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Nutrition and Digestion
Pg. 428-429 Suspension-feeding: a baleen whale
Ingesting food
Omnivores - ingest plants and animals
Herbivores -plant eaters
Carnivores -animal eaters
Suspension feeders-eat particles in the water
• Substrate feeder - live in or on food source
• Fluid feeder- suck nutrient rich fluid from
• Bulk feeder- eat large pieces of food
Figure 21.1 Substrate-feeding: a leaf miner
Figure 2118 Fluid-feeding: a mosquito
21.1E Bulk-feeding: a python
Food processing: 4 stages
• 1 Eating
• 2 Breakdown of food into small molecules for absorption
• 3 Cells in the lining of the digestive tract absorb nutrient
• 4 Undigested materials pass out of the digestive tract
Food processing: 4 stages
• Ingestion -eating
• Digestion-breakdown of food into small
molecules for absorption
• Absorption - cells in the lining of the
digestive tract absorb nutrient molecules
• Elimination - undigested materials pass out
of the digestive tract
Digestion occurs in specialized
Simple animals
have a mouth and
cavity Fig 21.3A
More complex animals have an
alimentary canal
Human digestive tract
• Alimentary canal
Main parts
– Mouth,oral
all intestine, large
intestine, rectum, anus
• Accessory structures
– Salivary glands,
pancreas, liver
– Peristalsis, sphincters
The oral cavity
• Salivary juices
– Lubricate, buffer, kill
bacteria, begin
• Mechanical and
Chemical digestion
– Tooth types
• Tongue
– Manipulates food
Food and breathing passages
open to the pharynx
• Pharynx open to windpipe most of the time
• During eating the epiglottis closes off the
Esophagus squeezes food
to the stomach
• Two muscle layers, circular and longitudinal
• Peristalsis moves the food along
• No digestive function (hiatal hernia)
Stomach stores food and breaks it down
2-6 hours!
• Involves acid and digestive enzymes
• Can store 2L of food
• Has pits, glands, and cells which produce acid and mucus
Stomach stores food and breaks it down
• Digestion in the stomach
– Pepsinogen + HCl Epepsin acitvated
– Proteins + pepsin E polypeptides
Gastric glands secrete mucus, HCl and pepsinogen
External stimuli (smell, sight) stimulate gastrin release
Gastrin stimulates production of gastric juce
Chyme forms from food and gastric juice mixed together
Disorders of the stomach and esophagus
• Acid reflux- back flow of acid into the esophagus
- heartburn
• Barrett’s esophagus - growth of abnormal tissue in
the esophagus.
• Gastric ulcers-digestive juice erodes the lining of
the stomach wall creating open sores
• H. pylori can cause ulcers also (gastritis)
• Antibiotics can cure this
Small intestine: major site of chemical
digestion and nutrient absorption
Small intestine: major site of chemical
digestion and nutrient absorption
• Pancreas -secretes 9 different enzymes that
break down fat, protein, carbohydrate. Also
produces an alkaline secretion that
neutralizes acid chyme
• Liver-produces bile that emulsifies fat
• Bile- chemically emulsifies fat
• Gallbladder- stores bile salts that emulsify
• Duodenum- site of absorption
Small intestine:Structure
• Starch
• Place a sample of
solution to be tested in
the dish
• Add a few drops of
• Maltose
• Add benedicts to
solution remaining in
each test tube
• Heat and observe
Test for Starch with IKI
• A dark brown color indicates the
presence of starch
Hydrolysis of Starch to Maltose
Total hydrolysis No hydrolysis
Partial hydrolysis
Test for Maltose with Benedicts
• Blue is negative
• Orange is positive
Large intestine
• Cecum - blind pouch that stores bacteria
• Appendix - immune function
• Main function - water absorption - creates feces which become
harder as water is absorbed
• Vitamin production from E. coli
• Rectum-terminal portion of the colon
• Diarrhea / constipation
Adaptations of the digestive system
• Carnivore - short
alimentary canal
• Herbivore/omnivorelong alimentary canal
– Special chambers to
digest cellulose
• Cow - the extreme
herbivore - Ruminant
4 chambered stomach
extracts maximum
1+2 prokaryotes digest cellulose in rumen and reticulum
Regurgitation and more chewing
Swallow again - omasum absorbs water
Abomasum - cow’s own enzymes complete digestion
• “If you find honey eat just
enough - too much and
you will vomit”
• Macronutrients
– Carbohydrates, Fats, Proteins, Nucleic acids
– Provide fuel for energy
• Micronutrients
– Vitamins and minerals
BMR = 1300-1800
kcal per day
Liver makes and
stores glycogen
which is stored in
muscles as well
Excess energy is
stored as fat
Essential Amino Acids
• Your body
makes many
amino acids, but
not all of them
• Some AA’s must
be obtained from
food = essential
• Chemical nutrients
other than O, H, N, H
• All minerals are
• Too much of some can
cause high blood
• An organic nutrient
that is essential but
required in smaller
• Coenzymes - part of
the metabolic
reactions in the body
• Deficiencies cause
specific sets of