5: Energy Transfers In and Between Organisms

note reduced NAD= NADH but ms preferes reducdedf NAD and reduced NADP is the same as NADP

structure of chloroplast

grana- stacks of thylakoids to increase SA
thylakoids- where light dependent stage of photosynthesis takes place
stroma- fluid-filled matrix where light-independent stage takes place, also includes starch grains

light dependent reaction

1. photoionisation:

• light absorbed by chlorophyll molecules in PSII

• this excites electrons so they leave PSII and are absrobed by PSI electron transport chain (protein complexes in inner mitochondria membrane) do a series of redox reactions

• chlorophyl molecule becomes positively charged(oxidised) causing step 2

2. photolysis:

• splitting water using light

• 2H₂O→4H⁺ (4 protons), + O₂ + 4e^-

• the oxygen diffuses out of the stomata or is used in respiration, the 4 electrons replace those lost from PSII and the protons diffuse down conc into the stroma to create a proton gradient(chemiosmosic/chemiosmotic theory)

3. for non-cyclic photophosphorylation: electrons in electron transport chain are taken up by NADP as well as protons to form reduced NADP which moves into stroma for light independent reaction. ATP is synthesised from ADP and Pi using ATP synthase. products: ATP, oxygen, reduced NADP

4. cyclic photophosphorylation: only uses PSI so no photolysis, but photoionisation occurs in PSI electrons leave PSI and move down ETC releasing energy for active transport of H⁺ ions. electrons at PSI constantly flow back/are recycled so no reduced NAPD or oxygen is produced, and only small amounts of ATP

light independent reaction/Calvin Cycle

1. carboxylation:

• CO₂ enters the leaf and diffuses into stroma

• it combines with RuBP(5 carbons) to make an unstable 6C compound using rubisco enzyme

• this splits into 2 molecules of 3C compounds called gylcerate 3-phosphate(GP)

2.reduction

• GP is reduced into a different 3C compound called triose phosphate(don’t shorten)

• H⁺ ions from reduced NADP and ATP from light-dependent reaction are needed, so ATP becomes ADP+Pi(releasing energy)

3.regeneration

• 5 out of 6 triose phosphate molecules are used to regenerate RuBP.

• the rest of the ATP from light dependent reaction is also used to regenerate RuBP so it becomes ADP +Pi(released energy)

6 calvin cycles are needed to produce one molecule of glucose

products: NADP, ADP, Pi go back to light dependent reaction. TP is used to build organic compounds e.g glucose, amino acids, lipids, RuBP is regenerated and reused in calvin cycle

limiting factors for photosynthesis

• light intensity and wavelength: higher→more energy to excite electrons→too high may damage pigments, pigments mostly absorb red and blue and reflect green

• temperature: low-ezymes slow, high-denature

• carbon dioxide: high increases photosynthesis, until past stomato close

• availability of water: increases photosynthesis, unless roots are waterlogged and can’t respire so no ATP for active transport and chlorosis(no Mg)

define biomass, and how we measure energy stored in it

biomass- mass of carbon/dry mass of tissue per given area per given time. the energy stored can be estimated by using bomb calorimetry by burning sample in oxygen and submerging the sample in biomass and calculating the change in water temperature

the sample must be dry mass as wet mass varies to much. We ensure it is dry by heating at a low temperature(so it doesn’t burn away) in an oven measure mass and then reheat until mass remains constant

define % efficiency of energy transfer, net primary production, gross primary production, and net production of consumers

% efficiency= energy available after the transfer/energy available before the transfer x100

net primary production(NPP)- chemical energy stored in plant biomass after respiratory losses to the environment have been taken into account NPP=GPP-R

gross primary production(GPP)- the chemical energy stored in plant biomass in a given area or volume

net production of consumers(N) N=I-(F+R) I chemical energy in ingested food, F is chemical energy lost to environment in faeces and urine and R is respiratory losses to environment

energy can be lost as heat through respiration

how farmers increase crop growth

• increase CO₂ using CO₂ generators

• increases light intensity with blue/red LED lights

• greenhouses to trap heat and fans/automatic windows or ac systems for cooling

cells in meristems(roots and shoots) divide by mitosis to grow

RP7: Chromatography of plant pigments, method and factors affecting

method:

1. draw a start line 1cm up from the filter in pencil

2. crush a section of leaf +5ml acetone using a pestle and mortle

3. use a capillary tube to extract some pigmetn and blot it into the pencil line

4. suspend the paper into the solvent, so the liquid isn’t above the pencil line and leave the paper until the solvent is near the top

5. remove the paper and calculate the Rf value from the center of the spot. Rf=(distance travelled by solute/distance travelled by solvent)

factors:

affinity- pigments with lower affinities travel further up the page
solubility- pigments that are more soluble travel faster up the pag

RP8: named factors affect on the rate of dehydrogenase activity in chloropast extracts method and theory

method:

1. remove stalks from the leaf and grind the sample using a pestle and mortar and place into a chilled isotonic solution

2. use a muslin cloth and funnel to filer it into a beaker. keep this beaker in an ice bath/chilled

3. centrifuge at high speeds for 10 minutes to separate chloroplasts into the pellet

4. remove the supernatant and add the pellet to the chilled isotonic solution

5. set colorimeter to a red filter, zero/standardised it using chlorplast extract and distilled water

6. place 5cm3 chloroplast extracts+5cm3 DCIPIP in test tubes at 30cm from a lamp for 5 minutes each, measure absorbance on colurimeter every 30seconds

7. repeat at different distances from the lamp

conclusion:

• degenerase enzyme catalyses electrons being accepted by NADP in the light dependent reaction,

• when DCPIP dye is added, electrons are accepted by the DCPIP instead, so it turns blue to colourless

• light intensity decreasing, decreases photosynthesis, so less electrons released by chlorophyll→less accepted by DCPIP→takes longer to turn froom blue to colourless

• when DCPIP is blue, absorbance is higher

define producer, consumer, food chain, food web, biomass

producer- organisms that manufacture organic substances through photosynthesis

consumer- organisms that get their energy from consuming other organisms. Primary-consumers producers, secondary-eats primary, tertiary-eats secondary

food chain- feeing relationship where producers are eaten by primary consumers, who are eaten by secondary consumer ect. arrows represent direction of energy flow, and each stage is a trophic level

food web- many food chains linked together in a single habitat

biomass- the total mass of living material in a specific area in a given time

nitrogen cycle

phosphorus cycle

mycorrhizae

• this is the mutalistic relationship between plants and fungi

• fungi act as extensions to the plant’s root system and increase the surface area for the absorption of water and mineral

• the plant provides glucose/carbohydrates, a protected habitat

natural vs artificial fertisers and the need for them

natural/organic- made from dead and decaying plants and animals, or animal wastes such as bone meal or manure

artificial/inorganic- mined from rocks and deposits, converted into different forms and blended in the correct proportion for a specific crop, always contain NPK

need for fertilisers: plants need minerals from the soil, and most crops are intensively farmed so they minerals needd to be replenished so they don’t become limiting facors to plant growth

effects of nitrogen-containing fertilisers

reduced species diversity: nitrogen rich soils favour the growth of fast growing species e.g nettles and grasses, so they out-compete otehr species and they die

leaching: rainwater dissolves soluble nutrients, which find their way into streams and rivers, where they have a harmful effect on humans drinking it or marine life and also causes eutrophication

eutrophication:

1. rivers and lakes have naturally low conc of nitrate, so it is a limiting factor for plant and algea growth

2. due to leaching, nitrate conc increases so plant and algae populations grow

3. algal bloom-upper layers of water becomes densely populated with algae preventing light penetrating to the depths

4. light becomes limiting factor for plants at low etphs so they die

5. dead plants allows saprobiontic bacteria to grow using dead plants as food

6. saprobionts use o2 to respire, increasing oxygen demand

7. this reduces oxygen conc in the water and releases nitrates, so oxygen becomes a limiting factor for aerobic organisms e.g fish and they die

8. anaerobic organisms have less competition, so their populaitons rise. They decompose dead material releasing more nitrates and toxic wastes making the water putrid

glycolysis

• occurs in the cytoplasm outside the mitochondria

• reverse of the calvin cycle

1. glucose is phosphorylated by adding 2Pi from 2ATP to make it more reactive. It splits into 2 molecules of Triose Phosphate(3carbons)

2. Triose phosphate is oxifised to pyruvate. 2NAD collects H+ and is reduced to 2NADH

3. 4ATP are produced but but 2 are used at the start, so products are 2ATP, 2 pyruvate, 2reduced NAD

link reaction

• this occurs in the mitochondrial matrix via active transport

• 2 link reactions for 1 glucose bc 1 glucose makes 2 pyruvate

1. the 2 molecules of pyruvate are actively transported into the mitochondria

2. the enzyme carboxylase removes a molecule of CO₂ and H from pyruvate to make it acetate(2 carbons)

3. acetate combines with coenzyme A to make acetyl coenzyme A\

4. total products for 1 link reaction-1 CO₂, 1 reduced NAD

krebs cycle

• in the mitochondrial matrix

1. acetate is removed from coenzyme A and combines with a 4carbon molecule to form a 6 carbon molecule

2. coenzyme A is released and recycled back to link reaction

3. 6 carbon molecule undergoes a series of redox reactions and is converted back into the 4C molecule so the cycle can continue

4. during these reactions carbon dioxide is released(decarboxylated), hydrogens are also released(dehydrogenation) and ATP is directly produced by substrate level phosphorylation

• one turn of the krebs cycle prodcues 3xreduced NAD, 1xreduced FAD, 1xATp, 2xCO₂(waste)

• there are 2 turns per glucose molecule

oxidative phosphorylation

1. reduced NAD and reduced FAD donate electrons to the electron transport chain

2. electrons pass along a series of electron carriers, releasing energy

3. this enrgy is used to actively transport H⁺ from the mitochondrial matrix into the intermembrane space

4. this creates an electrochemical gradient accross the inner mitochondrial membrane

5. hydrogen ions diffuse down the electrochemical gradient(move from inner membrane to matrix) through ATP synthase, providing energy for phosphorylation of ADP + Pi to form ATP -chemiosmosis

6. oxygen acts as a the final electron acceptor combining with electrons and hydrogen to form water

• oxidative phosphorylation occurs in the inner mitochondrial membrane

anaerobic respiration

• only glycolysis happens and it roduces a small amount of ATP

plants and yeast:

1. glycolysis to form pyruvate

2. pyruvate loses CO₂ to produce ethanal

3. ethanal accepts hydrogen from reduced NAD, ethanal is reduced to ethanol and reduced NAD is oxidised back to NAD to allow glycolysis to continue

animals:

1. glycolysis produces pyruvate and reduced NAD

2. pyruvate accepts hydrogen from reduced NAd and is reduced to lactate

3. reduced NAD is oxidised back to NAD

why is nad regenerated duringa anerobic repsiration

• NAD is needed as a hydrogen acceptor during glycolysis

• during anaerobic respiration, there is no oxygen to act as the final electron acceptor in oxidative phosporylation

• reduced NAD transfers hydrogen to pyruvate, which regenerates oxidised NAD to be reused allowing ATP production to carry on in glycolysis.

respiration quotient

volume of CO₂ produced/volume of O₂ consumed.

this is 1 for carbohydrates. the RQ value can tell us which biological molecule the cell is primarily breaking down

oxygen debt

• during vigorous exercise the need for ATP increases, so if oxygen suppy doesn’t meet demand anaerobic respiration increases

• lactate accumulates in muscle cells and enters blood stream

• when the exercise is finished, lactate is transported in blood to the liver and converted back into pyrutvate. This requires oxygen

• the pyuvate is oxised in aerobic respiration or used to synthesise glucose

• oxygen

products summary of net products per glucose molecule

for one molecule of glucose:

• one round of glycolysis

• 2 link reactions

• 2 krebs cycles