topic 5

Question 1

where does light dependant reaction happen

Answer 1

thylakoid memb of chloroplast

Question 2

light independant reaction

Answer 2

stroma of chloroplast

Question 3

light dependant reaction

Answer 3

photoisonisation - chlorophyll absorb light energy which excites electrons to a higher energy level
so electrons released from chlorophyll and chlorophyll becomes postively charged.
after photoionisation so energy from photoionisation conserved for production of atp and reduced nadp
electrons move along etc releasing energy to actively pump protons from stroma to thylakoid
protons move by FD down electrochem gradient via ATP synthase
energy used to join adp and pi to form atp
nadp accepts a proton and an electron to form reduced NADP
water splits to produce protons electrons and oxygen so electrons replace those lost from chlorophyll

Question 4

light independent reaction

Answer 4

co2 reacts with rubp which is catalysed by rubisco
forming two G3P which is reduced to triose phosphate
using products from LDR - the reduced NADP and energy from ATP
some TP converted to useful organic substances
some TP used to regen RuBP using energy from ATP

Question 5

temps affect on photosynthesis

Answer 5

incr temp, incr rate as they gain more kinetic energy so more E-S complexes

Question 6

light intensity affect on photosynthesis

Answer 6

light intensity increases the rate increases
LDR increases so more ATP and reduced NADP produced
light independant reaction increases as more GP reduced to TP and more TP regen RUBP

Question 7

co2 conc affect on photosynthesis

Answer 7

co2 conc increase, the rate increases so light independant reaction increases as more co2 combines with RuBP to form GP and more GP is reduced to TP so more organic substances and rubp regenerated

Question 8

respiration

Answer 8

produces ATP to release energy for active transport and protein synthesis

Question 9

glycolysis

Answer 9

glucose phosphorylated to glucose phosphate using inorganic phosphates from 2 ATP
hydrolysed to 2 triose phosphate which is oxidised to 2 pyruvate
2 NAD reduced
4 ATP generated

Question 10

what happens after glycolysis if anaerobic respiration

Answer 10

pyruvate converted to lactate or ethanol
oxidising reduced NAD so NAD regenerated
so glyoclysis continue allowing continued production of ATP

Question 11

suggest why anaerobic respiration produces less ATP per molec of glucose

Answer 11

only glycolysis involved which produces little ATP
no oxidative phosphorylation which forms majority of ATP

Question 12

link reaction

Answer 12

pyruvate oxidised to acetate
co2 produced and reduced NAD produced
acetate combines with co enzyme A forming acetyl coenzyme A

Question 13

krebs cycle

Answer 13

acetyl co enzyme A reacts with a 4c molecule releasing coenzyme A and producing a 6C molecule which enters the krebs cycle
in a series oxidation reduction reactions and the 4c molecule is regenerated and 2 co2 is lost and coenzymes NAD FAD reduced
substrate level phosphorlyation
and atp is produced

Question 14

The products per glucose molecule of Krebs cycle

Answer 14

6 reduced NAD 2reduced FAD 2 ATP and 4 CO2

Question 15

Oxidative phosphorylation

Answer 15

Reduced NAD and FAD oxidised to release H plus atoms which split into protons and electrons
Electrons transferred down ETC by redox reactions
Energy released by electrons used in the production of ATP from ADP PI and this energy is used to AT protons from the matrix to the inter membrane space
Protons diffuse into matrix down electrochemical gradient via ATP synthase releasing energy to synthesise atp from adp plus pi
In matrix at the end of ETC oxygen is the final electron acceptor so protons electrons and oxygen combine to form water

Question 16

How is biomass formed in plants

Answer 16

During photosynthesis plants make organic compounds from atmospheric or aquatic co2
Most sugars synthesised are used by plant as respiratory substrates
Rest used to make other groups of biological molecules

Question 17

How is biomass measured

Answer 17

Mass of carbon or dry mass of tissue per given area

Question 18

How can dry mass of tissue be measured

Answer 18

Sample dried I’m oven at eg 100c
Sample weighed and reheated at regular intervals until it remains constant

Question 19

How can the chemical energy stored in dry biomass be measured

Answer 19

Using calorimetry
Known mass of dry biomass fully combusted and the heat energy released heats a known volume of water
Increase in temp of water used to calculate the chemical energy of biomass

Question 20

Gross primary production

Answer 20

Chemical energy stored in plant biomass in a given area and volume and time
Total energy transferred into chemical energy from light energy during photosynthesis

Question 21

Net primary production

Answer 21

Chemical energy store In plant biomass after respiratory losses to envi taken into account

Question 22

Importance of npp in ecosystems

Answer 22

Npp is available for plant growth and reproduction
Also available to other trophic levels In ecosystem like herbivores and decomposers

Question 23

Why is the most the light that falls on producers not used for photosynthesis

Answer 23

Light reflected or wrong wavelength
Light misses chlorophyll
Co2 conc or temp is a limiting factor

Question 24

Formula for net production of consumers

Answer 24

N-I-(F+R)
I is the chemical energy stored in ingested food
F is the chemical energy lost to environment in faeces and urine

Question 25

Why is energy transfer between organisms inefficient

Answer 25

heat energy lost via respiration
Energy lost as part of organisms that aren’t eaten
Energy lost via food not digested lost as faeces
Energy lost via excretion

Question 26

How do crop farming practices increase efficiency of energy transfer

Answer 26

Simplifying food webs to reduce energy losses
Herbicides to kill weeds so less competition
Pesticides to kill insects and reduce loss of biomass from crops
Fungicides to reduce fungal infections so more energy to create biomass
Fertilisers to prevent poor growth due to lack of nutrients

Question 27

Livestock farming practice to increase efficiency of energy transfer

Answer 27

Restrict movement and keep warm so less energy lost as heat from Respiration
Slaughter animals whilst young and growing when most energy is used for growth
Treat with antibiotics to prevent energy loss due to pathogens
Selective breeding to produce breeds with higher growth rates

Question 28

Saprobionts Role In recycling chemical elements

Answer 28

Decompose organic compounds by secreting enzymes for extra cellular digestion
Absorb soluble needed nutrients and release mineral ions like phosphate

Question 29

Mycorrhizae

Answer 29

The symbiotic association between fungi and plant roots
Fungi act as extension of plant roots to increase surface area of root system
To increase rate of uptake and absorption of water and inorganic ions and In return fungi receives organic compounds

Question 30

Role of bacteria in nitrogen fixation

Answer 30

Nitrogen gas is converted to ammonia which forms ammonium ions in soil by nitrogen fixating bacteria

Question 31

Role of bacteria in ammonification

Answer 31

Nitrogen containing compounds like protiens from dead organisms are broken down
Converted to ammonia which form ammonium ions in soil
By Saprobionts which secrete enzymes for extra cellular digestion

Question 32

Role of bacteria in nitrification

Answer 32

Ammonium ions In soil converted to nitriles then nitrates via a two step oxidation
For uptake by plant root hair cells by active transport
By nitrifying bacteria in aerobic conditions

Question 33

Bacteria in dentrification

Answer 33

Nitrates I’m soil converted to nitrogen gas
By dentrifying bacteria I’m anaerobic conditions

Question 34

Ploughing increases soil fertility

Answer 34

More ammonium converted into nitrile and nitrate so more nitrfication
Less denitrification and less nitrate converted to nitrogen gas

Question 35

Phosphorus cycle

Answer 35

Phosphate ions in rocks released by erosion and weathering
Phosphate ions Taken up by producers plant and algae and incorporated into their biomass
Rate of absorption increased by mycrohizzae
Phosphate ions transferred through food chain
Some phosphate ions lost from animals as waste products
Saprobionts decompose organic compounds releasing phosphate ions

Question 36

Why are fertilisers used

Answer 36

Replace nitrates and phosphates lost when plants are harvested and livestock are removed
Those removed from soil are incorporated into biomass which can’t be released back into the soil through decomposition by Saprobionts
So improve efficiency of energy transfer

Question 37

Natural fertilisers

Answer 37

Organic like manure and compost ions released during decomposition by Saprobionts

Question 38

Artificial fertilisers

Answer 38

Contain inorganic compounds of nitrogen phosphorus and potassium

Question 39

Envi issues of using fertilisers

Answer 39

Phosphates and nitrates dissolve in water leading to leaching of nutrients into lakes rivers ocean
Leading to eutrophication
Rapid growth of algae in pond so algal bloom and light is blocked
So submerged plants die as can’t photosynthesise
So Saprobionts decompose dead plant matter using oxygen in aerobic respiration
So less oxygen for fish to aerobically respire leading to death

Question 40

Advantage of using natural fertiliser over artificial

Answer 40

Less water soluble so less leaching and eutrophication less likely
Organic molecules require breaking down by Saprobionts slow release of nitrate and phosphate