Transcript Animal Metabolism, Nutrition, and Digestion

Animal
Metabolism,
Nutrition, and
Digestion
Chapter 40
CELLULAR RESPIRATION
40.1 Metabolic rate
depends on activity,
body size, and body
temperature.
Cellular respiration breaks down:
•Carbohydrates
•Fats
•Proteins for energy to make ATP
•NOTE: Cellular respiration does
NOT use nucleic acids
CELLULAR RESPIRATION REVIEW
 Glucose can be partially broken down in the absence of oxygen by
glycolysis.
 Occurs in the cytosol of the cell
 Breakdown of each glucose molecule results in 2 molecules of pyruvate
and 2 molecules of ATP
 Anaerobic metabolism
 If oxygen is not present, or is present only in small amounts, pyruvate is
converted by fermentation into lactic acid. Only 2 ATPs made by glycolysis
 Provides rapid but short-term energy to the cell
 Aerobic metabolism
 Carried out within the mitochondria of eukaryotic animals
 Requires oxygen diffusing into the mitochondria
 Provides a steady supply of 36 ATPs /molecule of glucose for longer -term,
sustainable activity.
 Pyruvate is processed by the citric acid cycle rather than converted to
lactic acid.
 The ETC and OxPhos result in 36-38 ATPs/mlecule of glucose
 Oxygen is used and water and CO2 is produced.
CELLULAR RESPIRATION REVIEW
Lipids: another important energy source for most animals.
 Lipids from the diet are broken down to glycerol and fatty acids
 These enter glycolysis or the Krebs Cycle to yield 36 -38 ATPs.
 Animals preferentially rely on fats for long-term energy supply.
Proteins: are also a useful energy source for animals.
 Proteins are needed for building and maintaining the body
 Constitute the enzymes and structural elements of cells and tissues
 Only following prolonged food deprivation (when fat and carbohydrate
reserves are depleted), do animals break down protein reserves to form
ATP.
QUICK CHECK
 Muscle protein, fat, and glycogen are all reservoirs of
energy. In what order are they used during a prolonged fast?
ANSWER
 Glycogen
 Fat
 Muscle protein
METABOLIC RATE
Metabolic rate:
•An animal’s overall rate of energy use
•Speed of chemical reactions in an organism
Can be measured by:
•Rate of oxygen consumption
•Reflects aerobic ATP production
O 2 CONSUMPTION DURING ACTIVITY
Metabolic rate increases with increased physical activity.
BODY TEMPERATURE AND ACTIVITY
METABOLIC RATE AND BODY SIZE
•Larger animals consume
more energy and have
higher metabolic rates
than smaller animals
•However, the increase in
metabolic rate is not
proportional to mass.
QUICK CHECK
 Does a dog that is twice as heavy as a cat have twice the
resting metabolic rate?
ANSWER
 No
 Metabolic rate increases with increasing mass, the
relationship between the two is not linear
 Instead, metabolic rate increases with mass raised to the ¾
power.
 Thus, a dog that is twice as heavy as a cat has a metabolic
rate that is less than twice as much as the cat.
METABOLIC RATE AFFECTED BY RUNNING
& BODY SIZE
METABOLIC RATES
Metabolic rate: also affected by body temperature
2 categories of animals:
•Endotherms: produce their own heat as by-products of their own metabolism
and breakdown of food
•Usually have a body temp higher than environment
•Mammals, (including humans) & birds
•Have a higher metabolic rate than ectotherms
•Able to be active over broader range of external temperatures
•Ectotherms: obtain their heat from environment; usually by behavioral means
•Most fish, amphibians, reptiles, invertebrates
•The activity level & metabolic rate both increase with increasing body
temperature
•However, their metabolic rate 25% of endotherm
•Cannot sustain prolonged activity
HOMEOSTASIS AND THERMOREGULATION
ENERGY BALANCE
An animal in energy balance takes in the same amount of calories of energy
from food that it uses over time to meet its metabolic needs
Energy intake = Energy use
When energy intake does not equal energy used, there is an
energy imbalance.
Energy intake deficit
 Undernourishment and muscle wasting
Energy intake excess  Obesity
ANIMAL NUTRITION AND DIET
40.2 An animal’s diet supplies the energy it needs for
homeostasis and essential nutrients it cannot
synthesize on its own.
ESSENTIAL AMINO ACIDS FOR HUMANS
Humans cannot synthesize 8 of the 20 amino acids
MINERALS REQUIRED BY HUMANS
ESSENTIAL VITAMINS FOR HUMANS
13 essential vitamins for humans
FILTER FEEDING
40.3 Different animals have different adaptations for feeding.
Ingestion: the process of eating
Suspension filter feeding; most common
form of food capture; clams, oysters
Filtering water with food through sieves in
oral cavity….i.e. baleen whales
SUCTION FEEDING
•Rapid expansion of mouth draws water/prey in; when fish closes its mouth, water
is pumped out past the gills
•“Sit and wait” predators
•Many fish feed this way
ACTIVE SWIMMING TO FEED
Larger fish; marine mammals like sharks, whales, dolphins
PHYLOGENY OF VERTEBRATES (JAWS)
JAWS AND TEETH
ORGANIZATION OF DIGESTIVE TRACTS
40.4 The digestive tract is a
tube-like structure with regions
specialized for different
functions.
Digestion: the breakdown (mechanical or
enzymatic hydrolysis) of macromolecules
into smaller monomers
• Digestive tract (gut)..digestive tube
that runs from mouth to anus
•Allows for specialized areas, such as:
•Storage (foregut)
•Chemical breakdown (foregut)
•Absorption of released
nutrients(midgut)
•Elimination of waste
products(hindgut)
MAIN STAGES OF FOOD PROCESSING
 4 Major Stages:
 Ingestion: eating
 Digestion: breakdown (mechanical or enzymatic hydolysis) of
macromolecules into smaller monomers
 Absoprtion: uptake of nutrients by body cells
 Elimination: passage of undigested material out of body as feces
SWALLOWING
HUMAN ORAL CAVITY AND PHARYNX
Oral Cavity: contains 3 pairs of salivary glands
•Saliva: secretes more than 1 liter/day
•Contains 99.5% water
•Also salivary amylase: enzyme that helps digest starch and glycogen
•NOTE: carb/polysaccharide digestion begins here
•Mucin, buffers, antimicrobial agents
•Tongue: used to taste, help chewing, mix food with saliva to form bolus;
pushes bolus into pharynx
Pharynx: the region we call our “throat”; an intersection which leads to both
trachea/windpipe and esophagus
•When we swallow, the top of the trachea (called the larynx = your voice
box) moves up so that its opening (the glottis) is blocked by a
cartilaginous flap called the epiglottis . Seen as the bobbing of the Adam’s
Apple.
•Waves of smooth muscle contraction called peristalsis move the bolus
down esophagus to stomach.
ESOPHAGUS
 About 10 inches long; descends behind trachea; passes
through diaphragm to somach
 Conducts food from pharynx to stomach
 Peristaltic waves move food
 Muscles at top of esophagus are skeletal (voluntary), but
then involuntary waves of smooth muscle take over
 Salivary amylase continues to digest starch/polyscahharides
DIGESTIVE CONTROL
STOMACH
•J-shaped bag on left side of digestive cavity, just below diaphragm
•Can stretch to hold 2 liters food/water
•Secretes mucus and gastric juice
•Gastric juice = hydrochloric acid (pH of 2) and pepsin (enzyme which digests
protein)
•Stomach has 2 sphincters:
•Cardiac sphincter: goes into stomach; prevents backflow of acidic chyme
(mixture of bolus and gastric juice) into esophagus. Medically called GERD.
•Pyloric sphincter: leads out of stomach into small intestine
•Stomach is where proteins are 1st digested. Proteins are the only molecules that the
stomach digests. High protein meal, long time in stomach, and vice versa.
SMALL INTESTINE
•Longest section of alimentary canal; about 20 ft long
Duodenum: (about 10 inches long) where most digestion finishes (carb, protein,
NA, and lipids)
•NOTE: lipid and NA are ONLY digested in duodenum
•By end of duodenum, most food should be monomers (monosaccharides,
glycerol, fa, aa, nucleotides)
•When fats enter, cells lining the duodenum release a hormone called
cholecystokinin (CCK), which causes the gallbladder to contract, thus releasing
bile into the duodenum.
Jejunum (8 ft long) and Ileum (12 ft long):does nutrient absorption
•Villi: fingerlike projections in folds of small intestine; huge surface area for
absorption
•Absorbed aa and sugars enter capillaries and carried by blood to liver
•Lipids mixed with cholesterol to form chylomicrons, which move into lacteals
and into lymphatic system
HUMAN ACCESSORY GLANDS
•Pancreas: not part of the digestive tube; it is an accessory gland that lies between
the stomach and duodenum. Has 2 digestive functions:
•Discharges pancreatic enzymes (lipase and trypsin) into duodenum for
finishing enzymatic digestion
•Also secretes a buffer of alkaline sodium bicarbonate into duodenum
•Liver: not part of digestive tube; makes bile which it then stores in gall bladder
•Bile: breaks down fat
•Made of bile pigments, bile salts, and cholesterol
•Bile salts from gall bladder are secreted into duodenum to coat the fat
molecules and keep them from clumping. Called emulsification
•Large surface area is exposed to lipase which breaks it down into micelles
for small intestine to absorb
•Gall bladder: stores the bile that the liver makes
SMALL INTESTINE
VILLI AND MICROVILLI
GLUCOSE ABSORPTION
LARGE INTESTINE
LARGE INTESTINE
 About 4/5 ft long; Responsible for:
 Absorption of water
 Synthesis of vitamins not obtained from food (Vitamin K)
 Abosprtion of vitamins/minerals
 Compaction
 Excretion of wastes and excess salts
 Cecum: first 2/3 inches; blind sac; easily get polyps here
 Appendix: attached to cecum; has a minor immune function
 Colon: ascending; transverse; descending; sigmoid
 Rectum: storage chamber for feces; controlled by 2 sphincters;
one voluntary, one involuntary
 Anus: elimination
 Large intestine contains a host of microorganisms.Most of the
dry w eight of feces is E. coli bacteria.
MAMMALIAN INTESTINE
FOREGUT FERMENTER
Ruminant Herbivorous Animals: evolved
specialized 4-chambered stomach (rumen,
reticulum, omasum, and abomasum) to digest
cellulose
•I.e. cows, sheep, goats, termites….lack
cellulase to break down cellulose
•Their stomach compartments have bacteria
that make cellulase……symbiotic relationship
HINDGUT FERMENTER
Other mammalian herbivores are hindgut
fermenters:
•Koalas, rabbits, horses
•Occurs in colon and cecum
•Less efficient for nutrient extraction since nutrients
already absorbed by small intestine