A&P 2 Ch. 24: Nutrition Metabolism/Energy Balance

Essential nutrient

A nutrient the body cannot make at a speed sufficient to maintain normal growth, maintenance, and repair

In glycolysis, glucose must be activated with the use of how many ATP molecules?

Two

The liver synthesizes about what percent of the cholesterol found in blood?

85% Because the body can synthesize as much cholesterol as it needs, cholesterol is not required in the diet. Many guidelines still recommend keeping cholesterol intake as low as possible. This is particularly important for individuals who already have high total blood cholesterol levels, which have been associated with cardiovascular disease. Cholesterol is a stabilizing component of plasma membranes and is the precursor from which bile salts, steroid hormones, and other important molecules are formed. Unlike triglycerides, cholesterol is not used for energy.

Nutrient

A substance in food the body uses to promote normal growth, maintenance, and repair

Lipids

Act as an accessory fuel; component of membranes

Which of the following is the amount of energy the body needs to maintain life?

BMR (Basal Metabolic Rate) aka "Energy Cost of Living"

Lipolysis

Breakdown of lipids

Proteins

Built of long chains of amino acids

Glycogenesis

The formation of glycogen to store glucose When high ATP levels begin to "turn off" glycolysis, glucose molecules are combined in long chains to form glycogen, the animal carbohydrate storage product. This process is called glycogenesis (glyco = sugar; genesis = origin).

Gluconeogenesis

The process of forming glucose from noncarbohydrate molecules When too little glucose is available to stoke the "metabolic furnace," glycerol and amino acids are converted to glucose. Gluconeogenesis, the process of forming new (neo) glucose from noncarbohydrate molecules, occurs in the liver. Gluconeogenesis takes place when dietary sources and glucose reserves have been used up and blood glucose levels are beginning to drop. Gluconeogenesis protects the body, especially the nervous system, from the damaging effects of low blood sugar (hypoglycemia) by ensuring that ATP synthesis can continue.

What does the term "nitrogen balance" mean?

The rate of protein synthesis equals the rate of protein breakdown and loss. The body is in positive nitrogen balance when the amount of protein incorporated into tissue is greater than the amount being broken down and used for energyn the amount of nitro in growing children and pregnant women. A positive balance also occurs when tissues are being repaired following illness or injury. In negative nitrogen balance, protein breakdown for energy exceeds the amount of protein being incorporated into tissues. This occurs during physical and emotional stress (for example, infection, injury, or burns), when the quality or quantity of dietary protein is poor, or during starvation.

The thermoregulatory centers are located in the __________.

hypothalamus

The hormone that controls essentially all events of the absorptive state is __________.

insulin Insulin directs essentially all events of the absorptive state. After a meal, rising blood glucose and amino acid levels stimulate the beta cells of the pancreatic islets to secrete more insulin. The GI tract hormone glucose-dependent insulinotropic peptide (GIP) and parasympathetic stimulation also promote the release of insulin.

Cyanide acts as a poison by __________.

interfering with the flow of electrons in the electron transport chain

The site of electron transport is the __________.

mitochondrial inner membrane (cristae)

A kilocalorie is the amount of energy __________.

needed to heat 1 kilogram of water 1 degree Celsius The energy value of foods is measured in kilocalories (kcal). One kilocalorie is the amount of heat energy needed to raise the temperature of 1 kilogram of water 1°C (1.8°F). This unit is the "calorie" (C) that dieters count so conscientiously.

Nutritionally incomplete proteins are low in __________.

one or more of the essential amino acids

The final electron acceptor in the electron transport chain is __________.

oxygen

Cori Cycle

the pathway in which glucose is metabolized to lactate in the muscle, lactate is converted back to glucose in the liver, and then glucose is returned to the muscle . (Pyruvates into glucose)

Lipogenesis

triglyceride synthesis that occurs when cellular ATP and glucose levels are high

The final product(s) of glycolysis is (are) __________.

two molecules of pyruvic acid, two molecules of reduced NAD+, and a net gain of two ATP

A major means for conserving heat in the body is __________.

vasoconstriction of cutaneous blood vessels

A function of the liver during the postabsorptive state is __________.

to mobilize glucose reserves by glycogenolysis

Macronutrient

A nutrient that makes up the bulk of what we eat A nutrient is a substance in food the body uses to promote normal growth, maintenance, and repair. The nutrients needed for health divide into five categories. Three of these—carbohydrates, lipids, and proteins—are macronutrients that make up the bulk of what we eat. The fourth and fifth categories, vitamins and minerals, though equally crucial for health, are micronutrients required in only minute amounts.

Nonessential nutrient

A nutrient that the body can make at a speed sufficient to maintain normal growth, maintenance and repair. A nutrient is a substance in food the body uses to promote normal growth, maintenance, and repair. The nutrients needed for health divide into five categories. Three of these—carbohydrates, lipids, and proteins—are macronutrients that make up the bulk of what we eat. The fourth and fifth categories, vitamins and minerals, though equally crucial for health, are micronutrients required in only minute amounts.

Triglycerides

Composed of fatty acids and glycerol There is a continuous turnover of triglycerides in adipose tissue. New fats are stored for later use, and stored fats are broken down and released to the blood. That bulge of fatty tissue you see today does not contain the same fat molecules it did a month ago. Glycerol and fatty acids from dietary fats not immediately needed for energy are recombined into triglycerides and stored. About 50% ends up in subcutaneous tissue, and the balance is stockpiled in other fat depots of the body.

Carbohydrates

Composed of simple sugars; used as the major fuel source for cellular respiration Provide the primary source of fuel for ATP synthesis The monosaccharide glucose is the carbohydrate molecule ultimately used as fuel by body cells to produce ATP. Carbohydrate digestion also yields fructose and galactose, but the liver converts these monosaccharides to glucose before they enter the general circulation.

Which of the following statements about "redox" reactions in human metabolism is correct? A. Enzymes accept hydrogen. B. Oxidized substances gain energy. C. The substance being reduced loses an electron. D. Coenzymes accept hydrogen.

D. Coenzymes accept hydrogen. Most of these enzymes require the help of a specific coenzyme, typically derived from one of the B vitamins. Although the enzymes catalyze the removal of hydrogen atoms to oxidize a substance, they cannot accept the hydrogen (hold on or bond to it). Their coenzymes, however, can act as hydrogen (or electron) acceptors, becoming reduced each time a substrate is oxidized.

Which of the following is the correct description of the Citric acid cycle (or Krebs cycle)? A. Requires ATP synthase at end B. Results in fatty acid chains being broken down C. End product is pyruvic acid D. Fueled largely by pyruvic acid

D. Fueled largely by pyruvic acid The citric acid cycle occurs in the mitochondrial matrix and is fueled largely by pyruvic acid produced during glycolysis and by fatty acids resulting from fat breakdown. Because pyruvic acid is a charged molecule, it must enter the mitochondrion by active transport with the help of a transport protein. Once in the mitochondrion, the first order of business is a transitional phase that converts pyruvic acid to acetyl CoA.

Which of the following describes the function of vitamins?

Function as coenzymes; not used as structural components Vitamins (vita = life) are organic compounds needed in minute amounts for growth and good health. Unlike other organic nutrients, vitamins do not serve as an energy source nor as building blocks, but they are crucial in helping the body use those nutrients that do. Without vitamins, all the carbohydrates, proteins, and fats we eat would be useless.

__________ are considered "good" cholesterol; high blood levels of this cholesterol are thought to be beneficial.

HDLs The major function of HDLs, which are particularly rich in phospholipids and proteins, is to scoop up and transport excess cholesterol from peripheral tissues to the liver, where it is broken down and becomes part of bile. The liver makes the protein envelopes of the HDL particles and then ejects them into the bloodstream in collapsed form, rather like deflated beach balls.

Function of minerals

Incorporated into some body structures; used in conjunction with enzymes Most minerals are ionized in body fluids or bound to organic compounds to form phospholipids, hormones, and various proteins. For example, iron is essential to the oxygen-binding heme of hemoglobin, and sodium and chloride ions are the major electrolytes in blood. The amount of a particular mineral in the body gives very few clues to its importance in body function. For example, just a few milligrams of iodine (required for thyroid hormone synthesis) can make a critical difference to health.

Which of the following describes the function of minerals?

Incorporated into some body structures; used in conjunction with enzymes The body requires moderate amounts of seven minerals (calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium) and trace amounts of about a dozen others. Minerals make up about 4% of the body by weight, with calcium and phosphorus (as bone salts) accounting for about three-quarters of this amount. Minerals, like vitamins, are not used for fuel but work with other nutrients to ensure a smoothly functioning body. Incorporating minerals into structures makes them stronger. For example, calcium, phosphorus, and magnesium salts harden the teeth and strengthen the skeleton.

Which lipoprotein contains high levels of cholesterol?

LDL

Which of the following describes the products of glycolysis?

Produces two molecules of pyruvic acid, four ATP, and two NADH + H+ The final products of glycolysis are two molecules of pyruvic acid and two molecules of reduced NAD+ (which is NADH + H+). There is a net gain of two ATP molecules per glucose molecule. Four ATPs are produced, but remember that two are consumed in phase 1 to "prime the pump." Between them the two pyruvic acid molecules have lost four hydrogen atoms, whose electrons are now bound to two molecules of NAD+. NAD carries a positive charge (NAD+), so when it accepts a hydrogen pair, NADH + H+ is the resulting reduced product. Although a small amount of ATP has been harvested, the other two products of glucose oxidation (H2O and CO2) have yet to appear.

Glycogenolysis

The cleavage of glycogen to release glucose When blood glucose levels drop, glycogen lysis (splitting) occurs. This process is known as glycogenolysis. The enzyme glycogen phosphorylase oversees phosphorylation and splitting of glycogen to release glucose-1-phosphate, which is then converted to glucose-6-phosphate, a form that can enter the glycolysis pathway to be oxidized for energy.

Which of the following is the correct description of glycogenesis?

The formation of glycogen to store glucose When high ATP levels begin to "turn off" glycolysis, glucose molecules are combined in long chains to form glycogen, the animal carbohydrate storage product. This process is called glycogenesis (glyco = sugar; genesis = origin).

Oxidative phosphorylation

The production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration. Requires ATP synthase at end The only areas of the mitochondrial membrane freely permeable to H+ are large enzyme-protein complexes (complex V) called ATP synthases. These complexes, which populate the inner mitochondrial membrane, lay claim to being nature's smallest rotary motors. This motor drives a molecular mill that "grinds" ADP and Pi together into ATP. As the protons flow through, they bind to a subunit of the rotor, causing it to change shape and forcing the rotor to spin. The spinning rotor turns a connecting rod within a stationary knob. This mechanical action catalyzes the formation of ATP.

Micronutrients

Vitamins and minerals A nutrient is a substance in food the body uses to promote normal growth, maintenance, and repair. The nutrients needed for health divide into five categories. Three of these—carbohydrates, lipids, and proteins—are macronutrients that make up the bulk of what we eat. The fourth and fifth categories, vitamins and minerals, though equally crucial for health, are micronutrients required in only minute amounts.

As proteins are broken down for energy, __________ is generated; the liver then converts this potentially toxic intermediate into __________.

ammonia; urea As proteins are broken down for energy, ammonia is generated; the liver then converts this potentially toxic intermediate into urea.

In the postabsorptive state, __________.

glycogen is broken down to release glucose So where does blood glucose come from in the post-absorptive state? Sources include stored glycogen in the liver and skeletal muscles, tissue proteins, and, in limited amounts, fats. The liver's glycogen stores are the first line of glucose reserves. They are mobilized quickly by glycogenolysis and can maintain blood sugar levels for about four hours during the post-absorptive state.

In the absorptive state, __________.

insulin serves as the main regulatory hormone Insulin directs essentially all events of the absorptive state. After a meal, rising blood glucose and amino acid levels stimulate the beta cells of the pancreatic islets to secrete more insulin. The GI tract hormone glucose-dependent insulinotropic peptide (GIP) and parasympathetic stimulation also promote the release of insulin.

Most of the ATP produced during cellular respiration is produced by __________.

oxidative phosphorylation during the chemiosmotic process How do our cells capture some of the energy liberated during cellular respiration to make ATP molecules? There are two mechanisms: substrate-level phosphorylation and oxidative phosphorylation. Substrate-level phosphorylation occurs when high-energy phosphate groups are transferred directly from phosphorylated substrates (metabolic intermediates such as glyceraldehyde 3-phosphate) to ADP. Essentially, this process occurs because the high-energy bonds attaching the phosphate groups to the substrates are even more unstable than those in ATP. ATP is synthesized by this route twice during glycolysis, and once during each turn of the citric acid cycle. The enzymes catalyzing substrate-level phosphorylations are located in both the cytosol (where glycolysis occurs) and in the watery matrix inside the mitochondria (where the citric acid cycle takes place). Oxidative phosphorylation is more complicated, but it also releases most of the energy that is eventually captured in ATP bonds during cellular respiration. Oxidative phosphorylation, which is carried out by electron transport proteins embedded in the inner mitochondrial membranes, is an example of a chemiosmotic process. Chemiosmotic processes couple the movement of substances across membranes to chemical reactions.

The hormone responsible for setting the basal metabolic rate is __________.

thyroxine The amount of thyroxine produced by the thyroid gland is probably the most important hormonal factor in determining BMR. For this reason, thyroxine has been dubbed the "metabolic hormone." Its direct effect on most body cells (except brain cells) is to increase O2 consumption and heat production, in part by accelerating the use of ATP to operate the sodium-potassium pump. As ATP reserves decline, cellular respiration accelerates. Thus, the more thyroxine produced, the higher the BMR.