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Food and Nutrients Food Any substance, either raw or
processed which is meant for human consumption
Nutrients The components of food that the body can use for growth, repair and energy
Homeostatic RegulationGlucose level rises, insulin is secreted
Insulintransport of glucoseliver & muscle store glucose lblood levels drop
Glucose level drops glucagon is made to oppose the effect of insulin
Glucagon promotes the breakdown of glycogen blood glucose levels rise
Appetite Regulating Hormones
PYY is an appetite suppressant
Ghrelin triggers hunger
Insulin suppresses appetite
Leptin suppresses appetite
Essential Nutrients
Essential AA Essential fatty acids Vitamins MineralsUndernourishment vs. malnutrition
Essential Amino Acids
Animals require 20 AA
Can synthesize most 8 are essential, must
obtain from food How do vegetarians
get all essential AA?
Essential Nutrients What happens if an animal’s diet is
missing an essential nutrient?Deficiency Diseases
scurvy — vitamin C (collagen production) rickets — vitamin D (calcium absorption) blindness — vitamin A (retinol production) anemia — vitamin B12 (coenzyme function) kwashiorkor — protein
Intracellular Digestion in Paramecium Digestion occurs in
specialized compartments
Intracellular digestion occurs in protists and sponges
Gastrovascular Cavities and Extracellular Digestion
Gastrovascular cavities do both digestion and distribution Ex. Cnidarians,
platyhelminthes (flat worms)
Two-way digestion
Stages of Food Processing
1. Ingestion: eating or drinking2. Digestion : Breaking food into smaller
molecules• Mechanical • Chemical (Enzymes)
3. Absorption: nutrient molecules enter blood, the circulatory system transports it through out the body
4. Elimination: undigested material passes out of the body
The Digestive System Functions like a series of tube like
organs which pass through the body from the mouth to the anus Alimentary Canal
Alimentary Canal can be about 30’ long
Accessory organs Pancreas, Liver, Gallbladder secrete enzymes that are released into the food tube
It all begins in the mouth . . .
Teeth, tongueSalivary glands
MucusAmylase
Only carbohydrates are digested here
Digestion in the Stomach Muscular organ Acts as a
reservoir where food is prepared for digestion in the SI
Produces Gastric Juices
Stomach Functions1. Food Storage2. Mechanical Digestion3. Chemical DigestionSecretions:1. Mucus2. EnzymePepsinogen3. HCL
CHYME semi-fluid food mixture leaves.
Protection from Self-Digestion
Protective liningMain enzyme -Pepsin is inactive Pepsinogen when secreted
Digestion in the Stomach Pepsinogen Comes in contact with
HCl Pepsin Pepsin converts proteins into
peptones Acidity of Gastric juices kills some
bacteria that enters with food Gastric Juices stimulated by
psychological and chemical means Peristaltic process of moving chyme into
the SI takes place for 6hrs
Digestion in the Small Intestine Main stage of Digestion As chyme enters the SI secretes juices that
are alkaline and neutralizes the acidity SI maltase,lactase,sucrase breaks
disaccharides Liver secretes bile emulsifies fats Dipeptidases dipeptides into AAs Pancreas
Trypsin & Chymotrypsin break down proteins
Amylase converts starch into maltoseLipase breaks fats
Process is complete in about 4 hrs
1. Anatomy:2. Functions
a. Reclaim waterb. Synthesis of vitamins by E. coli
FecesRectumAnus
DiarrheaConstipation
Large Intestine = Colon
Food as Fuel Carbohydrates, fats and proteins are
all used to generate ATP Fats9 Calories/gm, Proteins and
Carbs 4Calories/gm 1 Calorie (kilocalorie)= 1000 calories Basic Calorie need 2200 for female
teens, 2500 males
Accessory Organs
LIVER A. Secretions B. Functions
1. Digestive function 2. Glycogenesis 3. Gluconeogenesis 4. Glycogenolysis 5. Hematopoiesis in embryo 6. Detoxification 7. Damaged red blood cell
removal bile contains pigment by-
products of RBC bile pigments eliminated from
body with feces brown feces = rusty iron from
hemoglobin!
Pancreas a. Anatomy
Acinar cells Islets cells:Alpha, Beta
b. Functions c. Digestive Enzyme 1. trypsinogen 2. chymotrypsinogen 3. carboxypeptidase 4. aminopeptidase 5. pancreatic amylase 6. pancreatic lipase
These accessory organs secrete their enzymes and a basic fluid into the duodenum of the small intestine
Small Intestinea. Anatomy
1. size2. villi3. lacteals4. glands
b. Functionsc. Secretions
1. mucus2. maltase3. sucrase4. lactase5. peptidase6. enterokinase
Absorption in the Small Intestinevillimicrovillichylomicrons fats, cholesterol, wrapped in protein
leave cells by exocytosis
lactealslymphatic systemhepatic portal vein
Hormonal Control Enterogastrone Gastrin Cholecystokinin secreted in
response to the presence of amino acids or fatty acids, causes the gallbladder to contract and release bile into the small intestine and triggers the release of pancreatic enzymes
Secretin chyme(acidic pH)enters the duodenum, signals the pancreas to release bicarbonate to neutralize the chyme
Flora of Large Intestines Living in the large intestine is a rich flora of
mostly harmless bacteria Escherichia coli
a favorite research organism bacteria produce vitamins
vitamin K; biotin, folic acid & other B vitamins generate gases
by-product of bacterial metabolism
methane, hydrogen sulfide
Large Intestines (colon) Reclaiming water
used as solvent for various digestive juices
~7L of fluid secreted intodigestive tract daily
> 90% of water reabsorbed diarrhea = insufficient
water absorbed constipation = too much
water absorbed
Rectum Terminal portion of colon
Feces contain masses of bacteria undigested materials, mainly cellulose
roughage or fiber salts
appendix
Digesting CelluloseHow well you digest cellulose governs life
strategy of herbivoresCOW
Can digest cellulose well; not need to eat supplemental sugars
GORILLACan’t digest cellulose well; must supplement with sugar sources, like fruit