Digestive System Flashcards
What is digestion?
The breakdown of larger food molecules into smaller molecules.
What are the two types of digestion?
- Mechanical Digestion
- Chemical Digestion
What is mechanical digestion?
The physical breakdown of larger food molecules into smaller molecules.
What is the purpose of mechanical digestion?
To increase the surface area of the food mass.
What are some examples of mechanical digestion?
Chewing with the teeth
Churning with the stomach
What is chemical digestion?
The chemical breakdown of larger food molecules into smaller molecules.
(Catabolism)
What are some examples of chemical digestion?
Saliva in the mouth
Hydrochloric Acid in the stomach
What type of digestion occurs in the mouth?
Mechanical (Teeth)
and
Chemical (Saliva).
How does saliva chemically digest foods?
Through the usage of:
* Salivary Amylase (enzyme)
* Mucous (moisten foods)
* Buffers
* Antibacterial Chemicals
What is a bolus?
A ball of chewed food.
What is the function of salivary amylase in the mouth?
To break down starch.
What is the epiglottis?
A flap of carilage that closes the trachea (windpipe) when swallowing.
Define peristalsis.
Involuntary muscle contractions that move food along.
What are the layers of the GI tract?
(In order from inner to outermost)
- Mucosa
- Submucosa
- Double layer of muscle (Longitudinal, Circular)
- Serosa
What is the oesophagus?
A muscular tube that connects the mouth to the stomach.
What is the main function of the stomach?
To store and break up food.
What type of digestion occurs in the stomach?
Mechanical (Churning)
and
Chemical (Hydrochloric acid & Pepsin).
What is the pH of Hydrochloric Acid? (HCl)
~2-3
What enzyme does the stomach produce?
Pepsin.
Why would pepsin only survive in the stomach?
Pepsin requires a very acidic (low pH) environment.
What is a protease?
A protein-digesting enzyme.
How does mechanical digestion in the stomach occur?
Waves of movement are made along the stomach wall.
What allows the stomach wall to move?
The stomach’s third layer of muscle
(Oblique muscle)
What does the stomach turn food into?
A thick, soupy liquid called chyme.
*ulcers
What is the function of a buffer?
To neutralise acid from the stomach.
What is the function of the pancreas?
To produce and secrete pancreatic juice into the small intestine.
Which enzymes are present in pancreatic juices?
- Proteases — Trypsin, Chymotrypsin
- Amylase
- Lipase
Define gluconeogenesis.
The conversion of amino acids to glucose.
List 3 functions of the liver.
- Gluconeogenesis
- Metabolises fat (produces lipids from excess glucose)
- Detoxification (eg metabolising alcohol)
What is deamination?
The removal of excess amino acids from the body.
What happens in the process of deamination?
- The amine group (NH₂) is removed from the amino acid ()
- The amine group is converted to ammonia (NH₃)
- The ammonia is combined with CO₂ using ATP to produce urea CO(NH₂ )₂
Why is it important that ammonia is quickly converted to urea in deamination?
Because it’s very soluble and toxic.
What is bile?
A thick liquid that’s produced by the liver to help digest fat.
What is the function of the gallbladder?
To store bile produced by the liver.
How does the small intestine maintain a large surface area while taking such a small amount of space?
- Length
- Folds
- Villi & Microvilli
How does the small intestine mechanically digest food?
- Peristalsis
- Bile (emulsion)
How does the small intestine chemically digest food?
Pancreatic and Intestinal juices.
(Both containing enzymes)
What are villi?
Small finger-like projections
What is the function of villi?
To increase surface area for absorption.
How are monosaccharides absorbed?
Active transport into blood capillaries.
How are amino acids absorbed?
Active transport into blood capillaries.
How are fatty acids and glycerol absorbed?
Simple diffusion into the villi cells, which coat them in protein.
How are fat-soluble vitamins absorbed?
Using fatty acids and glycerol.
How are water-soluble vitamins absorbed?
Simple diffusion, into blood capillaries.
How is water absorbed?
Into villi cells, via osmosis.
What is the function of the large intestine?
- Water absorption
- Break down remaining organic molecules (which produces gases.)
What is another name for the large intestine?
The colon.
What percentage of water used in digestion is reabsorbed by the large intestine?
~90%.
How does the large intestine reabsorb water?
Via osmosis.
The large intestine has bacteria that helps digest remaining food molecules. What do they generate during this digestion?
Gases
(Methane, Hydrogen sulfide)
