Energy Transfers In And Between Organisms Flashcards
What is Photosynthesis?
- Reaction in which light energy is used to produce glucose in plants.
- Water + Carbon Dioxide = Glucose + Oxygen
What are the two stages of Photosynthesis?
- Light dependent reaction
- Light independent reaction
What is the rate of Photosynthesis determined by?
- Carbon dioxide concentration, light intensity and temperature.
What ways are chloroplasts adapted for Photosynthesis?
- Stacks of Thylakoid membranes called Grana = large surface area for the attachment of chlorophyll, electrons and enzymes.
- Network of proteins = hold the chlorophyll in a very specific manner = absorb maximum amount of light.
- ATP synthase channels = selectively permeable = proton gradient = synthesis of ATP.
- DNA and Ribosomes = synthesis proteins for the light dependent reaction.
Light Dependent reaction = What is Photoionsation?
(Non-cyclic Photophosphorlation)
- Photons of light are absorbed by PSII
- Energy excites two electrons to a higher energy level
- 2e- move along the e- transfer chain to PSI
Light Dependent reaction = What is Photolysis?
(Non-cyclic Photophosphorlation)
- The splitting of water with light
- H20 -> 2H+ + 0.5o2 + 2e-
- One molecule of water = 4 photons to split
- Electrons produced replace lost electrons in PSII
- Protons move into stroma creating a proton gradient
Light Dependent reaction = How does energy from electrons produce ATP?
(Non-cyclic Photophosphorlation)
- Excited electrons move along electron transfer chain = loosing energy.
- Lost energy provide energy for active transport of H+ ions from a low to high gradient into the Thylakoid space from the stroma across the proteins = proton pump created.
- High concentration of H+ ions in thylakoid space allows a facilitated diffusion through ATP synthase into the stroma.
- Energy from this combines ADP and Pi to from ATP.
Light Dependent reaction = How is reduced NADP made from energy from the electrons?
(Non-cyclic Photophosphorlation)
- Light energy is absorbed by PSI
- 2e- becomes excited and leaves PSI to form NADP
- Protons int eh stroma combine with NADP or make reduced NADP.
Light Dependent reaction = Cyclic Photophosphrolation
- Light energy excites 2e- in PSI, move down electron transfer chain creating proton gradient and energy for active transport of H+ ions into Thylakoid membrane.
- ATP synthase makes ATP, electrons return to PSI.
What is the Chemiosmotic theory?
Process of electrons flowing down the electron transfer chain to create a proton gradient to drive ATP synthesis.
Light Independent reaction = What happens in Carbon dioxide fixation/stage 1?
- CO2 diffuses through the stomata fixed with ribulose bisphosphate (RuBP) = carboxylation.
- Enzyme Rubisco needed.
- 6 carbon sugar is formed first, very unstable so it forms 2 molecules of glycerate-3-phosphate.
Light Independent reaction = What happens in the Reduction phase/stage 2?
- The 2 molecules of glycerate-3-phosphate contain a -COOH group = acid.
- Reduced NADP from the light dependent reaction then reduced the glycerate-3-phosphate, with energy provided from ATP.
- Forms 2 molecules of triose phosphate
Light Independent reaction = What happens in the Regeneration of RuBP phase/stage 3?
- 5 molecules of triose phosphate are used in order to regenerate 3 molecules of ribulose bisphosphate.
- Remaining ATP from light dependent reaction is used to do this.
- The other 1 molecule of triose phosphate goes towards making glucose.
Light Independent reaction = What happens int eh Organic molecule production/stage 4?
- 2 molecules of triose phosphate can combine to form the intermediate hexose sugar (fructose 1,6 bisphosphate)
- 6 turns of the Calvin Cycle needed in order to produce one molecule of glucose per molecule of CO2.
What is the Lollipop experiment - Melvin Calvin?
- Radioactive carbon added to algae to be incorporated during photosynthesis.
- After a set period of time, algae is killed in alcohol to prevent further reaction,
What is a limiting factor?
In photosynthesis?
- A factor that decreases of limits the rate of Photosynthesis
- Rate of physiological process will be limited by the factor which is in shortest supply.
What is the Compensation point?
- When carbon dioxide released during respiration is equal to that taken up by Photosynthesis.
How does light affect the rate of Photosynthesis?
- As light intensity increases = rate of photosynthesis increases
- More Photons of light = greater the number of chlorophyll molecules are ionised and more ATP and NADPH are generated.
- Will be limited by some other factor
- Very very high light intensity = chlorophyll may become damaged
How does Carbon dioxide affect the rate of Physical?
- As CO2 increases = rate of Photosynthesis increases
- Plateaus when the maximum rate of fixation is reached
How does temperature affect the rate of Photosynthesis?
- Light independent reactions = DEPENDENT of temperature = reaction is catalysed by enzymes
- As temperature increases up to the optimum temp = rate of Photosynthesis increases
- Aprox. Doubles for every 10’C
- Aboce optimum temperature rate decreases as enzymes denature
What are the four stages of respiration?
1) Glycolysis - conversion of glucose (6C) to pyruvate (3C) (anaerobic)
2) Link reaction - Pyruvate is converted yo acetyl-coenzyme A (2C)
3) Krebs cycle - cycle of oxidation and reduction reactions that yield ATP and reduced NAD and reduced FAD
4) Oxidative phosphorylation- electron transfer chain using reduced NAD and FAD to from ATP and water
Where does each stage happen?
1) Glycolysis = cytoplasm of cell
2) Link reaction = matrix of mitochondria
3) Krebs cycle = matrix of the mitochondria
4) Electron transfer chain = proteins of the membrane of the crista
What happens in glycolysis?
- ATP adds one phosphate group to a glucose molecule = glucose phosphate (6C)
- Another phosphate group is added to glucose phosphate to form hexose bisphosphate (6C) - requires energy from ATP
- Hexose bisphosphate (6C) is then broken down into 2 molecules of triose phosphate (3C)
- Each triose phosphate is oxidised by NAD to form reduced NAD - 2 molecules of reduced NAD from 1glucose
- Each molecule of triose phosphate (3C) is converted to pyruvate (3C) - due to the removal of both phosphate groups by ADP to form ATP - each triose phosphate form 2 ATP
- If oxygen present - pyruvate transfers from the cytoplasm to the matrix of the mitochondria for the link reaction and Krebs cycle
- If oxygen not present - pyruvate is converted to lactate or ethanol and CO2 in anaerobic respiration
What are the main products of Glycolysis?
- 2 reduced NAD (NADH + H+)
- 2 Pyruvate
- 2 ATP (net)
What happens in the Link reaction?
- 2 Molecules of pyruvate are actively transported into the mitochondria
- The pyruvate (3C) is the decarboxylated by decarboxylase where a CO2 is removed and dehydrogenated where oxidised NAD forms reduced NAD with the lost H+
- The acetate formed then combines with coenzyme A to form a molecule of acetyl coenzyme A (2C)
- Per glucose molecule 2 molecules of acetyl coenzyme A are formed and 0 ATP
- Acetyl coenzyme A now enters the Krebs cycle
What is the quick equation for the link reaction?
2 (Pyruvate + Oxidised NAP + CoA —> Acetyl CoA + Reduced NAD + CO2)
What happens in the Krebs cycle?
- CoA is used to transport acetate to the Krebs cycle
- Acetate (2C) combines with oxalocetate (4C) forming citrate (6C)
- Citrate is decarboxylated and dehydrogenated, loosing a CO2 and 2 hydrogens, accepted by NAD to form reduced NAD
- The 5C compound is also decarboxylated and dehydrogenated forming a 4C molecule, again NAP accepts the lost hydrogen forming another reduced NAD
- 4C gives a phosphate group to ADP, leading to production of ATP, and forms a second 4C
- The second 4C is converted to another 4C, two hydrogens are released and accepted by FAD making reduced FAD
- The third 4C is dehydrogenated, re-forming oxalocetate, and another pair of hydrogens are released making another reduced NAD
What happens in Oxidation Phosphorylation?
- Hydrogen atoms are released from reduced NAD and reduced FAD as they are oxidised back into NAD and FAD
- The hydrogen atoms split into protons (H+) and electrons (e-)
- The electrons move down the electron transfer chain losing energy at each carrier
- This energy is used to create a proton pump form the matrix to the intermebrane space
- Creating a electrochemical gradient
- Protons move down this gradient through ATP synthase to make ATP = chemiosmosis
- At the end of the transfer chain, protons, electrons and oxygen combine to form water. Oxygen is the final electron acceptor
How much ATP is formed in respiration?
32
What happens in anaerobic respiration?
- Reduced NAD transfers its hydrogens to pyruvate to from lactate
- Pyruvate is reduced to lactate by the enzyme lactate dehydrogenase
- Pyruvate is the hydrogen acceptor
- Oxidised NAD is now available to accept electrons and protons so glycolysis can continue
Pyruvate + reduced NAD —> lactate + oxidised NAD
What happens in the metabolisation of lactate?
EITHER:
- Lactate is oxidised back to pyruvate which can be channelled into the Krebs cycle for ATP production
- Lactate is converted into glycogen for storage in the liver
What is oxygen debt?
- Oxidation of lactate back to pyruvate needs extra oxygen, this extra oxygen is referred to as oxygen debt
- it is why animals breathe deeper and faster after exercise
What happens in fermentation?
- Pyruvate is decarboxylated into ethanol, producing CO2
- Reduced NAD transfers its hydrogen to ethanal to from ethanol
- Ethanal is reduced to ethanol by the enzyme alcohol dehydrogenase
- Ethanal is the hydrogen acceptor
- Ethanol cannot be further metabolised, as it is a waste product
Pyruvate + reduced NAD —> ethanol + carbon dioxide + oxidised NAD
What is an autotroph?
Photosynthetic organisms that use sunlight to produced their own food = primary producers.
What is a heterotroph?
Organisms that cannot synthesise their own food = all animals.
Why is 90% of chemical food energy lost to surroundings?
- Uneaten parts e.g. bones
- Decay of dead material
- Excretion
- Exothermic reactions e.g. heat lost in respiration
How can percentage efficiency be calculated?
Energy available after the transfer
Percentage efficiency = ————————————————— x100
Energy available before the transfer
What is Net Primary Productivity (NPP) ?
The rate at which energy is transferred into the organic molecules that makeup new plant biomass, the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.
What is Gross Primary Productivity (GPP) ?
The rate at which plants produce organic molecules by photosynthesis.
Equation for NPP?
NPP = GPP - R
Where R = respiration
Net production of consumers - secondary production equation?
N = I - (F+R)
N = net production
I = chemical energy store of ingested food
F = chemical energy lost in faces and urine
R = energy lost in respiration
What is a pyramid of numbers?
- The number of organisms at each trophic level
- Width of the box indicates the number of organisms at each trophic level
What are the disadvantages of pyramids of numbers?
- Can result in upside down pyramids
- No measurement of energy movement is shown
What is a pyramid of biomass?
- Shows the dry biomass of the organisms at each trophic level
- Better idea of the quantities of the plant or animal material at each level on the food chain
What’s the disadvantages of pyramids of biomass?
- Organisms have to be dry and need to be killed to do that
What’s a pyramid of energy?
- A model that shows the flow of energy from one tropic level to the next in a ecosystem, taken at a given time
What’s the disadvantages of pyramids of energy?
- Only shows the energy flow at one given moment in time
How can farming practices increase productivity?
- Meat production:
- Put animals in small pens to reduce muscle contraction
- Heat the are so less energy is lost to metabolic processes
- Pesticides, antibiotics, vaccines
- protein based diets
How can farming practices increase productivity?
- Monoculture production:
- Herbicides and pesticides
- Remove hedgerows
What is the nitrogen cycle?
- 79% of air is nitrogen gas
- Organisms can’t use nitrogen gas as it is inert
- Instead : Nitrate ions, Ammonia/ammonium absorbed by active transport
What are the three types of nitrogen fixation?
- Biological = microbes
- Atmospheric = lightning
- Industrial = hater process
What are the two ways biological nitrogen fixation occurs?
- Free-living bacteria e.g. Azotobacter : reduce nitrogen to form amino acids, when they die the nitrogen rich compounds are released.
- Symbiotic bacteria e.g. Rhizobium, in the root nodules of legumes. Rhizobium contains enzymes called nitrogenase that converts nitrogen and hydrogen to ammonia.
- The ammonia is used to make amino acids which the legumes can use to make proteins in return for supplying bacteria with carbohydrates for respiration
What is decomposition?
- Saprophytes that break down the molecules in excretions and dead organisms into ammonia
What is ammonification?
- Production of ammonia from organic nitrogen containing compounds like amino acids, urea, nucleic acids, vitamins and proteins
- Saprobiotic mircroorganims
- Forms ammonia ions in the soil
What is nitrification?
- Most ammonia produced by decay is converted into nitrates.
- Accomplished by : nitrifying bacteria oxidising ammonia to nitrates and nitrites to nitrates
What is denitrification?
- Anaerobic denitrifying bacteria converts nitrates to nitrogen, occurs when there is a lack of oxygen.
What happens in the phosphate cycle?
- Phosphate is released from sedimentary rocks as a result of weathering, as well as the decay of bones, shells and the excreta of some birds.
- Decomposers break down organic molecules to release phosphate ions into water or soil.
Why are fertilisers needed in agricultural ecosystems?
- They can be used to replace the nutrients that are lost through agriculture, and can increase crop yield.
Why does adding fertiliser only increase the productivity of agriculture to a certain point?
- The nitrates and phosphates are no longer the limiting factor for the growth of the crops.
What is leaching?
- The loss of water-soluble nutrients form the soil, due to rain and irrigation.
What are the sequence of consequences of eutrophication?
- Algal blooms
- Block sunlight = Kills off other aquatic plants
- When the algae dies, it is broken down by bacteria which uses the oxygen up, creating anaerobic conditions
