newlecture 2 me for virtual

8/10/2019 NewLECTURE 2 ME for Virtual

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Introduction to Cell Biology

Lecture #2: bonds, chirality, sugars and lipids

Marcelo Ehrlich, PhD

Department of Cell Research and Immunology

2014

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4 types of chemical bonds

- covalent = two atoms share electrons

- ionic = based on the electrostatic forces between two

oppositely charged ions

- hydrogen = attractive interaction (dipole-dipole) between an

electronegative atom and an hydrogen atom bound to another

electronegative atom

- Van der waals = intermolecular forces which arrise from the

generation (transient) of dipoles

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Bond anglesBond anglesBond rigidity

3How do chemical bonds contribute to molecular shape?


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The form forming potential of carbon skeletons

Chains Branched trees Rings

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The function of molecules is determined by

their shape

The shape of molecules is determined by

the chemical bonds of the atoms which formit.

Chemical bonds can be defined in terms oftheir strength, polarity, angles and rigidity

?

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0.27nm

Figures 2-10, 2-14, Panel 2-2

water (H2O)

Water: the medium in which life started and the medium in

which life takes place. What are the characteristics of water that

contribute to the process of life?

+

+2-

+

+

2-

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Panels 2-2, 2-71998 and 2004 GARLAND PUBLISHING

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,MELTING AND ANNEALING 9


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-helix

Figure 4-102004 GARLAND PUBLISHING

Denaturation

RenaturationFolded state Random coil

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heat

alcohol

denaturing agents (urea)


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?

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Isomere = from the Greek isos= equal and mere = part

Compounds with the same molecular formula but with differentstructural formulae

Some definitions:

Stereoisomere: the atoms

are joined in the same way

but have a different spatial

arrangement

Structural isomere: the

atoms are joined in different

ways

C-C-C

H

H

H

H

H H

H

OH C-C-C

H

H

H

H

H H

HHO

Enantiomeres

Enantios = opposite

Mirror images of one

another

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L-aspartyl -L-phenylalanine methyl ester L-aspartyl -D-phenylalanine methyl ester

sweet bitter

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2

Carbo - Hydrates

monomer polymer15

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Chiral center - D configuration

Aldehyde

C

C

CO

OH

H

OHH2

H

Glyceraldehyde - the smallest sugar

(CH20)3 Carbo - Hydrate=

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hexosetriose pentose 17


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glyceraldehyde ribose glucose

fructose

hexose

ribulosedihydroxyacetone

triose pentose

aldose

ketose

Panel 2-3

2004GARLANDP

UBLISHING

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CH2OH

123

4 5

6

OHO

H

CH2OH

123

4 5

6

O

CHO

CH2OH

1

6C H2OH

1

6

CHO

L -glucose D -glucose

OH

OH

anomeric carbon


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Epimers of glucose 19


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2004 GARLAND PUBLISHING

CHO

CH2OH

1

6

D -glucose

glucose

CHO

CH2OH

1

6

D -galactose

galactose

CHO

CH2OH

1

6

D -mannose

mannosePanel 2-3

Epimers of glucose

Epimer= a stereoisomer that has a different configuration at only one

stereogenic center and are not mirror images of each other.

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RNA

3OH+2OH in RNA

3OH+2H in DNA

3H+2H=

dideoxynucleotide

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condensation hydrolysis

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Panel 2-32004 GARLAND PUBLISHING

glucose fructose

sucrose

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2004 GARLAND PUBLISHING Figure 13-18,20

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1 4 25


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1-4

1-4

glycogen, starch

cellulose

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monomer polymer28


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Figure 2-15


monomer polymer

- Structural component of membranes (essential for

compartmentalization)- Storage (energy, fat)

- Intracellular signaling

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Fatty Acids

- Long chain (even number of carbons),mono-carboxylic acids, that have a general

structure of

CH3(CH2)nCOOH

- Saturated (no double bonds) or unsaturated

palmitic acid - 16 carbons30


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palmitic acid - 16 carbons


Hydrophilic carboxylic acid head

Hydrophobic hydrocarbon tail

18 carbons 31


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stearic acid vs. oleic acid

saturated unsaturatedPanel 2-4


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Panel 2-42004 GARLAND PUBLISHING

ester bonds

Glycerides are lipids possessing a glycerol core structure

with one or more fatty-acyl groups attached by ester

linkages.

Tryglicerides are the main storage form of fat

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Glycerophospholipids

Glycerol linked to two fatty acids (tails) andone phosphate-based (head). Common

phospholipids in cell membranes are

phosphatdyl-choline, phosphatdyl-serine,

phosphatdyl-ethanolamine, phosphatdyl-

inositol.

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phosphatidylethanolamine cholesterolphosphatidylserine

Figures 11-72004 GARLAND PUBLISHING

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lipid bilayer

micelle

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