Chapter 25 - Metabolism and Nutrition

What processes are needed to produce all the ATP needed for cellular activities?

- Glycolysis - Krebs cycle - especially the Electron Transport chain - provide all the ATP needed for cellular activities. Krebs cycle and electron transport chain - are aerobic processes - they would not carry on for long without oxygen present.

What are the guidelines for healthy eating?

-Eat a variety of foods -Maintain a healthy weight -Choose foods low in fat, saturated fat, and cholesterol -Eat plenty of vegetables, fruits and grain products -Use sugars in moderation only

Steps in electron transport and chemiosmotic ATP generation.

1) Carriers of transport chain: - clustered into three complexes - within inner mitochondrial membrane - each act as H+ proton pumps - expel H+ from mitochondrial matrix - help to create an electrochemical gradient of H+. 2) Each proton pump: - transports electrons - pumps H+ 3) Oxygen: - helps form water 4) Proton Motive Force H+ build up makes: - one side of the inner mitochondrial membrane positively charged - compared to the other side Creating an electrochemical gradient - that has potential energy. 5) Proton Channels: - in mitochondrial membrane - allow H+ to flow back across the mitochondrial membrane - driven by the proton motive force 6) ATP is Generated - as H+ flows back H+ channels contain: - an enzyme - called ATP synthase. ATP synthase: - Enzyme that uses the proton motive force - to synthesize ATP from ADP and 1 phosphorous. Chemiosmosis: Responsible for - most of ATP produced during cellular respiration.

Describe Metabolism during Fasting and Starvation.

1) Fasting - Going without food - for many hours or a few days. 2) Starvation - Going without food or inadequate amounts of food for weeks or months Survive without food for: - 2 months or more - if drink water to prevent dehydration - Dependent upon amount of adipose tissue stored. Fasting and Starvation: 1) Nervous tissue and RBC: - produce ATP by using glucose 2) Insulin is lowered, cortisol increased: - slows pace of protein synthesis - promote protein catabolism = large supply of amino acids 3) Skeletal muscles: - have a large amount of protein in them - able to work for a long time without feeling drained. Days of Fasting: 1st Day: - Protein catabolism outpaces protein synthesis - 75 grams daily - old amino acids deaminated and used in gluconeogenesis - new amino acids are lacking. 2nd Day: - Blood glucose levels stabilized (65 mg/100 mL - 3.6 mmol/liter). Increased level of fatty acids in plasma. Lipolysis of triglycerides in adipose tissue releases glycerol - used for gluconeogenesis and fatty acids. Fatty acids diffuse into body cells and muscle fibers - used to produce acetyl CoA - that enters Krebs cycle. ATP synthesized as oxidation proceeds via the Krebs cycle and electron transport chain. After 2nd Day: - Ketone's are 100-300 times higher - supply brains fuel for ATP production. 40 Days of Starvation: - Ketone's provide 2/3 of brains energy needs - presence reduces the use of glucose for ATP production - decreases demand of gluconeogenesis - slows catabolism of muscle proteins - approximately 20 grams daily. Dramatic Metabolic Change: -Increase in formation of ketone bodies by hepatocytes. -Only small amounts of glucose are converted to pyruvic acid via glycolysis - which is converted to oxaloacetic acid - leads to only a little bit of acetyl CoA to enter Krebs cycle.

Figure 25.15: Points at which amino acids (yellow boxes) enter the Krebs cycle for oxidation.

Before amino acids are catabolized - they must first be converted to various substances that can enter the Krebs cycle. Phenylaline Converted To: - Tyrosin - Leucine - Lysine - Tryptophan - which are converted to Acetoacetyl CoA - converted to Acetyl CoA - enter Krebs Cycle. Converted to Pyruvic Acid: - Alanine - Cysteine - Glycine - Serine - Threonine - converted to Pyruvic Acid - converted to Acetyl CoA - enter Krebs Cycle. Converted to Acetyl CoA: - Isoleucine - Leucine - Tryptophan - converted to Acetyl CoA - enter Krebs Cycle. Converted to Oxaloacetic Acid: - Aspartic Acid - Asparagine - converted to Oxaloacetic Acid (already in Krebs Cycle) Converted to Fumaric Acid: - Phenylalanine - converted to Tyrosin - converted to Fumaric Acid (already in the Krebs Cycle). Converted to Succinyl CoA: - Isoleucine - Methionine - Valine - converted to Succinyl CoA (already in the Krebs Cycle). Converted to Alpha-ketoglutaric Acid: - Arginine - Histidine - Glutamine - Proline - converted to Glutamic Acid - converted to Alpha-ketoglutaric Acid (already in the Krebs cycle).

Describe Glucose movement into Cells

Before glucose is used in body cells. 1) Pass through: - plasma membrane - enter cytosol 2) Glucose absorption: - GI tract - kidney tubules Via: - secondary active transport - Na+ - glucose symporters 3) Glucose Transport: - through GluT molecules - family of transporters Occurs: - facilitated diffusion High insulin: - increases the insertion of GluT4 - into plasma membranes of most body cells - increasing rate of facilitated diffusion - of glucose into body cells 4) Entering cell - glucose becomes phosphorylated Phosphorylation of Glucose: - once inside cell - cannot be transported by GluT - traps glucose inside the cell

Figure 25.3: Cellular respiration begins with glyoclysis.

During glycolysis, - each molecule of glucose is converted - to two molecules of pyruvic acid.

Figure 25.4: The ten reactions of glucose.

Glycolysis: Results IN: - a net gain of - two ATP - two NADH - two H+ Reaction 1: - Glucose is phosphorylated - using a phosphate group from an ATP molecule - to form glucose 6-phosphate. Reaction 2: - Glucose 6-phosphate - converted to fructose 6-phosphate. Reaction 3: - A second ATP is added to fructose 6-phosphate - to form fructose 1,6-bisphosphate Phosphofructokinase - enzyme that catalyzes - key regulator of rate of glycolysis When low: - glucose does not enter the glyoclysis reaction - instead - undergoes conversion to glycogen for storage. Reaction 4/5 Fructose splits into: - two 3-carbon molecules - glyceraldehyde 3-phosphate (G 3-P) - dihydroxyacetone phosphate - each having one phosphate group. Reaction 6 Oxidation occurs as: - two molecules of NAD+ - accept two pairs of electrons and hydrogen ions - from two molecules of G 3-P - to form two molecules of NADH A second phosphate group: - attaches to G 3-P Forming: - 1,3-bisphosphoglyceric acid (BPG) Many body cells use: - the two molecules of NADH - to form 4 ATP - in the electron transport chain Hepatocytes, kidney cells, cardiac muscle fibers: - generate 6 ATP - from two NADH. Reactions 1-5 - Energy in the form of ATP is invested 6-carbon glucose is split: - into 3-carbon molecules - of glyceraldehyde 3-phosphate. Reactions 6-10 - Two glyceraldehyde 3-phosphate molecules - are converted to - two pyruvic acid molecules - and ATP is generated Reaction 7-10 These reactions generate: - four molecules of ATP Produce: - two molecules of pyruvic acid (pyruvate).

Describe Heat and Energy Balance.

Heat: - Form of energy - is measured by temperature, - expressed in units called calories. Calorie (cal): - Amount of heat required to raise the temperature of 1 gram of water 1 degree C. Kilocalorie (kcal) or Calorie (Cal): - Used to measure body's metabolic rate - express the energy content in foods - Equals 1000 calories.

How does muscle glycogen indirectly supply the liver with blood glucose?

Hepatocytes: - have the enzyme phosphotase - can release glucose into the blood stream Skeletal muscles: - cannot release glucose into the blood stream - they do not have enzyme phosphotase. - have glycogen broken down to glucose 1-phosphate - which is catabolized by the Krebs cycle and glycolysis Lactic acid: - produced by glycolysis in muscle cells - can be converted to glucose in the liver.

How does the body regulate metabolism in the postabsorptive state?

Hormones and the sympathetic nervous system - regulate metabolism - during the postabsorptive state. 1) Anti-insulin hormones - counter effect insulin - during the absorptive state. Blood glucose concentration drops Pancreatic alpha cells secrete: - glucagon - at a faster rate Pancreatic beta cells: - secrete insulin - slowly. Primary target of glucagon: - is the liver Major effect: - is increased release of glucose into the bloodstream - due to gluconeogenesis - and glycogenolysis. 2) Sympathetic branch of the ANS is activated: - with low blood glucose levels Glucose sensitive neurons in hypothalamus: - detect low blood glucose - increase sympathetic output Sympathetic nerve endings: - release neurotransmitter norepinephrine Adrenal medulla secretes: catecholamine hormones - epinephrine - norepinephrine Epinephrine: - stimulates glycogen breakdown Epinephrine and norepinephrine: - potent stimulators for lipolysis. 3) Action of Catecholamines Increase: - glucose and fatty acid levels in blood - muscle uses more fatty acids for ATP production - more glucose is available for the nervous system.

Describe the hypothalamic thermostat

Hypothalamus Preoptic Area - Control center in anterior part Receives impulses from: - thermoreceptors in skin and mucous membranes - hypothalamus Generate nerve impulses: - at higher frequency when blood temperature increases - lower frequency when blood temperature decreases. Nerve impulses from preoptic area in hypothalamus: - propagate to two parts of hypothalamus - called heat-losing center (lowers body temperature) - heat promoting center (increases body temperature).

Figure 25.8: Chemiosmosis

In chemiosmosis - ATP is produced - when H+ ions diffuse back - into the mitochondrial matrix.

What is the summary of cellular respiration?

Cellular Respiration - generates 36 or 38 ATP - from each molecule of glucose 2 from substrate-level phosphorylation: - in glycolysis 2 from substrate level phosphorylation: - in the Krebs cycle. Overall Reactions is: C6 H12 O6 + 6 O2 + 36 or 38 ADPs + 36 or 38 P = 6 CO2 + 6 H2O + 36 or 38 ATPs Electron Transport Chain: - generates 32-34 ATP - from each molecule of glucose that is oxidized. 28 or 30 from the - 10 molecules of NADH + H+ 2 from: - each of the 2 molecules of FADH2 (4 Total)

Describe Metabolic Rate

Metabolic Rate: - Overall rate at which metabolic reactions use energy. Basal Rate: - Under standard conditions - body quiet - resting and fasting. Basal Metabolic Rate: - Done by measuring amount of oxygen used - per kilocalorie of food metabolized. Example: - Body uses 1 liter of oxygen - to oxidize typical dietary mixture of triglycerides, carbohydrates, proteins = 4.8 Cal of energy released BMR is 1200-1800 Cal/day in adults - 24 Cal/kg of body mass in adult males - 22 Cal/kg of body mass in adult females Average calorie intake: - 500 - 3000 cal per day.

Define Metabolism

Metabolism: - All chemical reactions that occur in the body Two types: 1) Catabolism: - Chemical reactions that break down complex organic molecules - into simpler ones. Exergonic: - Produce more energy than they consume - releasing chemical energy stored in organic molecules. Examples: - Important exergonic processes - are seen in the Kreb's cycle - and electron transport chain 2) Anabolism: - Combine simple molecules and monomers - to form complex structural and functional components. Endergonic: - Consume more energy than they produce. Examples: - Formation of peptide bonds - between amino acids - during protein synthesis

Table 25.3: Hormonal Regulation of Metabolism in the Absorptive State.

Process - Location - Main Stimulating Hormones 1) Facilitated Diffusion of Glucose into Cell Most Cells - Insulin * facilitated diffusion of glucose into hepatocytes is always turned on and does not need insulin. 2) Active Transport of Amino Acids into Cells: Most Cells - Insulin 3) Glycogenesis (glycogen synthesis): Hepatocytes and Muscle Fibers - Insulin 4) Protein Synthesis: All body cells - Insulin, thyroid hormones, insulinlike growth factors. 5) Lipogenesis (triglyceride synthesis): Adipose cells and hepatocytes - Insulin.

Table 25.4: Hormonal Regulation of Metabolism in the Postabsorptive State.

Process - Locations - Main stimulating hormones 1) Glycogenolysis - Hepatocytes and skeletal muscle fibers - Glucagon and epinephrine. 2) Lipolysis (Triglyceride breakdown) - Adipocytes - Epinephrine, norepinephrine, cortisol, insulinlike growth factors, thyroid hormones, and others. 3) Protein Breakdown: Most body cells, mainly skeletal muscle fibers - Cortisol. 4) Gluconeogenesis (Synthesis of glucose from noncarbohydrates) - Hepatocytes and kidney cortex cells - Glucagon and cortisol.

How does heat production affect Metabolic Rate?

Production of body heat is proportional to metabolic rate. 1) Exercise: - Strenuous exercise metabolic rate increase - 15 times to basal rate - well trained athletes may increase 20 times. 2) Hormones Thyroid hormones: - thryoxine - triidothyronine - main regulators of BMR - they stimulate aerobic cellular respiration - increases oxygen consumption - producing heat - increasing body temperature BMR increases: - as blood levels of thyroid hormones increase Testosterone, insulin, human growth hormone: - increase metabolic rate 5-15%. 3) Nervous System During exercise or stressful situation: - sympathetic nervous systems postganglionic neurons - release norepinephrine - stimulates release of epinephrine and norepinephrine from adrenal medulla - increase metabolic rate of body cells. 4) Body Temperature Higher body temperature: - higher metabolic rate - increases rate of biochemical reactions by 10%. 5) Ingestion of Food Food raises metabolic rate: - 10-20% - due to energy needed to digest, absorb, and store nutrients. Food-induced thermogenesis: - highest after eating protein rich food (less after eating carbs and fats). 6) Age - Metabolic rate of a child is double - compared to an elderly person - due to reactions related to growth. 7) Other Factors Gender: - lower in females - except during pregnancy and lactation Others: - climate (lower in tropical regions) - sleeping (lower) - malnutrition (lower).

Describe Protein Metabolism

Proteins broken down into: - amino acids - not stored - are oxidized to produce ATP Synthesize new proteins for: - body growth - repair Excess dietary amino acids: - not excreted in feces or urine - are converted into glucose (gluconeogenesis) - or triglycerides (lipogenesis).

What is the regulation of metabolism in the absorptive state?

1) Glucose-dependent insulinotropic peptide (GIP) - rising levels of glucose and certain amino acids - stimulate pancreatic beta cells - to secrete insulin. 2) Insulin Increases activity of: - enzymes needed for anabolism - and synthesis of storage molecules Decreases activity of: - enzymes needed for catabolic reactions. Promotes entry of: - glucose - and amino acids - into body cells Stimulates conversion of: - glucose 6-phosphate - to glycogen - in liver and muscle cells Insulin enhances synthesis of: - triglycerides - in liver and adipose tissue. Insulin stimulates synthesis of: - protein - in other cells of the body. 3) Insulin-like Growth Factors and Thyroid Hormones (T3 and T4) - Stimulate protein synthesis.

Table 25.1: Summary of ATP produced in cellular respiration.

1) Glycolysis a) Oxidation of: - one glucose molecule - and two pyruvic acid molecules = 2 ATPs via -substrate-level phosphorylation b) Production of: - 2 NADH + H+ = 4 or 6 ATPs via - oxidative phosphorylation in electron transport chain 2) Formation of Two molecules of Acetyl Coenzyme A a) 2 NADH + 2 H+ = 6 ATPs via - oxidative phosphorylation in electron transport chain 3) Krebs Cycle and Electron Transport Chain a) Oxidation of succinyl-CoA to succinic acid = 2 GTPs - that are converted to 2 ATPs via - substrate-level phosphorylation b) Production of: - 6 NADH + 6 H+ = 18 ATPs Via: oxidative phosphorylation in electron transport chain c) Production of: - 2 FADH2 = 4 ATPs via oxidative phosphorylation in electron transport chain TOTAL = 36 or 38 ATPs per glucose molecule (theoretical maximum).

Explain Carbohydrate Metabolism

1) Polysaccharides and Disaccharides Hydrolyzed into Monosaccharides: - glucose (about 80%) - fructose - galactose during digestion of carbohydrates. 2) Fructose - converted into glucose - absorbed by epithelial cells Hepatocytes convert: - remaining fructose - most of galactose - into glucose. 3) Negative Feedback Mechanisms Maintain blood glucose: - at 90 mg/100 mL of plasma (5 mmol/liter) - total of 2-3 g of glucose normally circulates in the blood.

What are the three fates that food molecules have after being absorbed by the GI tract?

1. Supply Energy: - Active transport - DNA replication - protein synthesis - muscle contraction - maintenance of body temperature - mitosis. 2. Serve as Building Blocks For: - synthesis of more complex structural or functional molecules - proteins - hormones - enzymes. 3. Stored for Future Use Example: - glycogen stored in liver cells - triglycerides stored in adipose cells.

Describe Metabolism during the Postabsorptive State

4 Hours after the last meal - absorption of nutrients from small intestine almost complete - blood glucose level starts to fall - glucose continues to leave bloodstream to enter body cells - glucose not absorbed in the GI tract. Main metabolic challenge: - Maintaining blood glucose levels at 70-110 mg/100 mL (3.9-6.1 mmol/liter). Homeostasis important 1) Main fuel for nervous system ATP production is glucose - because fatty acids are unable to pass through the blood brain barrier. 2) RBC get all of their ATP from: - glycolysis of glucose - because they have no mitochondria - Krebs cycle and electron transport chain are not available to them.

Figure 25.13: A lipoprotein. VLDL

A single layer of amphipathic phospholipids, cholesterol, and proteins surrounds a core of non polar lipids. Apoproteins: Apo E, Apo C-2, Apo B100 Nonpolar Lipids: Cholesterol ester, Triglyceride Amphipathic Lipids: Phospholipid, Cholesterol

Describe the coupling of catabolism and anabolism by ATP

ATP Consists of an: - adenine molecule - ribose molecule - three phosphate groups - bonded to one another. Catabolic Reactions: Adinosine diphosphate + phosphate + energy = Adenosine triphosphate. ADP + P + Energy = ATP Energy from Catabolic Reactions Functions: 1) 40% of energy released for a catabolic reaction - used for cellular functions 2) Used for heat - to maintain normal body temperature.

Figure 25.12: Gluconeogenesis, the conversion of noncarbohydrate molecules (amino acids, lactic acid, glycerol) into glucose.

About 60% of the amino acids in the body - can be used for gluconeogenesis. Gluconeogenesis - stimulated by cortisol and glucagon.

What are some metabolic adaptions?

Absorptive State - Ingested nutrients are entering bloodstream - glucose is available for ATP production Three meals a day - absorptive state is 12 hours a day Dominated by effects of insulin. Postabsorptive State - Absorption of nutrients from GI tract complete - energy needs must be met by fuel needs already in body. Times where there are no meals (late morning, late afternoon, night). Complete Absorption - Takes approximately 4 hours - at three meals a day, absorptive state

Figure 25.5: Fate of pyruvic acid.

Acetyl Coenzyme A When oxygen is plentiful: - pyruvic acid enters mitochondria - is converted to acetyl coenzyme A - enters Krebs cycle (aerobic pathway). Lactic Acid When oxygen is scarce: - pyruvic acid is converted to lactic acid - via an anaerobic pathway

Explain the role of ATP in anabolism and catabolism.

Adenosine triphosphate (ATP): - Participates in energy exchanges in living cells - couples energy-releasing catabolic reactions to - energy-requiring anabolic reactions.

Describe Triglyceride Storage.

Adipose Tissue: 1) Removes trigylcerides from: - chylomicrons and VLDLs - store them - until needed for ATP production in other parts of body. 2) Triglycerides stored in: - adipose tissue - constitutes 98% of all energy reserves - mostly because they are hydrophobic - don't exert osmotic pressure on cell membranes 3) Insulates: - protects parts of body 4) Subcutaneous layer stores: - about 50% of all triglycerides 5) Other adipose tissue constitutes: - the other 50% of stored triglycerides - 12% in kidneys - 10-15% in omenta - 15% in genital areas - 5-8% between muscles - 5% behind the eyes, in sulci of heart, attached to outside of large intestine 6) Triglycerides in adipose tissue: - are broken down and resynthesized.

Figure 25.9: The actions of the three proton pumps and ATP synthase in the inner membrane of mitochondria.

As the three proton pumps pass electrons from one carrier to the next - they also move H+ protons from the matrix to the space between the inner and outer mitochondrial membranes. - As protons flow back into the mitochondrial matrix through the H+ channel in ATP synthase - ATP is synthesized. Each pump is complex of three or more electron carriers. 1) The first proton pump: NADH dehydrogenase complex Contains: - flavin mononucleotide (FMN) - five or more Fe-S centers NADH + H+: - is oxidized -to NAD+, FMN: - is reduced - to FMNH2 FMNH2: - is oxidized - as it passes electrons to the iron-sulfur centers Q: - which is mobile in the membrane - shuttles electrons to the second pump complex. 2) The second proton pump: Cytochrome b-c1 complex Contains: - cytochromes - and an iron-sulfur center Electrons are passed: - successively from - Q to cyt b - to Fe-S, to cyt 1 The mobile shuttle: Cytochrome C (cyt c) - passes electrons from the second pump complex - to the third 3) The third proton pump: Cytochrome oxidase complex Contains cytochromes: - a and a3 - and two copper atoms Electrons pass from: - cyt c, to Cu - to cyt a - finally to cyt a3 Cyt a3 passes electrons to: - one-half of a molecule of oxygen (O2) O2: - becomes negatively charged - picks up two H+ - from the surrounding medium - to form H2O.

Table 25.2: Summary of Metabolism

CARBOHYDRATES Glucose Catabolism - Complete oxidation of glucose (cellular respiration) - is chief source of ATP in cells Consists of: - glycolysis - Krebs cycle - electron transport chain Complete oxidation of 1 molecule of glucose: - yields maximum of 36-38 ATP molecules. a) Glycolysis - Conversion of glucose into pyruvic acid - results in production of ATP. -Reactions do not require oxygen (anaerobic cellular respiration). b) Krebs Cycle - Cycle includes series of oxidation-reduction reactions - 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 require oxygen (aerobic cellular respiration) c) Electron Transport Chain - Third set of reactions in glucose catabolism - another series of oxidation-reduction reactions - electrons are passed from one carrier to the next - most ATP produced - Reactions require oxygen (aerobic cellular respiration). Glucose Anabolism - Some glucose is converted to glycogen (glycogenesis) - for storage - if not needed immediately for ATP production - Glycogen can be reconverted to glucose (glycogenolysis) Gluconeogenesis - conversion of - amino acids - glycerol - lactic acid - to glucose LIPIDS Triglyceride Catabolism Triglycerides are broken down into: - glycerol and fatty acids Glycerol may be converted to: - glucose (gluconeogenesis) - or catabolized via glycolysis Fatty acids are catabolized: - via beta oxidation - into acetyl coenzyme A - that can enter Krebs cycle for ATP production - or be converted to ketone bodies (ketogenesis). Triglyceride Anabolism - Synthesis of triglycerides from glucose and fatty acids - is called lipogenesis - Triglycerides are stored in adipose tissue. PROTEINS Protein Catabolism - Amino acids are oxidized - via Krebs cycle deamination Ammonia resulting from deamination: - is converted to urea in liver - passed into blood - and excreted in urine Amino acids may be converted: - to glucose (gluconeogenesis) - fatty acids - or ketone bodies. Protein Anabolism - Protein synthesis - is directed by DNA - utilizes cells RNA and ribosomes.

Describe Glucose Catabolism

CELLULAR RESPIRATION - Oxidation of glucose to produce ATP. Involves: 1) Glycolysis - 1 glucose molecule oxidized = 2 molecules of pyruvic acid Also produces: - 2 molecules of ATP - 2 energy containing NADH + H+. Anaerobic Cellular Respiration: - Glycolysis does not require oxygen - to produce ATP. 2) Formation of Acetyl Coenzyme A - Transition step - prepares pyruvic acid for entrance into Krebs cycle Produces: - energy-containing NADH + H+ - plus carbon dioxide. 3) Krebs Cycle Reactions Oxidize: - acetyl coenzyme A Produce: - CO2 - ATP - NADH +H - FADH2. 4) Electron Transport Chain Reactions Oxidize: - NADH + H+ - FADH2 Transfer their electrons: - through a series of electron carriers. Aerobic Cellular Respiration: - The krebs cycle - electron transport chain - require oxygen to produce ATP.

MyPyramid Chart

Calorie Level at 2000 (18 adult female) and 2800 (18 adult male) Fruits (fresh, frozen, canned, dried, juices) 2 cups and 2.5 cups Vegetables (fresh, frozen, canned, dried, juices) 2.5 cups and 3.5 cups Grains (made from wheat, rise, oats, cornmeal, barley such as bread, cereals, oatmeal, rice, pasta, crackers, tortillas, grits) 6oz and 10 oz Meats and Beans (lean meat, poultry, fish, eggs, peanut butter, beans, nuts, seeds) 5.5 oz and 7 oz Milk Group (milk products and foods made from milk that retain their calcium content - cheeses and yogurt) 3 cups and 3 cups Oils (choose from fats containing monunsaturated and poyunsaturated fatty acids such as fish, nuts, seeds, and vegetable oils) 6 tsp and 8 tsp Sodium: Less than 2300 mg/day

What is carbohydrate loading?

Carbohydrate Loading: - Performed by long-term athletes - where they load up on carbohydrates (pasta, potatoes) 3 days before an event - helps to maximize the amount of glycogen available for ATP production in muscles. Increased endurance is due to glycogenolysis - results in more glucose that can be catabolized for energy.

Describe the formation of acetyl coenzyme A in Glucose Catabolism

Coenzyme A: - used to oxidize glucose - derived from pantothenic acid and a B vitamin. 1) Transitional step between glycolysis and the Krebs cycle - pyruvic acid prepared for entrance 2) Enzyme pyruvate dehydrogenase - located exclusively in the mitochondrial matrix - converts pyruvic acid to 2-carbon fragment - called an acetyl group - by removing a molecule of CO2 3) Acetyl Group formed by: - removing CO2 from pyruvic acid - to produce a 2-carbon fragment 4) Decarboxylation: - loss of a molecule of CO2 by a substance First reaction in cellular respiration: - that releases CO2 - Pyruvic acid also oxidized 5) Pyruvic acid loses: - two H+ atoms In the form of: - one hydride ion (H-) - one hydrogen ion (H+) 6) Coenzyme NAD+ is reduced: - as it picks up the hydride (H-) ion - from pyruvic acid 7) The hydrogen (H+) ion is released: - into mitochondrial matrix 8) Acetyl coenzyme A: - produced by an Acetyl group - attaching to coenzyme A. Oxidation of glucose produces: - 2 molecules of pyruvic acid - two molecules of CO2 are lost - two NADH + H+ are produced.

Describe Body Temperature Homeostasis.

Core Temperature: - 37 C (98.6 F) - Temperature in the body structures deep to skin and subcutaneous layer. Shell Temperature: - Temperature near the body surface - in skin and subcutaneous layer - (1-6 C lower than core temperature).

Describe thermoregulation.

Core temperature declines: - mechanisms start to conserve heat - increase heat production - via negative feedback mechanism. 1) Thermoreceptors in skin and hypothalamus Send impulses to: - preoptic area and heat-promoting center in hypothalamus - hypothalamic neurosecretory cells Produce: - thyrotropin-releasing hormone (TRH). 2) Hypothalamus sends impulses Secretes: - TRH TRH stimulates: - thyrotrophs - in anterior pituitary gland - to release thyroid-stimulating hormone (TSH) 3) Nerve impulses from hypothalamus and thyroid-stimulating hormone Activate several effectors: - effectors respond by increasing core temperature. a) Nerve impulses from heat-promoting center Stimulate sympathetic nerves to: - constrict blood vessels in skin Vasoconstriction: - decreases flow of warm blood (transfer of heat) from internal organs to skin - slowing rate of heat loss - internal body temperature increases - as metabolic reactions continue to produce heat. b) Sympathetic nerve impulses: - send signal to adrenal medulla - to secrete epinephrine and norepinephrine - which increase cellular metabolism - increases heat production. c) Heat-promoting center Stimulates part of body: - that produces muscle tone - producing heat Produces: - shivering (alternating contraction and relaxation of antagonist and agonist) - increases rate of heat production. d) Thyroid gland Responds to TSH: - by releasing more thyroid hormones in blood Increased thyroid hormones in blood: - increases metabolic rate - body temperature increases. Core Temperature Rises above Normal: Negative feedback mechanism - reduces heat loss. 1) Thermoreceptors stimulated: - sends nerve impulses to heat-losing center in hypothalamus - inhibits heat-promoting center 2) Heat-losing center: - dilates blood vessels in skin - skin becomes warm - heat lost via radiation and conduction - as increased blood flows from warmer areas to cooler areas. 3) Metabolic rate decreases: - shivering does not occur 4) High blood temperature: - stimulates sweat glands - via hypothalamic sympathetic nerves - water evaporates from skin - skin is cooled.

Figure 25.19: Negative feedback mechanisms that conserve heat and increase heat production.

Core temperature: - is the temperature in body structures - deep to skin and subcutaneous layer Shell temperature: - is the temperature near the body surface. Some stimulus disrupts homeostasis by decreasing Body temperature Receptors - Thermoreceptors in skin and hypothalamus Send input via nerve impulses Control Centers - preoptic area, heat-promoting center and neurosecretory cells in hypothalamus and thyrotropes in anterior pituitary gland. Send output via nerve impulses and thyroid-stimulating hormone Effectors - Vasoconstriction decreases 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. Increases body temperature Return to homeostasis when response brings body temperature back to normal.

Describe the postabsorptive state reactions.

During postabsorptive state - Glucose production and glucose conservation - maintain blood glucose levels Hepatocytes produce: - glucose molecules - export them into blood Body cells use: - alternative ways to produce ATP - to conserve the glucose. 1) Breakdown of liver glycogen - During fasting - liver glycogen can be broken down by the liver - to supply about 4 hours of glucose. 2) Lipolysis - Breakdown of triglycerides - in adipose tissue produces glycerol - can be used to form glucose. 3) Gluconeogenesis using Lactic Acid - During exercise - skeletal muscles break down glycogen - produces ATP anaerobically The pyruvic acid that is made: - is converted to acetyl CoA - some converted to lactic acid The lactic acid undergoes: - gluconeogenesis in the liver - to produce glucose - glucose is released into the blood. 4) Gluconeogenesis using Amino Acids - Modest break down of proteins - in skeletal muscles and other tissues - can produce large amount of amino acids The amino acids are converted to: - glucose - via gluconeogenesis in the liver. Following reactions that produce ATP: - WITHOUT using glucose 5) Oxidation of Fatty Acids - Fatty acids released by lipolysis of triglycerides Cannot be used for glucose production: - because acetyl CoA - cannot be converted to pyruvic acid Fatty acids are oxidized: - sent into the Krebs cycle as acetyl CoA - to produce ATP - through the electron transport chain. 6) Oxidation of Lactic Acid - Cardiac muscle produces ATP aerobically - by using lactic acid. 7) Oxidation of Amino Acids - Amino acids can be oxidized directly - to produce ATP in hepatocytes 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 - undergoes glycolysis - to provide ATP - for muscle contraction.

Figure 25.17: Principal Metabolic Pathways during the Absorptive State.

During the absorptive state, most body cells produce - ATP - by oxidizing glucose - to CO2 and H2O.

Describe the Electron Transport Chain

ELECTRON TRANSPORT CHAIN Series of electron carriers: - reduced as it picks up electrons - oxidized as it loses electrons As electrons pass through the chain: - a series of exergonic reactions occur - releasing energy - used to make APT. Electron Carriers: - integral membrane proteins - in inner mitochondrial membrane Mitochondrial Membrane: - folded into cristae to increase surface area - accommodates thousands of copies of the transport chain - in each mitochondrion. Aerobic Cellular Respiration: - Final electron acceptor in the chain - is oxygen. Chemiosmosis: - Mechanism of ATP generation - links chemical reactions - passage of electrons along the transport chain - with the pumping of hydrogen ions Three mechanisms: 1) Proton Pump - energy from NADH + H+ - passes along the electron transport chain Is used to pump H+: - from the matrix of the mitochondrion TO - space between inner and outer mitochondrial membranes Called a proton pump because: H+ consists of a single proton. 2) A high concentration of H+: - accumulates between the inner and outer mitochondrial membranes. 3) ATP synthesis occurs when: - the H+ flows back into the mitochondrial matrix - through H+ channels in the membrane

Describe energy homeostasis and regulation of food intake.

Energy homeostasis: - Precise matching of food intake to energy expenditure over time. Energy intake depends: 1) Basal metabolic rate accounts for: - 60% of energy expenditure. 2) Physical activity: - adds 30-35% energy expenditure - voluntary exercise - and non-exercise thermogenesis (energy costs for maintaining muscle tone, posture while sitting or standing and involuntary fidgeting movements). 3) Food-induced Thermogenesis - Heat produced while food is digested, absorbed, and stored - represents 5-10% of total energy expenditure. Satiety: - Hypothalamus contains clusters of neurons - that regulate food intake - arcuate nucleus and paraventricular nucleus. Leptin and Insulin: - Leptin Acts on hypothalamus - inhibit circuits stimulating eating - activates circuits to increase expenditure - Insulin smaller effect Both pass blood-brain barrier. - Stimulates release of melanocortin neurotransmitter from neurons extending between the arcuate nucleus and paraventricular nucleus - controls eating. Low leptin and insulin levels: Neuropeptide Y neurotransmitter is released from neurons extending from arcuate nucleus to paraventricular nucleus - stimulates eating. Hormones to increase satiety - increase energy expenditure: Glucagon, cholecystokinin, estrogen, epinephrine (acting via beta receptors). Hormones to increase appetite - decrease energy expenditure: Growth hormone-releasing hormone, androgen, glucocorticoids, epinephrine (acting via alpha receptors) and progesterone.

Figure 25.10: Summary of the principal reactions of cellular respiration. ETC = electron transport chain and chemiosmosis

Except for glyoclysis: - which occurs in the cytosol All other reactions of cellular respiration: - occur within mitochondria.

What molecules and atoms serve as electron carriers?

Flavin Mononucleotide (FMN): - Flavoprotein - derived from riboflavin (vitamin B2) Cytochromes: - Proteins with iron-containing heme group - able to exist as a reduced form (Fe2+) - and oxidized form (Fe3+). Cytochromes involved in the electron transport chain - cytochrome b (cyt b) - cytochrome c1 (cyt c1) - cytochrome c (cyt c) - cytochrome a (cyt a) - cytochrome a3 (cyt a3). Iron-sulfur (Fe-S) Centers: - Contain 2-4 iron atoms - bound to sulfur atoms - form electron transfer center within a protein. Copper (Cu) Atoms: - Bound to two proteins in the chain - also participate in electron transfer. Coenzyme Q, or Q, is a: - nonprotein - low-molecular-weight carrier - mobile in the lipid bilayer of the inner membrane.

Key Molecules at Metabolic Crossroads: Explain the role of glucose 6-phosphate

GLUCOSE 6-PHOSPHATE Glucose enters body cell: - kinase converts it to glucose 6-phosphate. 1) Synthesis of Glycogen - Glucose 6-phosphate synthesizes glycogen Occurs mainly in: - skeletal muscle fibers - hepatocytes. 2) Release of glucose into the bloodstream - mainly by hepatocytes Enzyme glucose 6-phosphotase: - dephosphorylates - glucose 6-phosphate - into glucose Once glucose is released from phosphate group: - it leaves cell - enters blood stream. 3) Synthesis of Nucleic Acids - Glucose 6-phosphate - precursor to make - ribose 5-phosphate Ribose 5- Phosphate - a 5-carbon sugar - needed for synthesis of RNA (ribonucleic acid) - and DNA (deoxyribonucleic acid) Also produces NADPH: - hydrogen and electron donor - in certain reduction reactions - like synthesis of fatty acids and steroid hormones. 4) Glycolysis - Some ATP is produced anaerobically via glycolysis - glucose 6-phosphate is converted to pyruvic acid - key molecule in metabolism - Most body cells carry out glycolysis.

Describe the Glycolysis step in glucose catabolism

GLYCOLYSIS - catabolic Chemical reaction Splits: 6-carbon molecule of glucose = 3-carbon molecules of pyruvic acid. Consumes: 2 ATP molecules Produces: - 4 ATP molecules = net gain of 2 ATP molecules - for each glucose molecule that is oxidized.

What is phenylketonuria?

Genetic error of protein metabolism. Characteristics - Elevated blood levels of amino acid phenylaline - Children have mutation in gene codes for the enzyme phenylaline hydroxylase - enzyme needed to convert phenylaline into amino acid tyrosine - that can enter the Krebs cycle. Deficient enzyme - build up of phenylaline in the blood - can lead to vomiting - rashes - seizure - growth deficiency - severe mental retardation. Prevention: - Screening new born - restricting diet - only an amount of phenylaline needed for growth.

What is the fate of glucose in metabolism

Glucose - preferred source for synthesizing ATP for energy - is dependent on the needs of body cells. 1) ATP Production - Body cells that require immediate energy - glucose is oxidized to produce ATP Glucose that is not needed for ATP production - enters one of several other metabolic pathways. 2) Amino Acid Synthesis - Cells in body use glucose to form several amino acids - to be used in forming proteins 3) Glycogen Synthesis Occurs In: - Hepatocytes - muscle fibers Undergo Glycogenesis: - hundreds of glucose monomers - combined to form polysaccharide glycogen Glycogen: - storage molecule of glucose - 125 g of glycogen stored in liver * - 375 g of glycogen stored in skeletal muscles. 4) Triglyceride Synthesis - Glycogen storage areas filled Lipogenesis: - synthesis of triglycerides - Hepatocytes convert glucose to glycerol and fatty acids Triglycerides Deposited Into: - adipose tissue - has virtually endless storage capacity.

Figure 25.14: Pathways of lipid metabolism

Glycerol and fatty acids: - are catabolized in separate ways. Glycerol may be converted to: - glyceraldehyde 3-phosphate - which can be converted to glucose - to enter Krebs cycle for oxidation. Fatty acids undergo: - beta oxidation - enter Krebs cycle - via acetyl coenzyme A. Lipogenesis: - The synthesis of lipids - from glucose and amino acids

Figure 25.11: Glycogenesis and glycogenolysis

Glycogenesis pathway: - converts glucose - into glycogen Glycogenolysis pathway: - breaks down glycogen - into glucose.

Describe metabolism during the absorptive state.

Ingested food reaches blood as: - glucose - amino acids - triglycerides (chylomicrons). Pinpoint for Absorptive State: 1) Oxidation of glucose for ATP production - occurring in most body cells 2) Storage of excess fuel molecules - for future between meal use Occurs mainly in: - hepatocytes - adipocytes - skeletal muscle fibers. Absorptive State Reactions. 1) 50% of glucose absorbed - is oxidized by cells throughout the body - for ATP production Via: - glycolysis - Krebs cycle - electron transport chain. 2) Most glucose that enters hepatocytes - converted to glycogen Small amounts used for synthesis of: - fatty acids - glyceraldehyde 3-phosphate. 3) Some fatty acids and triglycerides - are stored in hepatocytes - others are packaged into VLDLs that carry lipids to adipose tissue for storage. 4) Adipocytes take up glucose not picked up by the liver - convert it to triglycerides for storage - 40% of glucose converted to triglycerides - 10% of glucose stored as glycogen in skeletal muscles and hepatocytes. 5) Most dietary lipids - mainly triglycerides and fatty acids - are stored in adipose tissue - only small portion used for synthesis reactions Adipocytes obtain lipids from: - chylomicrons - VLDLs - from their own synthesis reactions. 6) Some absorbed amino acids that enter hepatocytes - are deaminated into keto acids - they enter the Krebs cycle for ATP production - or are used for synthesis of glucose or fatty acids. 7) Some amino acids that enter hepatocytes - are used to synthesize proteins (example: plasma proteins). 8) Amino acids not taken up by hepatocytes - are used in other body cells (such as muscle cells) - for synthesis of proteins - or regulatory chemicals such as hormones or enzymes.

What is the fate of proteins?

Insulinlike growth factors and insulin - stimulate amino acids - to be actively transported into body cells. Immediately after digestion: - amino acids reassembled into proteins. Protein Functions - As enzymes - transport hemoglobin - serve as antibodies - clotting chemicals (fibrinogen) - hormones (insulin) - contractile elements in muscle fibers (actin, myosin) Serve as: - structural components of body - collagen - elastin - keratin

Describe the Krebs cycle step in Glucose Catabolism

KREBS CYCLE or CITRIC ACID CYCLE - Named after biochemist Hans Krebs. Begins once Pyruvic acid has undergone: - decarboxylation (removal of CO2) Remaining acetyl group has: - attached to CoA - to form acetyl coenzyme A. Reactions occur in: - mitochondrial matrix Consists of: - series of oxidation-reduction reactions - and decarboxylation reactions - that release CO2 1) Oxidation-reduction reactions - transfer chemical energy - in form of electrons - two coenzymes NAD+ and FAD. 2) Pyruvic Acid derivatives - are oxidized - coenzymes reduced. 3) Reduced coenzymes - NADH and FADH2 - most important in Krebs cycle Contain energy: - originally stored in glucose - now stored in pyruvic acid 4) Every acetyl CoA that enters Krebs cycle: - three NADH - three H+ - one FADH2 Produced by: - oxidation-reduction reactions 1 molecule of ATP is generated: - by substrate-level phosphorylation. 5) In electron transport chain: Three NADH + 3 H+ - will later yield: - 9 ATP molecules The FADH2 - will later yield: - two ATP molecules. 6) Each turn of the Krebs cycle: - will generate - 24 molecules of ATP. 7) Release of CO2 occurs: - as pyruvic acid - is converted to acetyl coA - during the two decarboxylation reactions - of the Krebs cycle. 8) Each molecule of glucose generates: - two molecules of pyruvic acid That means that six molecules of CO2 are liberated - from each original glucose molecule catabolized. 9) Molecules of CO2 diffuse out of Mitochondria: - through cytosol and plasma membrane into - blood. 10) Blood transports CO2 to the lungs: - to be exhaled.

What is ketosis?

Ketosis - High level of ketone bodies in the blood Due to: - excessive beta oxidation - ketone bodies are produced - not enough taken into body cells Ketone bodies must be buffered: - too many accumulate Cause pH: - to drop Due to: - decreased buffers - such as bicarbonate ion. Occur: - After meal rich in triglycerides - during fasting or starvation - few carbohydrates available for catabolism. Excessive Beta Oxidation Due to: - poorly controlled or untreated - diabetes mellitus 1) Adequate glucose cannot: - get into cells - triglycerides are used for ATP production 2) Insulin normally inhibits: - lipolysis - lack of insulin accelerates lipolysis. Acidosis (ketoacidosis) - Extreme or prolonged ketosis - abnormally low pH Can lead to: - depression central nervous system - disorientation - coma - death.

Describe Transport of Lipids by Lipoproteins during Lipid Metabolism

LIPIDS - Hydrophobic - do not dissolve in water - Have a low density. Lipid Transportation in Watery Blood - Lipids must be bound - to proteins produced by the liver and intestine. Lipoproteins - Lipid and protein combinations - are spherical particles Outer Shell: - Proteins - phospholipids - cholesterol. Inner Core: - Triglycerides - other lipids - Most are for transport - Categorized and named according to density - varies with ratio of lipids (low density) and proteins (high density). Apoproteins - Proteins in outer shell of lipoproteins Designated by letters: A, B, C, D, E plus a number - each has specific functions. Four Types of Lipoproteins - categorized by largest and heaviest - to smallest and lightest: 1) Chylomicrons - Formed in mucosal epithelial cells of small intestine - Transport dietary (ingested) lipids to adipose tissue for storage. Enter lacteals of intestinal villi - Carried to lymph - Into venous blood - Into systemic circulation (gives blood a milky appearance, remains in blood for only a few minutes). Apoprotein C-2 activates: - the enzyme endothelial lipoprotein lipase enzyme - removes fatty acids from chylomicron triglycerides Three fatty acids: - taken by adipocytes for storage and synthesis - as triglycerides - and by muscle cells for ATP production Hepatocytes remove chylomicrons: - from blood - via receptor mediated endocytosis - using the apoprotein apo E as a docking protein. Contain: - 1-2% proteins - 85% triglycerides - 7% phospholipids - 6-7% cholesterol - small amount of fat-soluble vitamins. 2) Very-low-density Lipoproteins (VLDLs): - Form in hepatocytes - contain endogenous (main in body) lipids. Transport triglycerides: - synthesized by hepatocytes - to adipocytes for storage Lose triglycerides: - as their apo C-2 activates endothelial lipase Released fatty acids: - are taken up by adipocytes for storage - and by muscle cells for ATP production VLDL converted to LDL: - As triglycerides are deposited in adipose cells Contain: - 10% proteins - 50% triglycerides - 20% phospholipids - 20% cholesterol. 3) Low-density Lipoproteins (LDLs): Function: - Deliver cholesterol to cells in the body for use in repair of cell membranes - synthesis of steroid hormones and bile salts. Contain: - a single apoprotein apo B100 - used as a docking protein - binds to LDL receptors on plasma membrane of body cells - so that LDL can enter cell - via receptor-mediated endocytosis Within cell: - LDL is broken down - cholesterol is released Negative Feedback Mechanism: - activated once cell has enough cholesterol to perform its duties - inhibits the cell's synthesis of new LDL receptors LDL deposit cholesterol: - in and around smooth muscle fibers in arteries - forms fatty plaques - increase risk of coronary artery disease. LDL- cholesterol: - Considered bad because of the risk of forming fatty plaques - Reducing fat intake can decrease the risk. Contain: - 25% proteins - 5% triglycerides - 20% phospholipids - 50% cholesterol Carry 75% of total cholesterol in the blood. 4) High-density Lipoproteins (HDLs):\ Functions: - Removes excess cholesterol from body cells and blood - transports to liver for elimination - Prevent accumulation of cholesterol in blood - HDLs are associated with decreased risk of coronary artery disease - HDL-cholesterol is a "good" cholesterol. Contain: - 40-50% proteins - 5-10% triglycerides - 30% phospholipids - 20% cholesterol.

Describe Lipid Anabolism: Lipogenesis

LIPOGENESIS Liver and adipose cells synthesize: - lipids from glucose or amino acids Stimulated by: - insulin Occurs when: - people consume more calories - than needed for ATP needs. Excess: - Dietary carbohydrates - proteins - fats - all converted to triglycerides. A) Certain amino acids - Amino acids - acetyl CoA - fatty acids - triglycerides Undergo certain pathways B) The use of glucose to form lipids: - takes place via two pathways: 1) Glucose - glyceraldehyde 3-phosphate - glycerol. 2) Glucose - glyceraldehyde 3-phosphate - acetyl CoA - fatty acids. Resulting glycerol and fatty acids undergo: - anabolic reactions to become stored triglycerides - or go through anabolic reactions - to produce lipids - lipoproteins, phospholipids, cholesterol.

Describe Lipid Catabolism: Lipolysis

Lipolysis: - Splitting of triglycerides into fatty acids and glycerol. Lipases: - Enzymes that catalyze lipolysis. Lypolytic Hormones: Epinephrine and Norepinephrine Enhance: - triglyceride breakdown into fatty acids and glycerol Released when: - sympathetic tone increases - during exercise - Cortisol - thyroid hormones - insulinlike growth factors. Insulin: - Inhibits lipolysis. Catabolism of Glycerol: - Glycerol converted by many cells to glyceraldehyde 3-phosphate (one compound formed during catabolism of glucose) If ATP is high: - glyceraldehyde 3-phosphate converted - to glucose If ATP supply is low: - glyceraldehyde 3-phosphate enters - catabolic pathway to pyruvic acid. Catabolism of Fatty Acids: - Catabolized differently than glycerol and yield more ATP. 1) Beta oxidation: FORMS acetyl CoA - occurs in matrix of mitochondria - enzymes remove two carbon atoms at a time from - the fatty acid long chain carbon atoms and attach - the resulting two-carbon fragment to coenzyme A - forming acetyl CoA 2) Acetyl CoA enters Krebs cycle Palmitic Acid - A 16-carbon fatty acid Yields: - 129 ATP in - beta oxidation - the Krebs cycle - electron transport chain. Acetoacetic Acid - Formed by hepatocytes condensing - two acetyl CoA molecules Liberates: - the bulky CoA portion - which doesn't diffuse easily out of cells Acetoacetic Acid can be converted: - to beta-hydroxybutric acid and acetone Cannot be used in: - the formation of ATP - because hepatocytes lack an enzyme to convert it - back to coenzyme A. Ketone Bodies - Beta-hydroxybutric acid and acetone Formed by: - the conversion of acetoacetic acid - in the process of ketogenesis Freely diffuse through: - plasma membranes Leave: - hepatocytes - TO enter bloodstream.

Describe the formation of glucose from proteins and fats: Gluconeogenesis

Liver runs low on glycogen: - it is time to eat If you don't: - body starts to catabolize - trigylcerides (fats) and proteins. Gluconeogenesis Break down of: - non-carbohydrate sources - to form glucose 60% of amino acids in body: - converted to glucose - via gluconeogenesis Stimulated by: - cortisol - main glucocorticoid hormone of adrenal cortex - glucagon from the pancreas. Lactic Acid and Amino Acids - alanine - cysteine - glycine - serine - threonine - converted to pyruvic acid - to be synthesized into glucose - and enter the Krebs cycle. Glycerol - Can be converted into glyceraldehyde 3-phosphate - which can form pyruvic acid - or be used to synthesize glucose. Cortisol - Stimulates breakdown of proteins - into amino acids - to be available for gluconeogenesis. Thyroid Hormones - Thyroxine - Triiodothyronine Mobilize: - proteins and possible triglycerides - from adipose tissue - making glycerol available for gluconeogenesis.

What is hypothermia?

Lowering of core body temperature to 35 C or below. Causes: - Overwhelming cold stress (immersion in icy water) - metabolic diseases (hypoglycemia, adrenal insufficiency, hypothyroidism) - drugs (alcohol, antidepressants, sedatives, tranquilizers) - burns - malnutrition. Signs: - Shivering - sensation of cold - confusion - vasoconstriction - muscle rigidity - bradycardia - acidosis - hypoventilation - hypotension - loss of spontaneous movement - coma - death (caused by cardiac arrhythmias) - Elderly at greater risk because of low metabolic rate, reduced perception of cold.

Describe mechanisms of heat transfer.

Maintaining normal body temperature: - depend upon losing heat to environment - at same rate as heat produced during metabolic reactions. Heat transferred by: - conduction - convection - radiation - evaporation. 1) Conduction Heat exchange that occurs: - when two molecules come in contact with each other - 3% lost to solid materials during rest (chair, jewelry, etc). Heat gained: - water conducts 20 times more heat than air. 2) Convection - Transfer of heat by movement of fluid (gas or liquid) - between areas of different temperature - 15% body heat lost to air via convection and conduction. 3) Radiation - Transfer of heat in form of infrared rays - between warmer object and a cooler one - without physical contact - 60% heat loss occurs via radiation in a resting person. 4) Evaporation - Conversion of liquid to vapor - 22% of heat loss occurs with evaporation. Insensible Water Loss - Water loss through skin and mucous membranes of mouth and respiratory system - that we are not consciously aware of Higher relative humidity: - less evaporation - Main defense in overheating during exercise.

What are minerals

Minerals: Inorganic elements that occur naturally on earth's crust. In body are in combination with one another, combination with organic compounds, or as ions in a solution. Constitute 4% body mass - concentrated mostly in skeleton. Minerals Include: Calcium, phosphorous, potassium, sulfur, sodium, chloride, magnesium, iron, iodide, manganese, copper, cobalt, zinc, fluoride, selenium, chromium. Other minerals (functions unclear): Aluminum, boron, silicon, molybdenum. Roles: Calcium and phosphorous forms matrix of bone. Regulate enzymatic reactions. Calcium, iron, magnesium, manganese constituents of coenzymes. Magnesium is a catalyst for conversion of ADP to ATP. Sodium and phosphorous work in buffer systems - control pH in body fluids. Sodium regulates osmosis of water. Sodium and other ions generate nerve impulses.

Figure 25.20: MyPyramid

MyPyramid is a personalized approach to making healthy food choices and maintaining regular physical activity.

What reduced coenzymes are most important in the Krebs cycle?

NADH and FADH2 - they contain the energy originally stored in glucose - now stored in pyruvic acid.

What are nutrients?

Nutrients: Chemical substances in food that body cells use for growth, maintenance and repair. Six Types of Nutrients: Water (need 2-3 liters), carbohydrates, lipids, proteins, vitamins, minerals. Essential Nutrients: Specific nutrient molecules that body cannot make efficiently to meet needs - must be obtained from diet.

Describe oxidation-reductions reactions during energy transfer.

OXIDATION - Removal of electrons from an atom or molecules - decreases potential energy of atom or molecule. Dehydrogenation Reactions (oxidation reaction) Example: Conversion of lactic acid into pyruvic acid. Lactic Acid - Oxidation removes 2 H (H+ + H-) = Pyruvic Acid. 2 H means that: - two neutral hydrogen ions are removed - and becomes one hydrogen ion (H+) plus one hydride ion (H-). REDUCTION - Addition of electrons to a molecule - Increases potential energy of the molecule Example: Conversion of pyruvic acid into lactic acid. Pyruvic Acid - Reduction adds 2 H (H+ + H-) = Lactic Acid OXIDATION AND REDUCTION REACTIONS Oxidation-reduction reactions: - Always coupled - one substance is oxidized - while the other substance is reduced simultaneously. 1) Nicotinamide adenine dinucleotide (NAD) Derivative of: - B niacin vitamin - flavin adenine Nicotinamide adenine dinucleotide (NAD) - niacin derivative Oxidized NAD+ - 2H (H+ + H-) = Reduced NADH + H+ Reduced NADH+ + H+ +2H (H+ + H-) = Oxidized NAD+ 2) Flavin adenine dinucleotide (FAD) Derivative of: - B2 riboflavin vitamin Flavin adenine dinucleotide (FAD) - riboflavin derivative Oxidized FAD +2 H (H+ + H-) = Reduced FADH2 Reduced FADH2 -2 H (H+ + H-) = Oxidized FAD

Figure 25.2: Overview of cellular respiration (oxidation of glucose).

Oxidation of glucose involves: - glycolysis - formation of acetyl coenzyme A - the Krebs cycle - electron transport chain. 1. Glycolysis 2. Formation of acetyl co-enzyme A 3. Krebs Cycle 4. Electron Transport Chain.

Describe the Fate of Lipids

Oxidized to produce ATP - stored in adipose tissue throughout the body Used as: - structural molecules - to synthesize other essential substances. Examples: - Phospholipids - part of plasma membranes - lipoproteins - used to transport cholesterol throughout the body - thromboplastin - needed for blood clotting - myelin sheaths - speed up nerve impulse conduction. Essential Fatty Acids: - Body cannot synthesize linoleic acid, linolenic acid - Come from vegetable oils, and leafy vegetables.

Describe Protein Anabolism

PROTEIN ANABOLISM Formation of peptide bonds: - between amino acids - to produce more proteins Carried out on: - ribosomes of almost every cell of the body It is directed by: - DNA - RNA. Protein Synthesis Stimulated by: - insulinlike growth factors - insulin - thyroid hormones (T3 and T4) - estrogen - testosterone. Essential Amino Acids: 10. Are present in diet - cannot be synthesized in body adequately Humans unable to synthesize 8 amino acids: - isoleucine - leucine - lysine - methionine - phenylalanine - threonin - tryptophan - valine Can synthesize: - arganine - histadine. Complete Protein: - Sufficient amounts of all amino acids - Beef - fish - poultry - eggs - milk Incomplete Protein - Does not contain all essential amino acids Include: - leafy green vegetables - legumes (beans and peas) - grains. Nonessential Amino Acids: - Can be synthesized by the body. Transamination: - Nonessential amino acids formed in this way - by transferring an amino group from an amino acid to - pyruvic acid - an acid in the Krebs cycle.

Describe protein catabolism.

PROTEIN CATABOLISM Stimulated mainly by: - cortisol from adrenal cortex Worn-out cells (RBCs): - broken down into - amino acids - peptide bonds re-formed - new proteins synthesized. Hepatocytes convert: - amino acids to - fatty acids - ketone bodies - or glucose. Oxidizing Protein - by Cells throughout body For: - ATP production Through: - the Krebs cycle - electron transport chain Protein must be converted: - to molecules that are part of the Krebs cycle - or those that can enter the Krebs cycle (acetyl CoA) 1) Deamination: - Amino group removed - occurs in hepatocytes - produces ammonia (NH3) 2) Liver cells convert: - the really toxic ammonia - to urea (substance secreted in urine). Conversion of amino acids - Amino Acids to glucose (gluconeogenesis) - Amino acids to - fatty acids (lipogenesis) - Amino acids to - ketone bodies (ketogenesis)

Key Molecules at Metabolic Crossroads: The role of pyruvic acid.

PYRUVIC ACID - 3-carbon molecules Formed through: - the glycolysis of 6-carbon molecule of glucose. Oxygen needed for cellular respiration to proceed. 5) Production of Lactic Acid Not enough oxygen: - during active contraction of skeletal or cardiac muscle - pyruvic acid changes into - lactic acid Lactic acid enters bloodstream: - taken up by hepatocytes - can eventually change it back to - pyruvic acid. 6) Production of Alanine Carbohydrate and protein metabolism are linked to pyruvic acid Through transamination: - an amino group (-NH2) - can be added to amino acid - produce alanine or be removed from alanine - to generate pyruvic acid. 7) Gluconeogenesis - Pyruvic acid and some amino acids - can be converted to oxaloacetic acid (Krebs cycle intermediate) - can be used to form glucose 6-phosphate - This can often bypass the glycolysis steps.

Mechanisms of ATP Generation.

Phosphorylation: Adding a phosphate group - to a molecule - increases its potential energy. Three mechanisms of phosphorylation 1) Substrate-level Phosphorylation Generates ATP by: - transferring a high-energy phosphate group - from an intermediate phosphorylated metabolic compound - using a substrate (molecule which an enzyme reacts with) - directly to ADP. 2) Oxidative Phosphorylation: - occurs in inner mitochondrial membrane of cells Removes electrons from: - organic compounds Passes them through: - a series of electron acceptors - called the electron transport chain - to molecules of O2 3) Photophosphorylation - Only in chlorophyll- containing plant cells - or in certain bacteria that contain light-absorbing pigments.

Describe the fate of pyruvic acid.

Pyruvic acid produced during glycolysis depends on: - oxygen - for the next step in its metabolism LOW OXYGEN - In skeletal muscle fibers - during strenuous exercise 1) Pyruvic Acid Reduced - via anaerobic pathway - by addition of two hydrogen atoms 2) Lactic acid produced 3) This reaction regenerates: - NAD+ - to form glycerldehyde 3-phosphate - allows glycolysis to continue. 2 Pyruvic Acid (Oxidized) + 2 NADH + 2 H+ = 2 Lactic Acid (Reduced) + 2 NAD+ 4) Lactic acid is produced: - rapidly diffuses out of body cells - into blood 5) Hepatocytes remove: - lactic acid from blood - convert it back to pyruvic acid - lactic acid in blood causes muscle fatigue HIGH OXYGEN - Most cells convert pyruvic acid to acetyl coenzyme A 1) Acetyl coenzyme A: - links glycolysis - occurs in cytosol - to Krebs cycle - occurs in the matrix of mitochondria 2) Pyruvic acid: - enters mitochondrial matrix - with help of transporter protein 3) RBC lack mitochondria: - can only produce ATP via glycolysis

Key Molecules at Metabolic Crossroads: The Role of Acetyl Coenzyme A

ROLE OF ACETYL COENZYME A 8) When ATP is low but oxygen is plentiful: - most pyruvic acid travels towards ATP-producing reactions - such as the Krebs cycle and electron transport chain - by converting to acetyl coenzyme A. 9) Entry into the Krebs Cycle - Acetyl CoA is the vehicle that transports 2-carbon acetyl groups into the Krebs cycle Oxidative Krebs cycle reactions: - convert acetyl CoA into CO2 - produce reduced coenzymes (NADH and FADH2) - which transfer electrons to the electron transport chain Oxidative reactions in electron transport chain: - generate ATP Molecules that can be oxidized to produce ATP: - first converted to acetyl CoA - Glucose - fatty acids - ketone bodies 10) Synthesis of Lipids Can be used for synthesis of: - some lipids such as fatty acids - ketone bodies - cholesterol Carbohydrates can be turned into: - triglycerides - because pyruvic acid can be converted to - acetyl CoA - can store excess carbohydrates as fat Fatty acids CANNOT be used as: - glucose - or other carbohydrates - because acetyl CoA - cannot reconvert to pyruvic acid

Figure 25.6: After formation of acetyl coenzyme A, the next stage of cellular respiration is the Krebs cycle.

Reactions of the Krebs cycle occur in: - the matrix of mitochondria

What are some ways that glucose can by anabolized?

Synthesis of Glycogen Synthesis of new glucose molecules: - form some of the products of - protein and lipid breakdown.

Figure 25.7: The eight reactions of the Krebs cycle.

THREE MAIN RESULTS OF KREBS CYCLE 1) Production of reduced coenzymes (NADH and FADH2): - which contain stored energy in pyruvic acid from energy originally stored in glucose 2) Generation of GTP: - a high-energy compound - used to produce ATP 3) Formation of CO2 - which is transported to the lungs and exhaled. 8 STEPS INVOLVED 1) Entry of acetyl group - The chemical bond that attaches the acetyl group to coenzyme A (CoA) breaks 2-carbon acetyl group: - attaches to 4-carbon molecule of oxaloacetic acid - forms citric acid a 6-carbon molecule CoA is free to combine: - with another acetyl group - from pyruvic acid - to repeat the process. 2) Isomerization FORMS: - isocitric acid Citric acid undergoes isomerization: - to isocitric acid - has the same molecular formula as citrate Notice: - the hydroxyl group (-OH) is attached to a different carbon. 3) Oxidative Decarboxylation FORMS: - alpha-ketoglutaric acid - NADH + H+ Isocitric acid is: - oxidized - loses a molecule of CO2 - forming alpha-ketoglutaric acid The H+ from the oxidation: - is passed on to NAD+ NAD+ is reduced to: - NADH + H+. 4) Oxidative Decarboxylation FORMS - succinyl-CoA Alpha-ketoglutaric acid is oxidized: - loses a molecule of CO2 - picks up CoA - to form succinyl-CoA. 5) Substrate-level Phosphorylation FORMS - guanosin triphosphate - to form ATP CoA is displaced by a phosphate group: - which is then transferred to guanosine diphosphate (GDP) - to form guanosine triphosphate (GTP) GTP can donate: - a phosphate group to ADP - to form ATP. 6) Dehydrogenation FORMS - FAD - to be reduced to FADH2 Succinic acid is oxidized: - to fumaric acid - as two of its hydrogen atoms are transferred - to the coenzyme flavin adenine dinucleotide (FAD) FAD: - is reduced to FADH2. 7) Hydration FORMS - malic acid Fumaric acid is converted to: - malic acid - by the addition of a molecule of water. 8) Dehydrogenation FORMS - oxaloacetic acid - NAD+ reduced to NADH + H+ - Final step in the Krebs cycle - malic acid is oxidized - to re-form oxaloacetic acid Two hydrogen atoms: - are removed - one is transferred to NAD+ NAD+ is reduced to: - NADH + H+ Generated oxaloacetic acid: - can combine with another molecule of acetyl CoA - beginning a new cycle.

Side Note

Two NADH produced in the cytosol during glycolysis - cannot enter mitochondria Instead, they donate - their electrons -to one of the two transfer molecules Known as - a malate shuttle - and the glycerol phosphate shuttle. In cells of the: - liver - kidneys - heart - use of the malate shuttle results in - three ATPs synthesized for each NADH. In other body cells: - such as skeletal muscle fibers - neurons - use of the glycerol phosphate shuttle - results in two ATPs synthesized for each NADH.

Figure 25.1: Role of ATP in Linking anabolic and catabolic reactions.

The coupling of energy-releasing and energy-requiring reactions is achieved through ATP. 1) Simple molecules such as: - glucose - amino acids - glycerol - fatty acids 2) Anabolic reactions transfer energy from: - ATP - to complex molecules 3) Heat is Released 4) Complex molecules such as: - glycogen - proteins - triglycerides 5) Catabolic reactions - transfer energy from complex molecules - to ATP 6) Heat is Released 7) Cycle repeats

Figure 25.18: Principal metabolic pathways during the postabsorptive state.

The principal function of postabsorptive state reactions is: - to maintain a normal blood glucose level.

Figure 25.16: Summary of the roles of key molecules in metabolic pathways.

Three molecules: - glucose 6-phosphate - pyruvic acid - acetyl coenzyme A - stand at "metabolic crossroads." They can undergo different reactions depending on their nutritional or activity status. Reactions 1-7 occur in cytosol. Reactions 8/9: Occur inside mitochondria. Reaction 10: Occur in smooth muscle of endoplasmic reticulum.

What are the sources and significance of blood cholesterol?

Two Sources of Cholesterol in the Body: 1) Present in Foods: - Eggs - dairy - organ meats - beef - pork - processed luncheon meats 2) Most synthesized by Hepatocytes Fatty foods with low cholesterol: - can increase cholesterol in two ways: 1) High intake of dietary fats: - stimulates reabsorption of cholesterol-containing bile back into blood - less cholesterol lost in feces 2) Saturated fats: - broken down in the body - hepatocytes use some to make cholesterol. Lipid Profile Test: Measure: - total cholesterol (TC) - HDL-cholesterol - Trigylcerides (VLDLs). LDL cholesterol calculated LDL-cholesterol = TC - HDL-cholesterol - triglycerides/5. Desired blood cholesterol Levels: - Under 200 mg/dL - LDL-cholesterol under 130 mg/dL - HDL-cholesterol over 40 mg/dL - Normally triglycerides range 10-190 mg/dL. Coronary Artery Disease: - Total cholesterol above 200 mg/dL - heart attack doubles with every 50 mg/dL increase. High Blood Cholesterol: - Total Cholesterol above 239 mg/dL - LDL above 159 mg/dL. Reducing blood cholesterol: - Exercise, diet, drugs. Drugs: - Questran - Colestid - Liponicin - Zocor - Lipitor - Mevacor - HMG-CoA reductase.

How do RBC's produce ATP

Via glycolysis - lack mitochondria.

What are vitamins?

Vitamins: Organic nutrients - required in small amounts for growth and normal metabolism. Do not provide energy or serve as bodies building materials. Most vitamins are coenzymes. Provitamins: Raw materials that help body assemble some vitamins. Fat-soluble Vitamins: Vitamins A, E, D, K. Absorbed with dietary lipids in small intestine, packaged into chylomicrons. Cannot be absorbed adequately unless ingested with other lipids. Can be stored in cells - especially by hepatocytes. Water-soluble Vitamins: Several B vitamins and vitamin C - dissolved in body fluids. Excess quantities excreted in urine. Antioxidant Vitamins: Inactivate oxygen free radicals. Protect body against some cancers, reduce build-up of atherosclerotic plaque, delay effects of aging, decreasing chance of cataract formation of lens of eyes.

Describe Glucose Storage: Glycogenesis

When body does not need glucose for ATP production: - it is stored as Glycogen. Glycogen - Glucose combined with other molecules - type of Polysaccharide - only stored form of carbohydrate in the body Body stores about: - 500 g of glycogen - 75% in skeletal muscles - 25% in liver cells. Glycogenesis Triggered by: - the hormone insulin - secreted by pancreatic beta cells - stimulates hepatocytes and skeletal muscles to synthesize glycogen. 1) Glucose phosphorylated: - to glucose 6-phosphate - by hexokinase. 2) Glucose 6-phosphate: - is converted to glucose 1-phosphate 3) Then to uridine diphosphate glucose 4) And then to glycogen.

Describe Glucose Release: Glycogenolysis

When body needs ATP - the glycogen stored in the liver - is broken down into glucose - released into the blood - transported to cells - where it is catabolized by cellular respiration. Glycogenolysis - Process of splitting glycogen into glucose 1) Splitting glucose molecules: - off the branched glycogen molecule - via phosphorylation - to form glucose 1-phosphate 2) Phoshorylase (enzyme): - catalyzes the reaction - is activated by glucagon from pancreatic alpha cells - and epinephrine from adrenal medulla 3) Glucose 1-phosphate: - is converted to glucose 6-phosphate 4) Glucose 6-phosphate: - is converted to glucose - by the enzyme phosphotase (absent in skeletal muscle fibers) 5) Glucose leaves hepatocytes: - via glucose transporters (GluT) - in plasma membrane.