Topic 5 Last Flashcards
(42 cards)
2 reactions of photosynthesis
- Light dependent
- Light independent
Structure of cholorplast
- Double membrane
- Stroma
- Thylakoid membrane
- Granum
- Linked by lamellae
How does the structure of the thylakoid membrane relate to the light depedent reaction?
- Large surface area for the attachment of:
Chlorophyll
Electron carriers
Enzymes - Permeable membrane for gas diffusion
- Fluid in the strom contains all enzymes required to make carbohydrates for the light indepedent reaction.
Light dependent reaction?
- Photoionisation
- Chlrophyll absorbs lightt, electrons are excited and are donated to an electron carrier that moves the electrons down the chain.
-Photolysis
- Electrons are replaced by the splitting of water into hydrogen, oxygen and electrons.
Chemiosmosis
- Excited electrons lose energy as they move down the ETC.
- This energy is used to pump Hydrogen ions into the thylakoid space via a proton pump.
- Creates a favourable concentration gradient for the diffusion of H+ ions into the stroma via ATP synthase, which catalyses ADP+Pi to form ATP.
Formation of NADPH
- Electrons from ETC and H+ ions that have diffused through ATP synthase are used to form Reduced NADP.
Light independent reaction
- occurs in the stroma
- Rubisco catalyses reaction of RuBP and CO2 to temporarily give an unstable 6-carbon compound which breaks down into 2 GP molecules.
- GP is reduced to TP using NADPH, using energy from ATP hydrolysis.
- TP is converted into useful organic compounds such as glucose and amino acids
- In one cycle 10 TP molecules are converted into RuBP but only 2 TPs are converted into useful compounds.
What factors limit the rate of photosynthesis
- Temperature (Involve enzymes which require optimum temperatures)
- CO2 concentration as the light independent reaction requires a source of carbon so fixation is slowed.
- Light intensity as energy from sunlight is needed to excite electrons in chlorophyll
What is glycolysis?
- Conversion of glucose into pyruvate
1) Occurs in the cytoplasm
2) Glucose is converted in glucose phosphate via ATP hydrolysis
3) 2xTP molecules are formed
4) 2 TP molecules are converted into 2 pyruvate molecules via redox reactions where ATP is oxidised and NAD is reduced
- 2 ATP net gain
- 2 NADH
- 4 ATP molecules
What happens in anaerobic respiration?
Animals
- Pyruvate is converted to lactate during redox with NADH
- Lactate regenerates NAD which is fed back into glycolysis, meaning ATP is still produced.
Plants
Pyruvate is converted to ethanal, producing CO2 in the process, then ethanal is converted to ethanol during a redox reaction that converts NADH to NAD.
What happens during the link reaction?
- Link reaction happens in the mitochondrial matrix
- Pyruvate loses carbon as CO2 and is converted to a 2C Acetate via a redox reaction of NAD.
- Acetate reacts with coA to form Acetyl coA.
- Link reaction would happen twice per glycolysis.
What happens in the Krebs Cycle?
- Mitochondrial matrix
- Acetyl coA reacts with 4C compound to produce 6C citrate
- Series of redox reactions produces 2 CO2 molecules, 3 NADH molecules, 1 FADH2 molecules and 1 ATP molecule.
- coA is regenerated
Oxidative phosphorylation
1) H atoms released from NADH and FADH2
2) Hydrogen atoms split into hydrogen ions and electrons.
3) Electrons move down the ETC
4) Energy lost by electrons at each carrier are used to pump hydrogen ions into the intermembrane space via a proton pump creating a favourable concentration gradient for diffusion of hydrogen ions into the matrix via ATP synthase causing it to spin.
- Catalysed ADP+Pi -> ATP.
- O2 combines with hydrogen ions and electrons to form water.
Why is oxygen considered the last electron acceptor.
- Oxygen accepts H+ ions and electrons to form water
- ETC would stop and no pumping of hydrogen ions, no gradient for the diffusion of hydrogen ions so no ATP molecules produced.
What is biomass?
- The mass of carbon or dry mass of tissue per given area.
What is calorimetry
1) Dry the sample, burn the sample
2) Use this to heat a known volume of water
3) Measure temperature change and use this to calculate the chemical energy that was stored in the dry biomass.
What is the Gross Primary Production
- The chemical energy store in plant biomass, in a given area or volume.
What is the Net Primary Production
- The chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.
Formula for NPP
NPP=GPP-R
What is the energy from the NPP used for?
- Available for plant growth and reproduction. It is also available for other trophic levels in the ecosystem.
How do we calculate the net production of consumers
N=I - (F+R)
N - Net production of consumers
I = Chemical energy store
F = Energy lost in faeces and urine
R = Respiratory losses in the environemtn
Why is so much energy lost at each trophic level
- In plants, some light energy is reflected or transmitted through loveaves or not of the right wavelength so the efficiency of photosynthesis is very low.
- Energy is lost to the surrounding as heat from respiration.
- Energy lost in faeces or urine.
- Some parts of the organism are not eaten, so some energy is not transferred to the next trophic level.
Why are food chains often limited to 4-5 trophic levels?
- Energy is lost at each trophic level so the efficiency of energy transfer is very low.
- Total biomass is less at higher trophic levels
- Insufficient energy available to support a large enough breeding population.
How does farming maximise energy>
- Simplify food webs by using pesticides so that energy isn’t lost.
- Reduce respiratory losses within a human food chain such as controlling the conditions livestock are kept in such as restricting their movement or keeping them warm (unethical) .
- More biomass so greater chemical energy store so more biomass and a higher chemical energy store so more NPP and efficiency of transfer.
Primary and Secondary productivity
- The rate of primary and secondary production respectively
- kJ per hectare per year
What is the role of microorganisms in nutrient cycles ?
- Break down organic molecules into simple inorganic molecules and ions, that plants can make use of.
- Saprobionts feed by extracellular digestion by secreting digestive enzymes and absorb the soluble nutrients released.
- Converts organic into inorganic compounds
- DNA, RNA and amino acids into phosphates and nitrates
