Nutrition Nutrient – a substance that promotes normal growth, maintenance, and repair Nutrient – a substance that promotes normal growth, maintenance, and repair Major nutrients – carbohydrates, lipids, and proteins Major nutrients – carbohydrates, lipids, and proteins Other nutrients – vitamins and minerals (and technically speaking, water) Other nutrients – vitamins and minerals (and technically speaking, water)

USDA Food Guide Pyramid Figure 24.1a

Nutrition Figure 24.1b

Carbohydrates Complex carbohydrates (starches) are found in bread, cereal, flour, pasta, nuts, and potatoes Complex carbohydrates (starches) are found in bread, cereal, flour, pasta, nuts, and potatoes Simple carbohydrates (sugars) are found in soft drinks, candy, fruit, and ice cream Simple carbohydrates (sugars) are found in soft drinks, candy, fruit, and ice cream

Carbohydrates Glucose is the molecule ultimately used by body cells to make ATP Glucose is the molecule ultimately used by body cells to make ATP Neurons and RBCs rely almost entirely upon glucose to supply their energy needs Neurons and RBCs rely almost entirely upon glucose to supply their energy needs Excess glucose is converted to glycogen or fat and stored Excess glucose is converted to glycogen or fat and stored

Carbohydrates The minimum amount of carbohydrates needed to maintain adequate blood glucose levels is 100 grams per day The minimum amount of carbohydrates needed to maintain adequate blood glucose levels is 100 grams per day Starchy foods and milk have nutrients such as vitamins and minerals in addition to complex carbohydrates Starchy foods and milk have nutrients such as vitamins and minerals in addition to complex carbohydrates Refined carbohydrate foods (candy and soft drinks) provide energy sources only and are referred to as “empty calories” Refined carbohydrate foods (candy and soft drinks) provide energy sources only and are referred to as “empty calories”

Lipids The most abundant dietary lipids, triglycerides, are found in both animal and plant foods The most abundant dietary lipids, triglycerides, are found in both animal and plant foods Essential fatty acids – linoleic and linolenic acid, found in most vegetables, must be ingested Essential fatty acids – linoleic and linolenic acid, found in most vegetables, must be ingested Dietary fats: Dietary fats: Help the body to absorb vitamins Help the body to absorb vitamins Are a major energy fuel of hepatocytes and skeletal muscle Are a major energy fuel of hepatocytes and skeletal muscle Are a component of myelin sheaths and all cell membranes Are a component of myelin sheaths and all cell membranes

Lipids Fatty deposits in adipose tissue provide: Fatty deposits in adipose tissue provide: A protective cushion around body organs A protective cushion around body organs An insulating layer beneath the skin An insulating layer beneath the skin An easy-to-store concentrated source of energy An easy-to-store concentrated source of energy

Lipids Prostaglandins function in: Prostaglandins function in: Smooth muscle contraction Smooth muscle contraction Control of blood pressure Control of blood pressure Inflammation Inflammation Cholesterol stabilizes membranes and is a precursor of bile salts and steroid hormones Cholesterol stabilizes membranes and is a precursor of bile salts and steroid hormones

Lipids: Dietary Requirements Higher for infants and children than for adults Higher for infants and children than for adults The American Heart Association suggests that: The American Heart Association suggests that: Fats should represent less than 30% of one’s total caloric intake Fats should represent less than 30% of one’s total caloric intake Saturated fats should be limited to 10% or less of one’s total fat intake Saturated fats should be limited to 10% or less of one’s total fat intake Daily cholesterol intake should not exceed 200 mg Daily cholesterol intake should not exceed 200 mg

Proteins Complete proteins that meet all the body’s amino acid needs are found in eggs, milk, milk products, meat, and fish Complete proteins that meet all the body’s amino acid needs are found in eggs, milk, milk products, meat, and fish Incomplete proteins are found in legumes, nuts, seeds, grains, and vegetables Incomplete proteins are found in legumes, nuts, seeds, grains, and vegetables

Proteins Proteins supply: Proteins supply: Essential amino acids, the building blocks for nonessential amino acids Essential amino acids, the building blocks for nonessential amino acids Nitrogen for nonprotein nitrogen-containing substances Nitrogen for nonprotein nitrogen-containing substances Daily intake should be approximately 0.8g/kg of body weight Daily intake should be approximately 0.8g/kg of body weight

Proteins: Synthesis and Hydrolysis All-or-none rule All-or-none rule All amino acids needed must be present at the same time for protein synthesis to occur All amino acids needed must be present at the same time for protein synthesis to occur Adequacy of caloric intake Adequacy of caloric intake Protein will be used as fuel if there is insufficient carbohydrate or fat available Protein will be used as fuel if there is insufficient carbohydrate or fat available

Proteins: Synthesis and Hydrolysis Nitrogen balance Nitrogen balance The rate of protein synthesis equals the rate of breakdown and loss The rate of protein synthesis equals the rate of breakdown and loss Positive – synthesis exceeds breakdown (normal in children and tissue repair) Positive – synthesis exceeds breakdown (normal in children and tissue repair) Negative – breakdown exceeds synthesis (e.g., stress, burns, infection, or injury) Negative – breakdown exceeds synthesis (e.g., stress, burns, infection, or injury) Hormonal control Hormonal control Anabolic hormones accelerate protein synthesis Anabolic hormones accelerate protein synthesis

Essential Amino Acids Figure 24.2

Vitamins Organic compounds needed for growth and good health Organic compounds needed for growth and good health They are crucial in helping the body use nutrients and often function as coenzymes They are crucial in helping the body use nutrients and often function as coenzymes Only vitamins D, K, and B are synthesized in the body; all others must be ingested Only vitamins D, K, and B are synthesized in the body; all others must be ingested Water-soluble vitamins (B-complex and C) are absorbed in the gastrointestinal tract Water-soluble vitamins (B-complex and C) are absorbed in the gastrointestinal tract B 12 additionally requires gastric intrinsic factor to be absorbed B 12 additionally requires gastric intrinsic factor to be absorbed

Vitamins Fat-soluble vitamins (A, D, E, and K) bind to ingested lipids and are absorbed with their digestion products Fat-soluble vitamins (A, D, E, and K) bind to ingested lipids and are absorbed with their digestion products Vitamins A, C, and E also act in an antioxidant cascade Vitamins A, C, and E also act in an antioxidant cascade

Minerals Seven minerals are required in moderate amounts Seven minerals are required in moderate amounts Calcium, phosphorus, potassium, sulfur, sodium, chloride, and magnesium Calcium, phosphorus, potassium, sulfur, sodium, chloride, and magnesium Dozens are required in trace amounts Dozens are required in trace amounts Minerals work with nutrients to ensure proper body functioning Minerals work with nutrients to ensure proper body functioning Calcium, phosphorus, and magnesium salts harden bone Calcium, phosphorus, and magnesium salts harden bone

Minerals Sodium and chloride help maintain normal osmolarity, water balance, and are essential in nerve and muscle function Sodium and chloride help maintain normal osmolarity, water balance, and are essential in nerve and muscle function Uptake and excretion must be balanced to prevent toxic overload Uptake and excretion must be balanced to prevent toxic overload

Metabolism Metabolism – all chemical reactions necessary to maintain life Metabolism – all chemical reactions necessary to maintain life Cellular respiration – food fuels are broken down within cells and some of the energy is captured to produce ATP Cellular respiration – food fuels are broken down within cells and some of the energy is captured to produce ATP Anabolic reactions – synthesis of larger molecules from smaller ones Anabolic reactions – synthesis of larger molecules from smaller ones Catabolic reactions – hydrolysis of complex structures into simpler ones Catabolic reactions – hydrolysis of complex structures into simpler ones

Metabolism Enzymes shift the high-energy phosphate groups of ATP to other molecules Enzymes shift the high-energy phosphate groups of ATP to other molecules These phosphorylated molecules are activated to perform cellular functions These phosphorylated molecules are activated to perform cellular functions

Stages of Metabolism Energy-containing nutrients are processed in three major stages Energy-containing nutrients are processed in three major stages Digestion – breakdown of food; nutrients are transported to tissues Digestion – breakdown of food; nutrients are transported to tissues Anabolism and formation of catabolic intermediates where nutrients are: Anabolism and formation of catabolic intermediates where nutrients are: Built into lipids, proteins, and glycogen Built into lipids, proteins, and glycogen Broken down by catabolic pathways to pyruvic acid and acetyl CoA Broken down by catabolic pathways to pyruvic acid and acetyl CoA Oxidative breakdown – nutrients are catabolized to carbon dioxide, water, and ATP Oxidative breakdown – nutrients are catabolized to carbon dioxide, water, and ATP

Oxidation-Reduction (Redox) Reactions Oxidation occurs via the gain of oxygen or the loss of hydrogen Oxidation occurs via the gain of oxygen or the loss of hydrogen Whenever one substance is oxidized, another substance is reduced Whenever one substance is oxidized, another substance is reduced Oxidized substances lose energy Oxidized substances lose energy Reduced substances gain energy Reduced substances gain energy Coenzymes act as hydrogen (or electron) acceptors Coenzymes act as hydrogen (or electron) acceptors Two important coenzymes are nicotinamide adenine dinucleotide (NAD + ) and flavin adenine dinucleotide (FAD) Two important coenzymes are nicotinamide adenine dinucleotide (NAD + ) and flavin adenine dinucleotide (FAD)

Carbohydrate Metabolism Since all carbohydrates are transformed into glucose, it is essentially glucose metabolism Since all carbohydrates are transformed into glucose, it is essentially glucose metabolism Oxidation of glucose is shown by the overall reaction: Oxidation of glucose is shown by the overall reaction: C 6 H 12 O 6 + 6O 2  6H 2 O + 6CO ATP + heat C 6 H 12 O 6 + 6O 2  6H 2 O + 6CO ATP + heat Glucose is catabolized in three pathways Glucose is catabolized in three pathways Glycolysis Glycolysis Krebs cycle Krebs cycle The electron transport chain and oxidative phosphorylation The electron transport chain and oxidative phosphorylation

Glycolysis A three-phase pathway in which: A three-phase pathway in which: Glucose is oxidized into pyruvic acid Glucose is oxidized into pyruvic acid NAD + is reduced to NADH + H + NAD + is reduced to NADH + H + ATP is synthesized by substrate-level phosphorylation ATP is synthesized by substrate-level phosphorylation Pyruvic acid: Pyruvic acid: Moves on to the Krebs cycle in an aerobic pathway or Moves on to the Krebs cycle in an aerobic pathway or Is reduced to lactic acid in an anaerobic environment Is reduced to lactic acid in an anaerobic environment

Glycolysis Figure Glucose 4 ADP 2 NAD + 2 Lactic acid NADH+H + 2 Pyruvic acid Phase 1 Sugar activation Fructose-1,6- bisphosphate Dihydroxyacetone phosphate Glyceraldehyde phosphate Phase 2 Sugar cleavage Phase 3 Sugar oxidation and formation of ATP Key: = Carbon atom = Inorganic phosphate O2O2 Glycolysis Electron trans- port chain and oxidative phosphorylation 2 ADP 2 ATP 4 ATP P PP P PiPi PiPi To Krebs cycle (aerobic pathway) ATP Krebs cycle O2O2

Krebs Cycle: Preparatory Step Occurs in the mitochondrial matrix and is fueled by pyruvic acid and fatty acids Occurs in the mitochondrial matrix and is fueled by pyruvic acid and fatty acids

Krebs Cycle: Preparatory Step Pyruvic acid is converted to acetyl CoA in three main steps: Pyruvic acid is converted to acetyl CoA in three main steps: Decarboxylation Decarboxylation Carbon is removed from pyruvic acid Carbon is removed from pyruvic acid Carbon dioxide is released Carbon dioxide is released

Krebs Cycle: Preparatory Step Oxidation Oxidation Hydrogen atoms are removed from pyruvic acid Hydrogen atoms are removed from pyruvic acid NAD + is reduced to NADH + H + NAD + is reduced to NADH + H + Formation of acetyl CoA – the resulting acetic acid is combined with coenzyme A, a sulfur-containing coenzyme, to form acetyl CoA Formation of acetyl CoA – the resulting acetic acid is combined with coenzyme A, a sulfur-containing coenzyme, to form acetyl CoA

Krebs Cycle An eight-step cycle in which each acetic acid is decarboxylated and oxidized, generating: An eight-step cycle in which each acetic acid is decarboxylated and oxidized, generating: Three molecules of NADH + H + Three molecules of NADH + H + One molecule of FADH 2 One molecule of FADH 2 Two molecules of CO 2 Two molecules of CO 2 One molecule of ATP One molecule of ATP For each molecule of glucose entering glycolysis, two molecules of acetyl CoA enter the Krebs cycle For each molecule of glucose entering glycolysis, two molecules of acetyl CoA enter the Krebs cycle

Figure 24.7 NAD + GDP + CO 2 NAD + FAD NADH+H + Cytosol Mitochondrion (fluid matrix) FADH 2 NADH+H + Citric acid (initial reactant) (pickup molecule) Oxaloacetic acid Malic acid Fumaric acid Succinic acid Succinyl-CoA GTP ADP PiPi = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA ATP Krebs cycle NAD + CO 2 NAD + NADH+H + Isocitric acid  -Ketoglutaric acid CoA ATP

Electron Transport Chain Food (glucose) is oxidized and the released hydrogens: Food (glucose) is oxidized and the released hydrogens: Are transported by coenzymes NADH and FADH 2 Are transported by coenzymes NADH and FADH 2 Enter a chain of proteins bound to metal atoms (cofactors) Enter a chain of proteins bound to metal atoms (cofactors) Combine with molecular oxygen to form water Combine with molecular oxygen to form water Release energy Release energy The energy released is harnessed to attach inorganic phosphate groups (P i ) to ADP, making ATP by oxidative phosphorylation The energy released is harnessed to attach inorganic phosphate groups (P i ) to ADP, making ATP by oxidative phosphorylation

Figure 24.8 Electron Transport ChainATP Synthase Core ADP + Cyt c Q Intermembrane space Inner mitochondrial membrane Mitochondrial matrix ATP PiPi H+H+ 2H+H+ + H+H+ H+H+ H+H+ H+H+ O2O2 H2OH2O Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle e NADH + H + NAD + FAD (carrying from food) e- FADH 2 e- ATP 3 2 1

Electronic Energy Gradient The electrochemical proton gradient across the inner membrane: The electrochemical proton gradient across the inner membrane: Creates a pH gradient Creates a pH gradient Generates a voltage gradient Generates a voltage gradient These gradients cause H + to flow back into the matrix via ATP synthase These gradients cause H + to flow back into the matrix via ATP synthase

ATP Synthase The enzyme consists of three parts: a rotor, a knob, and a rod The enzyme consists of three parts: a rotor, a knob, and a rod Current created by H + causes the rotor and rod to rotate Current created by H + causes the rotor and rod to rotate This rotation activates catalytic sites in the knob where ADP and P i are combined to make ATP This rotation activates catalytic sites in the knob where ADP and P i are combined to make ATP

Structure of ATP Synthase Figure 24.10

Summary of ATP Production Figure 24.11

Glycogenesis and Glycogenolysis Glycogenesis – formation of glycogen when glucose supplies exceed cellular need for ATP synthesis Glycogenesis – formation of glycogen when glucose supplies exceed cellular need for ATP synthesis Glycogenolysis – breakdown of glycogen in response to low blood glucose Glycogenolysis – breakdown of glycogen in response to low blood glucose Figure 24.12

Gluconeogenesis The process of forming sugar from noncarbohydrate molecules The process of forming sugar from noncarbohydrate molecules Takes place mainly in the liver Takes place mainly in the liver Protects the body, especially the brain, from the damaging effects of hypoglycemia by ensuring ATP synthesis can continue Protects the body, especially the brain, from the damaging effects of hypoglycemia by ensuring ATP synthesis can continue

Lipid Metabolism Most products of fat metabolism are transported in lymph as chylomicrons: a large plasma lipoprotein particle, occurring as a droplet consisting primarily of triglycerides and functioning in the transport of neutral lipids from the intestine to the tissues by way of the lymph. Most products of fat metabolism are transported in lymph as chylomicrons: a large plasma lipoprotein particle, occurring as a droplet consisting primarily of triglycerides and functioning in the transport of neutral lipids from the intestine to the tissues by way of the lymph. Lipids in chylomicrons are hydrolyzed by plasma enzymes and absorbed by cells Lipids in chylomicrons are hydrolyzed by plasma enzymes and absorbed by cells Only neutral fats are routinely oxidized for energy Only neutral fats are routinely oxidized for energy

Lipid Metabolism Catabolism of fats involves two separate pathways Catabolism of fats involves two separate pathways Glycerol pathway Glycerol pathway Fatty acids pathway Fatty acids pathway

Lipid Metabolism- Glycerol Pathway Glycerol is converted to glyceraldehyde phosphate Glycerol is converted to glyceraldehyde phosphate Glyceraldehyde is ultimately converted into acetyl CoA Glyceraldehyde is ultimately converted into acetyl CoA Acetyl CoA enters the Krebs cycle Acetyl CoA enters the Krebs cycle

Lipid Metabolism- Fatty Acids Pathway Fatty acids undergo beta oxidation which produces: Fatty acids undergo beta oxidation which produces: Two-carbon acetic acid fragments, which enter the Krebs cycle Two-carbon acetic acid fragments, which enter the Krebs cycle Reduced coenzymes, which enter the electron transport chain Reduced coenzymes, which enter the electron transport chain

Lipid Metabolism Figure 24.13

Lipogenesis and Lipolysis Excess dietary glycerol and fatty acids undergo lipogenesis to form triglycerides Excess dietary glycerol and fatty acids undergo lipogenesis to form triglycerides Glucose is easily converted into fat since acetyl CoA is: Glucose is easily converted into fat since acetyl CoA is: An intermediate in glucose catabolism An intermediate in glucose catabolism The starting molecule for the synthesis of fatty acids The starting molecule for the synthesis of fatty acids

Lipogenesis and Lipolysis Lipolysis, the breakdown of stored fat, is essentially lipogenesis in reverse Lipolysis, the breakdown of stored fat, is essentially lipogenesis in reverse Oxaloacetic acid is necessary for the complete oxidation of fat Oxaloacetic acid is necessary for the complete oxidation of fat Without it, acetyl CoA is converted into ketones (ketogenesis) Without it, acetyl CoA is converted into ketones (ketogenesis)

Lipid Metabolism: Synthesis of Structural Materials Phospholipids are important components of myelin and cell membranes Phospholipids are important components of myelin and cell membranes

Lipid Metabolism: Synthesis of Structural Materials The liver: The liver: Synthesizes lipoproteins for transport of cholesterol and fats Synthesizes lipoproteins for transport of cholesterol and fats Makes tissue factor, a clotting factor Makes tissue factor, a clotting factor Synthesizes cholesterol for acetyl CoA Synthesizes cholesterol for acetyl CoA Uses cholesterol to form bile salts Uses cholesterol to form bile salts Certain endocrine organs use cholesterol to synthesize steroid hormones Certain endocrine organs use cholesterol to synthesize steroid hormones

Protein Metabolism Excess dietary protein results in amino acids being: Excess dietary protein results in amino acids being: Oxidized for energy Oxidized for energy Converted into fat for storage Converted into fat for storage Amino acids must be deaminated prior to oxidation for energy Amino acids must be deaminated prior to oxidation for energy

Protein Metabolism Deaminated amino acids are converted into: Deaminated amino acids are converted into: Pyruvic acid Pyruvic acid One of the keto acid intermediates of the Krebs cycle One of the keto acid intermediates of the Krebs cycle These events occur as transamination, oxidative deamination, and keto acid modification These events occur as transamination, oxidative deamination, and keto acid modification

Amino Acid Oxidation Figure 24.15