Bio - P2
5 – Energy transfers between
organisms
- Role of producers:
o Plants -> perform PS, use light energy to make bio molecules
- Role of consumers:
o Animals -> eat plants/other animals to get bio molecules
- Role of decomposers:
o Bacteria/fungi - > release enzymes onto dead plants to decompose them
- Energy is lost along a food chain bc of:
o Respiration, inedible parts and indigestible parts
o Higher consumers have higher respiratory losses as they have incr. movement for hunting food
- Productivity = amount of glucose. Energy available to organism
- Net productivity = gross productivity – respiratory (and faeces) losses
o Gross prod. = amount of glucose made by plants in PS
o Net prod. = amount of glucose stored as starch after respiration
- Biomass = mass of living tissue
- Adaptations of plant for PS
o Leaf near top of plant = closer to light
o Leaf tin and wide = large SA for light + short diffu. Distance
o Many veins = connect xylem to bring in water
o Has stomata = for gas exchange of CO2/O2
o Palisade cells have large vacuole = pushes chloroplast to edge of cell closer to light
- LDR
o Occurs in thylakoids
1. Chlorophyll absorbs light and e- becomes excited and are lost from chlorophyll (photoionisation)
2. E- enter ETC and move down it, releasing energy -> this pumps H+ from stroma into thylakoid space
3. H+ pass though ATP synthase which joins ADP + Pi to make ATP
4. E- joins w/ NADP to form red. NADP
5. Light also hits water -> causes photolysis and forms H+ + e- + O2
6. The H+ joins w/ red. NADP
7. E- replaces e- lost from chlorophyll
- LIR (aka Calvin cycle)
o Occurs in stroma
1. CO2 diffuses through stroma and joins w/ RuBP using rubisco enzyme -> makes 2x GP
2. 2x GP is reduced into 2x TP -> uses energy from ATP and H+ from red. NADP
3. Some TP used to regenerate RuBP using energy from ATP, and the rest is used to make organic
substances, e.g. glucose
- Effect of light intensity on PS
o Incr. LDR
o Causes stomata to open so CO2 can enter leaf -> incr. rate
- Effect of temp. on PS
o Incr. rate of enzyme-controlled reactions up to 25 °c
o Above 25 °c, rate falls due to enzymes not working efficiently -> may denature ATP synthase/rubisco
o Incr. temp = incr. rate of transpiration -> could lead to closure of stomata so reduced uptake of CO2 -
> decr. rate
- Effects of CO2 on PS:
o Incr. in CO2, incr. rate of LIR, up to 0.4%
- Aerobic respiration:
,Bio - P2
o Glycolysis (also happens in AN-R)
Occurs in cytoplasm
1. Glucose is phosphorylated using 2 phosphates from 2x ATP
2. Glucose phosphate is split into 2 triose-phosphate molecules, which are oxidised (loses H) to for
2x pyruvate
Produces 2x red. NAD + 2x ATP
o Link reaction:
Occurs in mitochondrial matrix
1. Pyruvate actively transported into mitochondrial matrix and is oxidised into acetate -> uses NAD
which is reduced to form red. NAD
2. Pyruvate decarboxylated to release CO2
3. Acetate combines w/ coenzyme A to for acetyl coenzyme A (acetyl CoA)
Produces 2x CO2 + 2x red. NAD
o Krebs cycle:
Occurs in mitochondrial matrix
1. Acetyl CoA combines w/ 4C ATP CO2 Reduce Reduce
molecules to form 6C molecule d NAD d FAD
2. 6C molecule is decarboxylated
X X
Glycolysi
and oxidised to 5c molecule, s 2 2
using H for NAD and produces
X X
Link
red. NAD reaction 2 2
3. 5C molecule is decarboxylated
Krebs
and oxidised into 4C molecule 2 4 6 2
cycle
again -> uses H from red. FAD
and red. NAD
Produces 4x CO2, 2x ATP, 6x red. NAD, 2x red. FAD
o Oxidative phosphorylation:
Occurs in cristae
1. H atoms produced in glycolysis and Krebs cycle combine w/ NAD and FAD to form red. NAD and
red. FAD
2. Red. NAD and FAD donate 2- of H atoms
3. E- pass along ETC, releasing energy, causing active transport of H+ ions across inner
mitochondrial membrane into intermembrane space
4. H+ gather together before they diffuse back into matrix through ATP synthase channels in inner
membrane on mitochondria
5. At end of chain, e- combine w. H+ and O2 to form water = ½ O2 + 2e- + 2H+ -> H2O
6. O2 is the final e- acceptor
- Anaerobic respiration:
o Pyruvate, from glycolysis, is reduced into lactate (in
animals) or ethanol (in plants)
- Nitrogen cycle:
o Nitrogen fixation -> nitrogen-fixing bacteria convert
nitrogen into ammonia -> forms ammonia ions which
plants use
o Ammonification -> nitrogen compounds from dead
organisms/waste products are converted to
ammonia by saprobionts
o Nitrification -> ammonium ions in soil are oxidised to nitrites and nitrates by nitrifying bacteria
, Bio - P2
o Denitrification -> nitrates in soil converted to nitrogen gas by denitrifying bacteria (anaerobic
conditions)
- Role of saprobionts ->
o Secrete enzymes externally onto dead organisms/waste products
o Breaks down bio molecules
o Absorb some of nutrients
- Role of mycorrhizae -> their hyphae connect to plant roots and incr. SA -> helps plant absorb more ions form
soil/take up more water
- Phosphorous cycle:
o Phosphorous in rocks slowly released into soil and into water sources in form of phosphate ions by
weathering
o Phosphate ions are taken up from soil by plants
o Phosphate ions are transferred to consumers during feeding
o Phosphate ions in waste products/dead organisms are released into soil/water during
decomposition by saprobionts
o Phosphate ions can now be taken up and used once again by producers or may be trapped in
sediment that may turn into phosphorous containing rock again
- Types of fertilisers:
o Natural fertilisers – consist of dead and decaying remains of plants and animals as well a animal
wastes such as manure, slurry and bone meal
o Artificial fertilisers – they are mined from rocks and deposits and then converted into different forms
and blended together to give appropriate balance of minerals for a particular crop. Compounds
containing the 3 elements, nitrogen, phosphorous and potassium are almost always present
- Eutrophication:
o Leaching
Fertilisers used to grow plants do into local rivers/lakes by rainfall due to groundwater that
runs off soil -> incr. nitrogen conc. of water
o Algal bloom
Incr. in nitrogen = faster growth of algae on water’s surface
Means limited light passes through due to it being absorbed by algae
o Limited light -> less light for plants at bottom means PS won’t happen -> plants won’t grow and die
o Saprobiotic bacteria (SB)
Decomposes dead plants
Pop. Of it grows -> uses dead organisms for food
o Aerobic respiration
SB uses O2 for respiration
Conc. of O2 reduced and nitrates are released from decaying organisms
o O2 conc.
O2 becomes limiting factor for organisms
Organisms dies due to lack of O2
Less O2 = less competition for anaerobic organisms which further decompose dead material,
releasing nitrates and some toxic wastes, making water putrid
5 – Energy transfers between
organisms
- Role of producers:
o Plants -> perform PS, use light energy to make bio molecules
- Role of consumers:
o Animals -> eat plants/other animals to get bio molecules
- Role of decomposers:
o Bacteria/fungi - > release enzymes onto dead plants to decompose them
- Energy is lost along a food chain bc of:
o Respiration, inedible parts and indigestible parts
o Higher consumers have higher respiratory losses as they have incr. movement for hunting food
- Productivity = amount of glucose. Energy available to organism
- Net productivity = gross productivity – respiratory (and faeces) losses
o Gross prod. = amount of glucose made by plants in PS
o Net prod. = amount of glucose stored as starch after respiration
- Biomass = mass of living tissue
- Adaptations of plant for PS
o Leaf near top of plant = closer to light
o Leaf tin and wide = large SA for light + short diffu. Distance
o Many veins = connect xylem to bring in water
o Has stomata = for gas exchange of CO2/O2
o Palisade cells have large vacuole = pushes chloroplast to edge of cell closer to light
- LDR
o Occurs in thylakoids
1. Chlorophyll absorbs light and e- becomes excited and are lost from chlorophyll (photoionisation)
2. E- enter ETC and move down it, releasing energy -> this pumps H+ from stroma into thylakoid space
3. H+ pass though ATP synthase which joins ADP + Pi to make ATP
4. E- joins w/ NADP to form red. NADP
5. Light also hits water -> causes photolysis and forms H+ + e- + O2
6. The H+ joins w/ red. NADP
7. E- replaces e- lost from chlorophyll
- LIR (aka Calvin cycle)
o Occurs in stroma
1. CO2 diffuses through stroma and joins w/ RuBP using rubisco enzyme -> makes 2x GP
2. 2x GP is reduced into 2x TP -> uses energy from ATP and H+ from red. NADP
3. Some TP used to regenerate RuBP using energy from ATP, and the rest is used to make organic
substances, e.g. glucose
- Effect of light intensity on PS
o Incr. LDR
o Causes stomata to open so CO2 can enter leaf -> incr. rate
- Effect of temp. on PS
o Incr. rate of enzyme-controlled reactions up to 25 °c
o Above 25 °c, rate falls due to enzymes not working efficiently -> may denature ATP synthase/rubisco
o Incr. temp = incr. rate of transpiration -> could lead to closure of stomata so reduced uptake of CO2 -
> decr. rate
- Effects of CO2 on PS:
o Incr. in CO2, incr. rate of LIR, up to 0.4%
- Aerobic respiration:
,Bio - P2
o Glycolysis (also happens in AN-R)
Occurs in cytoplasm
1. Glucose is phosphorylated using 2 phosphates from 2x ATP
2. Glucose phosphate is split into 2 triose-phosphate molecules, which are oxidised (loses H) to for
2x pyruvate
Produces 2x red. NAD + 2x ATP
o Link reaction:
Occurs in mitochondrial matrix
1. Pyruvate actively transported into mitochondrial matrix and is oxidised into acetate -> uses NAD
which is reduced to form red. NAD
2. Pyruvate decarboxylated to release CO2
3. Acetate combines w/ coenzyme A to for acetyl coenzyme A (acetyl CoA)
Produces 2x CO2 + 2x red. NAD
o Krebs cycle:
Occurs in mitochondrial matrix
1. Acetyl CoA combines w/ 4C ATP CO2 Reduce Reduce
molecules to form 6C molecule d NAD d FAD
2. 6C molecule is decarboxylated
X X
Glycolysi
and oxidised to 5c molecule, s 2 2
using H for NAD and produces
X X
Link
red. NAD reaction 2 2
3. 5C molecule is decarboxylated
Krebs
and oxidised into 4C molecule 2 4 6 2
cycle
again -> uses H from red. FAD
and red. NAD
Produces 4x CO2, 2x ATP, 6x red. NAD, 2x red. FAD
o Oxidative phosphorylation:
Occurs in cristae
1. H atoms produced in glycolysis and Krebs cycle combine w/ NAD and FAD to form red. NAD and
red. FAD
2. Red. NAD and FAD donate 2- of H atoms
3. E- pass along ETC, releasing energy, causing active transport of H+ ions across inner
mitochondrial membrane into intermembrane space
4. H+ gather together before they diffuse back into matrix through ATP synthase channels in inner
membrane on mitochondria
5. At end of chain, e- combine w. H+ and O2 to form water = ½ O2 + 2e- + 2H+ -> H2O
6. O2 is the final e- acceptor
- Anaerobic respiration:
o Pyruvate, from glycolysis, is reduced into lactate (in
animals) or ethanol (in plants)
- Nitrogen cycle:
o Nitrogen fixation -> nitrogen-fixing bacteria convert
nitrogen into ammonia -> forms ammonia ions which
plants use
o Ammonification -> nitrogen compounds from dead
organisms/waste products are converted to
ammonia by saprobionts
o Nitrification -> ammonium ions in soil are oxidised to nitrites and nitrates by nitrifying bacteria
, Bio - P2
o Denitrification -> nitrates in soil converted to nitrogen gas by denitrifying bacteria (anaerobic
conditions)
- Role of saprobionts ->
o Secrete enzymes externally onto dead organisms/waste products
o Breaks down bio molecules
o Absorb some of nutrients
- Role of mycorrhizae -> their hyphae connect to plant roots and incr. SA -> helps plant absorb more ions form
soil/take up more water
- Phosphorous cycle:
o Phosphorous in rocks slowly released into soil and into water sources in form of phosphate ions by
weathering
o Phosphate ions are taken up from soil by plants
o Phosphate ions are transferred to consumers during feeding
o Phosphate ions in waste products/dead organisms are released into soil/water during
decomposition by saprobionts
o Phosphate ions can now be taken up and used once again by producers or may be trapped in
sediment that may turn into phosphorous containing rock again
- Types of fertilisers:
o Natural fertilisers – consist of dead and decaying remains of plants and animals as well a animal
wastes such as manure, slurry and bone meal
o Artificial fertilisers – they are mined from rocks and deposits and then converted into different forms
and blended together to give appropriate balance of minerals for a particular crop. Compounds
containing the 3 elements, nitrogen, phosphorous and potassium are almost always present
- Eutrophication:
o Leaching
Fertilisers used to grow plants do into local rivers/lakes by rainfall due to groundwater that
runs off soil -> incr. nitrogen conc. of water
o Algal bloom
Incr. in nitrogen = faster growth of algae on water’s surface
Means limited light passes through due to it being absorbed by algae
o Limited light -> less light for plants at bottom means PS won’t happen -> plants won’t grow and die
o Saprobiotic bacteria (SB)
Decomposes dead plants
Pop. Of it grows -> uses dead organisms for food
o Aerobic respiration
SB uses O2 for respiration
Conc. of O2 reduced and nitrates are released from decaying organisms
o O2 conc.
O2 becomes limiting factor for organisms
Organisms dies due to lack of O2
Less O2 = less competition for anaerobic organisms which further decompose dead material,
releasing nitrates and some toxic wastes, making water putrid
