Biology questions I got wrong Flashcards
Which anion is a component of nucleotides and phospholipids?
- PO43-
Give one reason why water is useful as a solvent in living organisms
- most biological reactions take place in solution
- dissolved substances can be transported around the body
Give one reason why it is important for ice to form an insulating layer at the surface of ponds and lakes
- so that the water below the layer does not freeze
so that organisms below the layer can move and survive
Name the type of chemical bond that causes water molecules to stick to other materials (adhesion)
- hydrogen
Give 3 examples of how carbohydrates are used in the body.
- to supply energy to cells
to store energy
to make structural components
to help in cellular recognition
to build biological molecules
Give two ways in which the structure of cellulose helps to give it strength.
- Remember microfibrils
- Unbranched
True or False? All monosaccharides are reducing sugars.
- True
- All monosaccharides and some disaccharides are reducing sugars.
Which chemical must be added to a non-reducing sugar to hydrolyse the disaccharides?
- hydrocholric acid
Suggest one reason why scientists doubted for a long time that DNA is the source of genetic information for all organisms.
- DNA structure is too simple
Describe how Mrna is produced and prepared for translation.
First, hydrogen bonds in the DNA strands are broken. (1)
Next, free RNA nucleotides bind to complementary DNA bases. (1)
These RNA nucleotides contain uracil instead of thymine. (1)
Then, for the last two marks, describe the role of RNA polymerase in producing mRNA:
Finally, RNA polymerase joins adjacent RNA nucleotides (1)
through phosphodiester bonds. (1)
Describe how translation leads to the production of a polypeptide. [5 marks]
First, mRNA binds to a ribosome. Next, a tRNA molecule that carries a specific amino acid moves to the ribosome, and its specific anticodon binds to the complementary codon on the mRNA. The ribosome then moves along to the next codon. The amino acids are joined together by condensation reactions, forming a polypeptide.
Describe the roles of the following in translation:
i) A ribosome [2 marks]
ii)
A tRNA molecule [2 marks]
Part i) - Up to 2 marks for:
. 1. Assemble amino acids into specific proteins
· 2. (by) facilitating tRNA binding.
Part ii) - Up to 2 marks for:
. 1. Contains anticodon
. 2. (which is) specific to the codon on the mRNA strand.
A polypeptide contains 42 amino acids.
i) Calculate the minimum number of bases needed to form the polypeptide. [1 mark]
During translation, 15 amino acids are added to the polypeptide each second.
ii) Calculate how many bases will be added over the course of 1 minute. [1 mark]
- Part i) - Up to 1 mark for:
. 42 × 3 = 126
To calculate the minimum number of bases needed to form the polypeptide, recall how many bases code for
one amino acid:
1 amino acid:
- coded for by 3 bases
You’re told that this polypeptide contains 42 amino acids.
So, to score one mark, calculate the minimum number of bases needed to code for 42 amino acids:
42×3=126 bases (1)
- Part ii) - Up to 1 mark for:
. 15× 3× 60 = 2700
To calculate how many bases are added to the polypeptide in one minute, recall how many bases code for one
amino acid:
1 amino acid:
- coded for by 3 bases
You’re told that 15 amino acids are added to the polypeptide each second.
So, calculate how many bases are added to the polypeptide each second:
15 ×3=45 bases
Next, there are 60 seconds in 1 minute.
So, to score one mark, calculate how many bases will be added to the polypeptide in 1 minute:
45×60=2700 bases (1)
Explain why donated human organs are placed in an isotonic solution during transport. [3 marks]
. 1. No net movement of water in or out of cells by osmosis;
. 2. (So) cells don’t gain water and lyse / burst;
. 3. (So) cells don’t lose water and shrink / shrivel / become crenated.