AS BIOLOGY 2022 PAPER 1 Flashcards
(28 cards)
Describe the mechanism for the absorption of amino acids in the ileum.
Sodium ions are actively transported from the epithelial cells to the blood
Sodium ion concentration decreases in epithelial cell
Sodium ions diffuse through the lumen down a concentration gradient into the epithelial cell via a cotransporter protein
the co transporter protein brings amino acids where sodium ions are increasing amino acid concentration by faciliated diffusion
faciliated diffusion of amino acids into blood
Give the two types of molecule from which a ribosome is made.
RNA
protein
four structural differences between a DNA molecule and an
mRNA molecule.
DNA is double stranded RNA is single stranded
DNA has hydrogen bonds RNA doesnt
DNA has deoxyribose sugar RNA has ribose sugar
DNA has thymine RNA has uracil instead of thymine
Figure 2 is different from an image of this bacterium obtained using a transmission
electron microscope.
Describe and explain one difference between these images.
3D with SEM, but 2D with TEM
because electrons bounce of using SEM
The resolution of an image obtained using an electron microscope is higher than the
resolution of an image obtained using an optical microscope.
explain why
Longer wavelength in light (rays
A student determined the size of a cell structure from a photograph obtained using a
microscope.
He used a ruler and a calculator and gave the answer in μm
Describe how the student determined the size of the structure.
Measure (length of structure) and divide by
magnification;
convert from mm to micro metres by multiplying by a 1000
Name two structures found in all bacteria that are not found in plant cells.
chloroplast
cell wall
Name two features of HIV particles that are not found in bacteria
caspid
reverse transcriptase
The pO2 of dissolved oxygen in lugworm blood is < 2.7 kPa
Using the data in Figure 3, what can you conclude about the uptake of oxygen over
the entire body of the lugworm?
- Enters by diffusion;
- Down a concentration gradient
OR
From high to low pO2; - More/most across parts of body with gills;
- Gills provide a larger surface area (for
absorption); - 8.8 (kPa) over gills
The oxygen saturation in the blood of a lugworm is 92%
The lugworm has 0.2 cm3 of blood.
Calculate the volume of dissolved oxygen in the blood of this lugworm using this
equation
pO2 = CdO2
0.000 031
CdO2 is the concentration of dissolved oxygen in the blood, with units
cm3 oxygen per cm3 of blood
9.3 x 10 power of -6
The intensity of the red colour in blood is affected by the pO2 of the blood.
The intensity of the colour in a solution is measured using a colorimeter.
The scientist used a colorimeter to measure the intensity of red colour in samples of
lugworm blood with different pO2 values. She prepared a calibration curve with this
information.
Describe how the scientist will use information from the colorimeter and her calibration
curve to determine the pO2 in a sample of lugworm blood.
- (Measure light) absorption/transmission;
- Interpolate/draw line to curve/line then to pO2
Describe how monomers join to form the primary structure of a protein.
condensation reaction between amino acids
many amino acids join together to form a peptide bond which determine the specfic sequence of amino acids determining the primary structure
Describe one similarity and one difference between the induced-fit model of enzyme
action and the lock and key model of enzyme action.
SIMILARITY
Substrate binds to active site
DIFFERENCE
active site changes shape so its complementary to substrate
State how enzymes help reactions to proceed quickly at lower temperatures.
Do not write about active sites in your answer.
Lower down activation energy
Explain a property of iron ions that enables these ions to carry out their role in red
blood cells.
are positively charged which allows them to bind to o2 and allows the formation of oxyhaemoglobin
The hormone hepcidin controls the iron ion concentration in blood plasma. Hepcidin
affects ferroportin, the iron ion channel protein in cell-surface membranes.
Figure 7 shows how hepcidin controls the iron ion concentration in plasma.
People with the disease haemochromatosis do not produce hepcidin.
Use information in Figure 7 to explain why the iron ion concentration is higher in the
plasma of people with haemochromatosis.
Hepcidin is not present
so the protein channel ferroportin is not broken down so the channel protein remains open
so that iron ions can continue to diffuse into the blood increasing the concentration in the plasma
by faciliated diffusion
The mass of iron ions in the plasma of a person with haemochromatosis is 6104 μg
The iron ion concentration in the plasma of a healthy person is 50 μg dm–3
The volume of blood in each of these people is 4000 cm3
Calculate the ratio of the mass of iron ions in the plasma of the person with
haemochromatosis to the mass of iron ions in the plasma of the healthy person.
30.52:1
What is a tumour?
a clump of abnormal cells dividing uncontrollably by mitosis
uncontrolled cell division
Describe how you would determine a reliable mitotic index (MI) from tissue observed
with an optical microscope.
Do not include details of how you would prepare the tissue observed with an
optical microscope.
look at the field of view for the number of cells in mitosis and count the number of cells
look at the field of view of the total number of cells
count the number of cells in mitosis and divide by the number of total cells
repeat 5 times
calculate mitotic index
The scientists concluded that MI > 5 is a reliable indicator of how serious the cancer is
in a dog.
Use information from Figure 8 and Table 4 to evaluate this conclusion.
dogs with an M.I above 5 had a lower survival time and dogs with a lower M.I had a longer survival time
the difference in the mean survival time was not due to chance because the probability was 0.001 so there is a 99.9% chance that its due to scientific reasons
no range around the mean
Suggest why the number of E. coli cells per mm3 in each culture after 24 hours might
have been lower if the student had not used a sterilised pipette. Explain your answer
micro organisms alive attached to pipette which can produce toxins
The student diluted 3 cm3 of culture 1 with 12 cm3 of water. She observed a sample
of this diluted mixture using an optical microscope and counted 24 cells in
0.000 25 mm3 of the diluted mixture.
Use this information to calculate the number of cells per mm3 in undiluted culture 1.
480,000
Read the following passage. box
The placenta is a specialised exchange surface.
In the placenta, substances are exchanged between the blood of a fetus and
the blood of its mother. Gas exchange for the fetus occurs in the placenta.
There is also transfer of IgG antibodies in the placenta between the mother’s
blood and fetal blood. These IgG antibodies protect the fetus against the
pathogens that infect its mother during pregnancy. The IgG antibodies can
circulate at high concentration in the mother’s blood for months or years. A
fetus does not produce IgG antibodies.
The UK immunisation programme vaccinates as many babies as possible to
protect the UK population against pathogens such as measles viruses and
tetanus bacteria. Measles viruses spread quickly from infected people.
Despite the efforts of the NHS, there has been a recent increase in the number
of children catching measles.
Tetanus bacteria enter the body through skin wounds. Tetanus bacteria do not
spread from infected people. In order to develop good immunity against
tetanus, children are given three tetanus vaccinations at regular intervals
before they reach their first birthday.
Use the information in the passage and your own knowledge to answer the
following questions.
Gas exchange for the fetus occurs in the placenta (line 3).
Describe how the composition of blood in the pulmonary artery of a fetus is different
from the composition of blood in the pulmonary artery of its mother.
Give one reason for this difference.
fetal blood has a higher concentration of oxygen because gas exchange occurs in the placenta not lungs
Explain how a fetus is protected against the pathogens that infect its mother during
pregnancy (lines 5–6).
Do not give details of an active immune response in the mother.
(IgG) antibodies (from mother) are
complementary/bind specifically to antigens on placenta
antigen -antibody complex formed
Giving passive immunity (in fetus)
