Biological Molecules 1.ppt

04/17/23 19:36 1

Nazabayev UniversityUPCSEBiology

Biological Molecules 1

Biomolecules 1 Pork Chop Willie 204/17/23 19:36

Molecules important in biology

Water Inorganic ions Carbohydrates Lipids Nucleic Acids Proteins

Chirality "handedness."

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Chirality in life

Thalidomide is a sedative drug that was prescribed to pregnant women, from 1957 into the early 60's.

It was present in at least 46 countries under different brand names. "When taken during the first trimester of pregnancy, Thalidomide prevented the proper growth of the foetus, resulting in horrific birth defects.


Why? The Thalidomide molecule is chiral.

There are left and right-handed Thalidomides, just as there are left and right hands.

The drug that was marketed was a 50/50 mixture.

One of the molecules, say the left one, was a sedative, whereas the right one was found later to cause foetal abnormalities.


Properties of water that make it an ideal transport medium

Water is unusual because it is a liquid at room temperature whereas other small molecules are gases. CO2, 02

Water is a polar molecule; it has an unevenly distributed electrical charge.

The two hydrogens are pushed into a V shaped molecule

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Hydrogen bonding

Positive end of the molecule is attracted to the negative ends of surrounding molecules

This hydrogen bonding holds the water molecules together and results in many of the properties of water


Dipoles and Hydrogen Bonds

Atoms in molecules are held together because they share electrons with each other.

A shared pair of electrons forms a covalent bond - for example in a water molecule, two hydrogen atoms each share a pair of electrons with an oxygen atom.


Solvent properties of water

Many chemical dissolve easily in water, allowing vital chemical reactions to take place

Chemicals can move about freely in aqueous environment

Chemicals can react with water itself e.g. hydrolysis and condensation reactions



Dissolved substances can be transported around the body in blood and lymph in animals and in plants through xylem and phloem.

Ionic molecules e.g.(NaCl) dissolve easily in water forming ions Na+ which are attracted to Cl-



Polar molecules dissolve easily in water. Their polar groups e.g. –OH group in

sugars or the amine group –NH2 in an amino acid, become surrounded by water and go into solution.

Polar substances are said to be hydrophilic (water loving)



Non –polar, hydrophobic substances such as lipids, do not dissolve in water.

To enable transport in blood, lipids combine with proteins to form lipoproteins


Thermal properties of water

Specific heat capacity of water (the amount of energy in joules required to raise 1 cm3 (1g) of water by 1 oC, is very high

Because in water a large amount of energy is required to break the hydrogen bonds

Water warms up and cools down slowly Avoids rapid changes in internal

environment


Carbohydrates Cx(H2O)n

SugarsMonosaccharides: single unitsDisaccharides: two single sugarsPolysaccharides: Long staight or branched chains


Monosaccharides (C6H12O6)

Hexose sugars

GlucoseGalactoseFructose


Monosacharides

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Monosaccharides


Disaccharides (C12H22O11)

Sucrose (glucose+fructose)Maltose (glucose+glucose)Lactose (glucose+galactose)


Condensation reaction to form a Dissacharide

Biomolecules 1 Pork Chop Willie 21

Glycosidic link split by Hydrolysis


Polysaccharides

Polymers made up from simple sugars joined by glycosidic links into long chains.

Three main types Starch and Cellulose in plants and

glycogen in animals


Starch Mixture of two molecules: Amylose and

amylopectin Amylose straight chain glucose molecules

with 1,4 glycosidic. Position of bond causes the chain to coil into spiral shape

Amylopectin polymer of glucose with branches, 1,6 glycosidic link holds each side branch onto the main chain


Starch


1,4 and 1,6 glycosidic links


Glycogen

Bacteria, fungi and animals store glycogen instead of starch

Polymer composed of glucose Numerous side branches (1,6 link)that

can be rapidly hydrolysed giving easy access to stored energy

Humans store glycogen in Liver and muscles


Cellulose

Dietary fibre Non starch polysaccharide Straight chains (1,4 links only) Gives strength to cell walls of plants Made up of β-glucose molecules


In Cellulose neighbouring chains of glucose molecules are linked by

hydrogen bonds to form microfibrils


Lipids (Fats, oils, waxes)

Enhance flavour and palatability of food Supply twice the energy of carbohydrates 37KJ per gram of food Insoluble in water Soluble in ethanol All Lipids are hydrophobic: that’s the one

property they have in common. Lipids found in every type of cell


Glycerol and fatty acids


Formation of a triglyceride


Saturated and unsaturated fats


Saturated Lipids


Saturated Fat

Eating too much saturated fat (like the kind found in the English breakfast) can cause high cholesterol.

You will find this unhealthy fat in foods that come from animals.

e.g. Beef, pork, veal, milk, eggs, butter, and cheese contain saturated fat.

Packaged foods that contain coconut oil, palm oil, or cocoa butter may have a lot of saturated fat.

You will also find saturated fat in stick margarine, vegetable shortening, and most cookies, crisps.


Where can you get saturated fats?


Unsaturated fats

Monounsaturated fats have one double bond between two carbon atoms in ach fatty acid chain

Polyunsaturated fats have a larger number of double bonds.


Unsaturated fats

Double bond cause kink in the hydrocarbon chain and prevents close packing.

Weak intermolecular bonds between unsaturated fats results in oils at room temperature.

Vegetable oils and fish good sources of polyunsaturated fats.


Unsaturated lipids


Trans Cis

Opposite sides

Same side

Straight Bent

Rare Common

Unsaturated fats

Cis double bonds bend carbon chains cis fatty acids are more bulky than trans fatty

acids Cis fatty acids have a lower melting point. Trans fatty acids behave more like saturated

fats than cis fatty acids Animals cannot metabolise trans fatty acids

fully


Cholesterol


Cholesterol

Vital component of cell membranes Steroid sex hormones(such as

progesterone and testosterone) and some growth hormones.

Bile salts formed from cholesterol Made in the liver from saturated fats Too high cholesterol can be bad


Sphingolipids

Fatty acids linked to Amine group

Important in cell membranes


Lipoproteins

Low density lipoprpoteins (LDL) Main cholesterol carrier in the blood Triglcerides from saturated fats combine with cholesterol Does not remove cholesterol from blood

High density lipoproteins (HDL)Combine with unsaturated fatsTransport cholesterol to liver


Biological Molecules 1.ppt

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