Lipids Flashcards
What physical characteristics do all lipids share?
- insoluble in water
- soluble in nonpolar compounds
What are the functions of lipids?
Function of Lipids
- major source of energy
- provide hydrophobic barrier
- serve as coenzymes, regulators (vitamins A, D, E, K)
- hormones
- mediators of inflammation
What are the classification of lipids?
- fatty acids
- triacylglycerides / triglycerides
- steriods and cholesterol
- phospholipids
- sphingolipids
- glycolipids
What lipid enables the formation of bilipid layers? What property enables them to do so?
Phospholipids are amphipathic hence have both hydrophilic and hydrophobic groups.
What are fatty acids?
Fatty acids are long chains of carboxylic acids
How are fatty acids classified?
Fatty acids are classifed according to degree of saturation:
- Saturated: no double bond
- Monounstaurated: 1 double bond
- Polyunsaturated: >2 double bonds
What molecules can carboxylic acid bind?
Carboxylic acid can bind to H, O, N
What is the effect of double bonds on the structure of fatty acids?
Double bonds cause a kink in the structure of fatty acids
What kind of fatty acids are associated with increased risk of cardiovascular disease?
Trans- and saturated fatty acids are associated with increased risk of cardiovascular disease
What kind of fatty acids are cardioprotective?
**Mono- **and **polyunsaturated fatty acids **are cardioprotective
What are the essential fatty acids?
Linoleic acid, iinolenic acid, and arachidonic acid
***arachidonic acid only becomes essential if linoleic acid is deficient
What are the 2 geometric isomerisms of unsaturated fatty acids?
CIS fatty acids - same side as the double bond
TRANS fatty acids - opposite sides of the double bond
What decreases fluidity of fatty acids?
Fluidity decreases with:
- increasing chain length = more C atoms
- increasing saturation = less double bonds
In labeling fatty acids, what do each of these numbers mean?
18 : 2 (9,12)
LINOLEIC ACID
18 : 2 (9,12)
18 - number of carbon atoms
2 - number of double bonds
**(9,12) **- location of double bonds
Why are some fatty acids considered essential? What are these fatty acids?
Some fatty acids are essential because humans cannot generate double bonds beyond position 9.
- **Linoleic acid **has double bonds at C9 & C12
- Linolenic acid has double bonds at C9, C12 & C15
- **Arachidonic acid **has double bonds at C5, C8, C11, & C14
Linoleic acid is a precursor of what fatty acid?
Linoleic acid is a precursor of arachidonic acid which is essential for prostaglandin synthesis
What does deficiency in linolenic acid result in?
Linolenic acid **deficiency **results in decreased vision and altered learning behavior.
What is arachidonic acid essential in? When does it become an essential fatty acid?
**Arachidonic acid **is essential in prostaglandin synthesis and becomes essential when linoleic acid is deficient.
How are omega fatty acids numbered?
The numbering of omega fatty acids starts from the last carbon atom
What are the 2 omega fatty acids that are correlated with a decreased risk of cardiovascular disease? What are they also know as?
decreased risk of cardiovascular disease
Omega-3 (linolenic acid)
Omega-6 (linoleic acid)
- lowers thromboxane production
- reduced tendency of platelets to aggregate
What must first be done before fatty acids can be used in metabolism?
Fatty acids must first be activated by the enzyme fatty acyl-CoA synthetase with the co-factor **pantothenic acid **to yield fatty acyl-CoA synthetase
How many ATP equivalents is used in the activation of fatty acids?
**2 ATP **equivalents are used in the activation of fatty acids
What is fatty acid synthesis for?
Fatty acid synthesis is for the formation of palmitate
Where does fatty acid synthesis occur? Which part of the cell?
Fatty acid synthesis occurs in the ff organs:
MAJOR: liver, lactating mammary gland
MINOR: adipose tissue
It occurs in the cytosol of the cell.
What are the substrates and products of Fatty Acid synthesis?
SUBSTRATES
= 1 acetyl CoA, 7 malonyl CoA, NADPH and ATP
PRODUCTS
= Palmitate only
What is the rate limiting step of Fatty Acid Synthesis?
_A_cetyl _C_oA _C_arboxylase catalyzes the conversion of acetyl CoA and ATP to malonyl CoA
“Addik sa Chicharon → Chubby”
What is the necessary co-factor in the rate-limiting step of fatty acid synthesis?
BIOTIN is the necessary cofactor of acetyl CoA carboxylase
(all carboxylases require biotin to carry out their function)
What are the 3 important steps in Fatty Acid Synthesis?
Important steps in Fatty Acid Synthesis
- synthesis of cytoplasmic acteyl CoA
- Acetyl CoA carboxylated to malonyl CoA by acetyl CoA carboxylase
- Assembly of palmitate by fatty acis synthase
How is cytoplasmic acetyl CoA synthesized?
Acetyl CoA is transfered to from the mitochondria to the cytoplasm through a citrate shuttle which only occurs in an energy-rich state due to:
- inhibition of Isocitrate Dehydrogenase so acetyl CoA is diverted away from TCA cycle
- increased ATP and increased citrate
NOTES:
- Acetyl CoA is produced in the mitochondrial matrix only
- Acteyl CoA cannot pass the the mitochondrial membrane hence it needs to use the citrate shuttle
What enzyme catalyzes the rxn
**acetyl CoA → malonyl CoA **?
What are its cofactor? activators?
acetyl CoA → malonyl CoA is catalyzed by the enzyme Acetyl CoA Carboxylase
cofactor: biotin
activators: insulin and citrate
“Addict sa Chicharon → Chubby”
What is the multienzyme complex that has an acyl carrier protein (ACP) which is responsible for the assembly of palmitate?
What is its cofactor?
Fatty acid synthetase synthesizes palmitate from 1 acetyl CoA and 7 malonyl CoA using NADPH as a reducing equivalent.
cofator: pantothenic acid
What is the sequence of steps in the assembly of palmitate?
Condensation → Reduction → Dehydration → Reduction
“Code Red DRed“
