paper 1 2019

Created by

neha

Cards (29)

A student investigated mitosis in the root tip of a garlic plant.
Explain why the student used the tip of the root.
The root tip contains meristems for growth
The student squashed the root tip on a microscope slide to spread out the cells.
The slide was placed on the stage of a microscope.Describe how to use the microscope to obtain a clear image of the cells.
Start with the lowest objective lens x4. Use the focusing wheel to obtain a clear image
The student could not see the chromosomes inside the cells.State what can be added to the root tip squash to make the chromosomes visible.
iodine solution
Figure 1 shows a root cell in a stage of mitosis.
Which stage of mitosis is shown in Figure 1?
A prophase B metaphase C anaphase D telophase
answer = anaphase
Describe what is happening in Figure 1.
Spindle fibres are pulling chromosomes apart chromatids are pulled to opposite ends of the cell
Chlamydia is caused by a pathogen.
Chlamydia is transmitted by
A insect vectors
B sneezing
C sexual intercourse
D contaminated food
answer = sexual intercourse
The type of pathogen that causes chlamydia is a
A bacterium B fungusC protistD virus
answer = bacterium
Figure 2 shows the number of cases of chlamydia in the United Kingdom per 100 000 people between 1996 and 2013.
Describe the trend in the number of cases of chlamydia between 1996 and 2013.
the number of cases increases then decreases
State the number of cases of chlamydia per 100 000 in 2013.
= 1800
The population of the United Kingdom in 2013 was 64 000 000.
Calculate the number of people with chlamydia in 2013.
= 64000000/100000
= 640 x 1800 = 1152000
Figure 3 shows the activity of the enzymes pepsin and trypsin at different pH levels.
Describe the trend in the graph for the enzyme trypsin.
Use data from the graph to support your answer.
the enzyme activity increases from 5.8 - 8 pH
the optimum pH is 8
State the optimum pH for the enzyme pepsin.
= 2
Pepsin only works effectively in the stomach.Describe the conditions in the stomach that allow pepsin to work effectively.
stomach circumstances of pH are low
stomach produces hydrochloric acid
At high pH values the active site of the enzyme pepsin changes shape.
When the active site of the enzyme changes shape, the enzyme is
A specific B denatured C digested D dead
answer = denatured
State what is produced when proteins are digested.
amino acids
A karyogram is a picture of the chromosomes found in the nucleus of a single cell.
Figure 4 shows a human karyogram.
State two reasons why this karyogram cannot be from a gamete (sex cell).
Because it has an X and a Y chromosome
gametes only have 23 chromosomes not 46
State the gender shown by this karyogram.
male
Figure 5 shows two sperm cells.
Name structure Z.
acrosome
Sperm B has a larger middle section than sperm A.
Explain why sperm B will be more likely to fertilise an egg than sperm A if they were both released at the same time
Sperm B has a bigger middle section meaning that it has more mitochondria therefore can release more energy and can move faster
James Watson and Francis Crick built a model that showed that DNA has a double helix structure.
Which statement about DNA is correct?
A each pair of bases is joined by hydrogen bonds
B phosphate groups are joined by hydrogen bonds
C nucleotides consist of a sugar and a phosphate group only
D bases are joined to phosphate molecules
answer = each pair of bases is joined by hydrogen bonds
Figure 6 shows the percentage of each base in human DNA.
Describe how this data provides evidence for base pairing in DNA.
A and T have equal amounts of DNA
A pairs with T and C pairs with G
A scientist obtained a mass of 0.0062 nanograms of DNA from a diploid human cell.
Calculate the mass of DNA the scientist should obtain from a haploid human cell.
Give your answer in picograms.(1 nanogram = 1000 picograms)
0.0062 x 1000 = 6.2
6.2/2 = 3.1
A student used the method shown in Figure 7 to compare the mass of DNA extracted from strawberry fruit cells and from kiwi fruit cells.
crush the fruit cells in a buffer solution
filter to separate the soluble DNA from the cell fragments
add ethanol. State why ethanol is used.
To precipitate the DNA
State two variables the student needs to control when using this method to compare the mass of DNA from these two fruits.
volume of ethanol
mass of fruits
The student repeated the experiment.
Give one reason why.
to calculate a mean
Mitosis and meiosis are processes that produce new cells.
Compare the outcomes of mitosis and meiosis.
Mitosis = 2 genetically identical diploid daughter cells whereas Meiosis = 4 genetically different haploid daughter cells.
Clostridium tetani is a bacterium that can be found in soil.
It causes the infection tetanus.
Children are vaccinated against tetanus.
Explain why these children do not get tetanus if the bacteria enter their body through a cut in the skin.
They are immune to clostridium tetani because the vaccination contained an antigen which caused memory lymphocytes to be produced leading to the production of antibodies which causes a secondary response to occur
Colistin is an antibiotic used to treat infections in the bloodstream.
Some bacteria are resistant to Colistin.Explain how these bacteria have become resistant to Colistin.
People do not stop taking Colistin
natural selection occurs
some bacteria has mutations (changes in their DNA)
the resistant bacteria survives
Figure 8 shows three stone tools found in different layers of rock.
Explain how information from Figure 8 provides evidence for human evolution.
The further down the stone tools are the older they are.
Stone tool A is the most sophisticated as it is the one with the most point.
Stone tool C is round, stone tool B is still round but has a point on it and stone tool A has the best developed point therefore showing evidence of human evolution.