Class 9- Lipids pt.2

sandy phillips

what are the three xxx responsible for lipid digestion? how does main one work

what are the three LIPASES:

1. lingual lipase

2. gastric lipase

3. pancreatic lipase - MAIN: breaks down each triglyceride into 2 free FA and a monoglyceride, sometimes this monoglyceride is split

   w another h2o to give a

   third FA and glycerol.

where does most of lipid digestion occur?

small intestine

general step of lipid digestion:

1. mouth: lingual lipase is there for babies for breast milk

2. stomach: slight digestion thanks to gastric lipase

3. small intestine: bile will emulsify fat, then pancreatic lipase splits up fat

what is bile made of? where is it made, where is it stored

made up of:

bile acids,

cholesterol,

phospholipids,

bile pigment: bilirubin and biliverdin

electrolytes

h20

made in the liver, then either stored in the gallbladder or released directly from the liver into the small intestine

how does bile aid digestion

• bile has hydrophobic and hydrophilic regions, has affinity for fat&h20

• it acts as emulsifier and creates fat droplets that repel e/o

• once in this emulsified/droplet form, fat is exposed to enzyme to be digested 

what is enterohepatic circulation? what would trap the bile?

cycle of how bile released is often reabsorbed, and sent back to liver

• soluble fibre can trap bile, so then bile sis excreted by poop

what happens for fat digestion in the stomach? which enzyme is involved? 

The acid-stable lingual lipase initiates lipid digestion by:

hydrolyzing one bond of triglycerides to produce diglycerides and FA. The degree of hydrolysis by lingual lipase is slight for most fats but may be appreciable for milk fats.

The stomach's churning action mixes fat with water and acid.

A gastric lipase accesses and hydrolyzes (only a very small amount of) fat.

what happens for fat digestion in the small intestine? which enzyme is involved? 

1. cholecytun CCK signals gallbladder to release bile via bile duct

fat+bile=emulsified fat

2. pancreatic lipase flows from pancreas via pancreatic duct

emulsified fat+pancreatic&intestinal lipases= monoglycerides, glycerol, FA

when a lipid is digested, what enters bloodstream directly?

glycerol +small lipids (SCFAs+ medium chain FA)

what happens to monoglycerides + long chain FA once broken down? 

monoglycerides + long chain FA will make chylomicrons that travel through lymph and enter blood stream 

what are chylomicrons? how are they formed?

chylomicrons= a type of lipoprotein that travel in the lymph vessels to the bloodstream.

formed by : lining cells on small intestine convert monoglycerides and long-chain fatty acids

on back into triglycerides and combine them with protein

what is a micelle in digestion 

 Bile salts envelope the long fatty

acids and monoglycerides to form

micelles

 the micelle fats can travel through the

watery environment due to process

of emulsion

how do chylomicrons get into circulatory system

• Chylomicrons enter the large

pores of lacteals.

• lacteals come together to form

the lymphatic vessels.

• lymphatic system transports to

the circulatory system.

what do lipoproteins do?

• they transport fat

• the body extracts what is needed form fats

• unused fat are picked up by liver, liver dismantles remnants to reuse these parts

what are the types of lipoproteins? which has highest proportion of fat to protein?

1. chylomicrons

2. Very-low-density proteins VLDL

3. low-density proteins LDL

4. High-density lipoproteins HDL

(deacr. order of fat content) 

chylomicrons are composed of

Chylomicrons contain so little protein and so much triglyceride

• they are the lowest in density for lipoproteins

VLDL ar composed of

Very-low-density lipoproteins (VLDL) are half triglycerides, accounting for their very low density.

LDL are composed of:

Low-density lipoproteins (LDL) are half cholesterol

• this cholesterol accounts for their implication in heart disease.

HDL are composed of

High-density lipoproteins (HDL) are half protein, accounting for their high density. 

how do VLDL, LDL, and HDL differ in transport functions?

•VLDL=carry triglycerides and other lipids made in the liver to the body cells for their use.

•LDL=  transport cholesterol and other lipids to the tissues. LDL are made from VLDL after they have donated many of their triglycerides to body cells.

•HDL =important for carrying

cholesterol AWAT from body cells to the liver for

disposal

what is atherosclerosis? 3 stages 

when ‘bad cholesterol’ accumulate sin artery walls, leads to build up of plaque 

1. the fatty streak

2. fibrous plaque

3. complete lesion and calcification

what is thrombosis

when clot grows so large it fully obstructs blood vessel

1)arterial thrombosis(clot in an artery)

2)venous thrombosis (clot in a vein),

what is embolus

when a blood clot breaks loose, it travels along circulatory system until reaching an artery 

heart attack vs stroke

where does cholesterol come from?

-  body naturally makes cholesterol in your

liver, making ~800–1500 mg/day vs 200-300

from food in diet of meat eaters.

 Cholesterol can also come from foods you eat.

This is called “dietary cholesterol” and is found in

animal foods like meat, poultry, milk products,

eggs, fish and seafood.

why is liver important ?

 essential for building cell membranes

 producing steroid hormones (like estrogen and

testosterone),

 synthesizing vitamin D,

 creating bile acids that aid in fat digestion and

nutrient absorption

how is total cholesterol calculated?

Your total cholesterol is a combined measure of:

 HDL cholesterol: Known as "good" cholesterol.

 LDL cholesterol: Known as "bad" cholesterol.

 20% of your triglyceride level: the fat in your blood.

how can you lower cholesterol lvls

 Exercise regularly. Regular exercise can lower triglycerides + boost "good" cholesterol.

 Avoid sugar and refined carbohydrates. Simple

carbohydrates in excess can increase triglycerides.

 loseweight and reduce your waist circumference.

 Choose healthier fats.

 Limit or avoid alcohol.

how does low vs high fibre diet effect blood cholesterol? 

what are phytosterols= sterols/stanols?

Phytosterols (fi-TAH-ster-ols) are natural products from plants

• structure similar to cholesterol , serve as structural component to plant 

• offered as dietary supplements

what are adipokines?

• cell-signaling proteins secreted by adipose tissue that has been related to a low-grade state of inflammation and different pathologies

ex= leptin

how does ingested fat go to body fat?

first is hydrolysis of TG

then lipoprotein lipase hydrolyzes TG from lipoproteins, releasing FA’s that can enter fat cells for storage (reassembled into TG)

how is body fat used for energy? 

Fat supplies 60% of the body’s ongoing energy needs during rest and also light-intensity activity

 Hormone-sensitive lipase:

• Enzyme inside fat cells that responds to hormones like epinephrine and glucagon which indicate a need for fuel.

• Dismantles the stored TG and releases glycerol and FA’s into blood when needed/signaled to

what are steps of lipolysis?

1. Lipases break down stored TG’s into FA’s and glycerol.

2. FA’s are transported through the bloodstream to muscles and other cells requiring energy.

3. Inside the mitochondria the FA’s

undergo beta-oxidation. This process breaks down the fatty acids into two-carbon units, forming acetyl-CoA.

4.Acetyl-CoA enters the Krebs cycle, also known as the citric acid cycle—> produces ATP

5. Waste Products : The final byproducts of this process are carbon dioxide & water, which are then released from the body.

what are situations when lipolysis could be induced?

i) During increased demand through

long-lasting and lower intensity

exercise

ii) During starvation or decreasing

intake of food energy

iii) Under fasting conditions and/or

inadequate carbohydrate, fats may

also be broken down to produce

ketone bodies—> brain

can use for fuel when glucose is

limited 

what is lipogenesis?

when liver breaks down glucose and puts them back tg to store as fat 

what are DRI for fat intake , grams and % of total cals 

44-78g per 2000cal or 20-35% of total energy  - there is no RDA or UL