exam questions 1-4

Question 1

what are ribosomes made of

Answer 1

protein and RNA

Question 2

describe the role of ribosomes in polypeptide production.

Answer 2

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

Question 3

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.

Answer 3

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

Question 4

State three comparisons of genetic diversity that the scientists use

Answer 4

dna base sequence
mrna base sequence
amino acid base sequence

Question 5

Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange

Answer 5

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

Question 6

Suggest two ways the student could improve the quality of her scientific drawing

Answer 6

add more labels
no shading
single lines no sketching
add scale

Question 7

Contrast how an optical microscope and a transmission electron microscope work
and contrast the limitations of their use when studying cells.

Answer 7

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

Question 8

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

Answer 8

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

Question 9

difference between RNA and DNA molecules?

Answer 9

DNA has bases AGCT RNA has AGCU
DNA is longer than RNA
DNA has Deoxyribose RNA has ribose

Question 10

why can lipids not travel accross cell surface membrane

Answer 10

It is hydrophillic

It is too big

Question 11

describe the induced model fit enzyme action?

Answer 11

before reaction active site not complementary
shape of active site changes as sustrate binds
distorting bonds in substrate leading to reaction

Question 12

what is a statistical test to compare means?

Answer 12

T test compares means

Question 13

t why the development of a monopolar mitotic spindle (chromosomes not lining up in the middle of cell) would prevent successful mitosis.

Answer 13

chromatids cannot split successfully
chromosomes all end up at one side
meaning one cell has double the chromsomes and the other has none

Question 14

difference between prokaryotic DNA and Eukaryoric DNA?

Answer 14

Eukaryotic DNA is linear associated with proteins/histones
Prokaryotic DNA is circular not associated with proteins/histones
Prokaryotic DNA is found in plasmids

Question 15

give 2 reasons as to why cells in figuire 1 are undergoing mitosis?

Answer 15

Indivudual chromosomes are more condensed and can be seen

chromosomes are made up of 2 chromatids because DNA has been replicated

Question 16

Give one reason as to why the structure of the chromosome could differ the results of the stain binding more in some areas?

Answer 16

Difference in DNA base sequences

Question 17

Describe a method of to measure the effect of surface area on osmosis

Answer 17

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

Question 18

Use your knowledge of directional selection to explain the results shown in Table 3

Answer 18

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

Question 19

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

Answer 19

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

Question 20

Role of DNA polymerase?

Answer 20

joins the DNA nucleotides to produce a phosphodiester bond (not between complimentary bases)

Question 21

Describe the gross structure of the human gas exchange system and how we breathe
in and out.

Answer 21

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

Question 22

where are glycoproteins produced?

Answer 22

Golgi body

Question 23

describe the formation of galactose?

Answer 23

glucose + lactose
condensation reaction
forms glycosidic bonds

Question 24

compare tryglyceride and phospholipid?

Answer 24

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

Question 25

what is a null hypothesis?

Answer 25

It suggests that their is no statistical significance between 2 variables

Question 26

what is used to test the null hypothesis to prove their is no statistical deviation?

Answer 26

Chii squared test is a way of measuring if their is any deviation between the observed and expected results

Question 27

describe how to use the chi squared test?

Answer 27

Find the square root of chii value
find the degrees of freedom(variables measured-1)
look along the the probability
if the chii value is less than the critical value reject null hypothesis (variable does affect what are you are measuring)
if the chii value is greater than critical value accept null hypothesis (Any difference is due to chance)

Question 28

No large lipid droplets are visible with the optical microscope in the samples from
suspension A

Answer 28

emulsification produces small droplets which cannot be shown under small resolution

Question 29

Cells with BrdU in their DNA are detected using an anti-BrdU antibody with an enzyme
attached.
Use your knowledge of the ELISA test to suggest and explain how the scientists
identified the cells that have BrdU in their DNA.

Answer 29

Add Antibody which has enzyme attached
wash immobilised antibody to remove any excess cells
Add substrate which should cause colour change

Question 30

Suggest how Ulva lactuca is able to survive without xylem tissue.

Answer 30

Is semi permeable allows water/ions to flow through

Question 31

Explain five properties that make water important for organisms

Answer 31

cohesion allows it to be taken up plants via the xyle,
Cohesion allows small organisms to move across
high latent heat of vaporisation provides a cooling affect via sweating (evaporation)
specific heat capacity acts as a temperature buffer
solvent allows reactions to occur

Question 32

lipid test?

Answer 32

emulsion test
add ethanol
turns milky/white

Question 33

reducing agent test?

Answer 33

Add benedics agent
heat up
turns from blue to orange / red depending the strencth of reducing agent

Question 34

non reducing agent test?

Answer 34

Do benedicts test should get a negative result (blue colour)
Add HCL to hydrolyse and NaOH to neutralise
add benedict reagent
should now produce a positive test
blue -> red/orange