A-level paper 1 mistakes Flashcards
Why might a patient have an unusually high proportion of eosinophils?
The patient will produce more of these cells due to an allergy
Explain why heart cells are damaged as a result of heart disease.
Plaque can lead to arteries becoming blocked
This deprives heart cells of oxygen
So cells cannot respire
Compare and contrast the properties and uses of embryonic stem cells and pluripotent stem cells (IPS cells)
Similarities:
Both are able to divide indefinitely
Both are able to differentiate into a number of different cells
Differences:
IPS cells were adult cells, embryonic cells taken from inner cell mass
IPS have a gene, embryonic stem cells don’t.
Less ethical issues surrounding IPS cells
IPS cells form adult cells whereas embryonic stem cells form younger cells
Explain how a mutation can result in a shortened protein being produced.
The mutation may produce a stop codon
Therefore translation will stop sooner
Some people have mutations that affect proteins involved in the electron transport chain.
Explain why these mutations lead to a build up of lactate.
Electron carriers can’t transport electrons
Reduced NAD will not be oxidised
So pyruvate will produce lactate
State the role of platelets in the blood clotting process.
They form a scab to seal the blood vessel.
What happens to oxygen availability in water as temperature increases?
It decreases
Describe the structure of a globular protein.
They have a 3 dimensional structure/ quaternary structure.
Held together by peptide bonds
Explain the role of the Krebs cycle.
Completely oxidises acetyl coA
To release energy
And generates ATP
Reduced NAD formed
Which can be used in the ETC
What substances are transported by xylem and phloem tissues?
xylem = water and mineral ions
Sucrose = water and sucrose
Describe the differences between the structure of the xylem and that of the phloem.
xylem cell walls contain lignin but phloem cell walls contain only cellulose.
Xylem is hollow but phloem has cell contents
Xylem doesn’t have companion cells but phloem does.
Do salmonella produce endo or exotoxins?
Endotoxins
A scientist wanted to grow some salmonella.
Explain why the use of streak plating on a selective media is a good method for isolating salmonella.
Media allows only salmonella to grow
Colonies will be spread out on agar
Separates individual bacteria
So colonies are individual and can be picked up.
Explain how stem rust fungus causes a reduction in a grain plant’s yield.
Stem rust fungus uses up nutrients.
Less glucose to form starch and for plant respiration.
Stem rust fungus also interferes with vascular tissue.
This can cause weakened stems.
State the meaning of DNA methylation.
The addition of a methyl group to a cytosine base.
Why is DNA methylation involved in the development of an embryo.
genes can be activated/ switched off
Causing cells to become specialised.
Compare and contrast the structure of amylose and amylopectin.
Both contain alpha glucose
Both contain glycosidic bonds.
Amylose is helical but amylopectin is branched.
Why do viruses have to be cultured with appropriate cells.
Viruses can only bind to one type of cell.
Due to receptors on their surface.
They cannot replicate without host cells.
Most ATP is produced by mitochondrial respiration.
Describe how the remaining ATP is produced.
During glycolysis, glucose is converted to pyruvate by substrate level phosphorylation.
Do archaea have ribosomes?
No
How many sets of chromosomes does a tube nucleus have?
1
Why does blood plasma have a higher protein content?
proteins are too large to diffuse through the capillary wall.
Why does tissue fluid have less dissolved oxygen than blood plasma?
Oxygen has diffused into the cells.
what happens to the tissue fluid that is not reabsorbed into the blood capillary?
Tissue fluid enters the lymphatic system.
Lymph returns to the blood.
Bone marrow stem cells can differentaite into 2 different cells.
Explain why.
Epigenetic modification.
For example DNA methylation.
Genes needed in both cell types remain switched on.
Then genes needed for one cell may become switched off.
Causing proteins to be made that are specific to one cell type.
Explain the importance of vaccinating as many people as possible against rubella.
Results in herd immunity.
Fewer infected people to pass virus onto unaffected people.
Is there hydrogen bonding in carbohydrates and lipids?
Carbohydrates = yes
Lipids = no
Explain why lipids can be respired in only aerobic conditions?
In anaerobic conditions, pyruvate is used to reoxidise NADH so no krebs cycle.
No oxygen available to act as terminal electron acceptor.
NADH and FADH2 cannot be oxidised.
So no coenzyme can bind to H+
Explain how the types of bacteria found in the female genital tract could be identified.
Take a sample from the female genital tract.
Grow bacteria on an agar plate.
Add different antibiotics to the agar.
Use of antibodies.
Use the shape of colonies to distinguish.
Compare and contrast the structure of fructose with the structure of glucose.
Both are hexose sugars.
Both have covalent bonds.
Glucose has a hexagon shape, fructose has a pentagon shape.
Glucose has one CH2OH whereas fructose has 2.
Explain the advantages of the presence of fructose in seminal fluid.
Acts as an energy source for the sperm.
Movement through the female genital tract requires ATP.
In order to reduce competition for carbohydrates with the bacterial cells in the female genital tract.
