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OCR Biology Revision Thread - 8th June Exam

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    (Original post by TX22)
    are these summaries helping?
    Yep thanks ! :yes:
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    carbon monoxide can lead to atherosclerosis and CHD. it really easy to learn.

    emphysema, lung cancer normally caused by tar.

    Tar relates to emphysema chronic bronchitis, and lung cancer

    carbon monoxide, nictotine related to CHD

    also diet like cholesterol, lipoproteins, high salt intake relates to CHD.




    (Original post by HumanNature1992)
    The more important stuff for smoking is in terms of diseases, like atherosclerosis, CHD, stroke, lung cancer, Chronic Bronchitits and Emphysema.:confused:
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    (Original post by TX22)
    carbon monoxide can lead to atherosclerosis and CHD. it really easy to learn.

    emphysema, lung cancer normally caused by tar.

    Tar relates to emphysema chronic bronchitis, and lung cancer

    carbon monoxide, nictotine related to CHD

    also diet like cholesterol, lipoproteins, high salt intake relates to CHD.
    Don't worry, I know this stuff, sitting this for a third time:p:

    Stroke, are also caused by nicotine, as nicotine create blood clots and a blood clot to the brain causes a stroke. And carbon momoxide irreversibly combines with haemoglobin making less o2 availabe for the brain.

    Also Lung cancer, caused by carciongens in the smoke --->uncontrolled cell growth ---> malignant tumour--->blocks air flow--->decreases gas exchange and leads to shortness of breath.
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    Hydrolysis

    H20 added
    Covalent bond broken
    Large molecule split into smaller molecules (seen in digestion)

    Condensation

    H20 released (H on one molecule, OH on other molecule)
    Covalent bond formed (-O-)
    Small molecules built into larger molecules (seen in muscle growth)


    Overview of the roles and functions of biological molecules

    Carbohydrates: Energy storage and supply, structure

    Proteins: Enzymes, antibodies, hormones, transport, structure

    Lipids: Membranes, energy supply, thermal insulation

    Vitamins & Minerals: Metabolic reactions, coenzymes

    Nucleic acids: Information molecules that carry the instructions for life

    Water: Support, transport, medium for metabolism



    Structural differences between a-glucose and b-glucose

    ABBA

    A-glucose = Below

    B-glucose = Above

    In a-glucose, the OH bond is below the the plane of the ring structure whereas in b-glucose, the OH bond is above the plane of the ring structure.



    CARBOHYDRATES

    Two monosaccharides of a-glucose form a disaccharide called maltose.

    Lots more a-glucose molecules forms a polysaccharide called amylose.


    Starch: energy storage in plants

    Amylose is present in starch.
    It's a long, unbranched chain.
    The angles of the glycosidic bonds cause amylose to coil.
    This makes it more compact, making it a good storage molecule, as more substance can be put into a small space.

    Starch is also made up of amylopectin.
    This is a long, branched chain.
    These branches allow enzymes to access the glycosidic bonds with ease so glucose can be released quickly.

    Starch is also insoluble in water which is vital as it means it does not affect the water potential of the plant cell and cause water to enter by osmosis (which would cause the plant cell to swell)


    Glycogen: energy-storage in animals

    Similar structure to amylopectin.
    Also made on a-glucose subunits.
    Differs to amylopectic as it has MORE side brances.
    This makes it even more compact than starch.

    Same properties as starch in that it's insoluble in water and it's branches allow glucose to be released quickly.


    Cellulose

    Made of b-glucose which forms long, straight chains.

    Hydrogen bonds form between the different cellulose chains to form macrofibrils.
    Macrofibrils can criss-cross and run in all directions to give the wall even more strength.

    Cellulose has great mechanical strength and structural support.
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    Proteins

    Monomers: amino acids

    Amino acids consist of an amino group, carboxyl group and an R group bonded to a carbon

    Condensation reaction takes place between the carboxyl group on one and the amino group on the other. The bond formed is a peptide bond


    Levels of protein structure

    Primary - sequence of amino acids. Involves peptide bonds

    Secondary - the coiling of polypeptide chains to form an alpha helix or the folding of polypeptide chains to form beta plated sheets. This involves hydrogen bonds (hold the coils/folds together)

    Tertiary - the coils and folds then coil and fold themselves.
    This is the final 3D structure for proteins made of one polypeptide chain
    This involves:

    Disulfide bonds (between sulfur on one cysteine molecule and sulfur on another) sulfur is a type of amino acid.

    Ionic bonds (between +ve R group and -ve R group)

    Hydrogen bonds between +ve molecule and -ve hydrogen

    Hyrophobic and hydrophillic interactions.


    Quaternary structure - How different polypeptide chains are assembled/held together.
    Involves all the bonds above.
    Final 3D structure for proteins made of more than one pp chain.


    Structure of collagen

    3 polypeptide chains wound in a triple helix held by hydrogen bonds

    35% of its primary structure is made of glycine.
    Glycine contains sulfur so it can form disulfide bridges = strong.

    Collagen + another collagen molecule -> fibril.
    Many fibrils make a fibre.
    Different collagen molecules are held together by covalent bonds
    (between amino acid group & carboxyl group)


    SHOT GUN POINTS

    Carbohydrate monosaccharides: glucose, fructose, galactose

    Carbohydrate disaccharides: sucrose (glucose+fructose), lactose(glucose+galactose), maltose (glucose+glucose)

    Carbohydrate polysaccharides: amylose, amylopectin

    Bond formed in condensation is glycosidic.

    Test for starch: iodine test, turns blue-black if present



    Protein monomer: amino acids

    Joining of amino acids forms a peptide bond.

    Test for protein: Biuret test, goes purple if protein present
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    these were posted on another thread by someone else. Thought i would just paste it here
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    About comparing the structure and functions of collagen and haemoglobin.. I can compare their structures but what would you say for their functions? Just one line about how collagen is strong and supportive, a fibrous protein but haemoglobin is a globular transport? Or would you have to relate the structure to the function?
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    I'm doing (and flopping ) this exam...

    haven't really started revision as I have psychology and chemistry which are loooong ass units...

    should be interesting to see though
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    Can someone please help me!!

    I'm stuck on:
    • Nucleaic Acids - DNA + RNA
    • Replication
    • Immune system
    • Smoking + disease
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    (Original post by ro.)
    Can someone please help me!!

    I'm stuck on:
    • Nucleaic Acids - DNA + RNA
    • Replication
    • Immune system
    • Smoking + disease
    What exact part in each of those topics?
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    serious question guys, i need 84% to get an A, do you think that is do-able?
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    (Original post by annieareyouokay)
    serious question guys, i need 84% to get an A, do you think that is do-able?
    With hard work and determination, yes. :yes:
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    Does anyone have the OCR Biology January Unit 2 2010 paper with mark scheme??
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    (Original post by Emy8643)
    Does anyone have the OCR Biology January Unit 2 2010 paper with mark scheme??
    Here:

    http://www.thestudentroom.co.uk/show...7#post25489187
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    (Original post by Marshmellow.)
    Here:

    http://www.thestudentroom.co.uk/show...7#post25489187
    Thank youu!
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    (Original post by Emy8643)
    Thank youu!
    Dont thank me, thank them
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    Wow these notes are really great!
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    (Original post by Marshmellow.)
    What exact part in each of those topics?
    I've got neculeaic acids and immune system down now, but i dont understand anything on protein synthesis, like i don't even understand what it says in my revision guide on it.

    And i understand smoking somewhat , but i just cant seem to remember it.
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    (Original post by ro.)
    I've got neculeaic acids and immune system down now, but i dont understand anything on protein synthesis, like i don't even understand what it says in my revision guide on it.

    And i understand smoking somewhat , but i just cant seem to remember it.
    I'll explain protein synthesis to you if you want. What revision guide do you have?

    Pretty much, think of protein synthesis in a step-by-step process like this: DNA --> RNA --> CYTOPLASM --> RIBOSOME --> PROTEIN.

    DNA is found in the nucleus. To make a protein, it must first leave the nucleus. But, DNA is too large to move out of the nucleus. So, DNA copies itself into RNA, which is a smaller molecule (it has a single polypeptide chain, DNA has a double). RNA leaves the nucleus and joins with a ribosome in the cytoplasm. Ribosomes are the organelles that look like jelly babies and are the site where proteins are made. A protein is synthesised here. There you go! Any questions?
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    Just to add to that.. the DNA gives the RNA a sequence to follow. It puts all the free floating RNA nucleotides in the same order (as is on the DNA) so it's effectively a replicate (just single stranded so it's able to leave the nucleus)
    After it's all in order, the RNA single strand will peel away from the DNA molecule and leave the nucleus via the nuclear pore as stated above. The ribosome's job is to translate the base sequences of RNA (which the DNA gave it) so the amino acids can be brought in the along in the correct order. Three bases code for an amino acid so a different order of bases will produce a different amino acid.
    The amino acids undergo condensation reactions to join up.. forming peptide bonds.. the chain of amino acids produces a protein.

    I suggest you watch a video of protein synthesis on youtube if you don't understand it. I find videos helpful for such subjects like DNA, RNA and immune response - just puts it all into context.

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Updated: June 7, 2010
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