Flashcards in Fat digestion and absorption in the small intestine Deck (19):
Why is it important to eat fats?
- major energy storage/fuel in the body|
- provide insulation/protection for our body
- carry fat soluble vitamins through the body
- some acids we cant make in the bod and have to ingest eg linoleic acid (essential fatty acids)
What is the structure of a triglyceride moelcule? and what are two other typed of lipids?
Consists of three fatty acids bound to a glycerol molecule.
Two other forms of lipids that are less common are phospholipids and steroids (eg cholesterol).
What food source are long chain fatty acids mainly found and where are short chain acids mainly found?
Long chain = in meat, fish and vegetable oils
Short chain = in dairy products
In terms of saturation level which fats are the best for us?
saturated (liquid at room temp)
polyunsaturated eg vegetable oils (flaxseed, sunflower)
monounsaturated eg olive oil and canola oil
In terms of saturation level which fats are the worst for us?
saturated fats (mostly solids at room temp) eg butter, lard, palm oil, coconut oil
How susceptible to oxidation are saturated and unsaturated fats and what does this mean in terms of their usage?
Saturated fats are less susceptible to oxidation and this gives them a longer shelf life.
Polyunsaturated and monounsaturated fats are much more readily spoiled.
What happens to unsaturated fats like olive oil when they are heated to high temperatures?
They are hydrogenated which turns their structure into more of a saturated fat and prevents them from oxidation. This has raised issues in the past in terms of vegetable oils being used in baking and cooking being unhealthy?
What is the most common sterol and what is the main source of it?
Cholesterol - it is in animal products (meat, eggs, fish, dairy) although we actually manufacture most of our cholesterol in our liver (very little is actually absorbed from the diet).
What effect does plant sterols have on the absorption of cholesterol?
Plant sterols eg flor proactvie interfere with cholesterol absorption. Hence why margarine is labelled as being able to lower blood cholesterol.
What are some of the main functions of cholesterol in the body?
- important for synthesis of hormones, bile acids and vit D
- structural component of cell membranes
What condition results as a builup of cholesterol on the artery wall?
What is the recommendation in terms of how much fat should make up our daily energy consumption and what type of fat should this be?
We should be consuming around 30% of our energy intake through fat (no more than 35%) of which less than 10% should be from saturated fats.
What was the problem with removing a lot of fat out of the diet in the 1990's?
As a lot of fat was taken out of food eg milk for example, lots of sugar was added to the low fat alternatives in order to make it still taste good and so although the aim was to reduce the risk of CVD, the increased sugar has lead to increased obesity which is a risk factor for CVD!
Describe the steps of fat digestion as they occur from starting to eat food to the food arriving in the small intestine.
1. As we think about food and start to eat it, linguinal lipase is released into the saliva and helps to initiative breakdown of the lipids as food is being chewed.
2. As the food enters the stomach, lipid lipase/ gastric lipase starts the digestion and contraction and churning of the stomach muscles starts to break the fat into smaller droplets.
3. As the fat droplets move into the small intestine, cholecystokinin (CKK) signals for the gall bladder to release bile and the pancreas to release digestive enzymes.
4. The bile emulsifies the fat (acts a detergent) that separates the fat droplets and breaks them down into smaller particles so pancreatic enzymes can act on them.
5. The pancreatic enzymes then break the fat particles down into smaller globules (glycerol, monoglycerides, fatty acids).
Describe how fat is absorbed into the enterocytes once it has arrived in the small intestine.
- small and medium chain fatty acids can move directly into the villi of the small intestine into the hepatic portal vein and travel through the bloodstream to the liver
- longer chain fatty acids have to first combine with bile to form a "micelle" which is then able to pass into the enterocyte. Once in the enterocyte the fatty acid is repackaged as a triglyceride with protein to from a chylomicron which then passes into the lacteal and eventually enters the bloodstream through the lymph.
What are chylomicrons responsible for?
Transport fats from the small intestine to the liver.
What is a lipoprotein?
It is like a little submarine for fat. Because fat is water insoluble, the large chains are unable to move through the blood but protein is water soluble. The lipoprotein generally consists of cholesterol and triglycerides on the inside surrounded by a protein shell.
What are the four different types of lipoproteins?
Chylomicrons - small milky proteins that transport lipids from the small intestine to the body cells to be used as energy
VLDL (very low density lipoproteins) - transport lipids from the liver cells to body cells and are very high in triglycerides (if your VLDL is high you have a lot of triglyercides in the blood)
LDL (low density lipoproteins) - transport cholesterol to cells so is composed primarily of cholesterol
HLD (high density lipoproteins) - also transports cholesterol but composed mainly of protein. It works to remove LDL and to recycle LDL by transporting it back to the liver.