chap 4 - marcomolecules

8/14/2019 Chap 4 - Marcomolecules

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CHAPTER 4

CELLULAR CHEMICAL COMPOUNDS


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Cellular chemical compounds

Four main classes of large biological molecules:

carbohydrates, lipids, proteins and nucleic acids

also called macromolecules

They are chain-like molecules called polymers : a

long molecules consisting of many similar or identical

building blocks linked by covalent bonds.

The repeating units that serve as the building blocks

of a polymer are small molecules called monomers.


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Carbohydrates

The most important source of energy in a cell

General formula : CnH2n On

Consists of carbon, hydrogen and oxygen 1:2:1

Include both sugars and polymers of sugars

Simplest carbohydrates : monosaccharides

Double sugars : disaccharides consisting of two

monosaccharides joined by a condensation reaction

Macromolecules : oligosaccharides consisting two to tenunits of monosaccharides

polysaccharides - consisting more than ten

units of monosaccharides


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Monosaccharides

Few groups: trioses (C3H6O3), pentose (C5H10 O5) and

hexoses (C6H12 O6)

Example : Hexose - Glucose (C6H12 O6)

Act as reducing agents in Benedict and Fehling Tests.

2 groups : aldose and ketose depending on the location

of the carbonyl group

Example : Glucose is an aldose and fructose is a structural

isomer of glucose is a ketose

Characteristics : sweet, water-soluble and can crystallize


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Oligosaccharides

Consists of two or more units of monosaccharides

Disaccharide (important oligosaccharides)

Consists of two monosaccharides joined by a glycosidic linkage a

covalent bond formed between two molecules by a condensation

reaction

Example:

Glucose + glucose Maltose(Malt sugar in brewing beer)

Glucose + fructose Sucrose(Table sugar)

Glucose + galactose Lactose(sugar in milk)

Characteristics : sweet, water-soluble and can crystallize


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Condensation reaction to form disaccharide - sucrose

+ H2O


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Polysaccharides

Macromolecules, polymers with a few hundred to

a few thousand monosaccharides joined by

glycosidic linkages through condensation

reaction

General formula : (C6H12 O6)n

Serve as storage material, hydrolyzed to provide

sugar for cells and building material

Characteristics : not sweet, insoluble in water

and cannot crystallize


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Starch

Storage in plants. Consists entirely of glucose

monomers. Plants store starch as granules within

cellular structures called plastids which include

chloroplasts.


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Glycogen

Similar to amylopectin but more extensively

branched. Storage polysaccharide in human andother vertebrates mainly in liver and muscle cells.


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Protein

Consists of C, H, O and N and occasionally S made up of thousands of polypeptides chains

Basic unit for polypeptide is amino acid connected bypeptide bonds

Amino acid monomers side chain

R carbon

H O

N C C

H OH

amino H carboxylgroup group

the physical and chemical properties of the side chain

determine the unique characteristics of a particular amino


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Functions of protein:

a. Building new tissues and replacing dead, injuredor damaged tissues

b. Producing enzymes, antibodies, hemoglobin,

carotene and hormones

c. Produce energy by breaking down protein to

carbohydrates

d. Forming muscles

Sources of protein:

Meat, eggs, milk, fish and beans


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Formation of Amino

acid polymers

Condensation

H

H

OH

OH


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Level of Protein Structure

The Primary Structure of Protein

Example : Transthyretin a

globular protein found in the

blood that transport vitamin A

and a particular thyroid hormonethroughout the body

Four identical polypeptide chains

make it composed of 127 amino

acids


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The Secondary Structure of

Protein

Composed of coils andfolds of polypeptide protein

Hydrogen bonds linked the

repeating constituents of

the polypeptide backbone. Two types:

helix human hair pleated sheet spider

silk


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The Tertiary Structure of

Protein

Holds by a few type ofbonds:

Hydrophobic

interaction

Van der Waals

interaction

Ionic bond

Disulfide bridge

Example:Cytokines, Interleukins,

Human growth

hormones


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The Quaternary Structure of Proteins

Include overall protein structure that results from the

aggregation of these polypeptide subunits Example :

Hemoglobin : consists of four polypeptide subunits, two of

one kind ( chains) and two of another kind ( chains)


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Review: the four levels of protein structure


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Lipid

Consists of C, H and O and sometimes P

Types of lipid : fats, phospholipids and steroids

Characteristics : insoluble in water but soluble in organic

solvent; at room temperature, lipid exists in two forms: liquid

(oil) and solid (fat)

Fats

Form from smaller molecules by dehydration reactions

Constructed from glycerol and fatty acids

Fat molecule = three fatty acids join to a glycerol (ester

linkage)

Fat is also called triacylglycerol : three fatty acids + one

glycerol


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Fatty acids vary in length and in the number and locations of

double bonds

2 types : saturated and unsaturated fats

Saturated fatty acid : No double bonds between carbon atoms

composing the chain, it is saturated with hydrogen

Unsaturated fatty acid : has one or more double bonds, form

by the removal of hydrogen atoms from the carbon skeleton


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Saturated fat

Mostly animal fats

Solid at room temperature Example : butter

Unsaturated fat

Mostly from plants and fishes

Liquid at room temperature

Example : Olive oil, cod liver oil

The kinks where the cis double bond are located

prevent the molecule from packing closely enough

to solidify at room temperature


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Function of fats:

a. Release twice the energy for each gram ofburned fat, compared to carbohydrates.

b. Act as heat insulators, for example adipose

tissue under the skin

c. Provide protection against injuries or

concussion to internal organs for example fats

around kidneyd. Act as the soluble site for fat-soluble vitamins

like vitamins A, D, E and K.


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Power from animal fat, soybeans, or other forms of biodiesel fuel

Designed by Craig Loomes Design Group Ltd


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Phospholipids

Similar to fat but only has two fatty acids attached to glycerol

The third hydroxyl group of glycerol is joined to a phosphate

group which has a negative electrical charge

Additional small molecules usually charged or polar can be

linked to the phosphate group to form a variety of phospholipids


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Nucleic Acid

Two types of nucleic acids : deoxyribonucleic acid (DNA) and

ribonucleic acid (RNA)

These molecules enable living organisms to reproduce their

complex components from one generation to the next

DNA provides directions for its own replication, directs RNAsynthesis and control protein synthesis

DNA is the genetic material that organisms inherit from their

parents

Each chromosome contains one long DNA molecule

DNA encoded the information that program all the cells

activities


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The human genome has

approximately 3 billion

base pairs of DNA

arranged into 46chromosomes (23 pairs of

chromosomes including a

pair of sex chromosome)

DNA was first isolated by

the Swiss physician

Friedrich Miescher in 1869

In 1953, James Watson

and Francis Crick

suggestedthe first

accurate model of DNA

structure


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The Structure of Nucleic Acids

Nucleic acids are macromolecules that exists as

polymers called polynucleotides

Each polynucleotides consists of monomers called

nucleotides

Nucleotides composed of three parts :a nitrogenous base a

pentose (five-carbon sugar)

a phosphate group

Nucleotides are joined by covalent bonds called

phosphodiester linkage

Nucleotide monomers


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Nucleotide monomers

Phosphodiester linkage


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Nucleotide Polymers

Nucleotides are joined by covalent bonds called phosphodiester

linkage between the OH group on the 3 carbon of one nucleotideand the phosphate on the 5 carbon of the next

The two free ends of the polymers : phosphate attached to a 5

carbon (5 end) and a hydroxyl group on a 3 carbon (3 end)

5C

3C

5C

3C

Phosphodiester

linkage


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Base pairing:


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Base pairing:

In DNA

Adenine(A) Thymine(T)

Guanine(G) Cytosine(C

In RNA

Adenine(A) Uracil (U)

Guanine(G) Cytosine(C


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Differences between DNA and RNA

Characteristics DNA RNA

1. Pentose group(sugar)

Deoxyribonucleicacid Ribonucleic acid

2. Nitrogenousbase

Adenine, Thymine,Guanine and

Cytosine

Adenine, Urasil,Guanine and

Cytosine3. Structure Longer chain,

double strandedShorter chain, canbe either double(only virus) or singlestrand

Urasil replace Thymine in RNA; but the other nitrogen bases

no changeUrasil = un-meth lated form of Th mine


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Functions of DNA/RNA

DNA:

Containing genetic information = genes

Synthesis of RNA as well

Genes have coding that help in protein synthesis by RNA

Can be inherited from parents to offsprings; genetic relationship

RNA:

Responsible for protein synthesis

RNA


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RNA

3

Transfer RNA

(tRNA)

3

Messenger RNA

(mRNA)

Ribosomal RNA

(rRNA)

Messenger RNA

Carries

informationspecifying amino

acid sequences of

proteins from DNA

to ribosomes

Transfer RNA

The RNA that moves

amino acids to theribosome to be

placed in the order

prescribed by the

messenger RNA

Ribosomal RNA

RNA that

constructed theribosomal subunit;

Helping in protein

synthesis

chap 4 - marcomolecules

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