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24/04/12 Overview: The Need to Feed Animal Nutri1on BIOL212 NSCC •  Food is taken in, taken apart, and taken up in the process of animal nutri&on •  In general, animals fall into three categories: –  Herbivores eat mainly plants and algae –  Carnivores eat other animals –  Omnivores regularly consume animals as well as plants or algae •  Most animals are also opportunis1c feeders © 2011 Pearson Education, Inc.
Figure 41.1
Video: Lobster Mouth Parts Video: Shark Ea1ng a Seal © 2011 Pearson Education, Inc.
1 24/04/12 Concept 41.1: An animal s diet must supply chemical energy, organic molecules, and essen1al nutrients •  An animal s diet provides: –  Chemical energy, which is converted into ATP to power cellular processes –  Organic building blocks, such as organic carbon and organic nitrogen, to synthesize a variety of organic molecules –  Essen&al nutrients, which are required by cells and must be obtained from dietary sources © 2011 Pearson Education, Inc.
Essen1al Nutrients •  There are four classes of essen1al nutrients: –  Essen1al amino acids –  Essen1al faQy acids –  Vitamins –  Minerals © 2011 Pearson Education, Inc.
Essen%al Amino Acids •  Animals require 20 amino acids and can synthesize about half from molecules in their diet •  The remaining amino acids, the essen&al amino acids, must be obtained from food in preassembled form •  Meat, eggs, and cheese provide all the essen1al amino acids and are thus complete proteins © 2011 Pearson Education, Inc.
•  Most plant proteins are incomplete in amino acid composi1on •  Individuals who eat only plant proteins need to eat specific plant combina1ons to get all the essen1al amino acids •  Some animals have adapta1ons that help them through periods when their bodies demand extraordinary amounts of protein © 2011 Pearson Education, Inc.
2 24/04/12 Figure 41.2
Essen%al Fa0y Acids •  Animals can synthesize most of the faQy acids they need •  The essen&al fa7y acids must be obtained from the diet and include certain unsaturated faQy acids (i.e., faQy acids with one or more double bonds) •  Deficiencies in faQy acids are rare © 2011 Pearson Education, Inc.
Table 41.1
Vitamins •  Vitamins are organic molecules required in the diet in small amounts •  Thirteen vitamins are essen1al for humans •  Vitamins are grouped into two categories: fat-­‐soluble and water-­‐soluble © 2011 Pearson Education, Inc.
3 24/04/12 Table 41.2
Minerals •  Minerals are simple inorganic nutrients, usually required in small amounts •  Inges1ng large amounts of some minerals can upset homeosta1c balance © 2011 Pearson Education, Inc.
Dietary Deficiencies Deficiencies in Essen%al Nutrients •  Malnourishment is the long-­‐term absence from the diet of one or more essen1al nutrients •  Deficiencies in essen1al nutrients can cause deformi1es, disease, and death •  Golden Rice is an engineered strain of rice with beta-­‐carotene, which is converted to vitamin A in the body © 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
4 24/04/12 Figure 41.3
Undernutri%on •  Undernutri1on results when a diet does not provide enough chemical energy •  An undernourished individual will –  Use up stored fat and carbohydrates –  Break down its own proteins –  Lose muscle mass –  Suffer protein deficiency of the brain –  Die or suffer irreversible damage © 2011 Pearson Education, Inc.
Figure 41.4
Assessing Nutri1onal Needs •  Gene1c defects that disrupt food uptake provide informa1on about human nutri1on –  For example, hemochromatosis causes iron buildup without excessive iron intake •  Insights into human nutri1on have come from epidemiology, the study of human health and disease in popula1ons •  Neural tube defects were found to be the result of a deficiency in folic acid in pregnant mothers RESULTS
Group
Number of
infants/fetuses
studied
Infants/fetuses
with a neural
tube defect
Vitamin supplements
(experimental group)
141
1 (0.7%)
No vitamin supplements
(control group)
204
12 (5.9%)
© 2011 Pearson Education, Inc.
5 24/04/12 Figure 41.5
Concept 41.2: The main stages of food processing are inges1on, diges1on, absorp1on, and elimina1on •  Inges&on is the act of ea1ng Mechanical
digestion
1 Ingestion
Nutrient molecules
enter body cells
Chemical
digestion
(enzymatic
hydrolysis)
2 Digestion
Undigested
material
3 Absorption
4 Elimination
© 2011 Pearson Education, Inc.
Figure 41.5a
Suspension Feeders •  Many aqua1c animals are suspension feeders, which si_ small food par1cles from the water © 2011 Pearson Education, Inc.
6 24/04/12 Figure 41.6
Suspension Feeders and Filter Feeders
Baleen
Substrate
Feeders
Fluid Feeders
Substrate Feeders •  Substrate feeders are animals that live in or on their food source Caterpillar Feces
Bulk Feeders
© 2011 Pearson Education, Inc.
Fluid Feeders Bulk Feeders •  Fluid feeders suck nutrient-­‐rich fluid from a living host •  Bulk feeders eat rela1vely large pieces of food © 2011 Pearson Education, Inc.
© 2011 Pearson Education, Inc.
7 24/04/12 •  Diges&on is the process of breaking food down into molecules small enough to absorb •  Mechanical diges1on, including chewing, increases the surface area of food •  Chemical diges1on splits food into small molecules that can pass through membranes; these are used to build larger molecules •  In chemical diges1on, the process of enzyma&c hydrolysis splits bonds in molecules with the addi1on of water © 2011 Pearson Education, Inc.
Diges1ve Compartments •  Most animals process food in specialized compartments •  These compartments reduce the risk of an animal diges1ng its own cells and 1ssues © 2011 Pearson Education, Inc.
•  Absorp&on is uptake of nutrients by body cells •  Elimina&on is the passage of undigested material out of the diges1ve system © 2011 Pearson Education, Inc.
Intracellular Diges%on •  In intracellular diges&on, food par1cles are engulfed by phagocytosis •  Food vacuoles, containing food, fuse with lysosomes containing hydroly1c enzymes © 2011 Pearson Education, Inc.
8 24/04/12 Figure 41.7
Extracellular Diges%on Mouth
•  Extracellular diges&on is the breakdown of food par1cles outside of cells •  It occurs in compartments that are con1nuous with the outside of the animal s body •  Animals with simple body plans have a gastrovascular cavity that func1ons in both diges1on and distribu1on of nutrients Tentacles
Food
1 Digestive
enzymes released
2 Food
particles broken
down
3 Food particles
engulfed and
digested
Epidermis
Video: Hydra Ea1ng Daphnia Gastrodermis
© 2011 Pearson Education, Inc.
Figure 41.8
Esophagus
Crop
Gizzard
Intestine
Pharynx
•  More complex animals have a diges1ve tube with two openings, a mouth and an anus •  This diges1ve tube is called a complete diges&ve tract or an alimentary canal •  It can have specialized regions that carry out diges1on and absorp1on in a stepwise fashion Anus
Mouth
(a) Earthworm
Foregut Midgut Hindgut
Esophagus
Rectum
Anus
Esophagus
Crop
Stomach
Gizzard
Intestine
Mouth
Crop
Gastric cecae
Mouth
(b) Grasshopper
Anus
(c) Bird
© 2011 Pearson Education, Inc.
9 24/04/12 Concept 41.3: Organs specialized for sequen1al stages of food processing form the mammalian diges1ve system •  The mammalian diges1ve system consists of an alimentary canal and accessory glands that secrete diges1ve juices through ducts •  Mammalian accessory glands are the salivary glands, the pancreas, the liver, and the gallbladder © 2011 Pearson Education, Inc.
Tongue
Oral cavity
Salivary
glands
Pharynx
Esophagus
Liver
Sphincter
Small
intestine
Large
intestine
Rectum
Anus
The Oral Cavity, Pharynx, and Esophagus Mouth
Esophagus
Gallbladder
•  Valves called sphincters (muscles) regulate the movement of material between compartments © 2011 Pearson Education, Inc.
Figure 41.9
Pancreas
•  Food is pushed along by peristalsis, rhythmic contrac1ons of muscles in the wall of the canal Sphincter
Stomach
Duodenum of
small intestine
Gallbladder
Liver
Pancreas
Salivary
glands
Stomach
Small
intestine
Large
intestine
Rectum
Anus
Schematic diagram
•  The first stage of diges1on is mechanical and takes place in the oral cavity •  Salivary glands deliver saliva to lubricate food •  Teeth chew food into smaller par1cles that are exposed to salivary amylase, ini1a1ng breakdown of glucose polymers •  Saliva also contains mucus, a viscous mixture of water, salts, cells, and glycoproteins © 2011 Pearson Education, Inc.
10 24/04/12 •  The tongue shapes food into a bolus and provides help with swallowing •  The throat, or pharynx, is the junc1on that opens to both the esophagus and the trachea •  The esophagus connects to the stomach •  The trachea (windpipe) leads to the lungs © 2011 Pearson Education, Inc.
•  The esophagus conducts food from the pharynx down to the stomach by peristalsis •  Swallowing causes the epiglogs to block entry to the trachea, and the bolus is guided by the larynx, the upper part of the respiratory tract •  Coughing occurs when the swallowing reflex fails and food or liquids reach the windpipe © 2011 Pearson Education, Inc.
Figure 41.10-3
Tongue
Bolus of
food
Pharynx
Epiglottis
up
Glottis
Larynx
Trachea
Diges1on in the Stomach •  The stomach stores food and secretes gastric juice, which converts a meal to acid chyme Esophageal
sphincter
contracted
Esophagus
To lungs To stomach
Relaxed
muscles
Contracted
muscles
Sphincter
relaxed
Stomach
© 2011 Pearson Education, Inc.
11 24/04/12 Chemical Diges%on in the Stomach •  Gastric juice has a low pH of about 2, which kills bacteria and denatures proteins •  Gastric juice is made up of hydrochloric acid (HCl) and pepsin •  Pepsin is a protease, or protein-­‐diges1ng enzyme, that cleaves proteins into smaller pep1des © 2011 Pearson Education, Inc.
Figure 41.11
© 2011 Pearson Education, Inc.
Esophagus
Sphincter
Stomach
10 µm
Sphincter
Gastric pits on
interior surface
of stomach
Gastric gland
Mucous cell
Chief cell
•  Parietal cells secrete hydrogen and chloride ions separately into the lumen (cavity) of the stomach •  Chief cells secrete inac1ve pepsinogen, which is ac1vated to pepsin when mixed with hydrochloric acid in the stomach •  Mucus protects the stomach lining from gastric juice Small
intestine
Folds of
epithelial
tissue
Epithelium
3
Pepsinogen
Chief
cell
•  Gastric ulcers, lesions in the lining, are caused mainly by the bacterium Heliobacter pylori 2
Pepsin
HCl
1
Cl-
H+
Parietal
cell
Parietal cell
© 2011 Pearson Education, Inc.
12 24/04/12 Stomach Dynamics Diges1on in the Small Intes1ne •  Coordinated contrac1on and relaxa1on of stomach muscle churn the stomach s contents •  Sphincters prevent chyme from entering the esophagus and regulate its entry into the small intes1ne © 2011 Pearson Education, Inc.
•  The small intes&ne is the longest sec1on of the alimentary canal •  It is the major organ of diges1on and absorp1on © 2011 Pearson Education, Inc.
Figure 41.12-4
Carbohydrate digestion
Oral cavity,
Polysaccharides Disaccharides
pharynx,
esophagus
Salivary amylase
Smaller
Maltose
polysaccharides
Stomach
Protein digestion
Proteins
Pepsin
Small polypeptides
Small
intestine
(enzymes
from
pancreas)
Pancreatic amylases
Pancreatic trypsin and
chymotrypsin
Nucleic acid digestion
Fat digestion
DNA, RNA
Fat (triglycerides)
Pancreatic
nucleases
•  The first por1on of the small intes1ne is the duodenum, where chyme from the stomach mixes with diges1ve juices from the pancreas, liver, gallbladder, and the small intes1ne itself Disaccharides
Smaller
polypeptides
Nucleotides
Pancreatic lipase
Pancreatic carboxypeptidase
Glycerol, fatty acids,
monoglycerides
Small peptides
Small
intestine
(enzymes
from
epithelium)
Disaccharidases
Dipeptidases, carboxypeptidase, and
aminopeptidase
Nucleotidases
Nucleosides
Nucleosidases
and
phosphatases
Monosaccharides
Amino acids
Nitrogenous bases,
sugars, phosphates
© 2011 Pearson Education, Inc.
13 24/04/12 Pancrea%c Secre%ons •  The pancreas produces proteases, trypsin and chymotrypsin, that are ac1vated in the lumen of the duodenum •  Its solu1on is alkaline and neutralizes the acidic chyme. © 2011 Pearson Education, Inc.
Secre%ons of the Small Intes%ne •  The epithelial lining of the duodenum produces several diges1ve enzymes •  Enzyma1c diges1on is completed as peristalsis moves the chyme and diges1ve juices along the small intes1ne •  Most diges1on occurs in the duodenum; the jejunum and ileum func1on mainly in absorp1on of nutrients and water © 2011 Pearson Education, Inc.
Bile Produc%on by the Liver •  In the small intes1ne, bile aids in diges1on and absorp1on of fats •  Bile is made in the liver and stored in the gallbladder •  Bile also destroys nonfunc1onal red blood cells © 2011 Pearson Education, Inc.
Absorp1on in the Small Intes1ne •  The small intes1ne has a huge surface area, due to villi and microvilli that are exposed to the intes1nal lumen •  The enormous microvillar surface creates a brush border that greatly increases the rate of nutrient absorp1on •  Transport across the epithelial cells can be passive or ac1ve depending on the nutrient © 2011 Pearson Education, Inc.
14 24/04/12 Figure 41.13a
Figure 41.13b
Villi
Vein carrying
blood to liver
Microvilli (brush
border) at apical
(lumenal) surface
Lumen
Epithelial
cells
Blood
capillaries
Epithelial
cells
Muscle layers
Villi
Intestinal wall
Large
circular
folds
Basal
surface
Lacteal
Key
Key
Nutrient
absorption
•  The hepa&c portal vein carries nutrient-­‐rich blood from the capillaries of the villi to the liver, then to the heart •  The liver regulates nutrient distribu1on, interconverts many organic molecules, and detoxifies many organic molecules © 2011 Pearson Education, Inc.
Lymph
vessel
Nutrient
absorption
•  Epithelial cells absorb faQy acids and monoglycerides and recombine them into triglycerides •  These fats are coated with phospholipids, cholesterol, and proteins to form water-­‐soluble chylomicrons •  Chylomicrons are transported into a lacteal, a lympha1c vessel in each villus •  Lympha1c vessels deliver chylomicron-­‐containing lymph to large veins that return blood to the heart © 2011 Pearson Education, Inc.
15 24/04/12 Figure 41.14a
Figure 41.14b
LUMEN
Triglycerides
OF SMALL
INTESTINE
Epithelial
cell
Fatty acids
Triglycerides
Monoglycerides
Phospholipids,
cholesterol,
and proteins
Chylomicron
Triglycerides
Lacteal
Figure 41.15
Absorp1on in the Large Intes1ne •  The colon of the large intes&ne is connected to the small intes1ne •  The cecum aids in the fermenta1on of plant material and connects where the small and large intes1nes meet •  The human cecum has an extension called the appendix, which plays a very minor role in immunity Ascending
portion
of colon
Small
intestine
Cecum
Appendix
© 2011 Pearson Education, Inc.
16 24/04/12 •  A major func1on of the colon is to recover water that has entered the alimentary canal •  The colon houses bacteria (e.g., Escherichia coli) which live on unabsorbed organic material; some produce vitamins •  Feces, including undigested material and bacteria, become more solid as they move through the colon © 2011 Pearson Education, Inc.
Concept 41.4: Evolu1onary adapta1ons of vertebrate diges1ve systems correlate with diet •  Diges1ve systems of vertebrates are varia1ons on a common plan •  However, there are intriguing adapta1ons, o_en related to diet © 2011 Pearson Education, Inc.
•  Feces are stored in the rectum un1l they can be eliminated through the anus •  Two sphincters between the rectum and anus control bowel movements © 2011 Pearson Education, Inc.
Dental Adapta1ons •  Den11on, an animal s assortment of teeth, is one example of structural varia1on reflec1ng diet •  The success of mammals is due in part to their den11on, which is specialized for different diets •  Nonmammalian vertebrates have less specialized teeth, though excep1ons exist –  For example, the teeth of poisonous snakes are modified as fangs for injec1ng venom © 2011 Pearson Education, Inc.
17 24/04/12 Figure 41.16
Stomach and Intes1nal Adapta1ons Carnivore
•  Many carnivores have large, expandable stomachs •  Herbivores and omnivores generally have longer alimentary canals than carnivores, reflec1ng the longer 1me needed to digest vegeta1on Herbivore
Key
Omnivore
Incisors
Canines
Premolars
Molars
© 2011 Pearson Education, Inc.
Figure 41.17
Mutualis1c Adapta1ons Small intestine
Small
intestine
Stomach
•  Many herbivores have fermenta1on chambers, where mutualis1c microorganisms digest cellulose •  The most elaborate adapta1ons for an herbivorous diet have evolved in the animals called ruminants Cecum
Carnivore
Colon
(large
intestine)
Herbivore
© 2011 Pearson Education, Inc.
18 24/04/12 Figure 41.18
2 Reticulum
1 Rumen
Esophagus
Concept 41.5: Feedback circuits regulate diges1on, energy storage, and appe1te •  The intake of food and the use of nutrients varies with an animal s diet and environment Intestine
4 Abomasum
3 Omasum
© 2011 Pearson Education, Inc.
Figure 41.19a
Regula1on of Diges1on •  Each step in the diges1ve system is ac1vated as needed •  The enteric division of the nervous system helps to regulate the diges1ve process •  The endocrine system also regulates diges1on through the release and transport of hormones 1
Food
Liver
Stomach
Gallbladder
Gastric
juices
Gastrin
+
Pancreas
Duodenum
of small intestine
Key
+ Stimulation
- Inhibition
© 2011 Pearson Education, Inc.
19 24/04/12 Figure 41.19b
Figure 41.19c
2
3
Bile
Chyme
Secretin
and CCK
-
CCK
Gastric
juices
+
-,
HCO3 enzymes
Secretin
+
CCK
Key
+ Stimulation
- Inhibition
+
Key
+ Stimulation
- Inhibition
Regula1on of Energy Storage Glucose Homeostasis •  The body stores energy-­‐rich molecules that are not needed right away for metabolism •  In humans, energy is stored first in the liver and muscle cells in the polymer glycogen •  Excess energy is stored in adipose 1ssue, the most space-­‐efficient storage 1ssue •  Oxida1on of glucose generates ATP to fuel cellular processes •  The hormones insulin and glucagon regulate the breakdown of glycogen into glucose •  The liver is the site for glucose homeostasis © 2011 Pearson Education, Inc.
–  A carbohydrate-­‐rich meal raises insulin levels, which triggers the synthesis of glycogen –  Low blood sugar causes glucagon to s1mulate the breakdown of glycogen and release glucose © 2011 Pearson Education, Inc.
20 24/04/12 Figure 41.20
Pancreas
secretes
insulin.
Transport of
glucose into
body cells
and storage
of glucose
as glycogen
•  Overnourishment causes obesity, which results from excessive intake of food energy with the excess stored as fat •  Obesity contributes to diabetes (type 2), cancer of the colon and breasts, heart aQacks, and strokes •  Researchers have discovered several of the mechanisms that help regulate body weight Stimulus:
Blood glucose
level rises
after eating.
Homeostasis:
70–110 mg glucose/
100 mL blood
Stimulus:
Blood glucose
level drops
below set point.
Breakdown
of glycogen
and release
of glucose
into blood
Regula1on of Appe1te and Consump1on Pancreas
secretes
glucagon.
© 2011 Pearson Education, Inc.
Figure 41.21
Satiety
center
Ghrelin
+
Insulin
-
•  Hormones regulate long-­‐term and short-­‐term appe1te by affec1ng a sa1ety center in the brain •  Studies on mice revealed that the hormone lep&n plays an important role in regula1ng obesity •  Lep1n is produced by adipose 1ssue and can help to suppress appe1te Leptin
PYY
-
© 2011 Pearson Education, Inc.
21 24/04/12 Figure 41.22
Figure 41.22a
EXPERIMENT
Obese mouse with mutant
ob gene (left) next to wild-type
mouse
RESULTS
Genotype pairing
(red type indicates
mutant genes)
Average change
in body mass (g)
of subject
Subject
Paired with
ob+ob+ , db+db+
ob+ob+ , db+db+
8.3
ob ob, db+db+
ob ob, db+db+
38.7
ob ob, db+db+
ob+ob+, db+db+
ob ob, db+db+
ob+ob+, db db
Obese mouse with mutant
ob gene (left) next to wild-type
mouse
8.2
-14.9*
*Due to pronounced weight loss and weakening, subjects in this pairing were
reweighed after less than eight weeks.
Figure 41.22b
Obesity and Evolu1on RESULTS
Genotype pairing
(red type indicates
mutant genes)
Average change
in body mass (g)
of subject
Subject
Paired with
ob+ob+ , db+db+
ob+ob+ , db+db+
8.3
ob ob, db+db+
ob ob, db+db+
38.7
ob ob, db+db+
ob+ob+, db+db+
8.2
ob ob, db+db+
ob+ob+, db db
•  A species of birds called petrels become obese as chicks; in order to consume enough protein from high-­‐fat food, chicks need to consume more calories than they burn -14.9*
*Due to pronounced weight loss and weakening, subjects in this pairing were
reweighed after less than eight weeks.
© 2011 Pearson Education, Inc.
22 24/04/12 Figure 41.23
•  The problem of maintaining weight partly stems from our evolu1onary past, when fat hoarding was a means of survival •  Individuals who were more likely to eat faQy food and store energy as adipose 1ssue may have been more likely to survive famines © 2011 Pearson Education, Inc.
Figure 41.UN01
Veins to heart
Hepatic portal vein
Lymphatic system
Mouth
Stomach
Esophagus
Secretions
from salivary
glands
Lipids
Absorbed food
(except lipids)
Small intestine
Secretions
Secretions from liver
from gastric
glands
Secretions from pancreas
Liver
Absorbed
water
Anus
Large
Rectum
intestine
23