exam questions 1-4 Flashcards
(34 cards)
what are ribosomes made of
protein and RNA
describe the role of ribosomes in polypeptide production.
mRNA binds to ribosome
2 m codons can bind at a time
allows trna with anticodons to bind
catalyses the peptide bond between amino acids
Sodium ions from salt (sodium chloride) are absorbed by cells lining the gut. Some
of these cells have membranes with a carrier protein called NHE3.
NHE3 actively transports one sodium ion into the cell in exchange for one proton
(hydrogen ion) out of the cell.
Use your knowledge of transport across cell membranes to suggest how NHE3
does this.
co transport. adp is hydrolysed to atp.this is used by NHE3 which binds to na+ and H+. this changes its shape and allows it to move through the membraene
State three comparisons of genetic diversity that the scientists use
dna base sequence
mrna base sequence
amino acid base sequence
Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange
tracheoles have thin walls short diffusion pathway
many tracheoles so short diffusion pathway
end of tracheoles dipped in water and can move out to allow gas phase diffusion which is quicker
Suggest two ways the student could improve the quality of her scientific drawing
add more labels
no shading
single lines no sketching
add scale
Contrast how an optical microscope and a transmission electron microscope work
and contrast the limitations of their use when studying cells.
TEM uses electrons oprical uses light TEM greater resolution TEM allows smaller organeles to be seen TEM can only see dead specimen Optical can see alive specimen TEM no colour Optical shows colour TEM requires thinnner specimen
Describe how he should collect and process data from these seeds to investigate
whether there is a difference in seed size between these two populations of trees
use random sample of seeds from each population
sample is large enough to be representative
indication of size e.g mass,length
calculate mean and standard deviation
use t test
anaylse difference
difference between RNA and DNA molecules?
DNA has bases AGCT RNA has AGCU
DNA is longer than RNA
DNA has Deoxyribose RNA has ribose
why can lipids not travel accross cell surface membrane
It is hydrophillic
It is too big
describe the induced model fit enzyme action?
before reaction active site not complementary
shape of active site changes as sustrate binds
distorting bonds in substrate leading to reaction
what is a statistical test to compare means?
T test compares means
t why the development of a monopolar mitotic spindle (chromosomes not lining up in the middle of cell) would prevent successful mitosis.
chromatids cannot split successfully
chromosomes all end up at one side
meaning one cell has double the chromsomes and the other has none
difference between prokaryotic DNA and Eukaryoric DNA?
Eukaryotic DNA is linear associated with proteins/histones
Prokaryotic DNA is circular not associated with proteins/histones
Prokaryotic DNA is found in plasmids
give 2 reasons as to why cells in figuire 1 are undergoing mitosis?
Indivudual chromosomes are more condensed and can be seen
chromosomes are made up of 2 chromatids because DNA has been replicated
Give one reason as to why the structure of the chromosome could differ the results of the stain binding more in some areas?
Difference in DNA base sequences
Describe a method of to measure the effect of surface area on osmosis
prepare 1 large potatoe and 8 small potatoes of the same length
measure the original mass
engulf all of it in sugar solution so all sides are covered
make sure temperature is constant (room temp)
at selected intervals (5 mins) dry the potatoe and weigh
Complete this process for 40 mins
Use your knowledge of directional selection to explain the results shown in Table 3
scientist only used plants that produced 2n gametes
These plants passed over their alleles to their 2n gametes offspring
Over time the frequency of this allele increases
During vaccination, each animal is initially injected with a small volume of venom.
Two weeks later, it is injected with a larger volume of venom.
Use your knowledge of the humoral immune response to explain this vaccination
programme
When the pathogen is first injected
The B cells bind and divide by mitosis to produce memory cells and plasma cells
This small dose allows the animal to produce the initial antibodies which require time
the 2nd dose the memory cells can divide to produce many plasma cells and hence many antibodies immediatedly and at a higher concentratoin
Role of DNA polymerase?
joins the DNA nucleotides to produce a phosphodiester bond (not between complimentary bases)
Describe the gross structure of the human gas exchange system and how we breathe
in and out.
Air moves through trachea ,bronchi ,bronchioles to alevoli
When breathing in diaphragm contracts external intercostal muscle contracts
this increases vol decreases pressure in thoracic cavity to below atmospheric pressure forcing air in
When breathing out diaphragm contract internal intercostal muscle contracts
decreasing vol increase pressure air forced out via pressure gradient
where are glycoproteins produced?
Golgi body
describe the formation of galactose?
glucose + lactose
condensation reaction
forms glycosidic bonds
compare tryglyceride and phospholipid?
tryglecerides have 3 fatty acids phospholipid has 2 fatty acid
both have phosphate group and glycerol
both have ester bond
both have saturated/unsaturated chain
only phospholpic can produce a bilayer in water
both insolouble
