ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Biology => Topic started by: Rishi97 on March 10, 2014, 09:36:37 pm
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Hey guys
Since this is yr 12, I'm going to need all the help I can get for Biology
Thanks :D
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Has anyone done the enzyme prac with the enzyme protease and photographic film?
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I have answered some questions for our enzyme sac. Could someone pls check them and feel free to add anything.
1)How do enzymes catalyse reactions?Enzymes catalyse reactions by reducing the activation energy required for a reaction to proceed. The enzyme temporary binds with specific substrates and produces products.
2)Explain Lock and Key model and Induced fit model of enzyme action
Lock and key model- States that the active site & substrate are exactly complementary. Each enzyme is very specific to the substrate.
Induced fit model- Suggests that the enzyme can slightly modify the shape of the active site to accommodate the substrate. (More widely accepted)
3)How does temperature affect enzyme activity?Temperature increases the rate of reaction by increasing the kinetic energy so that more molecules collide more frequently. However, if the temperature exceeds the optimum temperature, the enzymes denature and the rate of reaction stops. If the temperature is below the optimum temp, there is not enough collisions and the rate of reaction decreases.
4)How does pH affect enzyme activity?All enzymes work at an optimum ph. By changing the pH, and increasing or lowering it too much, the enzyme could denature. As a result, the active site with permanently lose its shape, and the enzyme will not be able to conduct anymore reactions.
5)What is meant by the activation energy?
Activation energy is the energy required to start a reaction. Enzymes lower the activation energy.
6)How do enzymes affect activation energy
Enzymes lower the activation energy. (Please add info here-not a very good answer)
7)How does concentration affect enzyme activity?
An increased concentration of enzyme increases enzyme activity, as more enzymes will undergo reactions. A decreased concentration of enzyme will decrease enzyme activity. On the other hand, substrate concentration can also affect enzymes. High substrate concentrations mean enzymes will conduct reactions longer to break down all products. Low substrate concentrations means enzyme will conduct reactions quicker.
Endergonic/ Exergonic reactions
Anabolic/Endothermic – Build-up of molecules
-Requires energy
-6CO2+6H2OC6H12O6 + 6O2 (Photosynthesis)
Catabolic/ Exergonic- Break down of molecules
-Releases energy
-C6O12O6 + 6O2 6CO2 + 6H2O + ENERGY (Cellular respiration)
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I have answered some questions for our enzyme sac. Could someone pls check them and feel free to add anything.
1)How do enzymes catalyse reactions?Enzymes catalyse reactions by reducing the activation energy required for a reaction to proceed. The enzyme temporary binds with specific substrates and produces products.
2)Explain Lock and Key model and Induced fit model of enzyme action
Lock and key model- States that the active site & substrate are exactly complementary. Each enzyme is very specific to the substrate.
Induced fit model- Suggests that the enzyme can slightly modify the shape of the active site to accommodate the substrate. (More widely accepted)
3)How does temperature affect enzyme activity?Temperature increases the rate of reaction by increasing the kinetic energy so that more molecules collide more frequently. However, if the temperature exceeds the optimum temperature, the enzymes denature and the rate of reaction stops. If the temperature is below the optimum temp, there is not enough collisions and the rate of reaction decreases.
4)How does pH affect enzyme activity?All enzymes work at an optimum ph. By changing the pH, and increasing or lowering it too much, the enzyme could denature. As a result, the active site with permanently lose its shape, and the enzyme will not be able to conduct anymore reactions.
5)What is meant by the activation energy?
Activation energy is the energy required to start a reaction. Enzymes lower the activation energy.
6)How do enzymes affect activation energy
Enzymes lower the activation energy. (Please add info here-not a very good answer)
7)How does concentration affect enzyme activity?
An increased concentration of enzyme increases enzyme activity, as more enzymes will undergo reactions. A decreased concentration of enzyme will decrease enzyme activity. On the other hand, substrate concentration can also affect enzymes. High substrate concentrations mean enzymes will conduct reactions longer to break down all products. Low substrate concentrations means enzyme will conduct reactions quicker.
Endergonic/ Exergonic reactions
Anabolic/Endothermic – Build-up of molecules
-Requires energy
-6CO2+6H2OC6H12O6 + 6O2 (Photosynthesis)
Catabolic/ Exergonic- Break down of molecules
-Releases energy
-C6O12O6 + 6O2 6CO2 + 6H2O + ENERGY (Cellular respiration)
For your first answer, I'd add that it reduces activation energy by weakening bonds in the substrate molecule. Also, activation energy is the energy required for a reaction to begin not 'proceed'
Your second answer is spot on!
For your fourth answer, you could say 'altering' not changing :)
For your sixth answer, be a bit more specific - consider how activation energy is reduced?
I'd say something like "Enzymes weaken the bonds in the substrate/s molecule/s which in turn reduces the activation energy hence enabling the reaction to commence and proceed at a faster rate"
Hmm I don't know why anabolic reactions have been compared with endothermic reactions. You're being specific which is good but if you're describing it in general terms, then anabolic reactions are endergonic. Endothermic reactions are simply a category of endergonic reactions.
In regards to your description of an exergonic reaction, alongside referring to it as a decomposition reaction, also mention that it releases energy.
:) Hope this helped and please forgive me if I've made any mistakes.
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Thanks a lot nermmb. No no, you're answers are perfect.
oops, I meant to say endergonic not endothermic. Thanks for correcting me :D
btw, you probs don't remember but you helped me heaps for my previous sac on osmosis. The answers you gave for each of the questions were perfect and I ended up getting a good mark for the sac. SO THANK YOU :D
If u ever need help, ask away :)
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Thanks a lot nermmb. No no, you're answers are perfect.
oops, I meant to say endergonic not endothermic. Thanks for correcting me :D
btw, you probs don't remember but you helped me heaps for my previous sac on osmosis. The answers you gave for each of the questions were perfect and I ended up getting a good mark for the sac. SO THANK YOU :D
If u ever need help, ask away :)
Aww :") Thanks Rishi97! I'm sure I'll need help haha atm cellular respiration is like a slow killer for me :P
No need to thank me honestly, that's the spirit of the AN community and I'm sure that you scored well because you were genuinely prepared (not because of my answers) :D and trust me, the number of times I make mistakes in my answers is crazy haha my teacher always criticises me for it!
Absolutely Best of luck!
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Hi
Could you pls help me with some qs from the biozone worksheets?
1) Explain the importance of compartmentalisation in the mitochondria
2) Explain why thermoregulation is associated with energy expenditure.
Thanks ;D
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Hi
Could you pls help me with some qs from the biozone worksheets?
1) Explain the importance of compartmentalisation in the mitochondria
2) Explain why thermoregulation is associated with energy expenditure.
Thanks ;D
1. Compartmentalisation localises different cellular reactions to different regions within the mitochondria, which in turn increases the efficiency of the organelle.
2. Energy is required to produce heat, and in turn regulate body temperature.
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Hi
Could you pls help me with some qs from the biozone worksheets?
1) Explain the importance of compartmentalisation in the mitochondria
2) Explain why thermoregulation is associated with energy expenditure.
Thanks ;D
Wow tough questions, I'll have a go :)
1. The mitochondria is the sight of one of some of the most vital cellular processes and thus stores enzymes required for the processes to occur. Compartmentalisation within the mitochondria enables these processes to occur in regions which satisfy the requirements of these processes such as large surface area and abundance of necessary enzymes.
2. Energy, in cellular reactions, is expended in many forms such as heat which is necessary to maintain a constant body temperature, thermoregulation, which in turn enables enzymes to function at their optimum temperature hence allowing reactions to continue occurring at desirable conditions.
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Thanks oddly and nerdmmb for answering...This has really helped ;)
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What are the inputs and outputs of photosynthesis?
I'm confused because, do I have to name the specific ones for each stage such as NADPH2?
Thanks :)
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I have a biology SAC tomorrow and we are doing the prac where leaf discs are placed in bicarbonate solution.
Why do the leaf disks sink when a vacuum in the syringe is created?
Thanks
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What are the inputs and outputs of photosynthesis?
I'm confused because, do I have to name the specific ones for each stage such as NADPH2?
Thanks :)
Yes, you'll need to be specific but you are not required to write down the quantity.
For the light dependent stage:
Inputs: H2O+ 18ADP + 18Pi + NADP+
Outputs:6O2 (waste product) +18ATP + NADPH
For the light independent stage:
Inputs: 6CO2 + 18ATP + NADPH
Outputs: C6H12O6 + 6H2O + NADP+ + 18ADP +18Pi
Also, an NADP molecule can only hold upto 1 hydrogen not two.
Hope this helped :)
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thanks soooo much nerdmmb. You r such a big life saver :)
Also, when you say, an NADP molecule can only hold one hydrogen, will it be just NADPH? Cause our teacher said NADPH2. Now I'm getting really confused.
Is it necessary to write water as an output for the light independent stage?
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thanks soooo much nerdmmb. You r such a big life saver :)
Also, when you say, an NADP molecule can only hold one hydrogen, will it be just NADPH? Cause our teacher said NADPH2. Now I'm getting really confused.
Is it necessary to write water as an output for the light independent stage?
NADP reduces to NADPH +H+ when it accepts electrons. However, you can probably write it as NADPH2 as well.
It's not necessary to include water as an output, but just ensure that you only include 6H2O for the inputs of the light dependent stage.
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oh ok thanks :)
So would I still be correct if I just wrote NADPH for the output of the light dependent stage?
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oh ok thanks :)
So would I still be correct if I just wrote NADPH for the output of the light dependent stage?
I think so, because many textbooks just leave it at that
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What is the role of NADP+ reductase in light dependent reactions?
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What is the role of NADP+ reductase in light dependent reactions?
It reduces NADP+
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It reduces NADP+
It reduces NADP+ to make NADPH???
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It reduces NADP+ to make NADPH???
Yup :)
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At school when we learnt about cellular respiration, our teacher explained that there are 4 stages:
- Glycolysis
- Link reaction
- Krebs cycle
- Electron transport chain
But in the textbook, they havent mentioned the link reaction at all. Why is that?
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At school when we learnt about cellular respiration, our teacher explained that there are 4 stages:
- Glycolysis
- Link reaction
- Krebs cycle
- Electron transport chain
But in the textbook, they havent mentioned the link reaction at all. Why is that?
Hmm, what textbook are you using btw? NoB (3rd edition) has it on page 83 Figure 3.30.
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Hmm, what textbook are you using btw? NoB (3rd edition) has it on page 83 Figure 3.30.
I'm using NoB (4th edition) and the link reaction isn't even mentioned
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I'm using NoB (4th edition) and the link reaction isn't even mentioned
Ah, the newer books usually have some stuff cut out, so that's probably why..
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Describe two mechanisms that operate to restore homeostasis after infection by a pathogenThe questions from biozone are soo hard :(
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Describe two mechanisms that operate to restore homeostasis after infection by a pathogenThe questions from biozone are soo hard :(
biozone doesn't specifically cover VCE course
"In Unit 3, coordination and regulation are considered at the cellular, rather than whole organism, level. Hence, references to homeostasis and feedback mechanisms have been deleted from Unit 3. The treatment of homeostasis at a systems level, including feedback mechanisms, involving hormonal control (for example, regulation of blood glucose), water balance and temperature control, is included in Unit 2 Biology."
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Why do hormones require a second messenger protein in order to have their signal detected within a cell?
Is it because they are soluble in water?
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Why do hormones require a second messenger protein in order to have their signal detected within a cell?
Is it because they are soluble in water?
Remember that for hormones to work in the body, we only require a very very very very very very small concentration of hormones, hence, by using second messenger, only that little amount can amplified itself in the signal transduction process and produce great effect, much more efficient.
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Why do hormones require a second messenger protein in order to have their signal detected within a cell?
Is it because they are soluble in water?
This is actually technically not always the case. Some hormones don't have any second messenger.
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Why do hormones require a second messenger protein in order to have their signal detected within a cell?
Is it because they are soluble in water?
The majority of hormone classes can squeeze through the membrane but keep in mind peptide hormones are hydrophillic (lipophobic) to a degree. This class of hormones usually attaches to receptors on the surface of the cell which in turn produces a second messenger (because they would find it difficult to get into the cell itself). As mentioned, amplification of the signal is another reason as well.
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Could someone please kindly check my answer :)
1)What occurs in the body when glucose levels are
a.High?
Cells in the pancreas detect rise
Beta cells produce INSULIN
Insulin stimulates muscles + liver cells to absorb glucose
Glucose is converted to glycogen
b.Low?
Cells in the pancreas detect drop
Alpha cells produce GLUCAGON
Glucagon stimulates the liver to release glucose
Glycogen is converted to glucose
2)What are the hormones involved in the regulation of glucose levels in the blood?
Insulin and glucagon
3)What are the glands that produce the hormones that regulate glucose?
The pancreas is a gland that regulates glucose levels by producing insulin and glucagon
4)What is meant by the terms hypoglycaemia and hyperglycaemia?
Hypoglycemia is a condition in which the blood glucose levels in the body are lower than the required range
Hyperglycemia is a condition in which the blood glucose levels in the body are higher than the required range.
5)What is negative feedback?
The negative feedback system is a system of control which detects a change in a variable (e.g.: decrease) and action occurs to produce a change in the opposite direction (e.g. increase)
6)Be able to write a flow chart including, sensors, stimulus, effector and response. (including negative feedback)Stimulus sensors effector response
Stimulus Receptor Effector Signal transduction Response
7)What is signal transduction? How does it differ depending on the type of hormone?
Signal transduction is a chain of events that transmits and amplifies a signal to get a particular cellular response.
How it works:
-The receptor receives a stimulus (protein or lipid)
-The G-protein detects this stimulus and changes shape
-The G-protein transmits the message to the secondary messengers
-The secondary messengers amplify the required response so it occurs in less time
Types of hormones:-
PROTEIN- If the hormones are proteins, then it cannot travel through the cell membrane since it’s not lipid soluble. Protein hormones (stimulus) have receptors on the cell membrane. When leaving a cell, the protein hormones use vesicles.
-LIPIDS- If the hormones are lipids, then it can travel through the cell membrane since it is lipid-soluble. Lipid hormones (stimulus) have receptors inside the cell/ in the cytoplasm.
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List the major steps involved in humoral immunity
Thanks :)
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List the major steps involved in humoral immunity
Thanks :)
Note that B-cells have membrane bound IgM and IgD that have the same antigen specificity.
When B-cells encounter their antigen at least two membrane bound antibodies must attach to it. This will initiate endocytosis of the antigen, and digestion of its peptide portions for presentation on MHC-II.
Circulation activated T-helper cells can then recognize MHC-peptide complex on their surface and secrete IL-4 which helps activate the B-cell.
The B-cell can then divide and differentiate into plasma cells which secrete antibody and into memory cells.
Memory cells in circulation can form germinal centers around follicular dendritic cells in the lymph nodes and spleen where they can undergo affinity maturation and class switching.
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Note that B-cells have membrane bound IgM and IgD that have the same antigen specificity.
When B-cells encounter their antigen at least two membrane bound antibodies must attach to it. This will initiate endocytosis of the antigen, and digestion of its peptide portions for presentation on MHC-II.
Circulation activated T-helper cells can then recognize MHC-peptide complex on their surface and secrete IL-4 which helps activate the B-cell.
The B-cell can then divide and differentiate into plasma cells which secrete antibody and into memory cells.
Memory cells in circulation can form germinal centers around follicular dendritic cells in the lymph nodes and spleen where they can undergo affinity maturation and class switching.
Wow..that is some sophisticated vocab.I haven't even heard half these words :/
This is what I wrote:
- Macrophages engulf pathogens and display the pathogen's anitigens on their surface
- T-helper cells are attracted to the macrophage and stimulate B-cells
- The B-cells produce plasma cells and memory cells
- The plasma cells produce antibodies which form antibody-antigen complexes
- The B-memory cells stay in the body until there is a second infection. It reacts more vigorously towards the pathogen the second time round.
Is this right?
Thanks :)
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Wow..that is some sophisticated vocab.I haven't even heard half these words :/
This is what I wrote:
- Macrophages engulf pathogens and display the pathogen's anitigens on their surface
- T-helper cells are attracted to the macrophage and stimulate B-cells
- The B-cells produce plasma cells and memory cells
- The plasma cells produce antibodies which form antibody-antigen complexes
- The B-memory cells stay in the body until there is a second infection. It reacts more vigorously towards the pathogen the second time round.
Is this right?
Thanks :)
That's perfect! Nothing wrong with that, just if willing, learn some biological terminology to enhance your answer's credibility! :)
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I actually think it can be better to use simple/less complex terminology in VCE Biol...otherwise it's easier to make a mistake and difficult for the examiner to mark. The examiner is only looking for things in the study design. There's nothing wrong with what either of you wrote but you won't get extra marks for mentioning things like affinity maturation or class switching, nor will it enhance your answer, because (afaik, or at least when I did VCE Biol) they're not in the study design. Good job being enthusiastic about immuno though :D
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Wow..that is some sophisticated vocab.I haven't even heard half these words :/
This is what I wrote:
- Macrophages engulf pathogens and display the pathogen's anitigens on their surface
- T-helper cells are attracted to the macrophage and stimulate B-cells
- The B-cells produce plasma cells and memory cells
- The plasma cells produce antibodies which form antibody-antigen complexes
- The B-memory cells stay in the body until there is a second infection. It reacts more vigorously towards the pathogen the second time round.
Is this right?
Thanks :)
I'd write that subsequent expose to that antigen results in greater/faster production of specific antibodies due to the presence of memory B cells. "More vigorous" is a bit too vague
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I'd write that subsequent expose to that antigen results in greater/faster production of specific antibodies due to the presence of memory B cells. "More vigorous" is a bit too vague
I'm not too sure about Rishi, but my teacher reiterated that it was more 'vigorous' and the Nelson Biology or NoB not too sure which one I recall it from, states that it acts more vigorously! Just saying :)
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I'm not too sure about Rishi, but my teacher reiterated that it was more 'vigorous' and the Nelson Biology or NoB not too sure which one I recall it from, states that it acts more vigorously! Just saying :)
Well, yeah, the immune response is more vigorous, but you're unlikely to be awarded marks for writing that if you get a question about memory cells. It doesn't really demonstrate any understanding of the concept. You've gotta be specific! :)
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How can you acquire immunity through natural and passive strategies?
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How can you acquire immunity through natural and passive strategies?
This should definitely help
http://classes.midlandstech.edu/carterp/Courses/bio225/chap17/17-01_AcqImmunity.jpg
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This should definitely help
http://classes.midlandstech.edu/carterp/Courses/bio225/chap17/17-01_AcqImmunity.jpg
Omg just what I needed :)
Thanks Reus
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1) Why are hormonal responses generally longer lasting?
2) What is the difference between hormones and pheromones?
Thanks guyysss :)
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1) Why are hormonal responses generally longer lasting?
2) What is the difference between hormones and pheromones?
Thanks guyysss :)
1. The Humoral Response creates a large number of antibodies specific to the antigen, and a large number of Memory B-Cells. This is longer lasting in terms of immunity as next time the antigen invades, a form of defence mechanism is ready.
2. Hormones are chemical signalling molecules which travel in the blood stream directly to their target tissues to induce a specific response. This works within the means of the organism itself. Pheromones however, are chemical signalling molecules which travel through the atmosphere, causing a change in behaviour on members on the same species.
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1) they stay around longer; neurotransmitters are rapidly broken down/absorbed after binding to a post synaptic neuron, to prevent over stimulation; generally affect gene expression
2) hormones are secreted by endocrine cells into the internal environment and exert an effect on target cells with specific receptors, whereas pheromones are secreted by exocrine cells into the external environment and exert an effect on organisms of the same species
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1) Describe the steps involved in forming a functional enzyme comprising two polypeptide chains
2) What is the significance of the anti-parallel nature of DNA?
Thanks heaps
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1) Describe the steps involved in forming a functional enzyme comprising two polypeptide chains
2) What is the significance of the anti-parallel nature of DNA?
Thanks heaps
1) enzymes can have tertiary or quaternary structure. If an enzyme is composed of 1 polypeptide chain, it's tertiary. If an enzyme is composed of 2 polypeptide chains, it's quaternary. So basically, 2 polypeptide comes and aggregates, stabilising the structure by Hydrogen bond etc. (I only know this much details about the process :( ).
2) Cause you are doing Chem 3/4, you probably remember that the phosphate is bonded to the 5' Carbon whilst the nitrogenous base is bonded to the 1' Carbon. On a piece of paper, try and draw 2 single DNA strands from 5' -> 3'. If you draw it this way, do you see that it's impossible for the nitrogenous base to "face" each other and create H-bond between them? Hence, this is why you need anti-parallel structure (this is not examinable in Bio but probably in Chem :D )
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1) Describe the steps involved in forming a functional enzyme comprising two polypeptide chains
2) What is the significance of the anti-parallel nature of DNA?
Thanks heaps
1. This is a question that if asked on an exam, would probably be broken up into a, b, c, etc. You'd probably be asked to explain the synthesis of individual polypeptide chains, and how these two polypeptide chains then join together in a particular manner, to form an overall 3-D shape to the enzyme with an active site of a specific conformation (as you know, specifically complementary to the shape of the specific substrate in which it binds to). So, I'd say in VERY summarised terms:
1. Each polypeptide chain comprising the enzyme are synthesised via the protein-synthesis pathway (i.e. transcription and translation).
2. The polypeptide chains are joined together in a specific manner by (not 100% sure, but I think) covalent (peptide) bonds.
3. The protein molecule adopts an overall 3D shape with an active site of a specific conformation specifically complementary to the shape of the substrate in which it joins to.
2. If this was ever asked, it would be a suggest question because this isn't really examinable in the Biology syllabus. The nitrogenous bases chemically bond to their corresponding, complementary base by hydrogen bonds, which ultimately connects the two strands of polynucleotides together to form DNA. By having two anti-parallel strands of DNA, the bases are able to face each other in a manner that the bases can chemically bond together, and thus allow the DNA molecule be double-stranded. Again, knowing this in Chem is probably important, but it's not assessed in Biology to this degree.
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1. This is a question that if asked on an exam, would probably be broken up into a, b, c, etc. You'd probably be asked to explain the synthesis of individual polypeptide chains, and how these two polypeptide chains then join together in a particular manner, to form an overall 3-D shape to the enzyme with an active site of a specific conformation (as you know, specifically complementary to the shape of the specific substrate in which it binds to). So, I'd say in VERY summarised terms:
1. Each polypeptide chain comprising the enzyme are synthesised via the protein-synthesis pathway (i.e. transcription and translation).
2. The polypeptide chains are joined together in a specific manner by (not 100% sure, but I think) covalent (peptide) bonds.
3. The protein molecule adopts an overall 3D shape with an active site of a specific conformation specifically complementary to the shape of the substrate in which it joins to.
2. If this was ever asked, it would be a suggest question because this isn't really examinable in the Biology syllabus. The nitrogenous bases chemically bond to their corresponding, complementary base by hydrogen bonds, which ultimately connects the two strands of polynucleotides together to form DNA. By having two anti-parallel strands of DNA, the bases are able to face each other in a manner that the bases can chemically bond together, and thus allow the DNA molecule be double-stranded. Again, knowing this in Chem is probably important, but it's not assessed in Biology to this degree.
Hi Yacoubb, I'm pretty sure there's no peptide bond in the Quaternary structure here. It is maintained by the same type of bonds in Tertiary :D. But again, we will not turn this into a Chemistry thread!
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Hi Yacoubb, I'm pretty sure there's no peptide bond in the Quaternary structure here. It is maintained by the same type of bonds in Tertiary :D. But again, we will not turn this into a Chemistry thread!
Yeah I was doing an exam once for Biology, and it asked what type of bond it was, and the answer said covalent bond. I just assumed it was peptide given it was a protein. But yeah, this isn't knowledge needed for Biology :)
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During DNA Replication:
A) Messenger RNA (mRNA) is produced
B) reverse transcriptase enzymes play an important role
C) bonds between phosphate and sugar molecules break
D) each of the DNA strands acts as a template strand
I thought the answer was A but I was wrong so could someone please explain why
Thanks :)
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The answer should be D. mRNA is produced during protein synthesis (transcription).
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During DNA Replication:
A) Messenger RNA (mRNA) is produced
B) reverse transcriptase enzymes play an important role
C) bonds between phosphate and sugar molecules break
D) each of the DNA strands acts as a template strand
I thought the answer was A but I was wrong so could someone please explain why
Thanks :)
A is incorrect, as mRNA is produced in transcription
B is incorrect, as reverse transcriptase is an enzyme that helps a DNA strand be "reverse transcripted" from a pre-existing RNA strand.
C is incorrect, as the breaking of phosphate and sugar bonds indicates the breaking down of a nucleotide, which does not occur in DNA replication
By process of elimination, D is correct.
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A is incorrect, as mRNA is produced in transcription
B is incorrect, as reverse transcriptase is an enzyme that helps a DNA strand be "reverse transcripted" from a pre-existing RNA strand.
C is incorrect, as the breaking of phosphate and sugar bonds indicates the breaking down of a nucleotide, which does not occur in DNA replication
By process of elimination, D is correct.
Thanks dankfrank that makes soo much more sense now :)
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-What are the two ways meiosis produces variation?
Thanks
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-What are the two ways meiosis produces variation?
Thanks
- Genetic recombination in prophase I
- Independent assortment in metaphase I and to a lesser extent metaphase II
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- Genetic recombination in prophase I
- Independent assortment in metaphase I and to a lesser extent metaphase II
Thanks Scooby
By genetic recombination, you mean 'crossing over' right?
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Thanks Scooby
By genetic recombination, you mean 'crossing over' right?
Exactly that :D
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Describe 2 features of restriction enzymes that vary in the way they cut DNA
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What is the difference between PCR and gene cloning?
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What is the difference between PCR and gene cloning?
This site has on point information, helped me so it may help you! :)
http://www.majordifferences.com/2013/10/difference-between-gene-cloning-and-pcr.html#.U9YvXV7vbfM
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This site has on point information, helped me so it may help you! :)
http://www.majordifferences.com/2013/10/difference-between-gene-cloning-and-pcr.html#.U9YvXV7vbfM
Perfect!!! Just the areas that I needed clarification on
Thanks Reus :)
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Would I be correct to say that primers "instruct" the DNA polymerase to start replicating the DNA strand in PCR?
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Would I be correct to say that primers "instruct" the DNA polymerase to start replicating the DNA strand in PCR?
I don't think they instruct..
If I'm not mistaken, they just act as a starting point for the attachment of DNA/RNA polymerase.
:)
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Would I be correct to say that primers "instruct" the DNA polymerase to start replicating the DNA strand in PCR?
They give you the replication fork, which as nerdmmb said, is where DNA pol can attach
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The human growth hormone consists of 14 amino acids. The minimum number of codons for this hormone would be:
a) 14
b) 16
c) 42
d) 48
Thanks :D
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The human growth hormone consists of 14 amino acids. The minimum number of codons for this hormone would be:
a) 14
b) 16
c) 42
d) 48
Thanks :D
Don't three amino acids make one codon?
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Don't three amino acids make one codon?
I thought it was 3 nucleotides make up one codon which codes for one amino acid.
Not sure though
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I thought it was 3 nucleotides make up one codon which codes for one amino acid.
Not sure though
You're right
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I thought it was 3 nucleotides make up one codon which codes for one amino acid.
Not sure though
Haha sorry, got them mixed up! Yep, they do. A codon codes for one amino acid.
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Haha sorry, got them mixed up! Yep, they do. A codon codes for one amino acid.
ok so do you know how to get the answer?
I did 14 x 3 and so circled 42 but my teacher said that the correct answer is 16! How?
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Should be 42..
Edit: my bad, got it mixed up. It's probably 16. So each amino acid is coded by one codon. But you have to take into account stop and start codons. therefore 14 + 2 = 16.
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Should be 42..
Yeah thought so... i'll ask him tomorrow and hopefully grab that extra mark :P
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Yeah thought so... i'll ask him tomorrow and hopefully grab that extra mark :P
your teacher is right i think. the questions asks how many codons there are, which are the base triplets codes. so if there are 14 amino acids, each will have one codon which is made up of three base pairs.
then in your sequence you need the start and stop codons as well, so that makes 16 codons total.
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The human growth hormone consists of 14 amino acids. The minimum number of codons for this hormone would be:
a) 14
b) 16
c) 42
d) 48
Thanks :D
As you have said earlier, a codon codes for an amino acid, hence, the number of coding codon = number of amino acids. So, If you multiply 3 by 14, what you are getting is the number of nucleotides on the mRNA, not the number of codons.
Remember one of the non-coding codon that we can have is the stop codon, which can be either UAA, UAG or UGA. when the ribosome reaches a stop codon, instead of an amino acid, termination factor will come into place, causing the ribosome to break apart. Hence, the number of coding codons + non-coding codons can be >=15. And 16 is a next lowest number I can get.
Correct me if I'm wrong.
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your teacher is right i think. the questions asks how many codons there are, which are the base triplets codes. so if there are 14 amino acids, each will have one codon which is made up of three base pairs.
then in your sequence you need the start and stop codons as well, so that makes 16 codons total.
Yeah I agree with you, but the dodgy thing about this question is, AUG (the start codon) actually codes for an amino acid : Methionine. Hence, it should have been considered in the polypeptide chain as well. I would have answered 15 if this is a short-answer question.
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Yeah I agree with you, but the dodgy thing about this question is, AUG (the start codon) actually codes for an amino acid : Methionine. Hence, it should have been considered in the polypeptide chain as well. I would have answered 15 if this is a short-answer question.
actually that's true, i didn't think about that. it's definitely a pretty dodgy question - whichever company wrote it (hopefully it wasn't vcaa) clearly didn't think it through :P
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actually that's true, i didn't think about that. it's definitely a pretty dodgy question - whichever company wrote it (hopefully it wasn't vcaa) clearly didn't think it through :P
haha it was NEAP but that was a very dodgy question
Thanks everyone for your help :)
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Minimum number would have to be 15. Those of you have cried foul are quite right to.
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In regards to comparative anatomy, would the human appendix be an example of a vesitigial structure?
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In regards to comparative anatomy, would the human appendix be an example of a vesitigial structure?
There's evidence to suggest that it is
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In regards to evolution, what is selection pressure?
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In regards to evolution, what is selection pressure?
Just various things that influence a populations behaviours depending on the phenotypes of the particular gene pool.
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Could someone please help me the following questions?
- What is the role of reverse transcriptase in "Gene Cloning"?
- How can a mutation in a single base be as damaging as a mutation in a sequence of bases?
- Explain how mutation can be harmful or beneficial
- Explain why non-disjunction in meiosis 1 results in a higher proportion of faulty gametes than non-disjunction in meiosis II
Big thanks to y'all
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Could someone please help me the following questions?
- What is the role of reverse transcriptase in "Gene Cloning"?
- How can a mutation in a single base be as damaging as a mutation in a sequence of bases?
- Explain how mutation can be harmful or beneficial
- Explain why non-disjunction in meiosis 1 results in a higher proportion of faulty gametes than non-disjunction in meiosis II
Big thanks to y'all
1. Reverse transcriptase, as the name suggests, is an enzyme which catalyses the production of complementary DNA (cDNA) from an RNA template strand. In gene cloning, by inserting a gene of interest in the form of mRNA into bacteria, along with reverse transcriptase, the gene of interest can then be inserted into the bacteria's genome (transforming it). So reverse transcriptase would convert mRNA into complementary cDNA, which can then be integrated into the bacteria's genome. As the bacteria undergoes binary fission, the gene which the original mRNA codes for is cloned.
2. As mutations are random, you can't really determine that unless you're given an example. So a point mutation which results in the same amino acid (as DNA is redundant; each amino acid can be by more than one DNA triplet) is "harmless", compared to another point mutation which results in a stop codon (which is serious). A mutation in several bases may or may not be more harmful than a point mutation. But I'd say the probability of it harbouring more harm is greater.
3. Mutations which result in alleles which contribute to a phenotype that is selected for or favourable in an organism's environment is beneficial. But as mentioned, they can also be harmful - and usually are (e.g. stop codons).
4. Okay, so think of the reductive division of meiosis; homologous chromosomes are separated from each other into two different daughter cells. Say we've got 2 chromosome-20s and two chromosome-21s. Non-disjunction would cause one daughter cell to have, say, two chromosome-20s and one chromosome-21 (extra one). The other daughter cell would then have only one chromosome-21 (less one). So both daughter cells would be faulty. Then meiosis II occurs which results in 4 gametes: two gametes would have chromosome-21, 2 x chromosome-20s (n+1) and the other two gametes would only have chromosome-21 but no 22 (n-1). So they would all be faulty.
If non-disjunction occurred in meiosis II, then only two cells would be abnormal (one is n+1 the other is n-1).
It's best to explain these types of questions with diagrams haha
Hope that helps :)
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Here is a challenging question:
Theoretically, what proportion of offspring from a cross between parental genotypes Pp;Qq;Rr;Ss and Pp;qq;Rr;Ss would have the genotype pp;qq;rr;ss?
a. 1/256
b. 1/128
c. 1/64
d. 1/32
THANK YOU!! :-)
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Here is a challenging question:
Theoretically, what proportion of offspring from a cross between parental genotypes Pp;Qq;Rr;Ss and Pp;qq;Rr;Ss would have the genotype pp;qq;rr;ss?
a. 1/256
b. 1/128
c. 1/64
d. 1/32
THANK YOU!! :-)
1/128
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1/128
could you please give a brief explanation of how you did it?
Thanks Mr T-Rav :)
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could you please give a brief explanation of how you did it?
Thanks Mr T-Rav :)
You look at the traits one by one.
Parents: Pp;Qq;Rr;Ss and Pp;qq;Rr;Ss
Offspring: pp;qq;rr;ss
So let's look at trait "P" first and forget about everything else. The cross we get is:
Pp x Pp
You should know by now that the chance of getting pp out of this is 1/4 (this is the monohybrid cross).
Now let's look at trait "Q". The cross we get is:
Qq x qq
So the chance of getting qq (in the offspring) is 1/2
We do the same for trait "R" and trait "S". Each time we just forget about the other traits and look at the probability of getting the genotype we get in the offspring.
So our probabilities are:
P(pp)=1/4
P(qq)=1/2
P(rr)=1/4
P(ss)=1/4
Now what we have to do is whack all these probabilities together:
1/4 x 1/2 x 1/4 x 1/4 = 1/128
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In prokaryotic organisms
A. translation occurs at the ribosome
B. transcription occurs in the nucleus
C. chromosomes are usually linear
D. DNA is only found in plasmids
I thought the answer was D but it says A :(
Could you also provide a brief explanation?
Thanks guys
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In prokaryotic organisms
A. translation occurs at the ribosome
B. transcription occurs in the nucleus
C. chromosomes are usually linear
D. DNA is only found in plasmids
I thought the answer was D but it says A :(
Could you also provide a brief explanation?
Thanks guys
Prokaryotic cells do have ribosome. Ribosome is not a membrane bound structure. DNA is not only found in plasmid, a prokaryote can have DNA in its main circular chromosome and plasmid. Plasmid contains all the DNA that are transmitted from others bacteria and help the cell to gain resistance, whilst the main chromosome contains its own genetic material.
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Prokaryotic cells do have ribosome. Ribosome is not a membrane bound structure. DNA is not only found in plasmid, a prokaryote can have DNA in its main circular chromosome and plasmid. Plasmid contains all the DNA that are transmitted from others bacteria and help the cell to gain resistance, whilst the main chromosome contains its own genetic material.
Just to add to this, the circular chromosome within prokaryotes codes for majority of the cell's proteins :)
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What is the difference between divergent evolution and parallel evolution?
Also, what is the difference between adaptive radiation and divergent evolution?
:p
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What is the difference between divergent evolution and parallel evolution?
Also, what is the difference between adaptive radiation and divergent evolution?
:p
Parallel evolution: two species which diverge from a common ancestor and independently evolve common features not present in the common ancestor due to similar selection pressures.
Divergent evolution: two species which diverge from a common ancestor and evolve different features due to different selection pressures.
Adaptive radiation is a specific type of divergent evolution that results in many species evolving from a common ancestor. :)
In exam questions, they'll sometimes ask for the mode of evolution present in an example given. VCAA will accept either divergent evolution or adaptive radiation from what I can see in past reports. :)
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What is the difference between divergent evolution and parallel evolution?
Also, what is the difference between adaptive radiation and divergent evolution?
:p
Good thing to note is that parallel evolution is not on the study design. Not too sure about adaptive radiation since it doesn't make a specific reference to it, but it's a good thing to know nonetheless
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Good thing to note is that parallel evolution is not on the study design. Not too sure about adaptive radiation since it doesn't make a specific reference to it, but it's a good thing to know nonetheless
Yup, if they ask for the pattern of evolution and you write coevolution or parallel evolution, they won't give you a mark for it
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Good thing to note is that parallel evolution is not on the study design. Not too sure about adaptive radiation since it doesn't make a specific reference to it, but it's a good thing to know nonetheless
Adaptive radiation is. I've come across it in an examiner's report :)