Digestion & Absorption Flashcards
Outline the role of the main components of the digestive system.
Mouth: 1)Contains teeth that breaks food down into smaller chunks, allowing easier movement down the GI tract.
2) Enzymes that chemically break down the food.
Oesophagus: tube connecting mouth and stomach. Peristalsis i.e. Wave-like movement that moves food downwards.
Stomach: strong HCl chemically break down food.
Small intestine: where most of CHO and lipid digestion takes place.
Large intestine: everything that are not thoroughly digested goes here. Mainly for water re-absorption too. (Diarrhea because insufficient time to stay in LI, so watery poo.
Pancreas: secretes enzymes such as pancreatic amylase and lipases helping with digestion of lipids and carbohydrates.
Gallbladder: liver produces bile from cholesterol and it is stored here. Used as an emulsifier to make fats water soluble.
Describe the digestion of carbohydrates?
See YouTube video.
https://www.youtube.com/watch?v=LWfXeCVp7Wk
Summary: mouth contains amylase that breaks starch into smaller polysaccharides and disaccharides. Stomach stops amylase action, no further action happens here. Small intestine does most of the job i.e. Pancreatic amylase (alpha amylase) breaks polysaccharides into monosaccharides. They diffuse across the capillary wall and go to the liver via the portal vein. Liver converts all into glucose. If blood glucose is low, then glucagon hormone is released to allow glucose to enter and circulate in the blood. If it is high, insulin released to store glucose as glycogen in liver. Around 2/3 stored in liver, and 1/3 in skeletal muscles.
Describe the digestion of lipids?
Refer to YouTube video: https://www.youtube.com/watch?v=i0kHf_5s3J8
Summary: mouth releases lipase for chemical breakdown. Stomach has no effect. While in lumen of small intestine, hormone CCK stimulates release of bile from gallbladder, which emulsifies the lipid, then the pancreatic lipases breakdown the TG into glycerol and 3 fatty acids. These enter they small intestine. Reassembly into TG by surrounding them with lipoproteins to form chylomicrons.
These enter the lymphatic system then drains into the blood near the heart.
For storage: goes into adipose tissue by lipoprotein lipase that breaks them down again. Stored as TG again.
For release into the blood:by hormone sensitive lipase. Broken down again, FFA binds with albumin. Forms NEFA. Goes into mitochondria forms atp by beta oxidation.
What are ketone bodies? How are they produced?
Ketone bodies are substances produced by the liver when fat breakdown is rapid without the presence of carbohydrate. I.e. Acetyl-coA is produced by fat breakdown, too much means they do not go into b-oxidation. So they are converted into ketone bodies.
What organs use ketone bodies for energy sources?
All non-liver organs, including brains and muscles.
What are some of the issues associated with excessive production of ketone bodies?
Excessive ketone bodies are often excreted through urine and breath. Abnormalities include:
1) ketonemia: increased ketone in blood.
2) ketonuria: increased ketone in urine.
3) ketoacidosis: they are acidic, so blood turns too acidic. Can be fatal.
4) Acetone breath: metallic smelling breath.
Major minerals? Trace minerals? Ultra-trace?
Major minerals:
Calcium, pottasium, iron, magnesium and sodium.
Trace minerals:
Copper, zinc, iodine, selenium, selenium and fluoride.
Ultra-trace:
The strange ones.
