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

AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011 Watch

  • View Poll Results: Are you resitting this unit?
    YES!
    12.91%
    NO!
    87.09%

    Offline

    0
    ReputationRep:
    would someone please be able to look over this synoptic essay i did and maybe give me a rough mark out of 25? i dont have anyone to mark them as im on study leave and cant get into school to hand them into teachers so i would really appreciate anyones help
    its a really rubbish one thats barely synoptic and took about 45mins including the plan

    Receptors and their role in coordination

    Spoiler:
    Show

    Receptors allow an organism to respond to a stimulus, which could potentially be harmful, therefore increasing the chances of survival. Organisms with better adapted responses will have a selection pressure favouring them and will therefore be more likely to survive. There are many different types of receptors in organisms, controlling both the nervous system and the hormonal system. Receptors involved in the nervous system can either be linked to the autonomic or the voluntary system. This essay will discuss the many uses of receptors and how they are important to living organisms.

    Receptors respond to stimuli. Specific receptors will only respond to certain stimuli. In the nervous system receptors respond by sending nerve impulses down sensory neurones until they reach the CNS. One example of a receptor that does this is the Pacinian corpuscle, which only responds to mechanical pressure. The receptor consists of the ending of a sensory neurone, surrounded by layers of connective tissue. When a stimulus-mechanical pressure – is applied, it changes the shape of the axon membrane. This pressure also changes the shape of the stretch mediated sodium ion channels, causing the membrane to be more permeable to sodium ions. This causes an influx of sodium ions which reverses the potential difference across the membrane, depolarising it. If the stimulus exceeds the threshold value, a generator potential will be created that is large enough to initiate an action potential which then travels down the neurone as a nerve impulse. In this way receptors act as transducers, converting the energy of a stimulus into a message that the CNS can understand.
    Receptors are involved in reflex arcs which are rapid responses to harmful stimuli. A reflex arc is involuntary and involves a coordinator such as the spinal cord, ensuring rapid impulses, as the information does not have to be coordinated by the brain which would otherwise be overloaded with unnecessary information. This prevents harm to an organism therefore increases chances of survival.

    Simple responses to stimuli that involve receptors are Taxes, Kineses and tropisms. A taxis for example is a simple response that occurs due to a directional stimulus. Woodlice for example will respond to the directional stimulus of light by moving into darkness. Photoreceptors allow the woodlice to do this, preventing the woodlice from drying out and therefore increasing chances of survival. Tropisms affect plants and involve responses to directional stimuli such as light or gravity. Plants however cannot control responses by the nervous system therefore respond to stimuli via the hormonal system using chemicals called growth factors e.g. IAA. When a positive phototropism occurs the plant will grow towards light, as the growth factor IAA will travel down the shaded side of the shoot, causing that side to elongate and bend towards the light. This maximises photosynthesis and therefore increases chances of survival.

    Receptors in larger organisms are involved in controlling the functions of organs and certain processes. Chemoreceptors and baroreceptors in the carotid arteries/aorta respond to changes in the blood. Chemoreceptors for example respond to changes in pH (due to levels of carbon dioxide) if the pH is lower than the set point (due to high conc. of CO2) chemoreceptors will respond by sending impulses to the centre in the medulla oblongata that increases heart rate. The medulla will then send impulses down the sympathetic pathway connecting to the SAN, causing more electrical activity to be stimulated, therefore increasing heart rate (which removes excess CO2 as blood will circulate more rapidly) and returning the blood pH back to normal. This ensures that the CO2 level in the blood remains constant and at a safe level.

    Photoreceptors in the retina respond to stimuli in the form of light. There are two different types of photoreceptor; rod cells and cone cells. Many rod cells are connected to one bipolar cell (retinal convergence), therefore the threshold value needed to create an action potential is exceeded at lower light intensity. This means that rod cells only produce images on black and white and have low visual acuity. Cone cells however are each attached to an individual bipolar cell, therefore light of higher intensity is needed to overcome the threshold value. This means that cone cells respond only to high intensity light therefore can produce coloured images. As they are attached to individual bipolar cells, cone cells have high visual acuity. The type and number of photoreceptors in the retina is different for different organisms, adapting them to their environment for better survival.

    As well as nervous control, receptors are also involves in hormonal control. Glycoprotein receptors for example are situated on target cells and have a structure that is specific and complementary to a particular hormone. Glucagon is released from the a-cells of the islets of Langerhans in the pancreas and binds to receptors on liver cells (target cells). This hormone receptor complex formed activated an enzyme inside the cell that stimulates the conversion of ATP into cyclic AMP. The hormone glucagon therefore acts as a first messenger whilst the cyclic AMP acts as a second messenger. Cyclic AMP stimulates a number of chemical reactions that results in the desired response (Glycogenolysis and Gluconeogenesis) which in this case is to increase the blood glucose level. this is an example of negative feedback as the blood glucose level is returned to normal, therefore illustrating how receptors play a key role in homeostasis.

    Receptors are also involved in the immune system of an organism. In cell mediated immunity T-cells have receptors on their cell surface membrane that are specific and enable detection of any foreign material. These receptors therefore allow the body to respond to any harmful material such as bacteria or viruses. On binding to the foreign material the T-cells initiate an immune response involving B-cells and antibodies in order to destroy the pathogen and hence increase the chances of survival of the organism.

    Receptors play important roles in homeostasis and response to harmful stimuli. They can be involved in either voluntary or involuntary nervous systems or even in hormonal systems and therefore increase the chances of survival.


    i had alot more stuff in my plan such as control of body temperature etc but i ran out of time lol
    Offline

    2
    ReputationRep:
    (Original post by Ramin Gorji)
    Just did the specimen paper,some of the questions are so badly worded. I hope that is because its a specimen and not a real paper.
    Yeah that paper is terrible. I mean the other papers are terrible too but the sample one is especially terrible.
    Offline

    2
    ReputationRep:
    (Original post by Ramin Gorji)
    can someone help me out on question 10b specimen paper part b (iii) it says describe the effect of blue light on the growth of seedlings p and q is it something to do with IAA only responding to normal light??? I don't undestand the Mark scheme :/
    What does the mark scheme say?
    Offline

    0
    ReputationRep:
    (Original post by Destroyviruses)
    unit 1= 100
    unit 2= 140
    unit4=100
    unit 5=140

    the isas are 60 each methinks!
    aww genius stuff!! Thank you! x
    Offline

    0
    ReputationRep:
    (Original post by tehsponge)
    What does the mark scheme say?
    the Mark scheme says for 3 marks you must mention inhibits growth of both in sucrose solution, stimulates growth of both in sucrose and IAA solution. greater effect in P. seedling p is with both root and shoot tipscut off, seedling q is just with roots cut.
    Offline

    0
    ReputationRep:
    Can someone explain the translation stuff in polypeptide synthesis... im really confused :/

    Thanks xx
    Offline

    2
    ReputationRep:
    (Original post by Ramin Gorji)
    the Mark scheme says for 3 marks you must mention inhibits growth of both in sucrose solution, stimulates growth of both in sucrose and IAA solution. greater effect in P. seedling p is with both root and shoot tipscut off, seedling q is just with roots cut.
    Hmm I need to see the whole question. I'll have a look at the sample paper and get back to you.
    Offline

    2
    ReputationRep:
    (Original post by .Hayley.)
    Can someone explain the translation stuff in polypeptide synthesis... im really confused :/

    Thanks xx
    Any specific parts, or just the whole thing?
    Offline

    0
    ReputationRep:
    (Original post by .Hayley.)
    Can someone explain the translation stuff in polypeptide synthesis... im really confused :/

    Thanks xx
    okie dokie, translation occurs in tge cytoplasm of the cell. it requires ribosomes and the mRNA created in transcription from the nucleus. 1) ribosomes attach to the first set of codons on the mRNA ( codons are the bases of the mRNA). 2) this provides the template for anticodons ( bases on tRNA) to attach to the codons of the mRNA on the ribosomes. 3) ribosomes move up the mRNA strand and attach tRNA as explained before. 4) tRNA has an amino acid molecule at the end of it clover shaped body. 5) when two or more tRNA molecules are next to each other a peptide bond can be formed by condensation reaction using ATP. 4) this continues until it reaches a group of 3 bases on the codon that are called a stop codon this stops the process of translation and polypeptide is finished. hope I've said most of the important points but youshould have a look attempt power point presentation uploaded either on this page or 1/2 back it has some descent points on it
    Offline

    0
    ReputationRep:
    (Original post by tehsponge)
    Hmm I need to see the whole question. I'll have a look at the sample paper and get back to you.
    thanks
    Offline

    2
    ReputationRep:
    (Original post by Ramin Gorji)
    the Mark scheme says for 3 marks you must mention inhibits growth of both in sucrose solution, stimulates growth of both in sucrose and IAA solution. greater effect in P. seedling p is with both root and shoot tipscut off, seedling q is just with roots cut.
    Okay, its a describe question, so all you have to do is describe what the table shows you. The table shows that for the ones grown in just 1% sucrose solution there is a decrease in mean length (so a decrease in growth) when blue light is used as opposed to no light.

    But when they're grown in 1% sucrose solution AND with IAA, there is an increase in growth when blue light is used as opposed to no light.

    I'm unsure about the last mark. It says the effect of the blue light is greater on P, which you can see happens when IAA is used, but Q has a larger decrease in growth in the 1% sucrose solution.
    Offline

    0
    ReputationRep:
    (Original post by Vidja)
    This threw me off a bit as well. Basically, what I think it means is that the plasmid you're using for the vector contains the GFP flourescent protein gene. You insert the desired gene into the centre of the GFP gene, so that the GFP gene is non-functional.

    Now, in some cases, the vector closes up without incorporating the DNA fragment. If this happens, the GFP gene will be working fine, since the desired gene has not been accepted into it. These bacteria will glow. You do not want these bacteria.

    The bacteria whose plasmids have incorporated the desired gene will not have a functioning GFP gene, since the desired gene is in the centre of the GFP gene. In these bacteria, the flourescent protein is not produced, and so these bacteria do not glow.

    I think what's confusing about this is that you aren't testing for the bacteria that have successfly taken up the vector That was achieved by growing them on an antibiotic medium. What you are testing for, is those that have taken up faulty vectors that do not contain your gene.
    Yeh, I think this is probably it. I'm not too worried cos they would have gone into more detail (or written something that actually makes sense) If it were a key bit or the syllabus.

    Just have to do my synoptic revision now grrrrrrrrrrrr
    Offline

    0
    ReputationRep:
    what are the things that are not likely to come up on the synoptic essay (because they've come up already)? this is so stressful, i don't know whether to just skim all synoptic stuff and just mainly revise biol5 or go into detail on all the synoptic stuff
    Offline

    0
    ReputationRep:
    (Original post by tehsponge)
    Okay, its a describe question, so all you have to do is describe what the table shows you. The table shows that for the ones grown in just 1% sucrose solution there is a decrease in mean length (so a decrease in growth) when blue light is used as opposed to no light.

    But when they're grown in 1% sucrose solution AND with IAA, there is an increase in growth when blue light is used as opposed to no light.

    I'm unsure about the last mark. It says the effect of the blue light is greater on P, which you can see happens when IAA is used, but Q has a larger decrease in growth in the 1% sucrose solution.
    hmmm yeah i should have read the question, I was doing this at 1am so i sort of skimmed the table :P They always have to add a point on the mark scheme were they know no one wil get
    Offline

    0
    ReputationRep:
    (Original post by Ramin Gorji)
    okie dokie, translation occurs in tge cytoplasm of the cell. it requires ribosomes and the mRNA created in transcription from the nucleus. 1) ribosomes attach to the first set of codons on the mRNA ( codons are the bases of the mRNA). 2) this provides the template for anticodons ( bases on tRNA) to attach to the codons of the mRNA on the ribosomes. 3) ribosomes move up the mRNA strand and attach tRNA as explained before. 4) tRNA has an amino acid molecule at the end of it clover shaped body. 5) when two or more tRNA molecules are next to each other a peptide bond can be formed by condensation reaction using ATP. 4) this continues until it reaches a group of 3 bases on the codon that are called a stop codon this stops the process of translation and polypeptide is finished. hope I've said most of the important points but youshould have a look attempt power point presentation uploaded either on this page or 1/2 back it has some descent points on it
    Thank you.. ill check the powerpoint out too xx
    Offline

    2
    ReputationRep:
    (Original post by Ramin Gorji)
    hmmm yeah i should have read the question, I was doing this at 1am so i sort of skimmed the table :P They always have to add a point on the mark scheme were they know no one wil get
    Well, for most of the mark schemes there is a lot of discussion which goes on between the head examiners, and they determine whether or not an answer should be added to the mark scheme. Since this is a specimen paper, I'm sure there will be flaws in the mark scheme. I think there should be another mark for saying that Q increases in one, and P in the other.

    Basically, I wouldn't worry about the specimen paper.
    Offline

    0
    ReputationRep:
    Menstrual cycle isn't great!

    Also struggle with the DNA technology part with it being the largest section of Unit 5.
    And as far as the essay is concerned...
    Offline

    2
    ReputationRep:
    (Original post by vickidougal)
    what are the things that are not likely to come up on the synoptic essay (because they've come up already)? this is so stressful, i don't know whether to just skim all synoptic stuff and just mainly revise biol5 or go into detail on all the synoptic stuff
    use my mindmap
    Attached Files
  1. File Type: docx mindmap 2.docx (31.6 KB, 239 views)
    Offline

    0
    ReputationRep:
    Hey,
    Our teacher marks our essays qualitatively not quantitatively, so I'm not sure if what I'm writing is good enough.

    Please can someone post up an essay scoring a high mark?
    Offline

    6
    ReputationRep:
    God dammit the menstrual cycle is such a giant pain, apart from that everything else in this unit seems reasonably straightforward except for the sheer volume of information needed to be learned for DNA technology.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Has a teacher ever helped you cheat?
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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.