OCR Biology Module 2

  • Created by: Jessinoch
  • Created on: 14-04-18 12:06
Describe the process of Protein Production
1. New proteins produced at RER and are folded & processed 2.They then are transported from ER to Golgi Apparatus in Vesicles 3. Proteins under further processing at Golgi Apparatus 4. Proteins enter more vesicles to go around cell
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What are the four main functions of the cytoskeleton?
1. Support the cell 2. Strengthen & maintain shape of cell 3. Aid movement of materials in cell 4. Causes the cell to also move
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Prokaryotic Cells
Extremely small cells (less than 2um), circular DNA, no nucleus (free DNA), polysaccharide cell wall, no membrane bound organelles, flagellin flagella, small ribosomes (e.g. e. coli bacterium)
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Eukaryotic Cells
Large cells (10-100um), linear DNA, present nucleus, no cell wall in animals/cellulose in plants/chitin in fungi, many membrane-bound organelles, microtubule flagella, large ribosomes (e.g. human liver cell)
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What is the difference between magnification and resolution?
Magnification is size (how much bigger the image is than the specimen) and resolution is the detail
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Light Microscopes
Uses light to look at a specimen, max magnification is x1500 and max resolution is 0.2um
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Scanning Electron Microscopes
Uses laser beams to scan a specimen (usually tagged with fluorescent dye), makes dye give off light & is focused through pinhole onto detector (clearer image). 3D image & used to look at thick specimens. Max mag is x500,000 and max res is 0.002um.
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Transmission Electron Microscopes
Beam of electrons transmitted through the specimen. Denser parts of the specimen absorb more electrons. Used on thin specimens. Max magnification is x1000000 (1 million) and max resolution is 0.0002um.
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7 Properties of Water
1. Liquid 2. Density 3. Solvent 4. Cohesion & Surface Tension 5. High Specific Heat Capacity 6. High Latent Heat of Vaporisation 7. Reactant
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Test for Sugars
Reducing Sugar - add benedict's reagent to sample & heat in water bath (blue -> brick red) / Non-reducing sugar - break sugars down using dilute hcl & heating in water bath, then neutralise with nahco3 and carry out normal benedict's test
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Test for Glucose
Test strips & reagent dipped into test solution (changes colour if present / colour change can be compared to a chart to give indication of conc)
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Test for Starch
Test sample & iodine dissolved in potassium iodide solution (browny-orange to blue-black colour)
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Test for Proteins
Biuret Test - add few drops of naoh solution to make alkaline and then add some copper (II) sulfate solution (solution will turn from blue to purple if positive)
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Test for Lipids
Emulsion test - shake the test substance with ethanol for about a minute and then pour solution into water (solution turns milky if positive)
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How can you determine the concentration of a solution?
1. Serial dilutions technique of solution to make different known concs 2. Use colorimeter with coloured filter to measure absorbance (+ control of water) 3. Use results to make a calibration curve showing absorbance/concentration 4. Compare unknown
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Energy store in plants made of 2 polysaccharides of a-glucose 1. amylose - long unbranched chain with coiled structure, compact (good storage) 2. Amylopectin - long branched chain with side branches - starch is insoluble in water (good for storage)
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Energy store in animals - a polysaccharide of a-glucose. A long branched chain with lots and lots of side branches (more than amylopectin) - good for storage.
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Major component of cell walls in plants - long unbranched chains of b-glucose, straight cellulose chains, cellulose chains linked together by hydrogen bonds to form microfibrils which provide structural support (criss-cross & high tensile strength)
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What are bacteria cell walls made from?
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What are exoskeletons made from?
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What do the structures of a-glucose & b-glucose look like?
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Name the 4 disaccharide formations
1. a-glucose + a-glucose -> maltose 2. a-glucose + fructose -> sucrose 3. b-galactose + a-glucose -> lactose 4. b-glucose + b-glucose -> cellobiose
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A group of substances that are soluble in alcohol rather than water
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What are triglycerides made up from?
Glycerol and 3 fatty acid chains
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What is the difference between saturated & unsaturated?
Saturated is no C=C bonds / un-saturated has C=C bonds (more unsaturated fatty acids means more kinks in the chain separating molecules leading to lower melting & boiling points)
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What bonds form when triglycerides form?
Ester bonds - the O-C=O bond
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What are the functions of a triglyceride?
1. Energy source & energy store 2. Insulation 3. Buoyancy 4. Protection
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What are phospholipids made up from?
Glycerol and 2 fatty acid chains and 1 phosphate group
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How do phospholipids behave in water?
1. The heads are hydrophilic and the tails are hydrophobic - they can form a layer on the surface with tails sticking out 2. Can also form micelles, which are balls with tails tucked away from water inside and heads on outside
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What are the adaptations of the phospholipid bilayer?
1. Membrane stability - inidividual phospholipids are free to move around 2. Selectively permeable - controls what goes in & out
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What is cholestrol?
Cholesterol has a small size and flattened shape allowing it to fit in between phospholipid molecules, they also bind to hydrophobic tails, allowing the tails to make more closely together to make membrane less fluid & more rigid
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What are proteins made up of?
Central carbon attached to an amino group, a carboxylic acid, hydrogen atom and a variable R group.
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What are amino acids joined together by?
Peptide bonds
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What are the four structural levels of a protein?
1. Primary Structure - sequence of amino acids 2. Secondary Structure - hydrogen bonds between amino acids (a-helix/bp-sheets) 3. Tertiary Structure - 3D structure 4. Quaternary Structure - 3D structure of several polypeptide chains
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What bonds hold the different structural levels together?
Primary Structure - peptide bonds between amino acids Secondary Structure - hydrogen bonds Tertiary Structure - Ionic bonds/disulfide bonds/hydrophobic(philic) interactions/hydrogen bonds Quaternary Structure - all the bonds above
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What are the strongest to weakest bonds?
(Strongest to weakest) Disulphide -> ionic -> hydrogen
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Conjugated globular protein with a prosthetic haem group. Made up of 2 a-chains and 2 b-chains, majority is wound into helix. Haemoglobin is soluble.
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Fibrous protein with no prosthetic group. Made up of left-handed helix structures. It is insoluble.
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1. DNA strands unzips by DNA Helicase 2. RNA Nucleotide bases pair up with exposed DNA bases 3. RNA Synthase forms covalent bonds between bases 4. mRNA strand formed breaks away from DNA 5. mRNA is free to migrate out of nucleus through nuclear pores
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1, mRNA attaches to ribosome on RER 2. Amino acid transported by tRNA attaches to ribosome 3. Adjacent amino acids join together by peptide bonds creating polypeptide chain 6. Process continues until 'stop' codon is reached on mRNA and chain is free
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Describe the structure of DNA
DNA (deoxyribonucleic acid) is a long chain polymer of nucleotide monomers. It is double stranded in a double helix arrangement. Bases pair according to complementary base pairing rule. Bases run anti-parallel to each other - hydrogen bonds between.
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DNA Replication
1. DNA unwinds due to gyrase enzyme 2. DNA unzips (hydrogen bonds break) due to DNA Helicase 3. Free phosphorylated nucleotides bond to exposed bases (CBPR) 4. DNA Polymerase catalyses addition of new bases in 5' to 3' direction (using template)
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DNA Replication continued...
5. Leading strand synthesised continuously, lagging strand is synthesised in fragments that are later joined by ligase enzymes 6. Phosphodiester bonds are made between each nucleotide to join them together 7. Product is 2 identical DNA molecules
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What molecules are in a DNA molecule?
The deoyxribose sugar is central - it is attached separately to a phosphate group and a base.
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How would you extract & purify DNA?
1. Macerate the tissue 2. Add a strong detergent 3. Add ethanol to allow DNA to precipitate out of the solution 4. DNA can then be further purified
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What are purines and pyrimidines?
Purines - double rings of carbon and nitrogen atoms (adenine and guanine) Pyrimidines - single rings of carbon and nitrogen atoms, smaller than purines (thymine, cytosine, uracil)
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The Lock & Key Model
Enzyme has an active site that is complementary to the substrate molecule, substrate fits into active site forming enzyme-substrate complex, then enzyme-product complex, products then are released and enzyme is unchanged.
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The Induced Fit Theory
As the substrate binds at the enzyme-substrate complex, the active site changes shape slightly to fit the substrate more closely.
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What factors affect enzyme activity?
1. Temperature (too high denatures/too low slows down) 2. pH (wrong amounts of H+/OH- messes up ionic bonds) 3. Enzyme Concentration 4. Substrate Concentration
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What is the difference between co-factors and co-enzymes?
Co-factors - help the substrate and enzyme bind together, not used or changed up Co-enzymes - they participate in reaction & are changed by it - act as carries etc and are continuously recycled
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Name two ways that enzyme activity can be inhibited
1. Competitive inhibition - competitive inhibitor has similar shape to substrate and competes for active site to block it Non-competitive inhibition - inhibitor binds to enzyme's allosteric site to change active site shape
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Draw the graph of the effect of substrate concentration as time goes on with a competitive inhibitor vs no inhibitor
No inhibitor starts at a faster rate and plateaus sooner than with inhibitor, but they both reach the same point at the end.
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Draw the graph of the effect of substrate concentration as time goes on with a non-competitive inhibitor vs no inhibitor
No inhibitor starts at a much faster rate and plateaus at the top of the graph, non-competitive inhibtor starts very slow and plateaus at the bottom of the graph, a little before no inhibitor does.
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What is the role of a membrane?
1. Separates the cell's components from it's external environment 2. Regulates transport of materials into & out of cell 3. Contains receptors for chemical signals / a site of cell communication
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What molecules are involved in the Fluid Mosaic Model of a membrane?
1. Glycocalyx (glycoproteins & glycolipids) 2. Peripheral/Extrinsic Proteins (support & signalling) 3. Integral/Intrinsic Proteins (channel & carrier) 4. Cholestrol (mechanical strength & flexibility) 5. Protein Receptor Sites
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Movement of molecules from an area of high concentration to an area of low concentration of that molecule
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Facilitated Diffusion
Movement of molecules from an area of high concentration to an area of low concentration of that molecule, across a partially permeable membrane via protein channels/carriers
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What are the factors that affect the rate of simple diffusion?
1. Temperature 2. Diffusion distance 3. Surface area 4. Size of diffusing molecule 5. Concentration gradient
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Passage of water molecules down their water potential gradient, across a partially permeable membrane
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Water Potential
The measure of the tendency of water molecules to diffuse from one region to another - measured in kPa
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What happens when water moves into & out of plant cells?
IN - The cell becomes turgid and does not break due to the cell wall OUT - The cell becomes plasmolysed and they become flaccid
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What happens when water moves into & out of animal cells?
IN - The cell will swell & burst (cytolysis) OUT - The cell shrivels and becomes crenated
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Active Transport
The movement of substances against their concentration gradient across a cell membrane, using ATP & protein carriers
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How does active transport work?
1. The molecule enters the carrier protein to move against concentration gradient 2. ATP splits into ADP and phosphate 3. The phosphate molecule binds to carrier protein, changing its shape and allowing molecule to pass through
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How large molecules may be brought into a cell - there are two types: Phagocytosis - intake of solid matter Pinocytosis - Intake of liquids
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How does endocytosis work?
1. Phagocytic cell approaches a bacterium 2. Cell extends to surround the bacterium 3. Bacterium is now enclosed within a phagocytic vesicle (phagosome)
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How large molecules may be exported out of cells
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How does exocytosis work?
1. Vesicle contains large molecule inside cell 2. Vesicle fuses with the plasma membrane 3. Large molecule exits the cell
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What is the purpose of checkpoints in cell division?
1. To prevent uncontrolled division leading to tumours like cancer 2. To detect & repair damage to DNA
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Significant for a-sexual reproduction, growth, repair & replacement, producing two identical cells
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Produces 4 non-identical daughter cells, significant for sexual reproduction, natural selection & genetic variation
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Name the steps of the cell cycle in order
Interphrase, Prophrase, Metaphase, Anaphase, Telephase, Cytokinesis (I PLAY MUSIC AT THE CLUB)
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MITOSIS: Interphrase
Consists of G1, S and G2. DNA replication, organelle doubling, proteins made, cell ‘double checks’ for mutations.
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MITOSIS: Prophase
Chromosomes super coil (shorten & thicken), nuclear envelope breaks down, centriole divides and 2 new centrioles move to opposite poles of cell, cytoskeleton threads form a spindle between centrioles.
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MITOSIS: Metaphase
Pairs of chromatids attach to spindle threads at the equator region by their centromeres.
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MITOSIS: Anaphase
The centromere of each pair of chromatids splits, motor proteins pull each sister chromatid pair in opposite directions to opposite poles.
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MITOSIS: Telophase
Separated chromosomes reach the poles, a new nuclear envelope is formed around each set of chromosomes.
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MITOSIS: Cytokinesis
Once mitosis is complete, the cell splits in two forming two genetically identical daughter cells.
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MEIOSIS: Phrophase I - Cytokinesis I
These stages are very similar as mitosis. The main difference is that recombination occurs during prophase I, which creates genetic diversity and involves chromatids swapping genes between themselves.
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MEIOSIS: Prophase II
Any reformed nuclear envelopes break down, chromatids coil & condense. spindles form.
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MEIOSIS: Metaphase II
The chromosomes attach, by their centromere, to the equator of the spindle, the chromatids of each chromosome are randomly arranged.
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MEIOSIS: Anaphase II
The centromeres divide, the chromatids are pulled apart by motor proteins to opposite poles.
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MEIOSIS: Telephase II
Nuclear envelopes form around each of the four haploid nuclei. In animals, the cells divide to give 4 haploid cells, in plants, the tetrad of four haploid cells is formed.
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MEIOSIS: Cytokinesis II
Cytoplasm and surface membrane divide, creating four independent haploid daughter cells.
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Advantages/disadvantages of light microscope
Wide range of specimens can be observed, they can be alive, they can be whole or embedded in wax, however non-coloured specimens must be stained & low res does not give detailed information
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Advantages/disadvantages of SEM
Produces detailed images of the structures inside cells, produces detailed 3D images showing contour of cells, however samples must be dead, a vacuum is used as electron beams deflected in air, it is expensive, needs skill & training to use
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Advantages/disadvantages of TEM
Produces detailed images of the structures inside cells, however samples must be dead, a vacuum is used as electron beams deflected in air, it is expensive, needs skill & training to use
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Card 2


What are the four main functions of the cytoskeleton?


1. Support the cell 2. Strengthen & maintain shape of cell 3. Aid movement of materials in cell 4. Causes the cell to also move

Card 3


Prokaryotic Cells


Preview of the front of card 3

Card 4


Eukaryotic Cells


Preview of the front of card 4

Card 5


What is the difference between magnification and resolution?


Preview of the front of card 5
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