Anatomy: Chapter 23
Identify and briefly define two eating disorders
Eating disorders are psychological problems that result in inadequate food consumption (anorexia nervosa) or excessive food consumption followed by purging (bulimia).
Identify the fates of fatty acids
Fatty acids may become a source of energy or a component of triglycerides, glycolipids, phospholipids, prostaglandins, cholesterol, and steroids
What hormone inhibits the satiety center and stimulates appetite in the short term?
Ghrelin, a hormone secreted by the gastric mucosa when the stomach is not full, inhibits the satiety center and stimulates appetite
What two coenzymes transfer hydrogen atoms to the electron transport system?
Hydrogen atoms are transferred to the electron transport system by way of the coenzymes NAD and FAD
Describe the role that hydrogen ion channels play in the generation of ATP
Hydrogen ion channels are the passageways for the diffusion of hydrogen ions from the inner membrane space of the mitochondria to the matrix. This movement of hydrogen ions powers the production of ATP by ATP synthase.
Describe the source of intestinal gas
Intestinal gas, or flatus, is generated by bacterial activities in the colon when indigestible carbohydrates stimulate bacterial gas production
What heat transfer process accounts for about 1/2 of a person's heat loss while indoors?
Radiation accounts for about 1/2 of a person's heat loss indoors
If vitamins do not provide a source of energy, what is their role in nutrition?
Vitamins play an important role in metabolic pathways by serving as coenzymens
How might a lack of neruopeptide Y in the hypothalamus affect the control of appetite?
a lack of neuropeptide Y, a hypothalamic neurotransmitter, would probably decrease appetite because it normally stimulates the feeding center
Define beta-oxidation
fatty acid catabolism that produces molecules of acetyl-CoA
How is heat loss different between conduction and convection?
Conduction is the direct transfer of heat through physical contact. Convection is heat loss to the cooler air in contact with the skin. The air warmed by the skin rises and it is repeatedly replaced by cooler air until there is no difference in temperature.
Where does most nutrient absorption occur?
small intestine, primarily jejunum
Predict the effect of peripheral vasodilation on a person's body temperature
the vasodilation of peripheral vessels would increase blood flow to the skin and thus the amount of heat the body can lose. As a result, body temperature would decrease.
Define balanced diet
A balanced diet contains all the ingredients needed to maintain homeostasis and prevent malnutrition.
Distinguish between a complete protein and an incomplete protein
A complete protein meets the body's amino acid requirements; an incomplete protein is deficient in one or more of the essential amino acids
Explain why glycolysis is important in cellular metabolism
ATP produced anaerobically through glycolysis is important during peak levels of physical activity, in red blood cells, or when a tissue is temporarily deprived of oxygen
What is basal metabolic rate?
Basal metabolic rate is the minimum resting energy expenditure of an awake, alert person
Explain why carbohydrates are preferred over proteins and lipids as an energy source
Carbohydrates are the preferred energy source because proteins and lipids are more important as structural components of cells and tissues
Distinguish between catabolism and anabolism
Catabolism is the breakdown of organic substrates in the body, whereas anabolism is the synthesis of new organic molecules
Why do cells engage in catabolism?
Cells carry out catabolism to release energy for use in cell growth, cell division, and tissue-specific activities
Why do cells make new compounds?
Cells make new compounds to maintain and repair structures, to support growth, and to build up nutrient reserves
Name the heat conservation mechanism that conducts heat from deep arteries to adjacent deep veins in the limbs
Counter current exchange is the heat conservation mechanism that results in the conduction of heat from deep arteries to adjacent deep veins in the limbs
Where are the cytochromes located in a mitochondrion?
Cytochromes are embedded in the inner mitochondrial membrane
Why is digestion important?
Digestion is important because cells throughout the body rely on the organic molecules from the food we eat for energy production and to replenish the intracellular nutrient pool
How do the absorptive and post absorptive states maintain normal blood glucose levels?
During the absorptive state, insulin prevents a large surge in blood glucose after a meal by stimulating the liver to remove glucose from the circulation. During the post absorptive state, blood glucose begins to decrease, triggering the release of glucagon, which stimulates the liver to release glucose into the circulation.
When and how do ketone bodies form?
Ketone bodies form during the post absorptive state when lipids and amino acids are broken down in the liver. The increased concentration of acetyl-CoA that results from their breakdown forms ketone bodies. Ketone bodies are not catabolized by liver cells, and they diffuse into the circulation.
Describe leptin and its effect on appetite
Leptin is a peptide hormone produced by adipose tissue during the synthesis of triglycerides. It stimulates the satiety center and suppresses appetite.
Describe the roles of LDL and HDL
Low density lipoproteins deliver cholesterol to body tissues, and high density lipoproteins absorb unused cholesterol from body tissues, returning it to the liver where it may be packaged into new LDLs or excreted with bile salts in bile
Explain the process of metabolic turnover
Metabolic turnover is the process in which cells continuously break down and replace all their organic components except DNA
Compare metabolism with cellular metabolism
Metabolism refers to all the chemical reactions that occur in an organism. Cellular metabolism refers to the chemical reactions within cells
What is the difference between a micelle and a chylomicron?
Micelles are lipid-bile salt complexes (containing fatty acids, glycerol, and monoglycerides) formed in the intestinal lumen. Chylomicrons are lipoproteins formed in intestinal epithelial cells and contain newly synthesized triglycerides, cholesterol, and other lipids surrounded by phospholipids and proteins.
Identify when most of the CO2 is released during the complete catabolism of glucose
Most (two-thirds) of the CO2 released in the complete catabolism of glucose occurs during the citric acid cycle
Describe the role of nonshivering thermogenesis in regulating body temperature
Nonshivering thermogenesis involves the release of hormones that increase the metabolic activity of all tissues, resulting in an increase in body temperature.
Define nutrition
Nutrition is the absorption of nutrients from food
Define oxidative phosphorylation
Oxidative phosphorylation is the generation of ATP within mitochondria in a reaction sequence that requires coenzymes and consumes oxygen
Briefly describe phenylketonuria (PKU)
PKU is an inherited metabolic disorder resulting from an inability to convert phenylalanine to tyrosine
Define protein deficiency disease and cite an example
Protein deficiency diseases are nutritional disorders resulting from a lack of one or more essential amino acids. Kwashiorkor is an example of a protein deficiency disease.
Define absorptive state and post absorptive state
The absorptive state, lasting about 4 hours, is the period following a meal, when nutrient absorption is under way. The post absorptive state, lasting about 12 hours, is the period when nutrient absorption is not under way and the body relies on internal energy reserves to meet demands.
Identify the processes by which the amino group is removed
The amino group is removed by deamination or transamination.
What happens to the ammonium ions that are removed from amino acids during deamination
The ammonium ions combine with carbon dioxide to form urea (in the urea cycle), which is ultimately excreted in the urine.
Describe the role of CCK release and its effects on proteins
The arrival of acidic chyme in the duodenum triggers the release of CCK, which stimulates the production and release of inactive pancreatic proenzymes. Enteropeptidase, released from the duodenum converts the pancreatic proenzyme trypsinogen into the proteolytic enzyme, trypsin. Trypsin then converts other proenzymes to yield chymotrypsin, carboxypeptidase, and elastase. Each of these enzymes attacks peptid bonds that link specific amino acids while ignoring others. As a result, they break down proteins into a mixture of dipeptides, tripeptides, and amino acids.
Of these three- carbohydrates, lipids, or proteins - which releases the greatest amount of energy per gram during catabolism?
The catabolism of lipids releases the greatest amount of energy per gram.
Briefly describe the citric acid cycle and explain its role
The citric acid cycle is the reaction sequence that occurs in the matrix of mitochondria. In the process, organic molecules are broken down, carbon dioxide molecules are released, and hydrogen atoms are transferred to coenzymes that deliver them to the electron transport system
What molecule forms the common substrate for the citric acid cycle?
The common substrate for the citric acid cycle in mitochondria is the 2-carbon molecule of acetate, CH3COO-, which is attached to coenzyme A to form acetyl-CoA
What does the liver do with the chylomicrons it receives?
The liver absorbs chylomicrons, removes the triglycerides, combines the cholesterol from the chylomicron with recycled cholesterol, and alters the surface proteins. Newly synthesized complexes are released into the bloodstream as low density lipoproteins (LDLs) or very low density lipoproteins (VLDLs).
Define nutrient pool
The nutrient pool within a cell includes all the organic substrates in the cytosol that are available for anabolism or catabolism
List the molecular products from a glucose molecule after glucolysis
The products are two molecules each of pyruvate, ATP, and NAD H
Define energetics
The study of the flow of energy and its change from one form to another
Identify the two classes of vitamins
The two classes of vitamins are fat-soluble vitamins and water-soluble vitamins
What molecule plays a key reactant role in both ATP production from fatty acids and lipogenesis
acetyl-CoA
Most of the absorbed nutrients enter into which blood vessel?
branch of the hepatic portal vein and are transported to the liver
Explain the role of glycogen in cellular metabolism
glycogen is synthesized from excess glucose molecules by liver and muscle cells, and serves as an intracellular glucose reserve
Define insensible perspiration
the evaporation of water from the skin and alveolar surfaces of the lungs
Define thermoregulation?
the homeostatic control of body temperature
