biology paper 1 doubts

[Nishii]

View attachment 18170 Why is the answer D ?
Are there really antigens on the surface of phagocytes ?
From the cambridge book it says that there are antibody receptors on white blood cells.I just dont get it !

there are self antigens on phagocytes!

 

[TCHS]

View attachment 18170 Why is the answer D ?
Are there really antigens on the surface of phagocytes ?
From the cambridge book it says that there are antibody receptors on white blood cells.I just dont get it !

Do you recall that process where specific antigens to a pathogen are arranged on the cell surface membrane of phagocytes?

 

[TCHS]

20 A peptide consists of ten amino acids of four different kinds.
What is the theoretical minimum number of different tRNA molecules required to translate the
mRNA for this peptide?
A 4
B 10
C 12
D 30

Help? I dont understand!

 

[athaan]

20 A peptide consists of ten amino acids of four different kinds.
What is the theoretical minimum number of different tRNA molecules required to translate the
mRNA for this peptide?
A 4
B 10
C 12
D 30

Help? I dont understand!

Answer is A.
tRNA can be reused, meaning that after the amino acid that it holds creates a peptide bond with another amino acid, the tRNA molecule leaves the amino acid and try to bond with the same type of amino acids lying in the cytoplasm.

There are four types of amino acids, therefore 4 types of tRNA can be used.

hope my answer helps.

 

[xtremeforums]

t

20 A peptide consists of ten amino acids of four different kinds.
What is the theoretical minimum number of different tRNA molecules required to translate the
mRNA for this peptide?
A 4
B 10
C 12
D 30

Help? I dont understand!

tRNA molecule is specific to one type of aminoacid. Since the polypeptide contains four different types of aminoacids, the minimum number of tRNA molecules needed would be 4. One for each type of amino acid.

 

[TCHS]

Answer is A.
tRNA can be reused, meaning that after the amino acid that it holds creates a peptide bond with another amino acid, the tRNA molecule leaves the amino acid and try to bond with the same type of amino acids lying in the cytoplasm.

There are four types of amino acids, therefore 4 types of tRNA can be used.

hope my answer helps.

Thank you! It did help

 

[TCHS]

t
tRNA molecule is specific to one type of aminoacid. Since the polypeptide contains four different types of aminoacids, the minimum number of tRNA molecules needed would be 4. One for each type of amino acid.

Thanks man!

 

[xtremeforums]

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_w08_qp_1.pdf

Question 36.
Why does increasing resistance to antibiotics and other drugs increase the spreading of malaria? Malaria is caused by a protoctista not a bacterium...
Please answer.

 

[InnocentAngel]

Do you recall that process where specific antigens to a pathogen are arranged on the cell surface membrane of phagocytes?

:O no i havent revsd it yet :/
What was it?

 

[InnocentAngel]

From one of the mcq i deduced that smoking increases the blood cholesterol level . How is that???

 

[NouranAyman]

Guys sometomes they adk us the diameter of organelles or cellsr in paper 1 how do we know it???

 

[ash369]

Ok so I know 1 is the dexoyribose sugar and 2 is the phosphate molecule, how do you decide although between 3 and 4?

 

[TCHS]

From one of the mcq i deduced that smoking increases the blood cholesterol level . How is that???

Because cigarette smoke contains nicotine, the nicotine causes atherosclerosis (which occurs when macrophages accumulate in arteries ) to occur where fats and cholesterol build up in arteries (causing plaques). This is why the blood cholesterol level increases.

 

[Ashiq Sookarry]

adenine forms 2 bonds with thymine and guanine 3 bonds with cytosine

 

[ash369]

adenine forms 2 bonds with thymine and guanine 3 bonds with cytosine

Oh alright! Thanks a lot bro!

 

[InnocentAngel]

Because cigarette smoke contains nicotine, the nicotine causes atherosclerosis (which occurs when macrophages accumulate in arteries ) to occur where fats and cholesterol build up in arteries (causing plaques). This is why the blood cholesterol level increases.

thanks buddy!

 

[InnocentAngel]

View attachment 18186
Can someone please explain this question to me?

Ans A . Is it A ?
I know potassium hydroxide absorbs CO2. I dnt knw if it wrks for NaOH as well

 

[railey]

Salam alaykum,
Can someone please help with this question.
I don't get this.. ;(
Thank you in advance

 

[InnocentAngel]

Why is the answer A ?? Where is the leaf turgid ? in diagrm1 or 2 ??

 

[ash369]

O

Ans A . Is it A ?
I know potassium hydroxide absorbs CO2. I dnt knw if it wrks for NaOH as well

The answer's B. The question's from the O level syllabus anyway!