Energy transfers in and between organisms Flashcards
(20 cards)
Describe the factors that affect rate of photosynthesis
Carbon dioxide
Light
Temperature (for enzymes)
In commercial greenhouses, we control these factors to an optimum to maximise yield potential
Describe the parts of the light independent stage of photosynthesis
- Carbon dioxide reacts with ribulose bisphosphate (RuBP) to form two molecules of GP - this reaction is catalysed by the enzyme rubisco
- ATP and reduced NADP from the light-dependent reaction are used to reduce GP to triose phosphate
- Some of the triose phosphate is used to regenerate RuBP in the Calvin cycle
- Some of the triose phosphate is converted to useful organic substances
Describe how the light dependent stage aids the light independent stage
Uses reduced NADP from the light dependent reaction to form a simple sugars
The hydrolysis of ATP provides the additional energy for this reaction
Describe the chemiosmotic theory
- Energy transferred during ETC is used to actively pump protons from the stroma into the thylakoid
- A proton gradient is established and protons then diffuse down their concentration gradient into the stroma via the enzyme ATP synthase
- The energy transferred by the movement of protons is used to phosphorylate ADP to form ATP
Describe the parts of the light dependent stage of photosynthesis
- Chlorophyll absorbs light energy which leads to the photoionisation of chlorophyll in PS1 (photosystem 1) - this causes electrons to be released and promoted to a higher energy level
The electrons are passed from one carrier to another in the ETC at decreasing energy levels which causes energy to be released - This energy is then used via the chemiosmotic theory to add phosphate to ADP to form ATP - photophosphorylation
- The released electrons are then accepted by NADP to form reduced NADP
- Photolysis (breaking) of water produces protons, electrons and oxygen
Describe the oxidative phosphorylation
This is essentially the Chemiosmotic Theory in action during aerobic respiration so use the same notes
Describe the Krebs cycle (stage 3 of aerobic respiration)
- Series of oxidation-reduction reactions occurs
- Generates reduced coenzymes and ATP by substrate-level phosphorylation (essentially direct formation of ATP from ADP and Pi using energy from the chemical processes occurring)
- Carbon dioxide is lost during krebs cycle
Describe the link reaction (stage 2 of aerobic respiration)
- Pyruvate is oxidised to acetate, producing reduced NAD in the process
- Acetate combines with coenzyme A in the link reaction to produce acetylcoenzyme A
- Acetylcoenzyme A reacts with a four-carbon molecule, releasing coenzyme A and producing a six-carbon molecule that enters the Krebs cycle
Describe the difference with what happens to pyruvate in aerobic and anaerobic respiration
If respiration is only anaerobic, pyruvate can be converted to ethanol or lactate using reduced NAD. The oxidised NAD produced in this way can be used in further glycolysis
If respiration is aerobic, pyruvate from glycolysis enters the mitochondrial matrix by active transport
Describe what happens during glycolysis
Phosphorylation of glucose using ATP
Production of triose phosphate
Oxidation of triose phosphate to pyruvate with a net gain of ATP and reduced NAD
Describe the need for respiration
To produce ATP
ATP is used for:
Active transport
Synthesis reactions e.g. protein/DNA synthesis
Muscle contraction
Cell division
Light independent reactions of photosynthesis
First stage of glycolysis (see following notes)
Describe what happens in eutrophication
- Leaching and runoff of inorganic fertilisers so increased concentration of nitrates and phosphates in lake
- Algal bloom on surface of water which means there is no light for plants on water bed, so can’t photosynthesise
- Death of plants so large quantities of decaying organic matter and therefore, Increased numbers of aerobic saprobionts
- Aerobic bacteria, fish and invertebrates die as dissolved oxygen is used up by saprobionts and they cannot respire
- Causes a reduction in species diversity
Describe the difference between artificial and natural fertilisers
- Natural Fertilisers – includes dead and decaying remains of plants and animals, manure and bone meal. As they decay, mineral ions are released which are taken up by crop plants
- Artificial Fertilisers – contain a mixture of inorganic compounds of nitrogen, phosphorous and potassium (NPK)
Describe the use of fertilisers
To replace nutrients removed by the growth and harvesting of crops and feeding
Describe the role of mycorrhizae
- Phosphorus in the form of phosphate ions is taken in through the roots of plants
- Some fungi form symbiotic or mutualistic (where both organisms benefit) relationships with plant roots - these relationships are known as mycorrhizae
- The fungi consists of hyphae – long, thin strands which connect with the plant roots and extend into the soil to increase the surface area for absorption of water and of ions such as phosphate
- In return the fungi receive organic compounds such as glucose produced by the plant during photosynthesis
Describe the role of denitrifying bacteria
Convert nitrates back into atmospheric nitrogen which then continues the cycle
Describe the role of saprobionants in ammonification
- Saprobiotic microorganisms cause decay and break down animal and plant proteins into ammonia which forms ammonium ions in the soil
- These ammonium ions will then form ammonia via ammonification
Describe the role of nitrifying bacteria
- Oxidise ammonia and ammonium ions in the soil into nitrites and then nitrates
- Nitrates are absorbed by plant roots by active transport and provide the source of nitrogen for the synthesis of proteins and nucleic acids
Describe the role of nitrogen fixing bacteria
Live free in the soil and ‘fix’ nitrogen into ammonia/ammonium compounds
Describe the role of saprobiotic microorganisms in decomposition
Used to break down the proteins in animals to form organic residues in soil that can be recycled
