biology paper 3

Question 1

formation of urea

Answer 1

deamination
ammonia combines with co2
the ornithine cycle produces urea

Question 2

enzyme increae in temp

Answer 2

enzyme denatures
hydrogen bonds broken
tertiary struture changed/active site
substrate complexes can no longer form

Question 3

process of atherscelrosis

Answer 3

damage to {endothelium} caused by
{high blood pressure / toxins / smoking}
 inflammatory response and arrival of
{macrophages / white blood cells}
 deposits of {cholesterol / calcium}
 formation of {atheroma / plaque}

Question 4

how do vaccines create immunity

Answer 4

antigen presenting cells / MHCs
 APC binds to {T cell /CD4 receptors}
 production of T memory cells
 (activated) T cells
{stimulate B cells / release cytokines}
 production of B memory cells
 plasma cells release antibodies

Question 5

why initial rate of reaction

Answer 5

so substrate conc is not limiting

Question 6

adaptations of the phloem

Answer 6

• companion cells for ATP production
• because sieve tubes are for transport of organic molecules
• because energy is needed for transport (both up and down the stem)
• sieve tubes have no organelles, so less barriers to transport

Question 7

critisice sampling methods

Answer 7

quadrats not placed at random (1)
* {size / number} of quadrats not mentioned
* plants sampled at various intervals, animals at regular ntervals
*both animals and plants sampled
* animals may {hide / move away / be counted twice} (1)
* whole area sampled
* survey done at only one {time of year / time of day} (1)

Question 8

good treatment for humans

Answer 8

dosent harm human cells
side effects

Question 9

divise an experiemnt

Answer 9

equal things being measured
controll abiotic
change in factor
measure change over set time
stat test
if relevant
-slelect area with differences
-quadrats
-random or on transect
large sampel size

Question 10

how to prepare a microscope slide

Answer 10

cut thin layer
place in conc acid to break down middle lamella
heat to intensifty acid
stain
heat to intesify stain
tease with mounted needle
place coverslip and squish to remove air bubbles
find on low power
view on high power

Question 11

double firtilisation

Answer 11

one male nucleus fuses with the two polar nuclei to form a triploid nucleus
* one male nucleus fuses with the egg cell to form a diploid zygote

Question 12

pollen tube experiment

Answer 12

at least 5 different values tested
sucrose solution added
suitable time before pollen tube measured
method of measurement of pollen tube with a
microscope described - stage micrometer and eyepiece
* method of calculation of rate of growth - lenth over time
* method of control of one relevant variable
* a repeat at each variable and calculate mean

Question 13

natural selection questions

Answer 13

name selection pressure
random mutation
benificial allele
allele frequency increases

Question 14

movement of mineral ions by active transport

Answer 14

acroos membranes by carrier proteins using atp against conc grad

Question 15

compare and contrasy zylem and phloem

Answer 15

both tissues contain tubes
* both have cell walls containing cellulose
* xylem vessels contain lignin, but phloem does not
* in xylem, end walls of cells break down completely but in phloem there are
sieve plates
* phloem (sieve tubes) have companion cells, but
xylem does not
* phloem (sieve tubes) contains cytoplasm, but
xylem does not
xylem has pits in the walls phloem does not
phloem has sieve plates, but xylem does not
phloem contains plasmodesmata but xylem does
not

Question 16

how to stop transpiration

Answer 16

petronium jelly

Question 17

definiton of gpp + units

Answer 17

the rate at which producers make organic material
(by photosynthesis)
g m-2 year-1