chapter 23

Catabolizing fatty acids by beta-oxidation results in the formation of what product?

Acetyl-CoA

What is the term for the direct transfer of heat energy through physical contact?

Conduction

Why is hypervitaminosis involving water-soluble vitamins relatively uncommon?

Excessive amounts of these vitamins are readily excreted in the urine. Unlike fat-soluble vitamins, which are stored in adipose deposits throughout the body, excess quantities of water-soluble vitamins end up in the urine. Since they are not stored in the body, water-soluble vitamins need to be taken regularly. With fat-soluble vitamins, deficiency states could take months to manifest. With water-soluble vitamins, however, deficiency states could manifest within days to weeks of a total absence of any particular vitamin.

What happens to a glucose molecule as a result of the reactions of glycolysis?

Formation of two molecules of pyruvic acid

lipogenesis

The synthesis of lipids is called __________. This process takes place within the smooth endoplasmic reticulum of cells. When the resulting lipid is triglyceride, the most common form of stored energy in the body, this takes place within adipose tissue. The resulting triglyceride is stored as lipid droplets within the adipocytes. In general, lipogenesis is an anabolic series of chemical reactions.

What lipoproteins transport cholesterol to cells of the body? review!!

LDL

What is the primary role of the citric acid cycle in the production of ATP?

Removal of electrons from substrates. In these reactions, the substrate is oxidized and electrons are removed and transferred to coenzymes, like NAD and FAD. During these oxidation reactions, hydrogen atoms and energy are also removed from the substrate and transferred to the coenzymes. The electrons and energy are shuttled to the electron transport chain for production of ATP.

catabolism

The process that breaks down organic substrates, releasing energy that can be used to synthesize ATP or other high-energy compounds, is __________.

Milk and eggs are complete proteins because they contain __________.

all the essential amino acids in sufficient quantities

In the nutrient pool, which chemical is best suited for storage of energy content?

fatty acids. Most cells prepare for those times when nutrients in the bloodstream are inadequate. This is certainly true of energy reserves. Because of their energy content, fatty acids are particularly useful as a stored energy source. Fatty acids are regularly converted into triglycerides and stored in adipose tissue for later use.

The most important factor of good nutrition is obtaining nutrients __________.

in sufficient quantities and qualities

Before the large vitamin B12 molecule can be absorbed, it must be bound to __________.

intrinsic factor; protein made in stomach

Beta-oxidation

is a sequence of reactions in which fatty acid molecules are broken down into two-carbon acetyl-CoA fragments. FAD and NAD+ are also reduced. This process takes place inside the mitochondria, so the carbon chains can enter the citric acid cycle as acetyl-CoA.

Lipids circulate through the bloodstream as __________.

lipoproteins and free fatty acids

During the catabolism of glucose, some energy is captured by __________ molecules, while the rest of the energy is lost mainly as ________.

reduced, heat

The electron transport system (ETS)

requires oxygen and electrons to work properly. The electrons are provided by coenzymes during oxidation reactions in other processes and are brought to the ETS by coenzymes like NAD and FAD. Oxygen is supplied to the cells and mitochondria by the respiratory and cardiovascular systems. Oxygen is the final electron acceptor in the ETS. When it accepts those electrons, it is split apart into an oxygen atom with two extra electrons and becomes very reactive. It reacts with the hydrogen ions, brought to the ETS by the coenzymes, and forms a water molecule.

The TCA cycle is also known as either

the Kreb's cycle or citric acid cycle, and takes place inside the mitochondria in the presence of oxygen. The electron transporters, NADH and FADH2 are formed in this process and are used in the ETC to form the bulk of the ATP during oxidative phosphorylation.

glycolysis

the first step in the production of glucose. doesnt require O2. Occurs in the cytosol splits one glucose molecule into two molecules of pyruvate. This step produces only a net result of 2 ATPs and is done without the need for oxygen. After this step, all subsequent steps are dependent on the presence of oxygen. All these aerobic reactions take place within the cristae of the mitochondria

The first step in the sequence of enzymatic reactions in the tricaboxylic acid (TCA) cycle is

the formation of citric acid.

For each glucose molecule converted to two pyruvates, the anaerobic reaction sequence in glycolysis provides a net gain of __________

2 atp for the cell. For each glucose molecule converted to two pyruvates, the anaerobic reaction sequence in glycolysis provides a net gain of two ATP for the cell. This initial step of glycolysis takes place in the cytosol and releases only a small part of the total energy inside the glucose molecule. To liberate the maximum amount of energy from glucose, oxygen is required in a series of aerobic reactions that take place inside the mitochondria. Most of this ATP is produced during the last part of the aerobic reactions, which is known as oxidative phosphorylation.

All nutrients can be used by the mitochondria to provide energy. In what form are these nutrients "fed" into the mitochondria?

2 carbon fragments. The mitochondria are picky eaters. They will not accept an intact simple nutrient. Catabolic processes in the cytoplasm must break down these simple nutrients into an acceptable form. The mitochondria will accept two-carbon fragments (like acetyl-CoA) and process them for their energy content.

The basal metabolic rate (BMR) is __________.

70 cal/hr or 1680 cal/day in the average individual

What is meant by the term balanced diet?

A balanced diet supplies all ingredients to maintain homeostasis.

NAD, a key coenzyme used in the process of producing ATP, is produced from which water-soluble vitamin?

Niacin; Niacin is also known as vitamin B3 and forms part of the structure of NAD. Deficiency of niacin, also known as pellagra, can induce dysfunction in the nervous and digestive systems and cause deterioration of epithelia and the skin. Excesses of this water-soluble vitamin can also induce dysfunction, even though most of this vitamin is excreted in the urine if present in excess.

Where in the cell does the electron transport chain occur?

Inner mitochondrial membrane.

What happens to oxygen when it functions as the final electron acceptor in the electron transport system?

It becomes part of a water molecule.

What is a complete protein?

It contains all the essential amino acids. Some of these amino acids can be synthesized by the liver. Others cannot. The amino acids that cannot be synthesized are essential amino acids. A complete protein is one that can supply all the essential amino acids.

What lipoproteins transport cholesterol to cells of the body?

LDL Cholesterol has many vital functions in the body. Peripheral cells use it in the synthesis of plasma membranes, and the production of hormones and other steroid lipids. It is transported to the peripheral cells for their use by low-density lipoproteins (LDL).

What is the primary focus of nutritional processing in the postabsorptive state?

Maintaining blood glucose levels. During the postabsorptive state, there are no usable nutrients in the digestive tract to be absorbed. Levels of nutrients in the blood, like glucose, are falling. To meet the body's needs, nutrients will have to be mobilized from storage. In order to ensure that neural tissue has an adequate supply of glucose, the focus of the postabsorptive state metabolically is to maintain blood glucose levels. Neural tissue is generally unable to metabolize other nutrients. Maintaining the blood glucose level is done by glycogenolysis and gluconeogenesis.

Where in the cell does the citric acid cycle occur?

Mitochondrial matrix

intrinsic factor

a protein made in the stomach epithelium, and its production becomes an issue in older individuals who have conditions such as atrophic gastritis, in which intrinsic factor production declines. When this is the case, vitamin B12 cannot be absorbed from food, and the result is a vitamin B12 deficiency disease known as pernicious anemia, in which red blood cells are no longer formed normally and their function is thus abnormal

Why is it that lipids cannot provide large amounts of adenosine triphosphate (ATP) in a short period of time?

1. Most lipids are processed in mitochondria, and mitochondrial activity depends on the availability of oxygen. 2. Lipids are insoluble in water, and it is thus difficult for water-soluble enzymes to reach them. Lipids are insoluble in water, so they must be emulsified in order for enzymes to reach them 3. Lipid reserves are difficult to mobilize.

Which lipoprotein carries dietary triglycerides to the liver?

Chylomicrons are the largest lipoproteins. About 95 percent of the weight of chylomicrons consists of triglycerides. Phospholipids, steroids, and fat-soluble vitamins are also present. Chylomicrons are produced by intestinal cells and put into the blood by exocytosis. The liver absorbs the chylomicrons and processes the dietary lipids.

Which of the following is NOT a way your body generates or conserves heat?

Decreased metabolic rate. We are constantly in a balance between heat loss and heat gain. If your body becomes cooler than normal, the sympathetic vasomotor center decreases blood flow to the dermis of the skin. This conserves heat by decreasing heat loss by radiation. There will also be a decrease in sweat production, which reduces heat loss by evaporation. These are both mechanisms of conservation of heat. The next thing you would do in your house, if it was cold, is turn up the heat. This is done in your body by shivering, in which the skeletal muscles involuntarily contract and generate heat to warm you. Your body would also produce hormones like epinephrine and thyroxine, which increase the metabolic rate of your body. This would generate heat also. Decreasing the metabolic rate would be opposite of what you need.

Excess cholesterol leaves somatic cells and is absorbed by __________, which then transport the cholesterol back to the liver.

HDLs. Excess cholesterol leaves somatic cells and is absorbed by HDLs, which then transport the cholesterol back to the liver. This lipoprotein category has been termed "good cholesterol" even though HDL is not pure cholesterol. Instead, HDL contains about equal amounts of lipids and proteins, with the lipids being mostly cholesterol and phospholipids. Once the HDL transports excess cholesterol to the liver, the cholesterol can be stored or excreted in bile during the process of fat digestion.

Why are minerals, vitamins, and water classified as essential nutrients?

The body cannot synthesize these nutrients in sufficient quantities.

The production of ATP provides energy to support anabolism as well as other cell functions. Which of the following is NOT supported by energy from ATP?

The diffusion of molecules across the plasma membrane.

energetics

The flow and transformation of energy the making and breaking of chemical bonds to produce ATP. The cellular region where most ATP is made is within mitochondria. Energetics describes a flow in which energy is continually lost because of the inherent inefficiency that is part of the physical universe.

Which vitamin is required for the synthesis of visual pigments?

Vitamin A

The period following a meal when nutrient absorption is underway is _____

absorptive state. This period lasts for about 4 hours and is dominated by hormonal activity which promotes tissue growth. Insulin is the primary hormone which causes uptake of glucose by cells. Other hormones that play a role in creating an anabolic environment include growth hormone, androgens and estrogens.

Which nutrient in the nutrient pool is most often used to replace structural and functional components of the cell?

amino acids

The process in which fatty acids are broken down into two-carbon fragments is __________.

beta-oxidation; this process occurs within the mitochondria and requires the presence of oxygen. l The breakdown of fatty acids yields over twice as much total ATP as that obtained from the breakdown of glucose. This is due to the higher energy density present in lipid and the greater number of chemical bonds when compared to that in carbohydrate.

In resting skeletal muscles, a significant portion of their metabolic demand is met through the __________.

catabolism of fatty acids. This is an example of a tissue shifting between two modes of metabolism, depending on the environmental circumstances. At rest, skeletal muscles derive most of their ATP from the breakdown of fatty acids. During activity, however, skeletal muscles get their supply of ATP from carbohydrates, and supplies of oxygen are also critical factors in skeletal muscle performance.

When blood glucose concentrations are elevated, the glucose molecules can be ________

catabolized for energy, used to build energy reserves, and used for growth and tissue repair.

review: Which lipoprotein carries dietary triglycerides to the liver?

chylomicrons

If the cells are catabolizing amino acids for energy, what is the first step in amino acid catabolism?

deamination When an amino acid is being catabolized for its energy content, the amino group has to be removed. This process is called deamination. The removal of the amino group results in the formation of an organic acid, which is catabolized by cellular metabolism for the production of ATP.

The flow and transformation of energy is called __________.

energetics

What is the term for an amino acid that either cannot be synthesized or is not synthesized in adequate amounts in the body?

essential amino acid

The mechanism of heat loss that involves the skin and alveoli of the lung is _______

evaporation

Which of the following is an important energy source during periods of starvation, when glucose supplies are limited?

free fatty acids. Free fatty acids are a crucial source of energy during periods of starvation, when glucose supplies are limited. During starvation states, glucose reserves in the liver and muscle in the form of glycogen have been depleted. At this point, adipose stores of fatty acids are accessed by freeing up triglyceride. Hydrolysis then breaks down these molecules into glycerol and free fatty acids. These fatty acids are then broken down via beta-oxidation in the mitochondria to generate ATP. The glycerol may enter the citric acid cycle to produce ATP as well.

Which process in the aerobic metabolism of glucose takes place in the cytosol?

glycolysis

Which process in the metabolism of glucose does not require oxygen?

glycolysis (anaerobic). The first step in the breakdown of glucose, glycolysis, does not require oxygen and is not part of aerobic metabolism. The processes that occur in the mitochondria all require the presence of oxygen in the cell.

reactions of glycolysis

happen in the cytoplasm/cytosol. Makes 2 molecules of pyruvate.

The lipoprotein that transports cholesterol to the liver is __________

high-density lipoprotein. The HDL particle transports excess cholesterol from the periphery to the liver for storage or excretion. HDL is sometimes referred to as "good cholesterol" because it takes cholesterol out of blood circulation, where it might otherwise form arterial plaques.

During open-heart surgery, which of the following thermoregulatory changes is induced in the patient's body?

hypothermia; This lowering of body temperature slows down metabolic demands of the organs and tissues and also lowers the metabolic use of oxygen. If the oxygen usage were to increase during this time, so would the damage from oxygen radical production. This oxygen radical production is a natural result of oxygen use during metabolism. By slowing down the metabolic activity of a tissue during surgery, stress on the tissue as well as subsequent damage following the surgery will be minimized.

Which part of the cell is most heavily involved in energetics?

mitochondria. Cells are chemical factories that break down organic molecules to obtain energy. Our cells can use their energy to generate ATP. The cells require oxygen and nutrients to provide this energy. The respiratory system and cardiovascular system provide the oxygen to our cells. The digestive system provides the nutrients. The mitochondria are the organelles in the cell that carry out the chemical reactions that provide the largest quantity of energy to the cell in the form of ATP.

A cell with excess carbohydrates, lipids, and amino acids will break down carbohydrates in order to __________.

obtain energy. Carbohydrates are made up of units of simple sugar, which are composed of chains of carbon atoms along with oxygen and hydrogen. Energy is contained in all chemical bonds, and when the bonds in simple sugars are broken down, this energy is stored in ATP. ATP is the energy currency of all cells, and this energy is stored and released to power all biochemical reactions.

Although small quantities of lipids are normally stored in the liver, most of the synthesized triglycerides are exported and bound to __________.

proteins. These transport aggregates begin in the GI tract as synthesized chylomicrons in intestinal cells. These are the largest of the lipoproteins that are then carried in lacteals to the liver. LDLs and VLDLs are then synthesized in the liver and carried away, while HDLs carry cholesterol back to the liver.

What chemical in the catabolism of glucose enters the mitochondria?

pyruvate

An individual's basal metabolic rate ideally represents __________.

the minimum resting energy expenditure of an awake, alert person This level of energy expenditure represents the metabolic baseline that is required to take care of basic needs, such as production of ATP. This production does not stop until a given cell or tissue turns over or dies. Other basic metabolic needs include the disposal of wastes and the transport of nutrients into cells.

Which vitamin is required for the synthesis of visual pigments?

vitamin A; Vitamin A is the vitamin required for the synthesis of visual pigments, particularly the visual pigment rhodopsin, which is responsible for light detection and vision. Deficiency of vitamin A is a leading cause of blindness in children worldwide. It is also needed for the proper development of tissues as well as the proper functioning of the immune system. Vitamin A is a fat-soluble vitamin found in leafy green, yellow, and orange vegetables and fruits. It is also found in milk, liver, eggs, and some fish.