NutritionNutrition

Nutrient – a substance that promotes normal Nutrient – a substance that promotes normal growth, maintenance, and repairgrowth, maintenance, and repair

Major nutrients – carbohydrates, lipids, and Major nutrients – carbohydrates, lipids, and proteinsproteins

Other nutrients – vitamins and minerals (and Other nutrients – vitamins and minerals (and technically speaking, water)technically speaking, water)

USDA Food Guide PyramidUSDA Food Guide Pyramid

Figure 24.1a

NutritionNutrition

Figure 24.1b

CarbohydratesCarbohydrates

Complex carbohydrates (starches) are found in Complex carbohydrates (starches) are found in bread, cereal, flour, pasta, nuts, and potatoes bread, cereal, flour, pasta, nuts, and potatoes

Simple carbohydrates (sugars) are found in Simple carbohydrates (sugars) are found in soft drinks, candy, fruit, and ice creamsoft drinks, candy, fruit, and ice cream

CarbohydratesCarbohydrates

Glucose is the molecule ultimately used by Glucose is the molecule ultimately used by body cells to make ATPbody cells to make ATP

Neurons and RBCs rely almost entirely upon Neurons and RBCs rely almost entirely upon glucose to supply their energy needsglucose to supply their energy needs

Excess glucose is converted to glycogen or fat Excess glucose is converted to glycogen or fat and storedand stored

CarbohydratesCarbohydrates

The minimum amount of carbohydrates The minimum amount of carbohydrates needed to maintain adequate blood glucose needed to maintain adequate blood glucose levels is 100 grams per daylevels is 100 grams per day

Starchy foods and milk have nutrients such as Starchy foods and milk have nutrients such as vitamins and minerals in addition to complex vitamins and minerals in addition to complex carbohydratescarbohydrates

Refined carbohydrate foods (candy and soft Refined carbohydrate foods (candy and soft drinks) provide energy sources only and are drinks) provide energy sources only and are referred to as “empty calories”referred to as “empty calories”

LipidsLipids The most abundant dietary lipids, triglycerides, The most abundant dietary lipids, triglycerides,

are found in both animal and plant foodsare found in both animal and plant foods Essential fatty acids – linoleic and linolenic Essential fatty acids – linoleic and linolenic

acid, found in most vegetables, must be acid, found in most vegetables, must be ingestedingested

Dietary fats: Dietary fats: Help the body to absorb vitaminsHelp the body to absorb vitamins Are a major energy fuel of hepatocytes and skeletal Are a major energy fuel of hepatocytes and skeletal

musclemuscle Are a component of myelin sheaths and all cell Are a component of myelin sheaths and all cell

membranesmembranes

LipidsLipids

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

LipidsLipids

Prostaglandins function in:Prostaglandins function in: Smooth muscle contractionSmooth muscle contraction Control of blood pressureControl of blood pressure InflammationInflammation

Cholesterol stabilizes membranes and is a Cholesterol stabilizes membranes and is a precursor of bile salts and steroid hormonesprecursor of bile salts and steroid hormones

Lipids: Dietary RequirementsLipids: Dietary Requirements

Higher for infants and children than for adultsHigher 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 Fats should represent less than 30% of one’s total caloric intakecaloric intake

Saturated fats should be limited to 10% or less of Saturated fats should be limited to 10% or less of one’s total fat intakeone’s total fat intake

Daily cholesterol intake should not exceed 200 mgDaily cholesterol intake should not exceed 200 mg

ProteinsProteins

Complete proteins that meet all the body’s Complete proteins that meet all the body’s amino acid needs are found in eggs, milk, milk amino acid needs are found in eggs, milk, milk products, meat, and fishproducts, meat, and fish

Incomplete proteins are found in legumes, Incomplete proteins are found in legumes, nuts, seeds, grains, and vegetablesnuts, seeds, grains, and vegetables

ProteinsProteins

Proteins supply:Proteins supply: Essential amino acids, the building blocks for Essential amino acids, the building blocks for

nonessential amino acidsnonessential amino acids Nitrogen for nonprotein nitrogen-containing Nitrogen for nonprotein nitrogen-containing

substancessubstances Daily intake should be approximately 0.8g/kg Daily intake should be approximately 0.8g/kg

of body weightof body weight

Proteins: Synthesis and Proteins: Synthesis and HydrolysisHydrolysis

All-or-none ruleAll-or-none rule All amino acids needed must be present at the All amino acids needed must be present at the

same time for protein synthesis to occursame time for protein synthesis to occur Adequacy of caloric intakeAdequacy of caloric intake

Protein will be used as fuel if there is insufficient Protein will be used as fuel if there is insufficient carbohydrate or fat availablecarbohydrate or fat available

Proteins: Synthesis and Proteins: Synthesis and HydrolysisHydrolysis

Nitrogen balanceNitrogen balance The rate of protein synthesis equals the rate of The rate of protein synthesis equals the rate of

breakdown and lossbreakdown and loss Positive – synthesis exceeds breakdown (normal in Positive – synthesis exceeds breakdown (normal in

children and tissue repair)children and tissue repair) Negative – breakdown exceeds synthesis (e.g., Negative – breakdown exceeds synthesis (e.g.,

stress, burns, infection, or injury)stress, burns, infection, or injury) Hormonal controlHormonal control

Anabolic hormones accelerate protein synthesisAnabolic hormones accelerate protein synthesis

Essential Amino AcidsEssential Amino Acids

Figure 24.2

VitaminsVitamins

Organic compounds needed for growth and Organic compounds needed for growth and good healthgood health

They are crucial in helping the body use They are crucial in helping the body use nutrients and often function as coenzymesnutrients and often function as coenzymes

Only vitamins D, K, and B are synthesized in Only vitamins D, K, and B are synthesized in the body; all others must be ingestedthe body; all others must be ingested

Water-soluble vitamins (B-complex and C) are Water-soluble vitamins (B-complex and C) are absorbed in the gastrointestinal tract absorbed in the gastrointestinal tract BB1212 additionally requires gastric intrinsic factor to additionally requires gastric intrinsic factor to

be absorbedbe absorbed

VitaminsVitamins

Fat-soluble vitamins (A, D, E, and K) bind to Fat-soluble vitamins (A, D, E, and K) bind to ingested lipids and are absorbed with their ingested lipids and are absorbed with their digestion productsdigestion products

Vitamins A, C, and E also act in an antioxidant Vitamins A, C, and E also act in an antioxidant cascadecascade

MineralsMinerals

Seven minerals are required in moderate Seven minerals are required in moderate amounts amounts Calcium, phosphorus, potassium, sulfur, sodium, Calcium, phosphorus, potassium, sulfur, sodium,

chloride, and magnesiumchloride, and magnesium Dozens are required in trace amountsDozens are required in trace amounts Minerals work with nutrients to ensure proper Minerals work with nutrients to ensure proper

body functioningbody functioning Calcium, phosphorus, and magnesium salts Calcium, phosphorus, and magnesium salts

harden boneharden bone

MineralsMinerals

Sodium and chloride help maintain normal Sodium and chloride help maintain normal osmolarity, water balance, and are essential in osmolarity, water balance, and are essential in nerve and muscle functionnerve and muscle function

Uptake and excretion must be balanced to Uptake and excretion must be balanced to prevent toxic overloadprevent toxic overload

MetabolismMetabolism

Metabolism – all chemical reactions necessary Metabolism – all chemical reactions necessary to maintain lifeto maintain life

Cellular respiration – food fuels are broken Cellular respiration – food fuels are broken down within cells and some of the energy is down within cells and some of the energy is captured to produce ATPcaptured to produce ATP Anabolic reactions – synthesis of larger molecules Anabolic reactions – synthesis of larger molecules

from smaller onesfrom smaller ones Catabolic reactions – hydrolysis of complex Catabolic reactions – hydrolysis of complex

structures into simpler onesstructures into simpler ones

MetabolismMetabolism

Enzymes shift the high-energy phosphate Enzymes shift the high-energy phosphate groups of ATP to other moleculesgroups of ATP to other molecules

These phosphorylated molecules are activated These phosphorylated molecules are activated to perform cellular functionsto perform cellular functions

Stages of MetabolismStages of Metabolism

Energy-containing nutrients are processed in Energy-containing nutrients are processed in three major stagesthree major stages Digestion – breakdown of food; nutrients are Digestion – breakdown of food; nutrients are

transported to tissuestransported to tissues Anabolism and formation of catabolic Anabolism and formation of catabolic

intermediates where nutrients are:intermediates where nutrients are: Built into lipids, proteins, and glycogenBuilt into lipids, proteins, and glycogen Broken down by catabolic pathways to pyruvic acid and Broken down by catabolic pathways to pyruvic acid and

acetyl CoAacetyl CoA Oxidative breakdown – nutrients are catabolized to Oxidative breakdown – nutrients are catabolized to

carbon dioxide, water, and ATPcarbon dioxide, water, and ATP

Oxidation-Reduction (Redox) Oxidation-Reduction (Redox) ReactionsReactions

Oxidation occurs via the gain of oxygen or the loss Oxidation occurs via the gain of oxygen or the loss of hydrogenof hydrogen

Whenever one substance is oxidized, another Whenever one substance is oxidized, another substance is reducedsubstance is reduced

Oxidized substances lose energyOxidized substances lose energy Reduced substances gain energyReduced substances gain energy Coenzymes act as hydrogen (or electron) acceptorsCoenzymes act as hydrogen (or electron) acceptors Two important coenzymes are nicotinamide Two important coenzymes are nicotinamide

adenine dinucleotide (NADadenine dinucleotide (NAD++)) and flavin adenine and flavin adenine dinucleotide (FAD)dinucleotide (FAD)

Carbohydrate MetabolismCarbohydrate Metabolism Since all carbohydrates are transformed into Since all carbohydrates are transformed into

glucose, it is essentially glucose metabolismglucose, it is essentially glucose metabolism Oxidation of glucose is shown by the overall Oxidation of glucose is shown by the overall

reaction: reaction: CC66HH1212OO66 + 6O + 6O22 6H 6H22O + 6COO + 6CO22 + 36 ATP + + 36 ATP +

heatheat Glucose is catabolized in three pathwaysGlucose is catabolized in three pathways

GlycolysisGlycolysis Krebs cycleKrebs cycle The electron transport chain and oxidative The electron transport chain and oxidative

phosphorylationphosphorylation

GlycolysisGlycolysis

A three-phase pathway in which:A three-phase pathway in which: Glucose is oxidized into pyruvic acidGlucose is oxidized into pyruvic acid NADNAD++ is reduced to NADH + H is reduced to NADH + H++

ATP is synthesized by substrate-level ATP is synthesized by substrate-level phosphorylationphosphorylation

Pyruvic acid: Pyruvic acid: Moves on to the Krebs cycle in an aerobic pathway Moves on to the Krebs cycle in an aerobic pathway

oror Is reduced to lactic acid in an anaerobic Is reduced to lactic acid in an anaerobic

environmentenvironment

GlycolysisGlycolysis

Figure 24.6

2

2

Glucose

4 ADP2 NAD+

2 NAD+

2 Lactic acid

NADH+H+

NADH+H+

2 Pyruvic acid

Phase 1Sugaractivation

Fructose-1,6-bisphosphate

Dihydroxyacetonephosphate

Glyceraldehydephosphate

Phase 2Sugarcleavage

Phase 3Sugaroxidationand formationof ATP

Key:= Carbon atom= Inorganic phosphate

O2

GlycolysisElectron trans-port chain and oxidativephosphorylation

2 ADP

2 ATP

4 ATP

P

P P

P

Pi

Pi

To Krebscycle

(aerobicpathway)

ATP ATP ATP

Krebscycle

O2

Krebs Cycle: Preparatory StepKrebs Cycle: Preparatory Step

Occurs in the mitochondrial matrix and is Occurs in the mitochondrial matrix and is fueled by pyruvic acid and fatty acidsfueled by pyruvic acid and fatty acids

Krebs Cycle: Preparatory StepKrebs Cycle: Preparatory Step

Pyruvic acid is converted to acetyl CoA in Pyruvic acid is converted to acetyl CoA in three main steps:three main steps: DecarboxylationDecarboxylation

Carbon is removed from pyruvic acidCarbon is removed from pyruvic acid Carbon dioxide is releasedCarbon dioxide is released

Krebs Cycle: Preparatory StepKrebs Cycle: Preparatory Step

OxidationOxidation Hydrogen atoms are removed from pyruvic acidHydrogen atoms are removed from pyruvic acid NADNAD++ is reduced to NADH + H is reduced to NADH + H++

Formation of acetyl CoA – the resulting acetic acid Formation of acetyl CoA – the resulting acetic acid is combined with coenzyme A, a sulfur-containing is combined with coenzyme A, a sulfur-containing coenzyme, to form acetyl CoAcoenzyme, to form acetyl CoA

Krebs CycleKrebs Cycle

An eight-step cycle in which each acetic acid is An eight-step cycle in which each acetic acid is decarboxylated and oxidized, generating: decarboxylated and oxidized, generating: Three molecules of NADH + HThree molecules of NADH + H++

One molecule of FADHOne molecule of FADH22

Two molecules of COTwo molecules of CO22

One molecule of ATPOne molecule of ATP For each molecule of glucose entering For each molecule of glucose entering

glycolysis, two molecules of acetyl CoA enter glycolysis, two molecules of acetyl CoA enter the Krebs cyclethe Krebs cycle

Figure 24.7

NAD+

GDP +

CO2

NAD+

FAD

NADH+H+

Cytosol

Mitochondrion(fluid matrix)

FADH2

NADH+H+

Citric acid

(initial reactant)(pickup molecule)

Oxaloacetic acid

Malic acid

Fumaric acid

Succinic acidSuccinyl-CoA

GTP

ADP

Pi= Carbon atom

Key:

= Inorganic phosphate

= Coenzyme A

CoA

CoA

Acetyl CoA

Pyruvic acid from glycolysis

GlycolysisElectron

transport chain and oxidative

phosphorylation

Krebscycle

Pi

CoA

CoA

ATP

Krebs cycle

NAD+

CO2

CO2 NAD+

NADH+H+

NADH+H+

Isocitric acid

-Ketoglutaric acid

CoA

ATP ATP ATP

Electron Transport ChainElectron Transport Chain

Food (glucose) is oxidized and the released Food (glucose) is oxidized and the released hydrogens:hydrogens: Are transported by coenzymes NADH and FADHAre transported by coenzymes NADH and FADH22

Enter a chain of proteins bound to metal atoms Enter a chain of proteins bound to metal atoms (cofactors) (cofactors)

Combine with molecular oxygen to form waterCombine with molecular oxygen to form water Release energyRelease energy

The energy released is harnessed to attach The energy released is harnessed to attach inorganic phosphate groups (Pinorganic phosphate groups (P ii) to ADP, ) to ADP, making ATP by oxidative phosphorylationmaking ATP by oxidative phosphorylation

Figure 24.8

Electron Transport Chain ATP Synthase

Core

ADP +

Cyt c

Q

Intermembranespace

Inner mitochondrialmembrane

Mitochondrialmatrix

ATPPi

H+

2 H+ +

H+

H+

H+ H+

O2 H2O

GlycolysisElectron

transport chain and oxidative

phosphorylation

Krebscycle

e-

12

NADH + H+

NAD+

FAD

(carryingfrom food)

e-

FADH2

e-

ATP ATP ATP

32

1

Electronic Energy GradientElectronic Energy Gradient

The electrochemical proton gradient across the The electrochemical proton gradient across the inner membrane:inner membrane: Creates a pH gradient Creates a pH gradient Generates a voltage gradientGenerates a voltage gradient

These gradients cause HThese gradients cause H++ to flow back into the to flow back into the matrix via ATP synthasematrix via ATP synthase

ATP SynthaseATP Synthase

The enzyme consists of three parts: a rotor, a The enzyme consists of three parts: a rotor, a knob, and a rodknob, and a rod

Current created by HCurrent created by H++ causes the rotor and rod causes the rotor and rod to rotateto rotate

This rotation activates catalytic sites in the This rotation activates catalytic sites in the knob where ADP and Pknob where ADP and Pii are combined to make are combined to make

ATPATP

Structure of ATP SynthaseStructure of ATP Synthase

Figure 24.10

Summary of ATP ProductionSummary of ATP Production

Figure 24.11

Glycogenesis and GlycogenolysisGlycogenesis and Glycogenolysis

Glycogenesis – Glycogenesis – formation of glycogen formation of glycogen when glucose supplies when glucose supplies exceed cellular need exceed cellular need for ATP synthesisfor ATP synthesis

Glycogenolysis – Glycogenolysis – breakdown of breakdown of glycogen in response glycogen in response to low blood glucoseto low blood glucose

Figure 24.12

GluconeogenesisGluconeogenesis

The process of forming sugar from The process of forming sugar from noncarbohydrate moleculesnoncarbohydrate molecules

Takes place mainly in the liverTakes place mainly in the liver Protects the body, especially the brain, from Protects the body, especially the brain, from

the damaging effects of hypoglycemia by the damaging effects of hypoglycemia by ensuring ATP synthesis can continueensuring ATP synthesis can continue

Lipid MetabolismLipid Metabolism Most products of fat metabolism are transported Most products of fat metabolism are transported

in lymph as chylomicrons: a large plasma in lymph as chylomicrons: a large plasma lipoprotein particle, occurring as a droplet lipoprotein particle, occurring as a droplet consisting primarily of triglycerides and consisting primarily of triglycerides and functioning in the transport of neutral lipids from functioning in the transport of neutral lipids from the intestine to the tissues by way of the lymph. the intestine to the tissues by way of the lymph.

Lipids in chylomicrons are hydrolyzed by plasma Lipids in chylomicrons are hydrolyzed by plasma enzymes and absorbed by cellsenzymes and absorbed by cells

Only neutral fats are routinely oxidized for energyOnly neutral fats are routinely oxidized for energy

Lipid MetabolismLipid Metabolism

Catabolism of fats involves two separate Catabolism of fats involves two separate pathwayspathways Glycerol pathwayGlycerol pathway Fatty acids pathwayFatty acids pathway

Lipid Metabolism- Glycerol Lipid Metabolism- Glycerol PathwayPathway

Glycerol is converted to glyceraldehyde Glycerol is converted to glyceraldehyde phosphatephosphate Glyceraldehyde is ultimately converted into acetyl Glyceraldehyde is ultimately converted into acetyl

CoACoA Acetyl CoA enters the Krebs cycleAcetyl CoA enters the Krebs cycle

Lipid Metabolism- Fatty Acids Lipid Metabolism- Fatty Acids PathwayPathway

Fatty acids undergo beta oxidation which Fatty acids undergo beta oxidation which produces:produces: Two-carbon acetic acid fragments, which enter the Two-carbon acetic acid fragments, which enter the

Krebs cycleKrebs cycle Reduced coenzymes, which enter the electron Reduced coenzymes, which enter the electron

transport chaintransport chain

Lipid MetabolismLipid Metabolism

Figure 24.13

Lipogenesis and LipolysisLipogenesis and Lipolysis

Excess dietary glycerol and fatty acids Excess dietary glycerol and fatty acids undergo lipogenesis to form triglycerides undergo lipogenesis to form triglycerides

Glucose is easily converted into fat since Glucose is easily converted into fat since acetyl CoA is: acetyl CoA is: An intermediate in glucose catabolism An intermediate in glucose catabolism The starting molecule for the synthesis of fatty The starting molecule for the synthesis of fatty

acidsacids

Lipogenesis and LipolysisLipogenesis and Lipolysis

Lipolysis, the breakdown of stored fat, is Lipolysis, the breakdown of stored fat, is essentially lipogenesis in reverseessentially lipogenesis in reverse

Oxaloacetic acid is necessary for the complete Oxaloacetic acid is necessary for the complete oxidation of fatoxidation of fat Without it, acetyl CoA is converted into ketones Without it, acetyl CoA is converted into ketones

(ketogenesis)(ketogenesis)

Lipid Metabolism: Lipid Metabolism: Synthesis of Structural MaterialsSynthesis of Structural Materials

Phospholipids are important components of Phospholipids are important components of myelin and cell membranesmyelin and cell membranes

Lipid Metabolism: Lipid Metabolism: Synthesis of Structural MaterialsSynthesis of Structural Materials

The liver: The liver: Synthesizes lipoproteins for transport of Synthesizes lipoproteins for transport of

cholesterol and fatscholesterol and fats Makes tissue factor, a clotting factorMakes tissue factor, a clotting factor Synthesizes cholesterol for acetyl CoASynthesizes cholesterol for acetyl CoA Uses cholesterol to form bile saltsUses cholesterol to form bile salts

Certain endocrine organs use cholesterol to Certain endocrine organs use cholesterol to synthesize steroid hormonessynthesize steroid hormones

Protein MetabolismProtein Metabolism

Excess dietary protein results in amino acids Excess dietary protein results in amino acids being:being: Oxidized for energy Oxidized for energy Converted into fat for storageConverted into fat for storage

Amino acids must be deaminated prior to Amino acids must be deaminated prior to oxidation for energyoxidation for energy

Protein MetabolismProtein 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 One of the keto acid intermediates of the Krebs

cycle cycle These events occur as transamination, These events occur as transamination,

oxidative deamination, and keto acid oxidative deamination, and keto acid modificationmodification

Amino Acid OxidationAmino Acid Oxidation

Figure 24.15