5: Energy Transfers (Photo/Resp/E transfers & N. Cycles) Flashcards
Describe what happens during photoionisation in the light dependent reaction. [2]
- Chlorophyll absorbs light energy OR Light energy excites/moves electrons in chlorophyll;
- Electron/s are lost **OR ** (Chlorophyll) becomes positively charged;
- Accept electrons go to electron transport/carrier chain for ‘electrons lost’.
Describe the light dependent reaction [6]
- Chlorophyll absorbs light energy and excites electrons
- Electrons removed (Oxidation of chlorophyll) via photoionisation;
- Electrons move along carriers/electron transport chain** releasing energy** (Series of REDOX reactions)
- Energy released (by electrons) used to form proton (electrochemical) gradient;
- H+ ions diffuse through ATP synthase;
- providing energy to join ADP and Pi to form ATP; Photophosphorylation
- Photolysis of water produces 2 protons, 2 electrons and ½ oxygen; electrons regenerate chlorophyll.
- NADP reduced by electrons / electrons and protons / hydrogen;
Name the two products of the light-dependent reaction that are required for the light-independent reaction.
- ATP;
- Reduced NADP;
Accept: NADPH / NADPH2
Proton pumping to form a proton gradient is an example of active transport.
True or False
False:
- Active transport requires ATP!
- Energy for proton pumping is from high energy electrons.
Describe the light independent reaction [6]
- Carbon dioxide combines/reacts with RuBP;
- Produces two glycerate (3- )phosphate/GP using (enzyme) Rubisco;
- GP reduced to triose phosphate;
- Using reduced NADP;
- Using energy from ATP;
- Triose phosphate converted to glucose / hexose / RuBP (ribulose bisphosphate) / other correctly named organic substance;
Where precisely is rubisco found in a cell?
Stroma
Explain why scientists measure the rate of production of oxygen in this investigation. (Rate of photosynthesis) [2]
- Oxygen produced in light-dependent reaction;
- The faster (oxygen) is produced, the faster the light-dependent reaction.
Explain why plants that have more chlorophyll will grow faster than plants with less chlorophyll. [5]
- Have faster production of ATP and reduced NADP;
- (So) have faster / more light-independent reaction;
- (So) produce more sugars that can be used in respiration;
- (So) have more energy for growth;
- Have faster / more synthesis of new organic materials.
ATP is produced in the light dependent reaction, suggest why this is not their (plants) only source of ATP. [4]
- Plants don’t photosynthesis in the dark;
- Not all the parts of the plants photosynthesise;
- Plants require more ATP than is produced in the light dependant reaction;
- ATP used in Active Transport (accept other named processes)
Describe the effect of introducing a herbicide/inhibitor on the electron transport chain (4)
- Reduced transfer of protons across thylakoid membrane OR Reduced chemiosmotic gradient/proton gradient across thylakoid membrane;
- (So) less ATP produced;
- (So) less reduced NADP produced;
- (So) light-independent reaction slows/stops OR Less reduction of GP to triose phosphate;
When producing a chromatogram explain why the origin is marked using a pencil rather than ink.
- Ink and (leaf) pigments would mix
OR - (With ink) origin/line in different position
OR - (With pencil) origin/line in same position
OR - (With pencil) origin/line still visible;
While making a chromatogram, describe the method used to separate the pigments after the solution of pigment had been applied to the origin. [2]
- Level of solvent below origin/line;
- Remove/stop before (solvent) reaches top/end;
Suggest and explain the advantage to plants of having different colour pigments in leaves.
- Absorb different/more wavelengths of light for photosynthesis;
Explain the relationship between stomatal opening and photosynthesis. [2]
- Stomata allow uptake of carbon dioxide;
- Carbon dioxide used in / required for photosynthesis;
What is the equation to calculate the Rf value?
Distance pigment moved from origin / Distance solvent front moved from origin
Describe the process of glycolysis.[5]
- Phosphorylation of glucose using ATP;
- Oxidation of triose phosphate to pyruvate;
- Net gain of ATP;
- NAD reduced;
- Occurs within the cytoplasm
Describe the link reaction [4]
- Occurs in the matrix (mitochondrion)
- Pyruvate oxidised and decarboxylated into Acetate.
- Produces reduced NAD and CO2
- Acetate combines with coenzyme A to produce Acetyl co A
Reject ATP is formed.
NAD is a coenzyme. What is a coenzyme?
- NAD is a dinucleotide (derivative)
- Organic NON-PROTEIN
*Binds to with an enzyme to help catalyse a reaction - often refered to as a carrier molecule
Describe how oxidation takes place in glycolysis and in the Krebs cycle. [4]
- removal of hydrogen/dehydrogenation;
- by enzymes/dehydrogenases;
- Hydrogen accepted by NAD/reduced NAD formed;
- in Krebs cycle, FAD (used as well);
Water is a waste product of aerobic respiration.
Describe how water is formed at the end of aerobic respiration. [2]
- oxygen is terminal/final electron acceptor;
- combines with electrons and protons (to form water);
Explain how the amount of ATP is increased by reactions occurring inside a mitochondrion. [6]
- oxidation of/removal of electrons and H+ from pyruvate
- acetyl CoA / 6 carbon compound; (credit oxidative decarboxylation)
- substrate level production of ATP / ATP produced in Krebs cycle;
- production of reduced NAD / FAD (allow they take up hydrogen);
- **in matrix **of mitochondria;
- electrons fed into electron transport chain / used in oxidative
- (Electrons) pass along carriers/through electron transport chain/through series of redox reactions;
- Energy released as heat;
- Protons pumped into intermembrane space;
- ADP + Pi to ATP using ATP synthase
Describe the roles of the coenzymes and carrier proteins in the synthesis of ATP.
OR
Describe the events of oxidative phosphorylation
[5]
- NAD/FAD reduced / hydrogen attached to NAD/FAD;
- H+ ions/electrons transferred from coenzyme to coenzyme/carrier to carrier (ETC on cristae of inner membrane)
- Energy released (from electrons) through series of redox reactions;
- Energy released used to pump H+/ protons into intermembrane space forming an electro-chemical gradient (of protons);
- H+/ protons flow back through ATP synthase to produce ATP from ADP and phosphate.
(some energy lost as heat)
In many mammals, ‘uncoupling proteins’ help to maintain a constant body temperature during hibernation.
Suggest and explain how.
[2]
- Allow passage of protons/H+;
- (Energy) released as heat;
The mitochondria in muscles contain many cristae. Explain the advantage of this. [2]
AO2 (More / Less)
- larger surface area for electron carrier system / MORE oxidative phosphorylation;
- provide MORE ATP / energy for contraction;
Give two reasons why the respirometer was left for 10 minutes when it was first placed in the water bath.
- Equilibrium reached;
- Allow for expansion (gases/liquids) /pressure change in apparatus;
- Allow respiration rate of seeds to stabilise;
In a respirometer why does the coloured liquid move to the left (towards the organism). [3]
- Oxygen taken up by organism
- Carbon dioxide absorbed by KOH
- Pressure/volume decreases inside
Apart from time, give two measurements a student would have to make to determine the rate of aerobic respiration of seeds in a respirometer in cm3 per hour.
- Distance liquid moves (cm)
- Diameter/radius of the tube (cm)
Explain why a log scale is used to record the number of cells/bacteria. [1]
- Large range/difference/increase in numbers;
- Accept reference to exponential (increase)
Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration. [2]
- Regenerates NAD / Oxidises reduced NAD;
- (So) glycolysis continues;
Malonate inhibits a reaction in the Krebs cycle.
Explain why malonate would decrease the uptake of oxygen in a respiring cell.
[2]
- Less/no reduced NAD/coenzymes OR Fewer/no hydrogens/electrons removed (and passed to electron transfer chain);
- Oxygen is the final/terminal (electron) acceptor;
Explain why converting pyruvate to ethanol is important in allowing the continued production of ATP in anaerobic respiration. [2]
- allows NAD to be recycled / re-formed;
- so that glycolysis continues / so that (more) glucose can be converted to pyruvate
Give two ways in which anaerobic respiration of glucose in yeast is similar to anaerobic respiration of glucose in a muscle cell. [2]
- ATP formed / used;
- pyruvate formed / reduced;
- NAD / reduced NAD;
- glycolysis involved
Give two ways in which anaerobic respiration of glucose in yeast is different from anaerobic respiration of glucose in a muscle cell. [2]
- ethanol / alcohol formed by yeast whereas lactate by muscle cell;
- CO2 released by yeast but not by muscle cell;
Name the two substances produced by anaerobic respiration in humans.
- Lactate;
- ATP;
A: Pyruvate
B: Reduced NAD / NADH/ NADH2
C: Coenzyme A
D: Acetylcoenzyme A / Acetyl co A
Name 3 respiratory substrates
- Glucose
- Amino acids
- Glycerol
- Fatty acids
Define Biomass
- Mass of carbon (organic compounds)
OR - Dry mass of tissue per given area
Suggest what you should do to ensure all water is removed from a tissue / sample. [2]
- Regularly weigh and re heat (less than 100 °C to prevent combustion)
- Until mass is constant
Define: Gross Primary Productivity (GPP)
- Chemical energy store in plant biomass, in a given area or volume. (Rate of photosynthesis)
Define: Net Primary Production (NPP)
- Chemical energy store in plant biomass after respiratory losses to the environment have been taken into account. NPP= GPP - R
- NPP is available for new plant growth and reproduction OR available for other trophic levels in the ecosystem, such as herbivores and saprobionts.
- kJ ha–1 year–1 OR kJ km–2 year–1 OR kJ km–3 year–1
Define: Net production of consumers
N = I – ( F + R)
where:
I represents the chemical energy store in ingested food;
F represents the chemical energy lost to the environment in faeces and urine;
R represents the respiratory losses to the
environment.
State the units for BIOMASS (in terms of productivity)
kJ ha–1 year–1
.
The percentage of the light energy trapped by the producers is very low. Give THREE reasons why.
- Reflected / absorbed by water vapour;
- Reflected from producers / wrong wavelength;
- Transmitted / passes between chloroplasts / does not strike chlorophyll / passes between plants / too few chloroplasts;
In natural ecosystems, most of the light falling on producers is not used in photosynthesis.
Suggest two reasons why.
- (Light is) reflected / Light energy is not absorbed
- (Light is) wrong wavelength / frequency.
- Accept reference to absorbing specified wavelengths/frequencies.
- (Light) misses chlorophyll / chloroplasts/ photosynthetic tissue;
- CO2 concentration or temperature is a limiting factor.
The biomass of primary consumers is less than the biomass of producers. Explain why. [4]
- Loss of energy / heat / use of energy for…. / less energy to be passed on;
- In respiration;
- In excreta / excretion / urine / carbon dioxide;
- Inedible parts / indigestible parts / egest/ egestion / to decomposers;
Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer. [5]
- Some light energy fails to strike/is reflected/not of appropriate wavelength;
- Efficiency of photosynthesis in plants is low/approximately 1-3% efficient;
- Respiratory loss / excretion / faeces / not eaten;
- Loss as heat;
- Efficiency of transfer to consumers greater than transfer to producers/approximately 10%;
- Efficiency lower in older animals/herbivores/ primary consumers/warm blooded animals;
- Carnivores consume, digest & assimilate more of their food than herbivores;
Explain how the intensive rearing of domestic livestock increases net productivity. [5]
- Slaughtered when still growing/before maturity/while young so more energy transferred to biomass/tissue/production;
- Fed on concentrate /controlled diet /controlled conditions/so higher proportion of (digested) food absorbed/lower proportion lost in faeces / valid reason for addition;
- Movement restricted** so** less respiratory loss / less energy used;
- Kept inside/heating/shelter / confined so less heat loss / no predators;
- Genetically selected for high productivity;
Describe the need for plants to both photosynthesise AND respire [5]
- In the dark no ATP production in Light dependent reactions / photosynthesis;
- Some tissues unable to photosynthesise/produce ATP;
- ATP cannot be moved from cell to cell/stored;
- Plant uses more ATP than produced in photosynthesis;
- ATP for active transport of ions / sucrose;
- ATP for synthesis (of named substance);
Explain what is meant by the term carbon sink.
Not on spec (GCSE)
- Takes up / locks up / stores carbon / carbon dioxide (for a long time) / eq ;
- Named example e.g. peat / coal / limestone / trees / fossil fuel / chalk / shells / seagrass;
Explain what is meant by the term global warming.
Not on spec (GCSE)
- Increase in {temperature of earth’s surface / mean global temperature};
- Carbon dioxide is a greenhouse gas / due to an increase in greenhouse gases
- (Which) {trap / reflect back} {heat / long wave / infra red} (in the atmosphere) ;
- Reference to an {increased / enhanced} greenhouse effect ;
- Reference to valid {effect / consequence} e.g. melting ice caps, flooding, climate change ;
Describe the role of saprobionts in the nitrogen cycle. [2]
- (secrete enzymes to) decompose proteins / DNA / RNA / urea;
- Producing / releasing ammonia / ammonium ions;
Explain how carbon-containing compounds present in the pine leaves that fall from the trees are absorbed and used for growth by saprobionts/fungi that live in the soil. [5]
- extracellular digestion;
- by secretion of hydrolystic/digestive enzymes;
- absorption of digested/soluble products;
- synthesis of structural compounds/named compound;.
- respiration provides energy for growth (of saprobiont)
What are saprobionts?
- Fungi / Bacteria that
- Secrete extracelluar enzymes to digest large insoluble organic matter
- absorb monomers for assimilation / respiration
Nitrogen compounds in the plants are made available for the main crop after ploughing in spring.
Describe the role of microorganisms in this process.
[5]
- proteins/amino acids broken down;
- deamination/ammonification/ release of ammonium compounds;
- By saprophytes/saprobionts;
- conversion to nitrates via nitrites;
- by nitrifying bacteria/named bacterium (Nitrosomonas then Nitrobacter);
- Nitrates absorbed into roots via active transport
The scientists used units of μg g−1 for the concentration of ammonia in soil.
Suggest why, in this investigation, the scientists used these units.
- (μg because) very little ammonia (in soil);
- (μg because) avoids use of (lots of) decimal places (in their results) / avoids the use of powers of 10 / avoids the use of standard form /makes numbers more manageable / Accept makes easier to plot graph
- (g-1) to allow comparisons (between samples);
Give two examples of biological molecules containing nitrogen that would be removed when a crop is harvested.
- amino acid/protein/ polypeptide/peptide;
- nucleic acid/nucleotide/base;
- DNA;
- RNA / pre-mRNA / mRNA / rRNA / tRNA
- ATP/ADP;
- NAD/NADP (reduced or not);
- Cyclic AMP/cAMP;
- Chlorophyll;
Plants absorb a number of other nutrients from the soil including phosphates.
Describe why phosphates are needed by a growing plant. [3]
- production of DNA;
- production of RNA;
- production of NADP
- production of phospholipids;
- in cell membranes;
- synthesis of ATP;
Describe how a lack of phosphates in the soil surrounding a plant can affect its growth [4]
Potential essay link
- (Required to) make ATP/glucose phosphate, so less respiration/less energy for growth;
- (Required to) make nucleotides, so less DNA/mRNA/tRNA for cell division/production of protein (for growth);
- (Required to) make RuBP/NADP, so less CO2 fixed/reduced into sugar;
- (Required to) make phospholipids for membranes;
Outline the advantages of having Mycorrhizae
growth near plants
[2]
Essay link
- Mycorrhizae help plants to defend themselves (causing an increase in crop yield);
- Mycorrhizae help plants to take up nitrates/phosphates (causing an increase in crop yield);
You are given samples of water from three different rivers.
Describe how you would obtain a quantitative measurement of their cloudiness. [3]
- Use of colorimeter;
- Measure the absorbance/transmission (of light);
- Example of how method can be standardised eg same volume of water, zeroing colorimeter, same wavelength of light/filter, shaking the sample;
Describe the process of eutrophication. [5]
- Nitrates / Phosphates / Ammonium ions flushed into waterway (leaching)
- Increased algal bloom
- Light blocked out
- Submerged aquatic plant unable to photosynthesise and die
- Increase in saprobionts so increases rate of aerobic respiration
- Saprobionts / aero.resp organismsn die as lack of oxygen (anoxic conditions)
- Increase in anaerobic microorganisms that production of toxins.
