Advanced article 2017

Question 1

what is the definition of population?

Answer 1

the number of all the organisms of the same group or species, which live in a defined geographical area and have the capability to interbreed successfully

Question 2

what is the aim of genetic engineering?

Answer 2

to introduce a new trait to an organism that does not occur naturally in the species

Question 3

how do gene guns work?

Answer 3

DNA bound to tiny gold/tungsten particles

particles shot into plant tissue under high pressure, penetrating cell wall and CSM

DNA separates and is integrated into nuclear DNA

Question 4

how does Agrobacterium tumefaciens mediate transferal of genetic information?

Answer 4

desired gene is incorporated into DNA plasmid and inserted into A. tumefaciens

plasmid acts as vector

A. tumefaciens infects plant roots and encourages tumour growth

incorporated gene activated + products formed

Question 5

how does electroporation work?

Answer 5

used when plant tissue does not contain cell walls

DNA enters the plant cell through miniature pores created by electric pulses

Question 6

what is the general formula of a monosaccharide?

Answer 6

C(x)H(2x)O(x)

Question 7

what are the two types of bonds found in glycogen? where specifically are they found and why?

Answer 7

a. 1,4-glycosidic bond - bonds within chains

a. 1,6-glycosidic bond -bonds between chains allowing branching

Question 8

how often does branching occur in glycogen molecules?

Answer 8

every 8 to 24 glucose molecules

Question 9

what are the differences between amylose and amylopectin?

Answer 9

amylose:

• helical polymer of a. glucose
• ~ 20-30% of starch
• insoluble
• hydrolysed slower

amylopectin:

• branched helical polymer of a. glucose
• ~ 70-80% of starch
• soluble
• hydrolysed faster

Question 10

outline some features of cellulose molecules

Answer 10

made from B. glucose

forms long fibrils

∴ has high tensile strength –> used in cell wall –> allows plant cell to become turgid

has inter- and intra-fibril H bonds

Question 11

outline some features of RuBisCO

Answer 11

has 16 ppc, 8 heavy and 8 light

requires Mg2+ (prosthetic group)

optimum pH 7.9

less specific active sites - can’t distinguish between CO(2) and O(2) - they are similar in size

Question 12

when does photorespiration occur? what are the consequences?

Answer 12

CO(2) concentration falls too low –> RuBisCO reacts with O(2) instead

carbohydrates are metabolised instead of created

Question 13

how do C4 and CAM plants cope with photorespiration?

Answer 13

bind CO(2) using a different enzyme - phosphoenolpyruvate carboxylase (PEPC)

which has a higher affinity for CO(2) than RuBisCCO ∴ can fix it with greater efficiency

∴ stomata can be opened for shorter periods of time

Question 14

what is the definition of carbon fixation?

Answer 14

the incorporation of inorganic carbon into organic compounds by living organisms

Question 15

what are carbon dioxide concentrating mechanisms (CCMs)?

Answer 15

found in algae + higher plants

used to overcome low CO(2) levels (e.g. in aqueous environment)

because CO(2) is slow to equilibrate between the air and water –> CO(2) depletion

∴ CCMs increase carboxylase activity

–> increased tolerance of low external concentrations of inorganic carbon + heat/water stress

Question 16

what are the three main components of algal CCM?

Answer 16

pyrenoid

series of transporters

series of carbonic anhydrases

Question 17

outline some features of cyanobacteria

Answer 17

a phylum of bacteria that obtain energy through photosynthesis

prokaryotes

can produce oxygen

can fix nitrogen in anaerobic conditions

have CCMs to obtain inorganic carbon

Question 18

what are carboxysomes?

Answer 18

a form of icosahedral bacterial micro-compartment

concentrate CO(2) inside by means of co-localised carbonic anhydrase activity (produced CO(2) from HCO(3)-)

avoids photorespiratory reactions

found in nitrobacter

Question 19

outline the features of carbonic anhydrase

Answer 19

globular protein with quaternary structure (Zn+ prosthetic)

Zn+ changes charge of a.s. –> easier for S to bind

∴ E(a) is reduced ∴ r.o.r. increases

reversible reaction

has 14 different isoforms in mammals

plans have B. carbonic anhydrase, which helps raise CO(2) concentration inside the chloroplast ∴ C activity of RuBisCO increases

Question 20

where is most of the RuBisCO in a chloroplast found?

Answer 20

in pyrenoids

Question 21

outline the features of Nicotiana tabacum

Answer 21

annually-grown herbaceous plant

commercially grown for processing into tobacco

Question 22

outline the features of Synechoccus elongatus

Answer 22

one circular chromosome and two plasmids

Gram -ve

freshwater photoautotroph that contributes significantly to primary production

Question 23

outline some of the effects of GM crops on ecosystems

Answer 23

possibly toxic to non-target organisms

cross-species transfer/contamination

evolution of superweeds

reduces competition and ∴ biodiversity

toxic soil ecosystems

eutrophication

Question 24

what is an invasive species?

Answer 24

a plant/fungus/animal that is not native to a specific location

has a tendency to spread to a degree that it causes damage to the environment

Question 25

what is a selective advantage?

Answer 25

a characteristic of an organisms that enables it to survive and reproduce better than other organisms in a population in a given environment