IB Biology Topic 2 : Molecular Biology

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How many bonds can carbon make
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carbon can make four covalent bonds
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Four most common compounds
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– carbon -hydrogen -nitrogen -oxygen
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what is life based on
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carbon compounds
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metabolism
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metabolism- chemical processes in the body, synthesis & breakdown of substances in living organisms. anabolism- the synthesis of complex molecules (simple to complex) (condensation reaction) catabolism- the breakdown of complex molecules into simpler macromolecules (hydrolysis)
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Importance of the artificial creation of urea
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vitalism – states that organic compounds can come from living things, so the creation on urea in a lab disproved this
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international problems with water
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Water is not readily available to all countries. And even within countries there are distribution problems
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What does polar and non polar mean?
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polar means that there is a positive and negative charge and its an equal sharing of electrons, while non-polar means that there is an unequal sharing
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what kind bonds do water molecules make with each other
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hydrogen bonds
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Hydrogen Bonds
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Hydrogen bonds are the weakest because they are positive
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Covalent Bonds
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covalent bonds are strongest because they share a pair of electrons.
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Properties of Water
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Water molecules are polar (forms hydrogen bonds), because of the pull of electrons towards oxygen. Cohesion – when water sticks to itself. Allows surface tension to occur. Adhesion- when water sticks to to other substances. The ability for water to stick to the xylem of plants allows it to be transported throughout the plant. Thermal properties- water has the highest heat capacity of all liquids and so it takes a lot of energy before it will change temperature. It also has a high boiling point because it takes a lot of energy to break hydrogen bonds. This is helpful in sweating b/c the energy provided by the body causes one to sweat – hence the cooling affect.
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Hydrophobic
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– not attracted to water – insoluble in water
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Hydrophilic
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– attracted to water – dissolves well in water – form molecular bonds with water molecules
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What are the four main macromolecules?
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-lipids -carbohydrates -nucleic acids -proteins
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Carbohydrates
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– Sugars – Made of of C, H, and O – main functions are quick energy, storage, raw/structural material – Monosaccharides, disaccharides, polyssacharides
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Monosaccharides
Monosaccharides
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– sugars that consist of a single sub-unit (monomer) – only contains carbon, hydrogen & oxygen with a ration of 1:2:1 eg. glucose (C6H12O6) and fructose
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Disaccharides
Disaccharides
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– a pairs of monosaccharides linked together by condensation eg. maltose ( glucose + glucose – used for food when plants break down their starch stores), lactose ( glucose + galactose – nursing and milk), sucrose ( fructose + glucose – table sugar)
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Polysaccharides
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– complex carbohydrates – chain of many monosaccharides – extremely soluble so a good source of quick energy eg. starch, glycogen, chitin, and cellulose
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How are sugars classified?
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the number of carbons
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Lipids
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– carbon compounds – non polar hydrophobic organic molecules Types of lipids: – triglycerides (eg. fats & oils) – phosopholipids – steroids (eg. testosterone & estrogen)
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Function of lipids
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– twice as much energy as carbohydrates but a slower release – insulation – framework for cell membrane
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Health risks for trans/saturated fat
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– Trans fats increase the \”bad\” cholesterol which raises the risks of coronary heat disease. – Diets that are high in trans-fat unnecessarily increase the chance that you will consume more than your body needs, because they are energy dense.
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BMI Equation
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bmi = weight of body / (height in meters ^2)
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Fatty Acids
Fatty Acids
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Types: – Saturated: All atoms in the chain are connected by single bonds – Unsaturated: chain contains one or more double bonds – Monounsaturated: only one double bond – Polyunsaturated: two or more double bonds – Cis-unsaturated: H bonded to C on the same side of the double bond – Trans-unsaturated: H bonded to C on different sides of the double bond.
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Polypeptides
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– chain of amino acids – the amino acid sequence of a polypeptide is coded for by a gene. The DNA sequence determines the sequence of amino acids in the polypeptide. – a protein consists of either a single or multiple polypeptides linked together.
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Denaturation
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proteins have a delicate structure that can be damaged by substances or conditions: this is called denaturation – heat causes denaturation – change in pH causes denaturation
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Function of proteins
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wide range of functions Eg: – Rubisco is an enzyme that catalyses the photosynthesis reaction – Insulin is a hormone that lowers the body’s blood glucose concentration
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Enzymes
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– biological catalysts – they speed up chemical reactions and metabolism – a reactant is an enzyme catalysed reaction called a substrate -substrates bind to the active site of the enzyme and the products are released.
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Factors affecting enzymes
Factors affecting enzymes
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1) Temperature – temperature increases enzyme activity – when temperatures are high, enzymes are denatured and stop working. 2) pH – enzyme activity decreases pH decreases from optimum. – above a certain pH, the a;lalinity denatures the enzyme 3) Substrate concentration – at low substrate concentrations enzyme activity increases steeply – at high substrate concentrations, most of the active sites are occupied.
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Production of lactose free milk (for lactose intolerant people)
Production of lactose free milk (for lactose intolerant people)
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– lactose is the sugar in milk – it can be hydrolysed into glucose and galactose by the enzyme lactase
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DNA
DNA
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– nucleic acid – consist of nucleotides – nucleotide: sugar, phosphate, and nitrogenous base (bases: adenine, thymine, guanine, cytosine)
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Structure of DNA
Structure of DNA
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RNA
RNA
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– single stranded (DNA is double stranded) – thymine is replaced by uracil
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Proteome
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the combination of all proteins in an organism, everyone’s is unique
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Amino acids
Amino acids
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have a central carbon atom with 4 different atoms linked to it: – R group (R) – amine group (N – Hx2) – carboxyl group (C=o, C-OH) – hydrogen atom (H)
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Peptide bonds
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bonds that link amino acids to form polypeptides. you take way the OH and one of te H’s from the H2 of the amine group
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primary, secondary, tertiary, and quaternary
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1. order of amino acids 2. reactions with amino acids near each other 3. reacts with farther apart amino acids, the reaction of the R groups which them determines the quaternary structure 4. arrangement of multiple proteins
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The importance of the R group
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This group determines the function of the protein and thus instructs how the it will interact with other amino acids ( which instructs how the amino acid chains are folded)
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Activation energy
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the energy it takes to begin a reaction
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Active site
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the place where the substrate binds to the enzyme; where the reaction occurs

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