectively referred to as ketone bodies , are released into the bloodstream. Ketone body formation is called ketogenesis.
Acetone is toxic to cells, but the lungs remove the compound by exhaling it. If excessive amounts of...
acetone are exhaled, the breath has an unusual "fruity" odor. Cells, excluding liver cells, can use acetoacetate and beta-hydroxybutyrate as sources of acetyl CoA.
Several physiological factors account for the variability. Besides the amount and timing of...
alcohol consumption, personal characteristics such as sex, body size and composition, age, and prior drinking history affect a person's detoxification rate
When a person drinks low to moderate amounts of alcohol, the liver relies primarily on the...
alcohol dehydrogenase pathway to metabolize the drug.
Although each gram of alcohol can be metabolized for energy and provides 7 kcal...
alcohol is not a nutrient; it is a mind-altering, toxic drug. When consumed in excess, alcohol can damage every organ of the body and lead to death.
As you can see, the human body is an...
amazing living machine that obtains energy from a variety of sources and extracts the energy in many ways.
As mentioned earlier, cells preferentially use...
amino acids and cells do not need energy
Although your body's proteins are abundant sources of...
amino acids, protein rich-tissues are not normally broken down and catabolized for energy.
A moderate drinker with a healthy liver can metabolize about 12 to 15 g of alcohol per hour. This amount is...
approximately the alcohol content of a standard drink. If the drinker consumes more than one standard drink/hour, the excess alcohol circulates in his or her bloodstream until liver cells are able to metabolize it.
A "problem drinker" experiences problems at home, work, and school that are...
associated with his or her drinking habits. According to the experts with the National Institutes of Health, a person with a severe drinking problem has an alcohol abuse disorder (AUD).
During starvation, however, muscle cells experience a severe change: They...
begin to break down and release amino acids. This degradation process is called proteolysis. The liver can use some of the amino acids for gluconeogenesis. Nevertheless, the body relies more heavily on stored fat than protein for energy during prolonged starvation.
Youthful binge drinking is a serious public health concern because the...
behavior is often associated with driving while drunk. Furthermore, the practice may increase a person's later risk of alcoholism and can result in death.
After carbohydrate-containing meal, the beta cells detect the rise in...
blood glucose levels (absorptive state) and secrete insulin.
High concentrations of the ketone bodies in the bloodstream lower the...
blood's pH and cause severe ketosis, which is called ketoacidosis.
Unlike the alcohol dehydrogenase pathway, the MEOS wastes energy in the form of...
body heat. Thus, alcohol-dependent people (alcoholics) may gain little weight from their energy intake, particularly when alcohol supplies most of their energy.
In a series of repeating sequential reactions, two-carbon acetyl CoA units are...
bound together form the hydrocarbon chain of the fatty acid. With each addition of a acetyl CoA molecule, the fatty acid elongates and stores energy.
Under these conditions, ketogenesis occurs at a rapid pace, and....
cells cannot oxidize acetoacetate and beta-hydroxybutyrate fast enough to maintain normal blood chemistry.
In cases of obesity, the increase in adipose tissue often results in abnormal metabolic changes in fat and muscle cells. These changes make the...
cells resistant or unresponsive to the effects of insulin.
Pregnant women who drink alcohol can cause irreversible damage to their unborn offspring. Alcohol's effects on the....
central nervous system, especially the brain, appear within a few minutes of having a drink. Alcohol acts as a depressant, slowing the transmission of messages between nerve cells.
Certain cells make fatty acids (lipogenesis). The synthesis of a fatty acid requires different enzymes and...
chemical pathways than the oxidation of a fatty acid.
The thyroid gland at the base of the throat synthesizes and secretes two hormones that are...
collectively referred to as thyroid hormone. This hormone helps the body adapt to different situations by increasing or decreasing the rate of metabolism.
The complete oxidation of a palmitic acid molecule yields a net of 106 ATP. In comparison, the...
complete catabolism of a glucose molecule yields only about 30 to 32 ATP.
Normally, cells synthesize oxaloacetate from pyruvate that is...
derived from glycolysis/ Thus, a "spark" from a carbohydrate "match" helps burn fat for energy. If cells do not have enough pyruvate to make oxaloacetate for citric acid cycle, acetyl CoA molecules that result from beta-oxidation accumulate.
While following a ketogenic diet, children with epilepsy need close medical supervision and monitoring to...
determine whether the diet is safe and effective and should be maintained for more than a few months.
To reduce alcohol's harmful effects, the body detoxifies the simple molecule by converting it into less damaging compounds. If alcohol mixes with food in the stomach, some...
detoxification of the drug occurs by the action of gastric alcohol that has been absorbed by the digestive tract.
Men and women have different physical responses to alcohol because of...
differences in body size and composition, as well as difference in metabolism.
To avoid ketosis, the average person needs to consume 100 g of...
digestible carbohydrates per day. Healthcare providers may use low-calorie, ketogenic diets to treat children and adults with eilepsy, particularly in cases that do not respond well to medication.
If the diet provides an excess of amino acids and cells...
do not need energy, the amino acids will be stripped of their nitrogen group and used to make either glucose or fat.
Because of the lack of NAD+, the activity of the citric acid cycle slows. Some of the acetyl CoA molecules...
enter the citric acid cycle and are catabolized for energy. However, the liver cells use most of the excess acetyl CoA molecules to make fatty acids for triglyceride synthesis. The accumulation of triglycerides in liver cells can cause "alcoholic fatty liver".
Patients with epilepsy have abnormal brain functioning that causes seizures. Some people who have...
epilepsy are less likely to have seizures when they follow a low-calories, very-low carbohydrate diet, but scientists do not fully understand why ketosis is beneficial in these cases.
As a result of lipolysis, more fatty acids and glycerol molecules become available for catabolism. Adrenal glands secrete large amounts of...
epinephrine in response to stressful conditions that increase the body's need for energy quickly. These conditions include intense physical activity and "fight-or flight" situations
These factors help to explain the increased risk of serious health problems faced by women..
even if they abuse lower amounts of alcohol than men.
Regardless of whether the cause of a fatty liver is insulin resistance or...
excess alcohol intake, the condition is a sign of impending liver damage.
Under normal conditions, the body does not eliminate the...
excess glucose by excreting the monosaccharide in urine.
Ketoacidosis is a potentially life-threatening condition that requires immediate medical care. Signs and symptoms of ketoacidosis include....
excessive thirst, frequent urination, and a blood glucose level of more than 250 mg/dL. Individuals with the condition may also have nausea, vomiting, abdominal pain, fatigue, and confusion.
The end result of this metabolic shift is the synthesis and storage of triglycerides in adipocytes. In a sense, the...
extra glucose molecules "spare" conserve fatty acids by enabling the lipid molecules to be made into triglycerides and stored for ATP production in the future. This process explains why people who eat excess carbohydrates can gain body fat.
The breakdown of adipose and muscle tissue to provide fuel sources for the starving person contributes to the...
extreme weight loss, muscle wasting, and weakened condition of the affected individual. Starvation is a highly catabolic state, characterized by glycogenolysis, lipolysis, proteolysis, and ketogenesis.
The fatty acids supply some energy for muscle tissue, and they are also taken up the liver. Eventually, the rapid influx of...
fatty acids into the liver becomes too much for the organ cells to handle. When this occurs, liver cells rely on ketogenesis to convert acetyl CoA into ketone bodies, an alternative fuel source described in.
Alcohol directly affects the liver by disrupting the normal metabolism of glucose...
fatty acids, and amino acids. The two dehydrogenase reactions in the metabolism of alcohol each result in the transfer of an electron to the electron carrier molecule NAD+, producing NADH. As NADH accumulates in liver cells, the amount of NAD+ has the following effects on liver cells' normal metabolic pathways.
Binge drinking is defined as having four or more drinks for females and...
five or more drinks for males per 2-hour occasion. As a college student, you may have observed binge drinking or engaged in the practice.
When the liver's glycogen supply is "on empty", glucagon stimulates liver cells to convert certain amino acids derived....
from muscle tissue into pyruvate and then glucose (gluconeogenesis). During this time, the liver and muscle tissue use mainly fatty acids for fuel. Once a person "breaks the fast" by eating a carbohydrate rich meal, the insulin response to the influx of glucose into the blood stream effectively turns the metabolic tide from a catabolic state to an anabolic state.
Acetate can be converted to Acetyl CoA, which may be...
further metabolized via the citric acid cycle to form CO2 and H2O, or the molecule can be used to synthesize fatty acids or ketone bodies.
Therefore, the hormone can have catabolic or anabolic actions. Thyroid hormone increases the rate of...
glucose catabolism, lipolysis, and protein synthesis. As a result of these actions, cell are able to develop and grow normally.
Most cells normally oxidize glucose as their primary fuel. However, if cells do not have enough...
glucose to "burn" for energy, beta-oxidation of fatty acids increases, which produces excessive amounts of acetyl CoA.
After entering, three fatty acids can be attached to a...
glycerol molecule, re-creating a triglyceride molecule. Making triglycerides from fatty acids and glycerol molecules requires very little energy input.
The liver is the main target organ for glucagon's action. Glucagon signals liver cells to increase...
glycogenolysis and gluconeogenesis from glucogenic amino acids. This action enables the liver to produce more glucose for release into the bloodstream.
Many people consume protein supplements because they think it will...
help them gain muscle mass. Obtaining adequate amounts of energy from all macronutrients and exercising muscles is necessary to build muscle size, strength, and endurance.
Furthermore, insulin stimulates protein synthesis in cells. Glucagon, cortisol, and epinephrine are...
hormones that instruct cells to use catabolic rather than anabolic pathways.
The increased ratio NADH to NAD+ can lead to...
hypoglycemia because not enough NAD+ is available to maintain the normal rate of gluconeogenesis
After a fatty meal, the absorption of triglycerides results in an...
influx of triglycerides into the liver. Some of the fat remains in the liver, but a considerable amount of the lipid is incorporated into very-low density lipoproteins.
In the US, a BAC of 0.08% is the legal limit for...
intoxication for automobile operators who are 21 years of age or older. Some states have a lower legal limit and the national limit for BAC may be reduced to 0.05% in the future.
The liver and to some extent, the...
kidneys are able to use glucogenic amino acids to make glucose (gluconeogensis). Liver cells can use the glucose formed by gluconeogenesis to synthesize glycogen or release the simple sugar into the bloodstream for other cells to use.
Metabolizing alcohol by the MEOS also produces acetaldehyde that must be further processed to yield acetyl CoA. Chronic and excessive alcohol intake...
leads to increased production of MEOS enzymes. As a result of this adaptation, the liver can metabolize the excess alcohol more rapidly.
Increases in the BAC reflect an alcohol consumption rate that exceeds the liver's capacity to metabolize the drug. To determine whether someone is...
legally intoxicated as a result of drinking alcohol, law enforcement officials use special devices to analyze the alcohol in expired air for estimating a person's BAC.
Compared to men, women tend to absorb more alcohol, and they also have...
less body water to dilute the alcohol that they consume.
When liver cells become insulin resistant, their ability to regulate glycogen synthesis and gluconeogenesis become altered. The liver continues to produce glucose and release the...
monosaccharide into the bloodstream. As the blood glucose level rises even higher, the pancreas secretes more insulin.
When a person consumes a surplus of glucose, his or her cells catabolize the...
monosaccharide molecules for ATP production instead of breaking down fatty acids.
Beer and wine contain simple carbohydrates and small amounts of certain minerals and B vitamins. Distilled spirits have essentially no...
nutritional value other than water. Mixing distilled spirits with juices, cocktail mixes, or other flavorings increases the alcoholic beverage's energy content and may add some nutrients, particularly simple sugars, depending on the ingredients in the mixer.
The body is adapted to survive an extended period without food intake. The same physiological adaptions that...
occur during an overnight fast also occur as the fast continues. Over a longer period of fasting-starvation- the body makes some additional changes to ensure that cells have access to a variety of fuels.
Furthermore, lipogenesis occurs in the cell's cytoplasm, instead...
of in mitochondria, and requires the input of energy and the help of the electron carrier molecule NADPH (this molecule is different from NADH because it has a phosphate group).
In addition, lipolysis in adipocytes is not restricted, resulting in the release of more fatty acids into the bloodstream. As a result...
of these metabolic changes, levels of glucose and fatty acids in blood increase dramatically.
A ketogenic diet supplies most of its energy from fat. Such low-carbohydrate diets are...
often popular with people who want to lose weight. Limiting carbohydrate intake to less than 50g per day not only rapidly depletes glycogen stores, but it also results in ketosis.
In 2015, 25% of Americans who were 12 years of age or...
older reported being binge drinkers during the 30 days prior to the survey. Binge drinking is a form of heavy drinking, but the definition of binge drinking differs according to sex.
Both problem drinkers and people with an AUD engage in behaviors that place themselves and...
others in danger, such as drinking and driving. According to the government estimates, almost 6% of Americans who were 12 years of age and older had an AUD in 2015.
As blood glucose levels fall during the early part of an overnight fast, the...
pancreas responds by releasing glucagon. Glucagon instructs liver cells to increase glycogenolysis.
Thus, consuming more protein or amino acids than your body needs for...
protein or ATP synthesis can increase your body fat.
Muscle, fat, and liver cells have insulin receptors on their cell membranes. Insulin binds to these...
receptors, which conveys specific information to the cells. As a result of this binding, these cells allow glucose and fatty acids to enter them, and the cells can sore energy.
The kidneys also filter some of the drug from the bloodstream and eliminate it in the urine. A person's blood alcohol concentration (BAC) is...
reported as a percentage that indicates the concentration of alcohol in the bloodstream.
According to one survey, 39% of young adults who were 10 to 25 years of age...
reported at least once during the previous 30 days.
Cortisol is often referred to as a "stress hormone" because it is secreted in...
response to a variety of stressful situations, such as low blood glucose levels, severe injuries, or psychological states that evoke anxiety of fear.
Glucagon is made by the alpha cells of the pancreas. Alpha cells secrete glucagon in...
response to blood glucose levels that drop to below normal levels (postabsorptive state).
The cells that synthesize these catabolic hormones release higher amounts of them in....
response to intense exercise, extreme stress, or starvation. The collective activity of these hormones is to increase fuel mobilization from storage, so sources of energy are available for all of the body's cells
Simply consuming protein or amino acid supplements is likely to...
result in gaining adipose tissue instead of lean body mass.
When the drinker's BAC reaches 0.20%, his or her brain is unable to process info. Higher BACs (0.25% or more) usually....
results in loss of consciousness (passing out).
Beta cells in the pancreas synthesize insulin, a protein that...
serves as the primary anabolic hormone.
The hormone attaches to special receptors on the cell membranes of adipocytes and muscle cells. This attachment results in a...
signal to glucose transport proteins that are also in the cell membrane. In response to the signal, the glucose transport molecules pass the monosaccharide across the cell membrane and into the cytoplasm.
Liver and muscle glycogen stores become depleted with extended fasting. When that...
situation occurs, muscle cells begin to rely more on fatty acids for energy. Adipose tissue responds to starvation by increasing lipolysis, and as a result, the level of fatty acids increases in the blood stream.
Insulin resistant cells do not take up glucose and fatty acids from the bloodstream and store energy effectively. Thus, blood glucose levels...
stay abnormally elevated (hyperglycemia) long after a meal is consumed.
Metabolic pathways are coordinated by hormones, that...
stimulate and regulate cellular activities. Key hormones that direct or regulate metabolic activities are insulin, glucagon, cortisol, epinephrine, and thyroid hormone.
Cortisol promotes protein catabolism and...
stimulates the liver to increase its use of amino acids for gluconeogenesis.
Instead, liver and muscle cells can....
store the glucose as glycogen through a pathway called glycogenesis.
Therefore, triglyceride synthesis is the primary route for...
storing excess fatty acids, especially adipocytes.
In contrast, if you spend most of the day sitting around, your body's energy needs are comparatively low. Therefore, any...
surplus of food energy provided by your evening meal will likely result in energy storage because your cells favor anabolic pathways.
Furthermore, alcoholics are at risk of hypothermia (lower-than-normal body temperature) when exposed to cold. The reason is...
that to remove the excess heat that result during the metabolism of alcohol, blood vessels relax (vasodilation)
When this occurs, the citric acid cycle cannot use the fatty acid molecules efficiently because...
the acetyl CoA molecules outnumber the oxaloacetate molecules that are available. Recall that the first step in the citric acid cycles requires acetyl CoA to bind to oxaloacetate, forming citrate.
During prolonged fasts, even the brain can catabolize ketone bodies for energy. Under normal conditions, glucose and fatty acids are...
the body's primary fuels, and they "spare" the body's proteins from being used as a major energy source.
If acetyl CoA molecules that were derived from these carbon skeletons do not enter...
the citric acid cycle, they may be used for fatty acid synthesis.
Vasodilation increases the circulation of blood to the skin, enabling body heat to dissipate into...
the environment more readily. As a result, alcoholics may feel warm and fail to wear proper clothing when in cold conditions. If not recognized and treated promptly, hypothermia can be deadly.
cells may use excess dietary glucose molecules to form...
triglycerides, but the conversion requires more steps and more energy. Thus, only a small percentage of extra dietary glucose is converted to triglycerides and stored in adipocytes.
Ketosis usually causes loss appetite, so people who are...
trying to lose weight may find this symptom desirable. The long-term health effects of mild ketosis are unknown.
If you suspect someone has consumed a deadly amount of alcohol, do not...
waste time tying to estimate how many drinks that person has drunk. Call 911.
Beers are typically 3 to 6% alcohol, and wines contain about 8 to 14% alcohol by volume. Distilled spirits (hard liquors) such as...
whiskey, bourbon, and vodka are generally 40 to 50% alcohol.
If you spend much of the day engaging in vigorous physical activity, your body's energy needs are high. In this situation....
your cells will process the macronutrients in your dinner meal by way of ATP-producing, catabolic pathways.
Step 3 of the citric acid cycle:
Alpha-ketoglutarate undergoes oxidation, losing a carbon atom in CO2. Once again, a NAD+ molecule picks up hydrogen and becomes NADH. As a result, succinyl-CoA forms.
Step 2 of ETC:
Cytochrome c facilitates the bonding of two hydrogen ions (H+) with an atom of oxygen, forming H2O as a result. This H2O may be referred to as "metabolic water "or the "water of metabolism."
Electron transport chain:
The NADH and FADH2 that were produced in earlier steps transport their hydrogen ions to the inner membrane of the mitochondrion, where the ETC is located. The enzymes that comprise the chain pass the electrons along, releasing much of their energy in the process. Some of the energy is captured during the formation of ATP and ADP and Pi. At the end of the chain, an atom of oxygen accepts two hydrogen ions. This final reaction forms water.
Guarana naturally contains caffeine and two chemically related stimulants, theobromine and theophylline.
The benefits of energy drinks do not live up to the marketing hype used to promote the products.
Glycolysis: Pyruvate's aerobic conversion to acetyl CoA:
The two pyruvate molecules enter a mitochondrion, and with the help of coenzyme A, each 3 carbon molecule is broken down into acetyl CoA, a 2 carbon molecule. During this process, NAD+ picks up Hydrogen ions to form NADH, and carbon dioxide is released.
Much of the energy that is released in the process is ultimately captured in ATP. There are 5 steps during the citirc cycle. Step 1:
The two-carbon acetyl CoA enters the citric acid cycle binds to oxaloacetate, a four-carbon molecule. This initial reaction forms the six-carbon molecule, citrate.
When ATP loses its terminal phosphate group it becomes....
adenosine diphosphate. Note that ADP has adenosine bound to two (di-) inorganic phosphate groups
In mitochondria, the catabolism of an activated fatty acids begins with...
a chemical pathway called beta-oxidation. Most naturally occurring fatty acids have an even number of carbon atoms.
Caffeine powder is available for commercial use as...
a food additive in soft drinks, but health food stores and Internet dietary supplement outlets also promote the product as a "thermogenic" supplement.
The coenzymes NADH and FADH2 carry ions and their high-energy electrons from the citric acid cycle to...
a linked series of enzymes called the electron transport chain. This consists of enzymes within the mitochondria.
Enzymes generally will not catalyze reactions without the help of coenzymes. Coenzymes are...
a particular group of organic compounds that often have B vitamins in their chemical structures
Each molecule of acetyl CoA goes through one cycle of the citric acid cycle. Under normal conditions, two...
acetyl CoAs are available from the catabolism of the six-carbon sugar, glucose. Therefore, the citric acid cycle repeats itself once again for each glucose molecule that enters the catabolic pathway.
The total amount of energy in a system is constant; that is...
energy can neither be created nor destroyed. However, energy can undergo transformations.
Such defects usually result from the inability to synthesize an...
enzyme needed for a chemical pathway to proceed. In some cases, the error has little or no effects on health, but in other instances, the biochemical defect is severe and its effects are lethal (deadly).
Fat cells (adipocytes) contain the enzyme hormone sensitive lipase (HSL). When cells...
especially muscle cells, need to catabolize fatty acids for energy, HSL facilitates lipolysis by removing the three fatty acids from the glycerol backbone of a triglyceride.
During beta-oxidation, fatty acid molecules are cleaved into 2 carbon segments that are converted into acetyl CoA. Except for the...
final cleavage reaction, one NADH and one FADH2 are also produced when a two-carbon segment is removed from the fatty acid.
Step 5 of the citric acid cycle:
the cycle reaches the "ending point" by reforming the four carbon molecule, oxaloacetate. As a result, oxaloacetate binds with acetyl CoA, so the cycle of chemical conversions can repeat itself.
Thus, the glucose must be catabolized for energy within the...
muscle cell where the glycogen had been stored. This adaptation enables muscles to have stock piles of glucose (stored as glycogen) in case of a "fight-or-flight" response.
The coenzyme pyridoxal phosphate (PLP) is....
needed for the conversion of glycogen to glucose molecules.
The coenzymes NAD+, coenzyme A, and thiamin pyrophosphate (TRP) are...
needed to form acetyl CoA from pyruvate. During the formation of acetyl CoA, pyruvate releases a molecule of CO2 and two hydrogen ions that are picked up by NAD+. This reaction is irreversible: Acetyl CoA cannot be used to re-form pyruvate. Thus, the formation of acetyl CoA is the "point of no return" for glucose catabolism.
The body highly regulates ATP production in response to the body's energy demands and..
not to consumption of such products. Any beverage that contains digestible carbohydrate, such as sucrose or lactose, provides energy for the body.
The fatty acid molecule yields eight acetyl CoA, seven NADH, and 7 FADH2 molecules as a result of undergoing beta-oxidation. Thus, beta-oxidation of...
palmitic acid produces about 28 ATP. That amount of ATP may not seem to be impressive, but the catabolism of the fatty acid molecule is not complete.
The liver and muscle tissue are the....
primary sites for glycogen storage and degradation.
Muscle cells lack the enzymes necessary to make glucose from lactate, so the 3 carbon compound is...
released into the bloodstream. Liver cells remove the lactate from the bloodstream and recycle it into glucose, using a pathway called the Cori cycle. After the liver releases the newly made glucose into circulation, it is available again as fuel for cells.
The cells in the human release, transfer, and use energy constantly. Human cells obtain energy by...
releasing the chemical energy that is stored in macronutrients and alcohol. It is important to remember that only carbohydrates, lipids, proteins, and alcohol can be utilized for energy; cells cannot release energy from vitamins, minerals, or water.
Glycerol is chemically similar to pyruvate in that it contains 3 carbons. The liver can...
remove glycerol from the blood and convert it to pyruvate or glucose (gluconeogenesis). Glycerol catabolism, however, does not produce much ATP. Most of the energy in a triglyceride molecule is stored in its fatty acids.
Anabolic reactions are "uphill" because they...
require the input of more energy than is released by the reactions. The newly formed molecules store this extra "input" energy for later use by the body.
ATP can be re-formed by phosphorylation, an anabolic reaction that....
results in the attachment of a Pi group to ADP.
Gluconeogenesis is not the...
reverse of glycolysis because some steps in the glycolytic pathway flow in only one direction: toward the citric acid cycle.
If no effective treatment is available, babies born with...
severe metabolic errors often die in infancy or early childhood.
The chemical reactions that oxidize (breakdown) glucose to produce ATP are...
significant from a nutritional and health standpoint. The water-soluble B vitamins thiamin, pathothenic acid, niacin, and riboflavin are components of coenzymes TPP, coenzyme A (CoA), NAD+, and FAD.
The lack of acetyl CoA results in decreased ATP formation, and the...
signs and symptoms of thiamin, pantothenic acid, niacin, and riboflaavin deficiency disorders soon become apparent.
Glycolysis is an anaerobic pathway that occurs in the cytoplasm of cells. In a series of chemical reactions, the...
six-carbon glucose molecule is converted into two three-carbon molecules of pyruvate, which is also known as pyruvic acid
In the liver, glycogenolysis occurs when any tissue of the body needs energy. The liver degrades its....
supply of glycogen and releases glucose into the bloodstream for eventual uptake by the cells.
Glucose is such an important biological fuel, the body can make the simple sugar, primarily in the liver. Gluconeogenesis is the...
synthesis of glucose from noncarbohydrate precursors that include glycerol, lactate, pyruvate, and amino acids.
A car needs a spark (energy) from the battery to start its engine. In cells, energy from two ATP molecules is...
the "spark" required to initiate the catabolism of a glucose molecule and crank up our "metabolic engine." Although glycolysis uses two ATP to get started, the process forms four ATP.
ATP is a high-energy phosphate compound. When an enzyme "cleaves" (breaks)...
the bond between the last two phosphate groups of ATP, the high-energy molecule loses some of its power. Cells can use the energy released in this reaction for anabolic activities
The most important products of chemical transformation that occur during the citric acid cycle are...
the coenzymes that are produced. NAD+ and FAD pick up hydrogen ions and electrons. These high energy electrons move on to the next phase of glucose catabolism and are responsible for the production of ATP.
