Four main types of bond
Covalent bonds, double bond, ionic bond and hydrogen bond
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It involves sharing electron pairs between atoms. e.g Carbon can form four covalent bonds with other carbon atoms or other atom types
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Exists where atoms share multiple electrons in order to stabilise (a double bond is just two covalent bonds)
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Always between 1 anion (non-metal) & 1 cation (metal). Don't share electrons but metal ion donates electron/s to non-metal ion to complete the outer energy level and stabilise the atom
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One of most important bonds-used to hold together individual monomers into larger groups (polymers)-Form where slightly +ve parts of a molecule meet slightly -ve parts of another-very weak but when there are loads, they are pretty strong together.
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What is a Carbohydrate made up of?
A carbohydrate is a biological molecule made of carbon, hydrogen and oxygen atoms
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What are carbohydrates used for in the body?
Energy source, energy storage or it has structural properties
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What is the formula for a carbohydrate?
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Simplest sugar - monosaccharide, monomer - C6H12O6 - first product of photosynthesis
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2 forms of Glucose?
alpha-glucose (hydrogen on top and hydroxyl on bottom) & beta-glucose(hydroxyl on top and hydrogen on bottom)
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2 monosaccharides polymerise (join together) and release water in the process - 2 alpha-glucose join to make maltose, held together by a glycosidic bond (C-O-C)
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A disaccharide splits by adding water to break or split the bond - produces 2 alpha-glucose.
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The energy store used in plants - made from 2 different molecules: 20% amylose (straight chain joined by glycosidic 1,4 bonds) and 80% amylopectin (branched chain - glycosidic 1,6 bonds and 1,4 bonds). Starch -broken down to be used in respiration
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Energy stpre in animals-glycosidic 1,4 chains are shorter and more 1,6 bonds per chain = molecules more compacted and complex.
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H on top, OH on bottom - forms starch (plants) and glycogen (animals) -used for storage.
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OH on top, H on bottom - forms cellulose (plants) - 1 long, straight chain - structural form. Every other beta-glucose flips 180 degrees to allow bonding of OH groups.
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Variable group that contains carbon, hydrogen and oxygen. Most common are fats, oils, waxes, steroids and phospholipids
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Lipid that covers fats and oils group - contain 6 oxygen atoms. One triglyceride molecule contains 3 fatty acids and 1 glycerol molecule
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Fatty acid molecule
2 parts: acid group (COOH) at one end & hydrocarbon chain at other end.
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contains 3 OH groups & is always the same in any triglyceride.
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3 fatty acid + 1 glycerol
3 fatty acids and 1 glycerol join in a condensation reaction - 3 water molecules released - bond between them is a O-C=O bond (ester bond) - This attaches 1 fatty acid to each carbon atom of glycerol molecule
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Form the basis of all biological membranes - structurally similar to triglycerides (glycerol & fatty acids (only 2)) - formed in condensation reaction. Head - hydrophilic & tail - hydrophobic
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Water-loving (phospholipid head)
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Water-hating (phospholipid tail)
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Type of lipid formed from 4 carbon-based rings. Small & hydrophobic - in all biological membranes (between fatty acid tails) - vital to living organisms so a lot of cells can make it (liver)
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Can cause health problems - hypercholesterolemia - genetic disorder where cells make and secrete cholesterol even though they have enough in the blood already
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Polymer - Made up of amino acids (individual monomers). Amino acids contain the elements carbon, hydrogen, oxygen and nitrogen, and some also contain sulphur
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Consists of an amine group, is basic and has the formula NH2
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vital to living organisms - reactant in loads of chemical reactions like photosynthesis and hydrolysis. Solvent so substances dissolve in it. Transports substances helps with temp control
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What do the hydrogen bonds in water do?
gives water a specific heat capacity (stops rapid temp changes in living organisms) and gives water a high latent heat of evaporation (A lot of energy used up when water evaporates - cools organisms)
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Makes it very cohesive (helps water to flow so it's good for transporting substances) and makes it a good solvent (because it's polar - positive end will be attracted to negative ion and vice versa
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What are proteins (polymers) made up of?
One of more polypeptides. Polypeptides = when more than 2 amino acids join together
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When 2 amino acids join together
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When more than 2 amino acids join together
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Bond joining amino acids together
Peptide bond forms when a molecule of water is released. C-N bond.
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Four structural levels of protein
Primary, secondary, tertiary, quaternary
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What is the primary structure?
The sequence of amino acids in the polypeptide chain
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What is the secondary structure?
Shows the Hydrogen bonds that form between the amino acids in the chain - Makes it automatically coil into an alpha helix or fold into a beta pleated sheet
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What is the tertiary structure?
When more bonds form between different parts of the polypeptide chain. If protein is made from only one polypeptide chain, this forms final 3D structure
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What is the quaternary structure?
Some proteins made from several different polypeptide chains held together by bonds - this structure is the way these polypeptides are assembles together - e.g haemoglobin made up of 4 polypeptide chains. - final 3D structure for most proteins
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Bonds in primary structure
Peptide bonds between amino acids
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Bond in secondary struture
Hydrogen bonds form between nearby amino acids - these bonds create alpha-helix chains or beta-pleated sheets
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Bonds in tertiary structure
Ionic interactions -weak attractions between -ve & +ve charges. Disulfide bonds, Hydrophobic & Hydrophilic interactions - hydrophobic groups clump together so get pushed to the outside. Hydrogen bonds
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Bonds in quaternary structure
Determined by tertiary structure - can be influenced by all bonds in tertiary structure which are?...
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2 examples of protein shapes
Collagen (fibrous protein) and Haemoglobin (globular protein)
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Fibrous protein, forms supportive tissue in animals so it needs to be strong - made of 3 polypeptide chains, tightly coiled together into a strong triple helix - chains interlinked by strong covalent bonds and minerals can bind to triple helix
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Globular protein - iron-containing haem group (binds to oxygen and carries round body) - Structure is curled so hydrophobic chains on outside - makes it soluble in water so good fro transport in blood
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Tough and rope-shaped. Tend to be found in connective tissue like tendons. E.g collagen (supportive tissue in animals)
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Round and compact, soluble and easily transported in fluids. E.g Haemoglobin (carries oxygen around the body)
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Biochemical tests for molecules
Benedict's test (sugars), iodine test (starch), biuret test (proteins), emulsion test (lipids) and colorimetry ( determine conc of a glucose solution
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For sugars - blue - Add to a sample & heat it (not boil) - if +ve, it will form a coloured precipitate (blue-green-yellow-orange-brick red)
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For starch - Add iodine dissolved in potassium iodide solution - if starch present, sample changes from browny-orange to dark blue-black colour.
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For proteins - needs to be alkaline (add few drops of sodium hydroxide solution), then add copper (II) sulfate and if protein present, purple layer forms. If no protein - solution stays blue
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For lipids - shake with ethanol then pour into water - if lipid present, solution will turn milky.
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What is DNA used for?
To store genetic information (instructions needed to grow and develop from a fertillised egg to a fully grown adult
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What is DNA made from?
It's a polynucleotide made from lots of nucleotides joined together
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What are nucleotides made up of?
A deoxyribose sugar, a phosphate group and a nitrogen-containing base - same sugar and phosphate but bases can vary.
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What are the four possible bases?
Adenine (A), thymine (T), cytosine (C) and Guanine (G)
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What are the purine bases?
Adenine and Guanine
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What are the pyrimidine bases?
Thymine and Cytosine
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What base joins to Adenine and how many hydrogen bonds are between them?
Thymine and there are 2 hydrogen bonds between them
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What base joins to Cytosine and how many hydrogen bonds are between them?
Guanine and there are 3 hydrogen bonds between them
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Complementary base pairing
Each base can only join one particular partner - G and C, A and T
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Similarities between RNA and DNA
Both contain sugar, nitrogen-containing base and phosphate, contains 4 diff bases and form a polynucleotide strand that is joined up between the sugar of 1 nucleotide & phosphate of the other
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Differences between RNA and DNA
Sugar in RNA nucleotides is ribose sugar (not deoxyribose), nucleotides form a single polynucleotide strand (not a double) and Uracil (pyrimidine) replaces Thymine as a base -pairs with Adenine in RNA
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Why is Self-replication important?
It's before cell division so each new cell has the full amount of DNA
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Stages of self-replication
Hydrogen bonds break (heliz unzips). Original strands act as templates for new strand and free-floating DNA nucelotides join to exposed bases. DNA polymerase joins nucelotides together. H bonds form between bases on original and new strand
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After self-replication, what does each new DNA molecule contain?
One strand from original DNA molecule and one new strand
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self-replication because half of the new strands of DNA are from original piece of DNA
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What does DNA contain?
Genes (instructions for proteins) - Diff proteins have diff no. and order of amino acids which determines order of amino acids in particular protein. Diff sequences of bases code for diff amino acids
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DNA is copied into RNA - Instructions (in DNA) are in nucleus and ribosomes (make proteins) are in cytoplasm but DNA is too large to get out of nucleus so sections of DNA are copied into RNA. RNA leaves nucleus & joins ribosome - makes proteins.
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Why is DNA and RNA vital for living organisms?
DNA contains all the genes which are instructions for proteins & RNA is used to get the information out of the nucleus to bind to ribosomes in the cytoplasm to make proteins
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What are enzymes?
Enzymes are biological catalysts which speed up chemical reactions - globular proteins & it's specific shape of active site is determined by tertiary structure.
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How does an enzyme work as a catalyst?
It reduces activation energy, often making reactions happen at a lower temp which speeds up the rate of reaction
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Lock and Key model
Enzymes only work with substrates that fit their active site - scientists realised it wasn't fully correct - evidence showed enzyme-substrate complex changed shape slightly to complete the fit.
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Induced fit model
Better theory than lock and key - helps to explain why enzymes are so specific and only bond to one particular substrate. Substrate doesn't have to be the right shape to fit, it has to make active site change shape
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Effect of temperature on enzyme activity
Rise in temp makes molecules vibrate more = more kinetic energy so faster the reaction. If temp gets too high - bonds break due to vibrations, active site changes shape and substrate no longer fits = denatured.
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Effect of pH on enzyme activity
Have an optimum pH - Pepsin works best at pH 2 as it's found in the stomach. Above & below optimum pH, H and OH ions found in acids and alkalis can mess up ionic and hydrogen bonds that hold tertiary structure in place = denatured.
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Effect of enzyme concentration on the rate of reaction
more enzymes = more chance of collisions = increases R.O.R. If amount of substrate is limited, there's a point when there's more than enough enzyme molecules to deal with all available substrate - no further effect
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Effect of substrate concentration on rate of reaction
higher substrate conc = faster the reaction = more collisions. Saturation point = there are so many substrate molecules that the enzymes have about as much as they can cope with (active sites are full) - makes no difference
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How to measure rate of an enzyme-controlled reaction
Measure how fast product of reaction appears or how fast the substrate disappears
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Cofactors & Coenzymes
a non-protein substance that binds to the enzyme to make it work.
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What are cofactors?
inorganic molecules - help enzyme and substrate bind together - don't directly participate in reaction so they aren't used up or changed.
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What are coenzymes?
Cofactors - organic molecules - participate in the reaction and are changed by it (second substrate basically) - often act as carriers, moving chemical groups between diff enzymes. Continually recycled during process.
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Similar shape to substrate & compete with it for active site but no reaction takes place - block active site so no substrate molecules can fit into it.
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Bind to enzyme away from it's active site - causes active site to change shape to substrate no longer fits. Don't 'compete' with substrate molecules because they're a diff shape.
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Enzyme inhibitors- causes damage, illness or death - Cyanide (irreversible-inhibits cytochrome c oxidase-stops cells respiring), Malonate (stops cell respiration) and Arsenic (inhibits pyruvate dehydrogenase-stops cells respiring) are examples
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Medicinal drugs that are enzyme inhibitors
Some antiviral drugs (inhibits enzyme which catalyses replication of viral DNA) & some antibiotics (penecillin inhibits an enzyme which catalyses formation of proteins in bacterial cell walls)
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Other cards in this set
It involves sharing electron pairs between atoms. e.g Carbon can form four covalent bonds with other carbon atoms or other atom types