6.1 Digestion and Absorption Flashcards
How does the body convert into nutrients?
Through the digestive system that consists of digestion and absorption.
What happens during digestion?
- “break down” of food into monomers of nutrient, ie. glucose, amino acid, fatty acid, nucleic acid. - Digestion or break down is by mechanical digestion (chewing) or by various enzymes
What is absorption in the body?
- “suck in” nutrients. - This happens in the intestine.
Draw and annotate a diagram of the digestive system (name & functions)
○ Mouth ○ Esophagus ○ Stomach ○ Small intestine ○ Large intestine ○ Pancreas ○ Liver ○ Gall bladder
What is the function of the mouth?
Mouth: physical digestion takes place as the teeth cut and grind food into small pieces. The tongue helps to mix the food with saliva which is released by salivary glands. Saliva contains salivary amylase, an enzyme which begins the process of chemical digestion. Salivary amylase breaks down starch into maltose
What is the function of the esophagus?
Esophagus: muscular tube which carries foods and liquids from the throat to the stomach. Food is pushed along the esophagus by a wave of muscular contractions. This type of muscle movement is called peristalsis.
What is the function of the stomach?
Churning and mixing with secreted water and acid which kills foreign bacteria and other pathogens in food, plus initial stages of protein digestion
What is function of small intestine?
final stages of digestion of lipids, carbohydrates, proteins, and nucleic acids, neutralizing stomach acid, plus absorption of nutrients
What is the function of the liver?
produces a liquid called bile. Bile contains emulsifying agent which helps to dissolve fats/ lipids in water.
Liver is also a place to store glycogen (see more in starch digestion)
What is the function of the gallbladder?
Stores bile until it is needed
What is is the function of a pancreas?
Produces pancreatic juice (bunch of enzymes) which contains pancreatic amylase, lipase and protease. Pancreatic juice is squirted into lumen of the small intestine as soon as food leaves the stomach
What is the function of the large intestine?
Re-absorption of water, further digestion especially of carbohydrates by symbiotic bacteria, plus formation and storage of feces.(Minerals & Vitamins absorbed)
How does the main tract in digestion work?
The main tract consist of mouth, esophagus, stomach, small and large intestine. The liver makes bile, bile is stored in gall bladder, gall bladder then connect to deliver bile to the small intestine. The pancreas is also connected to the small intestine. (Draw diagram if necessary)
What is peristalsis?
The contraction of circular and longitudinal muscle layers of the small intestine mixes the food with enzymes and moves it along the gut (type of movement)
Describe the structure of the small intestine.
The wall of the small intestine is made of layers of living tissues:
- Serosa: an outer coat
- Muscle layers: longitudinal muscle
- sub-mucosa: a tissue layer containing blood and lymph vessels
- mucosa: the lining of the small intestine, with the epithelium that absorbs nutrients on its inner surface (Draw Diagram)
How does peristalsis work?
The circular/longitudinal muscle is a smooth muscle and consists of short cells (not elongated fibres). -exerts continues moderate force interspersed with short periods of more vigorous contraction (one direction) -contraction of circular muscles behind the food constricts the gut prevent it from being pushed back -contraction of longitudinal muscle where food is located moves it along the gut.
How is peristalsis controlled?
-controlled unconsciously not by brain but by enteric nervous system (extensive and complex)
What muscle is used during vomiting?
abdominal muscles
What does pancreatic juice do?
There are two types of gland tissue where one group of cells secretes hormones (insulin&glucagon). The rest synthesizes digestive enzymes
Where are digestive enzymes synthesized in a cell?
They are proteins and thus synthesized on ribosomes in the RER
With the enzymes in the pancreatic juice, what can it breakdown?
-Amylase to digest starch -Lipases to digest lipids (triglyceride/phospholipids) -Proteases to digest proteins/peptides
Which reactions does the small intestine carry out?
Hydrolysis reactions: - starch is digested to maltose by amylase - tryglycerides are digested to fatty acids and glycerol by lipase - phospholipds are digested to fatty acids and glycerol/phosphate by phospholipase - proteins and polypeptides are digested to shorter peptides by protease This does NOT allow small enough molecules to be absorbed.
What enzymes are present in the plasma membrane of the epithelium cells (lining the small intestine)?
- Nucleases - Maltase - Lactase - Sucrase - Exopeptidases - Dipeptidases
What does exopeptidases breakdown?
These are protesases that digest peptides by removing single amino acids either from the carboxy or amino terminal of the chain until only a dipeptide is left
