Animal Nutrition

Nutrition: food taken in, food taken apart, food taken up

Nutrition is essential for Energy production (ATP): all activities from

molecular to cellular level Biosynthesis: supply raw materials to build

complex molecules to grow, maintain & reproduce

Animals have diverse diets: herbivores

carnivores

omnivores

Most animals are opportunistic feeders

Essential nutrients: materials that an animal’s cells require but cannot synthesize.

4 classes of essential nutrients: essential amino acids essential fatty acids vitamins minerals

Amino acids: Organic molecule with an amino group and an acid group

Essential amino acids: Must be obtained from prefabricated food 8 in humans (infants - 9 – histidine)

Animal products (meat, cheese, eggs) are complete “proteins”.

Most plants have “incomplete proteins”

Methionine

Valine

Threonine

Phenylalanine

Leucine

Isoleucine

Tryptophan

Lysine

Essential amino acids for adults

Beansand otherlegumes

Corn (maize)and other grains

Temporary use of muscle protein as a source of amino acids (penguins).

Essential fatty acids: Long carbon chain with an acid group Unsaturated fatty acids (linoleic acid to make membrane

phospholipids) Seeds, grains vegetables

SaturatedFatty acid

Unsaturated Fatty acid

Vitamins: Organic molecules with diverse functions;

required in the diet in small amounts. Water soluble: B-complex, C, Biotin Fat soluble: A, D, E, K

Minerals: Inorganic nutrients required in small amounts

Dietary deficiencies: Undernourishment: diet that supplies

insufficient chemical energy Malnourishment: long term absence from

diet of one or more essential nutrients

Undernourishment: diet that supplies insufficient chemical energy Body uses up stored fats

and carbohydrates Breaks down muscles Brain will become protein

deficient Death or irreversible

damage Places with turmoil in

society (war, drought), or eating disorders

Malnourishment: long term absence from diet of one or more essential nutrients Among herbivores (fragile bones from lack of

phosphorus) Carnivores switch prey Disease, deformities, death in humans, especially

children

Four main feeding mechanisms in animals: Suspension feeders Substrate feeders Fluid feeders Bulk feeders

Suspension feeders: clams, oysters, whales

Substrate feeders: live in or on the food source, caterpillars

CaterpillarFeces

Fluid feeders: suck nutrient-rich fluid from living host (have specialized organs)

Bulk feeders: Eat large pieces of food.

Four main stages of nutrition: Ingestion: act of eating Digestion: food is broken down into small

molecules that can be absorbed; mechanical & chemical – enzymatic hydrolysis)

Absorption: animal cells take up the break-down products

Elimination: passing out undigested material

LE 41-12

Pieces of food

Chemical digestion(enzymatic hydrolysis)

Food

Nutrientmoleculesenter bodycells

Smallmolecules

Undigestedmaterial

ELIMINATIONABSORPTIONDIGESTIONINGESTION

Mechanicaldigestion

Intracellular digestion: food is broken down inside food vacuoles

Extracellular digestion: Breakdown happens in compartments that are outside of the body; hydra, earthworm, grasshopper, birds, humans

Gastrovascularcavity

Mouth

Food

Tentacles

Epidermis

GastrodermisMesoglea

Gland cells

Flagella

Nutritivemuscularcells

Food vacuoles

Mesoglea

GizzardIntestine

Anus

CropEsophagus

Pharynx

Mouth

Earthworm

Typhlosole

Lumen of intestine

Foregut Midgut Hindgut

Rectum

Anus

Esophagus

MouthCrop

Gastric cecaGrasshopper

Anus

Esophagus

Mouth

Crop

Bird

StomachGizzard

Intestine

Human digestive system

Esophagus

Stomach

Liver

Salivaryglands

Gall-bladder

Pancreas

Rectum

Anus

Largeintestines

Smallintestines

Mouth

A schematic diagram of thehuman digestive system

Peristalsis: alternating waves of contraction and relaxation in the smooth muscles lining the alimentary canal.

Oral cavity: Mechanical digestion, chewing. Chemical digestion: Saliva

Oral cavity,pharynx,esophagus

Smaller polysac-charides, maltose

Polysaccharides Disaccharides

Carbohydrate digestion

Salivary amylase

Protein digestion Nucleic acid digestion Fat digestion

Functions of saliva salivary amylase, hydrolyzes starch lubrication: mucin (glycoprotein) preparation of food bolus buffer antibacterial function

Swallowing has to be carefully choreographed to prevent food from entering airway

Stomach: stores food continues digestion by churning and mixing with

gastric juices (chyme). low pH (~2)kills bacteria, HCl secreted by parietal

cells digests protein – pepsin, chief cells produce

pepsinogen which is activated by HCl.

Esophagus

Cardiac orifice

Pyloric sphincter

Smallintestine Folds of

epithelialtissue

Stomach

Epithelium

Pepsin(active enzyme)

Pepsinogen

HCl

Pepsinogen and HClare secreted into the lumen of the stomach.

HCl convertspepsinogen to pepsin.

Pepsin then activatesmore pepsinogen,starting a chainreaction. Pepsinbegins the chemicaldigestion of proteins.

Parietal cellChief cell

Chief cells

Mucus cells

Parietal cells

Interior surface of stomach

Gastric gland

5 µ

m

Stomach secretes thick mucus to prevent its cells from getting corroded by HCl.

Sphincter (ring-like valve) at the junction of stomach and esophagus prevents backflow. Backflow causes “heartburn”.

Sphincter between stomach and small intestine allows food to go out in squirts.

Takes 2 to 6 hrs after a meal for the stomach to empty.

Figure 22.10

Oral cavity,pharynx,esophagus

Stomach

Smaller polysac-charides, maltose

Polysaccharides Disaccharides

Carbohydrate digestion

Salivary amylase

Protein digestion Nucleic acid digestion

Proteins

Fat digestion

Small polypeptides

Pepsin

Bacteria

Mucuslayer ofstomach

1 µ

m

Small intestine: very long, small in diameter; three sections

duodenum jejunum ileum

Duodenum: Chyme mixes with

digestive juices from Liver and gall bladder Pancreas Intestinal wall

Bulk of digestion happens here Continues in the jejunum and ileum Bile salts produced by liver helps in the

digestion of fats

Pancreas

Lumen of duodenum

Membrane-boundenteropeptidase

Inactivetrypsinogen

Other inactiveproteases Active

proteases

Trypsin

Oral cavity,pharynx,esophagus

Stomach

Lumen ofsmall intes-tine

Smaller polysac-charides, maltose

Polysaccharides Disaccharides

Carbohydrate digestion

Salivary amylase

Polysaccharides

Pancreatic amylases

Maltose and otherdisaccharides

Epitheliumof smallintestine(brushborder)

Disaccharidases

Monosaccharides

Protein digestion Nucleic acid digestion

Proteins

Fat digestion

Fat globulesDNA, RNA

Fat dropletsNucleotides

Bile salts

Pancreatic lipase

Pancreaticnucleases

Nucleotidases

Glycerol, fattyacids, glycerides

Nitrogenous bases,sugars, phosphates

Nucleosides

Nucleosidasesand phosphatases

Dipeptidases, carboxy-peptidase, and aminopeptidase

Amino acids

Amino acids

Small peptides

Pancreatic carboxypeptidase

Pancreatic trypsinand chymotrypsin

Smaller polypeptides

Polypeptides

Small polypeptides

Pepsin

Absorption in small intestine Huge surface area – villi (finger like folds) Microvilli: folds on the surface of the epithelial

cells

Figure 22.15b

Nutrients convert to water-soluble chylomicron, transported through lacteal, goes to the lymph system and to the blood and heart.

Absorbed nutrients also reach the liver through hepatic portal vein; nutrient distribution is controlled by the liver, detoxification.

Large intestine: consists of Cecum Ascending, transverse and descending colon Rectum

In humans cecum is much reduced appendix – finger-like extension

90% of the water from the alimentary canal is absorbed here

Feces: undigested food material Escherichia coli: breaks down some of the

unabsorbed food material

Form fits function: Dental adaptations Stomach and intestinal adaptations Mutaualistic adaptations Coprophagous habits

Incisors

Carnivore

CaninesPremolars

Molars

Herbivore

Omnivore

Dental adaptations

Smallintestine

Stomach

Cecum

Colon(largeintestine)

Carnivore Herbivore

Small intestine

Stomach and intestinal adaptations

LE 41-28

Intestine Rumen

Reticulum

Omasum

EsophagusAbomasum

Mutaualistic adaptations

Coprophagous habits: rabbits and rodents eat their feces to extract all the nutrients

Homeostatic regulation of cellular fuel

STIMULUS:Blood glucose

level risesafter eating.

STIMULUS:Blood glucose

level dropsbelow set point.

Homeostasis:90 mg glucose/100 mL blood

Overnourishment: Consumption of more food than needed

Obesity – connected to cancer, heart disease and diabetes

Recent research: ob gene connected to obesity in mice

Fat and sugar cravings – evolutionary sense?