Biology - 2.2

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  • Created by: TobyHill5
  • Created on: 05-04-18 13:29
Define a hydrogen bond
a weak interaction that occurs wherever molecules contain a slightly -vely charged atom bonded to a slightly +vely charged Hydrogen atom
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Define a covalent bond
when electrons are shared between atoms
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Define a condensation reaction
when 2 molecules are bonded together with the removal of water as a waste product
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Define a hydrolysis reaction
when a molecule is split into 2 smaller molecules with the addition of water
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Define monomer
a small molecule which binds to many other identical molecules to form a polymer
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Define polymer
a large molecule made from many smaller molecules called monomers
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The 7 properties of water
(1) liquid (2) density (3) a solvent (4) cohesion+surface tension (5) high specific heat capacity (6) high latent heat of vapourisation (7) good reactant
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How is water liquid and what is the benefits
As the molecules move they make+break hydrogen bonds, which make it harder for water to become a gas. Water can therefore provide habitats, it is a major component of tissue, and provides a reaction and transport medium.
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Benefits of water's density
The density provides an ideal habitat, as animals are able to float. As water freezes, the water molecules align in a structure that is less dense than water (ice). The layer of ice on top of the water is able to insulate the water below.
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Why is water a good solvent
The +ve and -ve parts of molecules are attracted to -ve and +ve parts of solute. The molecules cluster around the solute, helping to separate them. This helps molecules and ions to be transported when dissolved, and react together.
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Water's cohesion + surface tension
Hydrogen bonds hold water together, demonstrating cohesion. The molecules at the surface bond to each other and to the molecules beneath as they are more attracted to each other. the surface can contract and resist force - this is surface tension
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Water's high specific heat capacity
Molecules are held tightly together by hydrogen bonds, therefore, lots of heat energy is needed to increase KE+temperature (4.2kJ to raise 1kg by 1 degree). This means it provides a stable environment
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Carbohydrates (what they contain and what they act as)
Contain carbon, hydrogen and oxygen. Acts as source of energy, store of energy and structural units.
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Define monosaccharide
The simplest carbohydrates, a source of energy due to the amount of C-H bonds
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2 isotopes of glucose are...
alpha + beta
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Define polysaccharide
polymers of monosaccharides, made up of monosaccharide monomers bonded together
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Why are polysaccharides good energy stores
COMPACT: don't occupy large space but still store large amounts of energy MADE OF GLUCOSE: glucose easily snipped off from the end by hydrolysis UNBRANCHED: chains can coil into compact shape BRANCHED: lots of glucose snipped off
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Why is it good that polysaccharides are less soluble.
If glucose molecules dissolved in water, the water potential would reduce and excess water would diffuse in. Regions that can hydrogen bond with water are hidden inside the coil
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Enzymes used in forming 1-4 and 1-6 glycosidic bonds
1-4: amylase 1-6: glucosidase
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A long chain of a glucose with glycosidic bonds between carbon 1-4. Coils into a spiral shape as hydrogen bonds hold it together. Hydroxyl groups on carbon2 are on inside, making it less soluble and allows H bonds to form to maintain shifts.
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Like amylose, but also has branches between carbon 1-6. It coils into spiral with hydrogen bonds holding it together. branches emerge
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Like amylopectin, but has more branches. 1-4 bonded chains are smaller so it has less tendency to coil. It has more braches, so is more compact. It is easier to remove monomer units from all the branches.
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CELLULOSE (details)
A structural polysaccharide. Forms cell wall in plants. Insoluble and fibrous. A homopolysaccharide.
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CELLULOSE (structure)
Ordinary b glucose can't bond together in a chain, so every other molecule is rotated 180 degrees. H bonding between monomers in same chain gives additional strength. H bonds between different chains give whole structure strength.
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Structure of plant cell walls
Macro+microfibrils have high tensile strength due to glycosidic+hydrogen bonds. They criss-cross the wall for strength. It is difficult to digest as glycosidic are hard to break.
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Function of plant cell walls
As plants have no skeleton, each cell needs a strong wall to support the plant. There is space between macrofibrils for water+mineral ions to pass (permeable). The wall has high tensile strength, stopping cells from bursting, supporting plant
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Define Disaccharide
2 monosaccharides joined by a glycosidic bond in a condensation reaction.
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Structure of Glycerol
3 carbon atoms. 3 free OH groups C3H5(OH)3
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Structure of Fatty Acids
Have a carboxyl (-COOH) attached to a hydrocarbon. Can be 2-20 carbons long. Saturated or unsaturated
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Ester bonds
Formed when forming triglycerides in a condensation reaction between acid and glycerol. 3 condensation reactions producing 3 water molecules. Between -COOH and -OH
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5 Functions of Triglycerides
(1) energy source - breaks down to CO2+H20 (2) energy store - insoluble and release more energy due to more H atoms. (3) insulation (4) buoyancy (5) protection
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Define Lipid
a group of substances that are soluble in alcohol rather than water.
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Properties of lipids
Lots of carbon + hydrogen. Little oxygen. insoluble in water (non-polar). Not polymers, but macromolecule.
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Define phospholipid
Molecule consisting of glycerol, 2 fatty acids and 1 phosphate group.
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Cholesterol - structure and function
a steroid alcohol. has 4 carbon based rings. small. hydrophobic. regulates fluidity.
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Polymers made from amino acids. structural components. proteins for active transport. e.g. enzymes, antibodies, hormones
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Amino Acids - structure
Contain carbon, hydrogen, oxygen + nitrogen. There are 20 in proteins. Has an amino (-NH2) group and carboxyl (-COOH) group either end of a C-H bond. Also has an R group, different for all amino acids.
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Peptide Bonds
Joins 2 amino acids and requires condensation.
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Define Primary Structure
the sequence of Amino acids
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Define secondary structure
the coiling or folding of an amino acid chain, which arises often as a result of hydrogen bond formation between different parts of the chain. a helix and b sheet
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Define Tertiary Structure
the overall 3D shape of a protein molecule. shape arises due to interactions - H bonding, disulfide bridges, ionic bonds + hydrophobic interactions
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Define Quaternary Structure
protein structure where a protein consists of more than one polypeptide chain
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FIBROUS proteins
regular repetitive sequence of amino acids(insoluble). form fibres with structural function. e.g. collagen, elastin, keratin
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GLOBULAR proteins
roll up into a sphere. hydrophilic R groups on inside so it is soluble. they have specific shapes so are enzymes+hormones
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FIBROUS. mechanical strength. in artery walls, tendons, cartilage+bones.
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FIBROUS. lots of cysteine (+disulfide bridges) mechanical barrier and protection. finger nails, hair
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FIBROUS. cross linking + coiling so strong + extensible. skin+lungs.
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GLOBULAR. 4 polypeptide chains (2 alpha, 2 betaglobin). Haem group in each chain containing an iron ion that carries oxygen.
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GLOBULAR. 2 polypeptide chains. A chain begins with a helix, B chain ends with b sheet. both chains joined by disulfide links. soluble
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GLOBULAR. digests proteins in stomach. 1 chain of 327 amino acids. 43 with acidic R group. 4 amino acids with basic R groups. hydrogen bonds and 2 disulfide bridges.
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Define stationary phase
either chromatography paper or a TLC plate. the paper is made from cellulose and the TLC plate is a thin sheet of plastic coated in a layer of silica gel. always free -OH groups pointing outwards, in contact with mobile phase
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Define mobile phase
the solvent for the biological molecules. we use water or ethanol. it flows through and across the stationary phase, carrying the biological molecules with it
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as the solvent travels up, the components of the solution travel with it. different components travel at different speeds. by the time solvent reaches top of stationary phase, components separated.
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How do you calculate Retardation Factor
(distance from baseline to dye) / (distance from baseline to solvent front)
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3 methods of identifying colourless molecules
(1) UV light - TLC plates fluoresce (2) Ninhydrin - amino acids appear brown/purple (3) Iodine - binds to molecules
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How do the molecules move upwards in chromatography?
The speed depends on their solubility and polarity. Exposed -OH groups make stationary phase polar, and can form H bonds with molecules
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Other cards in this set

Card 2


Define a covalent bond


when electrons are shared between atoms

Card 3


Define a condensation reaction


Preview of the front of card 3

Card 4


Define a hydrolysis reaction


Preview of the front of card 4

Card 5


Define monomer


Preview of the front of card 5
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