Chapter 25 Flashcards
(112 cards)
1
Q
Metabolism
A
Refers to all of the chemical reactions that occur in the body.
2
Q
What are the two types of metabolism? Describe them:
A
- Catabolism: chemical reactions that break down complex organic molecules into simpler ones. Are exergonic (produce more energy than they consume).
- Anabolism: chemical reactions that combine simple molecules and monomers to form the body’s complex structural and functional components. Are endergonic (consume more energy than they produce)
3
Q
ATP (adenosine triphosphate)
A
The molecule that participates most often in energy exchanges in living cells. Couples energy-releasing catabolic reactions to energy-requiring anabolic reactions. “Energy currency” of a living cell. A typical cell has about a billion molecules of ATP, each of which typically last less than a minute before being used.
4
Q
What is the energy released in catabolism used for?
A
About 40% of the energy released in catabolism is used for cellular functions; the rest is converted to heat, some of which helps maintain normal body temperature.
5
Q
Oxidation
A
The removal of electrons from an atom or molecule; the result is a decrease in the potential energy of the atom or molecule. Because most biological oxidation reactions involve the loss of hydrogen atoms, they are called dehydrogenation reactions.
6
Q
Reduction
A
The opposite of oxidation; it is the addition of electrons to a molecule. Reduction results in an increase in the potential energy of the molecule.
7
Q
What two coenzymes are commonly used by animal cells to carry hydrogen atoms to another compound after a substance is oxidized?
A
- Nicotinamide adenine dinucleotide (NAD) (a derivative of the B vitamin niacin)
- Flavin adenine dinucleotide (FAD) (a derivative of vitamin B2 (riboflavin))
8
Q
Oxidation–reduction (redox reactions)
A
Oxidation and reduction reactions are always coupled; each time one substance is oxidized, another is simultaneously reduced. In these reactions, oxidation is usually exergonic.
9
Q
Phosphorylation
A
The addition of a phosphate group to a molecule. Increases its potential energy.
10
Q
What three mechanisms of phosphorylation do organisms use to generate ATP?
A
- Substrate-level phosphorylation
- Oxidative phosphorylation
- Photophosphorylation
11
Q
Electron transport chain
A
A series of electron acceptors. Oxidative phosphorylation removes electrons from inorganic compounds and passes them through the electron transport chain to molecules of O2.
12
Q
What are the four ways that glucose can be used?
A
- ATP production
- Amino acid synthesis
- Glycogen synthesis
- Triglyceride synthesis
13
Q
Glycogenesis
A
Synthesis of glycogen from glucose.
14
Q
Lipogenesis
A
Synthesis of triglycerides.
15
Q
How does glucose get moved into cells?
A
Get moved by gluT molecules, which are a family of transporters that bring glucose into cells via facilitated diffusion. A high level of insulin increases the insertion of one type of GluT, called GluT4, into the plasma membranes of most body cells, thereby increasing the rate of facilitated diffusion of glucose into cells. In neurons and hepatocytes, however, another type of GluT is always present in the plasma membrane, so glucose entry is always “turned on.” On entering a cell, glucose becomes phosphorylated. Because GluT cannot transport phosphorylated glucose, this reaction traps glucose within the cell.
16
Q
Glucose catabolism
A
Complete oxidation of glucose (cellular respiration) is chief source of ATP in cells; consists of glycolysis, Krebs cycle,
and electron transport chain. Complete oxidation of 1 molecule of glucose yields maximum of 30 or 32 molecules
of ATP.
17
Q
Cellular respiration
A
The oxidation of glucose to produce ATP.
18
Q
What four sets of reactions does cellular respiration involve?
A
- Glycolysis
- Formation of acetyl coenzyme A
- Krebs cycle reactions
- Electron transport chain reactions
19
Q
What is the difference between aerobic and anaerobic?
A
- Aerobic: with oxygen.
- Anaerobic: without oxygen.
20
Q
Does glycolysis occur under aerobic or anaerobic conditions?
A
Glycolysis does not require oxygen, so it can occur under either aerobic or anaerobic conditions.
21
Q
Aerobic respiration
A
What the reactions of the Krebs cycle and electron transport chain are referred to as since they require oxygen.
22
Q
Anaerobic glycolysis
A
When glycolysis occurs by itself under anaerobic conditions.
23
Q
Glycolysis (step one in cellular respiration)
A
Occurs in cytosol. Conversion of glucose into pyruvic acid results in production of some ATP. Reactions do not require oxygen.
24
Q
What happens to pyruvic acid when oxygen is plentiful versus when oxygen scarce?
A
When oxygen is plentiful, pyruvic acid enters mitochondria, is converted to acetyl coenzyme A, and enters the Krebs cycle (aerobic pathway). When oxygen is scarce, most pyruvic acid is converted to lactic acid via an anaerobic pathway.
25
Formation of acetyl coenzyme A (step two in cellular respiration)
Occurs in mitochondria. A transition step that prepares pyruvic acid for entrance into the Krebs cycle. This step also produces energy-containing NADH + H+ plus carbon dioxide (CO2).
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Coenzyme A (CoA)
Used in the transition step between glycolysis and the Krebs cycle in cellular respiration.
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Acetyl group
A 2-carbon fragment that pyruvic acid get converted into when a molecule of CO2 is removed from it.
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Decarboxylation
A substance that removes CO2 from pyruvic acid, which converts it into an acetyl group.
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Acetyl coenzyme A
A molecule produced by an acetyl group attaching to coenzyme A.
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Krebs cycle reactions (citric acid cycle) (step three in cellular respiration)
Occurs in mitochondria. Cycle includes series of oxidation–reduction reactions in which coenzymes (NAD+ and FAD) pick up hydrogen ions and hydride ions from oxidized organic acids; some ATP produced. CO2 and H2O are by-products. Reactions are aerobic.
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Electron transport chain reactions (step four in cellular respiration)
Occurs in mitochondria. Third set of reactions in glucose catabolism: another series of oxidation–reduction reactions, in which electrons are passed from one carrier to next; most ATP produced. Reactions require oxygen (aerobic cellular respiration).
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Chemiosmosis
In chemiosmosis, ATP is produced when hydrogen ions diffuse back into the mitochondrial matrix.
33
What five types of molecules and atoms serve as electron carriers?
1. Flavin mononucleotide (FMN)
2. Cytochromes
3. Iron-sulfur (Fe-S) centers
4. Copper (Cu) atoms
5. Coenzyme Q (Q)
34
What is the summary of cellular respiration
23-25 ATP molecules from the ten molecules of NADH + H+, 3 ATP molecules from the two molecules of FADH2, 2 ATP molecules from glycolysis, and 2 ATP molecules from the Krebs cycle. A total of 30-32 ATP molecules are generated for each molecule of glucose catabolized during cellular respiration.
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Glucose anabolism
Some glucose is converted into glycogen (glycogenesis) for storage if not needed immediately for ATP production. Glycogen can be reconverted to glucose (glycogenolysis). Conversion of amino acids, glycerol, and lactic acid into glucose is called gluconeogenesis.
36
Glycogen
A polysaccharide that is the only stored form of carbohydrate in the body. If glucose is not needed immediately for ATP production, it combines with many other molecules of glucose to form glycogen.
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Glycogenesis
The synthesis of glycogen. Carried out by hepatocytes and skeletal muscles cells, which are stimulated by insulin from pancreatic beta cells.
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Glycogenolysis
The process of splitting glycogen into its glucose subunits. Stimulated by glucagon and epinephrine.
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Gluconeogenesis
The process by which glucose is formed from noncarbohydrate sources, such as triglycerides, lactic acid, and certain amino acids (think neo = "new"ly formed). Stimulated by cortisol and glucagon
40
Lipids
Are nonpolar and therefore very hydrophobic molecules. Don't dissolve easily in water (Eg. Triglycerides).
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Lipoproteins
"Transport vehicles". Lipid and protein combinations - spherical particles with an outer shell of proteins, phospholipids, and cholesterol molecules surrounding an inner core of triglycerides and other lipids. Since lipids aren't water soluble on their own, they get combined with proteins so that they can be transported in the blood.
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Apoproteins (apo)
Proteins in the outer shell of lipoproteins. Designated by the letters A, B, C, D, and E, plus a number. In addition to helping solubilize the lipoprotein in body fluids, each apoprotein has a specific function.
43
What are the four major classes of lipoproteins? Describe them:
1. Chylomicrons: transport dietary (ingested) lipids to adipose tissue for storage.
2. Very-low-density lipoproteins (VLDLs): contain mainly endogenous (made in body) lipids.
3. Low-density lipoproteins (LDLs): carry 75% of the total cholesterol in blood and deliver it to cells throughout the body. Contains the "bad" cholesterol.
4. High-density lipoproteins (HDLs): remove excess cholesterol from body cells and the blood and transport it to the liver for elimination. Contains the "good" cholesterol.
44
What are the two sources of cholesterol in the body?
1. Foods (some)
2. Hepatocytes (most)
45
What are the two essential fatty acids that the body cannot synthesize?
1. Linoleic acid
2. Linolenic acid
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Triglyceride catabolism
Amino acids are oxidized via Krebs cycle after deamination. Ammonia resulting from deamination is converted into urea in liver, passed into blood, and excreted in urine. Amino acids may be converted into glucose (gluconeogenesis), fatty acids, or ketone bodies.
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Lipolysis
Splitting triglycerides into glycerol and fatty acids, so that muscle, liver, and adipose tissue can oxidize the fatty acids to produce ATP. Stimulated by Epi, NE, and cortisol.
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Lipases
Enzyme that catalyzes lipolysis (Eg. Epi and NE, which are released when sympathetic tone increases. This can occur, for example, during exercise).
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Beta oxidation
A series of reactions that are the first stage in fatty acid catabolism. Occurs in the mitochondria.
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Ketone bodies
Acetoacetic acid (made from combining two acetyl CoA molecules), beta-hydroxybutyric acid (what some acetoacetic acid gets converted to), and acetone (what some acetoacetic acid gets converted to). Freely diffuse through plasma membranes and can leave hepatocytes and enter the bloodstream.
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Ketongenesis
Formation of acetoacetic acid, beta-hydroxybutyric acid, and acetone.
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Triglyceride anabolism
Synthesis of triglycerides from glucose and fatty acids is called lipogenesis. Triglycerides are stored in adipose tissue.
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Lipogenesis
Synthesis of lipids. Liver cells and adipose cells can synthesize lipids from glucose or amino acids. Stimulated by insulin.
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Proteins
Broken down into amino acids. Not stored like carbohydrates and triglycerides - instead are either oxidized to produce ATP or used to synthesize new proteins for body growth and repair.
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Protein catabolism
Amino acids are oxidized via Krebs cycle after deamination. Ammonia resulting from deamination is converted into urea in liver, passed into blood, and excreted in urine. Amino acids may be converted into glucose (gluconeogenesis), fatty acids, or ketone bodies.
56
Deamination
Process in which an amino acids amino group (NH2) gets removed. This must happen before amino acids can enter the Krebs cycle. Deamination occurs in the hepatocytes and produces ammonia (NH3), which then gets converted into urea, and excreted in the urine.
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Protein anabolism
Protein synthesis is directed by DNA and utilizes cells’ RNA and ribosomes.
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Essential amino acids
10 of the 20 amino acids in the body. Includes isoleucine, leucine, lysine, methionine, phenylalanine, threonine,
tryptophan, and valine. Must be present in the diet because they cannot be synthesized in the body in adequate amounts.
59
What is the difference between a complete protein and an incomplete protein?
Complete protein: contains sufficient amounts of all essential amino acids (Eg. Beef, fish, poultry, eggs, and milk).
Incomplete protein: does not contain all essential amino acids (Eg. Leafy green vegetables, legumes (beans and peas), and grains).
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Nonessential amino acids
Can be synthesized by body cells.
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Transamination
The transfer of an amino group from an amino acid to pyruvic acid or to an acid in the Krebs cycle. Form nonessential amino acids.
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What three molecules play a pivotal role in metabolism?
1. Glucose 6-phosphate
2. Pyruvic acid
3. Acetyl coenzyme A
63
Shortly after glucose enters the body, a kinase converts it to glucose-6-phosphate. What are the four possible fates for glucose-6-phosphate?
1. Synthesis of glycogen.
2. Release of glucose into the bloodstream.
3. Synthesis of nucleic acids.
4. Glycolysis.
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Each 6-carbon molecule of glucose that undergoes glycolysis yields two 3-carbon molecules of pyruvic acid. This molecule, like glucose 6-phosphate, stands at a metabolic crossroads: Given enough oxygen, the aerobic (oxygen-consuming) reactions of cellular respiration can proceed; if oxygen is in short supply, anaerobic reactions can occur. What are the four possible fates for pyruvic acid?
5. Production of lactic acid.
6. Production of alanine.
7. Gluconeogenesis
8. Acetyl coenzyme A
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When the ATP level in a cell is low but oxygen is plentiful, most pyruvic acid streams toward ATP-producing reactions - the Krebs cycle and electron transport chain-via conversion to
acetyl coenzyme A. What are the two possible fates for acetyl coenzyme A?
9. Entry into the Krebs cycle.
10. Synthesis of lipids.
66
What is the difference between the absorptive state and postabsorptive state?
Absorptive state: ingested nutrients are entering the bloodstream, and glucose is readily available for ATP production.
Postabsorptive state: absorption of nutrients from the GI tract is complete, and energy needs must be met by fuels already in the body.
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What are the seven absorptive state reactions?
1. Catabolism of glucose.
2. Catabolism of amino acids.
3. Protein synthesis.
4. Catabolism of few dietary lipids.
5. Glycogenesis.
6. Lipogenesis.
7. Transport of triglycerides from liver to adipose tissue.
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Nutrient stores
What excess absorbed nutrients get converted into. Mainly glycogen and fat.
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Glucose transporter (GluT) molecules
A family of transporters that bring glucose into cells via facilitated diffusion.
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What is the location(s) and main stimulating hormone(s) of the process of facilitated diffusion of glucose into cells?
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What is the location(s) and main stimulating hormone(s) of the process of active transport of amino acids into cells?
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What is the location(s) and main stimulating hormone(s) of the process of glycogenesis (glycogen synthesis)?
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What is the location(s) and main stimulating hormone(s) of the process of protein synthesis?
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What is the location(s) and main stimulating hormone(s) of the process of lipogenesis (triglyceride synthesis)?
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What are the nine postabsorptive state reactions?
1. Glycogenolysis in the liver.
2. Glycogenolysis in muscle.
3. Lipolysis.
4. Protein catabolism.
5. Gluconeogenesis.
6. Catabolism of fatty acids.
7. Catabolism of lactic acid.
8. Catabolism of amino acids.
9. Catabolism of ketone bodies.
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Glucose sparing
Means that most body cells switch to other fuels besides glucose as their main source of energy, leaving more glucose in the blood for the brain and red blood cells.
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What is the location(s) and main stimulating hormone(s) of the process of glycogenolysis (glycogen breakdown)?
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What is the location(s) and main stimulating hormone(s) of the process of lipolysis (triglyceride breakdown)?
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What is the location(s) and main stimulating hormone(s) of the process of protein breakdown?
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What is the location(s) and main stimulating hormone(s) of the process of gluconeogenesis (synthesis of glucose from noncarbohydrates)
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What is the difference between fasting and starving?
Fasting: going without food for many hours or a few days.
Starvation: weeks or months of food deprivation or inadequate food intake.
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Energy balance
The precise matching of energy intake (in food) to energy expenditure over time.
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Calorie (cal)
The amount of energy in the form of heat required to raise the temperature of 1 gram of water 1°C.
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Kilocalorie (kcal) (Calorie (Cal))
Used to express the energy content of foods. A kilocalorie equals 1000 calories. So when we say that a particular food item contains 500 Calories, we are actually referring to kilocalories.
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Metabolic rate
The overall rate at which metabolic reactions use energy.
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What seven factors affect the metabolic rate?
1. Hormones
2. Exercise
3. Nervous system
4. Body temperature
5. Ingestion of food
6. Age
7. Other factors (gender, climate, sleep, and malnutrition)
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Calorigenic effect
The effect of thyroid hormones on basal metabolic rate (BMR).
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Food-induced thermogenesis
The ingestion of food raises the metabolic rate 10–20% due to the energy “costs” of digesting, absorbing, and storing nutrients. This effect is greatest after eating a high-protein meal and is less after eating carbohydrates and lipids.
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Basal state
Standard conditions, with the body in a quiet, resting, and fasting condition.
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Basal metabolic rate (BMR)
The measurements obtained under the basal state.
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Total metabolic rate (TMR)
The total energy expenditure by the
body per unit of time.
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What three components contribute to the total metabolic rate (TMR)?
1. Basal metabolic rate (BMR)
2. Physical activity
3. Food-induced thermogenesis
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Nonexercise activity thermogenesis (NEAT)
The energy costs for maintaining muscle tone, posture while sitting or standing, and involuntary fidgeting movements.
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Satiety
A feeling of fullness accompanied by lack of desire to eat.
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Leptin
Helps decrease adiposity, total body-fat mass. Leptin is synthesized and secreted by adipocytes in proportion to adiposity; as more triglycerides are stored, more leptin is secreted into the bloodstream. Leptin acts on the hypothalamus to inhibit circuits that stimulate eating while also activating circuits that increase energy expenditure.
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Neuropeptide Y
Neurotransmitter that stimulates food intake.
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Melanocortin
Neurotransmitter that acts to inhibit food intake.
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Ghrelin
Hormone which plays a role in increasing appetite. Produced
by endocrine cells of the stomach.
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Heat
A form of energy that can be measured as temperature. Body maintains a constant core temperature near 37°C (98.6°F).
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What is the difference between core temperature and shell temperature?
Core temperature: the temperature in body structures deep to the skin and subcutaneous layer.
Shell temperature: the temperature near the body surface - in the skin and subcutaneous layer.
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What four ways can heat be transferred between the body and its surroundings? Briefly describe them:
1. Conduction: is the heat exchange that occurs between molecules of two materials that are in direct contact with each other.
2. Convection: is the transfer of heat by the movement of air or water between areas of different temperatures.
3. Radiation: is the transfer of heat in the form of infrared rays between a warmer object and a cooler one without physical contact.
4. Evaporation: is the conversion of a liquid to a vapor.
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Insensible water loss
What water loss through the skin and mucous membranes of the mouth and respiratory system is referred to as, since we are normally not aware of it.
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Heat-losing center and the
heat-promoting center
Get stimulated by the preoptic area and set into operation a series of responses that lower body temperature and raise body temperature, respectively.
104
What four ways does the body respond to increase the core temperature to the normal value through negative feedback mechanisms?
1. Vasoconstriction
2. Release of Epi and NE
3. Shivering
4. Release of thyroid hormones
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Shivering
Skeletal muscles contract in
repetitive cycle.
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Nutrients
Chemical substances in food that body cells use for growth, maintenance, and repair. The six main types of nutrients
are water, carbohydrates, lipids, proteins, minerals, and vitamins.
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Essential nutrients
Specific nutrient molecules that the body cannot make in sufficient quantity to meet its needs and thus must be obtained from the diet. Some amino acids, fatty acids, vitamins, and minerals are essential nutrients.
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Minerals
Inorganic elements that occur naturally in the earth’s crust. In the body they appear in combination with one another, in combination with organic compounds, or as ions in solution. Minerals constitute about 4% of total body mass and are concentrated most heavily in the skeleton. Minerals with known functions in the body include calcium, phosphorus, potassium, sulfur, sodium, chloride, magnesium, iron, iodide, manganese, copper, cobalt, zinc, fluoride, selenium, and chromium.
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Vitamins
Organic nutrients required in small amounts to maintain growth and normal metabolism. Unlike carbohydrates, lipids, or proteins, vitamins do not provide energy or serve as the body’s building materials. Most vitamins with known functions are coenzymes. Most, but not all, vitamins cannot be synthesized by the body and must be ingested in food.
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Provitamins
Raw materials of vitamins, which the body can use to assemble vitamins.
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What are the two main groups of vitamins? Describe them:
1. Fat-soluble vitamins: vitamins A, D, E, and K; are absorbed along with other dietary lipids in the small intestine and packaged into chylomicrons. They cannot be absorbed in adequate quantity unless they are ingested with other lipids.
2. Water-soluble vitamins: several B vitamins and vitamin C; may be stored in cells, particularly hepatocytes. Are dissolved in body fluids. Excess quantities of these vitamins are not stored but instead are excreted in the urine.
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Antioxidant vitamins
Vitamins C, E, and beta-carotene (a provitamin); inactivate oxygen free radicals. Protect against some kinds of cancer, reduce the buildup of atherosclerotic plaque, delay some effects of aging, and decrease the chance of cataract formation in the lens of the eyes.
