Lipid Catabolism Flashcards
How is acyl-carnitine transported from cytoplasm to mitochondria?
Acyl-carnitine shuttle
How are fatty acids activated?
Conversion to acyl-coA (requires 2ATP)
What is the substrate for beta oxidation?
Acyl-coA
Products of each beta oxidation cycle
- 1 acetyl coA
- 1 fatty acyl coA (shortened by 2 carbon atoms)
- complete me
What type of fatty acids cannot be synthesised by the body?
Polyunsaturated fatty acids
deficiencies can lead to membrane disorders, increased skin permeability, mitochondrial damage
Fat soluble vitamins
ADEK (often stored in body fat)
-if fat intake or absorption is inadequate, secondary deficiencies can occur
What are compound lipids?
Lipids associated with other functional groups
Fatty acids, triglycerides and waxes are what kinds of lipids?
Simple lipids
Which molecules are the main energy storage form in adipose tissue?
Triglycerides
high energy yield per gram
More common to have an even or odd number of C’s in fatty acids?
Even (usually straight as well)
Polyunsaturated
Several double bonds
Are double bonds usually in cis or trans formation?
cis (same plane)
Most common fatty acid in humans
Palmitic acid (16C)
How many carbons in stearic acid?
18
How many carbon atoms in oleic acid?
18 but also has a double bond, cheekay ;)
Body can only make double bonds in fatty acids up to (?) carbons away from carboxyl end
9
Essential fatty acids?
Polyunsaturated fatty acids that cannot be synthesised by the body
Lineolic acid
18:2
Fatty acids-nomenclature
Carboxyl group is C1
C adjacent is alpha
C furthest away is omega
Fatty acids with up to (?) atoms are liquid at room temperature?
8
What do double bonds do to the melting point?
They lower it
Animal fats contain mostly what fatty acids?
Palmitic and stearic
Why is absorbing fatty acids more complicated than absorbing glycerol?
Glycerol is an alcohol
Fatty acids are hydrophobic
Short and medium length fatty acids
enter portal blood
(longer chain FA and monoglycerides-resynthesised to TG. This TG is then coated with a layer of protein, phospholipid and cholesterol to form a chylomicron, enter lymph and then blood)
Lipoprotein lipases
Chylomicrons
Hormone sensitive lipases
e.g. adrenaline sensitive
Cleavage of stored fat
Released free fatty acids and glycerol when energy is needed
Why are fatty acids linked to CoA
To activate them (requires 2ATP)
This generates an acyl-coA
Difference between acetylcoA and acyl-coA?
Acetyl coA contains 2 carbons, acyl coA contains an undefined number of carbons (any fatty acid attached to a coA)
Where does the linking of fatty acids to coA occur?
In the cytoplasm of cells
Where does oxidation of fatty acids occur?
Mitochondrial matrix
Function of the carnitine shuttle?
Transports fatty acids from cytoplasm to mitochondria
(fatty acid from acyl-coA transferred onto carnitine to form acyl-carnitine)
CoA molecules never transported across the membrane
Where does beta oxidation take place?
The mitochondrial matrix
How many steps in beta oxidation?
4
Products are acetyl coA and a new acyl coA (shortened by 2 carbon atoms)
1 FADH2
1 NADH+ plus H+
Where is glycerol-3-phosphate absent from?
Skeletal muscle, adipose tissue and the heart
