Year 13 5.Energy transfers Flashcards
Describe the light dependent reaction (6)
- Chlorophyll absorbs light energy & 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 gradient;
- H+ ions move through ATP synthase;
- providing energy to join ADP and Pi to form ATP;
- Photolysis of water produces 2 protons, 2 electrons and ½ oxygen;
- 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;
Proton pumping to form a proton gradient is an example of active transport.
True or False (explain your answer).
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 ribulose bisphosphate/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/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)
- 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.
- 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 dependant reaction, suggest why this is not their (plants) only source of ATP.
- 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;
Describe what happens during photoionisation in the light dependent reaction.
- Chlorophyll absorbs light
OR
Light excites/moves electrons in chlorophyll; - Electron/s are lost / chlorophyll is oxidised;
OR
(Chlorophyll) becomes positively charged;
Accept electrons go to electron transport/carrier chain for ‘electrons lost’.
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.
- 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.
- Stomata allow uptake of carbon dioxide;
- Carbon dioxide used in / required for photosynthesis;
Describe the process of glycolysis. [4]
- Phosphorylation of glucose using ATP;
- Oxidation of triose phosphate to pyruvate;
- Net gain of ATP;
- NAD reduced;
Describe the link reaction [4]
- Occurs in the matix (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.
Describe how oxidation takes place in glycolysis and in the Krebs cycle. [4]
- removal of hydrogen/dehydrogenation;
- by enzymes/dehydrogenases;
- H 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;
- Protons move into intermembrane space;
- ADP/ADP + Pi;
- 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.
In many mammals, ‘uncoupling proteins’ help to maintain a constant body temperature during hibernation.
Suggest and explain how.
- Allow passage of protons/H+;
- (Energy) released as heat;
The mitochondria in muscles contain many cristae. Explain the advantage of this. [2]
- 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. [2]
- Equilibrium reached;
- Allow for expansion (gases/liquids) /pressure change in apparatus;
- Allow respiration rate of seeds to stabilise;
Explain why a log scale is used to record the number of cells/bacteria.
- 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;
Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration. [2]
- Regenerates NAD / Oxidises reduced NAD;
- (So) glycolysis continues;
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;
Define Biomass
- Mass of carbon (organic compounds)
- 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 Heat (less than 100 °C)
- Until mass is constant
What is GPP?
Gross Primary Productivity
* Chemical energy store in plant biomass, in a given area or volume. (Rate of photosynthesis)
What is NPP?
Net Primary Production
- 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.
Suggest suitable units to measure productivity (e.g. NPP)
- kJ ha–1 year–1
OR
kJ km–2 year–1
OR
kJ km–3 year–1
The percentage of the light energy trapped by the producers is very low. Give two reasons why. [2]
- Reflected / absorbed by water vapour;
- Reflected from producers / wrong wavelength;
- Transmitted / passes between chloroplasts/ between plants / too few chloroplasts;
In natural ecosystems, most of the light falling on producers is not used in photosynthesis.
Suggest two reasons why. [2]
- (Light is) reflected;
- (Light is) wrong wavelength;
- (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 / less energy to be passed on;
- In respiration;
- In excreta / excretion / urine / carbon dioxide;
- Inedible parts / indigestible parts / egesta / egestion / to decomposers;
Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer. [6]
- Some light energy fails to strike/is reflected/not of appropriate wavelength;
- Efficiency of photosynthesis in plants is low / approximately;
- 2% 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 use 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 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;
- ATP for synthesis (of named substance);
The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours. Use your knowledge of photosynthesis to describe these changes and explain why they occur. [5]
- High concentration of carbon dioxide linked with night/darkness;
- No photosynthesis in dark/night / light required for photosynthesis/light-dependent reaction;
- (In dark) plants (and other organisms) respire;
- In light net uptake of carbon dioxide by plants/plants use more carbon dioxide than they produce/ rate of photosynthesis greater than rate of respiration;
- Decrease in carbon dioxide concentration with height;
- At ground level fewer leaves/less photosynthesising tissue/more animals/less light;
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 ;
Describe the role of saprobionts in the nitrogen cycle. [2]
- (use 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 enzymes;
- absorption of digested/soluble products;
- synthesis of structural compounds/named compound;.
- respiration provide energy for growth
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/decomposers;
- conversion to nitrates via nitrites;
- by nitrifying bacteria/named bacterium;
- 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. [2]
- 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; (More on this later in the year)
- Chlorophyll;
Plants absorb a number of other nutrients from the soil including phosphates. Describe why phosphates are needed by a growing plant [4]
- production of phospholipids;
- in cell membranes;
- synthesis of ATP;
- production of DNA;
- production of RNA;
- production of NADP
Describe how a lack of phosphates in the soil surrounding a plant can affect its growth [4]
- (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]
- 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, shaking the sample;
Describe the process of eutrophication. [5]
- Nitrates / Phosphates / Ammonium ions flushed into waterway
- 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)
- *Increase in anaerobic microorganisms
- Production of toxins*
Explain why an increase in plant biomass can be taken as a measurement of net primary productivity.
- Represents dry mass / mass of carbon;
- Represents gross production minus respiratory losses;
or NPP =GPP - R
a) Nitrogen gas to Ammonium ions
b) Ammonium ions to Nitrates
c) Nitrates to Nitrogen gas
Which stage of the Nitrogen cycle involves NITRIFICATION ?
b) Ammonium ions to Nitrates
a) Nitrogen gas to Ammonium ions
b) Ammonium ions to Nitrates
c) Nitrates to Nitrogen gas
Which stage of the Nitrogen cycle involves DENITRIFICATION ?
c) Nitrates to Nitrogen gas
a) Nitrogen gas to Ammonium ions
b) Ammonium ions to Nitrates
c) Nitrates to Nitrogen gas
Which stage of the Nitrogen cycle involves Rhizobium bacteria ?
a) Nitrogen gas to Ammonium ions
Nitrogen fixation
Name the process by which some bacteria oxidise ammonia to nitrate.
Nitrification
