Review set 5 Flashcards
Why is digestion critical?
large food molecules is essential
*Most food large/ complex – not readily usable (must be broken down for absorption and for reassembly into new products); Contains certain substances not suitable for human tissue (must be separated/ removed)
Explain the need for enzymes in digestion.
Enzymes = biological catalysts; allow breakdown of specific substrates in organism-specific temperatures/ pH/ etc.; substrates broken down independently of others
- Hydrolysis (hydro = water, lysis = breaking) reactions (catabolic reactions) dominate the digestive process
- Enzymes are globular proteins that lower the activation energy needed to start a chemical reaction and speed up the rate of chemical reactions (allow reactions to occur more quickly at body temperature/ increase rate of digestion)
- Digestive enzymes released into gut from exocrine glands (pancreas) - exocrine glands have ducts and secrete substances to an epithelial surface
- Enzymes break large, insoluble molecules into smaller, soluble molecules (monomers) that are easily absorbed into the bloodstream
Define enzymes
biological catalysts; allow breakdown of specific substrates in organism-specific temperatures/ pH/ etc.; substrates broken down independently of others
Draw the digestive system
Stomach should be ‘J’-shaped and be connected to the esophagus and small intestine Liver should look like a right-angled triangle and be superimposed to the left of the stomach (right side of the human) Bile duct (connected to gall bladder) and pancreatic duct should both feed into a U-shaped bend of the small intestine Small intestine should be thinner in width than the large intestine
Enzyme: Salivary amylase
State: Site of production,Site of Action, pH, Substrate(s), Product(s)/
Site of production: Salivary glands Site of action: Mouth/ Esophagus ph: Neutral (7) Substrate: Starch (amylose) Product: Maltose
Enzyme: Pepsin/ protease
State: Site of production,Site of Action, pH, Substrate(s), Product(s)/
Stomach Stomach Acidic (1-2) Proteins Peptides
Enzyme: Amylase
State: Site of production,Site of Action, pH, Substrate(s), Product(s)/
Pancreas Lumen of small intestine Neutral to slightly alkaline (7-8) Starch Maltose
Enzyme: Lipase
State: Site of production,Site of Action, pH, Substrate(s), Product(s)/
peter loves nicotine too much
Pancreas Lumen of small intestine Neutral to slightly alkaline (7-8) Triglycerides Monoglycerides/ fatty acids/ glycerol
Enzyme: Endopeptidase/ Protease
State: Site of production,Site of Action, pH, Substrate(s), Product(s)/
Pancreas Lumen of small intestine Neutral to slightly alkaline (7-8) Proteins/ peptides Amino acids
Enzyme: Nuclease
State: Site of production,Site of Action, pH, Substrate(s), Product(s)/
Pancreas Lumen of small intestine Neutral to slightly alkaline (7-8) Nucleic acids Nucleosides
Carbohydrates process of being digested
—>
Once carbohydrates are hydrolyzed to disaccharides, they are then hydrolyzed to monosaccharides by enzymes that are immobilized (such as maltase) on the epithelial lining of the small intestine
Lipids process of digesting
Lipids are first emulsified (broken down into physically smaller droplets) by bile (released into the small intestine from the gall bladder) and then hydrolyzed by lipases (secreted into the small intestine from the pancreas) into monoglycerides, fatty acids, and glycerol. They are then absorbed by the epithelial cells of the small intestine and transported (as chylomicrons) to the lacteal.
Alimentary canal is divided into
Stomach, Small Intestine, and Large Intestine
Stomach’s function
Protein (chemical) digestion (begins – acidic pH denatures and proteases break down); begins mechanical digestion (breaking food into smaller parts without breaking bonds); mixes food to promote digestion (churning); produces chyme
Small intestine
Completes digestion of food molecules; absorption of nutrients/ water; receives secretions from pancreas/ gall bladder to aid in digestion; mixing/ movement of digested food products (peristalsis); secretion of intestinal juices; contains villi (increase surface area for absorption)
Large Intestine
Absorption of water/ minerals/ ions; produces/ stores/ eliminates feces (solid waste/ cellulose/ lignin)
What are not broken down by humans and why?
Cellulose and lignin are NOT broken down because humans lack enzymes to break down beta-glucose (the linkages found in cellulose and lignin) - important in diet though = “fiber” to clean out old cells/ bacteria and “work out” natural microflora
Structures of Villus
Microvilli, Rich capillary network, Single epithelial layer, Lacteals, Intestinal crypts (between villi), Membrane proteins/ mitochondria
Microvilli
increase surface area for absorption and contain immobilized enzymes (maltase etc.) for hydrolysis of disaccharides (maltose hydrolyzed to glucose)
Rich capillary network
minimize diffusion distance and maintain large concentration gradient for rapid absorption
Single epithelial layer
Minimal diffusion distance (cells connected by TIGHT JUNCTIONS - impermeable barrier/ ensure one-way flow of nutrients and ensuring separation of body and digestive fluids
Lacteals
Absorb lipids into lymphatic system
Intestinal crypts (between villi)
release juices that act as carrier fluids for nutrients
Membrane proteins/ mitochondria
Active transport
Structure of the Small intestine from outside to inside
Serosa Longitudinal muscles Circular muscles Submucosa Mucosa
Serosa
Protective outer covering
Longitudinal muscles
Peristalsis (move food along gut/ mix with enzymes)
Circular muscles
Segmentation (prevent backward movement of food/ mix with enzymes)
Submucosa
Separates innermost mucosa from muscles
Mucosa
Highly folded inner epithelial layer (villi and microvilli) to increase the surface area for absorption of monomers from the intestinal lumen
the Different methods of membrane transport are required to absorb different nutrients
Diffusion Osmosis Facilitated Diffusion Active Transport - requires ATP Endocytosis
Diffusion
Fatty acids and other small, non-polar substances easily pass through the hydrophobic cell membranes of epithelial cells through simple diffusion
Osmosis
Water diffuses across epithelial cell membranes in response to movement of ions and other hydrophilic monomers (occurs in small intestine and large intestine)
Facilitated Diffusion
Protein channels within epithelial cell membranes (of villi and microvilli) allow passage of hydrophilic food molecules (water-soluble/ polar molecules like fructose, vitamins, glucose, amino acids, and minerals)