Chapter 26: Nutrition and Metabolism

Created by boh1985 

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Ghrelin

this is secreted by parietal cells in the fundus of teh stomach, expecially when the stomach is empty

Peptide YY (PYY)

this is a member of a family of hormones related to neuropeptides Y

Cholecystokinin

is secreted by enteroendocrine cells in the duodenum and jejunum

Leptin

\is secreted by adipocytes throughout the body

Insulin

is secreted by the pancreatic beta cells

Arcuate Nucleus

brain center for appetite regulation

Neuropeptide Y

a potent appetite stimulant

Melanocortin

which inhibits eating

Hunger Contractions

begin soon after the stomach is emptied and increase in intensity over a period of hours

Kilocalorie

in biochemistry

Fuel

is oxidized solely or primarily to extract energy from it

Nutrient

is any ingested chemical that is used for growth, repair or maintenance of the body

Macronutrients

they must be consumed in relatively large quantities

Micronutrients

only small quatities are required

Recommended Daily Allowances (RDAs)

is a liberal but safe estimate of the daily intake that would meet the nutrtional needs of most healthy people

Essential Nutrients

it is essential that they be included in the diet

hypoglycemia

deficiency of blood glucose

Water-soluble Fiber

found in oats, beans, peas, carrots, brown rice, and fruits

Water-insoluble Fibers

apparently have no effect on cholesterol or LDLs

Glucose-sparing and Protein-sparing Effects

as long as enough fat is available to meet the energy needs of the tissues, protein is not catabolized for fuel and glucose is spared for consumption by cells that cannot use fat, such as neurons

Essential Fatty Acids

are those we cannot synthesize and there fore must obtain from the diet

Lipoproteins

tiny droplets with a core of cholesterol and triglycerides and a coating of proteins and phopholipids

lipoprotein Lipase

that hydrolyzes triglycerides into monoglycerides and free fatty acids

Essential Amino Acids

that we cannot synthesize: isoleucine, leucine, lysine, methionine, phenylalnine, threonine, tryptophan and valine

Inessential Amino Acids

not because the body doesn not require them buy because it can syntesize its own when the diet does not supply them

Complete Proteins

are those that rpobide all of the essential amino acids in the necessary proportions for human tissue growth, maintance and nitrogen balance

Incomplete Proteins

lack one or more essential amino acids

Net Protein Utilization

the percent of the amino acids in a protein that the human body uses

Nitrogen Balance

is a state in which the rate of nitrogen ingestion equals the rate of excretion

Positive Nitrogen Balance

indicates that body proteins are being broken down and used a sfuel

Water-soluble Vitamins

are absorbed with water from the small intestine, dissolve freely in the body fluids, and are quickly excreted by the kidneys

Fat-soluble Vitamins

are incorporated into lipid micelles in the small intestine and absorbed with dietary lipids

Hypervitaminosis

(vitamin excesses) also causes disease

Glycolysis

which splits a glucose molecule into two molecules of pyruvic acid

Anaerobic Fermentation

which occurs in the absence of oxygen and reduces pyruvic acid to lactic acid

Aerobic Respiration

which occurs in the presence of oxygen and oxidizes pyruvic acid to carbon dioxide and water

Body Weight

remains stable if energy intake and output are equal

Body Weight seems to have a Hoeostatic

set point

Combination of Environmental and Hereditary factors

30 - 50% of variation between individuals is due to heredity with the rest being eating and exercise habits

Phosphorylation

the enzyme hexokinase transfers an inorganic phophate group (Pi) from ATP to glucose, producing glucose 6-phophate (G6P)

Pyruvic Acid

3 carbon (C3) molecules

Priming

G6P is rearranged (isomerized) to form fructose 6-phophate, which is phophorylated again to form frutose1, 6-diphophate

Cleavage

the lysis part of glycolysis occurs when fructose 1, 6-diphophate splits into two 3-carbon molecules

Oxidation

each PGAL molecule is then oxidized by removing a pair of hydrogen atoms

Dephosphorylation

phosphate groups are taken from the glycolysis intermediates and transferred to ADP, phophorylating it to ATP

Matrix Reactions

because their controlling enzymes are in the fluid of the mitochondrial matrix

Membrane Reactions

their controlling enzymes are bound to the membrane of the mitochondrial cristae

Proton Pump

that removes H+ from the mitochodrial matrix and pumps it into the space between the inner and outer mitochodrial membranes

Chemiosmotic Mechanism

which suggests the "push" created by the electrochemical H+ gradient

Efficiency

a ratio of energy output to input

Glycogenesis

teh synthesis of glycogen, is stimulated by insulin

Glycogenolysis

the hydrolysis of glycogen, releases glucose between meals when new glucose is not being ingested

Lipogenesis

synthesizing fats from other types of molecules

Lypolysis

breaking down fat for fuel

Beta-oxidation

which removes two carbon atoms at a time

Ketogenesis

two acetyl groups are condensed to form acetoacetic acid and some of this is further converted to B-hydroxybutyric acid and acetone

Amino Acid Pool

that cells can draw upon to make new proteins

Deamination

the removal of an amino group

Amination

the addition of -NH2;

Transamination

the transfer of -NH2 from one molecule to another

Absorptive (fed) State

lasts about 4 hours during and after a meal.

Postabsorptive (fastin) State

prevails in the late mornign, late afternnon and overnight

Metabolic Rate

means the amount of energy liberated in the body per unit of time, expressed in such terms as kcal/hr or kcal/day

Calorimeter

a closed chamber with water filled walls that absorb the heat given off by the body

Basal Metabolic Rate BMR

is a baseline or standard of comparison that minimizes teh effects of such variables

Total Metabolic Rate (TMR)

is the sum of BMR and energh expenditure for voluntary activities, especially muscular contractions

Hypothermia

an excessively low body temperature, can cause metabolism to slow down to the point that it cannot sustain life

Hyperthermia

an excessively high temperature, can disrupt the coordination of metabolic pathways and also lead to death

Thermoregulation

the balance between heat production and loss, is a critically important aspect of homeostasis

Core Temperature

the temperature of organs in the cranial, thoracic, and abdominal cavities

Shell Temperature

is the temperature closer to the surface, especially skin and oral temperature

Radiation

heat means molecular motion

Conduction

as the molecules of our tissues vibrate with heat energy, they collide with other molecules and transfer kinetic energy to them

Convection

the motion of fluid due to uneven heating

Evaporation

the cohesion of water molecules hampers their vibratory movement in response to heat input

Forced Convection

accelerates heat removal

Heat-losing Center

a nucleus still farther anterior in the hypothalamus

Heat-promoting Center

a more posterior nucleus

Nonshivering Thermogenesis

is a more long-term mechanism for generating heat , used especially in the colder seasons of the year

Behavioral Thermoregulation

behaviors that raise or lower the body's heat gains and losses

Heat Cramps

are painful muscle spasms that result from excessive electrolyte loss in the sweat

Heat Exhaustion

results from more severe water and electrolyte loss and is characterized by hypotension, dizziness, vomiting and sometimes fainting

Heatstrake

sunstroke

Appetite and satiety are contolled by

hypothalamus

Other Factors in Appetite Control

inflating the stomach with balloon inhibits hunger, amino and fatty acids stimulate release of CCK from small intestine (appetite suppressant), neuropeptide Y from hypothalamus is an appetite stimulant (it may be inhibited by leptin from "full" fat cells), different neurotransmitters stimulate desire for different kinds of food -- carboyhydrates, fats or protein

One Calorie

is amount of heat that will raise the temperature of 1 g of water 1 degree C. (1,000 calories is a kilocalorie in biochemistry)

Fat contain about

9 kcal/g when oxidized

Carbohydrates and proteins contain about

4 kcal/g

When a substance is used for fuel

it is oxidized solely or primarily to make ATP

Nutrients

are any ingested chemical used for growth, repair or maintenace -- water, carbohydrates, lipids, proteins, minerals, vitamins

Macronutrients

must be consume in large amounts -- proteins, fats and carbohydrates

Micronutrients

are needed only in small amounts

Recommended Daily Allowances (RDA)

is safe estimate of daily intake that meets standard needs (minimums)

Essential Nutrients

are those the body can not synthesize- minerals, vitamins, 8 amino acids and 1-3 fatty acids must be consumed in the diet

Carbohydrates

in 3 places in the body - muscle and liver glycogena and blood glucose

Neurons and RBCs

depend on glucose almost exclusively

Fat is Oxidized

when glycogen and glucose levels are low (if incompletely oxidized produces ketone bodies and acidosis)

Sugars do serve as

Structural components

Blood Glucose

is carefully regulated through the actions of insulin and glucagon

Carbohydrates RDA

175 g/day

Dietary Carbohydrates come in 3 forms

monosaccharides, disaccharides, polysaccharides

Monosaccharides

glucose, galactose and fructose, arising from digestion of starch and disaccharides, normal blood sugar concentration ranges 70 to 110 mg/dL

Disaccharides

table sugar (sucrose)

Polysaccharides

starch, glycogen and cellulose

Nearly all dietary carbohydrates come from

plants

Dietary Fiber

all fibrous animal or plant material that resist digestion- cellulose, pectin, gums and lignins

Fiber is important to the diet

RDA is 30 g/day

insoluble Fiber

absorbs water in the intestines and thus softens the stool and gives it bulk speeding teh transit time

Pectin

is a water-soluble fiber found in oats, beans, carrots, fruits and brown rice and reduces blood cholesterol and LDL levels

Cellulose, himicellulose and lignin

are water-insoluble fibers having no effect upon cholesterol

Lipids

average adult male is 15% fat; female 25% fat, represents body's stored energy

Hydrophobic

contains almost no water, contains twic as much energy per gram and is thus more compact storage form

Fat-soluble Vitamins

A,D,E and K depend on dietary fat for their absorption by the intestine

Phopholipids and Cholesterol

are structural components of plasma membranes and myelin

Cholesterol

is precursor of steriods, bile salts and vitamin D

Fatty Acids

are precursors of prostaglandins and other eicosanoids

Lipids should be less than

30% of daily calorie intake- typical american gets 40-50% of calories from fat

Most Fatty Acids

can be synthesized by the body

Essential Fatty Acids

are those that must be consumed (linoleic, linolenic and arachidonic acids must be consumed)

Saturated Fats

are of animal origin-- meat, egg yolks and dairy products

Unsaturated Fats

are found in nuts, seeds and most vegetable oils

Cholesterol

is found in egg yolks, cream, shellfish, organ meats and other meats

Lipids

are transported in the blood as lipoporteins (keeps it suspended in plasma)

Lipoproteins

are categorized into 4 groups by their density: more protein means more dense

Lipoproteins Types

chylomicrons, high-density (HDLs), low-density (LDLs), very low-density (VLDLs)

Chylomicrons

are formed in the absorptive cells of teh small intestine, passes into the lymphatic system and into the blood, capillary surface enzymes hydrolyze the triglycerides, fatty acids and glycerol enter the fat cells to be resynthesized into triglycerides for storage, chylomicron remnant is degraded by liver

VLDLs

produced by the liver, transport lipids to the adipose tissue for storage

Desirable to maintain high levels of HDL

since it indicates cholesterol is being removed from the arteries

Desirable to maintain a low LDL concentration

signifies high rate of cholesterol deposition in arteries (smoking, saturated fats, coffee and stress increase LDLs)

Desirable to maintain total plasma cholesterol concentration of 200 mg/dL or less

most cholesterol is internally synthesized, but dietary restriction may lower blood cholesterol levels (vigorous exercise lowers blood cholesterol)

Proteins

c12-15% of body mass - mostly inskeletal muscles

Functions of Proteins

muscle contraction, ciliary and flagellar motility, structural role in all cell membranes (channels, pumps, etc...), fibrous proteins (collagen, elastin and keratin) globular proteins include antibodies, hormones, hemoglobin, enzymes, etc..., plasma proteins maintain blood osmolarity and viscosity

RDA

is 44-60 g/day depending on age and sex

Nutritional Value of a Protein

depends whether it supplies amino acids in the proportions needed- essential amino acids can not be synthesized

Cells do not store surplus

when a protein is to be synthesized, all the necessary amino acids must be present

Complete Proteins

supply all amino acids in right amounts

Nitrogen Balance

requires the rate of nitrogen (protein) ingestion equals the rate of excretion

Positive Nitrogen Balance

occurs in growing children since they ingest more than they excrete

Negative Nitrogen Balance

occurs if body proteins are being broken down for fuel (muscle atrophy)

Glucocorticoids

promote protein catabolism in states of stress

Calcium and phosphorus

make up the bones and teeth

Phosphorus

is part of many structural compounds

Calcium, Iron, Magnesium and Manganese

function as cofactors for enzymes

Iron

is essential for hemoglobin and myoglobin

Chlorine

is component of stomach acid (HCl)

Mineral Salts

function as electrolytes and govern teh function of nerve and muscle cells, regulating the distribution of water in the body

Vitamins

body synthesizes some vitamins from precursors (A,D, etc...)

Water-soluble Vitamins

are absorbed with water from the small intestine and are not stored (C and B)

C Promotes

hemoglobin and collagen synthesis

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