Basic structure of lipids and lipoprotein
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168 Terms
Lipids are soluble in what type of solvents?
Non‑polar organic solvents such as benzene, chloroform, ether, hot alcohol, acetone
What is the difference between fat and oil at room temperature?
Fat is solid, oil is liquid
What elements mostly compose lipids?
Carbon, hydrogen, oxygen
What are the four main classes of lipids?
Simple lipids, compound lipids, derived lipids, lipids complexed to other compounds
Give examples of simple lipids.
Triacylglycerols (TAGs), waxes
Give examples of compound lipids.
Phospholipids, non‑phosphorylated lipids
Give examples of derived lipids.
Fatty acids, steroids, prostaglandins, cholesterol
Give examples of lipids complexed to other compounds.
Proteolipids, lipoproteins
What is the main storage form of energy in lipids?
Triacylglycerols
Which lipids are structural components of biomembranes?
Phospholipids, glycolipids, cholesterol
Which lipids act as metabolic regulators?
Steroid hormones and prostaglandins
Which lipids act as surfactants and emulsifying agents?
Amphipathic lipids
What lipid function provides electrical insulation?
Lipids in neurons
What lipid function provides thermal insulation?
Subcutaneous fat
What lipid function cushions internal organs?
Pads of fat
Which vitamins require lipids for absorption?
Fat‑soluble vitamins A, D, E, K
What is the general formula of saturated fatty acids?
CH3‑(CH2)n‑COOH
Give examples of saturated fatty acids.
Acetic acid, butyric acid, palmitic acid, stearic acid
Where are palmitic and stearic acids found?
Body fat
What defines unsaturated fatty acids?
Presence of one or more double bonds
What configuration do naturally occurring unsaturated fatty acids have?
Cis configuration
What configuration of fatty acids is formed during metabolism?
Trans fatty acids
What are essential fatty acids?
Linoleic acid (ω6) and linolenic acid (ω3)
Can arachidonic acid be synthesized in the body?
Yes, if essential fatty acids are supplied in the diet
What is the nutritional importance of penta‑enoic acid in fish oils?
It is an ω3 unsaturated fatty acid
What are eicosanoids derived from?
20‑carbon arachidonic acid
Name the families of unsaturated fatty acids.
ω3 (linolenic), ω6 (linoleic, arachidonic), ω9 (oleic)
Where are trans fatty acids commonly found?
Dairy products, hydrogenated oils, fast food, processed foods, bakery products
What are the adverse effects of trans fatty acids?
Altered blood lipids, systemic inflammation, endothelial dysfunction, insulin resistance, obesity
What is an acylglycerol?
Ester of fatty acids with glycerol
What are the classes of acylglycerols?
Monoacylglycerols, diacylglycerols, triacylglycerols
What is the difference between simple and mixed TAGs?
Simple TAGs have identical FAs, mixed TAGs have different FAs
Where is PUFA commonly esterified in TAGs?
At the β‑carbon of glycerol
What is the energy yield of fatty acids compared to carbs/proteins?
9 kcal/g vs 4 kcal/g
Where are TAGs synthesized mainly?
Liver
How are TAGs transported in blood?
As lipoproteins
Where are TAGs stored?
Adipose tissue
What is the simplest phospholipid?
Phosphatidic acid
What is the amphipathic nature of phospholipids?
They have hydrophobic tails and hydrophilic heads
What is the main constituent of cell membranes?
Glycerophospholipids
What is the main constituent of myelin sheath?
Sphingophospholipids
What is the role of phospholipids in lipoproteins?
Transport of TAGs and cholesterol
What is the steroid nucleus of cholesterol called?
Cyclopentanoperhydrophenanthrene nucleus
What are the structural features of cholesterol?
Four fused rings, hydroxyl at C‑3, double bond at C‑5/C‑6, methyls at C‑10/C‑13, side chain at C‑17
What is the molecular formula of cholesterol?
C27H46O
What is the most important sterol in the human body?
Cholesterol
List functions of cholesterol.
Membrane fluidity, nerve conduction, precursor of bile acids, steroid hormones, vitamin D3
Where does fatty acid biosynthesis occur?
Cytoplasm of liver, lactating mammary gland, adipose tissue
What are the precursors for fatty acid biosynthesis?
Excess dietary carbohydrates and proteins
How are unesterified fatty acids transported in blood?
Bound to albumin
What provides 2‑carbon units in fatty acid biosynthesis?
Malonyl‑CoA
What is the end product of fatty acid synthase complex?
Palmitic acid
What are the major sources of NADPH for lipogenesis?
Pentose phosphate pathway, cytosolic NADP+‑dependent malic enzyme
Where does β‑oxidation occur?
Mitochondria
Where are fatty acids activated before β‑oxidation?
Cytoplasm
What transports fatty acyl‑CoA into mitochondria?
Carnitine carrier system
What is released in each cycle of β‑oxidation?
Acetyl‑CoA, NADH, FADH2
How many cycles of β‑oxidation does palmitic acid require?
7 cycles
What is the final product of odd‑chain fatty acid oxidation?
Propionyl‑CoA
What can propionyl‑CoA be converted into?
Glucose (gluconeogenesis)
How does β‑oxidation differ for unsaturated fatty acids?
Depends on whether double bond is at even or odd carbon position
What are ketone bodies?
Water‑soluble compounds formed from acetyl‑CoA in liver and kidney
When are ketone bodies synthesized?
During fasting, starvation, or high‑fat diet
Name functional ketone bodies.
Acetoacetate, β‑hydroxybutyrate
Name the non‑functional ketone body.
Acetone
What is the rate‑limiting enzyme in ketogenesis?
HMG‑CoA synthase
What ketone body is excreted in expired air?
Acetone
What is the order of lipoproteins from most dense to least dense?
HDL > LDL > VLDL > Chylomicrons
What do chylomicrons transport?
Dietary TAGs
What does VLDL transport?
Endogenous TAGs from liver
What does LDL transport?
Cholesterol to tissues
What does HDL transport?
Cholesterol back to liver (reverse transport)
What enzyme degrades TAGs in chylomicrons?
Lipoprotein lipase
What happens to chylomicron remnants?
Taken up by liver
What is VLDL converted into after TAG delivery?
LDL
How is LDL taken up by tissues?
Receptor‑mediated endocytosis
What is the role of HDL in cholesterol metabolism?
Reverse cholesterol transport to liver
What is Type I hyperchylomicronemia caused by?
Lipoprotein lipase deficiency or ApoC‑II defect
What are the clinical features of Type I hyperchylomicronemia?
Pancreatitis, hepatosplenomegaly, eruptive xanthomas, no increased atherosclerosis risk
What is Type IIa familial hypercholesterolemia caused by?
Absent or defective LDL receptors
What are the clinical features of Type IIa familial hypercholesterolemia?
Accelerated atherosclerosis, MI before age 20, tendon xanthomas, corneal arcus
What is Type IV hypertriglyceridemia caused by?
Hepatic overproduction of VLDL
What is the clinical feature of Type IV hypertriglyceridemia?
Pancreatitis
What is Tangier disease caused by?
ABCA1 deficiency
What is the hallmark of Tangier disease?
Severe reduction in HDL
Which lipoprotein particle transports dietary lipids through blood?
Chylomicrons
What lipids are found in the core of chylomicrons?
TAGs and cholesterol esters
What surface protein is characteristic of chylomicrons?
ApoC‑II
What is the energy yield of fatty acids compared to proteins and carbohydrates?
9 kcal/g vs 4 kcal/g
What is the main site of ketone body synthesis?
Liver mitochondria
Which ketone body undergoes spontaneous decarboxylation to acetone?
Acetoacetate
Which lipoprotein is associated with tendon xanthomas?
LDL (Type IIa familial hypercholesterolemia)
Which familial dyslipidemia does not increase risk of atherosclerosis?
Type I hyperchylomicronemia
Which familial dyslipidemia may cause MI before age 20?
Type IIa familial hypercholesterolemia