Energy transfers

photosynthesis

structure of chloroplast

  • contain stacks of thykaloids membranes called grana - provides large surface area for attachment of chlorophyll, electrons and enzymes

  • contain dna and ribosomes allowing them to synthesise proteins needed in LDR

  • ATP synthase channels allowing ATP to be synthesised as well as being selectively permeable allowing establishment of a proton gradient

LDR - thykaloid

  • light energy excites electrons, which are lost from chlorophyll (photoionisation)

  • electrons move along electron transfer chain releasing energy

  • energy used to join ADP and Pi to form ATP (photophosphorylation)

  • photolysis of water produces protons, electrons and oxygen

  • NADP reduced by electrons and protons/hydrogen

LIR - stroma

  • calvin cycle

  • carbon dioxide combines with RuBP catalysed by rubisco

  • produces 2x GP

  • GP reduces to triose phosphate

  • using reduced NADP (NADPH)

  • using energy from ATP

  • 5/6 converted to RuBP

  • 1/6 converted to glucose

Limiting factors of photosynthesis

  • no light = no gp to tp (no LDR)

  • no co2 = no RuBP to GP (doesn’t combine)

  • temperature = calvin cycle catalysed by enzymes

Agricultural practises

  • temperature controlled with burners and window

  • CO2 concentration controlled with burner to release CO2

  • light intensity controlled by greenhouses

  • number of chlorophyll molecules controlled by selective breeding/growing specific species

respiration

Glycolysis - cytoplasm

Pigeons, sell, oranges, anywhere (phosphorylation, splitting, oxidation, ATP production)

  • phosphorylation of glucose using ATP

  • phosphorylated glucose split into 2 molecules of triose phosphate

  • oxidation triose phosphate to pyruvate - hydrogen reduces NAD to NADH

  • 2 pyruvate (3c) produced - formation of 2 ATP - net gain of ATP - 4 produced, 2 used

Link reaction - mitochondria matrix

Always, open, juice (active transport, oxidation, joins)

  • 2 molecules of pyruvate actively transported into mitochondria from cytoplasm

  • pyruvate oxidised forming acetate and CO2 (requires reduction of NAD to NADH)

  • acetate joins with coenzyme A to form acetyl coenzyme A

Krebs cycle - mitochondria matrix

  • acetyl coenzyme A combines with 4c molecule to form citrate (6C)

  • citrate releases 2 molecules of CO2 and oxidised which releases hydrogens that reduce NAD and FAD

  • for each acetyl coenzyme A that enters cycle one ATP is synthesized

  • 4C molecule regenerated for next turn in cycle (oxaloacetate)

Per 1 molecule of glucose:

  • glycolysis produces 4 ATP, uses 2 ATP, produces NADH

  • link reaction produces 2 NADH, 2 CO2

  • Krebs cycle produces 2 ATP, 6 NADH, 2 FADH, 4 CO2

  • total production = 6 ATP, 2 used, 10 NADH, 2 FADH, 6 CO2

electron transfer chain

  • hydrogen carriers (NADH, FADH2) oxidised and release high energy electrons and protons

  • electrons pass down chain in series of REDOX reactions yielding free energy - used by the chain to actively transport hydrogen ions from matrix into inter membrane space

  • accumulation of H+ ions within intermembrane space creates electrochemical gradient

  • concentration gradient of H+ ions causes them to move down electrochemical gradient and diffuse back into matrix through enzyme ATP synthase

  • diffusion of protons called chemiosis

  • H+ ions move through ATP synthase they trigger molecular rotation of enzyme, synthesising ATP from ADP and Pi

  • electrons removed for ETC to continue functioning

  • oxygen acts as terminal electron acceptor

  • oxygen binds to free protons in matrix to form water - removing matrix protons maintains hydrogen gradient

  • in absense of oxygen, hydrogen carriers cannot transfer energised electrons to chain and ATP production halted

  • produces 32 molecules of ATP

Anaerobic respiration in animals and yeast

  • no oxygen present

  • no final acceptor of electrons from ETC

  • ETC stops functioning

  • no more ATP produced via oxidative phosphorylation

  • NADH and FADH aren’t oxidised by electron carrier

  • no oxidised NAD and FAD are available for regeneration in krebs cycle

  • krebs cycle stops

  • in order for glycolysis to continue, NAD must be regenerated so it can be used for glycolysis again

Mitochondiral structure

energy and ecosystems

ecosystem = interacting biotic and abiotic factors

population = all of the organisms of same species living in same habitat at same time

community = all of the organisms belonging to all of the different species that coexist in same habitat at same time

ecological niche = role of species in its environment, including food, predators etc.

biotic factors = living factors of an environment

abiotic factors = non-living factors of an environment

Biomass and energy transfer

  • energy transfer to plants:

    • some light energy is reflect from a leafs waxy cuticle

    • some light doesn’t hit chlorophyll and is transmitted through the leaf

    • light wrong wavelength so not absorbed by chlorophyll

    • some energy dissipates as heat during reactions in photosynthesis (LIR enzymes)

    • energy that is stored in glucose is then released during plant respiration, so not available to be eaten

Net primary production, gross primary production

  • NPP = GPP - R

  • primary productivity = rate at which plants make organic material

  • GPP = total amount of chemical energy stored in plant biomass as a result of photosynthesis - e.g. plant respiration

  • NPP = quantity of chemical energy in plant biomass that is left after respiratory losses - used by plants for own growth (passed onto next trophic level)

  • NPP = growth in plant, N = growth in animal

Efficiency of energy transfer

  • not all organisms in one trophic level are eaten by organisms from next level

  • not all food available to be consumed e.g. roots, bones

  • food that is eaten may be indigestible - not have enzymes to break down e.g. cellulose

  • excretory materials loose energy

  • energy lost to environment as heat energy via respiration

Pyramids of biomass/energy

  • pyramids of number - no. of organisms as each level. Inverted pyramids = happen because a single large producer supports many small primary consumers e.g. tree, or parasites occupy higher trophic level e.g. flea

    • don’t reflect amount of energy present

  • pyramids of biomass - total dry mass at any one time - take into account difference size between organisms

    • fluctuates throughout year

  • pyramids of energy - x axis = energy. Avoids inverted pyramids, VAT = rate of photosynthesis, volume of gas in a given area in given time. EAT = energy in given area at given time

productivity and farming practices

  • want NPP or N to be large = eaten

  • N = I - (R + F) - food - respiration + faeces

  • how do intensive rearing of domestic livestock increases net productivity:

    • animals selectively bread or geneticallly selected = rapid growth - more muscle production

    • animals are kept in small spcaes so can't move around much = less muscle contraction = less heat loss via respiration = more N

    • animals kept inside often in heated environments = less gradient for heat loss = less heat energy lost via R = more N

    • animals fed controlled diets that contain specific nutrients = food digested and absorbed = biomass less faeces

    • animals slaughtered before they reach maturity = N plateaus at maturity = waste input energy

  • explain how farming practises increase productivity of agricultural crops

    • fertilisers added to soil = nitrates = protein synthesis = more growth

    • pesticides used = remove pests = less crops eaten = more biomass crop

    • weed killers used = removes competitors (interspecific) - more light absorbed etc. = more growth

    • crop plants selectively bred e.g. rapid growth/disease resistant = more biomass

    • plants kept in greenhouse = controlled environment = e.g. co2, water

    • soils ploughed = o2 added to aerate soil = nitrification = nitrates = protein synthesis = more growth

    • crop rotation occurs = leguminous plants increase nitrate content of soil

Abiotic factors affect plant growth

  • light intensity = used in photosynthesis of water/electron excitation/making ATP/NADPH

  • CO2 = substrate for LIR of photosynthesis = more co2 = more can combine with RuBP = more GP made

  • temperature = increase rate of enzyme controlled reactions

  • nitrogen ions = nitrates to make amino acids for protein synthesis = magnesium ions to make chlorophyll to absorb light energy

  • water = support, mediums for reactions

  • pH = optimum pH needed for enzyme controlled reactions e.g. excess H+ may denature enzymes and show reactions

nutrient cycles

saprobiont = organisms that digest their food externally by releasing enzymes and then absorbing the products - decomposers

Nitrogen cycle (nitrogen fixation, ammonification, nitrification, dentrification)

  • protein broken down into ammonia

  • by saprobionts

  • ammonia converted to nitrite ions

  • nitrite ions oxidised to nitrate ions

  • by nitrifying bacteria

  • nitrogen converted to ammonia

  • by nitrogen fixing bacteria

phosphorus cycle

  • phosphorus contained in soils, oceans and rocks

  • plants take it up by absorption

  • this is passed to consumers

  • phosphates released back into soil by saprobionts

  • phosphates can also be locked up in rocks

role of microorganisms in nutrient recyling

mutualistic relationships and mycorrhizae

  • mycorrhizae increases absorption of phosphates in exchange for sugars from plant - mutualistic relationship (symbiotic)

fertilisers and environmental issues

natural vs artificial fertilisers

environmental impact (leaching, eutrophication)

managing ecosystems sustainably