Lesson 9: Water and Energy

What is the Thermic Effect of Food (TEF)?

- An estimation of the energy required to process food (digest, absorb, transport, metabolize, and store ingested nutrients). - The Thermic Effect of Food is, therefore, the estimated amount of energy required to process food. - It consumes about 10% of your total caloric intake. - Processing includes: - Digestion. - Absorption. - Transportation. - Metabolizing the Nutrients. For example, once absorbed, fructose is delivered to the liver and converted to glucose, which is then used to make Glycogen. All of this work requires an input of ATP.

What is Basal Metabolism?

- Basal metabolism is the rate of energy use for metabolism under specified conditions: after a 12-hour fast and restful sleep, without any physical activity or emotional excitement, and in a comfortable setting. It is usually expressed as kilocalories per kilogram body weight per hour. - Basal Metabolism is the energy spent to maintain life when the body is completely at rest. - That means not digesting food, running, emotionally distressed, or studying. Let's call it housekeeping. - A body's Basal Metabolic Rate (BMR) is the rate at which this energy is spent for the body's housekeeping. You can vacuum fast or slow, but you must vacuum.

What is the energy input and output of mechanical digestion?

- But mechanical digestion is also costly. - That ripple of peristaltic contractions along the alimentary canal to keep food moving requires an input of energy for the muscles to contract. - The muscles are being constantly phosphorylated by ATP. - Furthermore, the stomach churns the food for extended periods of time to break up the chyme before it enters the small intestine. - This is why you are tired after a big meal!

What role do genes and environmental factors play in environment and nutrition?

- Your BMR is largely genetically determined. - Genes do not control everything, however. - The environment also plays a role; the environment can be experienced in utero, as a neonate, or during adulthood.

Give an example of how the sodium-potassium protein pump is put to work.

1. ATP phosphorylates the transmembrane protein, causing it to continuously change shape. 2. As it changes shape, sodium is pumped out of the cells, while potassium is pumped inside of the cells. 3. The protein is in constant motion because it is continuously phosphorylated. 4. Consequently, ATP must be in constant supply for the sodium-potassium protein pump to work, and for you to maintain fluid balance.

What is Antidiuretic hormone (ADH)?

A hormone produced by the posterior pituitary gland in response to dehydration (or a high sodium concentration in the blood). It stimulates the kidneys to reabsorb more water and therefore prevents water loss in urine. (also called vasopressin).

What is aldosterone?

A hormone secreted by the adrenal glands that regulates blood pressure by increasing the reabsorption of sodium by the kidneys. Aldosterone also regulates chloride and potassium concentrations.

Describe the chemical properties of ATP.

ATP contains about 40% of the chemical energy that was stored in the carbon-hydrogen bonds of glucose. The rest (60%) was lost as heat. Why is ATP the energy currency of the cell? How does it work? After all, ATP is merely a compound like millions of others. What makes it different? For starters, it is highly reactive because of the cluster of negatively charged oxygen atoms in close proximity. This makes ATP analogous to a compressed spring. A compressed spring is an object like a table is an object, but a table cannot perform work. A spring can. Highly unstable, the last phosphate group of ATP is released and the energy is liberated in the form of kinetic energy.

How is ATP synthesized?

ATP is synthesized from adenosine diphosphate (ADP), and a phosphate. The energy for the reaction is supplied by the breakdown of macronutrients. By eating energy-rich meals, we provide the mitochondria with the fuel necessary to make ATP. ATP is then used for the day-to-day business of the cells of the body. For instance, the day-to-day business of the liver includes many vital functions. (Look at 'What are the responsibilities of the liver?' Card) By starving yourself during crash diets, your liver, among other organs, pays the price!

How many litres of water does an adult body contain?

An adult body contains approximately 40 liters of water. About two-thirds (2/3) of that water is found inside of cells. About one-third (1/3) of that water is contained in the extracellular fluid compartment.

How do kidneys and osmosis work together?

Before learning more about kidney function, remember that water always follows ions. The posterior pituitary gland releases antidiuretic hormone ADH when blood volume is low, or when the concentration of sodium in blood plasma is high. In both cases, water must be conserved either to 1. Increase blood pressure, or to 2. Dilute the concentrated extra cellular solution. In fewer words, ADH makes less urine. Working alongside the pituitary gland, the adrenal glands secrete aldosterone. Aldosterone signals the kidneys to reduce the elimination of sodium in urine. And because water always follows ions, the water is conserved as well. Furthermore, ADH and aldosterone promote the elimination of potassium, an intracellular ion. By doing so, they encourage water to remain in the extracellular compartment and not migrate into body cells.

Give a summary of the steps before ATP takes place.

Breathing saturates red blood cells with oxygen (O2). Eating saturates your blood with nutrients, like glucose. Blood capillaries is where gases, nutrients, and waste are exchanged between cells and the blood. Offloaded into the interstitial space, oxygen and biological fuels enter the intracellular space and flow into the mitochondrion, the ATP factory of every cell. The mitochondria transfer the chemical energy that was once stored inside of the energy-yielding nutrients into ATP. The end product of this catabolic chemical reaction is metabolic water (H2O), Carbon dioxide (CO2 exhaled), and ATP (energy currency of the cell). Carbon dioxide is moved into the blood capillaries and exhaled from your nose. Water is used by the cell. ATP is a highly reactive molecule, ready to perform work. The number of mitochondria per cell varies as a function of their metabolic rate; Energy-demanding muscle cells and liver cells are saturated with mitochondria. Less metabolically active cells, like fat cells, have less mitochondria.

What are catabolic chemical reactions?

Catabolic refers to reactions in which large molecules are broken down to smaller ones. Catabolic reactions release energy. (kata = [break] down) Catabolic pathways break down compounds into smaller pieces. The breakdown of glucose, glycerol, fatty acids, and amino acids releases energy. Part of this energy is lost as heat. The rest of it is transferred over to adenosine triphosphate, or ATP. ATP is the energy currency of the cell. For the liver to run its endless anabolic chemical reactions, it requires a constant supply of ATP.

What is the name for a positively charged ion? Negatively charged ion?

Cations are positively charged ions. Anions are negatively charged ions.

To understand the power of solutes, what can you do with an eggplant?

Cut the eggplant open, place some salt over it, then wait a few minutes. Within a short time, water leaves the plant cells and pools toward the surface, where the salt is most concentrated. Conversely, raisins placed in water begin to swell, as water moves inside, where sugar is most concentrated. This simple chemistry rule, known as osmosis, is crucial for understanding fluid balance. It is also crucial in cooking; salting meat well, before you cook it, draws out water from muscle cells, preventing you from properly searing the meat.

What is the DASH diet?

Dietary Approaches to Stop Hypertension. Power of Osmosis: Even if you do nothing to reduce salt intake but increase potassium and magnesium, blood pressure can be significantly reduced.

What do electrolytes do?

Electrolytes help to control the volume of water within the fluid compartments. For example, table salt placed in water dissociates to sodium and chloride.

Where does energy input come from?

Energy input comes from carbohydrates, lipids, and protein. If we base it on the AMDRs, the bulk should come from carbohydrates, followed by lipids and protein. Energy in must equal energy out for individuals wanting to maintain a stable weight. The outlet includes: 30-50% Physical Activity 10% Thermic effect of food 50-65% to run basic metabolic needs (basal metabolism) Basal metabolism, the largest part (1,300 kcal out of a 2,000kcal diet), is taken up by your basal metabolism.

What is metabolism and energy?

Energy is obtained from the foods you eat and spent to run the chemical reactions inside of your cells. Metabolism is the sum total of all the chemical reactions that go on in the body and in living cells. A high or low metabolism is the rate at which these reactions occur, and can be anabolic or catabolic. Anabolic chemical reactions build stuff, and therefore require energy input. These pathways use small, simpler compounds to build larger, more complex compounds. For example, the building of glycogen from glucose requires an input of energy. (Glucose + Glucose and ATP = Glycogen) So does the building of triglycerides (Glycerol + Fatty Acids and ATP = Triglycerides) and proteins (Amino Acid + Amino Acid and ATP = Protein) from their respective building blocks.

How is weight controlled by how we spend our extra calories?

Everyone knows that physical activity consumes energy. If your total caloric intake is 2,000 kilocalories, your weight will be controlled by how much of those extra calories you spend. If you spend those extra calories through regular exercise, your weight remains stable. If you lead a sedentary life, the pounds will begin to accumulate, because excess energy, whether it is in the form of carbohydrates, lipids, or protein, will get stored as fat in adipose tissue. Weight loss will occur when energy expenditure exceeds the intake.

What are the side effects of ecstasy on water intake?

Extreme thirst and reduced urine production are side effects of ecstasy. Water intoxication causes hyponatremia. Water moves into cells, symptoms can escalate from headaches, confusion, seizures, and coma to death.

Which sorts of cells contain less than 20% water?

Fat cells, bone cells.

How can fluid and electrolyte imbalance occur?

Fluid and electrolyte imbalance can occur from water deficiency and toxicity. This sudden imbalance overwhelms the capacity of your kidneys to maintain fluid and electrolyte homeostasis. Deficiencies can be mild to severe. Vomiting and diarrhea can lead to excessive water losses in a short period of time. Simple water intake can treat mild dehydration. For more severe cases, electrolytes must also be replenished. For example, during prolonged physical activity, extracellular electrolytes, along with water, are lost through sweat. If balance is not restored, this can lead to Hyponatremia. Hyponatremia is a decreased concentration of sodium in the blood. Hypo = below, Natrium = sodium, emia = blood The symptoms of hyponatremia includes severe headaches, confusion, and seizures. What happens at the cellular level? Water leaves the intravascular and interstitial compartments and migrates into cells, including cells of the nervous system. Hyponatremia requires immediate medical attention. Sports drinks can ensure electrolyte balance during prolonged physical activities in hot temperatures.

Imagine an ATP molecule, describe its function?

Imagine if you were standing in from of a larger than life ATP molecule. As the last phosphate is released, it transfers its stored energy on to you, and caused you to jerk. You've been phosphorylated! If you were continuously phosphorylated, you would be dancing. In reality, motion is caused by the concentration of muscle fibers that move the skeleton. At the cellular level, muscle fibers get phosphorylated, allowing them to slide past each other and contract. Enzymes and other proteins get phosphorylated, causing them to change configuration and perform work. The result of losing that last phosphate turns ATP into ADP.

Describe nutritional genomics.

In Lesson 1, we introduced nutrition's sister discipline; nutritional genomics. The interaction between diet and genes goes two ways; - Nutrigenomics studies how food can affect gene expression. - Nutrigenetics examines how genetic differences influence how nutrients are metabolized. These interactions can, not only set your BMR, but also amplify or silence risks for other diet-related chronic diseases. What you eat CAN and DOES change you! We still have a long way to go before we can disentangle the role of the environment on gene expression. But given the overwhelming evidence of the interaction between genes and nutrition, the best one can do is to learn how to cook simple, healthy meals to reduce risks of harm and increase chances of entering old age in the best possible condition.

Can quality of the diet also play a role?

In a study on the role of gestational nutrition on obesity, genetically similar mice carrying a gene mutation that increased the risk for obesity had very different fates because their mothers had very different diets. The normal-weight mouse's mother received dietary supplements, which silenced the obesity gene. In short, nutrients can and do affect gene expression; this is what we call epigenetics; the study of how the environment can alter gene expression.

What directs the kidneys?

In addition to eliminating waste, the kidneys also control blood volume, blood pressure, and the solute concentration of body fluids. After all, blood plasma is about 92% water. The volume of this fluid compartment influences blood pressure. The greater the amount of fluid, the greater the amount of pressure on the walls of the blood vessels. Conversely, low blood volume leads to low blood pressure. The kidneys themselves are controlled by secretions from the posterior pituitary gland located in the brain and the adrenal glands, that sit on top of the kidneys. The pituitary gland secretes Antidiuretic Hormone (ADH) and the adrenal glands secrete Aldosterone. These two hormones control the volume of urine and its solute concentration.

What is the extracellular fluid compartment?

Includes the intravascular compartment/cardiovascular system, lymphatic system, and interstitial fluid compartment. Also includes sweat, tears, gastric juices, spinal fluid, and fluid between joints. To function properly, the body must maintain the correct amount of water in each type of cell and compartment.

What are the responsibilities of the kidneys?

Kidneys require approximately 140kcal/day to function: - Convert inactive vitamin D into the final and active form. - Filters and process 5 cups of blood per minute to clear waste and maintain fluid balance. - For its size, the kidney takes the prize for the most energetically expensive organ to maintain.

What is the average number of kilocalories consumed per day per organ?

Liver - 27% - 380kcal/day Brain - 19% - 265kcal/day Skeletal Muscle - 18% - 250kcal/day Kidney - 10% - 140kcal/day Heart - 7% - 100kcal/day Other - 19% - 265kcal/day This is why an adequate diet is important for getting straight A's in school. From this example, basal metabolism accounts for 1,400kcal per day. This means that, if you consume an average of 2,000 kcal/day, you need to spend close to 600 kcal/day in physical activity to maintain a stable weight. The more calories you consume, the more you need to spend on physical activity.

Which sorts of cells contain 70-80% water?

Muscle cells, epithelial cells.

Describe Fetal Environment and BMR

Now that we have convinced you that the environment can change you, let's look at how fetal environments can potentially set the BMR. In a massive epidemiological study, comprised of 16,000 men and women born in England between 1911 and 1945. Low birth weight babies had a significantly higher risk of being obese as adults. The idea that caloric intake during pregnancy can affect BMRs has been studied for several decades. Known as the Thrifty Gene Theory, it is hypothesized that fetuses deprived of calories lower their BMRs because they predict an environment of food scarcity. But as it turns out, the risk for obesity is far too complex to be able to point the finger at a singular cause, like gestational caloric intake.

What are some of the roles that water plays in the body?

Now that you understand how water moves between compartments we can look at some of the roles water plays in the body. The most important function is the transport of nutrients and waste. Recall that blood is made up of red and white blood cells and plasma. Plasma is mostly water with suspended nutrients that are delivered to your cells and waste to the kidneys for elimination. Urine itself is mostly water with suspended body waste.

What is the best, most cost-effective physical activity for maintaining weight?

Running, since all you need is a pair of shoes. Buying a good pair is an excellent investment. What more is that running helps the brain. Cognitive benefits include improved memory, and by extension, improved grades.

With the knowledge of osmosis and our kidneys, how can we better manage our blood pressure?

One way to lower blood pressure is to: Increase potassium intake, Increase magnesium intake, reduce sodium intake. Cells that are more richly populated with electrolytes have the capacity to lower blood volume by drawing water out of the extracellular fluid compartments and in to the intracellular compartment. This approach to managing blood pressure is called the DASH diet.

What are the factors that influence BMR?

Some people can eat a lot and not gain much weight, while others are far more sensitive. Several factors can affect and ultimately set your basal metabolic rate: - Body composition. - Sex. - Body surface area. - Age. Muscle tissue, being packed with mitochondria, is MORE metabolically active than fat tissue. - Thus, the more muscle tissue you have relative to fat, the higher your BMR. - And since men on average have higher muscle mass than women, your biological sex also influences BMR. - Men have higher BMRs than women. - Growing children have high BMRs. This is why a teenager can eat an enormous quantity of food and not gain any weight. - Meanwhile, old age slows down BMRs.

What are factors that can influence basal metabolism?

Tall people have a greater total body surface area. Consider two structures with 8 blocks; one 1x8, and one 4x4. Both contain 8 blocks, but the taller one has 34 exposed sides, while the smaller one has only 24. A tall slender person who weighs 150lbs has a higher metabolic rate than a shorter person who also weighs 150lbs. Why? Because the taller body has more surface area from which heat energy can escape. Consequently, to maintain body temperature, the taller individual has to burn more calories to replace the heat that is lost. But these are all, of course, averages. And averages are meant for a population, and may not apply to the individual. An individual's BMR can also be determined by the environment.

When is the BMR measured?

The BMR is measured: - After fasting and resting for 12 hours. - Calculates the energy spent for breathing, circulating blood, and maintaining organ functions. - It does not include the energy spent for physical activity, digestion of food, and absorption and processing of nutrients. - BMR is measured in kilocalories per kg of body weight per hour.

How is it possible for the body to maintain the correct amount of water in each type of cell and compartment?

The ability of water to move freely and accurately between compartments is crucial. In lesson 3, we stated two golden rules in chemistry. The third is: where ions go, water follows. More elaborately; water molecules move towards compartments with the highest concentration of solutes. By controlling the amount of solutes within each compartment, the body can control the amount of water inside and outside of cells.

What is osmosis?

The diffusion of water through a selectively permeable membrane. In the body, this selectively permeable membrane is the membrane of your cells; cell membranes. The membrane is porous to water molecules only; solutes may not cross freely.

What happens in osmosis when the solute concentration is equal on both sides of the membrane?

The free-moving water molecules cross from one side of the membrane to the other. Other water molecules are not so free; they are hydrogen bonded to the solutes. Given that both sides have an equal concentration of solutes, we have an equal concentration of free and not-so-free water molecules.

What do your kidneys do?

The human body is composed of 50% to 70% water. The percentage of water in the body varies by at least two factors; the first is age. A newborn contains about 75% water by weight, while an elderly person is about 45% water by weight. The second is sex. Because body composition matters, recall that muscle tissue contains more water than fat tissue. Given that, on average, young adult men have more lean muscle tissue than young women, it follows then that men have more body water than women. Remember than muscle tissue = 75% water, and fat tissue = 20% water. Regardless of age or sex, the body maintains a near constant amount of water. Water sources include water from beverages and food. Fruits and vegetables can contain up to 90% water, while cheeses up to 50% water. Metabolic water is also a source of water, and it is produced from the chemical breakdown of macronutrients. Intake is balanced with water losses. The kidneys eliminate water along with waste in the form of urine. The rest of the losses occur through the skin in the form of sweat, expired air, and through feces. The kidneys and the brain work cooperatively to maintain the right amount of body fluid. Every time the heart contracts, 21% of the blood that is forced out heads directly to the kidneys for processing. Each minute, the kidneys receive nearly five cups of blood. Imagine these five cups of blood reaching your kidneys for processing. From this, they will make 1mL of urine per minute. The kidneys receive blood from the heart via the renal artery. Waste is removed from the blood and the cleaned blood leaves the kidneys via the renal vein. The waste, along with water, reaches the bladder via the ureter. Cardiac output = volume of blood pumped into circulation per minute.

What are the responsibilities of the liver?

The liver requires approximately 380kcal/day to function. - Build glycogen (Lesson 4). - Synthesize cholesterol (Lesson 5). - Make VLDLs (Lesson 5). - Synthesize 11 non-essential amino acids (Lesson 6). - Convert ammonia to urea during deamination of amino acids (Lesson 6). - Convert retinol into other vitamin A forms (Lesson 7). - Convert vitamin D3 into an intermediate form (Lesson 7). This is just a small fraction of the liver's roles. The liver is, energetically, a very demanding organ, consuming 380 kilocalories per day.

What is water intoxication?

The rare condition in which body water contents are too high in all body fluid compartments. Water intoxication occurs when excessive amounts of plain water is consumed in a short time period, or when the kidneys have difficulty filtering water from blood.

Water Toxicity: There is no upper limit (UL) for water, but...

There is no upper limit for water. But water intoxication can result from overconsuming plain water after prolonged physical activity. It can also be a consequence of taking drugs like ecstasy, which cause extreme thirst. Once again, the excess water dilutes the sodium concentration of blood, and causes hyponatremia. Water moves into cells, leading to symptoms that can escalate from headaches, confusion, seizures, and coma, to death.

What happens in osmosis when the solute concentration is unequal on both sides of the membrane, because one side received additional solutes?

This raises the solute concentration. As the unsuspecting, free-moving water molecules cross over from A to the other side (B), they become hydrogen bonded to the solutes. Soon, the other side (B) contains more hydrogen bonded water molecules. And the volume of water increases on that side. Thus, the body maintains the balance of compartmental fluids by controlling concentrations of ions in each compartment.

Why is BMR measured only after 12 hours of fasting?

To answer this question, let's return to Lesson 4, on carbohydrates. Make a mental list of all the enzymes that are necessary for carbohydrate digestion. How about lipids? Protein? In short, energy must be spent to make chemical digestion of food possible. The anabolic chemical reactions build the enzymes necessary for digestion.

How is the movement of water controlled in the body?

To control the movement of water, the cells direct the movement of major minerals. Most notably sodium, potassium, and magnesium, although chloride, phosphorus, and sulfur also play a role. These minerals, called salts, dissociate when placed in water, becoming ions with either positive or negative charges. Water molecules are immediately drawn to them. These charged ions are called electrolytes.

What is the role of the environment on development?

To convince you of the role that the environment can play on development, let's look at an unlikely example; the maturation of sweat glands. - Babies are born with non-functional sweat glands. These sweat glands will mature over the course of the first year. - The hotter the climate in which the baby is born, the more of these sweat glands become functional. - The colder the climate, the fewer the number of functional adult sweat glands. - Consequently, people with more functional sweat glands have less of a risk of dying from heat stress, because they can cool the body more efficiently.

What happens when you sweat?

Water also participates in chemical reactions. In fact, some of the water in our cells is the product of chemical reactions. This is called metabolic water. The amount of metabolic water produced per day depends on your physical activity level. Physically inactive people produce about 300mL of water per day. Very active people produce about 550mL of water daily. Water also regulates body temperature. During exercise, blood rushes to the surface of the skin, carrying the heat generated from the metabolic reactions in your cells. The blood capillaries near the surface of the skin dilate, allowing more blood to flow through them. This is why you turn red when exercising. this increase in blood flow allows more heat to dissipate, thus cooling down your core. The heat can escape by crossing through the skin and through the sweat glands. Sweat is what allows the body to cool during exercise, But this only works if the sweat is allowed to evaporate. Sweat evaporates similarly to how trees pull water all the way up from the roots to get to the leaves. Water that reaches the leaves comes into contact with the surrounding air. At the air-water interface, water molecules evaporate. As they evaporate, the column of water molecules that stretches all the way down to the roots is pulled up. If the air is saturated with water molecules, as it would be during a very humid day, water does not evaporate, and the column of water does not get pulled up. The same thing happens at the air-water interface of your sweat glands. For warm, interstitial water to be continuously pulled up to the surface of the skin, water molecules need to evaporate. If the air is too humid, the heated body water remains trapped in the body. Consequently, heatstroke can occur, so you can think of your sweat glands as tiny little bonsai trees that move heated interstitial fluid out of the body.