Biological Molecules 1
Biological Molecules 1
Biological Molecules 1
UPCSE Biology
Biological Molecules 1
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Lipids
Nucleic Acids Proteins
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Chirality "handedness."
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.
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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.
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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
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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.
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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
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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-
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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)
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such as lipids, do not dissolve in water. To enable transport in blood, lipids combine with proteins to form lipoproteins
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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
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Carbohydrates Cx(H2O)n
Sugars Monosaccharides: single units Disaccharides: two single sugars Polysaccharides: Long staight or branched chains
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Monosaccharides (C6H12O6)
Hexose sugars
Glucose
Galactose
Fructose
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Monosacharides
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Monosaccharides
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Monosaccharides
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Disaccharides (C12H22O11)
Sucrose (glucose+fructose)
Maltose (glucose+glucose)
Lactose (glucose+galactose)
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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
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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
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Starch
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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
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Cellulose
Dietary fibre
Non starch polysaccharide Straight chains (1,4 links only)
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In Cellulose neighbouring chains of glucose molecules are linked by hydrogen bonds to form microfibrils
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Insoluble in water
Soluble in ethanol All Lipids are hydrophobic: thats the one
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Formation of a triglyceride
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Saturated Lipids
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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.
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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.
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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.
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Unsaturated lipids
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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
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Cholesterol
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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
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Sphingolipids
Fatty acids linked
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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 fats Transport cholesterol to liver
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