Edexcel WBI02 ON 02/06/2014 (Biology Unit 2) IAL THREAD! NOT GCE

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angelom1994

not exactly, circular DNA could also refer to the nucleoid as well!

I'm so confused because my notes state that chloroplasts and mitochondria have circular DNA but also that only prokaryotes have plasmids. So if they're the same then whats going on

Reply 81

Lassy96

Original post by angelom1994

I'm so confused because my notes state that chloroplasts and mitochondria have circular DNA but also that only prokaryotes have plasmids. So if they're the same then whats going on

Chloroplasts and mitichondria are cell structures,they have no DNA ,circular or linear.Just stick with circular DNA if plasmids confused you.

Reply 82

Lassy96

Any tips for the practical questions? Gosh i hate them soo much.

Reply 83

angelom1994

Original post by Lassy96

Chloroplasts and mitichondria are cell structures,they have no DNA ,circular or linear.Just stick with circular DNA if plasmids confused you.

We just ignore the organelles and focus on the actual cells ok got it! Mitochondria do have dna though (mDNA) , i just dont think we acknowledge it in the syllabus

Reply 84

Ripper Phoenix

Original post by angelom1994

I'm so confused because my notes state that chloroplasts and mitochondria have circular DNA but also that only prokaryotes have plasmids. So if they're the same then whats going on

nonononono it has been discovered that mitochondria and cholorplasts orginate from the same cell known as a LEUCOPLAST .. thats why they seem similar..

and circular DNA is not plasmids i repeat circular dna is not plasmid..

CIRCULAR DNA REFERS TO THE NUCLEOID

Reply 85

Farafeero

Guys, what's the difference between xylem and sclerenchyma?

Reply 86

Ripper Phoenix

Original post by Farafeero

Guys, what's the difference between xylem and sclerenchyma?

Xylem can transport water and mineral ions and also is for support

HOWEVER!

Sclerenchyma has only 1 function and that is for support and NOT transport :smile:

Reply 87

Farafeero

Original post by Paras Agarwal

Xylem can transport water and mineral ions and also is for support

HOWEVER!

Sclerenchyma has only 1 function and that is for support and NOT transport :smile:

Thank yoooouu! :smile:

Reply 88

Ripper Phoenix

Original post by Lassy96

Any tips for the practical questions? Gosh i hate them soo much.

well i highly doubt there can be tips.. lol but just know your practicals well! stuff like why do we use the same plant fibres? why do we incubate petri dishes at 25 degrees... why do we use a named stain and acid (in mitosis)?

also know all experimnents well who knows they may want us to describe an xperiment as well for like 5 marks..surely cant lose out there :biggrin:

gud luck

Reply 89

Wannabe007

Original post by Wannabe007

Hey guys,
Could anyone explain figure 3.2.15 in the Edexcel Biology Book ( pg. 169, HSW box) ? I mean, does the age of the recipient embryo matter or the donor embryo's ?
Thanks.
Btw, If I've stupidly replied to someone, Im sorry its a mistake. I just made an account. =)

Could anyone please help me out in this ? Im in real confusion.

Reply 90

angelom1994

Original post by Paras Agarwal

ok so lets recap which cells/strucutres have circular dna which have plasmids and which have a nucleus with histones and dna

Reply 91

Farafeero

1- Take seedlings of the same parent plant and grow them to get genetically identical plants of the same age and size.
2- Place plants in equal amounts of nitrate ion solution, made by adding 200 cm3 of water to 50 ppm of nitrate ions, keeping all other minerals constant.
3- Allow the plants to grow at 25 degree Celsius at room temperature near a light source of a 250 W light bulb for 4 weeks. Keep on adding distilled water when required.
4- Measure the growth of the plant by counting the number of leaves formed. Repeat the same experiment with different concentrations of nitrates, 100, 150, 200 and 250 ppm.
5- Compare the number of leaves for each concentration. Repeat the whole experiment to get more reliable and valid results. Record the data and plot the graph.

Okay fine, this is how we compare the effects of different concentrations of nitrate ions. My question is, how do we compare the effects of different minerals?

Reply 92

trialbyc0mbat

can some briefly explain the stages of the cell cycle?

Reply 93

fictioned

You guys should revise Mitosis as well. The experiment has a high chance of coming up, so it wouldnt hurt

Posted from TSR Mobile

Reply 94

Ripper Phoenix

Original post by fictioned

You guys should revise Mitosis as well. The experiment has a high chance of coming up, so it wouldnt hurt

Posted from TSR Mobile

done with that :wink:

Reply 95

fictioned

Hahah, I am going through topic 4 now.
At least the exam is in the afternoon.

Any other topics you arr confident about?

Posted from TSR Mobile

Reply 96

angelom1994

Original post by trialbyc0mbat

can some briefly explain the stages of the cell cycle?

The cell cycle consists of the following stages: G1 - S - G2 - Mitosis- Cytokinesis. G1-S-G2 is also known as interphase and it's the stage before mitosis occurs. During G1 growth occurs, During S , DNA replication and during G2 preparation for mitosis. Then we have Mitosis , remember the anagram PMAT. Prophase, Metaphase, Anaphase and Telophase. After that comes cytokinesis when the cell splits.

The general function of the cell cycle is :
1) controlling the growth of an organism, replacing dead cells , repairing damaged tissue
2) increasing number of cells
3) asexual reproduction
4) DNA replication

Cell-Cycle-Illustration-Only.png7.2KB

Reply 97

Ripper Phoenix

Original post by trialbyc0mbat

can some briefly explain the stages of the cell cycle?

aim of cell cycle: growth and asexual reproduction
now stages:

1) INTERPHASE- newly formed cell grows, cell undertakes its normal function, cell prepares to divide by replicating its chrromosomes, chromosomes continue to condense, some organelles increase in number

2) MITOSIS: broken down into 4 stages namely Prophase, Metaphase, Anaphase, Telophase
a) Prophase:
nucleolus disappears
nuclear envelope breaks down
centrioles move to opposite poles of a cell
spindle fibres form
chromosomes condense and become fully visible

b) Metaphase:
chromosomes line up at cell equator
chromosomes attach to spindle fibres
fibres attach at the centromere

c) Anaphase
spindle fibres contract
fibres pulled to opposite poles with centromere leading

d) Telophase
chromosomes decondense and become invisible
nucleolus reappears
nuclear envelope reforms

Lastly CYTOKINESES:
organelles become arranged at opposite poles of a cell
cytoplasm divides
cell divides to form 2 daughter cells

NB: Its too bad i know these things word for word as they are in the revision guide lol.. i just love bio

Reply 98

koko1234

What is the structure of schlerenchyma?

Reply 99

trialbyc0mbat

wow thanks for the answer you both, that is what i needed! (Y)
now im having difficulty in understanding this translation and trascription and mRNA and all that. in january 2014 they asked a question to describe the processes which cause a cell to become specialized. in the marks scheme there is something about translation, transcription and mRNA. should not there be something about the transcription factors as well? like if they are present then the gene is switched on and it becomes specialized? :s-smilie: