3.5 Energy transfers in and between organisms (A-level only) Flashcards
(94 cards)
1
Q
Location of light dependent reaction
A
- Thylakoid membranes of chloroplast
2
Q
Location of light independent reaction
A
- Stroma of chloroplast
3
Q
Chloroplast structure
A
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4
Q
Thylakoid membranes
A
- Folded membranes containing photosynthetic proteins (chlorophyll)
- embedded with transmembrane electron carrier proteins
- involved in the LDRs
5
Q
Chlorophyll
A
- Located in proteins on thylakoid membranes
- mix of coloured proteins that absorb light
- different proportions of each pigment lead to different colours on leaves
6
Q
Advantage of many pigments
A
- Each pigment absorbs a different wavelength of visible light
- many pigments maximises spectrum of visible light absorbed
- maximum light energy taken in so more photoionisation and higher rate of photosynthesis
7
Q
Light-dependent reaction (LDR)
A
- First stage of photosynthesis
- occurs in thylakoid membranes
- uses light energy and water to create ATP and reduced NADP for LIR
- involves photoionisation of chlorophyll, photolysis and chemiosmosis
8
Q
Photolysis
A
- Light energy absorbed by chlorophyll splits water into oxygen, H+ and e-
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9
Q
Products of photolysis
A
- H+
◦ Picked up by NADP to form reduced NADP for LIR - e-
◦ passed along chain of
electron carrier proteins - oxygen
◦ used in respiration or diffuses out leaf via stomata
10
Q
Photoionisation of chlorophyll
A
- Light energy absorbed by chlorophyll excites electrons so they move to a higher energy level and leave chlorophyll
- some of the energy released is used to make ATP and reduced NADP
11
Q
Chemiosmosis
A
- Electrons that gained energy move along a series of electron carriers in thylakoid membrane
- release energy as they go along which pumps protons across thylakoid membrane
- electrochemical gradient made
- protons pass back across via ATP synthase enzyme producing ATP down their conc. gradient
12
Q
What happens to protons after chemiosmosis?
A
- Combine with co-enzyme NADP to become reduced NADP
- reduced NADP used in LIR
13
Q
Products of LDR
A
- ATP (used in LIR)
- reduced NADP (used in LIR)
- oxygen (used in respiration/diffuses out stomata)
14
Q
Light independent reaction (LIR)
A
- Calvin cycle
- uses CO2, reduced NADP and ATP to form hexose sugar
- occurs in stroma which contains the enzyme Rubisco
- temperature-sensitive
15
Q
Calvin cycle
A
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16
Q
RuBP
A
- Ribulose Bisphosphate
- 5-carbon molecule
17
Q
GP
A
- Glycerate-3-phosphate
- 3-carbon molecule
18
Q
Triose Phosphate
A
- 3-carbon molecule
- GP is reduced to form triose phosphate in the Calvin cycle.
- Triose phosphate is oxidised to form pyruvate in glycolysis.
19
Q
Producing hexose sugar in LIR
A
- Takes 6 cycles
- glucose can join to form disaccharides (sucrose) or polysaccharides (cellulose)
- can be converted to glycerol to combine with fatty acids to make lipids
20
Q
Limiting factor
A
- A factor which, if increased, the rate of the overall reaction also increases.
21
Q
Limiting factors of photosynthesis
A
- Light intensity
- CO2 concentration
- temperature
22
Q
How light intensity limits photosynthesis?
A
- If reduced, levels of ATP and reduced NADP would fall
◦ LDR limited – less photolysis and
photoionisation - GP cannot be reduced to triose phosphate in LIR
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23
Q
How temperature limits photosynthesis?
A
- LIR inhibited – enzyme controlled (Rubisco)
- up to optimum, more collisions and E-S complexes
- above optimum, H-bonds in tertiary structure break, active site changes shape – denatured
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24
Q
How CO2 concentration limits photosynthesis?
A
- If reduced, LIR inhibited
- less CO2 to combine with RuBP to form GP
- less GP reduced to TP
- less TP converted to hexose and RuBP regenerated
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25
Agricultural practices to maximise plant growth
* Growing plants under **artificial lighting** to maximise light intensity
* heating in **greenhouse** to increase temperature
* **burning fuel** to release CO2
26
Benefits of agricultural practices for plant growth
* Faster production of glucose → faster **respiration**
* more ATP to provide energy for growth e.g. cell division + protein synthesis
* higher yields so more **profit**
27
Products of LIR
* **Hexose sugar**
* **NADP** – used in LDR
28
Stages of aerobic respiration
1. Glycolysis
2. Link reaction
3. Krebs cycle
4. Oxidative phosphorylation
29
Location of glycolysis
* Cytoplasm
30
Glycolysis
* **Substrate level phosphorylation** – 2 ATP molecules add 2 phosphate groups to glucose
* **glucose phosphate** splits into two **triose phosphate** (3C) molecules
* both TP molecules are oxidised (reducing NAD) to form 2 **pyruvate** molecules (3C)
* releases 4 ATP molecules
31
Coenzymes
* A molecule which aids/assists an enzyme
* **NAD** and **FAD** in respiration both gain hydrogen to form reduced NAD (NADH) and reduced FAD (FADH)
* **NADP** in photosynthesis gains hydrogen to form reduced NADP (NADPH)
32
Products of glycolysis
* Net gain of 2 ATP
* 2 reduced NAD
* 2 pyruvate molecules
33
How many ATP molecules does glycolysis produce?
* 2 ATP molecules used to phosphorylate glycose to glucose phosphate
* 4 molecules generated in oxidation of triose phosphate to pyruvate
* **net gain 2 ATP** molecules
34
Location of the link reaction
* Mitochondrial **matrix**
35
Link reaction
* Reduced NAD and pyruvate are actively transported to matrix
* pyruvate is **oxidised** to **acetate** (forming reduced NAD)
* carbon removed and CO2 forms
* acetate combines with coenzyme A to form **acetylcoenzyme A** (2C)
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36
Products of the link reaction per glucose molecule
* **2 acetylcoenzyme A** molecules
* **2 carbon dioxide** molecules released
* **2 reduced NAD** molecules
37
Location of the Krebs cycle
* Mitochondrial **matrix**
38
Krebs cycle
* Acetylcoenzyme A combines with 4C molecule to produce a 6C molecule – enters cycle
* **oxidation-reduction** reactions
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39
Products of the Krebs cycle per glucose
* 8 reduced coenzymes
◦ 6 reduced NAD
◦ 2 reduced FAD
* 2 ATP
* 4 carbon dioxide
40
Location of oxidative
phosphorylation
* **Cristae** of mitochondria
41
Mitochondria structure
* **Double membrane** with inner membrane folded into **cristae**
* **enzymes** in matrix
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42
Role of reduced coenzymes in oxidative phosphorylation
* Accumulate in mitochondrial matrix, where they release their **protons** (H+) and **electrons** (e-)
* **regenerate NAD** and **FAD** to be used in glycolysis/link reaction/Krebs cycle
43
Role of electrons in oxidative phosphorylation
* Electrons pass down series of electron carrier proteins, losing energy as they move
* energy released **actively transports H+** from mitochondrial matrix to inter-membranal space
* **electrochemical gradient** generated
44
How is ATP made in oxidative
phosphorylation?
* Protons move down **electrochemical gradient** back into matrix via **ATP synthase**
* ATP created
* movement of H+ is **chemiosmosis**
45
Role of oxygen in oxidative phosphorylation
* Oxygen is the **final electron acceptor** in electron transport chain
* oxygen combines with protons and electrons to form **water**
* enables the electron transport chain to continue
46
How would lack of oxygen affect respiration?
* Electrons can’t be passed along the electron transport chain
* the **Krebs cycle and link reaction stop** because NAD and FAD (converted from reduced NAD/FAD as they release their H atoms for the ETC), cannot be produced.
47
Oxidation
* **Loss of electrons**
* when a molecule loses hydrogen
48
Reduction
* **Gain of electrons**
* a reaction where a molecule gains hydrogen
49
Location of anaerobic respiration
* Cytoplasm
◦ glycolysis only source of ATP
50
Anaerobic respiration in plants & microbes
* Pyruvate produced in glycolysis is **reduced** to form **ethanol and CO2**
* pyruvate gains hydrogen from reduced NAD
* reduced NAD oxidised to NAD so can be **reused** in glycolysis
* 2 ATP produced
51
Anaerobic respiration animals
* Pyruvate produced in glycolysis is **reduced** to form **lactate**
* pyruvate gains hydrogen from reduced NAD
* reduced NAD oxidised to NAD so can be **reused** in glycolysis
* 2 ATP produced
52
Other respiratory substances
* **Fatty acids** and **amino acids** can enter the **Krebs cycle** for continued ATP synthesis
53
Lipids as respiratory substances
* **Glycerol** from lipid hydrolysis converted to **acetylcoenzyme A**
* can enter the Krebs cycle
54
Proteins as respiratory substances
* **Amino acids** from protein hydrolysis can be converted to **intermediates** within Krebs cycle
55
Producers
* **Plants**
* produce their own carbohydrates from carbon dioxide **(autotrophs)**
* start of a food web
56
Energy transfer between trophic levels
* **Biomass** and its stored energy is transferred through trophic levels **very inefficiently**
* most energy is lost due to **respiration** and **excretion**
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Consumers
* **Heterotrophs** that cannot synthesise their own energy
* obtain chemical energy through **eating**
58
Biomass
* Measured in terms of:
◦ **mass of carbon**
◦ **dry mass of tissue** per given area
59
How is dry mass of tissue estimated?
* Sample of organism **dried** in oven below 100C (avoiding combustion + loss of biomass)
* sample **reweighed** at regular intervals
* all water removed when **mass constant**
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Why is dry mass a representative measure of biomass?
* **Water content** in tissues **varies**
* heating until constant mass allows **standardisation** of measurements
* for comparison
61
Calorimetry
* Laboratory method used to estimate chemical **energy stored** in dry **biomass**
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Calorimetry method
* Sample of dry biomass is **burnt**
* energy released used to heat known **volume** of water
* **change in temperature** of water used to calculate chemical energy
63
Gross primary production
* Chemical energy **stored in plant biomass**, in a given area/volume
* total energy resulting from photosynthesis
64
Net primary production
* Chemical energy stored in plant biomass **after respiratory losses**
* available for plant growth and reproduction – **create biomass** available to other trophic levels
65
Calculating net primary production
* **NPP = GPP - R**
* R = respiratory losses to the environment
66
Calculating net production of consumers (N)
* **N = I - (F + R)**
* I = chemical energy store in ingested food
* F = chemical energy store in faeces/urine
* R = respiratory losses
67
Units of productivity rates
* **kJ Ha-1 year-1**
* kJ is the unit for energy
68
Why is productivity measured per area?
* Per hectare (for example) is used because environments **vary in size**
* **standardises** results so environments can be compared
69
Why is productivity measured per year?
* More **representative** of productivity
* takes into account effects of **seasonal variation** (temperature) on biomass
* environments can be compared with a **standardised** amount of time
70
Why is energy transfer inefficient from sun → producer?
* Wrong **wavelength** of light – not absorbed by chlorophyll
* light strikes non-photosynthetic region (bark)
* light **reflected** by clouds/dust
* lost as **heat**
71
Why is energy transfer inefficient after producers?
* **Respiratory loss** – energy used for metabolism (active transport)
* lost as **heat**
* not all plant/animal eaten (bones)
* some food **undigested** (faeces)
72
Farming practices to increase energy transfer for crops
* Simplifying food webs to reduce energy/biomass
◦ **herbicides** kill weeds → less competition
◦ **fungicides** reduce fungal infections
* results in **more energy available to use to create biom to create biomassass**
* **fertilisers** such as nitrates to promote growth
73
Farming practices to increase energy transfer for animals
* Reducing respiratory losses **(more energy** to **make biomass)**
◦ restrict **movement**
◦ keep **warm**
* slaughter animal when young (most energy used for growth)
* **selective breeding** to produce breeds with higher growth rates
74
Saprobionts
* Feed on remains of dead organisms and their waste products (faeces/urea) and break down organic molecules
* secrete enzymes for **extracellular digestion**
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Mycorrhizae
* **Symbiotic relationship** between fungi and roots of plants
* fungi act as extensions of roots
* increase surface area of system – increasing rate of absorption
* **mutualistic relationship** as plants supply fungi with **carbohydrates**
76
Importance of nitrogen to organisms
* Used to create
◦ amino acids/proteins
◦ DNA
◦ RNA
◦ ATP
77
Nitrogen cycle stages
* Nitrogen fixation
* nitrification
* denitrification
* ammonification
78
Nitrogen fixation
* **Nitrogen fixing bacteria** break triple bond between two nitrogen atoms in nitrogen gas
* fix this nitrogen into **ammonium ions**
79
Nitrogen fixing bacteria
* Fix nitrogen gas into
**ammonium ions**
* free living in soil
* or form **mutualistic relationship** on root nodules of leguminous plants
◦ give plants N in exchange for carbohydrates
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Nitrification
* Ammonium ions in soil are **oxidised** to **nitrite ions**
* nitrite ions are oxidised to **nitrate ions**
* by **nitrifying bacteria**
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Denitrification
* Returns nitrogen in compounds back into **nitrogen gas** in atmosphere
* by **anaerobic denitrifying bacteria**
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Ammonification
* Proteins/urea/DNA can be **decomposed** in dead matter and waste by **saprobionts**
* return **ammonium ions** to soil – saprobiotic nutrition
83
Importance of phosphorus
* Used to create:
◦ DNA
◦ RNA
◦ ATP
◦ phospholipid bilayers
◦ RuBP/GP/Triose phosphate
84
Phosphorus cycle
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85
Fertilisers
* **Replace nutrients** (nitrates and phosphates) lost from an ecosystem's nutrient cycle when
◦ crops are harvested
◦ livestock removed
* can be **natural (manure)** or **artificial (inorganic chemicals)**
86
Natural fertilisers advantages
* **Cheaper** than artificial fertilisers
◦ often free if farmer has own animals – recycle manure
* organic molecules have to be broken down first by saprobionts so **leaching less likely**
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Artificial fertilisers advantages
* Contain **pure chemicals** in **exact proportions**
* more **water-soluble**, so more ions dissolve in water surrounding soil
◦ higher absorption
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Natural fertilisers disadvantages
* Exact minerals and proportions
**cannot be controlled**
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Artificial fertilisers disadvantages
* High solubility means larger quantities can **leach** away with rain
◦ risking **eutrophication**
* **reduce species diversity** as favour plants with higher growth rates e.g. nettles
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Leaching
* When water-soluble compounds are **washed away** into rivers/ponds
* for nitrogen fertilisers, this can lead to **eutrophication**
91
Eutrophication
* When nitrates leached from fields stimulate growth of **algae**
* **algal bloom**
* can lead to **death of aquatic organisms**
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How does eutrophication lead to death of aquatic organisms?
* Algal bloom creates blanket surface of water **blocking light**
* plants cannot **photosynthesise** and die
* **aerobic bacteria** feed and respire on dead plant matter
* eventually, aquatic organisms die due to **lack of dissolved oxygen** in water
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Mutualistic relationships
* A type of **symbiotic relationship** where all species involved benefit from their interactions
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Role of saprobionts in nitrogen cycle
* They use **enzymes** to **decompose** proteins/DNA/RNA/urea
* releasing **ammonium ions**
