15 ch110 lipids timberlake.ppt

7/27/2019 15 CH110 Lipids Timberlake.ppt

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Chapter 15 Lipids

15.1

Lipids

Copyright 2007 by Pearson Education, Inc.

Publishing as Benjamin Cummings


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Lipids

Lipids are

Biomolecules that contain fatty acids or a steroid

nucleus.

Soluble in organic solvents but not in water. Named for the Greek word lipos, which means fat. Extracted from cells using organic solvents.


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Types of Lipids

The types of lipids containing fatty acids are

Waxes.

Fats and oils (triacylglycerols).

Glycerophospholipids.

Prostaglandins.

Not steroids, as they do not contain fatty acids.


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Structures of Lipids




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15.2 Fatty Acids




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Fatty Acids

Fatty acids

Are long-chain

carboxylic acids.

Typically contain 12-18carbon atoms.

Are insoluble in water.

Can be saturated or

unsaturated.




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Fatty Acid Formulas

The formulas for fatty acids are written as

Condensed formulas.

Line-bond formulas.

For example caprylic acid with 8 carbon atoms.

CH3(CH2)6COOH

CH3CH2CH2CH2CH2CH2CH2COOH

OH

O


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Saturated fatty acids have

Single CC bonds. Molecules that fit closely together

in a regular pattern. Strong attractions between fatty

acid chains.

High melting points that make

them solids at room temperature.

Saturated Fatty Acids

Copyright 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings


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Some Saturated Fatty Acids



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Unsaturated Fatty Acids

Unsaturated fatty acids

Have one or more double C=C bond

Typically contain cis double bonds.



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Properties of Unsaturated Fatty

Acids

Unsaturated fatty acids

Have kinks in the fattyacid chains.

Do not pack closely.

Have few attractionsbetween chains.

Have low melting points.

Are liquids at roomtemperature.

kinks inchain




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Comparing Melting PointsofSome Fatty Acids



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Learning Check

Assign the melting points of17C, 13C, and 69Cto the correct fatty acid. Explain.

stearic acid (18 C) saturated

oleic acid (18 C) one double bondlinoleic acid (18 C) two double bonds


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Solution

Stearic acid is saturated and would have a higher

melting point than the unsaturated fatty acids.

Because linoleic has two double bonds, it would have

a lower mp than oleic acid, which has one double

bond.

stearic acid mp 69C saturated

oleic acid mp 13C

linoleic acid mp -17C most unsaturated


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Prostaglandins

Prostaglandins have

20 carbon atoms in their fatty acid chains.

An OH on carbon 11 and 15.

A trans double bond at carbon 13.


C 11

C 15C 13


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Prostaglandins in the Body

Prostaglandins are

Produced by injuredtissues.

Involved in pain,fever, andinflammation.

Not produced whenanti-inflammatory

drugs such as aspirininhibit their synthesis.




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Omega-6 and Omega 3- Fatty

Acids

Fatty acids

In vegetable oils are mostly omega-6 with

the first C=C at C6.

linoleic acid

CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH6

In fish oils are mostly omega-3 with the

first C=C at C3.

linolenic acidCH3CH2(CH=CHCH2)3(CH2)6COOH

3

Copyright 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings


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Some Omega-6 and Omega-3

Fatty Acids


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Learning Check

Write a fatty acid with 10 carbon atoms that is:

A. saturated

B. monounsaturated omega-3

C. monounsaturated omega-6


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Solution

Write a fatty acid with 10 carbon atoms that is:

A. saturated

CH3

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

COOH

B. monounsaturated omega-3

CH3CH2CH=CHCH2CH2CH2CH2CH2COOH

C. monounsaturated omega-6

CH3CH2CH2CH2CH2CH=CHCH2CH2COOH


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Waxes, Fats, and Oils




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Waxes

Waxes are

Esters of saturated fatty acids and long-chain alcohols.

Coatings that prevent loss of water by leaves of plants.

TABLE 17.2



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Fats and Oils: Triacylglycerols

Fats and oilsare

Also called triacylglycerols.

Esters of glycerol.

Produced by esterification. Formed when the hydroxyl

groups of glycerol react with the

carboxyl groups of fatty acids.




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In a triacylglycerol,

Glycerol forms ester bonds with three fatty acids.

Triacylglycerols



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Formation of a Triacylglycerol

glycerol + three fatty acids triacylglycerol

OHCH2

OH

OHCH2

CHO

(CH2)14CH3CHO

O

(CH2)14CH3CHO

O

(CH2)14CH3CHO

+ 3H2O

O

O

C (CH2)14CH3

CH O

O

C (CH2)14CH3

CH2 O

O

C (CH2)14CH3

CH2

+


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Olive Oil

Olive oil

Contains a high

percentage of oleic

acid, which is a

monounsaturated fatty

acid with one cis

double bond.



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Learning Check

What are the fatty acids in the following triacylglycerol?

(CH2)12CH3

O

C

CH(CH2)7CH3(CH2)7CH

O

C

O

(CH2)16CH3C

O

O

OCH2

CH2

CH


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Solution

Stearic acid

Oleic acid

Myristic acid(CH2)12CH3

O

C

CH(CH2)7CH3(CH2)7CH

O

C

O

(CH2)16CH3C

O

O

OCH2

CH2

CH


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Melting Points of Fats and Oils

A triacylglycerol that is a fat

Is solid at room temperature.

Is prevalent in meats, whole milk, butter, and cheese.

A triacylglycerol that is an oil

Is liquid at room temperature.

Is prevalent in plants such as olive and safflower.


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Oils with Unsaturated Fatty Acids

Oils

Have more unsaturated fats.

Have cis double bonds that cause kinks in the

fatty acid chains. Cannot pack triacylglycerol molecules as close

together as in fats.

Have lower melting points than saturated fats.

Are liquids at room temperature.


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Diagram of Triacylglycerol with


Unsaturated fatty acid

chains have kinks that

do not allow close

packing.



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Saturated and Unsaturated Fatty

Acids In Fats and Oils



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Chemical Properties of

Triacylglycerols




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The chemical reactions of triacylglycerols are similar

to those of alkenes and esters.

Inhydrogenation, double bonds in unsaturated

fatty acids react with H2 in the presence of a Ni orPt catalyst.

In hydrolysis, ester bonds are split by water in the

presence of an acid, a base, or an enzyme.

Chemical Properties of

Triacylglycerols


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Hydrogenation of Oils

Thehydrogenation of oils

Adds hydrogen (H2) to the carbon atoms of double bonds.

Converts double bonds to single bonds.

Increases the melting point.

Produces solids such as margarine and shortening.

Copyright 2007 by Pearson Education, Inc Publishing as Benjamin Cummings


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Hydrogenation

Ni

+ 3H2

glyceryl tripalmitoleate

(tripalmitolean)

glyceryl tripalmitate

(tripalmitin)

O

(CH2)14CH3C

O

(CH2)14CH3C

O

(CH2)14CH3C

O

O

OCH2

CH2

CH

CH(CH2)7CH3(CH2)5CH O

C

CH(CH2)7CH3(CH2)5CH

O

C

CH(CH2)7CH3(CH2)5CH

O

C

O

O

OCH2

CH2

CH


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What product(s) is obtained from the complete

hydrogenation of glyceryl trioleate?

1. Glycerol and 3 oleic acids2. Glyceryltristearate

3. Glycerol and 3 stearic acids

Learning Check


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What product(s) is obtained from the complete

hydrogenation of glyceryl trioleate?

2. Glyceryltristearate

Solution


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Olestra, A Fat Substitute

Olestra is

Used in foods as an artificial fat.

Sucrose linked by ester bonds to several long-chainfatty chains.

Not broken down in the intestinal tract.



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Cisand TransFatty Acids

Unsaturated fatty acids can be

Cis with bulky groups on same side of C=C.CH3 (CH2)5 (CH2)7COOH cis

C=CH H

Trans have bulky groups on opposite sides of C=C.

CH3 (CH2)5 H

C=C trans

H (CH2)7COOH


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Trans Fatty Acids and

Hydrogenation

Trans fatty acids

Are formed during hydrogenation when cis double

bonds are converted to trans double bonds.

In the body behave like saturated fatty acids. Are estimated to make up 2-4% of our total

Calories.

Are reported in several studies reported to raise

LDL-cholesterol and lower HDL-cholesterol.


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Learning Check

(1) True or (2) False

A. There are more unsaturated fats in vegetable oils.

B. Vegetable oils have higher melting points than fats.C. Hydrogenation of oils converts some cis-double

bonds to trans- double bonds.

D. Animal fats have more saturated fats.


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Solution

(1) True or (2) False

A. T There are more unsaturated fats in vegetable oils.

B. F Vegetable oils have higher melting points than fats.

C. T Hydrogenation of oils converts some cis-double

bonds to trans- double bonds.

D. T Animal fats have more saturated fats.


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Hydrolysis

In hydrolysis,

Triacylglycerols split into glycerol and three fatty acids.

An acid or enzyme catalyst is required.

OCH2

OCH

OCH2

OHCH2

OHCH

OHCH2

O

(CH2)14CH3CHO

H2O

O

(CH2)14CH3C

O

(CH2)14CH3C

O

(CH2)14CH3C

H++3

+ 3


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Saponification and Soap

Saponification

Is the reaction of a fat with a strong base.

Splits triacylglycerols into glycerol and the salts of

fatty acids.

Is the process of forming soaps (salts of fattyacids).

With KOH gives softer soaps.


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Saponification

O

O

C (CH2)14CH3

CH O

O

C (CH2)14

CH3

CH2 O

O

C (CH2)14CH3

CH2

+ 3NaOH

Na+-O

O

C (CH2)14CH33

OH

CH OH

CH2 OH

CH2

+

soap


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What products are obtained from the complete

hydrolysis of glyceryl trioleate?

1. Glycerol and 3 oleic acids

2. Glyceryl tristearate3. Glycerol and 3 stearic acids

Learning Check


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What products are obtained from the complete

hydrolysis of glyceryl trioleate?

1. Glycerol and 3 oleic acids

Solution


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Learning Check

Write the product of the following reaction.

OCH2

O

O

CH2

CH

CH(CH2)7CH3(CH2)5CH

O

CO

CH(CH2)7CH3(CH2)5CHC

O

C CH(CH2)7CH3(CH2)5CH

H2

Ni+ 3


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Solution

O

O

CH2

CH

OCH2

(CH2)14CH3

O

C

O(CH2)14CH3C

(CH2)14CH3

O

C


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Glycerophospholipids are

The most abundant lipids in cell membranes.

Composed of glycerol, two fatty acids, phosphateand an amino alcohol.

Glycerol

PO4Amino

alcohol

Glycerophospholipids

Fatty acid

Fatty acid


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Glycerophospholipids Are Polar

A glycerophospholipid has

Two nonpolar fatty acid chains.

A phosphate group and a polar amino alcohol.

CH3

+ +HOCH2CH2NCH3 HOCH2CH2NH3

choline CH3 ethanolamine

+

NH3

Amino alcoholsHOCH2CHCOO

serine

St t d P l it f A


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Structure and Polarity of A

Glycerophospholipid



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Lecithin and cephalin are glycerophospholipids

Abundant in brain and nerve tissues.

Found in egg yolk, wheat germ, and yeast.

Lecithin and Cephalin

Copyright 2007 by Pearson Education, Inc Publishing as Benjamin Cummings


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Learning Check

Identify each as a

A. fatty acid B. triacylglycerol

C. amino alcohol D. glycerophospholipid

1. glyceryl trioleate

2. cephalin

3. choline

4. palmitic acid


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Solution

Identify each as a

A. fatty acid B. triacylglycerol

C. amino alcohol D. glycerophospholipid

1. glyceryl trioleate B. triacylglycerol

2. cephalin D. glycerophospholipid

3. choline C. amino alcohol

4. palmitic acid A. fatty acid


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Learning Check

Identify the components and type of glycerophospholipid

O

CH2O C (CH2)16 CH3

OCH2O C (CH2)16 CH3

+

O NH3

CH2O P O CH2CHCOO-

O-


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Solution

Identify the components and type of glycerophospholipidO

CH2O C (CH2)16 CH3

O 2 stearic acids

CH2O C (CH2)16 CH3

+

O NH3

type = cephalinCH2O P O CH2CHCOO-

serineO-

phosphate amino alcohol


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Sphingolipids




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Sphingolipids

Sphingolipids

Are similar to phospholipids.

Contain sphingosine (a long-chain amino alcohol), a

fatty acid, phosphate, and a small amino alcohol.

Have polar and nonpolar regions.

sphingosine

PO4amino

alcohol

fatty acid


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Sphingosine

Sphingosine is a long-chain unsaturated amino alcohol.

CH3(CH

2)12

CH=CHCHOH

CHNH2

CH2OH

sphingosine


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In sphingomyelin, a sphingolipid found in nerve cells

There is an amide bond between a fatty acid andsphingosine, an 18-carbon alcohol.

Sphingolipids



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Glycosphingolipids

Glycosphingolipids

contain

monosaccharides

bonded to theOHof sphingosine by aglycosidic bond.


Glycosphingolipids and


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Glycosphingolipids and

Cerebrosides

Glycosphingolipids

Are sphingolipids that containmonosaccharides.

Can be a cerebroside with galactose.



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Gangliosides

Gangliosides Are similar to cerebrosides, but contain two or

more monosaccharides.

Are important in neurons.

Act as receptor for hormones and viruses.

Can accumulate and cause genetic diseases.


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Gangliosides

GM2 is a ganglioside That accumulates in Tay-Sachs disease.



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Lipid Diseases (Lipidoses)

In many lipid diseases, the deficiency of an enzyme

causes the accumulation of glycolipids.


TABLE 17.3


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Learning Check

Identify each as a

1) Fatty acid 2) Triacylglycerol

3) Amino alcohol 4) Glycerophospholipid

5) Glycosphingolipid

A. Glyceryl trioleate

B. Cephalin

C. Choline

D. Galactocerebroside

E. Palmitic acid


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Solution

A. Glyceryl trioleate 2) Triacylglycerol

B. Cephalin 4) Glycerophospholipid

C. Choline 3) Amino alcohol

D. Galactocerebroside 5) Glycosphingolipid

E. Palmitic acid 1) Fatty acid


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Steroids: Cholesterol, Bile Salts,

and Steroid Hormones

CH3

CH3CH3

CH3

HO

CH3




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Steroid Nucleus

Asteroid nucleus consists of

3 cyclohexane rings.

1 cyclopentane ring.

No fatty acids.

steroid nucleus


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Cholesterol

Cholesterol

Is the most abundant steroid in the body.

Has methyl CH3- groups, alkyl chain, and -OH

attached to the steroid nucleus.

CH3

CH3CH3

CH3

HO

CH3


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Cholesterol in the Body

Cholesterol in the body

Is obtained from meats,

milk, and eggs.

Is synthesized in the liver.

Is needed for cell

membranes, brain and

nerve tissue, steroid

hormones, and Vitamin D.

Clogs arteries when highlevels form plaque.

A normal, open artery.



An artery clogged by

cholesterol plaque


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Cholesterol in Foods

Cholesterol is

Synthesized inthe liver.

Obtained from

foods. Considered

elevated ifplasma

cholesterolexceeds 200mg/dL.

TABLE 17.4



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Learning Check

Match the components of the cholesterol molecule with

the following:

___ carbon chain ___hydroxyl group

___ steroid nucleus ___methyl group

CH3

CH3CH3

CH3

HO

CH3

AC

B

D


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Solution

Match the components of the cholesterol molecule with

the following:

D carbon chain A hydroxyl group

C steroid nucleus B methyl group

CH3

CH3CH3

CH3

HO

CH3

AC

B

D


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Bile Salts

Bile salts

Are synthesized in the liver from cholesterol.

Are stored in the gallbladder.

Are secreted into the small intestine.

Have a polar and a nonpolar region

Mix with fats to break them part.

Emulsify fat particles to provide large surface area.


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Bile Salts

OH

COO- Na+CH2

H

N

O

COH

CH3

CH3

HO

CH3

glycine, an amino acidcholic acid, a bile acid

sodium glycocholate, a bile salt

Nonpolar region

Polar region


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Lipoproteins

Lipoproteins Combine lipids with proteins and phospholipids. Are soluble in water because the surface consists of

polar lipids.



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Types of Lipoproteins

Lipoproteins

Differ in density, composition, and function.

Include low-density lipoprotein (LDLs) and high-

density lipoprotein (HDLs).

TABLE 17.5


Transport of Lipoproteins in


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Transport of Lipoproteins in

the Body


S i


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Steroid Hormones

Steroid hormones

Are chemical

messengers in cells.

Are produced from

cholesterol.

Include sex hormones

such as androgens

(testosterone) in

males and estrogens(estradiol) in females.


Ad l C i id


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Adrenal Corticosteroids

Adrenal corticosteroids are steroid hormones that

Are produced by the adrenal glands located on

the top of each kidney.

Include aldosterone, which regulates electrolytes

and water balance by the kidneys.

Include cortisone, a glucocorticoid, which

increases blood glucose level and stimulates the

synthesis of glycogen in the liver.

Ad l C i id


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Adrenal Corticosteroids


A b li St id


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Anabolic Steroids

Anabolic steroids Are derivatives of testosterone.

Are used illegally to increase muscle mass.

Have side effects including fluid retention, hair growth,

sleep disturbance, and liver damage.


L i Ch k


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Learning Check

Identify each as a

1. fatty acid 2. steroid 3. triacylglycerol

4. phospholipid 5. sphingolipid

A. cholesterolB. glycerol, 2 fatty acids, phosphate, and choline

C. glyceryl tristearate

D. sphingosine, fatty acid, phosphate, and choline

E. estradiol

F. bile salts

G. lipids in plasma membranes

S l ti


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Solution

A. cholesterol 2 steroidB. glycerol, 2 fatty acids, phosphate, and choline

4 phospholipid

C. glyceryl tristearate 3 triacylglycerol

D. sphingosine, fatty acid, phosphate, and choline5 sphingolipid

E. estradiol 2 steroid

F. bile salts 2 steroid

G. lipids in plasma membranes

4 phospholipid, 5 sphingolipid

.


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Cell Membranes



C ll M b


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Cell Membranes

Cell membranes

Separate cellular contents from the external

environment.

Consist of a lipid bilayer made of two rows of

phospholipids.

Have an inner portion made of the nonpolar tails of

phospholipids with the polar heads at the outer

and inner surfaces.

Fluid Mosaic Model of Cell


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Membranes

The lipid bilayer

Contains proteins, carbohydrates, and

cholesterol.

Has unsaturated fatty acids that make cellmembranes fluid-like rather than rigid.

Has proteins and carbohydrates on the surface

that communicate with hormones and

neurotransmitters.

Fl id M i M d l


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Fluid Mosaic Model



Transport Through Cell


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p g

Membranes

The transport of substances through cell

Membranes involves

Diffusion (passive transport), which moves

particles from a higher to a lower concentration. Facilitated transport, which uses protein channels

to increase the rate of diffusion.

Active transport, which moves ions against a

concentration gradient.

Transport Pathways Through Cell


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p y g

Membranes


Learning Check


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Learning Check

The transport of particles across a cell membrane from

high concentration to low concentration is called

1. Facilitated transport

2. Diffusion

3. Active transport

Solution


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Solution

The transport of particles across a cell membrane from

high concentration to low concentration is called

2. Diffusion

15 ch110 lipids timberlake.ppt

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