CH. 11 - Digestion

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Keywords

1. General

1. Digestion - degradation of larger molecules into smaller molecules that can be absorbed

2. Extracellular digestion - digestive process outside of cell, within lumen or tract

3. Heterotrophic - organisms unable to synthesize their own nutrients

4. Intracellular digestion - occurs in cell in membrane-bound vesicles

2. Digestion in Unicellular Organisms

1. Cytopharynx - oral groove where food particles are swept into by cilia

2. Lysosome - principal digestive organelle with digestive enzyme

3. Phagocytosis - enveloping of food particles via pseudopods

3. Digestion in Invertebrates

1. Crop - food storage in annelids

2. Gizzard - grind food down in annelids

3. Typholosole - a large dorsal fold to increase surface area for digestion and absorption in annelids

4. Digestion in Humans

1. Aminopeptidase - polypeptide digestion

2. Amylase - digests carbohydrate, produced in pancrea and mouth

3. Bile - produced in liver, emulsifies fat

4. Bolus - soft mass of chewed food within mouth

5. Chyme - partially digested food in stomach that's semi-fluid and acidic

6. Disaccharidases - digestion of maltose, lactose, sucrose

7. Emulsify - to break down large globules into small droplets

8. Gall Bladder - stores bile

9. Lactase - breaks down lactose (milk sugar)

10. Lacteals - vessels of lymphatic system, in the villi to absorb fatty acids and glycerol

11. Large Intestine - 1.5 meter long that absorbs salt and water

12. Lipases - digests fat, enzyme produced in pancreas

13. Liver - produces the bile that's stored in gall bladder, location of initial food processing

14. Mastication - chewing and biting of teeth

15. Pancreas - produces digestive enzymes and also secretes bicarbonate juice to neutralize the incoming acidic chyme

16. Pancretic amylase - break down starch to maltose

17. Pepsin - protein hydrolyzing enzyme in the stomach

18. Peristalsis - the muscular contractions of esophagus that moves food down

19. Pyloric sphincter - chyme passes through here to the small intestine

20. Rectum - temporary storage for feces

21. Salivary amylase - enzyme in saliva that breaks down starch to maltose

22. Small Intestine - break down into the duodenum, jejunum, and ileum

23. Trypsin - protein digestion enzyme produced in pancreas

24. Villi - finger-like extensions in small intestine that contain capillaries and lacteals for nutrient absorption

5. Digestion in Plants and Fungi

1. Saprophyte - lives on dead organic material

2. Starch - storage form of plant, polymer of glucose.  Found in stem, root, seed

Digestion in Unicellular Organisms

1. General

1. Amoeba

1. By utilizing phagocytosis

1. Pseudopods surround and engulf food, enclosing it in vacuole

2. Lysosomes fuse with the food vacuole and digestive enzyme released

1. Simpler molecule diffuse into cytoplasm and utilized

2. Unusable stuff eliminated

2. Paramecium

1. By utilizing cilia, food is sweeped into a mouth-like opening

1. Oral groove and cytopharynx

1. Food vacuole is formed around the inner part of cytopharynx

2. Vacuole breaks off and goes off into cytoplasm

3. Enzymes secreted into vacuole (lysosome?), and products diffuse into cytoplasm

4. Solid wastes expelled at anal pore

Digestion in Invertebrates

1. General

1. Two phases, physical breakdown and chemical breakdown

1. Physical breakdown - chewing, cutting, grinding food into smaller pieces

1. Done in digestive tract, and mouth

2. To increase the surface area that the digestive enzyme can act upon

2. Chemical breakdown - enzyme hydrolysis

1. Breaks down the food particle down further into useful molecules

3. Digested nutrients passes through semi-permeable plasma membrane of the gut cells to be transported.

2. Cnidarians

1. Utilizes both intracellular and extracellular digestion

2. Tentacles bring food to mouth, and it's chewed up slightly here

3. Food particles are then released into a cup-like sac and digestive enzymes in this gastrovascular cavity and food is broken up further

4. Once food is sufficiently broken up, the gastrodermal cells engulfs the nutrients

1. The digestion now continues intracellularly

5. Wastes are ejected throught he mouth

3. Annelids

1. Functions similar to higher life forms

1. One way digestive tract with both mouth and anus

2. Food pathway

1. Mouth > Pharynx > Esophagus > crop > gizzard > intestine > anus

2. Soluble food passes by diffusion through the walls of small intestine

4. Arthropods

1. Digestive pathway similar to annelids

2. Also have a jaw for chewing and salivary gland for improved food digestion

Digestion in Humans

1. General

1. Digestion pathway

1. Oral cavity > pharynx > esophagus > stomach > small intestine > large intestine > anus

2. Accessory organs that play a role

1. Salivary glands, pancreas, liver, gall bladder

2. The Oral Cavity

1. Where the mechanical and chemical digestion begins

2. Mechanical digestion

1. Also called mastication

3. Chemical breakdown

1. Salivary gland's saliva

1. Contains enzyme salivary amylase (ptyalin)

1. Hydrolyzes starch to maltose

2. Lubricates food to facilitate swallowing

3. Solvent for food particles

4. Secreted in response to nervous reflect triggered by food in oral cavity

4. The lubricated soft mass of chewed food is called bolus

3. The Esophagus

1. Muscular tube leading from mouth to stomach

2. Food moved down via involuntary muscular contractions called peristalsis

4. The Stomach

1. Large muscular organ in the upper abdomen

1. Stores and partially digests food

2. Lined by thick gastric mucosa

1. Secretes mucus that protects stomach lining from acidic juices in stomach

2. Secrets pepsin

1. Protein hydrolyzing enzyme

3. Secrets hydrochloric acid

1. Kills bacteria

2. Dissolves intercellular "glue" that holds food tissues together

3. Activates certain proteins

3. The churning of stomach produces an acidic, semi-fluid mixture of partially digested food called chyme

4. Chyme goes into first part small intestine called duodenum through the pyloric sphincter

5. Small Intestine

1. Chemical digestion completed here

2. Divided into three parts: duodenum, jejunum, and ileum

3. Highly adapted to absorption

4. Extremely long, 6 meters long, highly coiled

5. Numerous finger-like projection called villi extend out of the intestinal wall

1. Contains capillaries and lacteals

2. Amino acids and monosaccharides are picked up here through capillary system

3. Fatty acid and glycerol goes into lacteals and re-converted into fats

6. Some nutrients are actively absorbed (requires energy)

1. Amino acids and glucose

7. Some nutrients are passively absorbed

8. Duodenum

1. Most digestion occurs here

2. Secretions of intestinal glands, pancreas, liver, and gall bladder mix together with the chyme for further digestion

3. Intestinal mucosa secretes

1. Lipases - fat digestion

2. Aminopeptidases - polypeptide digestion

3. Disaccharidases - digestion of maltose, lactose, and sucrose

1. Lactase - breaks down lactose (milk sugar)

1. Present in infants

2. Adults lack it, thus lactose intolerant.  Bacteria uses it and causes internal discomfort

6. The Liver

1. Produces bile that's stored in gall bladder

2. Bile

1. Contains no enzyme

2. Emulsifies fat from large globules into small droplets

1. Allows pancreatic lipase to act on it better

3. Without bile, fat cannot be digested

3. Nutrients from intestines are transported here first for initial processing

7. The Pancreas

1. Produces enzymes

1. Amylase - carbohydrate digestion

2. Trypsin - protein digestion

3. Lipase - fat digestion

2. Also secretes bicarbonate rich juice that neutralizes the acidic chyme

1. The enzymes need to work in higher pH unlike pepsin

8. The Large Intestine

1. Approximately 1.5 meter long

2. Functions in the absorption of salts and water not already absorbed in small intesting

3. Rectum is a transient storage of feces prior to elimination through anus

Digestion in Plants and Fungi

1. Intracellular Digestion

1. Plants store insoluble polymers, starches, lipids, and proteins in the cells

2. Principal storage form is starch (glucose polysaccharide)

3. When nutrients are required, starch is broken down by enzyme hydrolysis

2. Extracellular digestion

1. Fungi excretes enzymes into the environment, and absorbs the simpler molecules

1. Rhizoid

1. Type of bread mold, typical saprophyte

2. Secretes enzyme onto the environment (bread)

3. Digestion produces simple soluble en-product which are absorbed via diffusion

2. Venus Flytrap

1. When fly arrives, certain tissue triggered would spring the trap and enclose the insect

2. Enzymes secreted to digest the fly and absorb the soluble end product

3. Still autotroph because it photosynthesize to produce glucose

Requires the insect as nitrate source so it can thrive on nitrogen poor soil