13.9 Steroids Kyleigh Moyer Taylor Raker

What are Steroids?  A compound containing this ring formation  Three cyclohexane rings  Another cyclohexane ring is fused  Not necessarily esters but some are

Cholesterol  Most abundant and most important steroid in the human body  Plasma membrane in all animal cells  Second important function – synthesis of steroids  Ex. Sex Hormones, adrenocorticoid hormones

Cholesterol  Free form and esterified  Gallstones – free cholesterol  High Serum Cholesterol and diseases  Fear of Cholesterol  Necessary for human life  Produced by liver and body doesn’t need to take in by diet  When it reaches 150 mg/100 mL the liver reduces production by half

Cholesterol  In the body it's a dynamic state  Constantly circulated in blood  Hydrophobic  Cholesterol  Cholesterol esters  Need water-soluble carrier to circulate in blood

Lipoproteins: Carriers of Cholesterol  Contain core hydrophobic lipid  Shell of hydrophilic molecules High-density lipoprotein (HDL)  Good Cholesterol  33% Protein  30% Cholesterol  Chylomicrons  Carry Dietary Lipids  Synthesized in intestines

Lipoproteins  Low-density lipoprotein (LDL)  Bad Cholesterol  25% Protein  50% Cholesterol  Very-low-density lipoprotein (VLDL)  Carries triglycerides (fats)  Synthesized by Liver

Transportation in LDL  Starts out as large VLDL particles  Core contains triglycerides and cholesteryl esters  Surrounded by polar coat  When they reach muscles or fat tissues  Triglycerides and proteins are removed  Core shrinks and it become more dense  LDL

Transportation in LDL  Carried Cholesterol specific LDL-receptors  Concentrated areas called coated pits  After binding  LDL is taken inside  Liberates cholesterol from cholesteryl esters  In receptors are low then cholesterol builds up in blood

Transportation in HDL  Peripheral tissues to liver  Transfers to LDL  In serum converted to cholesteryl esters  Delivered to liver for synthesis of bile acids and steroid hormones  Binds to liver cell surface  Transfers cholesteryl esters to cell  Reenters circulation  Want high levels – gets rid of cholesterol

 Insoluble in water  Higher levels  Plaque build up  Atherosclerosis  High BP  Heart attack  Stroke  Smaller diameter blood vessels  Deprive cells of oxygen

 Most cholesterol transported by LDL  If there's enough LDL-receptors levels drop  When levels are high  Less receptors  Low levels  A lot of receptors  Not enough  Familial hypercholesterolemia

 High plasma cholesterol levels  Lacks LDL-receptors  Or not concentrated on coated pits  High LDL means his cholesterol  Serum cholesterol levels control  Synthesis by liver  High levels – low synthesis

 Reduce serum cholesterol  Number of drugs  Inhibit liver synthesis  Inhibits an essential enzyme  More LDL enters cells  Premenopausal women have more HDL

1. What’s the common structure of a steroid? 2. What’s the second most important function of steroids? 3. What’s the most abundant steroid? 4. What is the core of a lipoprotein? 4/21/12