unit 1.1 molecules

7/31/2019 Unit 1.1 Molecules

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Unit 1.1 Molecules

Biology DepartmentWatford Girls Grammar School


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Introduction

For each of the following you should beable to:

Describe the properties Know the general formulae & structure Understand the role in animals & plants

Water Carbohydrate

s Lipids

Proteins Nucleic acids


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Water

Water is a polar molecule It forms weak hydrogen bonds It remains a liquid over a wide

temperature range Water molecules stick to one another =

cohesion (surface tension)

Water molecules stick to othersubstances = adhesion (capillarity)

O

H

H

+

+

-


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Water

It has a high specific heat capacity sowater can maintain a reasonablyconstant temperature (homeostasis)

It has a high latent heat of vaporisation so animals use water to coolthemselves

It is less dense as a solid (ice) and ice is a poor conductor Water is a good solvent


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Carbohydrates

Contain the elements Carbon Hydrogen& Oxygen

There are 3 types:

Monosaccharides Disaccharides Polysaccharides


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Monosacharides

(CH2O)n If n=3, triose (glyceraldehyde) If n=5, pentose (fructose, ribose) If n=6, hexose (glucose, galactose) Monosaccharides are used for

o Energyo Building blocks

O

C C

C C

C

C


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Isomerism

They can exist as isomers: & glucose OH

OH


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Disaccharides

Formed from two monosaccharides Joined by a glycosidic bond A condensation reaction:

glucose + glucose maltose glucose + galactose lactose glucose + fructose sucrose


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Condensation reaction

O

C C

C C

C

CO

C C

C C

C

C

OH OH


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O

C C

C C

C

CO

C C

C C

C

C

OH OH


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O

C C

C C

C

CO

C C

C C

C

C

O

H2O


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O

C C

C C

C

CO

C C

C C

C

C

O

A disaccharide1,4 glycosidic bond

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Polysaccharides

Polymers formed from manymonosaccharides

Three important examples:o Starcho Glycogeno Cellulose


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StarchInsoluble store of glucose in plantsformed from two glucose polymers:

Amylose

-glucose

1,4 glycosidic bondsSpiral structure

Amylopectin

-glucose

1,4 and some 1,6glycosidic bondsBranched structure


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Glycogen

Insoluble compactstore of glucose inanimals

-glucose units 1,4 and 1,6

glycosidic bonds

Branched structure


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Cellulose

Structural polysaccharidein plants

-glucose

1,4 glycosidic bonds H-bonds link adjacent

chains

O

O

O

O

O


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Lipids

Made up of C, H and O Can exist as fats, oils and waxes They are insoluble in water

They are a good source of energy(38kJ/g)

They are poor conductors of heat

Most fats & oils are triglycerides


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Triglycerides

Formed by esterification a condensation reaction between 3

fatty acids and glycerol:

Glycerol

H

C

H C

C

H

H

H

H

O

O

O


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Fatty acids Carboxyl group (-COOH)

attached to a long non-polarhydrocarbon chain (hydrophobic):

H

H

C

H

H

C

H

H

C

HC

O

O

HC

H

H

C

H

H

C

H

H

C

H

H

A saturated fatty acid (no double bonds)


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HH

C

O

O

H

C

H

H

C C

C C H

C

H

H

C

H

H

A polyunsaturated fatty acid

C

O

O

H

C

H

H

CH

H

CH

H

C

H

C

H

H

CH

H

C

H

H

A monounsaturated fatty acid

H H


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Esterification

H

C

H C

C

H

H

H

H

O

O

OC

O

O

H

C

H

H

C

H

H

C

H

H

C

H

H

Glycerol Fatty acid


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Esterification

H

C

H C

C

H

H

H

H

O

O

OC

O

O

H

C

H

H

C

H

H

C

H

H

C

H

H

Glycerol Fatty acid


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Esterification

H

C

H C

C

H

H

H

H

O

O

OC

O

O

H

C

H

H

C

H

H

C

H

H

C

H

H

Glycerol Fatty acid


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Esterification

H

C

H C

C

H

H

H

H

O

O

OC

O

O

H

C

H

H

C

H

H

C

H

H

C

H

H

Ester bond

water


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Esterification

This happens three times to form atriglyceride:

glycerolfatty acids


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Phospholipids

One fatty acid can be replacedby a polar phosphate group:

glycerolHydrophobic fatty acids

hydrophilicphosphate


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Functions of lipids

Protection of vital organs To prevent evaporation in plants &

animals

To insulate the body They form the myelin sheath around

some neurones

As a water source (respiration of lipids) As a component of cell membranes

P t i


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Proteins

Made from C H O N & sometimes S

Long chains of amino acids Properties determined by the aa

sequence

Amino acids

H

C

H

N C

H

H

O

O

R

~20 aa Glycine R=H Alanine R=CH3 amine

carboxyl


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Peptide bonding

HC

H

N C

HH

O

O

R

HC

HN C

HH

O

O

R


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Peptide bonding

HC

H

N CH

H

O

O

R

HC

HN C

HH

O

O

R


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Peptide bonding

H

C

H

N CH

H

O

O

R

HC

HN C

HH

O

O

R


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Peptide bonding

C

H

N CH

H

OR

HC

HN C

H

HO

H

O

O

R

water

Peptide bond

A condensation reaction


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Peptide bonding

C

H

N C

HH

OR

HC

HN C

H

O

O

R

A dipeptide


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Primary structure

The sequence of aa is know as theprimary structure

The aa chain is a polypeptide

Secondary structure

H-bonding forms between theCOOHand the -NH2 of adjacent aa This results in the chains folding:


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Secondary structure

-helix -pleated sheet


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Tertiary structure

Bonding between R-groupsgives rise to a 3D shape

H-bonds =O HN-

Ionic bondsNH3-COO-

Disulphide bridge

--CH2S-SCH2-

affected by temp & pH

affected by pH

affected by reducing agents


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Quaternary structure

Some proteins havemore than onepolypeptide chain

Each chain is heldtogether in a precisestructure

eg Haemoglobin


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Types of proteins

Fibrous proteinso e.g. collageno Insolubleo

structural

Globular proteinso e.g.enzymes

o Solubleo 3D shape


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Nucleic acids

DNA & RNA Made up of nucleotides:

phosphate

pentose sugar

base


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Nucleotides

2 types of base:

Pyrimidines -o Cytosine Co Thymine T

PurinesoAdenine Ao Guanine G


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Complimentary base pairing

Adenine will only bind with Thymine Cytosine will only bind with Guanine

T C GA


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DNA structure

nucleotide

Condensationpolymerisation of the

deoxyribose nucleotides

Replication


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Replication

During cell division the DNA mustreplicate

The DNA double helix unwinds The exposed bases bind to free floating

nucleotides in the nucleoplasm DNA polymerase binds the

complimentary nucleotides

Replication issemiconservative


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The genetic code

The sequence of nucleotide basesforms a code

Each code word has three letter a

triplet code Each codon codes for a specific amino

acid e.g:o GGG = prolineo CGG = glycineoATG = tyrosineoACT = stop (no amino acid)

Protein synthesis


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Protein synthesis

The DNA codes for

proteins A copy of DNA

(mRNA) is made in

the nucleus(transcription)

The mRNA is usedto make a protein(translation) in thecytoplasm

Transcription


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Transcription

The DNA polymerase

unwinds the DNA Free nucleotides join

onto complimentary

bases RNA polymerase links

adjacent nucleotides The completed mRNA

moves out of thenucleus

Transcription


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Transcription


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Amino acid activation

transferRNA:

tRNA binds onto aspecific amino acid


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Translation

A second tRNA brings another aa The two aas bind The process repeats


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Translation

A polypeptide chain forms Eventually a stop codon is reached

Th H G P j t


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The Human Genome Project

A multinational project aimed at sequencingthe entire human genome Visit the Human Genome Web site:

www.ornl.gov/hgmis/project/about.html

www.sanger.ac.uk

A k l d t
http://personal.tmlp.com/Jimr57http://personal.tmlp.com/Jimr57http://personal.tmlp.com/Jimr57


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Acknowledgements

Animated cell models used by kind permissionof The Virtual Cell website:

Feel free to use this presentation for

educational non-profit making purposes.

Q i


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Quiz

1. Which of the following is not animportant property of water

1.Its polar nature

2.Its low specific heat capacity3.Its high latent heat of vaporisation4.Its low density in solid form

Q i


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Quiz

2. The general formula for amonosaccharide is:

1.(CH2O)n

2.(CHO)n3.C(H2O)n4.CnH2On

Q i


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Quiz

3. Sucrose is made up of1.glucose + fructose2.glucose + galactose

3.glucose + glucose4.galactose + fructose

Q i


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Quiz

4. Amylopectin is made up of:1.-1,4 glycosidic bonds2.-1,4 & -1,4 glycosidic bonds

3.-1,4 & 1,6 glycosidic bonds4.-1,4 & 1,6 glycosidic bonds

Quiz


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Quiz

5. Formation of a triglyceride does NOTinvolve:

1.A condensation reaction

2.Esterification3.Polymerisation4.A reaction between 3 fatty acids &

glycerol

Quiz


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Quiz

6. The general formula of a saturatedfatty acid is:

1.CnH2nO2

2.Cn(H2O)n3.(CH2O)n4.(CH2)nO

Quiz


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Quiz

7. Which of the following is notresponsible for a proteins tertiarystructure

1.ionic bonding2.covalent bonding3.hydrogen bonding4.disulphide bonding

Quiz


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Quiz

8. Which of these is not an amino acid:1.alanine2.cysteine

3.glycine4.cytosine

Quiz


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Quiz

9. Which process involves tRNA:1.transciption2.translation

3.DNA replication4.gene mutation

Quiz


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Quiz

10. The formation of RNA does notinvolve:

1.ribose sugar

2.thymine3.removal of water4.phosphate

Answers


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Sorry, that is not the correct answer

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Thats right water has a high specificheat capacity

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Thats right


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Thats right



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Thats right


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Thats right


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Thats right, cytosine is an organic base



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unit 1.1 molecules

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