5. Energy transfers in and between organisms Flashcards
(137 cards)
1
Q
Where does the light-dependent reaction occur?
A
In the thylakoids of chloroplasts
2
Q
Where does the light-independent reaction occur?
A
In the stroma of chloroplasts
3
Q
Explain the role of light in photoionisation.
A
Chlorophyll molecules absorb energy from photons of light. This ‘excites’ 2 electrons, causing them to be released from the chlorophyll.
4
Q
Name the 2 main stages involved in ATP production in the light-dependent reaction.
A
Electron transfer chain
Chemiosmosis
5
Q
What happens in the electron transfer chain (ETC)?
A
Electrons released from chlorophyll move down a series of carrier proteins embedded in the thylakoid membrane and undergo a series of redox reactions, which release energy.
6
Q
How is a proton concentration gradient established during chemiosmosis?
A
Some energy released from the electron transfer chain is coupled to the active transport of H+ ions (protons) from the stroma into the thylakoid space.
7
Q
How does chemiosmosis produce ATP in the light-dependent stage?
A
H+ ions move down their concentration gradient from the thylakoid space into the stroma via the channel protein ATP synthase.
ATP synthase catalyses ADP + Pi → ATP
8
Q
Explain the role of light in photolysis.
A
Light energy splits molecule of water
2H20 → 4H+ + 4e- + O2
9
Q
What happens to the products of the photolysis of water?
A
H+ ions: move out of thylakoid space via ATP synthase and are used to reduce the coenzyme NADP.
e-: replace electrons lost from chlorophyll.
O2: used for respiration or diffuses out of leaf as waste gas.
10
Q
How and where is reduced NADP produced in the light-dependent reaction?
A
NADP + 2H+ + 2e- → reduced NADP
Catalysed by dehydrogenase enzymes.
Stroma of chloroplasts.
11
Q
Where do the H+ ions and electrons used to reduce NADP come from?
A
H+ ions: photolysis of water
Electrons: NADP acts as the final electron acceptor of the electron transfer chain.
12
Q
Name the 3 main stages in the Calvin cycle.
A
Carbon fixation
Reduction
Regeneration
13
Q
What happens during carbon fixation?
A
Reactions between CO2 and RuBP catalysed by rubisco.
Forms unstable 6C intermediate that breaks down into 2x GP.
14
Q
What happens during reduction (in the Calvin cycle)?
A
2x GP are reduced to 2x TP
Requires 2x reduced NADP and 2x ATP
Forms 2x NADP and 2x ATP
15
Q
How does the light-independent reaction result in the production of useful organic substances?
A
1C leaves the cycle (i.e. some of the TP is converted into useful organic molecules).
16
Q
What happens during regeneration (in the Calvin cycle)?
A
After 1C leaves the cycle, the 5C compound RuP forms.
RuBP is regenerated from RuP using 1x ATP.
Forms 1x ADP.
17
Q
State the roles of ATP and (reduced) NADP in the light-independent reaction.
A
ATP: reduction of GP to TP and provides phosphate group to convert RuP into RuBP.
(Reduced) NADP: coenzyme transports electrons needed for reduction of GP to TP.
18
Q
State the number of carbon atoms in RuBP, GP and TP.
A
RuBP: 5
GP: 3
TP: 3
19
Q
Describe the structure of a chloroplasts.
A
Usually disc-shaped.
Double membrane (envelope).
Thylakoids: flattened discs stack to form grana.
Intergranal lamellae: tubular extensions attach thylakoids in adjacent grana.
Stroma: fluid-filled matrix
20
Q
How does the structure of the chloroplast maximise the rate of the light-dependent reaction?
A
ATP synthase channels within granal membrane.
Large surface area of thylakoid membrane for ETC.
Photosystems position chlorophyll to enable maximum absorption of light.
21
Q
How does the structure of the chloroplast maximise the rate of the light-independent reaction?
A
Own DNA and ribosomes for synthesis of enzymes e.g. rubisco.
Concentration of enzymes and substrates in stroma is high.
22
Q
Define ‘limiting factor’.
A
Factor that determines maximum rate of a reaction, even if other factors change to become more favourable.
23
Q
Name 4 environmental factors that can limit the rate of photosynthesis.
A
Light intensity (LDR)
CO2 levels (LIR)
Temperature (enzyme-controlled steps)
Mineral/magnesium levels (maintain normal function of chlorophyll).
24
Q
Outline some common agricultural practices used to overcome the effect of limiting factors in photosynthesis.
A
Artificial light, especially at night.
Artificial heating
Addition of CO2 to greenhouse atmosphere.
25
Why do farmers try to overcome the effect of limiting factors?
To increase yield.
Additional cost must be balanced with yield to ensure maximum profit.
26
Suggest how a student could investigate the effect of a name variable on the rate of photosynthesis.
dependent variable: rate of O2 production/CO2 consumption
Use a potometer.
Place balls of calcium alginate containing green algae in hydrogencarbonate indicator (colour change orange → magenta as CO2 is consumed and pH increases).
27
State the purpose and principle of paper chromatography.
Molecules in a mixture are separated based on their relative attraction to the mobile phase (running solvent) vs the stationary phase (chromatography paper).
28
Outline a method for extracting photosynthetic pigments.
Use a pestle and mortar to grind a leaf with an extraction solvent e.g. propanone.
29
Outline how paper chromatography can be used to separate photosynthetic pigments.
Use a capillary tube to spot pigment extract onto pencil 'start line' (origin) 1cm above bottom of paper.
Place chromatography paper in solvent (origin should be above solvent line).
Allow solvent to run until it almost touches the other end of the paper. Pigments move different distances.
30
What are Rf values and how can they be calculated?
Ratios that allow comparison of how far molecules have moved in chromatograms.
Rf = distance between origin and centre of pigment spot / distance between origin and solvent front
31
Name the 4 main stages in aerobic respiration and where they occur.
Glycolysis → cytoplasm
Link reaction → mitochondrial matrix
Krebs cycle → mitochondrial matrix
Oxidative phosphorylation → via electron transfer chain → membrane of cristae
32
Outline the stages of glycolysis.
Glucose is phosphorylated to glucose phosphate by 2x ATP
Glucose phosphate splits into 2x TP
2x TP is oxidised to 2x pyruvate
Net gain of 2x reduced of NAD and 2x ATP per glucose.
33
How does pyruvate from glycolysis enter the mitochondria.
Via active transport.
34
What happens during the link reaction?
Oxidation of pyruvate to acetate.
Per pyruvate molecule: net gain of 1x CO2 (decarboxylation) and 2H atoms (used to reduce 1x NAD).
Acetate combines with coenzyme A (CoA) to form acetylcoenzyme A.
35
Give a summary equation for the link reaction.
Pyruvate + NAD + CoA → acetyl CoA + reduced NAD + CO2
36
What happens in the Krebs cycle?
Series of redox reactions produces:
ATP by substrate-level phosphorylation.
Reduced coenzymes.
CO2 from decarboxylation.
37
What is the electron transfer chain (ETC)?
Series of carrier proteins embedded in membrane of the cristae of mitochondria.
Produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration.
38
What happens in the electron transfer chain in respiration (ETC)?
Electrons released from reduced NAD and FAD undergo successive redox reactions.
The energy released is coupled to maintaining proton gradient or released as heat.
Oxygen acts as final electron acceptor.
39
How is a proton concentration gradient established during chemiosmosis in aerobic respiration?
Some energy released from the ETC is coupled to the active transport oh H+ ions from the mitochondrial matrix into the intermembrane space.
40
How does chemiosmosis produce ATP during aerobic respiration?
H+ ions move down their concentration gradient from the intermembrane space into the mitochondrial matrix via the channel protein ATP synthase.
ATP synthase catalyses ADP + Pi → ATP
41
State the role of oxygen in aerobic respiration.
Final electron acceptor in electron transfer chain.
(produces water as a byproduct).
42
What is the benefit of an electron transfer chain rather than a single reaction?
Energy is released gradually.
Less energy is released as heat.
43
Name 2 types of molecule that can be used as alternative respiratory substrates.
(amino acids from) proteins
(glycerol and fatty acids from) lipids
44
How can lipids act as an alternative respiratory substrate?
lipid → glycerol + fatty acid
Phosphorylation of glycerol → TP for glycolysis.
Fatty acid → acetate.
Acetate enters link reaction.
H atoms produced for oxidative phosphorylation.
45
How can amino acids act as an alternative respiratory substrate?
Deamination produces:
3C compounds → pyruvate for link reaction.
4C/5C compounds → intermediates in Krebs cycle.
46
Name the stages in respiration that produce ATP by substrate-level phosphorylation.
Glycolysis (anaerobic)
Krebs cycle (aerobic)
47
What happens during anaerobic respiration in animals?
Only glycolysis continues
reduced NAD + pyruvate → oxidised NAD (for further glycolysis) + lactate
48
What happens to the lactate produced in anaerobic respiration?
Transported to liver via bloodstream, where it is oxidised to pyruvate.
Can enter link reaction in liver cells or be converted to glycogen.
49
What happens during anaerobic respiration in some microorganisms?
Only glycolysis continues.
Pyruvate is decarboxylated to form ethanal.
Ethanal is reduced to ethanol using reduced NAD to produce oxidised NAD for further glycolysis.
50
What is the advantage of producing ethanol/ lactate during anaerobic respiration?
Converts reduced NAD back into NAD so glycolysis can continue.
51
What is the disadvantage of producing ethanol during anaerobic respiration?
Cells die when ethanol concentration is above 12%.
Ethanol dissolves cell membranes.
52
What is the disadvantage of producing lactate during anaerobic respiration?
Acidic, so decreases pH.
Results in muscle fatigue.
53
Similarities between aerobic and anaerobic respiration?
Both involve glycolysis.
Both require NAD.
Both produce ATP.
54
Differences between aerobic and anaerobic respiration.
Aerobic:
-produces ATP by substrate-level phosphorylation and oxidative phosphorylation
-produces much more ATP
-does not produce ethanol or lactate
Anaerobic
-substrate-level phosphorylation only
-produces fewer ATP
-produces ethanol or lactate
55
Suggest how a student could investigate the effect of a named variable on the rate of respiration of a single-celled organism.
Use a respirometer (pressure changes in boiling tube cause a drop of coloured liquid to move).
Use a dye as the terminal electron acceptor for the ETC.
56
What is the purpose of sodium hydroxide solution in a respirometer set up to measure the rate of aerobic respiration?
Absorbs CO2 so that there is a net decrease in pressure as O2 is consumed.
57
How could a student calculate the rate of respiration using a respirometer?
Volume of O2 produced or CO2 consumed/ time x mass of sample
volume = distance moved by coloured liquid x (o.5 x capillary tube diameter)2 x π
58
How do plants use the sugars from photosynthesis?
Primarily as respiratory substrates.
To synthesise other biological molecules e.g. cellulose
59
What is biomass?
Total dry mass of tissue or mass of carbon measured over a given time in a specific area.
60
Suggest the units for biomass.
When an area is being sampled: gm-2
When a volume is being sampled: gm-3
61
How can the chemical energy store in dry mass be estimated?
Using calorimetry.
Energy released = specific heat capacity of water x volume of water (cm3) x temperature increase of water.
62
Why is bomb calorimetry preferable to simple calorimetry?
Reduces heat loss to surroundings.
63
How could a student ensure that all water had been removed from a sample before weighing?
Heat the sample and reweigh it until the mass reading is constant.
64
Define gross primary production (GPP).
Total chemical energy in plant biomass within a given volume or area.
65
Define net primary productivity (NPP).
Total chemical energy available for plant growth, plant reproduction and energy transfer to other trophic levels after respiratory losses.
66
Give the mathematical relationship between GPP and NPP.
NPP = GPP - R
where R = respiratory losses
67
Why is most of the sun's energy not converted to organic matter?
Most solar energy is absorbed by atmosphere or reflected by clouds.
Photosynthetic pigments cannot absorb some wavelengths of light.
Not all light falls directly on a chlorophyll molecule.
Energy lost as heat during respiration/photosynthesis.
68
How can the net production of consumers be calculated?
NPP =I - (F + R)
I = chemical energy from ingested food
F = energy lost as faeces and urine
R = respiratory losses
69
Why does biomass decrease along a food chain?
Energy lost in nitrogenous waste (urine) and faeces.
Some of the organism is not consumed.
Energy lost to surroundings as heat.
70
Define primary and secondary productivity?
Rate of primary of secondary production.
Biomass in a specific area over a given time period e.g. kJ ha-1 year-1
71
Outline some common farming practices used to increase the efficiency of energy transfer.
Exclusion of predators: no energy lost to other organisms in food web.
Artificial heating: reduce energy lost to maintain constant body temperature.
Restriction of movement.
Feeding is controlled at the optimum.
72
Give the general equation for % efficiency.
( Energy converted to a useful form (J) / total energy supplied (J) )x 100
73
Explain why the length of food chains is limited.
Energy is lost at each trophic level.
So there is insufficient energy to support a higher trophic level.
74
What is a pyramid of biomass?
Diagram that shows the biomass at each trophic level.
75
Why is a pyramid of biomass preferable to a pyramid of numbers.
Shape of a pyramid of numbers may be skewed since a small number of producers can support many consumers.
76
Name the general stages in the phosphorus cycle.
Weathering
Runoff
Assimilation
Decomposition
Uplift
77
Why is the phosphorus cycle a slow process?
Phosphorous has no gas phase, so there is no atmospheric cycle.
Most phosphorus is stored as PO4-3 in rocks.
78
What happens during weathering and runoof?
Phosphate compounds from sedimentary rocks leach into surface water and soil.
79
Explain the significance of phosphorus to living organisms.
Plants convert inorganic phosphate into biological molecules e.g. DNA, ATP, NADP
Phosphorus is passed to consumers via feeding.
80
What happens during uplift?
Sedimentary layers from oceans (formed by the bodies of aquatic organisms) are brought up to land over many years.
81
How does mining affect the phosphorus cycle?
Speeds up uplift.
82
Name the 4 main stage of the nitrogen cycle.
Nitrogen fixation.
Ammonification.
Nitrification.
Denitrification.
83
Why can't organisms use nitrogen directly from the atmosphere?
N2 is very stable due to strong covalent triple bond.
84
What happens during atmospheric fixation of nitrogen?
High energy of lightning breaks N2 into N.
N reacts with oxygen to form NO2-.
NO2- dissolves in water to form NO3-.
85
Outline the role of bacteria in nitrogen fixation.
Mutualistic nitrogen-fixing bacteria in nodules of legumes and free-living bacteria in soil.
Use the enzyme nitrogenase to reduce gaseous nitrogen into ammonia.
86
Outline the role of bacteria in ammonification.
Saprobionts feed on and decompose organic waste containing nitrogen (e.g. urea, proteins, nucleic acids..)
NH3 released.
NH3 dissolves in water in soil to form NH4+.
87
Outline the role of bacteria in nitrification.
2-step process carried out by saprobionts in aerboic conditions:
2NH4+ + 3O2 → 2NO2- + 2H2O + 4H+
2NO2- + O2 → 2NO3-
88
Outline the role of bacteria in denitrification.
Anaerobic denitrifying bacteria convert soil nitrates back into gaseous nitrogen.
89
Explain the significance of nitrogen to living organisms.
Plant roots uptake nitrates via active transport and use them to make biological compounds e.g.:
amino acids
NAD/NADP
nucleic acids
90
Outline the role of mycorrhizae.
Mutualistic relationship between plant and fungus increases surface area of root system = increases uptake of water and mineral ions.
91
Give 3 benefits of planting a different crop on the same field each year.
Nitrogen-fixing crops e.g. legumes make soil more fertile by increasing soil nitrate content.
Different crops have different pathogens.
Different crops use different proportions of certain ions.
92
Name the 2 categories of fertiliser and state the purpose of using fertiliser.
Organic: decaying organic matter and animal waste.
Inorganic: minerals from rocks, usually containing nitrogen, phosphorus, potassium.
To increase gross productivity for higher yield.
93
At a certain point, using more fertiliser no longer increases crop yield. Why?
A factor unrelated to the concentration of mineral ions limits the rate of photosynthesis, so rate of growth cannot increase any further.
94
Outline 2 main environmental issues caused by the use of fertilisers.
Leaching: nitrates dissolve in rainwater and 'runoff' into water sources.
Eutrophication: water source becomes putrid as a result of algal bloom.
95
What happens during eutrophication?
Aquatic plants grow exponentially since nitrate level is no longer a limiting factor.
Algal bloom on water surface prevents light from reaching the bottom and plants die.
Oxygen levels decrease as population of aerobic saprobionts increases to decay dead matter, so fish die.
Anaerobic organisms reproduce exponentially and produce toxic waste which makes water putrid.
96
How can the risk of eutrophication be reduced?
Sewage treatment marshes on farms.
Pumping nutrient-enriched sediment out of water.
Using phosphate-free detergent.
97
What is photosynthesis
Occurs ONLY in plants. The plant makes glucose from light, carbon dioxide and water
98
Limiting factors of photosynthesis
Sunlight intensity, carbon dioxide concentration and temperature
99
Carbon fixation
The first stage of the Calvin cycle. Carbon dioxide enters the leaf and diffuses into the stroma of the chloroplast. Here it is combined with ribulose biphosphate (RuBP) a 5-carbon compound. This reaction is catalysed by the enzyme rubisco. This gives an unstable 6-carbon compound, which quickly breaks down into two molecules of 3-carbon compound called glycerate-3-phosphate (GP)
100
Reduction and carbohydrate formation
ATP from the light dependent reaction is used to turn the 2 3-carbon compound into another 3-carbon compound called triose phosphate (TP). This reaction also requires hydrogen ions which come from reduced NADP. Reduced NADP is recycled into NADP. Some triose phosphate is converted into a useful organic compounds such as glucose and some continues to regenerate RuBP.
101
Regeneration phase
The last phase in the Calvin cycle. Five out of every six molecules of TP produced in the cycle are used to regenerate RuBP uses the rest of the ATP produced by the light-dependent reaction. This means that to produce the two molecules of TP needed to make one hexose sugar the Calvin cycle needs to turn 6 times and 18 ATP and 12 reduced NADP are needed from the light dependent reaction.
102
Photoautotrophs
An organism that uses energy from sunlight to convert carbon dioxide and water to carbon compounds
103
ATP and reduced NADP
The products of the light dependent reaction
104
Glucose
The product of the light independent reaction
105
The equation for photosynthesis
6CO2 + 6H2O --> C6H12O6 + 6O2
106
What is the chemical equation for photolysis?
2H2) --> 4H+ + 4e- + 02
107
Why is photolysis important?
The loss of two electrons from the electron transport chain in a molecule of chlorophyll during the light dependent reaction means that the process will stop. In order to continue absorbing and transforming light energy, the chlorophyll must replace the electrons. It does this by splitting water molecules into hydrogen ions, electrons and oxygen molecules.
108
How are leaves adapted for photosynthesis?
-Large surface area
- They are thin
- Mesophyll cells are filled with chloroplasts
- Lots of air gaps increases surface area inside leaf for gas exchange
- Constant source of water from the xylem vessels
109
Photoionisation
Process by which a chlorophyll molecule becomes ionised. Caused by the chlorophyll molecule absorbing light energy and boosting the energy of a pair of electrons without a chlorophyll molecules, raising them to a higher energy level and they become so energetic they leave the chlorophyll molecule altogether and are taken up by an electron carrier
110
Light dependent reaction
Light is absorbed by chlorophyll which excites 2 electrons. These electrons are passed down the electron transport chain each time the electrons move from one carrier to the other the carrier they leave is oxidised and the one they join is reduced. The electrons lose a small amount of energy each time they move down a carrier molecule, this energy is used to pump hydrogen ions into the thylakoids lumen. The electrons leave the chain and are eventually given to NADP which reduces it. Hydrogen ions diffuse out of the lumen through the ATPase enzyme, this is called chemiosmosis. The movement of the hydrogen ions leaving the chlorophyll is used to turn ADP and Pi into ATP. Photolysis occurs, water is split into electrons, hydrogen ions and oxygen, to provide more electrons to continue the process
111
Light independent reaction (the Calvin cycle)
This reaction does not require direct sunlight, however it does require products made by sunlight so will not continue for long in the absence of light
112
How is energy stored in plants?
In the glucose until plants release it by respiration
113
Light
In the absence of this limiting factor of photosynthesis, photosynthesis stops. If the intensity increases so does the rate of photosynthesis until other limiting factors come into play
114
Carbon dioxide
This limiting factor of photosynthesis affects the efficiency of enzyme activity, particularly rubisco. At a certain level the plant is saturated and the reactions involved in photosynthesis are limited by other factors
115
Temperature
This limiting factor is directly proportional to the rate of photosynthesis up to a point. The rate of photosynthesis approximately doubles for every 10 increase until it reaches 25. This is where photosynthesis levels off and starts to decline. This decline is due to the affinity rubisco has for carbon dioxide. Above 25 rubisco carboxylase function switches to oxygenase. The graph for the limiting factor is different because of this phenomenon
116
Carboxylase
Rubisco fixes carbon dioxide onto RuBP
117
Oxygenase
Rubisco fixes oxygen onto RuBP
118
How can farmers increase the yield of their crops knowing that CO2 concentration is a limiting factor for plant growth in their greenhouses?
Add CO2 to the air
119
How can farmers increase the yield of their crops knowing that light intensity is a limiting factor for plant growth in their greenhouses?
Add lamps for light at night
120
How can farmers increase the yield of their crops knowing that temperature is a limiting factor for plant growth in their greenhouses?
Add a heating and cooling system
121
Photophosphorylation
The process of generating ATP from ADP and phosphate by means of a proton-motive force generated by the thylakoid membrane of the chloroplast during the light reactions of photosynthesis
122
Aerobic respiration
Respiration with oxygen
123
Anaerobic respiration
Respiration without oxygen
124
Respiration
The release of energy from glucose
125
Glycolysis
This is the first process in aerobic and anaerobic respiration. A molecule of glucose is converted into glucose phosphate, this is done by the hydrolysis of two ATP molecules into ADP and Pi this is called phosphorylation. The glucose phosphate molecule is then oxidised into two molecules of triose phosphate. Each molecule is then converted into pyruvate. This reaction produces ATP. A total of 4 ATP molecules are produced, two for each triose phosphate. There is a net gain of 2 ATP molecules. The conversion of triose phosphate is an oxidation reaction and involves the removal of hydrogen to reduce a co-enzyme called NAD. NAD is converted to reduced NAD as a result.
126
Which two reactions take place in the matrix of the mitochondria?
The link reaction and the Krebs cycle
127
The link reaction
Pyruvate is oxidised in a reaction with NAD creating reduced NAD, CO2 and a 2-carbon molecule called an acetyl group. This reacts with co-enzyme A to produce acetylcoenzyme A. The products of this reaction are 2 reduced NAD, 2 CO2 and 2 acetylcoenzyme A molecules
128
The Krebs cycle
The third stage in cellular respiration. Acetylcoenzyme A joins the cycle by reacting with a 4-carbon compound to form a 6-carbon compound. This molecule undergoes a series of redox reactions involving NAD, ADP and FAD. These reaction result in the 6-carbon molecule being turned back into the 4-carbon molecule. Other products of the Krebs cycle are 2 |CO2, 3 reduced NAD, 1 FADH2 and one ATP for each molecule of the 4-carbon compound. The reduced NAD and FADH2 go on to donate electrons in the next stage
129
The electron transport chain
The last step in aerobic respiration. The cristae of the mitochondria are studded with proteins and enzymes used in this stage. The reduced NAD and FAD from the Krebs cycle and glycolysis are used here. They donate electrons from the hydrogen atoms they are carrying to the first molecule in the chain, and the hydrogen ions that are left are actively transported across the inner membrane of the mitochondria. The electrons are passed along the chain in a series of oxidation and reduction reactions. As the electrons are transferred, the electrons lose energy and the cell is able to use this to power reaction between ADP and Pi to create ATP this is called an oxidative phosphorylation reaction.
130
The chemical equation for aerobic respiration
C6H12 + 6O2 --> 6H2O + energy
131
The equation for anerobic respiration in animals
Pyruvate + 2NADH --> lactate + 2NAD
CH3COCOOH + 2NADH --> C3H6)3 + 2NAD
132
The equation for anaerobic respiration in plants and yeast
Pyruvate + 2NADH --> ethanol + CO2 + 2NAD
CH3COCOOH + 2NADH --> C2H5OH + CO2 + 2NAD
133
Anaerobic respiration
A glucose molecule is broken down into 2 pyruvate molecules this releases electrons in the process and generates 2 molecules of ATP. Pyruvate is converted through a fermentation process into lactate or ethanol and CO2 is released. So only 2 ATP are created as a result of this type of respiration
134
Lactate
A compound produced during the breakdown of glucose in anaerobic respiration in animals
135
Fermentation
A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as alcohol or lactic acid
135
Ethanol and CO2
The compounds produced during the breakdown of glucose in anaerobic respiration in plants and yeast
136
