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AnnouncementsAnnouncements & Agenda& Agenda (04/18/07)(04/18/07)Extra Credit Assignment Due NOW!Extra Credit Assignment Due NOW!Exam Fri 04/20 (Ch 13,14,15)Exam Fri 04/20 (Ch 13,14,15) REVIEW @ 3pm and 5 pm Today!!!REVIEW @ 3pm and 5 pm Today!!! exam exam will notwill not include pp. 520-524 include pp. 520-524 START at 10:30 amSTART at 10:30 am

TodayToday Cholesterol (15.6)Cholesterol (15.6) More steroids (15.6)…More steroids (15.6)… Cell membranes (15.7)Cell membranes (15.7)

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OHCH2

OH

OHCH2

CHO

(CH2)14CH3CHO

O

(CH2)14CH3CHO

O

(CH2)14CH3CHO

Last Time: Formation of Fats & Oils Last Time: Formation of Fats & Oils (Triacylglycerols)(Triacylglycerols)

glycerol + three fatty acids triacylglycerolglycerol + three fatty acids triacylglycerol

+ 3H+ 3H22OO

O

O

C (CH2)14CH3

CH O

O

C (CH2)14CH3

CH2 O

O

C (CH2)14CH3

CH2

+

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The chemical reactions of triacylglycerols are The chemical reactions of triacylglycerols are similar to those of alkenes and esters. similar to those of alkenes and esters.

• HydrogenationHydrogenation of double bonds in unsaturated of double bonds in unsaturated fatty acids by Hfatty acids by H22 (compare to alkenes) (compare to alkenes)..

• HydrolysisHydrolysis of ester bonds by water in the of ester bonds by water in the presence of an acid, a base, or an enzyme presence of an acid, a base, or an enzyme (compare to esters).(compare to esters).

Last Time: 15.4 Chemical Properties of Last Time: 15.4 Chemical Properties of TriacylglycerolsTriacylglycerols

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• the most abundant lipids in cell membranes. the most abundant lipids in cell membranes. • composed of glycerol, two fatty acids, composed of glycerol, two fatty acids,

phosphate, and an amino alcohol.phosphate, and an amino alcohol.

Glycerol

PO4Amino alcohol

Last Time: 15.5 GlycerophospholipidsLast Time: 15.5 Glycerophospholipids

Fatty acid

Fatty acid

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Last Time: Steroid NucleusLast Time: Steroid Nucleus

Consists of:Consists of:• 3 cyclohexane rings.3 cyclohexane rings.• 1 cyclopentane ring.1 cyclopentane ring.• no fatty acids.no fatty acids.

steroid nucleussteroid nucleus

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CholesterolCholesterol

• is the most abundant steroid in the body. is the most abundant steroid in the body. • has methyl CHhas methyl CH33- groups, alkyl chain, and -- groups, alkyl chain, and -

OH attached to the steroid nucleus.OH attached to the steroid nucleus.

CH3

CH3CH3

CH3

HO

CH3

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Cholesterol in the BodyCholesterol in the Body

• is obtained from meats, is obtained from meats, milk, and eggs. milk, and eggs.

• is synthesized in the liver.is synthesized in the liver.• is needed for cell is needed for cell

membranes, brain and membranes, brain and nerve tissue, steroid nerve tissue, steroid hormones, and Vitamin D.hormones, and Vitamin D.

• clogs arteries when high clogs arteries when high levels form plaque.levels form plaque.

An artery clogged by cholesterol plaque

A normal, open artery.

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Cholesterol in FoodsCholesterol in Foods

• is considered is considered elevated if elevated if plasma plasma cholesterol cholesterol exceeds 200 exceeds 200 mg/dL.mg/dL.

• is synthesized is synthesized in the liver and in the liver and obtained from obtained from foods.foods.

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Lipoproteins: LDL, HDL, Etc…Lipoproteins: LDL, HDL, Etc…

• combine lipids combine lipids with proteins & with proteins & phospholipids.phospholipids.

• are soluble in are soluble in water because water because the surface the surface consists of polar consists of polar lipids.lipids.

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Types of LipoproteinsTypes of Lipoproteins

• differ in density, composition, and function.differ in density, composition, and function.• include low-density lipoprotein (LDLs) and include low-density lipoprotein (LDLs) and

high-density lipoprotein (HDLs).high-density lipoprotein (HDLs).

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Transport of Lipoproteins in the BodyTransport of Lipoproteins in the Body

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Steroid HormonesSteroid Hormones• chemical messengers in cells.chemical messengers in cells.• sex hormones. sex hormones.

Androgens in males (testosterone) Androgens in males (testosterone) Estrogens in females (estradiol)Estrogens in females (estradiol)

• Adrenocortical hormones from adrenal glands.Adrenocortical hormones from adrenal glands.-mineralocorticoids (electrolyte balance)-mineralocorticoids (electrolyte balance)-glucocorticoids regulate glucose level-glucocorticoids regulate glucose level

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Steroid HormonesSteroid Hormones• are produced from are produced from

cholesterol. cholesterol.

• include sex include sex hormones such as hormones such as androgens androgens (testosterone) in (testosterone) in males and males and estrogens (estradiol) estrogens (estradiol) in females.in females.

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Adrenal CorticosteroidsAdrenal Corticosteroids

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Anabolic SteroidsAnabolic Steroids

• are derivatives of testosterone.are derivatives of testosterone.• are used illegally to increase muscle mass.are used illegally to increase muscle mass.• have side effects including fluid retention, hair have side effects including fluid retention, hair

growth, sleep disturbance, and liver damage.growth, sleep disturbance, and liver damage.

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Cell MembranesCell Membranes• separate cellular contents from the separate cellular contents from the

external environment.external environment.• consist of a lipid bilayer made of two consist of a lipid bilayer made of two

rows of phospholipids.rows of phospholipids.• have an inner portion made of the have an inner portion made of the

nonpolar tails of phospholipids with the nonpolar tails of phospholipids with the polar heads at the outer and inner polar heads at the outer and inner surfaces.surfaces.

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Fluid Mosaic Model of Cell Fluid Mosaic Model of Cell MembranesMembranes

The The lipid bilayerlipid bilayer • contains proteins, carbohydrates, and contains proteins, carbohydrates, and

cholesterol.cholesterol.• has unsaturated fatty acids that make cell has unsaturated fatty acids that make cell

membranes fluid-like rather than rigid.membranes fluid-like rather than rigid.• has proteins and carbohydrates on the has proteins and carbohydrates on the

surface that communicate with hormones surface that communicate with hormones and neurotransmitters.and neurotransmitters.

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Fluid Mosaic Model of Cell Fluid Mosaic Model of Cell MembranesMembranes

1919

Transport Through Cell MembranesTransport Through Cell Membranes

The transport of substances through cell membranesThe transport of substances through cell membranesinvolvesinvolves• diffusion (passive transport),diffusion (passive transport), which moves which moves

particles from a higher to a lower concentration.particles from a higher to a lower concentration.• facilitated transportfacilitated transport,, which uses protein channels which uses protein channels

to increase the rate of diffusion.to increase the rate of diffusion.• active transportactive transport,, which moves ions against a which moves ions against a

concentration gradient.concentration gradient.

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Transport Pathways Through Cell Transport Pathways Through Cell MembranesMembranes