3.5 energy transfers in and between organisms

Question 1

what is the photosynthesis equation and where does photosynthesis occur

Answer 1

6CO2+ 6H2O → C6H12O6+ 6O2
Carbon Dioxide + Water -> Glucose + Oxygen
Occurs in the stroma and the thylakoid/grana
Light-dependent occurs in the grana
Light-independent occurs in the stroma.

Question 2

what is needed and made in the light dependent reaction

Answer 2

needed

• ADP + Pi
• NADP

made
ATP
reduced NADP
electron from chlorophyll

Question 3

what is the light dependent reaction

Answer 3

during photoionisation, light absorbed by the photo-systems causes the excitation of electrons which leads to ionisation
this is passed down the electron transport chain and the energy it produces is harnessed to synthesis ATP.
light splits water in photolysis. this produces hydrogen ions, oxygen and electrons. the electrons produced are used to reduced NADP

Question 4

what is the light independent reaction

Answer 4

Fixation
CO2 enters leaf through stomata. RuBP reacts with it. 6C into 2 3C compounds of glycerate 3-phosphate. Broken down via rubisco
2. Reduction
breaks down glycerate 3-phosphate into triose phosphate. H+ ions come from reduced NADP from light dependent reaction. NADP is recycled. TP is converted into compounds e.g. Glucose.
3. Regeneration
5/6 molecules of TP produced are used to regenerate RuBP. Rest of ATP produced in light-dependent is used

Question 5

what is the phosphorylation stage of glycolysis

Answer 5

Phosphorylation- glucose is phosphorylated to glucose phosphate using 1 molecule
of ATP. Glucose phosphate is phosphorylated by another molecule of ATP to hexose
bisphosphate.

Question 6

what is the splitting stage of glycolysis

Answer 6

Hexose bisphosphate splits into 2 molecules of triose phosphate

Question 7

what is the oxidation stage of glycolysis

Answer 7

oxidation- the 2 molecules of triose phosphate are oxidised to pyruvate in a
multi-step reaction. A single triose phosphate produces 2 molecules of ATP and 1
molecule of reduced NAD

Question 8

respiration and the link reaction

Answer 8

Start- pyruvate (3 carbon)
Step 1- pyruvate decarboxylase removes a carboxyl group forming CO2.
Step 2- Pyruvate dehydrogenase removes hydrogen atoms from the pyruvate. Hydrogen atoms are accepted by NAD which is reduced to form reduced NAD and acetate (2 carbon)
Coenzyme A (COA) accepts acetate to form acetyl coenzyme A (carries acetate into Krebs cycle)

Question 9

respiration and the krebs cycle

Answer 9

Takes place in mitochondrial matrix.
Step 1- coenzyme A releases acetate group. Acetate (2C) is joined to oxaloacetate (4C) and makes a 6C compound called citrate.
Step 2A- decarboxylation of citrate. Carboxyl group is removed from citrate and produces 1 CO2 and 1 5C compound (ketoglutarate)
Step 2B- oxidation of citrate. Dehydrogenation action of citrate. Hydrogen atoms removed by dehydrogenase enzymes, hydrogen accepted by NAD which is reduced.
Step 3A- ketoglutarate (5C) is oxidised to succinyl (4C). decarboxylation of ketoglutarate is oxidised to succinyl (4C). dehydrogenation of ketoglutarate. Hydrogen atoms removed by dehydrogenase enzymes. Hydrogen is accepted by NAD which is reduced.
Step 4- succinyl converted to succinate (4C). succinyl is converted to succinate (4C). energy is released by this step and is directly
used in a condensation reaction to form ATP.
Step 5- Succinate is oxidised to fumarate (4C). dehydrogenation of succinate. Hydrogen atoms is removed by dehydrogenase
enzymes. Hydrogen accepted by FAD which is reduced.
Step 6- Malatale (4C) oxidised to oxaloacetate (4C). dehydrogenation of malatate. Hydrogen removed by dehydrogenase
enzymes. Hydrogen accepted by NAD+ which is reduced.

Question 10

respiration

Answer 10

Glycolysis
C6H12O6 + 6O2 → 6CO2 + 6H20
Glycolysis is an anaerobic process and takes place in the cytoplasm. 

Link reaction 
Takes place in the mitochondria. 
Active transport moves pyruvates into the matrix. (pyruvates are polar) 
Connects glycolysis to the Krebs cycle. 

Krebs cycle 
Takes place in mitochondrial matrix

Question 11

light information

Answer 11

Over 90% of sun energy is reflected backed into space.
Not all wavelengths of light can be absorbed and used for photosynthesis
Light may not fall onto a chlorophyll molecule.

Question 12

what is gross production

Answer 12

the total quantity of energy the plants in a community convert to organic mass.

Question 13

what is biomass

Answer 13

Biomass is the total dry mass, excluding any water, of all organisms in a given area

Question 14

what is net productivity equation and definition

Answer 14

Plants use 20-25% of energy as respiration, leaving little to be stored. The rate at which they store energy is the net production
Net production= gross production- respiratory loss.

Question 15

what is gross production

Answer 15

Gross production- energy store in a given area or volume

Question 16

what is gross productivity

Answer 16

Gross productivity- rate of production

Question 17

net primary productivity

Answer 17

Is the chemical energy store available to plants after accounting for respiratory losses
NPP = GPP – R
GPP= gross primary production
R= respiration

Question 18

net consumer (or secondary) productivity

Answer 18

Is the chemical energy store available to animals
NSP = I – ( F + R )
I- energy ingested in food ( accounts for all food)
F- energy lost to the environment in faeces and urine
R- energy lost in respiration

Question 19

nitrogen cycles

Answer 19

Plants must secure their nitrogen in ‘fixed’ forms
i.e. incorporated in compounds such as:
Nitrate ions
Ammonia / ammonium
Animals secure their nitrogen from plants,

4 biological processes participate in the cycling of nitrogen in the biosphere 
 nitrogen fixation 
Decomposition 
Nitrification 
Denitrification

Question 20

mycorrhizae

Answer 20

Mycorrhizae live in association with roots of plants
Some plants live in close association with fungi
The fungi extend the roots, greatly increasing the surface area and therefore increasing absorption
The fungi gain access to carbohydrates

Question 21

nutrient cycles

Answer 21

Phosphorus- DNA
- ATP
- glycolysis
- phospholipid bilayer
Nitrogen- bases
- proteins- amine group in amino acids

Question 22

fertilisers

Answer 22

Replaces nutrients ( nitrates and phosphates) lost from an ecosystem’s nutrient cycle when:
Crops are harvested/ livestock removed
Nutrients that they have removed from the soil and incorporated into their biomass cant be released back into the soil through decomposition by saprobionts.
Improves the efficiency of energy transfer
Nutrient can no longer be a limiting factor
Increase productivity of agricultural land

Question 23

what are artificial fertilisers

Answer 23

Artificial fertilisers - inorganic

- contains pure chemicals (e.g. ammonium nitrate) as powder or pellets.

Question 24

what are natural fertilisers

Answer 24

Natural fertilisers - organic

- e.g. manure/ compost

Question 25

artificial fertilisers AO3

Answer 25

High concentrations can cause osmotic damage
Expensive
Uses light machinery
Exact composition is known
Easy to store/handle
Inorganic ions are readily soluble and can easily leach into waterways

Question 26

natural fertilisers AO3

Answer 26

Must 1st be decomposed and so release is slower and more controlled 
More controlled 
cheap
Less likely to cause leaching
May contain pathogens 
Uses heavy machinery

Question 27

environmental impact of fertilisers

Answer 27

Leaching
Rain/irrigation systems washes the water soluble compounds out of the soil into waterways
Particularly when more fertiliser is added to the field than used
Leads to eutrophication
Leaching is less likely to happen with natural fertilisers.
Nitrogen and phosphorous contained inorganic molecules which are less soluble in water and so need to be decomposed by saprobionts before nitrogen and phosphorous are released.
Can reduce species diversity

Question 28

eutrophication

Answer 28

Mineral ions leached from fertilised fields
Causes rapid growth of algae in ponds and rivers (algal bloom)
Algae blocks light, preventing it from reaching plants below.
Death of plants below as they cannot photosynthesise
Aerobically respiring saprobionts decompose the dead plant matter, reducing oxygen concentration of water
Leads to the death of aquatic organisms due to a lack of dissolved oxygen for aerobic respiration