Transcript Nutrition and Digestion

Nutrition and Digestion
Vitamin A and Learning
In The News
Nutrients
• Raw materials
– Growth
– Repair
– Maintenance
– Reproduction
• Energy
Classes of Nutrients
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Carbohydrates
Lipids
Proteins
Minerals
Vitamins
Water
Macronutrients
• Carbon-containing compounds
• Energy and raw material
• Includes carbohydrates, lipids, & proteins
• Body needs substantial amounts
Carbohydrates
• Should supply 45-65% of daily energy
• Includes fruits, vegetables, whole grains
• more low glycemic than high glycemic
Proteins
• Should supply 10-35% of daily energy
• Proteins made of 20 amino acids
• Essential amino acids must come from diet
Fats
• Should supply 20-35% of daily
energy
• Types of fats
– Monosaturated (good)
– Polyunsaturated (good)
– Saturated (bad)
– Trans fats (bad)
Vitamins
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Play vital role in body function
Most are derived from diet
Required in small amounts
Excess of some can be toxic
fat soluble: vitamins A,D,E,and K
water soluble: the other nine vitamins
Minerals
• Inorganic substances
• Transported as ions by bloodstream
• Variety of uses
Water
• No set amount daily
• Body must maintain normal hydration
Digestion
• Breaking of food particles into molecules
• Unnecessary in autotrophs, (self feeders)
• Two types of digestion
– Intracellular
– Extracellular
Organisms with Intracellular
Digestion
Organisms with Intracellular &
Extracellular Digestion
Extracellular Digestion
Fungi
Extracellular Digestion
Most Animals
Extracellular Digestion
• In organisms with & without a digestive
system
– Fungi – no digestive system
– Most animals – digestive system
• Relies on enzymes (chemical digestion)
• Mechanical digestion may also be present
Human Digestion
• Mechanical Digestion
– Oral cavity by teeth
– Stomach churning
• Chemical digestion
– Hydrochloric acid-denatures proteins, softens
connective tissue, converts pepsinogen to pepsin &
kills most bacteria
– Bile salts emulsify lipids
– Enzymes cleave chemical bonds (see table 27.3)
• proteases, amylases, lipases
Digestion in the Mouth
• Salivary glands
– Produces saliva
• Mostly water
• Some enzymes
– Salivary amylase
• Starch breakdown
– Bacteria killing enzymes
– mucus
Digestion in the Mouth
• Teeth
– Mechanical digestion
– Different teeth
• Different functions
• Fit omnivore diet
Swallowing
• Food is formed into a bolus
– Chewed & moistened
– Formed by tongue
• Bolus is pushed into upper pharynx
• Soft palate seals off nasopharynx
Epiglottis
• Folds over opening to larynx
• Directs food into esophagus
• Esophagus moves food toward stomach
– Peristalsis = slow rhythmic squeezing
– Gravity helps movement
Peristalsis
Stomach
• Muscular sac
– Churns & mixes food
• Gastric glands
– Produce gastric juice
• Pepsinogen to pepsin
• hydrochloric acid
– Gastrin
• Hormone
• Controls gastric juices
– Hydrochloric acid
– Mucus-protection
Structure of Stomach
Food in the Stomach
• Mixed with gastric juices
(hydrochloric acid & pepsinogen)
• Churned by muscles
(3 layers of smooth muscles)
• Leaves as paste (chyme)
• Process takes 2-6 hours
Small Intestine
• Site of most digestion
• Site of nutrient absorption
• Area of association with
accessory organs
– Liver
– Pancreas
– Gall bladder
Pancreas
• Secretes many enzymes
(proteases, amylase, lipase)
• Empties into duodenum
• Alkaline solution to help
neutralize acids
(sodium bicarbonate)
Liver
• Secretes bile
(stored in gall
bladder)
• Components:
Bile salts & bile
pigments
• Emulsifies fats
Gall Bladder
• Stores bile
• Releases bile into duodenum
Digestion in Small Intestine
• Pancreatic amylase
– Carbohydrates to maltose
• Pancreatic proteases
– Chymotrypsin
– Trypsin
– Carboxypeptidase
• Pancreatic lipase
– Fats
• Disaccharidases (sm. Int.)
– Further breaks down sugars
• Peptidases (sm. intestine)
Absorption in Small Intestine
• Villi & microvilli Projections to increase surface area
• Infoldings – increase surface area
• Energy helps nutrients cross membranes
• Nutrients diffuse into capillaries
– Blood capillaries for all but lipids
– Lacteals pick up lipids
Hormones Control Digestive Enzymes
Large Intestine
• Areas of Colon
– Cecum
– Rectum
– Terminates at anus
Large Intestine Function
• Concentration & elimination of solids
• No digestive function
• Absorption of water & sodium ions
• Home for bacteria that produce vitamin K
Overweight & Obesity
• Risk factors for many medical conditions
End chapter 27