Lecture 19 Digestive System Flashcards
DIGEST THIS IN YOUR BODY
What are the organs of the GI tract?
-Oral cavity
- Pharynx
- Esophagus
- Stomach
- Small intestine
- Large intestine
What are the accessory organs of the GI tract?
- Teeth
- Tongue
- Salivary glands
- Liver
- Gallbladder
- Pancreas
What are the five functions of digestion?
- Motility
- Digestion
- Secretion
- Absorption
- Storage and Elimination
How does motility work?
- Ingestion: taking food into oral cavity
- Deglutition: swallowing food (tongue and pharynx)
- Peristalsis: rhythmic wave-like muscular contractions that move food throughout GI tract starting with esophagus
Explain mechanical digestion
Breaking down food particles into smaller pieces
- Mastication: chewing food, mixing with saliva and binding food into a solid mass known as bolus (oral cavity, salivary glands, teeth, tongue)
- Churning: muscular contraction of stomach turns bolus into chyme
- Segmentation: muscular contraction of small intestine mixes food further
Explain chemical digestion
Chemically breaks down macromolecules of food by hydrolysis into molecular monomers.
Enzymes required
Mostly occurs in small intestine (but some can begin in oral cavity and stomach)
Secretion includes release of exocrine and endocrine products into the GI tract that help with digestion processes.
What are some exocrine and endocrine secretion examples?
- Exocrine: HCl, H2O, HCO3- (bicarbonate), bile, mucus, digestive enzymes (lipase, pepsin, amylase, trypsin, elastase
- Endocrine: Hormones secreted into stomach and small intestine to help regulate GI system (eg. Gastrin, secretin, CCK, GIP, GLP-1, guanylin, VIP and somatostatin)
Explain absorption
Eventual passage of monomers into blood or lymph which are then used by cells to either make ATP or additional tissue by building macromolecules
Food molecules absorbed mostly at small intestine.
Water molecules and electrolytes absorbed mostly at large intestine
Explain storage and elimination
Temporary storage of food and waste through stomach & large intestine and subsequent elimination/ defecation of indigestible components of food (large intestine)
What is required to break polymers into monomers?
Where are the majority of these secreted? In active or inactive form?
- Enzymes
- Secreted by the pancreas in inactive form
What are enzymes and what do they do?
A class of proteins that serve as biological catalysts
- Increase the rate of reaction
- Changed by the reaction so they can be used again
- Do not change nature of reaction, only speed it up
- Lowers activation energy of the reaction (A.E is the energy required for the reactants to engage in a reaction)
What is enzyme activity and what is it influenced by?
- The rate at which substrates re converted to products
Influenced by:
- Temperature
- pH
- Concentration of enzyme and substrate
What is the effect of temperature on enzymes?
Increase in temp will increase rate of reaction until temp reaches a few degrees above body temp (37 degrees C)
Enzyme would then become denatured
What is the effect of pH on enzymes?
Enzymes exhibit peak activity within a narrow pH range called the pH optimum (usually 7 for most enzymes)
pH changes will result in enzyme conformational changes and can lead to denaturation
What is the effect of substrate concentrations on enzymes?
Rate of reaction will increase if substrate concentration increases (until enzyme becomes saturated)
(saturated means every enzyme in solution is being used) (will basically plateau)
