AS BIOLOGY PAPER 1 2023 Flashcards
(27 cards)
Describe the primary structure of all proteins.
they have a specific amino acid sequence
proteins are formed/joined by peptide bonds
This question is about the genetic code.
Define universal, non-overlapping and degenerate.
universal
the same triplet codes always for the same amino acid
non-overlapping
each base is only part of one codon
degenerate
more than one codon codes for the each amino acid
Describe how the appearance of the area containing DNA in a TEM image of a
eukaryotic cell would differ from that shown in Figure 1
you would be able to see the nucleus and dna being attached to histones
Describe one difference between the structure of DNA in a prokaryotic cell and in a
eukaryotic cell.
prokaryotic
DNA is circular
eukaryotic linear
Streptococcus bacteria can infect the lungs when air is breathed in and cause lung
disease.
Describe the mechanism of breathing that causes air to enter the lungs
diaphgram contracts
external intercostal muscles contract pulling ribcage to move out and up
volume increases and pressure in thoractic cavity decreases
air pressure moves down a pressure gradient and its an active process requiring energy
Some strains of Streptococcus bacteria are more likely to cause lung disease than
other strains.
Strains that do not cause lung disease are quickly destroyed by phagocytes.
Phagocytes are stimulated when they bind to murein on Streptococcus bacteria.
Each strain of Streptococcus bacteria has a capsule of different thickness from the
others.
Suggest how Streptococcus bacteria with a thicker capsule are more likely to survive
and so cause lung disease.
phagocytes are unable to bind to cell wall murein
so less phagocytes carry out phagocytosis
bacteria can divide and produce toxins and do binary fission
Explain why phospholipids can form a bilayer but triglycerides cannot.
- Phospholipid both hydrophobic and hydrophilic
- phosphate group is charged so it can attract to hydrophillic head attracting water
- triglycerides are hydrophobic
Suggest why the fluidity of the membrane was higher after 4 months.
Use all the information provided in the question.
fatty acid B is unsaturated
Increase in fluidity caused by increased unsaturated fatty acids
Double bonds/unsaturated fatty acids cause
bends/kinks in fatty acid tail
State one feature that shows the images in Figure 5 were taken with an electron
microscope and not an optical microscope.
Explain your answer.
you can see the lysosomes and the nuclear membrane
EM has a higher resolution
State one role of a helper T cell.
stimulates B cells
The rate of translation is increased in T cells activated by antigens.
Describe the role of tRNA in translation.
tRNA brings specific amino acid to ribosome
anticodon on tRNA complementary/binds to codon on mRNA
Suggest what the student should have done when she saw that shape C, block 2 was
damaged.
Repeat with an undamaged (shape C) block;
State three variables the student controlled in order to obtain valid results
temperature
pH of solution
concentration of indicator
Describe how gas exchange occurs in single-celled organisms and explain why this
method cannot be used by large, multicellular organisms.
single celled
they have a high surface area to volume ratio
diffusion pathway is longer so rate is slower
multicelluar
they have a small surface area to volume ratio
diffusion is faster
The DNA-replication enzymes of a human cell make copies of the human papilloma
virus genome.
Name two enzymes that are involved in replicating the DNA of the human papilloma
virus and describe their roles in the replication process.
DNA helicase breaks hydrogen bonds between complementary base pairs
DNA polymerase joins adjacent nucleotides together via condensation reaction
catalyses the formation of phosphodiester bonds
Human papilloma virus infects cells that are no longer dividing. The human papilloma
virus genome contains genes that code for proteins that cause human cells to restart
their cell cycles.
Human papilloma virus infection can cause cancer.
Explain why.
uncontrollable cell division
Human papilloma virus (HPV) is transmitted through sexual contact.
More than 95% of cervical cancers (which only affect females) are due to HPV
infection. HPV infection of other tissues increases the risk of cancer but this is rare
compared with cervical infection.
A vaccine is available that is over 80% effective at preventing HPV infection, if given
before the person has been exposed to HPV. There is evidence of herd immunity
when more than 50% of the population have been vaccinated.
Evaluate whether 10- to 12-year-old boys should be given the HPV vaccine.
FOR
herd immunity which is good because the majority will be vaccinated so it will unlikely spread to the unvaccinated
will reduce the spread to boys
AGAINST
boys do not have a cervix so they dont get cervicial cancer
Using the standard deviation data from Table 4, describe the differences in
prokaryotic biodiversity found in the soil with these two farming methods.
In your answer, give the definitions of species richness and index of diversity
species richness is the number of species in a community
index of diversity is the relationship between the number of species and number of individuals
Genetic diversity in soil species was traditionally inferred by making observations after
growing prokaryotes on agar plates.
However, it is estimated that less than 10% of prokaryotes found in soil will grow if
spread on an agar plate in a laboratory.
In recent years, our knowledge of prokaryotic biodiversity in the soil has increased.
Suggest why.
DNA genome sequence can be now used
now we can analyse more prokaryotic species
Evaluate the balance between conservation and farming for these two farming
methods.
Use the information provided in Table 4 (on page 16).
FOR
there is a greater species richness
good at locking up carbon which reduces greenhouse effect
AGAINST
Decreases yield for food
A student prepared a plant root to observe cells undergoing mitosis.
He put the root in a small bottle of hydrochloric acid in a 40 °C water bath.
Why did he put the plant root in acid?
to squash the cell and break down the cell wall to allow stain to diffuse in
State the null hypothesis for this investigation.
Name the statistical test needed to determine whether the difference between the
mean mitotic index at 200 μm and at 300 μm is significant.
there is no significant difference between the mitotic index at 200 and 300
t-test
The scientists recorded these measurements from the tissue located at 200 μm from
the root tip.
Area of field of view = 0.2 mm2
Mean area of one cell = 3495 μm2
Use this information and Figure 7 to calculate the number of cells undergoing mitosis
in this location.
Assume there are no spaces between the cells.
Show your working.
20
Another student compares the mitotic index in the roots of two different species.
Give two considerations within her method to ensure this comparison is valid.
same age of root
same time of day
