Chapter 25: Metabolism and Nutrition

Although leptin supresses appetite and produces satiety in experiment animals,

it is not deficient in most obese ppl

Because each molecule of glucose generates two molecules of pyruvic acid, __________ molecules of CO2 are liberated from each original glucose molecule catabolized along its pathway

6 CO2 molecules

How many molecules of O2 are used, and how many molecules of CO2 are produced during the complete oxidization of one glucose molecule?

6 molecules of O2 are used and 6 molecules of CO2 are produced.

Net Yield for Krebs Cycle

6NADH + 6H 2ATP 2FADH2 (release of 4CO2)

1 molecule of NADH+H yields 3 ATP; 1 molecule of FADH2 yields 2 ATP hence, because each glucose molecule provides two acetyl Co A molecules, glucose catabolism via the KRebs cycle and electron transport chain yields .....

6NADH+6H = 6x3= 18 ATP 2 FADH2 = 2x2= 4ATP 2ATP= 2ATP TOTAL: 24 ATP molecules per glucose molecule from krebs cycle

an increase in blood glucose level, as occurs after eating a meal....

> decreases appetite

When you have a fever...

>pyrogen causes thermostat to reset... say it rises to 39 degrees... > heat-promoting mechanisms (vasoconstriction, increase metabolism, shivering) are operating at full force. -even though core temp is climbing higher than normal (say 38 degrees), the skin remains cold, and shivering occurs- called a CHILL -Chill- definite sign core temp is rising -core temp reaches the setting of thermostat> chills disappear. Now body will regulate temp at 39 degrees. -when pyrogens dissapear, thermostat is reset to normal. -b/c core temp is high in the beginning, the heat-losing mechanisms (vasodilation and sweating) go into operation to decrease core temp. -skin becomes warm> person begins to sweat> Called the CRISIS PHASE -Crisis Phase- indicates core temp is falling. -death results if core temp rises above 44-46 degrees

Fate of Pyruvic Acid

Oxygen Plentiful- Aerobic Pathway- Pyruvic acid enters mitochondria> converted to acetyl coenzyme A> enters Krebs cycle Oxygen Scarce- Anaerobic Pathway- pyruvic acid converted to lactic acid.

Where is the concentration of H+ the highest?

concentration of H+ is highest in the space between the inner and outer mitochondrial membranes.

Heat cramps

cramps that result from profuse sweating -salt lost in sweat causes painful contractions of muscles -usually occur in muscles used while working but do not appear until person relaxes once work is done. -Drink salted liquids to improve

When energy use exceeds energy input...

triglycerides in adipose tissue are catabolized to provide extra energy;

Satiety

feeling of fullness.

Melanocortin

inhibits food intake

Carbohydrate metabolism

-Polysaccharides & Disaccharides--> hydrolyzed intomonosaccharide glucose (80%), fructose, and galactose. -Hepatocytes convert remaining fructose and all galactose to GLUCOSE -total of 2-3g of GLUCOSE normally circulates in blood

Energy Homeostasis and regulation of food intake

-Energy Homeostasis- the precise matching of energy intake (in food) to energy expenditure over time. -when energy content of food=energy used by cells in body=weight remains constant.

Postabsorptive state

- 4 hrs after a meal, abortion is nearly complete, blood glucose level starts to fall b/c glucose continues to leave bloodstream & enter body cells (while none is being absorbed in GI tract) -main metabolic challenge: to maintain a normal blood glucose level of 70-100mg/100mL (3.9-6.1mmol/liter)

-normal blood glucose level very important for nervous system and for red blood cells. WHY?

- dominant fuel molecule for ATP production in nervous system is GLUCOSE (fatty acids are unable to pass the blood brain barrier) -RBCs have no mitochondria--> can only derive ATP from glycolysis

Cholesterol

-2 sources: > some present in foods (eggs, dairy products, organ meats, beef, pork, processed luncheon meats) >most synthesized by hepatocytes -a high intake of dietary fats stimulates reabsorption of cholesterol-containing bile back to the blood, so less cholesterol is lost in the feces. -when sat fats are broken down in the body, hepatocytes use some of the breakdown products to make cholesterol. -LDL cholesterol< 130mg/dL -HDL cholesterol > 40mg/dL -as total cholesterol increases, risk of coronary artery disease increases. -can be reduced by exercise, diet and drugs.

Cellular respiration begins with glycolysis

-6-carbon molecule is split by chemical reactions into two 3-carbon molecules of PYRUVIC ACID -Consumes 2 ATP, but produces 4 ATP: NET GAIN OF 2 ATP for each glucose molecule oxidized. -During glycolysis, each molecule of glucose is converted to two molecules of pyruvic acid -NET: 2 ATP 2 NADH +2H 2 Pyruvic Acid

Reduction

-Addition of Electrons -Addition of hydrogen atoms -Increase in potential energy -ex. conversion of pyruvic acid into lactic acid (addition of 2 H+= reduction)

Krebs Cycle (citric acid cycle)

-After pyruvic acid undergoes decarboxylation> remaining acetyl group has attached to CoA -Acetyl CoA is ready to enter krebs cycle -Krebs= also known as CITRIC ACID CYCLE -occurs in matrix of mitochondia -series of oxidation-reduction reactions & decarboxylation reactions (release CO2) -Transfer chemical energy (in the form of electrons) to two coenzymes- NAD+ and FAD. -Pyruvic acid derivatives> oxidized (lose H+)====> coenzymes are reduced (gain H+) -Net for 1 pyruvic acid 3NADH+3H 1ATP 1FADH2 (release of 2 CO2) (TIMES 2) NET: 6NADH+6H 2ATP 2FADH2 (Release of 4 CO2)

Electron Transport Chain

-series of electron carriers (integral membrane proteins in the inner mitochondrial membrane) -Each carrier in the chain is reduced as it PICKS UP electrons and oxidized as it GIVES UP electrons. -Electrons pass through chain> series of exergonic reactions release small amounts of energy (used to form ATP) -Aerobic Cellular Respiration: final electron acceptor of chain is oxygen. -Because this mechanism of ATP generation links chemical reactions (passage of electrons along the transport chain) with pumping of hydrogen ions, it's called Chemiosmosis Get (input into E.T.P) 4 ATP= 4ATP 10NADH+10H= 30ATP 2FADH2= 4 ATP (38ATP total in cellular respiration)

Lipolysis

-splitting triglycerides into glycerol and fatty acids -catalyzed by enzymes called LIPASES. -epinephrine and norepinephrine (enhance lipolysis)> released when sympathetic tone increases (like during exercise) -cortisol, thyroid hormones, insulinlike growth factors= lipolytic hormones -Insulin INHIBITS lipolysis

Lipogenesis

-synthesizing lipids from glucose or amino acids -stimulated by INSULIN (lipogenesis= stimulated by insulin; lypolysis= stimulated by Epinephrine, Norepinephrine and Cortisol) -occurs when mole calories are consumed than are needed to satisfy ATP needs. -Excess carbs, proteins and fats--> converted to triglycerides. -Amino acids--> acetyl CoA--> fatty acids--> triglycerides. -Glucose--> glyceraldehyde 3-phosphate--> glycerol -Glucose--> glyceraldehyde 3-phosphate-> acetyl CoA--> fatty acids. -glycerol & fatty acids undergo anabolic reactions to become stored triglycerides (or to become other lipids such as lipoproteins, phospholipids and cholesterol)

Core Temperature

-temperature in body structures deep to the skin and subcutaneous layer -core temp thats too high kills by denaturing body proteins -core temp thats too low causes cardiac arrhythmias that result in death

Glycogenolysis

-the breakdown of glycogen to glucose -happens when body activities require ATP> glycogen stored in hepatocytes is broken down into glucose and released into blood to be transported to cells where it will be catabolized by process of cellular respiration -phosphorylase- an enzyme that catalyzes this reaction, is activated by GLUCAGON from pancreatic alpha cells and EPINEPHRINE from adrenal medulla. -phosphorylated glucose molecules can't ride aboard GluT transporters>> Phosphatase (an enzyme that converts glucose 6 phosphate into glucose) is absent in skeletal muscle cells. -hepatocytes have phosphatase- can release glucose derived from glycogen into bloodstream (skeletal muscles cannot).

Obesity may result from

-trauma, tumors in food-regulating centers in hypothalamus -genetic factors can contribute -eating habits -overeating to relieve tension -social customs

Net Yield for Formation of Acetyl CoA

2NADH+2H (release of 2CO2)

Net Yield for Glycolysis

2 ATP 2NADH+2H

When energy input exceeds energy expenditure...

triglycerides are stored.

Energy intake depends ONLY on the amount of food consumed (and absorbed),but three components contribute to total energy expenditure.

-Basal Metabolic Rate (BMR)= 60% of expenditure -Physical Activity= adds 30-35% (can be lower for sedentary ppl). Partly from voluntary exercise (walking), and partly from nonexercising activity thermogenesis (NEAT)-energy costs for maintaining muscle tone, posture, and involuntary fidgeting movements -Food-Induced Thermogenesis- - 5-10% of total energy=heat produced while foods being digested, absorbed, and stored

Several factors that affect the metabolic rate and thus the rate of heat production:

-Exercise- metabolic rate increases -Hormones- Thyroid hormones are main regulators of BMR. BMR increases as blood levels of Thyroid Hormones rise. Thyroid hormones increase BMR by stimulating aerobic cellular respiration. As cells use more oxygen to produce ATP, more heat is given off and body temp rises. Other hormones that have minor effects on BMR: Testosterone, Insulin, Human Growth Hormone (can increase metabolic rate by 5-15%) -Nervous System- during exercise or stressful situations, symp. division is stimulated> release of NE and E> increase metabolic rate -Body Temp- Higher body temp=higher metabolic rate. Each 1 degree rise in core temp= increases rate of biochemical reactions by 10%. (metabolic rate increased substantially during a fever) -Ingestion of food- raises metabolic rate 10-20% due to energy "costs" of digesting, absorbing, and storing nutrients. Food-induced Thermogenesis is greater after eating a high protein meal and is less after eating carbs and lipids. -Age- metabolic rates of a child double that of an elderly person. -Other factors- gender (lower metabolic rate in F except during pregnancy and lactation), climate (lower in tropical regions), sleeping (lower), and malnutrition (lower)

Glycerol and fatty acids that result from lipolysis are catabolized via different pathways.

-Glycerol-- converted to glyceraldehyde 3-phosphate > If ATP supply in a cell is high= glyceraldehyde 3-phosphate is converted to glucose; > If ATP supply in a cell is low= glyceraldehyde 3-phosphate enters the catabolic pathway to pyruvic acid. -Fatty acids- catabolized differently & yield more ATP. > first stage: beta oxidation (enzymes remove 2 carbon atoms from long chain of carbon atoms and are attached to coenzyme A forming Acetyl CoA. >Acetyl CoA then enters Krebs cycle. -hepatocytes can take 2 acetyl CoA molecules at a time and condense them to form acetoacetic acid. Some is then converted into beta hydroxybutyric acid and acetone. These are collectively known as Ketone Bodies (ketogenesis)

What cells can carry out gluconeogenesis and glycogenesis?

-Hepatocytes can cary out gluconeogenesis and glycogenesis.

Thermoregulation

-If core temp declines> thermoreceptors in skin and hypothalamus send nerve impulses to preoptic area and heat-promoting center in hypothalamus> hypothalamic neurosecretory cells produce Thyrotropin-releasing hormone (TRH)> hypothalamus discharges nerve impulses and secrete TRH> stimulates thyrotrophs in anterior pituitary to release Thyroid-Stimulating Hormones (TSH)> nerve impulses from hypothalamus and TSH then activate several effectors: -Vasoconstriction- decrease heat loss through skin -Adrenal Medulla releases hormones that increase cellular metabolism -Skeletal muscles contract in repetitive cycle called SHIVERING -Thyroid gland releases thyroid hormones which increase metabolic rate

Chemiosmosis

-In chemiosmosis, ATP is produced when hydrogen ions diffuse back into the mtochondrial matrix. Works as follows: 1. Energy from NADH +H+ passes along ETC and is used to pump H+ from matrix of mitochondrion into space between inner and outer mitochondrial membranes. Called a proton pump b/c H+ ions consist of a single proton. 2. High concentration of H+ accumulates between inner and outer mitochondrial membranes 3. ATP synthesis occurs as hydrogen ions flow back into the mitochondrial matrix through a special type of H+ channel in the inner membrane (notice oxygen is used to help form water in step 3. this is th eonly point in aerobic cellular respiration where O2 is consumed.

Minerals

-Inorganic -4% of body mass; concentrated mostly in skeleton. -Excess excreted in urine & feces -calcium, phosphorus, potassium, sulfur, sodium, chloride, magnesium, iron, iodide, manganese, copper, cobalt, zinc, fluoride, selenium, and chromium -Mos abundant is Calcium

Coenzymes that are commonly used by animal cells to carry hydrogen atoms?

-Nicotinamide Adenine Dinucleotide (NAD) [derivative of B vitamin niacin] -flavin adenine dinucleotide (FAD)[derivative of vitamin B2-riboflavin]

Oxidation

-Removal of Electrons -Loss of hydrogen atoms (dehydrogenation reactions) -Decrease in potential energy -ex. conversion of lactic acid into pyruvic acid. (Removal of 2H+= oxidation) -hydrogen atoms that are lost during oxidization do not remain free in the cell, but instead are transferred immediately by COENZYMES to another compound

Glucose Anabolism

-Synthesis of glycogen -synthesis of new glucose molecules from some of the products of protein and lipid breakdown

Coupling of catabolism and anabolism by ATP

-When complex molecules and polymers are split apart (catabolism, at left), some energy is transferred to form ATP and the rest is given off as HEAT. -when simple molecules and monomers are COMBINED to form complex molecules (anabolism, at right), ATP provides the energy for synthesis and again some energy is given off as HEAT. (40% of energy released in catabolism is used for cellular functions; rest converted to HEAT (to maintain normal body temp)

Fate of proteins

-active transport of amino acids stimulated by insulinlike growth factors (IGFs) and insulin -after digestion> amino acids are reassembled into proteins -proteins function as: enzymes, transportation (hemoglobin), antibodies, clotting chemicals (fibrinogen), hormones (insulin), contractile elements in muscle fibers (actin and myosin) -several proteins serve as structural components of body-- collagen, elastin, keratin

Phosphorylation

-adding a phosphate -increases its potential energy

surplus calories--> converted to triglycerides--> stored in adipose cells

-adipose increase in size -at a maximal size--> they divide. -proliferation of adipocytes occurs in extreme obesity -enzyme endothelial lipoprotein lipase regulates triglyceride storage -accumulation of fat in abdomen is associated with higher blood cholesterol level & other cardiac risk factors (adipose cells in this area appear to be more metabolically active)

Triglyceride Storage

-adipose tissue- removes triglycerides from chylomicrons and VLDLs and store them until needed for ATP production in other parts of body. -triglycerides constitute 98% of all body energy reserves. -stored more readily than glycogen -insulates, protects -triglycerides in adipose tissue are continually broken down and resynthesized.

Two hypothalamic areas involved in regulation of food intake

-arcuate nucleus -paraventricular nucleus. -mouse gene named obese that causes overeating and severe obesity in its mutated form. -product in this gene is the hormone LEPTIN

Treatment for obesity

-behaviour modification -very low-carorie (VLC) diets, -drugs -surgery(gastric bypass or gastroplasty-greatly reduce stomach) -regular exercise (30 min/day 5-7 days/week) -heart healthy diet (abundance of veggies, low in fat (esp sat fat) -2 drugs to treat obesity: Sibyutramine-an appetite suppressant that works by inhibiting reuptake of seratonin and norepinerphrine > Orlistat- inhibits the lipases released into the lumen over the GI tract. W/ less lipase activity, fewer triglycerides are absorbed.

Obesity

-body weight more than 20% above a desirable standard due to excessive accumulation of adipose tissue. -can be overweight without being obese (athletes may have higher-than normal amounts of muscle tissue)

The pumping of H+ produces both a conc. gradient of protons and an electrical gradient.

-buildup of H+ makes one side of inner mitochondrial membrane positively charged compared to the other side -resulting electrochemical gradient has potential energy called "proton motive force" -proton channels in inner mitochondrial membrane allow H+ to flow back acros membrane, driven by proton motive force. -As H+ flows back, they generate ATP because H+ channels also include an enzyme called ATP synthase. -Enzyme uses proton motive force to synthesize ATP from ADP and P. -Process of chemiosmosis is responsible for MOST of the ATP produced during cellular respiration.

Nonessential amino acids

-can be synthesized by body cells -formed by transamination

Catabolism

-chemical reactions that BREAK DOWN complex organic molecules into simpler ones. -exergonic -produce more energy than they consume -occurs in glycolysis, the Krebs cycle, and the electron transport chain

Anabolism

-chemical reactions that COMBINE simple molecules and monomers to form the body's complex structural and functional components. -endergonic -consume more energy than they produce -ex. formation of peptide bonds between amino acids during protein synthesis -ex. building of fatty acids into phospholipids that form plasma membrane

Complete Protein

-contains SUFFICIENT amounts of all essential amino acids -Beef, fish,poultry, eggs, milk (contain complete proteins)

Hypothalamic Thermostat

-control center that functions as body's thermostat= hypothalamus=preoptic area -preoptic area- receives impulses from thermoreceptors in the skin and mucous membranes and in the hypothalamus. -Generate nerve impulses at higher frequency when blood temp increases & at lower frequency when blood temp decreases -Nerve impulses from the preoptic area propogate to two other parts of the hypothalamus: heat-losing center (lower body temp) & heat-promoting center (raises body temp)

Heat exhaustion

-core temp is generally normal, or a little below -skin is cool and moist due to profuse perspiration -loss of fluid and electrolytes (esp salt) -salt loss results in muscle cramps -dizziness -vomiting -fainting -fluid loss=low blood pressure -rest, rehydration, electrolyte replacement

oxidation and reduction reactions are always _______

-coupled -each time one substance is oxidized, another is simultaneously reduced. hence, "Oxidation-Reduction" or "Redox" Reactions. -ex. when lactic acid is oxidized to form pyruvic acid, the 2 hydrogen atoms removed in the reaction are used to reduce NAD+ (to NADH+H)

Leptin

-decreases ADIPOSITY- total body-fat mass -synthesized and secreted by adipocytes in proportion to adiposity. -as more triglycerides are stored, more leptin is secreted into bloodstream. -leptin acts on hypothalamus to inhibit circuits that stimulate eating while also activating circuits that increase energy expenditure. -Hormone insulin has a similar (but smaller) effect

Incomplete Proteins

-does NOT contain all essential amino acids -leafy green veggies, legumes (beans and peas) andgrains

Fever

-elevation of core temp caused by resetting of hypothalamic thermostat. -common causes: viral or bacterial infection, bacterial toxins, ovulation, excessive secretion of thyroid hormones, tumors, reactions to vaccines. -phagocytes ingest certain bacteria> stimulated to secrete a pyrogen (fever stimulating substance) - one pyrogen is interleukin-I. It circulates to hypothalamus and induces neurons of preoptic area to secrete prostaglandins. -prostaglandins can reset hypothalamic thermostat at a higher temp. -temp-regulating reflex mechanisms act to bring the core body temp up to this new setting. -Antipyretics- agents that relieve or reduce fever (ASPRIN, ACETAMINOPHEN (TYLENOL), IBUPROFEN(ADVIL)- reduce fever by inhibiting synthesis of certain prostaglandins

Pyruvate Dehydrogenase

-fate of pyruvic acid produced during glycolysis depends on availability of oxygen -if oxygen is scarce (anaerobic conditions like for skeletal muscle fibers during strenuous exercise)- pyruvic acid is reduced via anaerobic pathway> addition of 2 H+ to form LACTIC ACID (lactate) 2Pyruvic Acid (oxidized) + 2NADH +2H+----> 2Lactic Acid (reduced) +2NAD+ -lactic acid then diffuses out of the cell and enters the blood -Hepatocytes remove lactic acid from the blood and convert it back to pyruvic acid (buildup of lactic acid=muscle fatigue)

Glucose movement into cells

-first must pass through plasma membrane and enter the cystol. -Glucose absorption in GI tract and kidney tubules is accomplished by SECONDARY ACTIVE TRANSPORT (Na+-glucose symporters) -Glucose enters via GluT molecules (transporters that bring glucose in via FACILITATED DIFFUSION) -high levels of insulin increases insertion of GluT4 into plasma membrane (increase rate of facilitated diffusion of glucose into cells) -in neurons and hepatocytes> GluT ALWAYS present- glucose entry always "turned on" -When glucose enters cell> it becomes PHOSPHORYLATED. -GluT can't transport phosphorylated glucose> TRAPS GLUCOSE WITHIN CELL.

Protein Anabolism

-formation of peptide bonds btwn amino acids to form new proteins. -carried out by ribosomes (directed by cells DNA & RNA) Insulinlike growth factors, Thyroid hormones (T3 and T4), Insulin, Estrogen, Testosterone = STIMULATE PROTEIN SYNTHESIS -When dietary intake of protein is adequate, eating more protein will not increase bone or muscle mass (only a regular program of forceful, weight-bearing muscular activity will)

After a meal...

-glucose-dependent insulinotropic peptide (GIP) & the rising blood levels of glucose and certain amino acids--> stimulates pancreatic beta cells to release INSULIN -insulin increases the activity of enzymes needed for anabolism & synthesis of storage molecules -Insulin also decreases the activity of enzymes needed for catabolic or breakdown reactions -insulin promotes entry of glucose and amino acids into cells -insulin stimulates the phosphorylation of glucose in hepatocytes and conversion of glucose-6-phosphate to glycogen. -in liver and adipose tissue- insulin enhances synthesis of triglycerides. -insulin also stimulates protein synthesis.

Moderate Obesity

-hazardous to health -risk factor in cardiovascular disease, hypertension, pulmonary disease, non-insulin-dependent diabetes mellitus, arthritis, certain cancers (breast, uterus, and colon), varicose veins, gallbladder disease

Up to a point, a fever is beneficial... why?

-higher temp intensifies the effects of interferons and the phagocytic activities of macrophages while hindering replication of some pathogens -fever increases heart rate- infection fighting WBCs are delivered to site of infection more rapidly -antibody production and T cell proliferation increases -heat speeds up rate of chemical reactions- help body cells to repair themselves more quickly

Heat and Energy Balance

-homeostasis of body temp can be maintained only if rate of heat loss from body=rate of heat production by metabolism. -Heat- form of energy. Measured as Temp. Expressed in units called calories. -Calorie (cal)- the amount of heat required to raise the temp of 1g of water 1 degree celcius. -1kilocalorie (Calorie)=1000 calories.- used to measure body's metabolic rate.

Body Temp Homeostasis

-if rate of body heat production=rate of heat loss> body maintains a constant core temp near 37 degrees celcius.

Absorptive state

-ingested nutrients are entering bloodstream -ingested food reaches bloodstream mainly as GLUCOSE, AMINO ACIDS, and TRIGLYCERIDES (in chylomicrons). -glucose is readily avail. for ATP production. -typical meal takes about 4 hr for complete absorption -oxidation of glucose for ATP production -storage of excess fuel molecules for future between-meal use (occurs in hepatocytes, adipocytes, & skeletal muscle fibers)

When oxygen is plentiful (aerobic conditions), most cells convert pyruvic acid to acetyl coenzyme A in the mitochondria matrix.

-links glycolysis (occurs in cystol) with the krebs cycle (occurs in matrix of mitochondria) -Because RBCs lack a mitochondria, they can only produce ATP through glycolysis (in cystol)

Fate of lipids

-lipids (like carbs), may be oxidized to produce ATP. -stored in adipose tissue and in liver when not needed. -some are structural molecules, or synthesize other essential substances. (ie. phospholipids; lipoproteins; thromboplastin (needed for blood clotting); myeling sheaths (speed up nerve impulse conduction) -2 ESSENTIAL FATTY ACIDS that body can't synthesize: Linoleic acid & Linolenic acid. (veg. oils & leafy vegetables).

Minerals and Vitamins

-many are components of the enzyme systems that catalyze metabolic reactions

Basal Metabolic Rate (BMR)

-measurement of metabolic rate while body is quiet, resting, and fasting. -measured by measuring the amount of oxygen used per kilocalorie of food metabolized. -1200-1800 Cal/day in adults 24 Cal/kg of body mass in adult males 22 Cal/kg in adult females.

ATP (adenosine triphosphate)

-molecule that participates most often in energy exchanges in living cells -"energy currency" of a living cell -couples energy-releasing catabolic reactions to energy-requiring anabolic reactions. -a molecule of ATP consists of an adenine molecule, a ribose molecule, and 3 phosphate groups.

When leptin and insulin levels are low...

-neurons from arcuate nucleus to the paraventricular nucleus release neurotransmitter called Neuropeptide Y that stimulates food intake. -Other neurons release a neurotransmitter called melanocortin- similar to melanocyte-stimulating hormone (MSH_ -Leptinstimulates release of melanocortin- acts to inhibit food intake. -Leptin, Neuropeptide Y and Melanocorin are key signaling molecules for maintaining energy homeostasis.

Glycolysis

-one glucose molecule is OXYDIZED -2 molecules of Pyruvic Acid are produced -produces 2 ATP and 2 NADH+2H -glycolysis does not require oxygen (a way to produce ATP anaerobically)= ANAEROBIC CELLULAR RESPIRATION.

What happens when body temp rises above normal?

-opposite of previous negative feedback loop described. -higher temp stimulates thermoreceptors> send nerve impulses to preoptic area> stimulates heat-losing center> inhibit heat-promoting center>impulses from heat-losing center dilate blood vessels in skin> skin becomes warm and excess heat is lost to environment via radiation and conduction as an increased volume of blood flows from warmer core of body into the cooler skin> Same time, metabolic rate decreases> shivering does NOT occur. -high temp stimulates sweat glands of skin (via hypothalamic activation of symp. nerves. -water in perspiration evaporates from surface of skin, skin is cooled> body temp returns to normal.

Vitamins

-organic nutrients required in small amounts to maintain growth and normal metabolism. -Do not provide energy or serve as bodys building materials -usually COENZYMES -most cant be synthesized by body- must be ingested in food. Vit K- produced by bacteria in GI tract and then absorbed. -Body can assemble some vitamins if the raw materials (provitamins) are provided. (ie. vit A is produced by body from provitamin beta-carotene)

Metabolic Rate

-overall rate at which metabolic reactions use energy. -some of the energy is used to produce ATP -some of the energy is released as HEAT -measured under standard conditions. while body is quiet, resting, and fasting= BASAL STATE.

Glucose catabolism

-oxidation of glucose to produce ATP= CELLULAR RESPIRATION -involves 4 sets of reactions: 1. Glycolysis 2. Formation of Acetyl Coenzyme A 3. the Krebs cycle 4. the Electron Transport Chain

Overview of cellular respiration (oxidation of glucose)

-oxidization of glucose involves glycolysis, formation of acetyl coenzyme A, the Krebs cycle, and the electron transport chain -Which of the 4 prouces are also called anaerobic cellular respiration? Glycolysis

Electron Transport Chain Reactions

-oxidize NADH+H+ and FADH2 and transfer their electrons through a series of electron carriers. -like Krebs cycle, also requires oxygen to produce ATP -Krebs and ETC are collectively known as areobic cellular respiration)

Krebs Cycle Reactions

-oxydize acetyl coenzyme A -produce 4CO2, 2ATP, 6NADH+6H+ and 2FADH2 -requires oxygen to produce ATP (aerobic cellular respiration

Formation of Acetyl Coenzyme A

-prepares pyruvic acid for entrance into Krebs Cycle -produces 2 NADH + 2H+ and 2 CO2.

Formation of Acetyl Coenzyme A

-prepares pyruvic acid for entrance into the Krebs cycle -converts pyruvic acid to a 2-carbon fragment called an acetyl group by removing a molecule of CO2 (decarboxylation)[ 1st reaction in cellular respiration that releases CO2] -pyruvic acid is also oxydized (loses 2 H+) -coenzyme NAD+ is reduced (picks up H- from pyruvic acid)> NADH+H -NET: loss of 2CO2 2NADH+2H

Gluconeogenesis

-process by which GLUCOSE is formed from NONCARBOHYDRATE sources (triglycerides, lactic acid, certain amino acids) -NEWLY formed -stimulated by cortisol and glucagon -cortisol stimulates breakdown of proteins into amino acids (expanding pool of amino acids available for gluconeogenesis). -60% of amino acids can be used for gluconeogenesis

Heat production

-production of body heat is proportional to metabolic rate.

Protein catabolism

-protein catabolism occurs in body (stimulated by cortisol) -proteins from worn-out cells> broken into amino acids -some amino acids are converted into other amino acids, peptide bonds are formed, new proteins are synthesized (recycling process) -hepatocytes- convert amino acids to fatty acids, ketone bodies, or glucose. -oxidize a small amount of amino acids to generate ATP via Krebs cycle and ETC. (have to be converted to acetyl CoA before they can be oxidized though). Before entering KRebs cycle, amino group (NH2) must be removed>> DEAMINATION -Deamination occurs in hepatocytes and produces ammonia (NH3) -liver converts toxic ammonia to urea> excreted in urine.

Protein Metabolism

-proteins broken down into amino acids -proteins are NOT warehoused for future use (like carbs and triglycerides) -Amino acids are either oxidized to produce ATP, or used to synthesize new proteins for body growth and repair -excess amino acids- not excreted in the urine or feces--> instead are converted to glucose (gluconeogenesis) or triglycerides (lipogenesis)

Regulation of Metabolism during Postabsorptive state

-regulated by hormones and symp. division of ANS -anti-insulin hormones- counter effects of insulin during absorptive state. -as blood glucose level declines, secretion of insulin falls & release of anti-insulin hormone rises. -when blood glucose level declines- glucagon is released at a faster rate & insulin is secreted more slowly. -low blood glucose- activates sympathetic branch of ANS- release norepinephrine and epinephrine into bloodstream. -epinephrine- like glucagon- stimulates glycogen breakdown. -epinephrine and norepinephrine- potent stimulators of lipolysis. (helps to increase glucose and fatty acid levels in the blood)>> muscles use more fatty acids for ATP production & more glucose is avail. to nervous system.

Glycogenesis

-when glucose is not needed immediately for ATP production -glucose combines with other molecules of glucose to form GLYCOGEN (stored form of carbs in body) -hormone INSULIN from beta cells stimulates hepatocytes and skeletal muscle cells to carry out glycogenesis (synthesis of glycogen) -can store 75% in SKELETAL MUSCLE FIBERS, and the rest in HEPATOCYTES

Fate of Glucose -Glucose is the body's preferred source for synthesizing ATP. It's used for.....

1. ATP production- glucose is oxidized to produce ATP for cells that require immediate neergy. 2. Amino acid synthesis- cells can use glucose to form several amino acids--> proteins 3. Glycogen synthesis- Hepatocytes and muscle fibers perform glycogenesis (glucose -> glycogen). Storage capacity of glycogen is 125g in LIVER and 375g in SKELETAL MUSCLES 4. Triglyceride synthesis- when glycogen storage is FULL> hepatocytes transform glucose to glycerol and fatty acids> used for LIPOGENESIS (synthesis of triglycerides)> diposited in adipose tissue (unlimited storage capacity)

Postabsorptive state reactions

1. Breakdown of liver glycogen 2. Lipolysis (breaking down of triglycerides to form glucose) 3. Gluconeogenesis using lactic acid- during exercise, skeletal muscle tissue break down stored glycogen (step 9) and produces some ATP anaerobically via glycolysis. Some of the pyruvic acid that results is converted to acetyl CoA, and some is converted to lactic acid (diffuses into blood). In liver, lactic acid can be used for gluconeogensis and resulting glucose is released into blood 4. Gluconeogenesis using amino acids- breakdown of proteins in skeletal muscles & other tissues- releases amino acids--> converted to glucose by gluconeogenesis in liver 5. Oxidation of Fatty acids- oxidize fatty acids directly, feed them into krebs cycle as acetyl CoA & produce ATP through the ETC. 6. Oxidation of Lactic Acid- cardiac muscles produce ATP aerobically from lactic acid. 7. Oxidation of Amino Acids- in hepatocytes- amino acids may be oxidized directly to produce ATP 8. Oxidation of Ketone Bodies- hepatocytes convert fatty acids to ketone bodies (used by heart, kidneys and other tissues for ATP production). 9. Breakdown of muscle glycogen- skeletal muscles break down glycogen to glucose-6 phosphate which undergoes glycolysis and provides ATP for muscle contraction.

Organisms use 3 mechanisms of phosphorylation to generate ATP:

1. Substrate-level phosphorylation- generates ATP by transferring a high-energy phosphate group from a substrate, directly to ADP. Occurs in cystol in human cells. 2. Oxidative phosphorylation- removes electrons from organic compounds and passes them through the electron transport chain to molecules of oxygen. Occurs in the inner mitochondrial membrane of cells. 3. Photophosphorylation- occurs only in chlorophyll-containing plant cells, or in certain bacteria that contain other light-absorbing pigment.

________ Essential Amino Acids

10 Essential Amino Acids (20 amino acids in the body) -can not be synthesized in the body in adequate amounts> must be present in the DIET

Obese ppl who lose weight require ______ fewer calories to maintain normal body weight than do ppl who have never been obese

15% fewer calories

Overall, for every acetyl CoA that enters the krebs cycle...

3NADH +3H 1FADH2 1ATP produced.

Metabolic Adaptations

Absorptive state Postabsorptive state

Principal Metabolic Pathways during the absorptive state

Are the reactions shown in the figure mainly anabolic or catabolic? reactions of the absorptive state are mainly ANABOLIC

When in cellular respiration is carbon dioxide given off? what happens to this gas?

CO2 is given off during production of acetyl Coenzyme A & during krebs cycle. -diffuses into blood> transported to the lungs> exhaled.

3 organic nutrients

Carbs, Lipids, Proteins -provide energy needed for metabolic reactions -serve as building blocks to make body structures

Nutrients

Chemical substances in food and body cells used for growth, maintenance, and repair

Glycolysis occurs in ____________ Formation of Acetyl CoA and Krebs cycle occur in __________

Cystol Mitochondria

Negative feedback mechanisms that conserve heat and increase heat production

Each effector responds in a way that helps increase core temp to normal value: -Vasoconstriction- decreases flow of warm blood & the transfer of heat from organs to skin. Allows internal body temp to increase as metabolic reactions continue to produce heat. -Sypathetic nerves stimulate release of E & NE into blood. hormones increase cellular metabolism=increase heat production. -heat-promoting center cause increase muscle tone (thus heat production). >>shivering -Thyroid gland responds to TSH by releasing more thyroid hormones into the blood. increase thyroid hormones slowly increases metabolic rate= body temp rises.

Anarobic Cellular Respiration =______________________ Aerobic Cellular Respiration=__________&___________

Glycolysis Krebs Cycle & ETC

TOTAL ATP generated in total cellular respiration

Glycolysis : 2ATP 2NADH+2H (2x3)=6ATP 2Pyruvic Acid TOTAL: 8ATP Formation of Acetyl CoA: 2NADH +2H (2x3)=6ATP TOTAL: 6 ATP Krebs Cycle: 6NADH+6H (6x3)=18ATP 2FADH2 (2x2)= 4ATP 2 ATP= 2ATP TOTAL: 24 ATP Get (input into E.T.C.) 4 ATP= 4ATP 10NADH+10H= 30ATP 2FADH= 4ATP TOTAL ATP generated in total cellular respiration: 8ATP + 6ATP + 24 ATP= 38 ATP!!!!

Other hormones that increase appetite and decrease energy expenditure

Growth Hormone-Releasing Hormone (GHRH) Androgens Glucocorticoids Epinephrine (acting via alpha receptors) Progesterone

Absorptive state reactions

Following reactions dominate during the absorptive state: 1. About 50% of the glucose absorbed from a meal is oxidized by cells throughout the body to produce ATP via glycolysis, the Krebs cycle, and ETC. 2. Most glucose that enters hepatocytes is converted to glycogen. small amounts used for synthesis of fatty acids & glyceraldehyde 3-phosphate. 3. Some fatty acids and triglycerides synthesized in liver remain there but hepatocytes package most into VLDLs which carry lipids to adipose tissue for storage. 4. Adipocytes also take up glucose not picked up by the liver and convert it into triglycerides for storage. 40% of glucose absorbed is converted to triglycerides. 10% is stored as glycogen in skeletal muscles & hepatocytes. 5. Most dietary lipids are stored in adipose tissue. small portion used for synthesis reactions. Adipoctytes obtain the lipids from chylomicrons, from VLDLs, and from their own synthesis reactions. 6. absorbed amino acids that enter hepatocytes are deaminated to keto acids> enter krebs cycle for ATP production OR used to synthesize glucose or fatty acids 7. some Amino acids that enter hepatocytes are used to synthesize proteins (eg plasma proteins) 8. Amino acids not taken up by hepatocytes are used in other body cells ( like muscle cells) for synthesis of proteins or regulatory chemicals such as hormones or enzymes.

Other hormones that act to signal satiety and to increase energy expenditure

Glucagon Cholecystokinin Estrogens Epinephrine (acting via beta receptors) -distension of GI tract also contributes to termination of food intake.

Gluconeogenesis is stimulated by ________ & ___________

Glucagon and Cortisol

Glycogenolysis is stimulated by ______ & ___________

Glucagon and Epinephrine

___________ are the major regulators of metabolism in each state

Hormones are the major regulators of metabolism in each state. (absorptive and postabsorptive state) -Effects of INSULIN dominate absorptive state

Glycogenesis is stimulated by __________

Insulin

during fasting and starvation, many body cells turn to ___________________ for ATP production

Ketone bodies

Risk Ratio of cholesterol

LDL/HDL= risk ratio -Ratio > 4= BAD

Which type of lipoprotein delivers cholesterol to body cells?

LDLs deliver cholesterol to body cells

Both __________ and __________ are able to pass through the blood brain barrier

Leptin and Insulin.

Compounds with many H+ atoms such as glucose contain ____________ than oxidized compounds.

MORE chemical potential energy. -for this reason, glucose is a valuable nutrient.

Oxidation and reduction states of NAD+ and FAD...

NAD+(oxidized)-------> +2H---------->NADH+H (reduced) NAD+(oxidized)<------- -2H <-------- NADH +H (reduced) FAD (oxidized) ---------> +2H--------> FADH2 (reduced) FAD (oxidized) <-------- -2H <------- FADH2 (reduced)

The 10 reactions of glycolysis

NET: 2ATP 2NADH+2H+ 2Pyruvic Acid

Minerals vital to the body

Potassium & Magnesium= intracellular Sodium & Chloride= extracellular -calcium and phosphorus form part of matrix of bone -minerals are poor building materials (do not form long-chain compounds) -minerals mainly help regulate enzymatic reactions -Calcium, iron, magnesium and manganese= constituents of some coenzymes -Magnesium- serves as catalyst for conversion of ADP to ATP. -Sodium and phosphorus work in buffer systems- control pH of body fluids -Sodium- helps regulate osmosis of water and are involved in generation of nerve impulses.

Besides hepatocytes, which body cells can synthesize glycogen? why can't they release glucose into the blood?

Skeletal muscle fibers can synthesize glycogen, but cannot release glucose into the blood bc they lack the enzyme PHOSPHATASE required to remove the phosphate group from glucose (glucose trapped).

High Cholesterol

TC >239 mg/dL LDL > 159 mg/dL

Borderline High Cholesterol

Total Cholesterol (TC) 200-239mg/dL LDL 130-159mg/dL

Antioxidant Vitamins

Vitamin C, E, and beta-carotene (a provitamin) -inactivate oxygen free radicals -free radicals (highly reactive ions or molecules that carry an unpaired electron in their outermost electron shell. They damage cell membranes, DNA, other cellular structures, contribute to formation of atherosclerotic plaques. -protect against some kinds of cancers.

6 main types of nutrients

Water, Carbs, Proteins, Lipids, Vitamins, Minerals -Nutrient needed in largest amount: Water (provides the medium in which most metabolic reactions occur; also participates in some reactions- hydrolysis)

Postabsorptive state

absorption of nutrients from GI tract is complete -energy needs must be met by fuels already in the body. -Assuming no between-meal snacks, and other 12 hours- typically late morning, late afternoon, and most of the night- spent in postabsorptive state. -nervous system and RBCs depend on glucose forATP production during postabsorptive state>maintaining a steady blood glucose level is critical during this period.

Metabolism

all of the chemical reactions that occur in the body

What group is removed from an amino acid before it can enter the Krebs cycle, and what is this process called.

before an amino acid can enter the Krebs cycle, an AMINO group must be removed via DEAMINATION

Malnutrition

imbalance of total caloric intake or intake of specific nutrients, which can be either inadequate or excessive

Lipoprotein

lipid and protein combination. -lipids are nonpolar=hydrophobic- do not dissolve in water -must be transported by combining with proteins produced by liver and intestines. -Spherical particles with outer shell of protein, phospholipids, and cholesterol surrounding inner core of triglycerides and other lipids. -Proteins in outer shell= apoproteins (apo) -transport vehicles -provide delivery and pickup services so that lipids can be available when cells need them or removed from circulation when no needed. -Chylomicrons, Very-low-density lipoproteins (VLDLs), Low density lipoproteins (LDLs), and high-density lipoproteins (HDLs)

Once appropriate Essential and Nonessential amino acids are present in cells.....

protein synthesis occurs rapidly

Provitamins

raw materials that allow the body to assemble vitamins -eg. beta-carotene

Heatstroke

severe/fatal caused by high temps- esp when humidity is high (makes it difficult for body to lose heat). -blood flow to skin is decreased> perspiration is greatly reduced> body temprises sharply b/c of failure of hypothalamic thermostat. -cool body by immersing victim in cool water -administer fluids and electrolytes

Essential Nutrients

specific nutrient molecules that the body CANNOT make in sufficient quantity to meet its needs -Must be obtained by the DIET -Some amino acids, fatty acids, vitamins, and minerals are essential nutrients.

Neuropeptide Y

stimulates food intake

Shell Temperature

temperature near the body surface- in the skin and subcutaneous layer (usually about 1-6 degrees lower than core temp).