Practice questions Flashcards
Name a property of a DNA barcode that makes it ideal for identifying species.
shows a large amount of variation between species
Which of the reactions occurs in the blood clotting process?
A) Fibrinogen is converted to fibrin by the enzyme thromboplastin
B) Prothrombin is converted to thrombin by the enzyme thromboplastin
B) Prothrombin is converted to thrombin by the enzyme thromboplastin
What would be the correct antigens and antibodies for a patient receiving blood from a donor with blood group AB?
A and B antigens on erythrocytes
no antibodies in blood plasma
reason: AB donor matches AB patient blood group
Are neutrophils granulocytes or agranulocytes?
granulocytes
Which part(s) of a RNA nucleotide can form a phosphodiester bond with other nucleotides?
phosphate group and OH of the pentose sugar
Name and describe the 4 key features of the genetic code
degenerate - more than 1 codon for each amino acid
non-overlapping - each one codon/triplet in the sequence is read separately
triplet code - three bases are needed to code for one amino acid
universal - the same in almost all organisms
What feature of the DNA molecule provides stability?
phosphodiester bonds / sugar-phosphate backbone / double helix
Name the membrane which surrounds the vacuole in plant cells.
tonoplast
At a low pH, will a solution be more or less acidic?
How will protons affect proteins and membranes?
more acidic
protons will affect the ionic bonds in proteins and cause them to denature, causing membranes to become more permeable
Describe the inflammatory response
triggered by damaged cells / entry of pathogens
mast cells release histamine causing vasodilation
there is increased blood flow to the area
capillary walls are more permeable, making it easier for phagocytes to leave the blood
Describe how an ultrasound is used to measure the biparietal diameter of a fetus.
handheld transducer emits sound waves into the mother’s body which are then reflected back by the fetus to produce an image of the fetus on a monitor screen
a transducer can be used to provide different angles
the head of the fetus is measured at its widest point for the BPD
Suggest 4 factors that should be taken into account when using a growth chart to estimate the gestational age of a fetus
gender
maternal lifestyle
genetics
if a twin, the fetus could be smaller
During _ of meiosis 1, homologous chromosomes begin to pair up to form a bivalent.
prophase
During meiosis 1, alignment on the equator of the spindle and separation of the chromosomes in each pair to opposite poles of the cell is random. This process is called _.
independent assortment
Explain the term PEFR.
peak expiratory flow rate = the maximum rate at which air is forcibly exhaled
Explain the term FEV1
forced expiratory volume in one second = the volume of air that can be breathed out in the first second of forced exhalation
If FEV1 is lower than expected, this could be…?
a respiratory problem (airways reduced or restricted)
How must expired air resuscitation differ when being carried out on a child (3 ways)?
smaller puffs of air expired
head not tilted back as far
cover the mouth and nose of the child
Name the key advantage of a live-attenuated vaccine?
gives the strongest immune response and long lasting immunity
Name the 3 key advantages of killed inactivated pathogens?
safer / more stable than live vaccines
do not require refrigeration
can be given to patients with weakened immune systems
If the anticodon of the tRNA molecule specific to the amino acid phenylalanine (phe) is AAG. Which of the following statements is correct?
A) the triplet on the template strand that codes for phe is AAG
B) the triplet on the sense strand that codes for phe is AAG
C) the triplet on the template strand that codes for phe is TTC
D) the triplet on the sense strand that codes for phe is UUG
A) the triplet on the template strand that codes for phe is AAG
reasoning: template (antisense) strand = template for transcription with complementary bases to mRNA and the DNA sense strand
sense strand = same base sequence as RNA (T replaced with U in mRNA)
the anticodon of the tRNA has the same base sequence as the template strand (but uses U)
template strand bases = tRNA bases
sense strand bases = mRNA bases
Which of the following statements about fossil evidence does not support the conclusion that hominids were bipedal?
A) Hominids have a large cranial capacity
B) Hominid vertebral columns have a double curve
C) Hominid feet are arched
D) Hominid thigh bones slope inward from hip to knee
A) Hominids have a large cranial capacity
reason: bipedal = using only two legs for walking
What is cell x if it is a leucocyte and can differentiate to become a plasma cell?
B lymphocyte
Where are antibodies synthesised?
on the RER
How are the 4 polypeptide chains of an antibody molecule held together?
by disulfide bonds
Many bananas in shops are triploid. Which stage of the cell cycle would they be unable to complete? A) cytokinesis B) mitosis C) meiosis D) S phase
C) meiosis
reason: meiosis only occurs in gamete formation
A 40yr old man has measured blood pressure of 170/105mm Hg. Which of the following best describes the interpretation of this reading? A) high normal B) hypertension requiring treatment C) hypotension D) mild hypertension
B) hypertension requiring treatment
reason: 140/90mm Hg and above requires treatment
What type of bonds can the R group of an amino acid form in the tertiary structure of a protein?
hydrogen bonds
In people with a patent foramen ovale (PFO), there is a small gap in the atrial septum allowing some blood to pass between the atria. Explain why the circulatory system of a person with PFO may not be considered a double circulatory system.
Not all blood will pass through the heart twice in 1 circuit.
Some blood will not pass through pulmonary circulation.
Outline 3 advantages of a closed circulatory system.
smaller volume of transport fluid/blood required
blood supply to different organs can be varied
maintaining blood pressure
How could you confirm the presence of protein in a sample of blood plasma?
carry out a biuret test
positive result for protein = purple colour
The passage of a cell through the different stages of the cell cycle is regulated by a group of _ called cyclin-dependent kinases (CDKs).
enzymes
Without p21, cyclin-dependent kinases (CDKs) are permanently active. As a result, damaged/mutated cells continue dividing. For this reason the gene coding for p21 is referred to as a _ gene.
tumour suppressor
Name the test for reducing sugars and an appropriate water bath temperature.
Benedict’s test
above 70 degrees c
Using an example, explain what you understand by the term notifiable disease.
a communicable disease which you have the legal obligation to inform competent health authorities of
examples not limited to: scarlet fever, anthrax, cholera, food poisoning E. coli, mumps, rubella
Tobacco smoke is a carcinogen. It can damage the DNA of the cells lining the trachea resulting in the development of a tumour. Explain how damage to DNA can result in the development of a tumour.
mutation / described
proto-oncogenes become oncogenes
(causes) uncontrolled, mitosis / cell division / cell replication
idea that damages p53 gene
idea that mutation / damage, could be in tumour suppressor gene
Research was carried out into the effect of smoking on the incidence of lung cancer. State 5 factors that should have been considered when selecting people to participate in this research
age range underlying medical conditions how long they have smoked for gender family history of lung cancer
Lung cancer can be detected using a technique called an endoscopic ultrasound. When using this technique, instead of placing the ultrasound probe on the outside of the chest, it is inserted through the mouth and into the airways of the lungs. Suggest why endoscopic ultrasound is used rather than standard ultrasound for detecting lung cancer.
idea that a clearer image can be gained without interference from the rib cage
The number of people alive 10 years after being diagnosed with a disease is called the ten year survival rate. Suggest why the 10 year survival rate for lung cancer is low.
idea that no symptoms / symptoms similar to minor illness
rarely diagnosed early
difficult to treat / lumpectomy often not possible
no routine screening for lung cancer
During chemotherapy treatment, the majority of body cells are not affected by the drugs used. However, some cells, such as those in hair follicles and bone marrow, may be damaged by chemotherapy drugs, why?
idea that cells undergo cell division regularly
Supraventricular tachycardia (SVT) is a medical condition affecting heart resulting in an abnormal rhythm. One of the signs of SVT is that the atria do not contract correctly. Describe how the ECG trace of a patient with SVT would differ from the trace of a person with a healthy heart.
idea that there is no clear P-wave
idea that there is increased frequency
Describe the first aid procedure used to treat a patient suffering a heart attack and how the procedure would change if they later suffered a cardiac arrest.
Heart attack treatment: sit patient, down with support / in W position call 999 / emergency services reassure / calm then down idea of monitoring vital signs
Cardiac arrest treatment:
lie patient down
CPR / description of CPR
(request) defibrillator (if in public space)
Hominids have been classified using taxonomic ranks. Give the sequence of taxonomic ranks in the hierarchy of classification (8)
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
Homo habilis is a species of hominid that lived in central Africa between 2.8 and 1.5 million years ago. Since the discovery of Homo habilis fossils during the 1950s, scientists have debated whether this species should have been placed within the genus Australopithecus. Name 5 types of evidence useful in classifying a species and 5 types of evidence that would not be useful.
Types of evidence useful in classifying a species: Fossil records Carbon dating Morphology Anatomy Physical features
Evidence not useful: Embryo development Biochemical molecules e.g. DNA / amino acids Behaviour Immunology Fossil records may be incomplete
Explain how different tools can provide evidence of hominid evolution
tools are specialised
require greater dexterity to make
shows increased use of hands/tools
shows more complex thought processes
Isoniazid is one of the antibiotics used to treat TB. Isoniazid works by inhibiting the production of mycolic acid, a fatty acid required for the synthesis of some bacterial cell walls. Explain how isoniazid causes the death of M. tuberculosis cells.
Also, why does Isoniazid kills bacterial cells but has no effect on human cells?
cell wall not synthesized
water enters (cells) by osmosis
from a higher water potential to lower water potential
cells, lyse / burst
human cells do not have cell walls
human cells do not need mycolic acid
Why would a haemocytometer slide by cleaned with ethanol?
to remove grease / fingerprints
When preparing a blood sample for use with a haemocytometer, why may a diluting fluid, such as Dacie’s fluid be used?
solution is not too concentrated to count cells accurately
Dacie’s fluid preserves shape of RBC’s so they are easier to count
When preparing a blood sample for use with a haemocytometer, why may a stain be added to the diluting fluid?
makes, nuclei / white blood cells, visible
Why could dropping a solution onto a petri dish be a cause of error in an experiment?
the petri dish should be flooded with solution to ensure even coverage
As water molecules move through xylem vessels they are attracted to each other by _ forces. The water molecules are also attracted to the walls of the xylem vessel by _ forces. The walls of the xylem vessel are strengthened by _ which is impermeable to water
cohesive
adhesive
lignin
bordered pits
Which of the options, A to D, is a meiotic process that does not give rise to genetic variation?
A) crossing over of non-sister chromatids
B) crossing over of sister chromatids
C) independent assortment of chromatids
D) independent assortment of chromosomes
B
A length of DNA has the following sequence: GATACTCCAG
Which of the following options, A to D, is the mRNA sequence that would be transcribed from this length of DNA?
A) CTAGGAGTATC
B) CUAGGAGUAUC
C) CTATGAGGATC
D) CUAUGAGGAUC
D
Plants exchange gases through stomata. The opening and closing of stomata is controlled by guard cells. Which of the two sequences would result in open stomata?
- K+ enters guard cells. The water potential of the cells is decreased. The cells take in water.
- K+ leaves guard cells. The water potential of the cells is increased. Water leaves the cells.
- K+ enters guard cells. The water potential of the cells is decreased. The cells take in water.
Which of the following is a biological molecule that contains ester bonds? amylase cellulose lipid ribulose bisphosphate
lipid
Which of the following statements are correct?
1) at any partial pressure of oxygen, myoglobin has a lower oxygen saturation level than adult haemoglobin.
2) the oxygen dissociation curves for fetal and adult haemoglobin are sigmoidal due to cooperative binding of oxygen
3) haemoglobin releases oxygen more readily at a low pH
only 2 and 3 are correct
These statements describe the response to light by a rod cell in the retina. Which are correct?
1) the plasma membrane becomes hyperpolarised
2) rhodopsin is broken down
3) glutamate is released from a rod cell, causing depolarisation of a connecting bipolar cell
only 1 and 2 are correct
A study was conducted to determine the effect of alcohol on reaction time. 20 participants were asked to record as fast as possible to visual cues, before and after drinking a fixed quantity of alcohol. Two data sets were produced. Which of the options would be the appropriate statistical method for analysing data from this study? chi squared test paired Student's t-test unpaired Student's t-test Spearman's rank correlation coefficient
paired Student’s t-test
Explain how the loop of Henle performs its role in the production of urine
- (role is) to set up a range of water potential gradients between medullary tissue fluid and collecting duct
- diffusion of water out of descending limb
- ion concentration high at base of loop
- sodium and chloride ions diffuse out of base of ascending limb
- water cannot leave ascending limb / ascending limb impermeable to water
- ions pumped out of upper ascending limb
Iron is essential for the activity of the nitrogen-fixing enzyme, nitrogenase. Iron is present as ions in soil water but is not taken up by root nodules directly. Describe how iron ions in soil water reach the root nodules
(active transport) into root hairs
apoplast / symplast pathway
through epidermis / cortex layers
via xylem vessel to (root) nodule
Explain why a knockout of the gene encoding GnRH causes infertility in female mice
FSH & LH not released follicle not stimulated / oocyte does not develop (by FSH) no ovulation (by LH)
What is the role of cristae in the function of the mitochondrion?
provides a large surface area for oxidative phosphorylation / ATP production
State the importance of the intermembrane space for mitochondrial function
reduced NAD/reduced FAD oxidised on inner membrane
inner membrane not affected
Name 3 genetic diseases caused by a substitution mutation
sickle cell anaemia
PKU
cystic fibrosis
Explain why a substitution at a point in an intron will not result in a genetic disease
idea that code in this region does not appear in mature mRNA
idea that introns are transcribed but edited out
When a substitution mutation in part of an exon results in a change from triplet AGA to AGG, this did not result in a genetic disease. Why?
idea that genetic code is degenerate
idea that new triplet codes for an amino acid with a similar R group
no change in the tertiary structure of the protein
What type of gene is p53?
tumour suppressor gene
Other than not being able to repair DNA or initiate apoptosis, what other function will a p53 not be able to carry out if it is inactivated?
cell cycle not stopped at check points
How is a phosphodiester bond in DNA formed?
condensation reaction
In human DNA, the frequency of CpG sites across the genome varies. Analysis of the base content of human DNA shows that 21% of the bases present are cytosine. What is the expected frequency of a CpG site in the DNA?
0.044
State the precise location of TAAs (tumour suppressor antigens) on tumour cells
cell surface membrane
An anticancer vaccine would lead to the production of antibody molecules that recognise TAAs (tumour suppressor antigens) in the host. Explain how the structure of the antibody molecule would enable it to recognise only TAAs
idea of variable region being complementary to antigen
idea that different antigens would have a different (3D) shape
Skin temperature values obtained for fingers were always approx. 10 degrees C lower than those obtained for the upper arm. Why? (4 biological reasons)
larger surface area to volume ratio in fingers
more heat loss from surface of fingers
more muscle mass in upper arm
more heat generated (in muscle)
