13.9Steroids

Kyleigh MoyerTaylor Raker

What are Steroids?

A compound containing this ring formation

Three cyclohexane rings

Another cyclohexane ring is fused

Not necessarily esters but some are

CholesterolMost abundant and most important steroid in the human body

Plasma membrane in all animal cells

Second important function – synthesis of steroidsEx. Sex Hormones, adrenocorticoid

hormones

Cholesterol

Free form and esterified Gallstones – free cholesterol

High Serum Cholesterol and diseasesFear of Cholesterol

Necessary for human lifeProduced 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 stateConstantly circulated in bloodHydrophobicCholesterol

Cholesterol esters

Need water-soluble carrier to circulate in blood

Lipoproteins: Carriers of Cholesterol

Contain core hydrophobic lipidShell of hydrophilic molecules

•High-density lipoprotein (HDL)

Good Cholesterol

33% Protein

30% Cholesterol

ChylomicronsCarry Dietary Lipids

Synthesized in intestines

LipoproteinsLow-density lipoprotein (LDL)Bad Cholesterol

25% Protein

50% Cholesterol

Very-low-density lipoprotein (VLDL)Carries triglycerides (fats)

Synthesized by Liver

Transportation in LDLStarts out as large VLDL particlesCore contains triglycerides and cholesteryl estersSurrounded by polar coatWhen they reach muscles or fat tissuesTriglycerides and proteins are removed

Core shrinks and it become more dense LDL

Transportation in LDLCarried Cholesterol specific LDL-receptorsConcentrated areas called coated pitsAfter bindingLDL is taken inside

Liberates cholesterol from cholesteryl estersIn receptors are low then cholesterol builds up in blood

Transportation in HDLPeripheral tissues to liver Transfers to LDL

In serum converted to cholesteryl estersDelivered to liver for synthesis of bile acids and steroid hormonesBinds to liver cell surfaceTransfers cholesteryl esters to cell

Reenters circulationWant 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