Topic 1A - Biological Molecules

Carbohydrates
1. Most cabrohydrates are POLYMERS (Large complex molecules made by long chains of monomers joined together)
  1. MONOMERS are small basic units
2. The monomer they are made from are MONOSACCHARIDES
  1. Glucose is a hexose sugar with 6 monosaccaride units. There are 2 times of glucose alpha glucose and beta glucose
    1. There are ISOMERS (molecules with the same molecular formula as eachother but connected in different ways)
3. CONDENSATION REACTIONS join monosaccharides together to form a new chemical bond and a water molecule is RELEASED
  1. Monosaccharides are joined together by condensation reactions forming a GLYCOSIDIC BOND between them when water is released - A DISSACHARDIE if formed when 2 monosacchardies join together
    1. Polymers can be broken into monomers by a HYDROLYSIS REACTION which breaks chemical bonds by ADDING WATER
4. a glucose + a glucose = Maltose
5. glucose + fructose = sucrose
6. glucose + galactose = lactose
7. Benedict's test for sugar
  1. REDUCING SUGARS include all monosacchardies & maltose & lactose
    1. Add benedics regent (blue) to a sample and boil it in a hot bath
      1. If the tests positive it wll form a coloured precipitate going from BLUE - GREEN - YELLOW - ORANGE - RED the higher the concentration, the further the colour change
  2. If the result is negative you use a NON REDUCING SUGARS TEST to test sucrose
    1. You must get them into their monosaccharides, you do this buy adding HCL and heat it in a water bath. You then dilute it using sodium hydrogen carbonate
      1. You then carry out the previous test, if it chanes colour, a reducing sugar is present. If it remains blue it doesn't include a sugar
8. POLYSACCHARDIES are lots of MONOSACCHARIDES joined together by glycosidic bonds
9. STARCH (Main energy storage in plants)
  1. cells get energy from glucose, plants store excess as glucose - when a plant needs more energy it breaks don starch to produce glucose
    1. Starch is a mixture of two pollysacchardides of alpha glucose - AMYLOSE & AMYLOPECTIN
      1. AMYLOSE - LONG, UNBRANCHED chain of a glucose. COILED structure means its COMPACTS and GOOD FOR STORAGE a you can fit more in a small space
        AMYLOPECTIN - LONG, BRANCHED chain of a glucose. Side branches allow enzymes to break down the molecules to release glucose quickly & break glycocidic bonds
        Starch is INSOLUBLE in water & so DOESN'T effect WATER POTENTIAL, so DOESN'T CAUSE OSMOSIS and so if GOOD FOR STORAGE
        IODINE TEST for STARCH - add iodine and if the solution turns bluey/purple STARCH IS PRESENT
10. GLYCOGEN (main energy storage in animals)
  1. Animals get energy from glucose, they store glucose as GLYCOGEN (another a glucose polysaccharides)
    1. similar to amylopectin but MORE SIDE BRANCHES this means glucose can be RELEASED QUICKLY
      1. Its also COMPACT so good for STORAGE
11. CELLULOSE (major component to plants cell walls)
  1. LONG, UNBRANCED b glucose
    1. When b glucose molecules bond they form straight cellulose chains
      1. These are joined by HYDROGEN BONDS to form strong fibres called microfibrils. This provides the cell with STRON STRUCTUAL SUPPORT
Lipids
1. TRYGLICERIDES (used as ENERGY STORAGE molecules)
  1. 1 GLYCEROL & 3 FATTY ACIDS
    1. Fatty acids have long tails made of hydrocarbons. The TAILS are HYDROPHOBIC (repel water) this makes tails insoluble in water. The HEADS are HYDROPHILIC
      1. Tryglycerides are formed by CONDENSATION REACTIONS - when the water is released an ESTER BOND IS PRODUCED
      2. There are 2 different types of fatty acids, UNSATURATED & SATURATED - this depends on the 'tails'
        SATURATED fatty acids DONT have DOUBLE BONDS between carbon atoms
        UNSATURATED fatty acids have atlleast one DOUBLE BONDS between carbon atoms
  2. The long chain of hydrocarbon tails contain lots of chemical energy. - lots of energy is released when they break down because of this lipids contain twice the amount of energy than carbohydrates
    1. theyre INSOLUBLE so DONT effect WATER POTENTIAL & cause water to enter by osmosis.
2. PHOSPHOLIPIDS - make up the bilayer of the cell membrane (Controls what goes in & out)
  1. Found in the cell membrane
  2. 1 GLYCEROL,, 2 FATTY ACIDS & 1 PHOSPHATE GROUP
    1. The phosphate group is HYDROPHILIC and the fatty acids tails are HYDROPHOBIC
  3. Form a double layer because the hydrophilic heads face out and the hydrophobic tails in
    1. Water soluble substances can't easily pass through, so the membrane acts as a barrier
Proteins
1. The monomer of protein is amino acids
  1. A dipeptide is formed when two amino acids join together
    1. A polypeptide is formed when two or more amino acids join together
      1. Proteins are made up of one or more polypeptides
2. Amino acids have the same general strucure. A CARBOXYLL GROUP -COOH, AMINO GROUP NH2 & a Carbon containing R GROUP
  1. All living things share a bank of only 20 amino acids, the only difference between them is whats in the R group
3. Amino acids are linked together by condensation reactions to form polypeptides. A molecule of water is released. The bonds between are called PEPTIDE BONDS
4. 4 structural levels
  1. PRIMARY STRUCTURE - sequence of AMINO ACIDS in a POLYPEPTIDE CHAIN
  2. SECONDARY STRUCTURE - Hydrogen bonds are formed between the amino acid in the chain. This makes the structure COIL into an ALPHA HELIX or FOLD into a BETA PLEATED SHEET
  3. TERTIARY STRUCTURE - coiled of folder chain is often COILED OR FOLDED FURTHER. more bonds are formed including HYDROGEN BONDS AND IONIC BONDS. DISULFINE BONDS are also formed where two amino acids CYSTIENE come cllose. Proteins with a single polypeptide chain, this is often THE FINAL 3D STRUCTURE
  4. QUARTANERY STRUCTURE - some proteins are made of many polypeptide chains held together., the quartenary structure is the way these polypeptide chains are arranged.
5. Functions
  1. ENZYMES - roughly sherical due to the tight folding of polypeptide chains. Theyre soluble and often have a role in metabolism (e.g some enzymes break down large food molecules, others help to make large molecules)
  2. ANTIBODIES - involved in immune response. made of two short and two long polypeptide bonds joined together.
  3. TRANSPORT PROTEINS - (eg channel proteins in the cell membrane) channel proteins contain hydrophobic and hydrophilic amino acids which cause proteins to fold up and cause a channel
  4. STRUCTUAL PROTEINS - Physically strong. Consists of long polypeptide chains lying parallel to eachother. these include kollagen (found in connective tisue) and keratin found in hair and nails
6. Biuiret test for proteins
  1. 1) The test solution needs to be alkaline & so first need to add sodium hydroxide solution
  2. 2) You then add a few drops of copper sulfate solution, if protein IS PRESENT it will turn PURPLE. If protein ISN'T PRESENT the solution will STAY BLUE
Enzyme Action
1. BIOLOGICAL CATALYSTS THAT SPEEDS UP A REACTION WITHOUT BEING USED UP
2. Enzymes catalyse metabolic reactions, at cellular level (respiration) and for the organism at a whole level (eg digestion)
3. Enzymes can effect STRUCTURE of an organism (eg production of collagen) and FUNCTION (eg respiration)
4. Enzyme action can be INTERCELLULAR (inside the cell) or EXTRACELLULAR (outside the cell) ENZYMES ARE PROTEINS
5. HIGHLY SPECIFIC DUE TO TERTIARY STRUCTURE
6. Enxymes have an ACTIVE SITE which has a specific shape. The active site is part of the enzyme where the substrate binds to
7. ACTIVATION ENERGY - the amount f energy that needs to be suplied for the reaction to start - often provided as heat
  1. ENZYMES LOWER ACTIVATION ENERG, this means reactions can take place at a lower temperature, this speeding up the rate of reaction
    1. when a substrate fits an active site it forms an enzyme-substate complex. If two substartes need to be JOINED the enzyme holds them together so they can bond more easily
      1. If the enzyme is catalysing a breakdown, fittin into the active site puts a strain on the bonds so break up more easily
8. Lock & Key method
  1. Enzymes only work with substrates that fit their active sites, scietists came up with the lock & key model. where the substrate fits into the enzyme the same way as a key
  2. New evidence shows that the enzyme-substrate complex changes shape slightly to complete the fit., scientists then came up with the induce fit model
    1. The INDUCED FIT MODEL explains why enzymes are so specific. to substrates. Substrates don't only have to be the right shape to fit into the active site, the active site also has to change shape aswell
9. Enzymes have TERTIARY STRUCTURES
  1. 1) Enzymes are very specific, they often only catalyse one reaction eg sucrase only breas down sucrase this is because only one complementory substrate will fit
    1. 2) The active sites shape is determined by its tertiary structure which is dtermined by its primary structure. Each enzyme has a different tertiary stucture, so a different active site.. If a substrate doesnt match the active site, the substance wont be formed and reacton wont be cataylsed
      1. 3) If the tertiary stucture is changed the shape of the active site will change, This means substrates wont fit and the enzyme will no longer be able to carry out its function
        4) Tertiary structure can be changed to to pH or temperature. The primary structure is determined by a gene, if a mutation occurs it could change the tertiary stucture of the protein produced
Factors effecting enzyme activity
1. Temperature
  1. The ROR INCREASES when TEMP INCREASES. MORE HEAT = MORE KINETIC ENERGY, so molecules move faster. this makes enzymes MORE LIKELY to collide with molecules.
  2. If the TEMP gets TOO HIGH the reaction STOPS. This is because the rise in temp makes enzymes VIBRATE MORE.. If the temperature gets too high the vibrations BREAK BONDS that hold the enzyme together. The ACTIVE SITE SHAPE CHANES and substrates can no longer fit. The enzyme is then DENATURED
2. pH
  1. All enzymes have an optimum pH, most work best at 7 (neutral) nut some such as pepsin found in the stomach prefer acidic conditions - pH 2.. Above & below the optimum pH the hydrogen and hydroxide found in acids and alkalies break the ionic & hydrogen bonds that hold the tertiary structure in place. This denatures the enzyme
3. Enzyme concentration
  1. The MORE ENZYMES there is in a solution, the MORE LIKELY A SUBSTRATE WILL COLLIDE, so and INCREASED CONCENTRATION INCREASES ROR
    1. But, if the SUBSTARTE IS LIMITED, there becomes a point that no matter the amount of enzymes there are no reactions avaliable and so no further effects
4. Substrate concentration
  1. The HIGHER the SUBSTRATE CONC the HIGHER the ROR. This means more substartes will collide with enzymes active sites more often. This is only true up to the point of SATURATION where by the active sites of enzymes are all used up sp increasing concentration wont make a difference
    1. substrate concentration decreases within time unless more substrates are added. so if no variables are changed the ROR will decrease.
5. Competitive Inhibitors
  1. 1) Competitive inhibitors have similar shapes to that of the substrate, they compete with the substrate molecules to bind to the active site but NO REACTION
    1. 2) They BLOCK the active site so NO substrate molecule can fit. If theres A HIGH CONC of INHIBITORS it'll take up nearly all the active sites & hardly any of the substrates will get to the enzyme. But if theres a HIGHER CONC of SUBSTRATE then the chnaces of getting to an active site before inhibitors increase
6. Non-Competitive Inhibitors
  1. 1) Non competitive inhibitors BIND TO ENZYMES AWAY FROM THEIR ACTIVE SITES. This causes the ACTIVE SITE TO CHANGE SHAPE so molecules can no longer bind to it
    1. 2) They don't COMPETE with the substate molecule, to bind to the active site because they are a different shape. INCREASING SUBSTRATES WONT INCREASE ROR as enzymes will still be inhibited

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Topic 1A - Biological Molecules

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	Created by Lauren Jane Speed over 8 years ago