Section 5: Energy transfers in and between organisms Flashcards
(121 cards)
1
Q
Which wavelengths of light are best absorbed by chlorophyll
A
Orange and blue
2
Q
How does the structure of the chloroplast enable effieciently photosynthesis.
A
The structure of the chloroplast enables efficient photosynthesis by:
1. Thylakoid membranes: Provide a large surface area for the attachment of chlorophyll, enzymes, and electron carriers involved in the light-dependent reactions.
2. Stroma: Contains enzymes for the light-independent reactions (Calvin cycle) and surrounds the thylakoids to allow easy diffusion of products from the light-dependent reactions.
3
Q
What stage of photosynthesis occurs in the grana
A
Light dependent reaction
4
Q
Name 2 products of the LDR that are needed in the LIR and what is the other waste product
A
ATP and NADPH used
O2 waste ish
5
Q
What happens when chlorophyll pigments absorb light and what is this process called
A
Excited electrons and they move out of PS2 along electron transfer chain called photoionisation
6
Q
How does light effect water in the LDR
A
Photolysis energy used to split water into protons oxygen and electrons. electrons goes to PS2
7
Q
Where do the sub products of photolysis go and what stage of photosynthesis is it
A
Light dependent reaction
Proton/hydrogen is picked up by NADP to from NADPH used in the LIR
The electron goes to PS2 and is passed along electron transfer chain
The oxygen either used for respiration or diffuses out of the leaf through stomata
8
Q
What happens to NADP in the LDR
A
Reduced
attaches to H to from NADPH
9
Q
What is the process that involves the movement of hydrogen ions across a membrane to generate ATP and what stage of photosynthesis is it
A
Light dependent reaction
Chemiosmosis
10
Q
Describe chemiosmosis
A
Chemiosmosis during the light-dependent reaction (AQA A-Level, 4 marks):
1. Energy from excited electrons, transferred along the electron transport chain in the thylakoid membrane, is used to pump protons (H⁺) into the thylakoid space from the stroma.
2. This creates a high concentration of protons in the thylakoid space, establishing a proton gradient across the thylakoid membrane.
3. ATP synthase: Protons diffuse back into the stroma (as-well as protons from photolysis) through ATP synthase, down the concentration gradient.
4. ATP formation: The movement of protons through ATP synthase provides energy for the synthesis of ATP from ADP and inorganic phosphate (Pi).
11
Q
Who discovered the reactions of the light-independent reaction stage
A
Melvin Calvin
12
Q
What is the role of ribulose bisphosphate?
A
Carbon fixation: combines to CO2 catalysed by enzyme rubisco to eventually release organic molecules
13
Q
Give three reasons why ATP is required in the light-independent reactions
A
ATP is required in the light-independent reactions for:
1. Reduction of GP: Provides energy to reduce glycerate-3-phosphate (GP) into triose phosphate (TP).
2. Regeneration of RuBP: Supplies energy for the regeneration of ribulose bisphosphate (RuBP) from TP.
3. Synthesis of organic molecules: Provides energy for the formation of glucose and other carbohydrates.
14
Q
What is the role of NADPH in the light independent reactions
A
- Reduction of GP: NADPH reduces GP into TP
- Provides hydrogen: Supplies the hydrogen needed for the reduction process.
15
Q
What would happen to the level of GP if the lights were turned off?
A
- GP levels would increase: As RuBP continues to combine with CO₂, forming more GP.
- No reduction of GP: Without light, no NADPH or ATP is produced in the light-dependent reactions, so GP cannot be reduced to TP.
16
Q
Name three possible products that might be synthesised as a result of the light-independent reactions?
A
- Glucose (or other carbohydrates).
- Amino acids.
- Lipids.
17
Q
Explain why the rate of photosynthesis will not increase indefinitely if the light intensity continues to be increased
A
- Limiting factors: Other factors, such as CO₂ concentration or temperature, become limiting.
- Saturation point: Light-dependent reactions reach a maximum rate as all photosystems are saturated.
18
Q
How many carbon molecules does these molecules have:
RuBP
GP
TP
CO2
A
RuBP = 5C
GP = 3C
TP = 3C
CO2 = 1C
19
Q
Describe how NADP os reduced in the light-dependent reaction
A
- Electrons: NADP is reduced by electrons from the electron transport chain.
- Protons: NADP also combines with protons (H⁺) from the photolysis of water (after it has gone through ATP synthase) to form reduced NADP (NADPH).
20
Q
Describe the part played by reduced NADP in the light-independent reaction
A
- Reduction of GP: Reduced NADP (NADPH) donates electrons and hydrogen ions to reduce GP to TP
- provides energy from hydrolysis reaction of NADPH splitting
21
Q
Describe 2 features of an ATP molecule which make it a useful source of energy
A
- Small and soluble: ATP is small and soluble, so it can easily move within cells to where energy is needed.
- Instant release of energy: ATP releases energy quickly when one phosphate group is removed, making it efficient for cellular processes.
- Quickly regenerated: ATP can be easily converted back from ADP and Pi, providing a constant supply of energy.
22
Q
Write a simple equation summarising reaction involving CO2 GP and RuBP
A
RuBP + CO2 ——-> 2 GP
Catalysed by Rubisco enzyme
23
Q
What are the three stages in the light dependent reaction?
A
Photoionisation: light energy excited electrons they move out of chlorophyll. Chlorophyll has been ionised by light
Photolysis: Light energy absorbed in photo system 2 splits water into protons hydrogen and electron
Chemiosmosis: Electron transfer chain provide energy for Protons to move into thylakoid space which are then pumped back into stroma along with protons from photolysis through ATP synthase release ATP and reduce NADP
24
Q
Where in a cell is the enzyme rubisco found
A
Stroma of a chloroplasts
25
What substance combines with CO2 in a chloroplast
RuBP
26
Name the four stages of Aerobic respiration
1. Glycolysis
2. Link reaction
3. Krebs cycle
4. Oxidative phosphorylation
27
What is glycolysis?
Glucose (6C) phosphorylated to hexose bisphophate
hexose bisphosphate split into 2TP
Oxidation of TP to produce 2 pyruvates
the production of ATP
28
What is the link reaction summarised equation
pyruvate + NAD +coA ——> acetyl CoA + reduced NAD + CO2
29
What is the overall yeild from glycolysis
2 ATP
2 reduced NADP
2 molecules of pyruvate
30
Describe the Krebs cycle
1. Acetyl-CoA combines with 4 carbon molecule to form a 6 carbon molecule
2. Series of decarboxylation and dehydrogenation reactions occur.
3. CO₂ is released (two molecules per cycle).
4. Reduced NAD (three molecules) and reduced FAD (one molecule) are produced.
5. ATP is produced via substrate-level phosphorylation.
6. 4 carbon molecule is regenerated.
31
Explain the significance of the Krebs cycle in respiration (6 marks)
1. Makes reduced NAD and FAD, which carry electrons to make energy.
2. These are used in the electron transport chain to produce ATP.
3. Produces a small amount of ATP directly.
4. Releases carbon dioxide as a waste product.
5. Restarts the cycle by regenerating oxaloacetate.
6. Provides molecules needed for making other substances like amino acids.
32
State an equation for anaerobic respiration in plants after glycolysis
pyruvate + NADH —> ethanol + carbon dioxide + NAD
33
What is the product of glycolysis
2 Pyruvate
2 NADH
2 ATP
34
Describe the equation for anaerobic respiration in animal cells following glycolysis
2 pyruvate + 2NADH —-> 2 Lactate + 2 NAD
35
Where does anaerobic respiration take place
Cytoplasm
36
Describe a light-dependent reaction
1 - Chlorophyll absorbs light energy
2 - Excites electrons
3 - Electron transport chain releases energy
4 - Energy used to join ADP + Pi —> ATP
5 - Photolysis of water produces protons, oxygen and electrons
6 - H+ ions pumped/ actively transported out and back in (ATP Synthase)
7 - NADPH hydrogen carrier reduced
37
What is an accessory pigments
absorb wavelengths of light that are not easily absorbed by chlorophyll
38
What is a producer
photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide, and mineral ions.
39
What is a consumer
Consumers are organisms that obtain their energy by feeding on other organisms rather than using energy of sunlight directly.
40
What is a primary consumer
Organisms that directly eat producers (green plants)
41
What is a saprobionts
a group of organisms that break down the complex materials materials in dead organisms into simple ones
42
Define a food chain
a feeding relationship in which the produces are eaten by primary consumers then secondary consumers and so fourth… referring
43
Describe a food web
different food chains within a habitat interact with each other gm-2
44
What is bio mass
Total mass of living material in a given time in a specific area
45
What do food webs show
The relationship between organisms and energy transfers
Multiple food chains
46
How can the chemical energy store in an organism be estimated
calorimetry
47
Name three reasons why not all light energy. reaching a leaf is converted to biomass
Misses chlorophyll
Wrong wavelength
Respiration
48
What is GPP?
gross primary production
total quantity of the chemical energy store in plant biomass in a given area or volume in a given time
49
What is NPP
net primary production
NPP = GPP - respiration
50
What is a stage in a food chain called
tropic levels
51
What is the main source of energy for all ecosystems
The Sun
52
How does factory farming increase productivity
Movement restricted so less energy used in muscle contraction kept warm to reduce heat loss
feeding controlled
protects them from predators
53
Describe the nutrient cycle
1. nutrient is taken up by producers as simple inorganic molecules
2. the producer incorporates the nutrient into complex organic molecules
3. when the producer is eaten, the nutrient passes into consumers
4. It then passes along the food chain when these animals are eaten by other consumers
5. when the producers and consumers die their complex molecules are broke down by saprobiontic microorganisms that release the nutrient in its original simple form
54
Describe the nitrogen cycle
1. Nitrogen Fixation: Nitrogen-fixing bacteria, such as Rhizobium in root nodules of legumes, convert atmospheric nitrogen (N₂) into ammonia (NH₃), which then forms ammonium ions (NH₄⁺).
2. Ammonification: Decomposers, including saprobionts, break down organic nitrogen compounds from dead organisms and waste products into ammonia, which is subsequently converted into ammonium ions.
3. Nitrification: Nitrifying bacteria in the soil convert ammonium ions into nitrite ions (NO₂⁻) and then into nitrate ions (NO₃⁻), which plants can absorb and utilize.
4. Denitrification: In anaerobic conditions, denitrifying bacteria convert nitrate ions back into nitrogen gas (N₂), releasing it into the atmosphere and completing the cycle.
55
What happens during denitrification
converts nitrates to nitrogen in absence of oxygen
56
What is nitrification
Ammonia —-> nitrite ——> nitrate
57
Where does the ammonia come from in nitrification
Nitrogen fixation
Ammonification
58
What stage of the nitrogen cycle converts nitrogen to ammonia
Nitrogen fixation
59
What are the 2 stages of ammonification
1. Proteins to amino acid using extracellular protease enzyme
2. Removal of the amino group from the aqa using delaminate enzyme (deamination)
60
What are phosphorus used in
ATP: for respiration, active transport, energy release, growth
DNA: nucleotides, backbone, cell division, growth, proteins
Phospholipid bilayer: cell membrane
61
Describe the phosphorus cycle
1. Weathering of Rocks: Phosphate ions are released from sedimentary rocks through weathering and erosion, entering soils, lakes, rivers, and oceans.
2. Absorption by Plants: Plants absorb these phosphate ions from the soil through their roots, often with the assistance of mycorrhizal fungi, which enhance phosphate uptake.
3. Consumption by Animals: Herbivores obtain phosphorus by eating plants, and carnivores obtain it by eating herbivores. Phosphorus is essential for forming biological molecules like DNA, RNA, and ATP.
4. Return to the Environment: When plants and animals die, decomposers like bacteria and fungi break down their organic matter, releasing phosphate ions back into the soil or water, making them available for reuse by plants.
62
What is the role of mycorrhizae in nitrogen cycle
The fungi acts like extensions of the plants root system and vastly increases the total surface area for the absorption of water and minerals. Enables them to better resist drought and take up inorganic ions more readily
mutualistic
63
How does the phosphorus cycle work
Phosphorus uptake by plants: Phosphorus is taken up by plants through their roots and used to build molecules such as DNA, RNA, and ATP.
Decomposition of dead plants and animals: When plants and animals die, their remains are decomposed by decomposers such as bacteria and fungi, releasing phosphorus back into the soil.
Soil phosphorus: Some of the phosphorus released during decomposition is taken up by plants and reused, while some of it is lost from the soil through runoff and leaching.
Phosphorus in water: Phosphorus in water can be taken up by aquatic plants and animals, or it can be lost from the water through runoff, leaching, and precipitation.
Phosphorus in the atmosphere: Phosphorus in the atmosphere is primarily in the form of phosphates in aerosols, which can be transported long distances before being deposited on land or in water.
64
What is eutrophication and why is it important to understand in relation to the phosphorus cycle?
Eutrophication is the process by which a body of water becomes enriched with nutrients, leading to excessive growth of algae and other aquatic plants. This can have negative impacts on aquatic ecosystems, including reduced oxygen levels, changes in species composition, and increased disease outbreaks. Understanding eutrophication is important in relation to the phosphorus cycle because it highlights the impacts of human activity on the availability of phosphorus in the environment and the need to manage this resource sustainably.
65
How does human activity impact the phosphorus cycle?
Fertilizer use: The use of fertilizers can increase the amount of phosphorus in the soil, leading to over-fertilization and runoff into water bodies.
Land use changes: Changes in land use, such as deforestation and urbanization, can reduce the amount of phosphorus in the soil and increase the amount of phosphorus in runoff and leaching.
Sewage discharge: Sewage discharge can increase the amount of phosphorus in water bodies, leading to eutrophication and changes in aquatic ecosystems.
66
Why is the phosphorus cycle important
The phosphorus cycle is important because it helps to regulate the availability of phosphorus in the environment. This is important because phosphorus is an essential nutrient for all living organisms, and without an adequate supply of phosphorus, growth and reproduction would be limited.
67
What is leaching
Leaching is where fertilisers are washed into rivers and lakes. This occurs when too much fertiliser is applied, or during heavy rainfall, removing the water soluble compounds from the soil.
68
What are the concequences of fertiliser use
reduced biodiversity
leaching
eutrophication
69
Describe eutrophication
step 1 - mineral ions leached into rivers from fertilised fields stimulates the rapid growth of algae
step 2 - large amounts of algae blocks sunlight reaching the plants at the bottom of the water
step 3 - the plant at the bottom die
step 4 - Bacteria feed on the dead plant matter, reducing the oxygen concentration (aerobic respiration)
step 5 - Fish and other aquatic organisms die because there isnt enough oxygen
70
What are factors effecting eutrophication
temperature
still water
71
What is B.O.D
mass of oxygen consumed by microbial respiration
72
How does temperature affect eutrophication
Higher rate of respiration and metabolic processes are sped up due to inc enzyme activity. Mineral concentration increases as water evaporates
73
How does still water affect eutrophication
algae bloom stays stagnant and wont be disturbed in moving water water is constantly re-oxygenated
74
Give an example of natural fertilisers and an example of artificial fertilisers
natural - dead and decaying plants or animal waste
artificial - NPK ( nitrogen, phosphorus, potassium)
75
How do fertilisers increase productivity?
The application of either type of fertiliser can provide plants with the essential minerals they need for growth. For example, nitrogen in fertilisers is an essential component of amino acids and nucleotides in DNA, increases the rates of photosynthesis and growth, and improves crop productivity.
76
Name three environmental factors that should be controlled when measuring the rate of photosynthesis
Temperature
Humidity
Wind
Carbon dioxide availability
77
Describe how the products of the light-dependent reaction are used in the light independent reaction to produce triose phosphate
reduced NADP and AATP
ATP provides energy
GP reduced to TP
78
Suggest and explain the advantage to plants transmitting signal proteins through mycorrhizal networks, rather than releasing them in the air. 2 marks
Direct transmission plant-to-plant
Localised/faster response
79
Suggest how defensive enzymes produced by plants destroy bacteria
Enzymes hydrolyse bacteria cell wall made up of muiren
80
The processes that occur in the electron transfer chain are also known as oxidative phosphorylation. Suggest why this term is used.
The movement of electrons along the chain is due to oxidation. the energy from the electrons combines inorganic phosphate and ADP to from ATP = phosphorylation
81
The surface of the inner mitochondrial membrane is highly folded to form cristae. State one advantage of this arrangement to the electron transfer chain.
It provides a large surface area of membrane incorporating the co enzymes (NAD/FAD) and electron carriers that transfer the electrons along the chain
82
The oxygen taken up by organisms has an important role in aerobic respiration. Explain this role.
Oxygen is the final acceptor of the electrons and hydrogen ions (protons) in the electron transfer chain. Without it the electrons would accumulate along the chain and respiration would cease
83
as part of which molecule does the oxygen taken into an organism leave after being respired?
Water molecule
84
What are the 4 key stages of aerobic respiration and where does each one occur?
1. Glycolysis (cytoplasm)
2. Link reaction (mitochondrial matrix)
3. Krebs cycle (mitochondrial matrix)
4. Oxidative phosphorylation (mitochondrial inner membrane-cristae)
85
Describe glycolysis in three steps.
1. Phosphorylation glucose to glucose phosphate, using ATP
2. The production of Triose Phosphate
3. Oxidation of Triose Phosphate produce pyruvate with a net gain of ATP and reduced NAD
86
Describe the link reaction.
Pyruvate (3C) made in glycolysis is oxidised to acetate.
NAD picks up the hydrogen and becomes reduced NAD
Acetate then combines with coenzyme A in to produce acetylcoenzyme A
The link reaction occurs twice for every glucose molecule
So: 2x Acetyl CoA , 2 x CO2 released , 2 reduced NAD
87
What are the products of the krebs cycle for every glucose?
6 x reduced NAD
2 x reduced FAD
2 x ATP
4 x CO2
half this to get the products per cycle
88
Describe oxidative phosphorylation stage of aerobic respiration.
In the mitochondrial matrix the electrons are carried along the electron transfer chain
that releases energy
this energy is used to actively transport the protons from the mitochondrial matrix into the inter membrane space
that creates an concentration gradient for proton to facilitated diffuse through ATP synthase
ATP synthase phosphorylates ADP to produce ATP
Oxygen forms water when picks up protons
89
What is the overall yield from one glucose molecule undergoing glycolysis?
2 x ATP
2 x reduced NAD
2 x pyruvate
90
In glycolysis describe how Triose phosphate becomes pyruvate.
2 Hydrogen is removed and transferred to a hydrogen-carrier molecule known as NAD to form reduced NAD
2 molecules of ATP are regenerated from ADP
91
What is the net yield of glucose molecules in glycolysis?
2
92
What is the net yield of glucose molecules in the kreb cycle?
2
93
In oxidative phosphorylation, where does the electron come from for the electron transport chain?
reduced NAD transfers its 2 high energy electrons to become NAD
94
How do protons move from the intermembrane space back into the matrix during oxidative phosphorylation.
Higher concentration in the intermembrane space than the matrix, protons diffuse down the concentration gradient through ATP synthase into the matrix, this generates ATP and is called chemiosmosis
95
What is a primary consumer?
directly eat producers (green plants) while a secondary consumer would eat them (primary consumer)
96
Define biomass.
The total mass of living material in a specific area at a given time
97
How can the chemical energy store in dry mass be estimated?
Using calorimetry
98
How do you calculate NPP
NPP = GPP - R (respiratory losses)
99
Describe why there may be a low % of energy transferred between trophic levels.
1. Some of the organism is not consumed
2. Some parts are consumed but cannot be digested and are therefore lost in faeces
3. Some of the energy is lost in excretory materials, such as urine
4. Energy loss via heat from respiration
100
Define GPP and NPP
Gross primary production is the total quantity of chemical energy stored in plant biomass, in a given area or volume
Net primary production is the chemical energy stored in which is left hewn these losses to respiration have been taken out
101
What are the four stages in the nitrogen cycle?
Nitrogen fixing
Ammonification
Nitrification
Denitrification
102
Why is the nitrogen cycle so important?
Animal and plants cannot obtain nitrogen through gas exchange, so microorganisms are needed to break nitrogen’s triple bond and convert nitrgoen gas into nitrgoen containing substance that plants and animals can absorb.
103
Which biological molecules contain nitrogen?
Proteins, ATP and nucleic acids
104
Describe the nitrogen cycle
Atmospheric nitrogen
Either nitrogen fixation (bacteria living in legume root nodules convert it) or ammonification (nitrogen fixing bacteria naturally occurring convert nitrogen to ammonium)
Nitrifying bacteria converts ammonium to Nitrites to Nitrates
Nitrates are absorbed by plants (assimilation) and eaten by animals
Decomposes will convert dead plant and animal matter to ammonia (ammonification again)
Denitrifying bacteria converts nitrates back into nitrogen gas in the atmosphere
105
Describe nitrification
Ammonium converted to nitrites then to nitrates by nitrifying bacteria
106
Why do farmers plough the soils?
To aerate the soil to make sure there is oxygen in the soil
Denitrifying bacteria is anaerobic so will only happen when there is not any oxygen
Do not want nitrates converted to atmospheric nitrogen because then that is less for the plants to absorb
107
Is nitrification oxidation or reduction?
Oxidation
The nitrifying bacteria is aerobic bacteria
108
What is the nitrogen containing matter that decomposers break down into ammonia?
Protien in dead plant matter or urea in the urine
in an exam you must name what the nitrogen containing matter is
109
The relationship between mycorrhizal fungi and plants is…
mutualistic
110
Explain why fertilisers are needed in an agricultural ecosystem.
111
Contrast artificial and natural fertilisers.
Natural fertilisers are cheaper, and often free if the farmer owns animals. However, the exact minerals and proportions cannot be controlled.
Artificial fertilisers are chemicals created to contain exact proportions of minerals. Inorganic substances are more water soluble, and therefore more of these ions dissolve in the water surrounding the soil. Whilst this is an advantage tot eh plant for absorbing the nitrates and phosphates, the downside is that their high solubility means that larger quantities are washed away with rainfall and therefore have a greater impact on the environment.
112
What is leaching?
leaching is when water-soluble compounds are washed away, often into rivers or ponds.
If nitrogen fertilisers leach into waterways is causes eutrophication
113
List some negative effects the use of nitrogen-containing fertilisers have on the environment.
1. Reduced species diversity (nitrogen-rich soils favour growth of rapidly growing species like grass which outcompete other species)
2. Leaching (pollution of water courses )
3. Eutrophication
114
How does the use of nitrogen-containing fertilisers reduce species diversity?
Because nitrogen-containing soils favour the growth of rapidly growing species like grasses and nettles. These out-compete many other species. Species-rich meadows only survive with low nitrogen containing soil because it allows for other species to compete with the grasses
115
Describe eutrophication (6marks)
1) Algae bloom blocks light
2) No photosynthesis, so plants die
3) Saprobiotic decomposition occurs
4) Microorganisms respire aerobically (use up oxygen)
5) Less oxygen for fish to respire, therefore they die
6) increase in anaerobic microorganisms; release hydrogen sulphide/nitrates/toxic waste
7) water becomes putrid
116
Explain what is meant by eutrophication
Eutrophication is the processs by which by which salts build up in bodies of water
117
Explain how the increase of algal growth on the surface can lead to the death of plants growing beneath them.
The concentration of algae near the surface becomes so dense that no light penetrates to deeper levels. No light means no photosynthesis and hence no carbohydrate for respiration and so plants at lower levels die
118
Explain how the death of plants on the sea bed (in eutrophication) can result in the death of animals such as fish
Dead plants are used as food saprobionts. With an increased supply of this food, the population of saprobionts increases exponentially. Being aerobic they used up oxygen in the water leading to the death of fish, which cannot respire without it.
119
What is phosphorus used for in organisms?
DNA/RNA
ATP
Phospholipid bilayer
120
Why are mycorrhizae beneficial for plant growth?
1. The fungi increase the surface area for water and mineral absorption
2. The mycorrhizae acts like a sponge so holds water and minerals around the roots
3. This makes plants more drought resistant and able to take up more inorganic ions
121
Describe the phosphorus cycle (6marks)
Phosphate ions are released from rocks by weathering and enter soils and water.
Plants absorb phosphate ions through their roots.
Animals eat plants and obtain phosphorus.
When plants and animals die, decomposers break them down, returning phosphate to the soil.
Phosphate is also returned via animal waste.
Some phosphate is washed into rivers and oceans, where it forms sedimentary rocks, restarting the cycle.
