Nutrient Digestion II (Fats, Vitamins and Minerals) Flashcards
Where does all fat digestion occur and what enzyme does so?
Small Intestine
Lipase - Made in the pancreas
How do triacylglycerols present?
Large lipid droplets
What is special about the lipid droplet and lipase relationship?
Lipid droplets and insoluble in water but lipase is a water soluble enzyme so digestion only occurs at the droplet surface
What does lipase cleave triacylglycerols into?
Monoglyceride + Fatty Acids x2
What is emulsification?
The dividing of large lipid droplets into smaller droplets resulting in an increased surface area and accessibility to lipase action
How are droplets made smaller?
Mechanical disruption - Smooth muscle grinding and mixing luminal contents
How are smaller droplets prevented from reforming into largers ones?
Emulsifying agent (Comes from bile)
Biles salts and phospholipids emulsify smaller fat globules
Phospholipids are amphipathic so they repel other small lipid droplets
How is lipase digestion enhanced?
By the use of micelles
What are micelles?
Similar to emulsion droplets but much smaller
Bile salt + Monoglycerides + Fatty Acids + Phospholipids
What happens to micelles?
They are not absorbed but instead release small amounts of Fatty Acids and Monoglycerides to diffuse across the plasma membrane
When does the micelle destabilise?
When it enters the microclimate outside the cell
Triacylglycerol droplets coated with amphipathic protein are transported where, how and what happens to them there?
To Golgi Apparatus via vesicles from RER
Exocytosed into the ECF at the serosal membrane
What is a chylomicron?
Extracellular far droplet containing phospholipids, cholesterol and fat-soluble vitamins
A lipoprotein that is present in the blood after digested fat has been absorbed from the small intestine
Where do Chylomicrons go?
Into lacteals between endothelial cells
What can chylomicrons not pass through?
Tight junctions between capillaries to prevent fat entering the blood
What are the fat-soluble vitamins?
A, D, E & K
What are the water-soluble vitamins?
B, C & Folic acid - Either absorbed by passive diffusion or carrier-mediated transport
What is special about Vitamin B12?
It must bind to intrinsic factor in the stomach and travel to the ileum where a specific transport mechanism recognises the complex itself - not the B12
What does B12 have an affect on?
Red blood cell maturation - Can give functional anaemia
Why can a sign of gut specific deficiency be delayed?
There is 3 years worth of B12 in the liver
What effect can bowel resection have on B12?
B12 transport mechanism is removed and anaemia will ensue 3 years down the line
What is iron absorbed across into the blood?
Brush border membrane via DMT1 - 10% a day is ingested across the intestine into blood
What does DMT1 transport and where to?
Mainly Iron but also Lead and Cadmium into duodenal enterocytes
What are enterocytes?
Simple columnar epithelial cells found in the small intestine
What are iron ions incorporated into?
Ferritin
What happens to unbound iron?
Transported across the serosal membrane into the blood
What does iron in blood bind to?
Transferrin
What does transferrin do?
Stops iron becoming free radicals and transports it to the liver
How often does the small intestine lining renew itself?
Every 5 days
What is the regulator of iron stasis?
The gut
What does hyperaemia lead to?
Increased ferritin levels
More iron bound in enterocytes
What does anaemia lead to?
Decreased ferritin levels and more iron released into the blood
What three glands secrete saliva?
Parotid
Submandibular
Sublingual
What is the main component of saliva?
Water - 99% to soften, moisten and dilute particles
What are mucins and what is their function?
Mucus + Water
Lubricant function
Is amylase found in saliva?
Yes
What is a Lysozyme(Natural bacteria)?
Bacteriocidal that cleaves the polysaccharide component of the bacterial cell wall
Where does α-amylase come from?
Serous alveolus
What effect does the parasympathetic nervous system have on salivary secretion?
Creates a profuse watery salivna
*Cranial nerves VII (Facial) & IX (Glossopharyngeal)
What effect does the sympathetic nervous system have on salivary secretion?
Creates a small viscous amount of saliva that is high in protein
If separated a β-2 adrenoreceptor agonist will give you a high amylase content and a α-1 adrenoreceptor agonist will make the saliva gloopy
