Edexcel AS Biology - 6B101 + 6B102 - Unit 1 and Unit 2 Exam Discussion Thread

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Reply 1980

metaphase - the chromosomes line up at the equator the chromosomes attach to the spindle fibre the fibres attach to the centromere
anaphase - the spindle fibre contracts the fibres pull the chromatids apart
telophase - the chromosomes become visible the nuclear envelope reforms the nucleolus reappears.

I thought telophase they become invisible

Reply 1981

TheGreatImposter

Original post by unfathomableuser

I thought telophase they become invisible

They do. Chillax.

Let's smash this exam :smile:

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Reply 1982

Leah97

Original post by Excuse Me!

Can someone please summarise the stuff on a and b glucose, cellulose, microfibrils etc

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starch is made up alpha glucose while cellulose is made up of beta glucose starch contains 1,4/1,6 glycosidic bonds while cellulose contains 1,4 glycosidic bonds they are both insoluble.
cellulose microfibrils are formed when hydrogen bonds form between cellulose chains they are unbranched chains and basically the same structure as cellulose.
someone correct me if i made any errors. :smile:

Reply 1983

tayloryeah

Original post by Simmmi02

Can someone briefly remind me of what happens at each stage of the cell cycle? Kinda forgotten everything apart form prophase :redface:

Interphase consists of #g1 (where replication of organelles takes place), s phase (where DNS replication occurs), #g2 (replication of centrioles in preperation for mitosis)
Prophase:
-nuclear membrane breaks down
-chromosomes condense and are seen as sister chromosomes attached to a centromere
-centrioles begin to move to opposite poles
-spindles begins to form
Metaphase:
-centrioles have reached oposite poles
-spindles attatch to centromere and aligns chromosomes along the equator
Anaphase :
-spindles contract, breaking the centromere apart
-chromosomes are dragged to oposite post poles as spindles shorten
Telophase:
-nuclear membrane reforms
-chromosomes decondse
-spindles dissapear
-cyroplasm splits as two diploid nuclei are present
-one centeriole in each cell

Reply 1984

Leah97

Original post by unfathomableuser

I thought telophase they become invisible

yeah they do sorry my mistake :colondollar:

Reply 1985

Rubberduckiller

someone explain role of seedbanks and how they work please...

Reply 1986

Rubberduckiller

six mark question on how an egg cell is adapted how would you answer this...

Reply 1987

kdizzle97

Best of luck everyone, its been great having all of your help for both Biology Exams! Lets smash it :biggrin:

Reply 1988

tayloryeah

Original post by Rubberduckiller

someone explain role of seedbanks and how they work please...

How seed banks conserve seeds:
- collect seeds from different plants of the same species from different locations
-increases the genetic diversity

Seeds are collected from different plants because it increases genetic diversity and therefore increases the chance of a benificial allele, increasing the chance of survival due to adaptability. It also decreased the chance of interbreeding

Seed banks conservation :
-seeds are cleansed
-dried and stored at low temperatures to reduce enzyme and bacteria activity and reduce the rate of decomposition and germination
-seeds at tested to see if they consist of a living embryo using X-rays
-only viable seeds are stored
-viability is regulary checked during storage because germination success produces a new seed and some may need replacement due to decay
-if less than 75% germinate, collect fresh seeds for storing

Reply 1989

FutureMedic97

Original post by Rubberduckiller

six mark question on how an egg cell is adapted how would you answer this...

It's haploid so that diploid can be restored upon fertilisation
It contains lipid droplets as a store of energy for the mitosis after fertilisation
It is large to increase its chance of fertilisation
It has a zona pellucida to prevent poly spermy

Hope that helps!

Reply 1990

tayloryeah

Original post by Rubberduckiller

six mark question on how an egg cell is adapted how would you answer this...

Lipid droplets - provide energy for division
Egg cell releases chemicals - to attract sperm
Haploid cell - restored at fertilisation
Large surface area- increases the chance of fertilisation
Sperm membrane receptors - for sperm to bind onto
Zone pellucida hardens - to prevent polyspermy

Reply 1991

Tazmain

Role of synergids and antipodal cells?

anyone?? :s-smilie:

Reply 1992

Vinny22

Any predictions on what the questions will be?

Reply 1993

flight1

Do we need to know about the lac operon etc

Reply 1994

NUFC_97

Original post by jem_12345

please can someone tell me what label U is? thanks :smile:

Can someone explain what Q is?

Reply 1995

xsashax

Original post by NUFC_97

Can someone explain what Q is?

sclerenchyma

Reply 1996

NUFC_97

Original post by xsashax

sclerenchyma

Then what is S, I thought this is sclerenchyma, or are they both?

Reply 1997

xsashax

Original post by NUFC_97

Then what is S, I thought this is sclerenchyma, or are they both?

it's a bit confusing cause I'd say it's parenchyma though tha's meant to be a bit more in the middle...

Reply 1998

Nicobella12

Was such a good paper!!!!! But did get a little stuck on the last question

Reply 1999

Tazmain

Original post by Nicobella12

Was such a good paper!!!!! But did get a little stuck on the last question

Yeah, last one was a tough,

Loads of suggest questions as well, which were somewhat tricky to answer

I crossed out plasmodesmata and marked tonoplast :angry: