Lipid digestion and metabolism Flashcards
What is one thing that all lipids have in common?
They are insoluble in water
Fat has _____ times more energy than carbs
2.25
Saturated fats
have all single bonds
Unsaturated fats
have double bonds
Triglyceride structure
1 glycerol
3 fatty acids
function of lipids (2)
source of energy
carrier for absorption
- fat soluble vitamins, cholesterol, and sex hormones need lipid carriers to move through the bloodstream
essential fatty acids (3)
linoleic acids (18C, 2 double bonds)
linolenic acids (18C, 3 double bonds)
arachidonic acid (20C, 4 double bonds)
What are essential fatty acids used for?
precursors of a number of unsaturated fatty acids
What is the main enzyme that digests lipids?
lipase
What are the two forms of lipase?
gastric lipase
- found in the stomach
- is functional in young animals, not active in mature animals
Pancreatic lipase
- primary fat digestion enzyme
- secreted with pancreatic juice
- secreted in inactive form
- activated by Ca in lumen of S.I. (as a zymogen!!!)
Pancreatic lipase is secreted as a ______
zymogen
What role does the stomach play in fat digestion?
The stomach creates small fat droplets, increasing the surface area
the pyloric sphincter meters fat droplets to the small intestine
Bile functions (2)
emulsification of fats
arrange triglycerides for hydrolysis via lipase
How does lipase digest fats?
it cleaves the fatty acids from the glycerol backbone
How does bile bind triglycerides?
hydrophobic tails bind to the bile, exposing the glycerols for cleaving
What is the complex of bile and free fatty acids known as?
a micelle
Micelle
free fatty acid + bile
What happens to the micelle as it interacts with the brush border?
The bile is recycled back into the lumen, as the free fatty acids move into the cells of the gut. Glycerols also move into the cells.
Inside the cells, the tryglycerides are reconstituted
The restored tryglycerides are combined with protein, phospholipid, and cholesterol to form a chylomicron
The chylomicron moves into the bloodstream
what is a chylomicron?
a combination of tryglycerides, proteins, phospholipids, and cholesterol that can move into the bloodstream
80% triglyceride
2% protein
7% phospholipids
11% cholesterol
Lipid digestion in ruminants
glycerols are turned into VFAs by microbes
Free fatty acids are saturated or incorporated into microbial cell walls to be digested later
Galactolipid
the lipid content of stems and leaves
Composed of a glycerol + galactose + FFAs
What are the end products of galactolipid digestion
galactose + glycerol = VFAs
FFAs = lipid alterations etc
Fatty acids derived from the rumen travel as…
FFAs OR microbial cell walls
What is catabolism?
destructive metabolic processes
What is anabolism?
Constructive metabolic processes
What are the functions of lipids in the body?
- oxidation to CO2 for ATP
- glycolipids, phospholipids
- lung alveolar integrity
- solubilize ADEK
- prostaglandins, sex hormones, adrenal hormones
- energy
How are lipids stored in the body?
they are stored as triglycerides, occuring in all tissues
adipose tissue is a special tissue specifically for storing fat, and is made up of adipocytes
What is the name of the cells that makes up adipose tissue?
adipocytes
What happens in the body in terms of fat storage during times of excess nutrients?
glucose, protein, and fats are converted into fat storage
What happens in the body in terms of fat storage in times of nutrient deficiency?
fat is broken down for energy
Does insulin increase or decrease fat storage?
increase
does epinepherine increase or decrease fat storage?
decrease
does cortisol increase or decrease fat storage?
decrease
does glucagon increase or decrease fat storage?
decrease
does growth hormone increase or decreasae fat storage?
decrease
Typically, the composition of triglycerides in the body is….
similar to what is consumed
Swine fed unsaturated fatty acids will deposit unsaturated fatty acids. This is not the case for…
ruminants
How long are fat soluble vitamins typically stored in the tissues?
30-90 days
In monogastric animals, milk fat is typically derived from…
glucose
In ruminants, milk fat is typically derived from…
acetate
Fatty acids are produced from…
Acetyl coA (2 carbons)
From where can acetyl coA be sourced?
carbs, proteins, VFAs and degraded fats
Where are fatty acids synthesized in the cell?
the cytosol
How are fats made in the cell?
by the addition of acetyl coA (two carbons at a time)
What is the typical length of a fatty acid that is produced by the body?
16 carbons
What enzyme is responsible for building fatty acids in the body?
fatty acid synthase
Fatty acid synthesis depends on….
the nutrient status of the animal (slows with deficiency of energy)
Which enzyme is responsible breaking down triglycerides?
tissue lipase
triglyceride + ______ = glycerol + fatty acid
tissue lipase
What is beta oxidation?
The stepwise removal of 2 carbons from fatty acids, (removing one molecule of acetate (2C) as acetyl CoA)
In beta oxidation, fats are degraded to….
Acetyl CoA, two carbons at a time
What happens to acetyl coa produced by beta oxidation?
It goes into the krebs cycle, located in the mitochondria
For a 16 carbon fat, what is the yield of acetyl CoA?
8 acetyl CoA
What is the yield of NADH and FADH2 from one round beta oxidation?
1 NADH, 1 FADH2 are produced from one round of beta oxidation
one acetyl coA is also produced
For a 16 carbon fatty acid, what is the yield of ATP and other molecules from beta oxidation and the krebs cycle?
Beta oxidation produces 7 FADH and NADH
- 7 FADH -> ETC (2ATP) = 14
- 7 NADH -> ETC (3ATP) = 21
Beta oxidation TOTAL = 35 ATP
8 Acetyl CoAs -> krebs = 8(3 NADH + 1 FADH + 1 GTP)
Krebs TOTAL = 96 ATP
TOTAL ATP = 131ATP
How does ketosis occur?
When there is increased energy demand, B oxidation increases
There is a buildup of acetyl coA, overloading the krebs cycle and backing it up
The liver converts this excess acetyl coA into the ketones acetoacetic acid, B-hydroxybutyric acid, and acetone
as ketones increase, blood pH decreases, causing metabolic acidosis
Additionally, acetoacetic acid toxicity can cause death
What are the three main situations where ketosis is commonly seen?
- lactating ewes (twins/triplets)
- high producing dairy cows
- keto diet
What are the three ketones that the liver produces while in ketosis
- acetoacetic acid
- B-hydroxybutyric acid
- acetone
What are the symptoms of ketosis?
weak, trembling, acetone breath
How is ketosis treated?
- Ca gluconate
- Na propionate
- buffers (increase the pH)
- provide glucose
