2017 paper 1 a level Flashcards
(23 cards)
Give the 2 types of molecule from which a ribosome is made
2 marks
A Protein and RNA
Describe the role of a ribosome in the production of a polypeptide
Dont include transcription in your answer
3 marks
- mRNA binds to ribosome;
- Idea of two codons/binding sites;
- (Allows) tRNA with anticodons to bind/associate;
- (Catalyses) formation of peptide bond between
amino acids (held by tRNA molecules); - Moves along (mRNA to the next
codon)/translocation described;
Base sequence of pre-mrna may be different to the base sequence of mrna explain why 2 marks
Introns are removed during splicing of pre mrna
Describe the structure of glycogen 2 marks
Polysaccharide of alpha glucose/ polymer of alpha glucose
Joined by glysosidic bonds/ branched
Suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients. 2marks
Membrane folded in order to provide a large surface area
or membrane has a large surface area for the rapid diffusion of molecules
Large number of protein channels for co-transport
Large number of protein carriers in membrane for active transport
High absorption of salt from the diet can result in a higher than normal
concentration of salt in the blood plasma entering capillaries. This can lead to a
build-up of tissue fluid.
Explain how. 2 marks
Higher salt results in lower water potential of
tissue fluid so less water returns to capillary by osmosis (at venule end);
OR
Higher salt results in higher blood pressure/volume
So more fluid pushed/forced out at arteriole end of capillary
Describe how bacteria divide.
2 marks
Binary fission
Circular dna replicates
Division of cytoplasm to produce 2 genetically identical daughter cells
Each with a singular copy of circular DNA
Explain the shape of the curve at 50 and 60 degrees 4 marks
Both denatured (by high temperature
Denaturation faster at 60 °C due to more kinetic energy;
Breaks hydrogen/ionic bonds (between amino acids/R groups);
Change in shape of the active site/active site no longer complementary so fewer enzyme substrate complexes formed
Suggest one advantage to a bacterium of secreting an extracellular protease in its
natural environment.
Explain your answer. 2 marks
To digest proteins and break them down
So amino acids can be re absorbed for protein synthesis of the bacteria
Describe the action of these membrane-bound dipeptidases and explain their
importance. 2 marks
Hydrolyse peptide bonds to release amino acids
Amino acids can cross cell membranes
Place a tick () in the appropriate box next to the equation which represents the
reaction catalysed by ATP synthase.
[1 mark]
ATP= ADP + Pi + H2O
ATP + H2O =ADP + Pi
ADP + Pi= ATP + H2O
ADP + Pi + H2O =ATP
ADP+ Pi = ATP + H2O
Synthesising ATP
Suggest why human ATP synthase is not inhibited and bacterial synthase is
inhibited. 1 mark
Human ATP synthase has a different tertiary
structure to bacterial ATP synthase
Give three environmental variables that should be controlled when growing the
plants before treatment with the different sprays. 2 marks
- Temprature
-CO2 concentration - Conc of minerals in the soil used to grow the plants
- Humidity
- Soil PH
-Light intensity
-Volume of water given to the plants
Any 3
Evaluate the use of 2,4-D as a herbicide on a wheat crop that contains wild oats as
a weed. Use all the information provided. 4 marks
2,4-D causes an increase in release of ions
from wild oat cells and 2,4-D does not affect the release of ions from wheat cells;
For wheat Difference is less than LSD/7 so difference is not significant
3. Loss of ions from cells (likely to) lead to cell/plant death/damage
No evidence here about the death of plants as a result of this ion loss
No evidence here of other
ecological/environmental impact;
Describe how phagocytosis of a virus leads to presentation of its antigens 2 marks
Phagosome/vesicle fuses with lysosome;
(Virus) destroyed by lysozymes/hydrolytic
enzymes;
Peptides/antigen (from virus) are displayed on
the cell membrane;
Describe how presentation of a virus antigen leads to the secretion of an antibody
against this virus antigen. 3 marks
Helper T cell/TH cell binds to the antigen on
the antigen-presenting cell/phagocyte);
This helper T/TH cell stimulates a specific B cell
B cell divides by mitosis;
Forms plasma cells that release antibodies;
Collagen is a protein produced by cells in joints, such as the knee.
Rheumatoid arthritis (RA) is an auto-immune disease. In an auto-immune disease,
a person’s immune system attacks their own cells. RA causes pain, swelling and
stiffness in the joints.
Scientists have found a virus that produces a protein very similar to human
collagen.
Suggest how the immune response to this viral protein can result in the
development of RA. 2 marks
The antibody against virus (antigen) will bind
to collagen;
This results in the destruction of the (human)
cells/collagen;
State three comparisons of genetic diversity that the scientists used in order to
generate Classification Y.
Classification y was developed based of genetic analysis
Base sequence of dna
Base sequence of mrna
The amino acid sequence of proteins
Explain 3 ways in which the insects tracheal system is developed for efficient gas exchange 3 marks
vvTracheae provide tubes full of air so fast
diffusion (into insect tissues);
5. Fluid in the end of the tracheoles that
moves out (into tissues) during exercise so faster diffusion through the air to the
gas exchange surface;
Any 3
The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain
oxygen from water.
Some other species of insect have larvae that are a similar size and shape to
damselfly larvae and also live in water. These larvae do not actively hunt prey and
do not have gills.
Explain how the presence of gills adapts the damselfly to its way of life. 2 marks
. Damselfly larvae has high(er)
metabolic/respiratory (rate);
2. (So) uses more oxygen (per unit time/per
unit mass);
Suggest two ways the student could improve the quality of her scientific drawing of this gill.
2 marks
Don’t use shading;
Only use single lines/don’t use sketching lines and ensure lines are connected
Add further labels or annotations
Don’t cross label lines;
Add magnification/scale bar
Contrast how an optical microscope and a transmission electron microscope work
and contrast the limitations of their use when studying cells.
6 marks
TEM use electrons and optical use light;
TEM allows a greater resolution;
So with TEM) smaller organelles/named cell
structure can be observed greater detail in organelles/named cell structure
can be observed
TEM view only dead/dehydrated specimens and optical can view live specimens
TEM does not show colour and optical can
TEM requires thinner specimens;
TEM requires a more complex/time consuming
preparation
TEM focuses using magnets and optical uses
(glass) lenses
