Hey there! Sign in to join this conversationNew here? Join for free

OCR Biology F212 Revision [3rd June 2013] (Now Closed) watch

  • View Poll Results: How did you feel the F212 exam went?
    Awesome
    14
    9.46%
    Good
    50
    33.78%
    Okay
    53
    35.81%
    Bad
    16
    10.81%
    Rubbish
    8
    5.41%
    Not Sure
    7
    4.73%

    Offline

    2
    ReputationRep:
    During Semi-conservative replication does the DNA polymerase help break the hydrogen bonds between the bases apart? Or does it help during Proteinsynthesis? Or is it used for both?
    Offline

    2
    ReputationRep:
    (Original post by HelenPaddock)
    The following tests are part of the specification for biological molecules, could someone please bullet point how to do each one as you would get marks for on the mark scheme. Thank you!
    (r) describe how to carry out chemical tests to identify the presence of the following molecules: protein (biuret test), reducing and non-reducing sugars (Benedict’s test), starch (iodine solution) and lipids (emulsion test);
    (s) describe how the concentration of glucose in a solution may be determined using colorimetry (HSW3).

    1) PROTEIN- add a fews drops of Biuret solution (which contains NaOH and CuSO4) in cool sample.
    Chemicals react with the peptide bonds, and if protein is present, colour changes from pale blue to lilac.

    2) REDUCING SUGAR- All monosacchrides and some disaccharides (e.g. maltose) are reducing sugar.
    You place a few drops of Benedicts Solution to the sample and you heat it in a water bath to 80 degrees.
    If reducing sugar is present, colour changes from blue to a brick red precipitate (of CU2+)

    3) NON- REDUCING SUGAR- Most disaccharides are reducing sugars (e.g. sucrose and lactose)
    First of all, you ensure that no-reducing sugar is present in the sample (carry out a negative benedicts test).
    Then you boil the sample with HCL (this hydrolyses the non-reducing sugar, so that the glycosidic bond between the disaccharide molecule breaks apart, to form reducing sugars)
    Then you cool the solution and neutralise with Na2CO3 (as Benedicts test doesn't work in an acidic environment)
    Then you add Benedicts solution the second time round, and if the non-reducing sugar was present in the original sample, colour changes from blue to an orange/red precipitate.

    4) LIPID
    Mix sample with ethanol (this dissolves any lipid present)
    Pour the resulting solution into another clean test tube containing water
    If lipid is present, a cloudy white emulsion will form.

    5) STARCH
    Add a solution of iodine ( in potassium iodide) to sample.
    If starch is present, colour changes from yellow/brown- blue/black
    Offline

    0
    ReputationRep:
    (Original post by Hellomrnut)
    Explain an experiment using the water displacement method (Water bath, delivery tube, test tube filled with water upside down in the water bath and a conical flask where the experiment is taking place with the cork and delivery tube attached at the top)
    An example is the breakdown of H2O2 using the enzyme catalase to form H2O and O2
    The release of O2 can be recorded in the volume of gas collected from the delivery tube into the water bath and the rate of O2 collection is effectively the volume of Oxygen collected divided by the time taken
    Record these results, make a graph etc
    Change each variable (pH etc) keeping other variables constant
    Record the effect of these variables on rate of reaction (enzyme activity)

    Hope that helped

    Thanks!
    Offline

    2
    ReputationRep:
    (Original post by Beni24)
    During Semi-conservative replication does the DNA polymerase help break the hydrogen bonds between the bases apart? Or does it help during Proteinsynthesis? Or is it used for both?
    The DNA polymerase does two things

    1) It catalyses the formation of covalent bonds between the phosphate groups
    2) Proof reads the DNA

    Offline

    2
    ReputationRep:
    (Original post by HeyMickey6)
    Isn't Fe2+ in-organic tho ?
    good point.... guess it could be both organic and inorganic substances then..
    my notes are deceiving me
    Offline

    2
    ReputationRep:
    Did the january 2013 paper..just got a D..feeling very confident for the exam..not
    similarities and difference between Starch and cellulose?
    Offline

    0
    ReputationRep:
    (Original post by Beni24)
    During Semi-conservative replication, is 'DNA unzips' the same as saying The hydrogen bonds between the bases are broken apart?
    Say both, that'd usually give you 2 marks. So first you'd say the molecule untwists, then unzips, and then explain this by saying the hydrogen bonds break.
    Offline

    0
    ReputationRep:
    (Original post by Ambitions)
    1) PROTEIN- add a fews drops of Biuret solution (which contains NaOH and CuSO4) in cool sample.
    Chemicals react with the peptide bonds, and if protein is present, colour changes from pale blue to lilac.

    2) REDUCING SUGAR- All monosacchrides and some disaccharides (e.g. maltose) are reducing sugar.
    You place a few drops of Benedicts Solution to the sample and you heat it in a water bath to 80 degrees.
    If reducing sugar is present, colour changes from blue to a brick red precipitate (of CU2+)

    3) NON- REDUCING SUGAR- Most disaccharides are reducing sugars (e.g. sucrose and lactose)
    First of all, you ensure that no-reducing sugar is present in the sample (carry out a negative benedicts test).
    Then you boil the sample with HCL (this hydrolyses the non-reducing sugar, so that the glycosidic bond between the disaccharide molecule breaks apart, to form reducing sugars)
    Then you cool the solution and neutralise with Na2CO3 (as Benedicts test doesn't work in an acidic environment)
    Then you add Benedicts solution the second time round, and if the non-reducing sugar was present in the original sample, colour changes from blue to an orange/red precipitate.

    4) LIPID
    Mix sample with ethanol (this dissolves any lipid present)
    Pour the resulting solution into another clean test tube containing water
    If lipid is present, a cloudy white emulsion will form.

    5) STARCH
    Add a solution of iodine ( in potassium iodide) to sample.
    If starch is present, colour changes from yellow/brown- blue/black
    Really helpful, thank you!
    Offline

    2
    ReputationRep:
    Why do vaccines need to be continually updated? Apart from mutations... (for a 3 mark question say? )
    Offline

    0
    ReputationRep:
    (Original post by SheriB)
    Did the january 2013 paper..just got a D..feeling very confident for the exam..not
    similarities and difference between Starch and cellulose?
    Starch is energy storage. Cellulose is structural.
    Starch contains alpha glucose. Cellulose contains beta glucose.
    Starch is branched. Cellulose is not branched.
    Starch has no fibrils. Cellulose is comprised of fibrils
    Starch has no hydrogen bonding. Cellulose has hydrogen bonding

    Both contain Glycocidic bonds. Both are insoluble.
    Offline

    2
    ReputationRep:
    Guys whats a vector?
    Offline

    0
    ReputationRep:
    Describe the actions of t lymphocytes in the immune response (8)
    Offline

    0
    ReputationRep:
    (Original post by rival_)
    Guys whats a vector?
    Something that transports a disease/pathogen (eg the mosquito is the vector for the plasmodium pathogen)
    Offline

    0
    ReputationRep:
    (Original post by rival_)
    Guys whats a vector?
    An organism that carries a disease from one host to another.
    Offline

    0
    ReputationRep:
    (Original post by senS)
    Describe the actions of t lymphocytes in the immune response (8)
    Pathogen is recognised as foreign by antigens. (humoral response)
    Specific t lymphocyte must be found that is complimentary to the antigen. (clonal selection)
    Once this occurs clonal expansion occurs in which mitosis occurs rapidly.
    Then the T lymphocytes differentiate into 3 types of T lymphocytes:

    T killer :
    Engulfs and destroys infected cells

    T memory:
    Provides immune memory for a later infection. so antibodies can be produced faster

    T helper:
    Produces cytokines which stimulate B lymphocytes.
    Offline

    0
    ReputationRep:
    can someone outline the lock and key theory for me in specific marks?
    Offline

    2
    ReputationRep:
    I am going to fail this exam so hard ahah
    Offline

    0
    ReputationRep:
    (Original post by MrMeep2580)
    T killer : Engulfs and destroys infected cells
    Huh? In my book, it says that only phagocytes (Macrophages and Neutrophils) engulf cells. It says that T-killer cells secrete toxic substances such as hydrogen peroxide to kill the cell. Is this wrong?
    Offline

    2
    ReputationRep:
    (Original post by MrMeep2580)
    can someone outline the lock and key theory for me in specific marks?
    Hello

    Well lock and key is simply the substrate is exactly complementary to the active site

    But in AS we need to know about the Induced Fit hypothesis...which states that the active site is able to alter its shape to allow the complementary substrate to fit to into it.

    Also, the active site has charged amino acids which hold the substrate in
    Offline

    1
    ReputationRep:
    Question:

    Explain the link between classification and phylogeny
 
 
 
Poll
Do you agree with the PM's proposal to cut tuition fees for some courses?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.