Processing Food and Nutrition Chapter 46. Learning Objective 1 Describe food processing, including ingestion, digestion, absorption, and egestion or elimination

Processing Food and Processing Food and NutritionNutrition

Chapter 46Chapter 46

Learning Objective 1Learning Objective 1

• Describe food processing, including Describe food processing, including ingestioningestion, , digestiondigestion, , absorptionabsorption, and , and egestionegestion or or eliminationelimination

• Compare the digestive system of a Compare the digestive system of a cnidarian (such as cnidarian (such as HydraHydra) with that of an ) with that of an earthworm or vertebrateearthworm or vertebrate

NutritionNutrition

• The process of taking in and using foodThe process of taking in and using food

Food ProcessingFood Processing

• FeedingFeeding • selection, acquisition, and selection, acquisition, and ingestioningestion of food of food

• DigestionDigestion • breaking down food mechanically, chemically breaking down food mechanically, chemically

• Absorption Absorption • nutrients pass from digestive tract into bloodnutrients pass from digestive tract into blood

• EgestionEgestion (elimination)(elimination)• undigested, unabsorbed food discharged undigested, unabsorbed food discharged

Cnidarians and FlatwormsCnidarians and Flatworms

• Food digested in Food digested in gastrovascular cavitygastrovascular cavity • only one opening only one opening • serves as both mouth and anusserves as both mouth and anus

Gastrovascular Gastrovascular CavitiesCavities

Fig. 46-2a, p. 992

Wastes

Food

Tentacle

Mouth

Food Enzymes secreted by inner layer

Gastro- vascular cavity Food

absorbed

Gastrodermis(a) Hydra

(b) Exhalation.

Fig. 46-2b, p. 992

Gastrovascular cavityEpidermis

Food particles

Pharynx

Food absorbed

Mouth

EnzymesWastes

Lining of the intestine Food

(b) Flatworm

Complex Invertebrates and Complex Invertebrates and VertebratesVertebrates

• Digestive tract is complete tubeDigestive tract is complete tube• with opening at each end with opening at each end

• As food passes through tube As food passes through tube • digestion takes placedigestion takes place

• Parts of digestive tract are specializedParts of digestive tract are specialized• to perform specific functionsto perform specific functions

Complete Digestive TractComplete Digestive Tract

Fig. 46-3, p. 992

Crop Gizzard

EsophagusIntestine

Pharynx

Mouth Anus

Wastes

Food

Explore various digestive Explore various digestive systems by clicking on the figure systems by clicking on the figure

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KEY CONCEPTSKEY CONCEPTS

• Food processing includes ingestion, Food processing includes ingestion, digestion, absorption, and eliminationdigestion, absorption, and elimination

Adaptations for Obtaining FoodAdaptations for Obtaining Food


• Many animal adaptations are associated Many animal adaptations are associated with mode of nutritionwith mode of nutrition


• Trace the pathway traveled by an ingested Trace the pathway traveled by an ingested meal in the human digestive systemmeal in the human digestive system

• Describe the structure and function of Describe the structure and function of each organ involvedeach organ involved

Human Digestive System 1Human Digestive System 1

• Mouth Mouth • Mechanical, enzymatic digestion of carbohydratesMechanical, enzymatic digestion of carbohydrates

• Mammalian teethMammalian teeth• incisorsincisors for biting for biting • caninescanines for tearing food for tearing food • premolars,premolars, molarsmolars for crushing and grinding for crushing and grinding

Teeth and DietTeeth and Diet

Fig. 46-6a, p. 994

Incisors

CaninesPremolars Molars

(a) Carnivore.

Fig. 46-6b, p. 994

Incisors

Canine

Premolars

Molars

(b) Herbivore.

Fig. 46-6c, p. 994

Canines

Incisors

Premolars

Molars

(c) Omnivore.

Tooth StructureTooth Structure

Fig. 46-7, p. 995

Enamel GumCrown

Pulp cavity

PulpNeck Dentin

CementumRoot canal

RootSpongy bone

Nerve

Vein

(a) Human lower molar. Sagittal section showing the crown, neck, and root.

Artery (b) X-ray of a healthy tooth.


• Three pairs of Three pairs of salivary glandssalivary glands • secrete saliva (enzyme secrete saliva (enzyme salivary amylasesalivary amylase

digests starch)digests starch)

• PharynxPharynx and and esophagusesophagus• carry food to stomach carry food to stomach


• PeristalsisPeristalsis• waves of muscular contractionwaves of muscular contraction• pushes pushes bolusbolus of food along digestive tract of food along digestive tract

• StomachStomach • mechanical digestion by vigorous churningmechanical digestion by vigorous churning• enzyme enzyme pepsinpepsin in gastric juice digests in gastric juice digests

proteinsproteins

PeristalsisPeristalsis

Fig. 46-8, p. 995

EsophagusRelaxed muscle layer

Circular muscles contract, constricting passageway and pushing bolus ahead

Longitudinal muscles contract, shortening passageway ahead of the bolus

Relaxed muscle layer

Food bolus

Sphincter closed

Sphincter open

Stomach StomachA bolus is moved through the esophagus by peristaltic contractions.

When the sphincter (ring of muscle) at the entrance of the stomach opens, food enters the stomach.


• RugaeRugae • folds in stomach wallfolds in stomach wall• expand as stomach fills with food expand as stomach fills with food

• Gastric glandsGastric glands secrete secrete • hydrochloric acidhydrochloric acid • pepsinogen (pepsinogen (precursor of precursor of pepsin)pepsin)

Stomach StructureStomach Structure

Fig. 46-9a, p. 996

Visceral peritoneum

Esophagus

Sphincter

Circular muscle layer

Longitudinal muscle layer

Oblique muscle layer

Pyloric sphincter

Duodenum Rugae

Fig. 46-9b (1), p. 996

Openings into gastric glands

EpitheliumGastric glands

Lymph nodule

Gastric mucosa

Fig. 46-9b (2), p. 996

Chief cell Parietal cell

Nuclei

Surface epithelium

Chief cells

Parietal cellsGastric glands

Gastric glands


• ChymeChyme • soup of partly digested foodsoup of partly digested food• leaves stomach through leaves stomach through pyloruspylorus• enters enters small intestinesmall intestine in spurts in spurts

• DuodenumDuodenum • location of most enzymatic digestionlocation of most enzymatic digestion• produces several digestive enzymesproduces several digestive enzymes• receives secretions from liver and pancreasreceives secretions from liver and pancreas

Structure of Digestive TractStructure of Digestive Tract

Fig. 46-5, p. 993

VISCERAL PERITONEUM

Lymph nodule

Villi

Blood vessels

SUBMUCOSA

Nerve fibersMUCOSA

MUSCLE LAYER Inner circular fibers Outer longitudinal fibers


• LiverLiver produces produces bilebile• which emulsifies fats which emulsifies fats

• PancreasPancreas releases enzymes releases enzymes• digest protein, lipid, carbohydrate, RNA, DNA digest protein, lipid, carbohydrate, RNA, DNA

• TrypsinTrypsin and and chymotrypsinchymotrypsin • digest polypeptides to dipeptides digest polypeptides to dipeptides


• Pancreatic lipasePancreatic lipase • degrades fatsdegrades fats

• Pancreatic amylasePancreatic amylase • digests complex carbohydratesdigests complex carbohydrates

Liver and PancreasLiver and Pancreas

Fig. 46-11, p. 998

StomachInferior vena cava

Right lobe of liver

Right hepatic duct

PancreasCommon bile duct Hepatic

portal vein

Pancreatic duct

GallbladderDuodenum


• Large intestineLarge intestine• cecum, colon, rectum, anuscecum, colon, rectum, anus • eliminates undigested wastes eliminates undigested wastes • incubates bacteria (produce vitamin K, certain incubates bacteria (produce vitamin K, certain

B vitamins)B vitamins)

Human Digestive SystemHuman Digestive System

Fig. 46-4, p. 993

Parotid salivary gland

PharynxSublingual salivary gland

EsophagusSubmandibular salivary gland

Liver Stomach

DuodenumGallbladder

Pancreas

Ascending colon Transverse colon

Jejunumlleum Descending colon

CecumSigmoid colon

Vermiform appendix Anus

Rectum

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• Various parts of the vertebrate digestive Various parts of the vertebrate digestive system are specialized to perform specific system are specialized to perform specific functions; accessory glands (liver, functions; accessory glands (liver, pancreas, and salivary glands) secrete pancreas, and salivary glands) secrete fluids and enzymes important in digestionfluids and enzymes important in digestion


• Describe the step-by-step digestion of Describe the step-by-step digestion of carbohydratecarbohydrate, , proteinprotein, and , and lipidlipid

Carbohydrate DigestionCarbohydrate Digestion

• Polysaccharides Polysaccharides • digested to disaccharide digested to disaccharide maltosemaltose by by salivarysalivary

and and pancreatic amylasespancreatic amylases

• MaltaseMaltase in small intestine in small intestine• splits splits maltosemaltose into into glucoseglucose (main product of (main product of

carbohydrate digestion)carbohydrate digestion)

Protein DigestionProtein Digestion

• Proteins are split Proteins are split • by by pepsinpepsin in stomach in stomach• by proteolytic enzymes in pancreatic juiceby proteolytic enzymes in pancreatic juice

• DipeptidasesDipeptidases • split small peptides into split small peptides into amino acidsamino acids

Lipid DigestionLipid Digestion

• Lipids are emulsified by Lipids are emulsified by bile saltsbile salts • then hydrolyzed by then hydrolyzed by pancreatic lipasepancreatic lipase


• What structural adaptations increase the What structural adaptations increase the surface area of the digestive tract?surface area of the digestive tract?

Surface Area of the Small IntestineSurface Area of the Small Intestine

• Greatly expanded by Greatly expanded by • folds in wall (folds in wall (rugaerugae) ) • intestinal intestinal villivilli (projections of mucosa) (projections of mucosa)• microvillimicrovilli (plasma membrane projections of (plasma membrane projections of

epithelial cells of villi)epithelial cells of villi)

Villi and MicrovilliVilli and Microvilli

Fig. 46-10a, p. 997

Fig. 46-10b, p. 997

VilliEpithelial cells lining villus

Capillary network

Nerve fiber

Mucosa Openings of intestinal glands

Goblet cells

Intestinal glands

Submucosa Lacteal

Lymph vessel

Muscle layer

Visceral peritoneum

(b)

Fig. 46-10c, p. 997


• Compare lipid absorption with absorption Compare lipid absorption with absorption of other nutrientsof other nutrients

Nutrient AbsorptionNutrient Absorption

• Nutrients are absorbed through thin walls Nutrients are absorbed through thin walls of intestinal villi of intestinal villi

• Hepatic portal veinHepatic portal vein transports transports amino acidsamino acids and and glucoseglucose to liver to liver

Lipid Absorption 1Lipid Absorption 1

• Fatty acids and monoacylglycerolsFatty acids and monoacylglycerols• enter epithelial cells in intestinal liningenter epithelial cells in intestinal lining• are reassembled into triacylglycerols are reassembled into triacylglycerols • then packaged into then packaged into chylomicron chylomicron dropletsdroplets

Lipid Absorption 2Lipid Absorption 2

• ChylomicronsChylomicrons • also contain cholesterol and phospholipidsalso contain cholesterol and phospholipids• are covered by a protein coat are covered by a protein coat

• Lymphatic systemLymphatic system• transports chylomicrons to blood circulationtransports chylomicrons to blood circulation


• Summarize the nutritional requirements for Summarize the nutritional requirements for dietary carbohydrates, lipids, and proteinsdietary carbohydrates, lipids, and proteins

• Trace the fate of glucose, lipids, and Trace the fate of glucose, lipids, and amino acids after their absorptionamino acids after their absorption

A Balanced DietA Balanced Diet

• Humans and other animals requireHumans and other animals require• carbohydrates carbohydrates • lipidslipids• proteins proteins • vitaminsvitamins• minerals minerals

Carbohydrates 1Carbohydrates 1

• Most are ingested as polysaccharidesMost are ingested as polysaccharides• starch and cellulosestarch and cellulose

• Polysaccharides are Polysaccharides are complex carbohydratescomplex carbohydrates

• FiberFiber • mixture of cellulose, other indigestible mixture of cellulose, other indigestible

carbohydratescarbohydrates

Carbohydrates 2Carbohydrates 2

• CarbohydratesCarbohydrates• used mainly as energy source used mainly as energy source

• Glucose concentration in bloodGlucose concentration in blood• is carefully regulated is carefully regulated

• Excess glucoseExcess glucose• is stored as glycogenis stored as glycogen• or converted to fator converted to fat

Lipids 1Lipids 1

• Used to Used to • provide energy provide energy • form components of cell membranes form components of cell membranes • synthesize steroid hormones, other lipid synthesize steroid hormones, other lipid

substances substances

• Most lipids are ingested as triacylglycerols Most lipids are ingested as triacylglycerols

Lipids 2Lipids 2

• Fatty acids are converted to molecules of Fatty acids are converted to molecules of acetyl coenzyme A acetyl coenzyme A

• which enter citric acid cycle which enter citric acid cycle

• Excess fatty acids Excess fatty acids • are converted to triacylglycerolare converted to triacylglycerol• stored as fatstored as fat

Lipids 3Lipids 3

• Lipids are transported as large molecular Lipids are transported as large molecular complexes complexes (lipoproteins)(lipoproteins)

• Low-density lipoproteins (LDLs)Low-density lipoproteins (LDLs)• deliver cholesterol to cells deliver cholesterol to cells

• High-density lipoproteins (HDLs)High-density lipoproteins (HDLs)• collect excess cholesterolcollect excess cholesterol• transport it to livertransport it to liver

Fat Fat MetabolismMetabolism

Fig. 46-13, p. 1002

Fat cell Fat

Fatty acids +

Glycerol

Transported in blood

Liver Fatty acid + Glycerol

Enters cellular

respirationUsed to

make triacylglycerols

Acetyl CoA G3P

GlucoseConverted to other lipidsKetone bodies

Other cellsPyruvate or

acetyl CoA

Converted to other lipids

Enters cellular

respiration

Enters cellular

respiration

Fig. 46-13, p. 1002

Fat cell Fat

Fatty acids +

Glycerol

Transported in blood

+ Glycerol

Enters cellular respirationG3P

Glucose

Liver Fatty acid

Used to make

triacylglycerols

Acetyl CoA

Converted to other lipidsKetone bodies

Enters cellular respiration

Other cellsPyruvate or

acetyl CoA

Converted to other lipids

Enters cellular respiration

Stepped Art

Proteins 1Proteins 1

• Proteins serve as enzymesProteins serve as enzymes• and essential structural components of cells and essential structural components of cells

• Best distribution of Best distribution of essential amino acidsessential amino acids• in complete proteins of animal foods in complete proteins of animal foods

• Excess amino acidsExcess amino acids• are deaminated by liver cells are deaminated by liver cells

Proteins 2Proteins 2

• Amino groups are converted to ureaAmino groups are converted to urea• excreted in urineexcreted in urine

• Remaining keto acids are Remaining keto acids are • converted to carbohydrate and used as fuel converted to carbohydrate and used as fuel • converted to lipid and stored in fat cellsconverted to lipid and stored in fat cells

Protein Protein MetabolismMetabolism

Fig. 46-14, p. 1003

AMINO ACIDS

Catabolism Anabolism

Excess amino acids Structural proteins, hemoglobin, myosin, actin, enzymes, plasma proteins

Deamination

NH3 (ammonia) + -keto acids

FatUrea Pyruvate, -

ketoglutarate

Acetyl CoA

Ketone bodies

To kidneys Acetyl CoA

Fatty acids + glycerol

Triacylglycerol

Storage in fat cells

Liver

Enters cellular

respiration


• Describe the nutritional functions of Describe the nutritional functions of vitaminsvitamins, , mineralsminerals, and , and phytochemicalsphytochemicals

VitaminsVitamins

• Organic compounds required in small Organic compounds required in small amounts for biochemical processes amounts for biochemical processes

• components of coenzymes components of coenzymes

• Fat-soluble vitaminsFat-soluble vitamins• vitamins A, D, E, Kvitamins A, D, E, K

• Water-soluble vitaminsWater-soluble vitamins • B and C vitaminsB and C vitamins

MineralsMinerals

• Inorganic nutrients ingested as saltsInorganic nutrients ingested as salts• dissolved in food and water dissolved in food and water

• Trace elementsTrace elements • minerals required in small amounts minerals required in small amounts • (< 100 mg/day)(< 100 mg/day)

PhytochemicalsPhytochemicals

• Plant compounds that promote health Plant compounds that promote health • many are many are antioxidantsantioxidants that destroy that destroy oxidantsoxidants

• OxidantsOxidants • free radicals,free radicals, other reactive molecules other reactive molecules• damage DNA, proteins, unsaturated fatty damage DNA, proteins, unsaturated fatty

acids by snatching electronsacids by snatching electrons


• Most animals require the same basic Most animals require the same basic nutrients: carbohydrates, lipids, proteins, nutrients: carbohydrates, lipids, proteins, vitamins, and mineralsvitamins, and minerals


• Contrast Contrast basal metabolic ratebasal metabolic rate with with total total metabolic ratemetabolic rate

• Write the basic energy equation for Write the basic energy equation for maintaining body weight, and describe the maintaining body weight, and describe the consequences of altering it in either consequences of altering it in either directiondirection

Measuring MetabolismMeasuring Metabolism

• Basal metabolic rate (BMR)Basal metabolic rate (BMR) • body’s cost of metabolic livingbody’s cost of metabolic living

• Total metabolic rateTotal metabolic rate • BMR plus energy used to carry on daily BMR plus energy used to carry on daily

activitiesactivities

EnergyEnergy

• If energy (kcal) input equals energy output If energy (kcal) input equals energy output • body weight remains constant body weight remains constant

• If energy output exceeds energy input If energy output exceeds energy input • body weight decreases body weight decreases

• If energy input exceeds energy outputIf energy input exceeds energy output• body weight increasesbody weight increases


• In general terms, describe the effects of In general terms, describe the effects of malnutritionmalnutrition, including both , including both undernutritionundernutrition and and overnutritionovernutrition

UndernutritionUndernutrition

• Form of malnutrition Form of malnutrition • causes fatigue causes fatigue • depresses immune function depresses immune function

• Essential amino acidsEssential amino acids• nutrients most often deficient in dietnutrients most often deficient in diet

Protein DeficiencyProtein Deficiency

OvernutritionOvernutrition

• ObesityObesity • serious form of malnutrition serious form of malnutrition • excess fat accumulates in adipose tissuesexcess fat accumulates in adipose tissues• factor in heart disease, diabetes mellitus, factor in heart disease, diabetes mellitus,

other disorders other disorders

• Person gains weight taking in more energy Person gains weight taking in more energy (kilocalories) than expended in activity(kilocalories) than expended in activity


• Basal metabolic rate is the body’s cost of Basal metabolic rate is the body’s cost of metabolic living metabolic living

• When energy (kilocalories) input equals When energy (kilocalories) input equals energy output, body weight remains energy output, body weight remains constantconstant


• Summarize current hypotheses about the Summarize current hypotheses about the regulation of food intake and energy regulation of food intake and energy homeostasis, including the roles of homeostasis, including the roles of leptinleptin and and neuropeptide Yneuropeptide Y

LeptinLeptin

• Hormone produced by fat cellsHormone produced by fat cells• in proportion to body fat in proportion to body fat

• Signals brain about status of energy stores Signals brain about status of energy stores

Effect of LeptinEffect of Leptin

Neuropeptide Y (NPY)Neuropeptide Y (NPY)

• Neurotransmitter produced in hypothalamusNeurotransmitter produced in hypothalamus• increases appetite increases appetite

• Slows metabolism when leptin levels and Slows metabolism when leptin levels and food intake are lowfood intake are low

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Processing Food and Nutrition Chapter 46. Learning Objective 1 Describe food processing, including ingestion, digestion, absorption, and egestion or elimination