Topic 6.1: The Digestive System Flashcards
Organs of the digestive system (8)
Mouth Esophagus Stomach Liver Gall bladder Pancreas Small Intestine Large Intestine
Mouth
a) Chewing (Mechanical digestion)
b) Moistening of food to make a bolus for swallowing
c) Digestion of starch by amylase
Esophagus
Pushing bolus into the stomach via peristalsis
Stomach
a) Churning and mixing of bolus with acid by muscular contractions
b) Protein digestion by pepsin
Small intestine
a) Neutralization of acid and emulsification of fats by bile from the gale bladder.
b) Digestion of proteins, carbohydrates and fats
c) Absorption of nutrients from chime into the blood via the villi
Large intestine
Absorption of water and dissolved minerals
Pancreas
Secretion of lipase, amylase and protease
Liver
Production of bile
Gall bladder
Storage and regulated release of bile
Definition of digestion
Breaking complex macromolecules into simpler ones
Reasons for digestion (2)
a) Large molecules are chemically inert and need to be broken down and reassembled into usable products
b) Large molecules are insoluble and cannot be easily absorbed into cells compared to smaller subunits.
Types of digestion (2)
a) Mechanical
b) Chemical
Mechanical digestion (3)
a) Chewing - Grinding food using teeth
b) Churning - Squeezing stomach contents
c) Segmentation - Intestinal contractions
Chemical digestion (3)
a) Stomach acids - Denaturation of proteins (low pH)
b) Bile - Emulsification of fats into droplets
c) Enzymes - Catalyze hydrolysis reactions
Peristalsis
a) Unidirectional movement of food along alimentary canal
b) Caused by contraction of sequential longitudinal muscles
Segmentation
a) Bidirectional mixing of food within the small intestine
b) Caused by contraction of non-sequential circular muscles.
Role of enzymes during digestion
Digestive enzymes are released from the pancreas into the gut and are used in catabolic reactions
Amylase
a) Substrate
b) Product
c) Source
d) Optimum pH
a) Starch
b) Maltose
c) Salivary glands / Pancreas
d) 7
Pepsin / Endopeptidase
a) Substrate
b) Product
c) Source
d) Optimum pH
a) Polypeptides
b) Amino acids
c) Stomach / Pancreas
d) 2 / 7
Lipase
a) Substrate
b) Product
c) Source
d) Optimum pH
a) Triglycerides
b) Fatty acids / glycerol
c) Pancreas
d) 7
Process of starch digestion
a) Starch is digested by amylase secreted in the mouth and the pancreas
b) Amylose and amylopectin are broken down into maltose and dextrin respectively
c) Maltase immobilized on the epithelial lining of the small intestine breaks down maltose and dextrin into glucose
d) Pancreas secretes insulin and glucagon to regulate the concentration of glucose in the bloodstream
Absorption
Movement of fluids or dissolved substances across a cellular membrane
Assimilation
Components become part of an organism
Small intestine structure
a) Serosa
b) Longitudinal muscle
c) Circular muscle
d) Mucosa
Villi definition
Finger-like mucosal projections that increase SA of epithelium over which absorption is carried out
Features that allow for increased SA: Vol absorption
a) Microvilli
b) Rich blood supply
c) Single layer epithelium
d) Lacteals
e) Intestine crypts
f) Membrane proteins
Membrane transport mechanisms
a) Simple diffusion
b) Facilitated diffusion
c) Protein pumps
d) Endocytosis
e) Osmosis
Nutrients
a) Simple diffusion
b) Facilitated diffusion
c) Protein pumps
d) Endocytosis
e) Osmosis
a) Fatty acids
b) Monosaccharides / Vitamins / Minerals
c) Larger molecules
d) Water / Dissolved ions
Modelling absorption using dialysis tubing
a) Large molecules cannot cross
b) Small molecules can cross
