CHAPTER 5 - PHOTOSYNTHESIS, RESPIRATION AND NUTRIENT CYCLES Flashcards
- photosynthesis, LDR and LIR - limiting factors in photosynthesis - aerobic and anaerobic respiration - energy transfer in ecosystems - farming practices - nutrient cycles - fertilisers and eutrophication
why is energy important
- plants and animals need energy for biological processes to occur
- plants need energy for photosynthesis, active transport, DNA replication, cell division and protein synthesis
- animals need energy for muscle contraction, maintaining body temperature, active transport, DNA
what is the process of photosynthesis
- the process where ENERGY from LIGHT is used to make GLUCOSE from WATER and CARBON DIOXIDE
- the LIGHT ENERGY is converted to CHEMICAL ENERGY in the form of GLUCOSE (c6h12o6)
- ENERGY is stored in the GLUCOSE until the PLANTS release it by RESPIRATION
- ANIMALS obtain GLUCOSE by eating PLANTS (or by eating other animals, which have eaten plants), then RESPIRE the GLUCOSE to RELEASE ENERGY
what is the chemical equation for photosynthesis
6CO2 + 6H2O + energy -> C6H12O6 + 6O2
what is photosynthesis an example of
a metabolic pathway, the process occurs in a series of small reactions controlled by enzymes
how do plants and animal cells release energy from glucose
respiration
what is the energy from respiration used for
- used to power all the biological processes in a cell
what would happen to these biological processes (ex, photosynthesis and respiration) if there was no energy
they would stop and the plant/animal would die
what are the 2 types of respiration
aerobic and anaerobic respiration
what is the difference between aerobic and anaerobic respiration
aerobic respiration uses oxygen
what is aerobic respiration
respiration using oxygen
what is anaerobic respiration
respiration without oxygen
what is the chemical equation for aerobic respiration
C6H12O6 + 6O2 -> 6CO2 + 6H20 + energy
what is the purpose of anaerobic respiration
- in plants and yeast -> produces ethanol and carbon dioxide and releases energy
- in humans -> produces lactate and releases energy
what are aerobic and anaerobic respiration both an example of
metabolic pathways
what is the name of any organism that carries out photosynthesis
- photoautotroph (an organism that can make its own food using light energy)
- the process of photosynthesis is the SAME in ALL photoautotrophs -> suggests that they all evolved from a COMMON ANCESTOR
is energy created, destroyed or neither?
- energy is never created or destroyed
- energy is always converted from one form to another
- ex, (in photosynthesis) light energy is converted to chemical energy (glucose) and this energy is used to fuel biological processes
what is ATP
- adenosine triphosphate
- the immediate source of energy in a cell
what is the purpose of ATP
- a cell cant get its energy directly from glucose, so in RESPIRATION the energy released from GLUCOSE is used to make ATP
- it carries energy AROUND the cell to where its needed
what is ATP made of
- nucleotide base ADENINE
- RIBOSE sugar (pentose sugar)
- 3 phosphate groups
how is ATP formed
- ATP is SYNTHESISED via a CONDENSATION REACTION between ADP and Pi, using energy from an energy-releasing reaction (like the breakdown of glucose in respiration)
- the energy is stored as CHEMICAL ENERGY in a PHOSPHATE BOND
- the enzyme which catalyses this ^ reaction is ATP SYNTHASE (synthase = synthesise = joins)
what is phosphorylation
- ADDING phosphate to a molecule
- ex, ADP is PHOSPHORYLATED to ATP
- ATP then diffuses to the part of the cell that NEEDS energy
- CHEMICAL ENERGY is RELEASED from the PHOSPHATE BOND and USED by the CELL
- the enzyme which CATALYSES this ^ reaction is ATP HYDROLASE (hydrolase = hydrolyse = break)
describe the properties of ATP
- stores/releases only a SMALL, manageable amount of energy at a time, so NO energy is WASTED as HEAT
- its a SMALL and SOLUBLE molecule, so it can be EASILY TRANSPORTED around the cell
- EASILY BROKEN DOWN = energy can be released INSTANTLY
- it can be quickly REMADE
- it can make other molecules more REACTIVE through transferring one of its Pi groups to them (PHOSPHORYLATION)
- ATP can’t pass out of the cell = cell always has an IMMEDIATE supply of ENERGY
what processes do plants both carry out
photosynthesis and respiration
how do the plants carry out both processes
- can occur at the same time
- can occur at different rates
the rate of photosynthesis is partly dependent on?
the LIGHT INTENSITY of the ENVIRONMENT the plant is in
what is the compensation point for light intensity
the particular level of LIGHT INTENSITY at which the rate of photosynthesis exactly MATCHES the rate of respiration
how can the compensation point for a plant be worked out
- to measure the rate at which OXYGEN is PRODUCED and USED by a plant at DIFFERENT LIGHT INTENSITIES
- because photosynthesis PRODUCES O2 and RESPIRATION USES O2, the compensation point is the light intensity at which oxygen is being USED as quickly as it is PRODUCED
- the rate of CO2 production and use could also be measured because photosynthesis USES CO2 and respiration PRODUCES it
where does photosynthesis take place
the chloroplasts
what is the first reaction that takes place in photosynthesis
the light dependent reaction/LDR
describe the structure of chloroplasts
- small + flattened organelles
- surrounded by a double membrane
- thylakoids (fluid filled sacs) are stacked up -> forms grana
- a single grana = granum
- the grana are linked together by lamellae (bits of thylakoid membrane)
- a single lamellae = lamella
- photosystems are contained within the inner membrane of the chloroplast
- stroma ( a gel like substance) surrounds the thylakoids
- stroma contains enzymes, sugars and organic acids
- carbohydrates that are produced by photosynthesis, but not used immediately, are stored as STARCH GRAINS in the stroma
what do chloroplasts contain which absorb the light energy needed for photosynthesis
- photosynthetic pigments
what photosynthetic pigments do chloroplasts contain and what is their purpose
- chlorophyll a
- chlorophyll b
- carotene
- they are coloured substances that absorb the light energy needed for photosynthesis
- the pigments are found in THYLAKOID MEMBRANES
- they are attached to proteins = protein and pigment is called a PHOTOSYSTEM
- there are 2 photosystems used by plants to capture light energy, PSI and PSII
- PSI = photosystem I
- absorbs light best at a wavelength of 700 nm
- PSII = photosystem II
- absorbs light best at a wavelength of 680 nm
what are redox reactions
- reactions that involve OXIDATION and REDUCTION
- they occur in photosynthesis and respiration
- if something is REDUCED, it has GAINED ELECTRONS and may have GAINED HYDROGEN or LOST OXYGEN
- if something is OXIDISED, it has LOST ELECTRONS and may have LOST HYDROGEN or GAINED OXYGEN
- oxidation of one molecule ALWAYS involved the reduction of another molecule
what are coenzymes
- coenzyme = a molecule that aids the function of an enzyme
- work by transferring a chemical group from one molecule to another
- a coenzyme used in PHOTOSYNTHESIS = NADP
- NADP transfers HYDROGEN from one molecule, to another = it can REDUCE (give H to) or OXIDISE (take H from) a molecule
what are the 2 stages which make up photosynthesis
- the light dependent reaction/LDR
- the light independent reaction/LIR
what happens in the light dependent reaction
- reaction NEEDS light energy
- takes place in the thylakoid membranes of the chloroplasts
- light energy is absorbed by chlorophyll, and other photosynthetic pigments, in the photosystems
- the light energy excites the ELECTRONS in the chlorophyll, giving them MORE ENERGY = eventually causes the, to LEAVE the chlorophyll molecule
- ^ this process is PHOTOIONISATION
- chlorophyll is now a POSITIVELY CHARGED molecule
- some of the energy from the RELEASED ELECTRONS is used to add a Pi to ADP, forming ATP
- some of the energy from the RELEASED ELECTRONS is used to reduce NADP, forming reduced NADP/NADPH
- ATP transfers energy and NADPH transfers hydrogen to the LIR
- during the process, H2O is OXIDISED to O2
the energy resulting from the photoionisation of chlorophyll, in the LDR, is used for what?
- making ATP from ADP and Pi, called photopohsphorylation (process of adding phosphate to a molecule using light)
- making NADPH from NADP
- splitting water into protons (H+ ions/hydrogen ions), electrons and oxygen
- this is called photolysis (splitting of a molecule using light energy)
what are the products of the LDR
- ATP
- NADPH/ reduced NADP
- H ions
- oxygen
what are the 2 types of photophosphorylation that take place in the LDR
- non cyclic photophosphorylation
- cyclic photophosphorylation
describe the process of non-cyclic photophosphorylation
basics
- produces ATP, NADPH and O2
- photosystems are linked by ELECTRON CARRIERS (proteins that transfer electrons)
- photosystems and electron carriers form an ELECTRON TRANSPORT CHAIN (a chain of proteins through which excited electrons flow)
- multiple processes going on simultaneously in non-cyclic photophosphorylation
light energy excited electrons in chlorophyll
- light energy absorbed by PSII
- light energy excited electrons in chlorophyll
- the electrons move to a HIGHER energy level (have MORE energy)
- these high energy electrons are RELEASED from the chlorophyll, they then move down the ETC to PSI
photolysis of water produces protons, electrons and oxygen
- because the excited electrons leave the chlorophyll (and go to PII via the ETC), they must be replaced
- light energy splits water into protons (H+ ions), electrons and oxygen = PHOTOLYSIS
- equation = H2O -> 2H + 1/2 O2
- the electrons from photolysis ^ here, replace the electrons lost in photoionisation
energy from the excited electrons makes ATP
- the excited electrons LOSE energy as they move DOWN the ETC and this energy is used to transport protons (H+ ions) into the THYLAKOID (so the thylakoid has a HIGHER CONC of PROTONS than the STROMA)
- ^ this forms a proton gradient across the THYLAKOID MEMBRANE
- protons move DOWN their conc gradient, into the stroma, via enzyme ATP SYNTHASE (which is embedded in the thylakoid membrane)
- the energy from this movement combined ADP and Pi, forming ATP
energy from the excited electrons generates NADPH
- light energy is absorbed by PSI, which excites the electrons again to an even HIGHER energy level
- finally, the electrons are transferred to NADP along with a proton (H+/hydrogen ion) from the STROMA to form NADPH
describe chemiosmotic theory
- chemoiosmosis = the process of electrons flowing DOWN the ETC and creating a PROTON GRADIENT across the membrane to drive ATP synthesis
- ^ this process is described by the chemiosmotic theory
describe the process of cyclic photophosphorylation
- produces ATP
- only uses PSI
- called ‘cylic’ because the electrons from the chlorophyll molecule aren’t passed onto NADP, instead they are passed back to PSI via electron carriers
- ^ this means the electrons are RECYCLED flow through PSI
- this process doesn’t produce any NADPH or O2
- only produces small amounts of ATP
how is ATP formed in non-cyclic and cyclic photophosphorylation
by the movement of protons across the thylakoid membrane
describe the light independent reaction/the calvin cycle
- this reaction does NOT use light energy directly
- it DOES rely on the products of the LDR
- takes place in the stroma
- the ATP and NADPH from the LDR supplies the energy and hydrgogen to make GLUCOSE from CO2
describe the basics of the calvin cycle/light independent reaction
- takes place in the stroma
- makes triose phosphate (TP), from CO2 and ribulose bisphosphate (5 carbon compound)
- TP can be used to make glucose and other useful organic substances
- few steps in the cycle
- needs H+ ions to keep it going
- RuBP is regenerated
describe what takes place in the calvin cycle/LIR in detail
formation of glycerate 3-phosphate
- CO2 enters the leaf through the stomata and diffuses into the stomata of the chloroplast
- it is combined with RuBP, this reaction is catalysed by rubisco (enzyme)
- ^ this produces a 6 carbon compound
- the unstable 6 C compound quickly breaks down into 2 molecules of a 3 C compound, called GLYCERATE PHOSPHATE (GP, has 3 C each)
formation of triose phosphate
- the hydrolysis of ATP (from the LDR) provides energy to reduce GP to TP, which is a different 3C compound
- ^ this reaction also requires H+ ions (reduction reaction), which come from NADPH (from the LDR)
- NADPH is recycled to NADP
- some TP is converted into useful organic compounds, like GLUCOSE, and some continues in the calvin cycle to REGENERATE RuBP
regeneration of RuBP
- 5/6 molecules of TP in the cycle are used to regenerate RuBP, instead of making useful organic compounds
- regenerating RuBP uses the rest of the ATP produces by the LDR
what are hexose sugars
- simple 6 carbon sugars, like glucose
- one hexose sugar is made by joining 2 MOLECULES OF TP
- hexose sugars can be used to make larger carbohydrates
how many times does the cycle have to turn to produce a molecule of glucose
- 6 times
- ^ this is because, 3 turns of the cycle produces 6 molecules of TP (2 molecules of TP are made for every 1 molecule of CO2 molecule used)
- 5/6 of TP molecules are used to REGENERATE RuBP
- ^ this means that for 3 turns of the cycle, only 1 TP molecule is produced that is USED TO MAKE A HEXOSE SUGAR
- a HEXose sugar has 6 carbons, so 2 TP molecules are needed to form 1 hexose sugar
- the cycle must turn 6 times to produce 2 molecules of TP, that can be used to make 1 hexose sugar
- 6 turns of the cycle require = 18 ATP molecules and 12 NADPH molecules from the LDR
- ^ this may seem inefficient, however it allows the cycle to continue and also ensures that there’s always enough RuBP ready to combine with CO2, taken in from the atmosphere
how is TP and GP used to make carbohydrates
- hexose sugars are made from 2 TP molecules
- larger carbohydrates (sucrose, starch, cellulose) are made by joining hexose sugars together in different ways
how is TP and GP used to make lipids
- these are made using glycerol, which is SYNTHESISED from TP
- fatty acids are SYNTHESISED from GP
how is TP and GP used to make amino acids
some amino acids are made from GP
summarise the calvin cycle into inputs and outputs
inputs
- CO2
- ATP
- NADPH
outputs
- organic substances (ex, glucose)
- RuBP
list the limiting factors in photosynthesis
- light intensity
- temperature
- CO2 concentration
- water
how is high light intensity of a certain wavelength an optimum condition for photosynthesis
- light is needed to provide the energy for LDR
- the higher the intensity of the light, the more energy it provides
- only CERTAIN wavelengths of light are used for photosynthesis
- the photosynthetic pigments chlorophyll a, chlorophyll b and carotene only absorb the RED and BLUE light in sunlight
how is a temperature of around 25 degrees celsius an optimum condition for photosynthesis
- photosynthesis involved enzymes, ATP synthase and rubisco
- if the temp falls BELOW 10 degree cel, the enzymes may become INACTIVE
- if the temp goes above 45 degrees cel, the enzymes may start to DENATURE
how is a CO2 level of 0.4% an optimum condition for photosynthesis
- CO2 makes up 0.04% of the gases in the atmosphere
- increasing this to 0.4% gives a higher rate of photosynthesis
- any higher than this rate will cause the stomata to start to close
how is a constant water supply an optimum condition for photosynthesis
- plants need a constant water supply
- too little water = photosynthesis
- too much water = soil becomes WATERLOGGED, which reduces the uptake of minerals like magnesium, which is needed to make chlorophyll a
list and explain the limiting factors of photosynthesis
- light
- temperature
- carbon dioxide
- if any one of these ^ factors are too low or high, it will LIMIT photosynthesis, even if the other 2 factors are at the optimum level
how agricultural growers, like farmers, create an environment which has the right amount of everything needed
- the right amount of everything increases growth, and therefore increases yield
- growers create optimum conditions in GLASSHOUSES
CO2 CONCENTRATION
- carbon dioxide is added to the air
- ex - by burning a small amount of PROPANE in a CO2 generator
LIGHT
- light can get in through the glass
- at night time, lamps provide light
TEMPERATURE
- glasshouses trap heat energy from sunlight, which warms the air
- heaters and cooling systems can also be used to keep a CONSTANT OPTIMUM TEMP
- air circulation systems ensure the temp us even throughout the glasshouse
what is the purpose of respiration
it is the process which allows cells to produce ATP from glucose
what are the 2 types of respiration
- aerobic respiration (with oxygen)
- anaerobic respiration (without oxygen)
compare aerobic respiration and anaerobic respiration
- respiration can be done with O2 (aerobic), and without O2 (anaerobic)
- both types of respiration produce ATP, but anaerobic respiration produces LESS ATP
- both start with glycolysis, however the stages after glycolysis differ
what is the structure of the mitochondria and how does this relate to respiration
- the reactions in aerobic respiration take place in the mitochondria
- the CRISTAE in the inner membrane (the folds) = provide a LARGE SA = MAXIMISES RESPIRATION
what are coenzymes and what are the coenzymes in respiration and what is their purpose
- a coenzyme = a molecule that aids the function of an enzyme, by transferring a chemical group from one molecule to another
- the coenzymes in respiration = NAD, coenzyme A and FAD
- NAD + FAD = can reduce or oxidise a molecule
- coenzyme A = transfers ACETATE between molecules
what are the 4 stages in aerobic respiration
- glycolysis
- the link reaction
- the krebs cycle
- oxidative phosphorylation
summarise the roles of each stage in aerobic respiration
- the first 3 stages are a SERIES OF REACTIONS
- the products from these ^ reactions are used in the final stage
- the first stage, glycolysis, happens in the CYTOPLASM of cells
- the other 3 stages take place in the MITOCHONDRIA
what does respiration produce and how are these products used
- GLUCOSE can be used as a RESPIRATORY SUBSTRATE in BOTH aerobic and anaerobic respiration
- glucose isn’t the only respiratory substrate that can be used in aerobic respiration
- some products resulting from the breakdown of other molecules, like fatty acids from lipids and amino acids from proteins, can be CONVERTED INTO MOLECULES WHICH CAN ENTER THE KREBS CYCLE, usually acetyl CoA
what steps are in anaerobic respiration
- doesn’t involve the link reaction, krebs cycle or oxidative phosphorylation
- the products of glycolysis are converted to ETHANOL or LACTATE instead
what happens in glycolysis - basics
- glycolysis makes PYRUVATE from GLUCOSE
- glycolysis involves splitting ONE molecule of GLUCOSE (6C) into TWO smaller molecules of PYRUVATE (3C)
- process takes place in the cytoplasm of cells
- glycolysis is the first stage of BOTH aerobic and anaerobic respiration
- doesn’t need O2 to take place, therefore it is an ANAEROBIC PROCESS
- the 2 stages in glycolysis are phosphorylation and oxidation
describe what happens in glycolysis - in detail
PHOSPHORYLATION
- glucose is phosphorylated using a phosphate molecule from ATP
- this ^ creates 1 molecule of GLUCOSE PHOSPHATE + 1 molecule of ADP
- ATP is then used to add ANOTHER Pi, forming HEXOSE BIPHOSPHATE
- hexose biphosphate is then split into 2 molecules of TRIOSE PHOSPHATE
OXIDATION
- TP is oxidised (loses hydrogen), this forms 2 molecules of PYRUVATE
- NAD collects the H+ ions, forming 2 NADH/reduced NAD
- 4 ATP are produced, but 2 ATP were used in stage 1 (phosphorylation), therefore there is a NET GAIN of 2 ATP
name all the products of glycolysis and where they go to (in aerobic respiration)
- 2 NADH/reduced NAD = to OXIDATIVE PHOSPHORYLATION
- 2 pyruvate = actively transported into the mitochondrial matrix for use in the link reaction
- 2 ATP (net gain) = used for energy
why does glycolysis take place in the cytoplasm
- glucose cant cross the outer mitochondrial membrane
- pyruvate can cross this membrane, so the rest of the aerobic respiration occur within the mitochondria
what are the products of glycolysis in anaerobic respiration
- in anaerobic respiration, the PYRUVATE produced in glycolysis is converted into ethanol (alcoholic fermentation) or lactate (lactate fermentation) using NADH
ALCOHOLIC FERMENTATION
- this occurs in PLANTS and YEAST
- pyruvate is DECARBOXYLATED, which forms ETHANAL
- ethanal is REDUCED by NADH, which becomes NAD, and this forms ETHANOL
LACTATE FERMENTATION
- this occurs in animal cells and some bacteria
- pyruvate is reduced, to form lactate/lactic acid
- it is reduced by NADH, so it also forms NAD
- the production of lactate or ethanol regenerates oxidised NAD
- this ^ means glycolysis can CONTINUE even when there isn’t much oxygen around, so a small amount of ATP can still be produced to keep some biological processes going
what happens in the link reaction
- the link reaction converts the pyruvate (produced in glycolysis) to ACETYL COENZYME A
- pyruvate DECARBOXYLATED, so one carbon atom is removed from the PYRUVATE in the form of CO2
- at the same time, pyruvate is OXIDISED to form ACETATE and NAD is reduced to form NADH
- acetate is combined with CoA to form ACETYL COEZYME A
- NO ATP IS FORMED IN THIS REACTION
how many times does the link reaction need to occur per glucose molecule
- 2 pyruvate molecules are made per glucose molecule which enters glycolysis
- link reaction and the krebs cycle happen TWICE for every glucose molecule
what are the products of a single link reaction, and of 2 link reactions (which is for every glucose molecule) and where to they go
1 link reaction
- 1 acetyl CoA
- 1 CO2
- 1 NADH
2 link reactions, per glucose mol
- 2 acetyl CoA
- 2 CO2
- 2 NADH
- the 2 acetyl CoA go to the KREBS CYCLE
- the 2 CO2 are released as a waste product
- the 2 NADH go to the oxidative phosphorylation
what is the krebs cycle - basics
- produces reduced coenzymes and ATP
- involves a series of oxidation-reduction/redox reactions, which take place in the MATRIX
- cycle happens ONCE for every pyruvate molecule
what happens in the krebs cycle - detailed
FORMATION OF A 6C COMPOUND
- acetyl coA (from the link reaction) combined with a 4C molecule (oxaloacetate) to form a 6C compound (citrate)
- CoA goes back to the link reaction to be used again
FORMATION OF A 5C COMPOUND
- the 6C compound is converted to 5C
- DECARBOXYLATION occurs, where CO2 is removed
- DEHYDROGENATION also occurs, the H is used to produce NADH from NAD
REGENERATION OF OXALOACETATE
- the 5C molecule is converted to a 4C molecule
- decarboxylation and dehydrogenation occur = this produces 1 molecule of FADH + 2 molecules of NADH
- ATP is produced by the direct transfer of a phosphate group from an INTERMEDIATE COMPOUND to ADP
- when a phosphate group is directly transferred from one molecule to another, its called SUBSTRATE-LEVEL PHOSPHORYLATION
- citrate has now been converted to oxaloacetate
how many krebs cycles take place per glucose molecule
2
how many products per 1 krebs cycle and where do they go
- 1 CoA -> reused in the next link reaction
- oxaloacetate -> regenerated for use in the next krebs cycle
- 2 CO2 -> released as a waste product
- 1 ATP -> used for energy
- 3 NADH -> to oxidative phosphorylation
- 1 FADH -> to oxidative phosphorylation
what is oxidative phosphorylation - basics
- the process where the energy carried by electrons, from reduced coenzymes (NADH and FADH), is used to MAKE ATP
- the whole point of the previous stages stages is to make NADH and FADH for the final stage
- oxidative phosphorylation involves the electron transport chain and chemiosmosis
describe the process of oxidative phosphorylation
STEP 1
- hydrogen atoms are released from NADH and FADH as they are oxidised to NAD and FAD
- the H atoms are split into protons (H+) and electrons (e-)
STEP 2
- the electrons move DOWN the ETC (made of electron carriers), LOSING ENERGY at each carrier
STEP 3
- this energy is used by the electron carriers to pump protons from the MITOCHONDRIAL MATRIX into the INTERMEMBRANE SPACE (the space between the inner and outer mitochondrial membranes)
STEP 4
- the concentration of protons is now HIGHER in the INTERMEMBRANE space than in the MITOCHONDRIAL MATRIX - this forms an ELECTROCHEMICAL GRADIENT (a conc gradient of ions)
STEP 5
- protons then move down the electrochemical gradient, back across the inner mitochondrial matrix, via ATP synthase (which is embedded in the inner mitochondrial membrane)
- this movement drives the synthesis of ATP from ADP and Pi
STEP 6
- this process of ATP production driven by movement of H+ ions across a membrane (due to electrons moving down an ETC) is called CHEMIOSMOSIS
STEP 7
- in the mitochondrial matrix, at the end of the ETC, the protons (H+), electrons and oxygen (from the blood) combine to form WATER
- oxygen is said to be the FINAL ELECTRON ACCEPTOR
how much ATP is made from each NADH and each FADH
- 2.5 ATP are made from each NADH
- 1.5 ATP are made from each FADH
how many molecules of ATP are made from 1 molecule of glucose in aerobic respiration in a cell
32 ATP
name the stage of respiration, molecules produced and number of ATP molecules a cell can make from 1 mol of glucose in AEROBIC RESPIRATION
- glycolysis, 2 ATP mols produced , 2 ATP mols produced
- glycolysis, 2 NADH mols produced, 5 ATP mols produced
- link reaction x2, 2 NADH mols produced, 5 ATP mols produced
- krebs cycle x2, 2 ATP mols produced (net)
- krebs cycle x2, 6 NADH mols produced, 15 ATP mols produced
- krebs cycle x2, 2 FADH mols produced, 3 ATP mols produced
- total ATP produced per glucose mol = 32 ATP mols
summarise aerobic respiration
- glycolysis, link reaction and the krebs cycle are basically a series of reactions which produce ATP, NADH, FADH and CO2
- the reduced coenzymes, NADH and FADH, are then used in oxidative phosphorylation, to produce more ATP
what are mitochondrial diseases
- ATP production can be affected by mitochondrial diseases
- mitochondrial diseases affect the functioning of mitochondria
- they can affect how proteins involved in oxidative phosphorylation or the krebs cycle function, reducing ATP production
- this may cause anaerobic respiration to increase, to try and make up some of the ATP shortage
- this results in lots of lactate being produced, which can cause muscle fatigue and weakness
- some lactate will also diffuse into the bloodstream, leading to high lactate concentration in the blood
what are the basics of ecosystems
- an ecosystem includes all the ORGANISMS in a particular area and all the ABIOTIC (non-living) CONDITIONS
- in all ecosystems, there are PRODUCERS (organisms which make their own food)
- ex, in land based ecosystems, plants (like trees) produce their own food through PHOTOSYNTHESIS
- during photosynthesis, plants use ENERGY, from sunlight, and CO2, from the atmosphere in land based ecosystems/dissolved in water in aquatic ecosystems, to make GLUCOSE and OTHER SUGARS
- some of the sugars produced during photosynthesis are used in RESPIRATION, to release energy for growth
- the rest of the glucose is used to make OTHER BIOLOGICAL MOLECULES, like CELLULOSE (a component of plant cell walls)
- these biological molecules make up the plants BIOMASS (the mass of living material, can be thought of as the chemical energy stored in the plant)
- energy is transferred through the living organisms of an ecosystem when organisms eat other organisms (think of this as an energy passing system)
- ex, producers are eaten by PRIMARY CONSUMERS, who are eaten by SECONDARY CONSUMERS and they are consumed by TERTIARY CONSUMERS (this is a FOOD CHAIN)
how is biomass measured
- biomass can be measured in terms of the MASS OF CARBON than an organism contains or the dry mass of its tissue per unit area
- dry mass is the mass of the organism with the WATER REMOVED
- the water content of living tissue varies, so dry mass is used as a measure of biomass, instead of wet mass
- to measure the dry mass, a sample of the organism is DRIED, often in an oven at a low temp
- the sample if then weighed at regular intervals (everyday for ex)
- once the mass becomes constant, you can be sure all the water has been removed
- the mass of carbon present is usually 50% of the dry mass
- once the dry mass of the sample has been measured, it can be scaled up to give the biomass/dry mass of the total population or area being investigated
- typical units may be kg,m-2
what is a calorimetry and what is its purpose
- you can estimate the amount of CHEMICAL ENERGY stored in BIOMASS by BURNING THE BIOMASS IN A CALORIMETER
- the amount of heat given off tells you how much energy is in it
- energy is measured in joules or kilojoules
- a sample of dry biomass is burnt and the energy released is used to heat a known volume of water
- the change in temperature of the water is used to calculate the chemical energy of the dry biomass
what is primary production and its formula
- gross primary production is the TOTAL AMOUNT OF CHEMICAL ENERGY CONVERTED FROM LIGHT ENERGY BY PLANTS, IN A GIVEN AREA
- around 50% of the GPP is LOST TO THE ENVIRONMENT AS HEAT, when the plants respire : RESPIRATORY LOSS (R)
- the remaining chemical energy is called the NET PRIMARY PRODUCTION (NPP)
FORMULA
- NPP = GPP - R
- often, primary production is expressed as a rate (the total amount of chemical energy/biomass in a given area, in a given time
- typical units may be kJ ha-1 yr-1 (kilojoules per hectare per year) OR kj m-2 yr-1 (kilojoules per square metre per year)
- when primary production is expressed as a rate, it is called PRIMARY PRODUCTIVITY
- the NPP is the energy available to the plant for growth and reproduction, the energy stored in the plants biomass
- it is also the energy available to the organisms at the next stage in the food chain (the next trophic level), these include herbivores and decomposers
what is net production in consumers
- consumers also store chemical energy in their biomass
- consumers get energy by INGESTING PLANT MATERIAL or ANIMALS THAT HAVE EATEN PLANT MATERIAL
- however, not all the chemical energy stored in the consumers food is transferred to the next trophic level, around 90% of available energy is LOST in various ways
- not all food is eaten (ex, bones) so the energy it contains is NOT taken in
- for all the parts that ARE ingested, some are indigestible and egested as faeces and the chemical energy stored in these parts is lost to the environment
AND some energy is lost to the env through RESPIRATION to EXCRETION OF URINE - the energy thats left after all this is stored in the consumers biomass and IS available to the next trophic level, this energy is the consumers NET PRODUCTION
FORMULA
- N = I - (F+R)
- N = net production
- I = chemical energy in ingested food
- F = chemical energy lost in faeces and urine
- R = energy lost through respiration
- the net production of consumers can also be called SECONDARY PRODUCTION or SECONDARY PRODUCTIVITY when expressed as a RATE
what is the efficiency of energy transfer
FORMULA
- % efficiency of energy transfer = (net production of trophic level / net production of previous trophic level) x100
- as you move UP a food chain (producers ->consumers_
what are food chains, food webs and decomposers
- food chains and food webs show how energy is transferred through an ecosystem
- food chains show SIMPLE LINES OF ENERGY TRANSFER
- each stages in a food chain is called a TROPHIC LEVEL
- food webs show lots of food chains in an ecosystem and how they OVERLAP
- decomposers, like fungi, are also part of food webs and they break down dead or undigested material, allowing nutrients to be recycled
how can we increase efficiency
- most farming practices aim to increase the amount of energy that is available for HUMAN CONSUMPTION, this means INCREASING THE NET PRIMARY PRODUCTION (NPP) of CROPS and the NET PRODUCTION (NP) of LIVESTOCK
- the energy lost to other organisms, like pests, can be REDUCED through the SIMPLIFICATION OF FOOD WEBS
- the energy lost through the RESPIRATION OF LIVESTOCK can be reduced
how can food webs simplified
- PESTS are ORGANISMS THAT REDUCE THE AMOUNT OF ENERGY AVAILABLE FOR CROP GROWTH and THEREFORE THE NPP OF CROPS, this ultimately REDUCES the amount of ENERGY available for HUMANS
- by SIMPLIFYING the FOOD WEB, like getting rid of food chains that dont involve humans, energy losses will be REDUCED and the NPP of the crop will INCREASE
what are crops
crops are plants which are grown on a LARGE SCALE for the BENEFIT OF HUMANS, like for human consumption
what is livestock
animals which are bred for their produce, like milk, or for human consumption
how can farmers reduce pest numbers
- farmers need PEST CONTROL to get rid of pests
- farmers can reduce pest numbers using CHEMICAL PESTICIDES
- insecticides kill insect pests that eat and damage crops
- killing insect pests means LESS BIOMASS is LOST from CROPS, so they grow to be larger, which means NPP is greater
- herbicides kill WEEDS
- this can REMOVE DIRECT COMPETITION with the crop for energy from the sun
- weeds also compete with the crop for WATER, SPACE and NUTRIENTS
- it can also REMOVE the PREFERRED HABITAT or FOOD SOURCE of the insect pests, helping to FURTHER REDUCE THEIR NUMBERS and SIMPLIFY THE FOOD WEB
how can biological agents reduce the numbers of pests
- they REDUCE the number of PESTS, so CROPS LOSE LESS ENERGY and BIOMASS and this INCREASES THE EFFICIENCY OF ENERGY TRANSFER TO HUMANS
- parasites live in or lay their eggs on a pest insect
- parasites either KILL THE INSECT or REDUCE ITS ABILITY TO FUNCTION, ex - some wasp species lay their eggs inside caterpillars and the eggs hatch and kill the caterpillars
- pathogenic (disease causing) bacteria and viruses are used to kill pests, ex - the bacterium bacillus thuringiensis produces a toxin that kills a wide range of caterpillars
what is the advantage of farmers using integrated systems that combine both chemical and biological methods
- the combined effect of using both can REDUCE PEST NUMBERS EVEN MORE than neither method alone, meaning NPP is increased even more
how can respiratory loss be reduced
- one way that farmers INCREASE the NET PRODUCTION of their LIVESTOCK is by CONTROLLING THE CONDITIONS THAT THEY LIVE IN, so that MORE OF THEIR ENERGY is used for GROWTH and LESS IS LOST THROUGH RESPIRATION (and activities which increase the rate of respiration)
- movement increases the rate of respiration, so animals may be kept in pens where their movement is restricted
- the pens are often INDOORS and KEPT WARM, so LESS ENERGY IS WASTED BY GENERATING BODY HEAT
- this means that MORE BIOMASS is produced and MORE CHEMICAL ENERGY can be stored, INCREASING NET PRODUCTION and the EFFICIENCY OF ENERGY TRANSFER to HUMANS
- the benefits are that MORE FOOD CAN BE PRODUCED in a SHORTER PACE OF TIME, often at a LOWER COST
- however, enhancing net production by KEEPING ANIMALS IN PENS RAISES ETHICAL ISSUES
- ex, some people think that the conditions intensively reared animals are kept in cause the animals pain, distress or restrict their natural behaviour and therefor its shouldn’t be done
what is the purpose of introducing natural predators to the ecosystems
- to eat the pest species, ex ladybirds eating aphids
- this is useful but doesnt really simplify the food web
what is the role of microorganisms in food webs and ecosystems
- microorganisms, like bacteria and fungi, are an important part of FOOD WEBS and ECOSYSTEMS
- many are SAPROBIONTS
- SAPROBIONTS FEED ON THE REMAINS OF DEAD PLANTS AND ANIMALS and on their WASTE PRODUCTS (faeces and urine), breaking them down, this makes them a TYPE OF DECOMPOSER and it allows important chemical elements in the remains and waste to be recycled
- SAPROBIONTS SECRETE ENZYMES and DIGEST THEIR FOOD EXTERNALLY, then they ABSORB THE NUTRIENTS THEY NEED. this is known as EXTRACELLULAR DIGESTION and during this process, organic molecules are broken down into inorganic ions
- obtaining nutrients from dead organic matter and animal waste using extracellular digestion is known as SAPROBIOTIC NUTRITION
what is mycorrhizae
- some FUNGI form SYMBIOTIC relationships (when 2 species live closely together and one or both of the species depend on the other for survival) with the ROOTS OF THE PLANT -> these relationships are known as MYCORRHIZAE
- the FUNGI are made up of long, thing strands called HYPHAE, which connect to the plants roots
- the HYPHAE greatly INCREASE the SURFACE AREA of the PLANTS ROOT SYSTEM, helping the plant to ABSORB IONS FROM THE SOIL WHICH ARE USUALLY SCARCE, like phosphorous
- HYPHAE also INCREASE the UPTAKE OF WATER by the plant
- in turn, the FUNGI OBSTAIN ORGANIC COMPOUNDS, like GLUCOSE, from the PLANT
explain the nitrogen cycle
BASICS
- plants and animals need NITROGEN to make PROTEINS and NUCLEIC ACIDS (DNA+RNA)
- the atmosphere is made up of 78% nitrogen gas, but plants and animals cant use it in that form because they need bacteria to covert it into nitrogen-containing compounds first
NITROGEN FIXATION
- when nitrogen gas in the atmosphere is turned into NITROGEN-CONTAINING COMPOUNDS
- biological nitrogen fixation is carried out by bacteria like RHIZOBIUM, which turns NITROGEN into AMMONIA, which goes onto form ammonium ions in solution that can be used by plants
- RHIZOBIUM are found inside root nodules (growths on the roots) of LEGUMINOUS plants (like peas, beans and clover)
- they form a MUTUALISTIC relationship with the plants - they provide the plants with NITROGEN COMPOUNDS and the plants provide them with CARBOHYDRATES
- other nitrogen fixing bacteria are found in the soil
AMMONIFICATION
- when NITROGEN COMPOUNDS from DEAD ORGANISMS are turned into AMMONIA by SAPROBIONTS, which goes on to form AMMONIUM IONS
- ANIMAL WASTE (faeces and urine) also contain NITROGEN COMPOUNDS, these are also turned into AMMONIA by SAPROBOINTS and go on to form AMMONIUM IONS
NITRIFICATION
- nitrification is when AMMONIUM IONS in the SOIL are CHANGED into NITROGEN COMPOUNDS that can then be used by plants (nitrates)
- first nitrifying bacteria called NITROSOMONAS change AMMONIUM IONS -> NITRITES
- then other nitrifying bacteria called NITROBACTER change NITRITES -> NITRATES
DENITRIFICATION
- denitrification is when NITRATES IN THE SOIL ARE CONVERTED INTO NITROGEN GAS BY DENITRIFYING BACTERIA - they use nitrates in the soil to carry out respiration and produce NITROGEN GAS
- this ^ happens under anaerobic conditions (where there is NO OXYGEN), like in WATERLOGGED SOILS
- other ways that nitrogen gets into an ecosystem are by LIGHTNING (which fixes atmospheric nitrogen into nitrogen oxides) OR by ARTIFICIAL FERTILISERS (they are produced from atmospheric nitrogen on an INDUSTRIAL SCALE in the HARBER PROCESS)
describe the phosphorous cycle
- plants and animals need phosphorous to make BIOLOGICAL MOLECULES, like PHOSPHOLIPIDS (make up cell membranes), DNA and ATP
- phosphorous is found in rocks and dissolved in the oceans in the form of phosphate ions
- phosphate ions dissolved in water in the soil can be assimilated (absorbed and then used to make more complex molecules) by plants and other producers
PROCESS
- phosphate ions in rocks are released into the soil by weathering
- phosphate ions are taken into the plants through roots, mycorrhizae greatly INCREASE the rate at which phosphorous can be ASSIMILATED
- phosphate ions are TRANSFERRED through the food as animals eat the plants and are in turn eaten by other animals
- phosphate ions are LOST from the ANIMALS in WASTE PRODUCTS
- when PLANTS and ANIMALS DIE, SAPROBIONTS are involved in BREAKING DOWN the ORGANIC COMPOUNDS, releasing phosphate ins into the soil for assimilation by plants and these microorganisms also release the phosphate ions from URINE and FAECES
- WEATHERING OF ROCKS also RELEASES PHOSPHATE IONS into seas, lakes and rivers. this is taken up by AQUATIC PRODUCERS, like algae and passed along the food chain to birds
- the WASTE produced by the SEA BIRDS is known as GUANO and contains a HIGH PROPORTION OF PHOSPHATE IONS. guano RETURNS a SIGNIFICANT AMOUNT of PHOSPHATE IONS to SOILS (especially in coastal areas) and it is often used as a NATURAL FERTILISER
what can farmers do to the soil to increase the productivity of crops
- they can add extra nutrients, like nitrogen and phosphorous
- this could cause environmental problems because there needs to be a balance between adding to much and too little
how does the loss of nutrients take place
- crops take in minerals from the soil as they GROW and use them to BUILD THEIR OWN TISSUES
- when crops are HARVESTED, they are REMOVED from the field where they are grown instead of being allowed to die and decompose there
- this means that the mineral ions that they contain, like phosphates and nitrates, are NOT returned to the soil by DECOMPOSERS in the nitrogen or phosphorous cycles
- phosphates and nitrates are lost from the system when animals or animal products are removed from the land
- animals eat grass and other plants, taking in their nutrients
- when they are taken somewhere else for their slaughter or transferred to a different field, the nutrients aren’t replaced through their remains or waste products
how does using fertilisers effect the ecosystem
- adding fertile replaces lost minerals, so more energy from the ecosystem can be used for growth, INCREASING THE EFFICIENCY OF ENERGY TRANSFER
- fertilisers can be artificial or natural
- artificial fertilisers are inorganic - they contain pure chemicals, like ammonium nitrate, as powders or pellets
- natural fertilisers are ORGANIC MATTER, they include manure, composted vegetables, crop residues (plants of left over after the harvest) and sewage sludge
what are environmental issues which surround the use of fertilisers
- sometimes, more fertilisers is applied than the plants need or are able to use at a particular time and this can lead to the fertilisers LEACHING into waterways
- leaching = is when water-soluble compounds in the soil are washed away, by rain or irrigation systems for ex and they are often washed into nearby ponds and rivers which can lead to EUTROPHICATION
- inorganic ions in chemical fertilisers are relatively solouble
- this means excess minerals that aren’t used immediately are more likely to leach into waterways
- leaching is also more likely to occur if the fertiliser is applied just BEFORE heavy rainfall
- leaching is LESS LIKELY with natural fertilisers because the nitrogen and phosphorous are still contained in organic molecules that need to be decomposed by microorganisms before they can be absorbed by plants
- this means that their release into the soil for UPTAKE by plants is MORE CONTROLLED
- the leaching of PHOSPHATES is LESS LIKELY than the leaching if NITRATES, because PHOSPHATES ARE LESS SOLUBLE IN WATER
- using fertilisers may also change the balance of nutrients in the soil and too much of a certain nutrient can cause crops and other plants to die
describe the steps in eutrophication
- eutrophication is caused by excess nutrients
- mineral ions leached from fertilised fields stimulate the rapid growth of algae in ponds and rivers
- large amounts of algae block light from reaching plants below
- eventually the plants die because they are unable to photosynthesise enough
- bacteria feed on the dead plant matter and the increased numbers of bacteria REDUCE 02 CONC in the WATER by carrying out AEROBIC RESPIRATION
- fish and other aquatic organisms die as there isn’t enough dissolved oxygen
