Molecular biology

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Vitalism theorem
theory falsified by the synthesis of artificial urea.Thought that living organisms could only be synthesised by living systems (needed a 'vital force')
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What are living organisms governed by?
The same chemical and physical forces as in non-living matter
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Molecular Biology
aims to explain living processes in terms of the chemical substances involved
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When was urea (CH4N2O), in human urine, discovered?
in the 18th century.
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When was Urea first artificially synthesised?
in 1828 by german chemist Fredrich Wohlen, using silver isocyanate and ammonium chloride. (1rst time organic compound was synthesised)
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a single part of an element (+ charged nucleus, - charged electrons)
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a group of two or more atoms held together by covalent bonds
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Base for molecules used by living organisms
carbon. Carbon atom forms 4 covalent bonds
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Intermolecular forces
bonds which are weaker than covalent bonds and form between molecules
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the web of all enzyme-catalysed reactions in a cell or organism
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the synthesis of complex molecules from simpler molecules.
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Anabolic reactions
condensation reactions (water is produced)
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the breakdown of complex molecules into simpler molecules.
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Catabolic reactions
hydrolysis reactions (water molecules are split)
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How are covalent bonds formed?
when 2 atoms share a pair of electrons.
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Properties of water molecules
they are polar and show dipolarity
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Hydrogen bond
when an intermolecular bond forms between the positive pole of one water mol and the negative pole of another
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What happens when a hydrogen bond is made and broken?
Made: energy is released, Broken:energy is used
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What is sweat and what is its purpose?
a coolant- evaporation of water from sweat removes heat from the body
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Boiling point of methane and water
methane:-160C, water:100C (heat energy needed to break hydrogen bonds)
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Melting point of methane and water
methane:-182C, water:0C (hydrogen bonds restrict movement of water molecules)
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Specific heat capacity of methane and water
methane: 2.2J per g perC, water: 4.2J per g perC (hydrogen bonds restrict movement-more energy stored by moving water mols than methane mols)
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Latent heat of vaporization of methane and water
methane: 760J/g, water: 2257J/g (heat needed to break hydrogen bonds)
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substances attracted to water and form intermolecular bonds w/ water.
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What do many hydrophillic substances do in water
dissolve (their ions or molecules are more attracted to water than each other)
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is NOT repelled by water, but water molecules are more attracted to each other than non-polar hydrophobic substances> they are insoluble in water
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Transport in blood via water (4)
1Sodium chloride- water soluble- transported in plasma as Na^+ &CI^- ions, 2Glucose and amino acids: polar- transported dissolved in the blood, 3Oxygen:non-polar- red blood cells needed w/ hemoglobin-oxygen binds to 4Cholesterol & fats-non-polar &
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Properties of water (4)
Cohesive, Adhesive, Thermal, Solvent
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water molecules cohere (stick to each other) because of hydrogen bonds that form between them (example:strong pulling forces sucking water in xylem vessels)
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The dipolarity of water molecules- makes them adhere to polar surfaces:hydrophillic (example:adhesive forces between water &cellulose in cell walls)
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Due to hydrogen bonding, water has high melting & boiling points, high latent heat of vaporisation & high specific heat capacity (example:creates coolant, sweat, temp change slow- stable habitat)
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Substance which dissolve in water due to its polarity, including those composed of ions or polar molecule (example:metabolic reactions)
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Condensation reaction
two molecules join together to form a larger molecule plus a water molecule
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a single sub-unit
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pair of monomers bonded together
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a long chain of monomers
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a chain of amino acids
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Peptide bond
The bond which links the amino acids together in a polypeptide chain
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The basic sub-units of carbohydrates
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Two monosaccharides linked together form...
a disaccharide + water
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a lipid molecule- fatty acids linked to glycerol by condensation reactions
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a lipid molecule made up of one unit of glycerol and three fatty acids via condensation &has 3 hydrocarbon tails (three water molecules are made as well)
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Hydroylsis reaction
large molecule broken down into smaller molecules (opposite of condensation) Water is used in this process (-H and -OH group split)
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a large molecule- many monosaccharides linked to a disaccharide: molecule of many sugars
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sugars that consist of a single sub-unit (monomer)- Contain atoms only of carbon, hydrogen & oxygen ration 1:2:1
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Chemical formula for Ribose
C5 H10 O5
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Chemical formula for Glucose
C6 H12 O6
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Sugars with double rinnged structures. Pairs of monosaccharides linked together by condensation
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Name three monosaccharides commonly used to make disaccharides
Glucose (glucose+glucose=maltose+H20) Galactose (glucose+galactose=lactose+H2O) & Fructose (glucose+fructose=sucrose+H2O)
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Two types of Carbohydrates
sugar- saccharides, starches- polysacchrides
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Types of starch (3)
Starch (energy-plants), Glycogen (energy-animals), Cellulose (structural polysacchride)
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Amylose chain
(hydrophillic) glucose molecules are unbranched and form helix
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Amylopectin chain
Glycogen. (hydrophillic) chain is branched & has more globular shape.
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Starch: where is it found, what is it used for, what are its advantages
.Found in leaves & seeds, Used as a storage compound, .Advantage-compact, doe not alter osmotic potential, easily hydrolysed
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Glycogen:where is it found, what is it used for, what are its advantages
.Found in animals (humans liver & muscles) and some fungi, Used as a storage compound, .Advantage-compact, doe not alter osmotic potential, easily hydrolysed
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Cellulose:where is it found, what is it used for, what are its advantages
.Found in plant cell walls (structural),links to glucose made by condensation raction-hydrogen bonds, unbranched chains of beta glucose, Advantage:high tensile strength gives support to cells
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Main types of lipids (3)
1)Triglycerides (fats &oils) 2)Phospholipids 3) Steriods
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Has 2 fatty acids linked to glycerol with a phosphate
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structure of four fused rings in their molecule. Cholesterol, progesterone, oestrogen and testosterone are all steroids
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How can a molecule be identified as a lipid?
If they have two or three hydrocarbon tails or the quadruple ring structure of steriods.
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How are hydrocarbons usually shown in molecular diagrams?
As zigzag lines
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Name the two components of a fatty acid
a carboxyl group that is acidic (-COOH) and an unbranched hydrocarbon chain (-CH2-[CH2]N-CH3)
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Types of Fatty Acids
Saturated & Unsaturated
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Saturated fats
(bad for health)all carbon atoms in the chain are connected by SINGLE covalent bonds> nom of hydrogen atoms bonded to the carbons cannot be increased
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Unsaturated fats
(better than saturated fats)contains one or more DOUBLE bonds between carbon atoms> more hydrogen could be bonded to the carbons if a double bond was replaced by a single bond
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only one double bond
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two or more double bonds
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Cis unsaturated
hydrogen bonds are bonded to carbon atoms on the SAME side of a double bond
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Trans unsaturated
hydrogen atoms are bonded to carbon atoms on the OPPOSITE side of a double bond
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Stores of energy (4)
Fats and oils (lipids) & glycogen or starch (carbohydrates)
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What is the long-term advantage to using lipids as opposed to carbohydrates regarding energy storage? (2)
1)energy released in cell respiration per gram of lipids is double that of carbohydrates 2) Fats form pure droplets in cell w/ no water associated (glycogen 2 grams of water)> lipids 6x more efficient in energy amount stored per gram of body mass
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Body Mass Index calculation (kg/m² )
BMI= mass in kilograms/(height in meters)²
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Body Mass Index
below 18.5> underweight, 18.5-24.9> normal weight, 25.0-29.9> overweight 30.0 or more> obese
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Health risks of Trans Fats
.Banned in some countries- correlation w/ coronary heart disease (CHD)>patients who died from CHD had fatty deposits in arteries which contained concentrations of trans-fats
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Saturated fatty
(in animal fats &some veg oils)- Correlation w/ CHD
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What does not fit the correlation between saturated fatty acids and CHD?
The Maasi of Kenya- diet of foods rich in saturated fats yet CHD is very rare
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How many different R-groups do amino acids have in most living organisms
twenty in the polypeptides synthesized
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consists of either a single polypeptide or more than one polypeptide linked together
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unbranched chain of amino acids
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all the proteins produced by a cell, a tissue or an organism- it is variable because different cells in an organism make different proteins
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Card 2


What are living organisms governed by?


The same chemical and physical forces as in non-living matter

Card 3


Molecular Biology


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Card 4


When was urea (CH4N2O), in human urine, discovered?


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Card 5


When was Urea first artificially synthesised?


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