energy transfers in and between organisms 3.5

Question 1

what reaction occurs in the thylakoid?

Answer 1

light dependent reaction

Question 2

what reaction occurs in the stroma?

Answer 2

light independent reaction

Question 3

what are the four stages of LDR?

Answer 3

photolysis , photoionisation of chlorophyll, chemiosmosis and production of ATP and reduced NADP

Question 4

what happens in photolysis of water?

Answer 4

• light energy absorbed by chlorophyll splits water into oxygen electrons and H+ ions
• H+ ions picked up by NADP to form reduced NADP and used in LIR
• electrons pass along chain of electron carrier protein
• oxygen is either used for respiration or diffuses out of stomata

Question 5

what happens in photoionisation of chlorophyll?

Answer 5

• light energy absorbed by chlorophyll results in electrons becoming excited and raising an energy level to leave chlorophyll
• therefore chlorophyll ionised by light
• some of the energy released from electrons is used to make ATP and reduced NADP in chemiosmosis

Question 6

what happens in chemiosmosis?

Answer 6

• electrons that gained energy and left the chlorophyll move along a series of proteins embedded within the thylakoid membrane
• as they move along they release energy and some of this energy is used to pump protons across the chloroplast membrane (stroma to thylakoid membrane)
• an electrochemical gradient is created, the protons pass through the enzyme ATP synthase via facilitated diffusion resulting in the production of ATP (phosphorylation of ADP)
• the proton comes back to stroma which then combines with co enzyme NADP to form reduced NADP

Question 7

what enzyme is required in the Calvin cycle (LIR)?

Answer 7

RuBisCo

Question 8

what happens in the LIR?

Answer 8

• CO2 reacts with 5C RuBP to form two molecules of 3C GP this reaction is catalysed by RuBisCo
• GP is reduced to TP using ATP energy and by accepting a H from reduced NADP
• one carbon from TP leaves cycle to be converted to useful organic substances
• rest of TP is regenerated back to RuBP with the use of ATP

Question 9

what are the limiting factors of photosynthesis?

Answer 9

light intensity carbon dioxide and temperature

Question 10

what are plants in the ecosystem?

Answer 10

producers

Question 11

how can biomass be measured?

Answer 11

mass of carbon or dry mass of tissue remaining per given area

Question 12

what is gross primary production?

Answer 12

chemical energy store in plant biomass in a given area or volume (total energy resulting from photosynthesis)

Question 13

what is net primary production?

Answer 13

chemical energy store in plant biomass taking into account the energy that will be lost from respiration

Question 14

what is the equation between GPP NPP and respiration?

Answer 14

NPP = GPP - R

Question 15

what is NPP available for?

Answer 15

energy left over that is available for next trophic level to create new biomass and for plant growth/reproduction

Question 16

what is the net production of consumers equation?

Answer 16

N = I - (F + R)

Question 17

what does each letter stand for in N = I - (F + R)

Answer 17

N = net production of consumers
I = chemical energy store in ingested food
F = chemical energy lost to environment (faeces)
R = respiration loss

Question 18

what are rates of productivity units?

Answer 18

kJ unit area-1 year-1
(unit area can be ha,m etc)

Question 19

what does each symbol mean in the rates of productivity units?

Answer 19

kJ = units for energy
unit area to standardize the results so different areas can be compared
per year to take into account impact of each season provides average

Question 20

what happens in ammonification?

Answer 20

saprobionts break down organic matter to ammonia and hydrolyse conplex proteins into amino acids etc

Question 21

what are saprobionts?

Answer 21

bacteria and fungi that live on dead organisms and feed on them by extracellular digestion

Question 22

what happens in nitrification?

Answer 22

nitrifying bacteria convert ammonia to nitrite than nitrates

Question 23

what happens in denitrification?

Answer 23

when nitrate ions are converted into nitrogen gas by denitrifying bacteria

Question 24

what happens in nitrogen fixation?

Answer 24

when nitrogen gas is converted to ammonia ions which dissolve to form ammonium ions to make nitrogen useable by plants

Question 25

when does denitrification happen?

Answer 25

it wet areas with little oxygen (anaerobic areas)

Question 26

how to calculate efficient energy transfers

Answer 26

energy after transfer/energy before transfer x 100

Question 27

where is phosphorus released?

Answer 27

from sedimentary rocks as a result of weathering etc

Question 28

what is mycorrhizae?

Answer 28

fungi associated between plant roots and beneficial fungi

Question 29

why are mycorrhizae important?

Answer 29

• fungi increases surface area and mineral absorption
• hold water and ion around the roots
• makes plants drought resistant and able to take up more inorganic ion

Question 30

what is the relationship between plants and myccorhizae?

Answer 30

mutualistic

Question 31

why are fertilisers used?

Answer 31

to replace nitrates and phosphates lost in harvestation and removed from nutrient cycle

Question 32

name a natural fertiliser

Answer 32

animal manure

Question 33

name an artifical fertiliser

Answer 33

inorganic chemicals

Question 34

what are the pros and cons of natural fertiliser?

Answer 34

+ very cheap
- unable to control proportion

Question 35

what are the pros and cons of artifical fertiliser?

Answer 35

+ contain exact amounts of minerals
- very expensive
- very soluble so ions dissolve into surrounding waters of soil (impact of environment)

Question 36

what are the environmental impacts of artifical fertilisers?

Answer 36

leaching and eutrophication + reduced species diversity

Question 37

what is leaching?

Answer 37

when water soluble compounds are washed away into rivers and ponds etc

Question 38

what is eutrophication?

Answer 38

• nitrates leached into pond increase growth of algae
• blocks light and so therefore less photosynthesis so plants die
• saprobionts feed and respire aerobically from dead plants
• use up majority of water so not enough oxygen for fish and other organisms so they die