Year 12 Biology Test January 2024 Flashcards
Describe the mechanism for the absorption of amino acids in the ileum
Amino acids absorbed by facilitated diffusion
This maintains the concentration gradient
Sodium ions pumped
Which creates a sodium ion gradient
The resolution of an image using an electron microscope is higher than the resolution of an image obtained using an optical microscope
Explain why.
Electrons have a shorter wavelength than light
Figure 2 is an image obtained using a scanning electron microscope
Figure 2 is different from an image of this bacterium obtained using a transmission electron microscope
Describe and explain one difference between these images
Description: SEM produces a 3D image whereas a TEM produces a 2D image
Explanation; The electrons do not pass through the specimen
Name two structures found in all bacteria that are not found in plant cells
- Circular DNA
- Murein Cell wall
Name two features of HIV particles that are not found in bacteria
Do not include attachment proteins in your answer.
- RNA genome
- Capsid
Many proteins are enzymes
In 1894, a scientist suggested the lock and key model of enzyme action
Figure 5 shows the lock and key model
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 the active site of the enzyme
Difference: The active site changes shape to fit complementary to the substrate in induced fit model but does not change in the lock and key model
The enzyme maltase catalyses the hydrolysis of maltose to glucose
A scientist investigated maltase activity in two different maltose solutions G and H
For each solution he measured:
. The total number of glucose molecules produced by complete hydrolysis of the maltose
. The time taken for the complete hydrolysis of the maltose
Complete Table 3 by calculating the time taken for the complete hydrolysis of the maltose in solution H. Assume the rate of maltase activity is the same in solution G and in solution H.
Show your working
4 x 10^7/20 = 2,000,000 molecules per second
6 X 10^8 / 2,000,000 = 300 (s)
OR
6 X 10^8/ 4 X 10^7 = 15
20 X 15 = 300 (s)
Figure 6 shows the scientist’s results for solution G. Curve I shows the results of a similar investigation in which he changed one indep3endent variable
Tick one box next to the statement which describes the independent variable that the scientist changed to give the results shown by curve I
Increased maltase concentration
Explain a property of iron ions that enables these ions to carry out their role in red blood cells
Iron ions are polar
They have a positive charge which allows them to bind to oxygen molecules
The hormone hepcidin controls the iron ion concentration in blood plasma. Hepcidin affects ferroportin, the iron ion channel protein in cell-surface membranes
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
If ferroportin is present iron cannot be hydrolysed which means that there is more ferroportin in the cell-surface membranes which means that there are more iron ions in the cytoplasm of the cells in individual with haemochromatosis
The mass of iron ions in the plasma of a person with haemochromatosis is 6104 ug. The iron ion concentration in the plasma of a healthy person is 50ug dm^-3. The volume of blood in each of these people is 4000cm^3
Calculate the ratio of the mass of iron ions in the plasma of the person with haemochromatosis to the mass in the plasma of the healthy person
mass of ill : mass of healthy
ill = 6104 ug
healthy 50 ug dm^-3
1 dm^3 = 1000 cm^3
50 x 4 = 200
200 ug in 4 dm^3
/ 200 6104 : 200 / 200
3052: 15.26
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
Number of cells in field of view/ Total number of cells then repeat several times
The scientist 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
P value is significant
Mean doesn’t give an accurate value for survival period range would be better
Dogs with grade 1 tumours all have M1<5
Dogs with M1>5 all have shorter survival times
