Lipid metaboilism Flashcards
What are lipids?
A group of compounds that are insoluble in water and consists primarily of hydrocarbon chains and rings
What makes lipids hydrophbic?
A high proportion of nonpolar C-H bonds
What are the 2 main categories of lipids?
Simple and complex lipids
Simple Lipids
Saturated and unsaturated fatty acids and their esters with alcohols such as glycerol (mono, di or triglycerides)
Fatty Acids
Complex Lipids
Contain other residues with the esterified FAs
EX: glycerophopholipids and amphipathic
Glycerophospholipids are ________
Amphipathic (both hydophobic and hydrophilic)
Triglycerides
Make up the bulk of body lipid
Deposited in the cytoplasm of adipocytes
Composed of 1 glycerol and 3 fatty acids
Fatty Acids
Long hydrocarbon chains
Saturated, monosaturated or polysaturated
Metabolic fuels, components of other classes of lipids
What are the function of triglycerides?
Main storage of fatty acids and chemical energy
Store twice as much energy as carbs (9 cal/gram of fat)
Fatty Acid chemical makeup
CH3(CH2)nCOO-
CH3(CH2)n =hydrophobic
COO-= hydrophilic
When are fatty acids saturated?
If hydrocarbon chains are joined by single covalent bonds
When are fatty acids unsaturated?
If there are double bonds in the chains
Where are the alpha, y and beta bonds in fatty acids?
Numbered from COOH (right end) C2, C3 and C4 are alpha, beta and y carbons
Where are the double bonds in fatty acids?
C12 and C9
What do unsaturated fatty acids increase?
Membrane fluidity
Where do UFAs predominate over SFAs?
In high plant and cold environment residing animals
Where are trans UFAs high in?
Partially hydrogenerated vegetable oils
Ex; maragarin (increases transfat deposits in the body
Trans UFAs compared to SFAs?
More linear and promote cholesterol absorption from the gut
Associated with hypercholesterolemia
Classification of animal fats
usually saturated fats and are solid at room temp
Classification of plant fats
Oils that are usually unsaturated and are liquid at room temp
What are the different types of complex lipids
Phospholipid, sphingolipids, cholesterol, bile sats
Phospholipid
Source of inositol triphosphate(IP3) and diacylglyceride (DAG) for signal transduction
Contain hydrophilic phosphate group
Lipid part is nonpolar and hydrophobic
Sphingolipids
Component of membranes
Cholesterol
Component of membrane, precursor of bile salts and steroid hormones
Bile salts
Lipid digestion and absorption, main product of cholesterol metabolism
What do phospholipids form?
They spontaneously form micelles or lipid bilayers
_______ are the basis of biological membranes
Lipid bilayers
How do phospholipids act as surfactants?
By reducing surface tension
Derived Lipids
Steroid hormones, eisosanoids, vitamins, ketone bodies, prostaglandins
Steroid hormones
Intracellular signals that regulate gene expression in target cells
Eicosanoids
Regulation of physiological functins
Vitamins
Vision, calcium metabolism, antioxidants, blood coagulation
ketone bodies
metabolic fuel
Prostaglandins
Produced by and active in most tissues
How are lipids transported?
In blood bound to lipoproteins
Pathways of fatty acid trafficking between tissues in the fasted state
- Triacylglycerol stored in adipose tissue is mobilized to release nonesterified fatty acids into circulation
- NEFA are taken up by skeletal muscle and liver
- They may enter the pathway of B-oxidation or synthesis of TG
- In the liver they may they may also secrete fatty acids in the form of low density lipoprotein TG
- Fatty acids may be taken up fro esterfication in adipose tissue and for oxidation or esterification in muscle via the lipoprotein lipase pathway
What are the 3 key pathways of lipid metabolism?
Exogenous pathway
Endogenous pathway
Reverse cholesterol transport
Exogenous Pathway
Action of lipoprotein lipase on chylomicrons to form 3 fatty acids
Reverse cholesterol transport
Action of high density lipoprotein in collecting peripheral cholesterol
The endogenous pathway
Role of lipoprotein lipase in cleaving very low density lipoproteins to form intermediate density lipoproteins, taken up by the liver or lo-density lipoproteins and FFAs
Where are fatty acids synthesized
In cytoplasm from and broken down in mitochondria to a common compound acetyl CoA
What yield more energy than glucose?
A catabolism of a 6-carbon fatty acid
How are fatty acids converted into acetyl groups?
b-oxidation
Lipema
Refers to turbid or lactescent appearance of serum or plasma
Due to hypertriglyceridemia (>200 mg/dl in dog)
Hyperlipidemia
Increased concentrations of lipids (triglycerides, cholesterol or both) in the blood
Postprandial (physiological) or pathological
Ketone bodies formed in the liver and can be used to generate energy in most aerobic tissues but not by the liver
Hepatic Lipidosis (feline fatty liver)
Most frequent cause for severe live failure in cats
Often as inappetence
Too much mobilization from adipose tissue
Up to 50% liver may be replaced by TG
What are Ketone bodies?
Small, soluble, freely circulating lipids
Result from partial b-oxidation of fatty acid
How are Ketone bodies formed?
TGs are broken down and resynthesized in adipose tissue –>
If adipose is sufficient acetyl CoA is channeled into alternate pathway –>
Converted into KBs
What happens to free fatty acids?
Used or energey ot converted in liver to KBs
What do high levels of KBs cause?
Ketosis
When does Ketoacidosis occur?
When KBs in blood are lower than pH
How do horses differ from ruminants?
They possess greater capacity of exporting lipoprotein from hepatocytes
And greater hepatic clearance capacity for FFAs
Pathway for ketone formation less developed
Ketosis is infrequent
What are ruminants more prone to than horse?
Fatty live infiltration (steatosis, fatty liver syndrome)
