5 - Photosynthesis, Respiration, Cycles Flashcards
Where does the light dependant reaction in photosynthesis occur?
Thylakoids membrane in chloroplast
(Production of ATP)
- chlorophyll absorbs light and electrons are lost
Where does the light independant reaction in photosynthesis occur?
In stroma in chloroplast
What is the role of light in photoionisation
chlorophyll absorbs light energy (photon) which excites electrons to a higher energy level, releasing them from chlorophyll
What are the 2 main stages involved in ATP production in the LDR
- Electron transfer chain
- Chemiosmosis
Describe production of ATP in the LDR part 1) What happens in the electron transfer chain
1 - electrons pass down the chain from PSII to PSI via redox reactions, losing energy at each step
2 - this energy is used to actively transport protons from stroma into thylakoid
3 - which creates a electrochemical gradient across the thylakoid membrane
Describe production of ATP in the LDR part 2)
4 - protons move by facilitated diffusion down the electrochemical gradient into the stroma via ATP synthase embedded in the thylakoid membrane
5- energy from this allows ADP + Pi—> ATP (chemiosmotic theory)
LDR part 3)
Describe production of NADPH
In PSI electrons are excited and transferred to NADP (with a proton from photolysis) to reduce NADP and form NADPH
LDR part 4) Describe photolysis
- Splitting of water using light energy produces protons, electrons and oxygen (2H20 -> O2 + 4e + 4H+)
- electrons replace those lost from chlorophyll
What are the products of the LDR
- ATP
- reduced NADP
- oxygen
What are the 3 stages of the Calvin cycle (LIR)
- Carbon fixation
- Reduction
- Regeneration
Describe carbon fixation in the Calvin cycle (1)
- CO2 reacts with RuBP, catalysed by the enzyme rubisco
- this produces 2 molecules of (GP) (3C)
Describe reduction in the Calvin cycle (2)
- GP is reduced to TP using products from the LDR:
- energy from the hydrolysis of ATP and H+ from reduced NADP
- some TP is converted into useful organic substances eg glucose
Describe regeneration in the Calvin cycle (3)
- (5/6) TP is used to regenerate RuBP (using rest of ATP)
How does temperature effect the rate of photosynthesis
Increased temp up to the optimum - more E-S complexes (rubisco) and more kinetic energy
Above optimum - H bonds in tertiary structure break so active site changes shape. Rubisco denatures so fewer E-S complexes
- it limits the light independent reaction as it is enzyme controlled (rubisco)
How would dramatically reduced light intensity effect the rate of photosynthesis
Levels of ATP and reduced NADP would fall because:
- LDR is limited as less photoionisation of chlorophyll and photolysis
so LIR also slows because:
- GP cant be reduced to TP (requires ATP and reduced NADP)
- TP can’t regenerate RuBP (requires ATP)
How would dramatically reduced CO2 conc effect the rate of photosynthesis
LIR limited because:
- less CO2 to combine with RuBP to form GP
- less GP reduced to TP
- less TP and GP converted to organic substances eg to regenerate RuBP
How could you maximise light intensity for photosynthesis
Growing plants under artificial lighting
How could you increase temperature for photosynthesis
By heating a greenhouse
How could you increase CO2 conc for photosynthesis
Burning fuel eg paraffin burners
What is the effect on photosynthesis of limiting factors being only minimal
Rate of photosynthesis will increase because:
- faster production of glucose so faster respiration
- more ATP to provide energy for growth eg cell division, protein synthesis
- higher yield so more profit
Which chemicals are needed for the LDR
NADP
ADP
Pi
Water
What’s the advantage of having different coloured pigments in leaves
Absorb more wavelength’s of light for photosynthesis
Where is rubisco found in a cell
Stroma
What are the two molecules produced in the LDR which are needed for the LIR/Calvin cycle
ATP
NADPH
Where does glycolysis occur
- cytoplasm
- anaerobic process
Describe glycolysis
Occurs in cytoplasm
1) phosphorylation of glucose to GP using the inorganic phosphates from 2 ATP
2) hydrolysed to 2 x triose phosphate (TP)
3) 2x TP is oxidised 2x pyruvate
. 2 NAD is reduced
. 4 ATP regenerated
4) net production of 2 ATP
What happens after glycolysis if no oxygen present (anaerobic respiration)
1) pyruvate reduced to lactate (animals) or ethanol (plants/yeast)
2) oxidising reduced NAD -> NAD regenerated
3) so glycolysis can continue which uses NAD
Some energy is still in lactate (incomplete breakdown of glucose)
Why is anaerobic respiration less efficient than aerobic
- the ATP yield is lower
- majority of ATP is formed in oxidative phosphorylation
What happens after glycolysis if oxygen is present (aerobic respiration)
1) pyruvate is actively transported into mitochondrial matrix
2) the 4 stages of aerobic respiration occur
What are the 4 stages of aerobic respiration
- Glycolysis
- Link reaction
- Krebs cycle
- Oxidative phosphorylation
Describe aerobic respiration stage 2:
Link reaction
1 - occurs in mitochondrial matrix
2 - pyruvate is oxidised and decarboxylated to form acetate
. CO2 and NADH produced
3. Acetate combines with coenzyme A to form Acetyl Coenzyme A (CoA)
4. Per glucose molecule, 2x Acetyle CoA, 2x CO2, and 2x NADH produced
Describe aerobic respiration stage 3:
Krebs cycle (1-3)
1 ) occurs in mitochondrial matrix
2) Acetyl CoA reacts with a 4-carbon molecule, producing a 6-carbon molecule that enters the Krebs cycle. (CoA is released)
3) - 4C molecule is regenerated through a series of redox reactions.
Describe aerobic respiration stage 3:
Krebs cycle (4-5)
4) Decarboxylation and dehydrogenation occurs
. CO2 is removed
. Coenzymes NAD AND FAD reduced (important for oxidative phosphorylation) into NADH and FADH2
5) ATP produced by substrate level phosphorylation
Describe aerobic respiration stage 4:
Oxidative phosphorylation (1-3)
1) occurs on the Cristae of mitochondria
2) reduced NAD/FAD oxidised to release H atoms split into protons and electrons (e-)
3) e- transferred down the electron transport chain by redox reactions
Describe aerobic respiration stage 4:
Oxidative phosphorylation (4 - chemiosmotic theory)
4) energy released by electrons moving along the chain is used to make ATP from ADP +Pi (chemiosmotic theory)
- Energy used to actively transport protons from matrix to the inter membrane space
- Electrons At the end of the chain react with O2 and H+ to make water. Which is why Oxygen is the final electron acceptor
. Protons diffuse down via ATP synthase back into the matrix
. Releasing energy to produce ATP
Why is oxygen needed for the production of ATP on the cristae of the mitochondria
- O2 is the terminal electron acceptor for electrons passing along the ETC
- the ETC releases energy for the formation of most ATP
- if no O2 to accept them then e- cannot be passed along the e- transport chain
Why is oxygen needed for the Krebs cycle and link reaction
- NAD and FAD cannot be produced
What are some other respiratory substrates
breakdown products of lipids and amino acids, which enter the Krebs cycle
Why is high carbon has efficiency an advantage for an organism
- low respiration
- more growth
Describe the role of saprobionts in the nitrogen cycle
- they secrete enzymes to decompose proteins (extracellular digestion)
- producing ammonium ions
Give one way an increase in phosphate uptake in a plant could increase growth
Used to produce DNA
Describe the role of mycorrhizae
- symbiotic relationship between fungi and roots of plants
- mutualistic relationship
- increases SA and rate of absorption of water/nutrients
Describe ammonification (3)
- nitrogen containing compounds from animal waste are broken down by saprobionts into ammonia which gets converted into ammonium ions
Describe nitrification (2)
- ammonium ions in the soil -> nitrites -> nitrates
- by nitrifying bacteria.
- using O2
Why do farmers aerate their soil
- to increase O2 which allows number of nitrifying bacteria to increase and denitrifying bacteria to decrease
- this maximises nitrogen availability
Describe denitrification (4)
- nitrates in the soil -> nitrogen gas
- by denitrifying bacteria (anaerobically respire)
Describe nitrogen fixation (1)
- nitrogen gas in air is converted into ammonia and then ammonium ions
- by nitrogen fixing bacteria
- can be in foot nodules of plants eg legumes
Why is the nitrogen cycle important
- nitrogen gas is unreactive and not easily converted to other compounds
- most plants can only take up nitrogen as nitrate
- used by plants to make proteins/nucleic acids for growth
Why are fertilisers needed
- replaces nutrients lost from an ecosystem when crops are harvested or livestock is removed
- improve effiency of energy transfer to increase productivity of the land
What are the features of natural fertilisers
- organic
- eg manure, compost
- cheaper/free
- but exact nutrients cannot be controlled
What are the features of artificial fertilisers
- inorganic
- contain pure chemical
- inorganic substances more water soluble so larger quantities washed away which harms the environment
What is eutrophication
- rapid growth of algae in water
- algae blocks light so it can’t reach plants below
- plants die bc they can’t photosynthesise
- aerobically respiring saprobionts decompose the dead plants, reducing o2 concentration in water
- death of fish as no o2 left to respire
What are stages 1-2 in the phosphorus cycle
- phosphate ions in rocks released by erosion
- then taken into plants and incorporated into their biomass
- DNA, RNA, phospholipids
- rate of absorption increased by mycorrhizae
What are stages 3-4 in the phosphorus cycle
- phosphate ions transferred through food chain
- some lost from animals in waste products and plants and animals die
- decomposed by saprobionts
- release phosphate ions into the soil
What are photoautotrophs
Use light energy to synthesis their own food
What are chemoautotrophs
Use inorganic molecules to synthesis their food
What are heterotrophs
Cannot synthesis their own energy but obtain it from autotrophs or other heterotrophs
- they act as consumers in food webs
What are the two ways biomass can be measured
- Mass of carbon
- dry mass of tissue per given area
What is gross primary production (GPP)
Total energy resulting from photosynthesis
What is net primary production (NPP)
NPP = GPP - R (respiratory losses)
How do you work out net production of consumers
N = I - (F+R)
I = energy store in digested food
F = energy lost in faeces and urine
R = respiratory losses
What are some reasons for energy loss between trophic levels (sun to producer)
- wrong wavelength of light
- light strikes non-photosynthetic region
- light reflected
- lost as heat
What are some reasons for energy loss between trophic levels (producer to consumer)
- respiratory loss (energy used for metabolism
- lost as heat
- not all parts eaten eg bones
- some food not digested eg faeces
How could you increase energy transfer via livestock
Reduce respiratory losses by:
- restrict movement
- keep warm
- slaughter animal while still young
How could you increase energy transfer via crops
Simplify food webs:
- herbicides
- fungicides
- pesticides
Why is DCPIP used in the photosynthesis experiment
As a control to show that light does not effect it
What are the names of the two types nitrogen fixing bacteria
- free living: Azotobacter
- Mutualistic: Rhizobium
What are the names of the two types nitrifying bacteria
Converts ammonium ions to nitrite: Nitrosomonas
Converts nitrite to nitrate: Nitrobacter
What adaption of mitochondria allows them to produce a large amount of ATP
- their cristae have a large surface area for oxidative phosphorylation
