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

    0
    ReputationRep:
    (Original post by steph_v)
    If possible could someone explain muscle contraction to me? I sort of understand it, but now I've confused myself. Especially about calcium ions and the neuromuscular junction or whatever it's called.
    action potential reaches motor end plate
    influx of calcium ions causing Ach to be released by exocytosis.
    Ach diffuses across synaptic clef and binds to receptors in post synaptic membrane.
    release of Na ions causing depolarisation down T-tubules.
    Ca ions released in sarcoplasm, binds to troponin and moves trypomyosin revealing actin binding site.
    Ca ions also cause ATP to be broken down to ADP and Pi. Using energy from ATP, myosin binds to actin binding site creating actin-myosin cross bridge.The muscle contracts in a rachet mechanism and ATP is used to break the cross bridge.
    Offline

    1
    ReputationRep:
    (Original post by noodlecookie)
    I hope everyone hasn't turned against you for stretching the page lol!!

    I don't know what exactly you want me to explain about wheat bread... do you mean plant cloning in agriculture or artificial selection?
    Everyone is ignoring me though lol. I think they all hate me already. Artificial selection please!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!
    Offline

    0
    ReputationRep:
    (Original post by student92)
    so it can be A... mark scheme says B
    are you looking at the question with the table?

    if so it is because the other baby HAS to be A
    so that only leaves phenotype B for this baby
    out of AB A B and O

    Offline

    0
    ReputationRep:
    (Original post by steph_v)
    If possible could someone explain muscle contraction to me? I sort of understand it, but now I've confused myself. Especially about calcium ions and the neuromuscular junction or whatever it's called.

    right, so action potential reaches motor end plate (presynaptic knob). this depolarises it, calcium ions move into presynaptic knob. vesicles containing ACh move and fuse with presynaptic membrane, they release Ach via exocytosis. Ach diffuses across cleft. Binds to sarcolemma (muscle fibre / cell membrane). sarcolemma is the equivalent of last unit's postsynaptic membrance. this causes sodium ion channels on it to open, sodium diffuses in, depolarises it. this wave of depolarisation spreads down the sarcolemma and through a system of Transverse (T) tubules. this causes sarcoplasmic recticulum (specialised ER) to release calcium ions, which diffuse through sarcoplasm (muscle cell cytoplasm). this calcium ions bind to troponin on the sarcomere's thin actin filament. troponin shape is changed due to binding of calcium; it moves tropomyosin. tropomyosin beforehand was blocking a myosin-head binding site (on the actin filament), preventing crossbridges from forming. howeer, because the calcium binds to the troponin whichh moves the tropomyosin the binding sites are now exposed
    Offline

    0
    ReputationRep:
    do we have to be able to label the cerebral cortex with all the different areas such as motor area and visual association area?
    Offline

    0
    ReputationRep:
    (Original post by noodlecookie)
    I isn't a blood group, I is the thing (gene) that carries the blood group O, A, B or AB (allele).

    Haha, that sounds funny out of context :p: I isn't a blood group
    woops sorry dat woz my mistake
    Offline

    0
    ReputationRep:
    Can someone please go over how a polypeptide is assembled, i think i will understand it easier if it's in someone elses words than the book
    Offline

    1
    ReputationRep:
    (Original post by Archen)
    are you looking at the question with the table?

    if so it is because the other baby HAS to be A
    so that only leaves phenotype B for this baby
    out of AB A B and O

    Oh yeaaaah! damn, lol thanks
    Offline

    1
    ReputationRep:
    Whoever negged me, why? What did I do wrong? Are you negging me purely because I already have neg rep? I haven't been rude to anyone in this thread. Why don't you man up and explain why you negged me?

    Anyway, good luck for biology tomorrow.


    NOT. fool.
    Offline

    0
    ReputationRep:
    do we have to know bout downstreaming process???

    Penicillin is removed from the fermenter for downstream processing.
    Describe what happens during downstream processing.(5m)
    Offline

    0
    ReputationRep:
    (Original post by Sakujo)
    Do you have the purple OCR book?
    yup..
    Offline

    0
    ReputationRep:
    (Original post by blundell91)
    do we have to be able to label the cerebral cortex with all the different areas such as motor area and visual association area?
    In the specification it says you only need to know where the cerebrum, cerebellum, hypothalamas and medulla oblongata are..
    Offline

    11
    ReputationRep:
    (Original post by Ohhai)
    yup..
    Okay flick to the back where the spread answers are and there should be a table showing the differences and similarities of natural and artificial selection, read, memorise, reproduce in exam, full marks.
    Offline

    0
    ReputationRep:
    what is the function of vitamin A. This linked to golden rice
    Offline

    0
    ReputationRep:
    (Original post by Reflex)
    Can someone please go over how a polypeptide is assembled, i think i will understand it easier if it's in someone elses words than the book

    2 Processes are involved Transcription and Translation.

    Transcription: DNA Unravles (by dipping into Nucleolus) and breaks apart. mRNA made by complimentary base pairing with the template strand of the DNA, e.g. T on Template strand A on mRNA strand, only difference is that instead of T on mRNA its U (Uracil- I think thats how its spelt, doesn't matter as I don't think you need this) So when the mRNA has been transcribed it is a copy of the coding strand of the DNA (apart from T's replaced with U's) This now leaves the Nucleus to begin translation.

    Translation: mRNA binds to Ribosome in cytoplasm. tRNA which contains anti-codons, complimentary base pairings to the codons on the mRNA (codons are just 3 bases- each codon codes for an amino acid). A tRNA binds to the mRNA via Hydrogen bonding, on the opposite end of the tRNA it has exposed bases where an amino acid is joined to it. A second tRNA binds to the next codon next to it, this means the 2 amino acids at the other end are next to each other and form a peptide bond. The first tRNA unbinds. The whole process is continued untill the end of the mRNA (stop codon) You now have an amino acid chain which is a polypeptide/protein.
    • Community Assistant
    • PS Helper
    • PS Reviewer
    Offline

    3
    ReputationRep:
    Community Assistant
    PS Helper
    PS Reviewer
    Vitamin A creates rhodopsin that is used in sight, and bone growth.
    Offline

    0
    ReputationRep:
    (Original post by Ohhai)
    In the specification it says you only need to know where the cerebrum, cerebellum, hypothalamas and medulla oblongata are..
    In the spec. it says:

    Describe, with the aid of diagrams, the gross structure of the human brain and outline the functions of the cerebrum, cerebellum, hypothalamas and medulla oblongata.

    The fact that there are two clauses with two different command words, (describe and outline) leaves it open...
    Offline

    0
    ReputationRep:
    Hey everyone! Ok i made a revision guide covering some of the more complicated process using some of the stuff that you guys have made (which i am eternally grateful for:yep: ), notes from class and the book.
    It doesnt cover every topic, and if there are any mistakes i apologise now:woo:

    Good luck everyonefor tomorrow!
    Attached Files
  1. File Type: doc Biology Revision.doc (112.0 KB, 247 views)
    Offline

    0
    ReputationRep:
    (Original post by amitpatel44)
    what is the function of vitamin A. This linked to golden rice
    It's got quite a few functions:

    - essential for bone growth
    - forms part of the visual pigment rhodopsin
    - involved in the synthesis of many glycoproteins (cell growth and development)
    - needed for differentiation of epithelial cells

    It makes a lot of people in developing countries blind, because it is only found it animal sources and they don't eat a lot of meat.
    Offline

    0
    ReputationRep:
    (Original post by Just-Some-Guy)
    Hey everyone! Ok i made a revision guide covering some of the more complicated process using some of the stuff that you guys have made (which i am eternally grateful for:yep: ), notes from class and the book.
    It doesnt cover every topic, and if there are any mistakes i apologise now:woo:

    Good luck everyonefor tomorrow!
    Thank you

    +rep
 
 
 
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.