ALL CIE BIOLOGY DOUBTS HERE !!!

[Sue T]

th only structure present in animal cells that is absent in plant cells is the centriole
th only structuress present in plant cells that r absent in animal cells are:
-chloroplasts (photosynthesising cells only)
-cell walls
-plasmodesmata
-tonoplast and a large central vacuole
wat u came across in wiki may be diff, wrong, or xtra details tht rnt of requirement in ths syllabus
or u may hav misunderstood
nyways ths info is from my cie textbook so its trustworthy

[Sue T]

my  doubt is:
in mj 04 ppr 4

Q 3(b) Explain three ways in which the cells of the proximal convoluted tubule are adapted for
selective reabsorption.
2 of th answers were:
tight junctions – prevent migration of membrane proteins / separate
tubule fluid ;
ref. to pincocytosis – protein uptake ;
i have no idea wat they're talkin bout n its not in my textbook so - ny1 has ny idea?

Q 5 Coat colour in cats is determined by a sex-linked gene with two alleles, black and orange.
When black cats are mated with orange cats, the female offspring are always tortoiseshell,
their coats show black and orange patches of various sizes, while the male offspring have
the same coat colour as their mothers.
(c) Suggest an explanation for the tortoiseshell coat in terms of the activity of the X
chromosomes.
th ans was:
X chromosome inactivated randomly early in development
wat does that mean?

[Amelia]

my  doubt is:
in mj 04 ppr 4

Q 3(b) Explain three ways in which the cells of the proximal convoluted tubule are adapted for
selective reabsorption.
2 of th answers were:
tight junctions – prevent migration of membrane proteins / separate
tubule fluid ;
ref. to pincocytosis – protein uptake ;
i have no idea wat they're talkin bout n its not in my textbook so - ny1 has ny idea?
 

for pt. 1 - tight junctions are an adaptation of the proximal convulated tubules. They (the junctions) prevent the passage of molecules and ions through the space between cells. So materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue. This pathway provides control over what substances are allowed through.


2- you are supposed to refer to the pinocytosis process that takes place,
 Small proteins which pass into the tubule during ultrafiltration are removed by pinocytosis at the base of the microvilli. They are enclosed in pinocytotic vesicles to which lysosomes are attached. Hydrolytic enzymes in the lysosomes digest the proteins to aminoacids which are either used by the tubule cells or passed on, by diffusion, to the blood capillaries.

Although,
The proximal convoluted tubule cells are adapted for reabsorption as folloes:
i) large surfacearea due to microvilli and basal channels;
ii) numerous mitochondria;
iii) Closeness of blood capillaries.

[Amelia]

my  doubt is:
in mj 04 ppr 4

Q 5 Coat colour in cats is determined by a sex-linked gene with two alleles, black and orange.
When black cats are mated with orange cats, the female offspring are always tortoiseshell,
their coats show black and orange patches of various sizes, while the male offspring have
the same coat colour as their mothers.
(c) Suggest an explanation for the tortoiseshell coat in terms of the activity of the X
chromosomes.
th ans was:
X chromosome inactivated randomly early in developmentwat does that mean?

Each cell in a female's body contains two X chromosomes, but one is 'inactive' or 'turned-off' through a normal process called X-inactivation.Because X-inactivation is random, in normal females the X chromosome inherited from the mother is active in some cells, and the X chromosome inherited from the father is active in other cells.

[**RoRo**]

Question, how do you prepare for a biology practical exam? [Paper 3]

[Sue T]

Each cell in a female's body contains two X chromosomes, but one is 'inactive' or 'turned-off' through a normal process called X-inactivation.Because X-inactivation is random, in normal females the X chromosome inherited from the mother is active in some cells, and the X chromosome inherited from the father is active in other cells.

thank u v much both xplanations wer very helpful

[Master_Key]

Question, how do you prepare for a biology practical exam? [Paper 3]

You performed the practicals once in the classes right?

[**RoRo**]

You performed the practicals once in the classes right?

Yup! But I'm asking what do I do before going for my test, at home, like the day before.

[Amelia]

Yup! But I'm asking what do I do before going for my test, at home, like the day before.

   Practice drawing cells-very thin cell walls if it's a plant cell and the more variety of cell structures you draw the better prepared you  will be to draw any organelles that you may see on the day which you may recognize from practice.
And also you will be much more likely to label correctly.

- And revise food tests, make sure you know the procedure well and the results of the experiments well.

- Practise Graphs

- Go through your lab manual

[Amelia]

thank u v much both xplanations wer very helpful

My pleasure, Sue.
And sorry for the late reply.

[**RoRo**]

   Practice drawing cells-very thin cell walls if it's a plant cell and the more variety of cell structures you draw the better prepared you  will be to draw any organelles that you may see on the day which you may recognize from practice.
And also you will be much more likely to label correctly.

- And revise food tests, make sure you know the procedure well and the results of the experiments well.

- Practise Graphs

- Go through your lab manual

Thank you!

What's a lab manual? :/

[Amelia]

Thank you!

What's a lab manual? :/

It's that book you use in the lab.

[**RoRo**]

It's that book you use in the lab.

LOL Okay!

Thanks!

[Vampire-Love4ever]

4 Fig. 4.1 is a diagram drawn from a photomicrograph of an animal cell undergoing meiosis.


(a) Identify the stage of meiosis shown in Fig. 4.1.

...[2]

figure attached

th answer is : metaphase 2
from which angle does this look like metaphase 2??




ps- i cant attach the image !

[Amelia]

4 Fig. 4.1 is a diagram drawn from a photomicrograph of an animal cell undergoing meiosis.


(a) Identify the stage of meiosis shown in Fig. 4.1.

...[2]

figure attached

th answer is : metaphase 2
from which angle does this look like metaphase 2??
ps- i cant attach the image !

try uploading figure 4.1 again, because all I see is a cross where the pictromicrograph should be.
Meiosis 1 - http://botit.botany.wisc.edu/images/130/Meiosis/Lilium_microsporogenesis/Meiosis_1.jpg
Meiosis 2 - http://faculty.irsc.edu/FACULTY/TFischer/images/meiosis%202.jpg
http://botit.botany.wisc.edu/images/130/Meiosis/Lilium_microsporogenesis/Metaphase_II_MC_.low.jpg