nexttttt (5 Viewers)

[danz90]

I think the Cochlea is the overall sort of structure then the organ of corti is more specific and the coil in the middle of the cochlea

my teacher said that the hair cells are collectively known as the organ of corti. the cochlea is that spirally bony structure, that consists of the three canals, which HOUSES the organ of corti.

 

[gloworm14]

the cochlea contains the receptors for sound from what i remember from the top of my head, or should i say from the side of my head?
if not the receptors for sound, i know it has the receptors for something lol

 

[pbillabong]

hey for ppl doing human story, any ideas for examples in dot point 6.1?

 

[hoochiscrazy]

hey guys, do this hsc revision quiz i just knocked up.

post ur answers here, so we can kinda share answers, critique others etc. i reckon it'll work good, make us feel ready for tomorrow.

its attached as a PDF.

A) DNA or deoxyribonucleic acid is in the shape or a ladder. where the sides consist of phosphate and sugar (deoxyribon). Attached to the sugar is the 'rungs' of the ladder. These 'rungs' are made of 2 of the 4 nucleotides thymine, cytosine, guanine and adenine. The shape of each of these nucleotides are so they are complementry meaning that thymine can only join with adenine and cytosine can only join with guanine. Once the DNA is made the 'ladder' is then coiled into a double helix shape.

B) The diagram of the enzyme shows that there are active sites. These active sites are then used by the substrate so the reaction requires less energy and are quicker. Because there are a limited number of active sites there is a limit to how many substrates can be processed at one time. Increasing the substrate will increase the reaction rate until all the active sites are occupied.

C) Genotype + environment=Phenotype. The environment limits to what extent the genotype of an individual is expressed for example if a pea plant that has a genotype to be tall but doesnt have sufficient minerals, light ect the pea plant will not develop to be tall. Another example of the is the plant hydrangeas. Depending on the pH of the soil it is grown in will influence the colour of its flower e.g if it is grown in an acidic soil the flowers will be blue. In a neutral or basic soil pale pink or whitish.

D) I) Virus
II) Fungus- Viruses are non-cellular where most fungi are multi-cellurlar. Fungi can be treated by antibiotics and viruses cannot no know cure but their are vaccines. Viruses need a cell so they can reproduce within it.
III) Jesus! havnt finished my revision for this bit yet lol

E)I) Dont know for sure but im gonna guess phloem since in part II it says substanceS.
II) Substances such as sugars, water to some extent as a solvent, minerals, vitamins, photosynthesis produces as well as transpiration wastes/ products.
III) Movement within the phloem uses the sink-path-source theory. Sugars or other materials that are needed to be transported are move into the phloem through active transport at the source end. Because the concentration of materials is high water follows by osmosis. At the sink end Materials are being removed (water then follows again by osmosis) through active transport. This creates a pressure gradient as there is high pressure at the source end and low at the sink and where materials are being removed. This creates a flow from the Source to the sink.

 

[hoochiscrazy]

Do we need to know much about Burnette Macfarlan? Or just know the stuff he discovered since its pretty relevant?

Edit: Also do we need to know how cytptoxic t-cells kill infected cells? e.g releases perforin.

How much detail is needed on the effectiveness of vaccination programs for small pox, diptheria and polio??

 

[aussiechick007]

^ *macfarlane burnet

 

[hoochiscrazy]

^ *macfarlane burnet

lol my bad hand writing and wtf kind of first name is Macfarlane!

 

[midifile]

For danzs questions

a. DNA is a double stranded molecule twisted into a helix. It is composed of two strands of nucleotides. Each nucleotide consist of a phosphate molecule, a sugar (deoxyribose) and nitrogenous base (either adenine, thymine, guanine or cytosine). Adenine will bond with thymine and guanine bonds with cytosine forming hydrogen bonds between them.

b. The reaction eventually reaches a point of saturation. This occurs when every enzyme is catalysing a reaction with substrates. Once the reaction has reached this point, even if you increase sustrate concentration, the rate of reaction will not increase, as every active site is already bonded to the substrate (catalysing the reaction).

c. The phenotype of an organism is influenced by both genotype and the environment. For example in humans, we inherit a height potential (as part of our genotype). However, whether or not we reach this potential depends on environmental factors. If nutrition is inadequete during the growth perion (childhood, adolesence), an individual will not reach their height potential. The lack of certain mineral will also decrease growth (ie if iodine is insufficient, growth will be stunted resulting in cretinism)

d. i) Virus

ii) Comparing it to bacteria - Viruses are acellular, while bacteria are unicellular eukaryotes; Viruses are smaller than bacteria; Viruses consist of a core of nucleic acid sourrounded by a protein coat, while bacteria have a single circular chromosome, cytoplasm, ribosomes, a cell wall and a cell membrane; Viruses are unable to survive outside of a host cell, while bacteria can; Viruses can be crystallised and bacteria cannot.

iii) When a virus enters the body, macrophages recognise antigens on their protein coat to be non-self, and respond by ingesting and digesting them (phagocytosis). These macrophages then display the viruses antigens on their surfaces. These are recognised by specific helper T cells, which stimulate the production of specific killer T cells, B cells and memory B and T cells. The killer T cells produce proteins that puncture holes in infected cells, killing them, while the B cells differentiate and mature to form plasma cells which produce antibodies specific to the antigens on the virus. These antibodies bind to the antigens, neutralising them. When the infection has been fought off, suppressor T cells halt the immune response, leaving teh memory B and T cells in the blood, so if the same virus enters the body again (displaying the same antigens) an immediate immune response can occur before symptoms develop.

e. i) I thought it was xylem???

ii) Water, dissolved mineral ions (ie phosphate, magenesium etc)

iii) Transpiration pull - As one molecule of water is lost by transpiration through the stomata on the leaves, a molecule of water moves from the xylem to the airspaces to take its place. As this happens, one molecule is drawn up the xylem to take its place due to cohesion. This causes transpiration pull in the xylem. Water also moves due to capillarity (water rising in narrow tubes due to adhesion and cohesion) and root pressure (the pressure of incoming water pushing water already in the xylem upward).

 

[dolbinau]

He isn't listed as an actual syllabus dot point, so I'd just say increased knowledge on the immune system especially the cloning of T/B cells as a response to specific antigens

Edit: Also do we need to know how cytptoxic t-cells kill infected cells? e.g releases perforin.

How much detail is needed on the effectiveness of vaccination programs for small pox, diptheria and polio??
__________________

1. I don't think so

2. Good question, I don't know. I'm personally going to have a few dates and generalise the success of small pox (eradication), less polio/diphtheria cases etc. Unless people have other suggestions. Maybe mention WHO in it somewhere

 

[Undermyskin]

a. DNA (deoxyribonucleic acid) is a polymer of nucleotides each of which is made up of 3 basic components: deoxyribose sugar, phosphate and nitrogen base. Elements: C, P, N, H and O. These nucleotides are classifed according to their bases in two groups: purine (A, G) and pyrimidine (T, C) and they go in pairs: A-T, C-G.

b. The amount of enzyme is fixed while the amount of substrate increases. These substrates occupy the active sites of the enzymes up to a point when none is spare. This is the saturation point. Any increase in substrates can increase the number of interaction between and the enzymes over a time unit. As in in the graph, the line flattens to a straight line.

c. Light on plants.
Those are exposed to sunlight as normal have darker green leaves, thicker and harder with their branches and trunks stronger and more turgid. This is due to the supply of photons to help them photosynthesis using chlorophylls and hence produce glucose, stored as starch in their body.
Those are kept in darkness have much paler leaves, soft and much longer. No light --> no photosynthesis, chlorophyll is unused, trees are consuming energy instead of producing.

d. i) Virus
ii) Bacteria: procaryotic cells, reproduce by mitosis, much bigger than virus, living organism (virus isn't unless it gets into a host cell), have organelles to carry out metabolism rather than just DNA; affected by antibiotics (when not resistant) while viruses aren't.

iii) Which one is 'the above'? Gosh.
Bacteria: they can be killed straight away by natural killer cells; or they enter the body until engulfed by macrophages, these phagocytes kill them (by lysozyme) and display their antigens on their surfaces, these antigen stimulate T-helper cells that then stimulate T and B cells. It takes time for T and B cells to produce proteins that can fit onto these antigens and that's when we have symptoms of the disease. Once finished, T cells clone and differentiate to T-killer cells (use cytotoxin to kill bacteria), T memory helper cells (remain in lymph nodes), T suppressor cells. B cells clone to plasma cells (produce antibodies that bind onto antigens to help 'signalling' + make them harmless) and B memory cells.

Virus: APCs (antigen presenting cells) digest them and use class II MHC to present the antigens to helper T cells. Similar procedure as above.

e) i) Xylem (?)
ii) water and minerals, upward only
iii) Transpirational pull: eveporation of water from the leaves through stomates initiate the force, pulling water upwards; due to cohesion force between water molecules and adhesion force between water molecules and the xylem sides, water is continuously pulled up.

Edit: For virus, cytotoxic T cells use perforin and granzyme to render apoptosis.

 

[imqt]

guys this may sound stupdi but is insecticide the same as pesticides?

 

[Undermyskin]

Well, pesticides include insecticides and herbicides.

 

[hoochiscrazy]

guys this may sound stupdi but is insecticide the same as pesticides?

At a guess maybe insecticides are more specific in that they just deal with insects and pesticides might deal with insects and plants diseases?? i dunno though.

 

[imqt]

Well, pesticides include insecticides and herbicides.

oh ok well im doin question 25 HSC PAPER 2005...and i wrote that the negative effects of pesticides is that it does not kill all pest, mutation occurs and leads to resistance/ reproduces etc....but in the HSC SUCCESS ONE answers it did not even mention this? i know they are dodgy answers, some of them, but thats an obvious answer? correct me if im wrong?

 

[Undermyskin]

How many marks for it? I haven't done it, sorry. But you're right, resistance is the key backlash they are looking for.

 

[imqt]

How many marks for it? I haven't done it, sorry. But you're right, resistance is the key backlash they are looking for.

its ok, its a 5 marker...they give you a scenario and you have to compare the impact of pesticides and biological control on the environment and society , in relation to controlling locusts

 

[dolbinau]

What does everyone have for their model of polypeptide synthesis? I only have a flow chart. Does that count?

 

[imqt]

What does everyone have for their model of polypeptide synthesis? I only have a flow chart. Does that count?

yeh i have a flow chart aswell

 

[dolbinau]

Also, a few more questions regarding polypeptides.

In DNA replication, corresponding nucleotides are brought from the nucleoplasm. Is this the same for the formation of mRNA?

Is the function of the ribosome to read the codons and call for a corresponding tRNA molecule?

 

[danz90]

so u guys liked my quiz? lolll

some really good answers there. especially midifile and undermyskin

and yes, it was xylem labelled in that diagram. It is the larger vessel towards the centre of the vascular bundle.