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A2 Biology > Topic 5: Energy Transfer In And Between Organisms > Flashcards

Topic 5: Energy Transfer In And Between Organisms Flashcards

1
Q

3.5.1 Photosynthesis

What is photosynthesis?

A
  • Photosynthesis is a reaction in which light energy is used to
    produce glucose in plants. The process requires water and carbon
    dioxide, with the products being glucose and oxygen.
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2
Q

What are the two key stages of photsynthesis?

A
  • the light dependent reaction
  • the light independent reaction
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3
Q

What factors affect the rate of photosynthesis?

A
  • carbon dioxide concentration
  • light intensity
  • temperature
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4
Q

What are the four key stages in the light dependent reaction?

A
  1. Photolysis of water
  2. Photoionisation
  3. Chemiosmosis
  4. Production of ATP and reduced NADP
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5
Q

How are chloroplasts adapted for photosynthesis?

A
  • contains stacks of thylakoid membrane called the grana, these are folded to provide a large surface area for the attachment of chlorophyll, electrons and enzymes
  • the granal membrane has ATP synthase channels embedded allowing ATP to be synthesised and its selectively permeable which creates a proton gradient
  • chloroplasts contain DNA and ribosomes allowing them to synthesise proteins needed in the light dependent reaction
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6
Q

What happens in photolysis?

A
  • light energy is absorbed by the chloropyll
  • this splits water into oxygen protons and electrons
  • the protons are used to create reduced NADP and is used in the LIR
  • the electrons are passed along a chain of electron carrier proteins
  • the oxygen is either used for respiration or diffuses out of the leaf through the stomata
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7
Q

How many photons of light is required to split one molecule of water?

A
  • 4 photons of light are required to split one molecule of water
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8
Q

How many molecules of oxygen protons and electrons does the photolysis of water produce?

A
  • 1 molecule of oxygen
  • 4 protons
  • 4 electrons
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9
Q

What happens in photoionisation?

A
  • The light energy absorbed by the chloropyll results in the electrons becoming excited
  • the electrons raise up an energy level and leave the chloropyll
  • chloropyll becomes positively charged and has now been ionised
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10
Q

What is some of the energy released from the electrons in photoionisation used for?

A
  • is conserved in the production of ATP and
    reduced NADP
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11
Q

What happens in chemiosmosis?

A
  1. the electrons move along a series of proteins embedded within the thylakoid membrane
  2. As the electrons move along the proteins they release energy and some of this energy is used to pump the protons across chloroplasts membranes
  3. An electrochemical gradient is created. The protons pass through the enzyme ATP synthase by facilitated diffusion which phosphorylates ATP from ADP + pi
  4. The protons combine with coenzyme NADP to become reduced NADPH
  5. Because the protons move from an area of high to low concentration gradient. This is known as chemiosmosis
  6. NADPH and ATP are now used in the LIR
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12
Q

Where does the light independent reaction take place?

A
  • the stroma
  • also known as the calvin cycle
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13
Q

What is the enzyme involved in the LIR?

A
  • Rubisco which catalyses the reaction
  • the stage is temperature reactive due to the fact it contains enzymes
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14
Q

What does the calvin cycle use to form a hexose sugar?

A
  • CO2
  • reduced NADP
  • ATP
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15
Q

What is the role of ATP and NADPH in the calvin cycle?

A
  • ATP is hydrolysed to provide energy for the reaction
  • reduced NADP donates the hydrogen to reduces the molecule GP in the cycle
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16
Q

What are the main stages in the calvin cycle?

A
  1. carbon dioxide fixation
  2. reduction phase
  3. regeneration of RuBp
  4. organic molecule production
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17
Q

What happens in the first stage of the calvin cycle (carbon dioxide fixation)?

A
  • CO2 reacts with ribulose bisphosphate (RuBP) in a process known as carboxylation
  • to form 2 molecules of GP a three carbon compound
  • this reaction is catalysed by the enzyme rubisco
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18
Q

What happens in the second stage of the calvin cycle (reduction phase)?

A
  • GP is reduced by reduced NADP to form 2 molecules of TP and also energy is used by ATP
  • All of the NADP from the LDR has been used
  • Only some of the ATP has been used
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19
Q

What happens in the third stage of the calvin cycle (regeneration of RuBP)?

A
  • Some of the carbon from TP leaves the cycle each turn to be converted into useful organic substances
  • 5 molecules of triose phosphate are used in order to regenerate 3 molecules of RuBP
  • The remaining amount of ATP from the light
    stage is now used.
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20
Q

What happens in the last stage of the calvin cycle (organic molecule production)?

A
  • 2 molecules of triose phosphate can combine to form
    the intermediate hexose sugar
  • whilst glucose is the product this monosaccharide can join to form disaccharides such as sucrose and polysaccharides such as cellulose and starch
  • glucose can also be converted to glycerol and therefore combine with fatty acids to make lipids for the plant
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21
Q

How many turns of the calvin cycle are needed to produce 1 molecule of glucose per molecule of CO2?

A
  • 6 turns of the Calvin Cycle are required in order to produce 1 molecule of glucose per
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22
Q

Describe the structure of a chloroplast

A
  • usually disc shaped
  • Double membrane
  • Thylakoids-flattended discs stack to form grana
  • Intergranal lamellae
  • stroma-fluid filled matrix
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23
Q

How does the structure of the chloroplast maximise the rate of the LDR?

A
  • ATP synthase channels within granal membrane
  • Large surface area of thylakoid membrane for ETC
  • photosystems position chlorophyll to enable maximum absorption of light
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24
Q

How does the structure of the chloroplast maximise the rate of the LIR?

A
  • own DNA and ribosomes for synthesis of enzymes e.g. rubisco
  • concentration of enzymes and substrates in stroma is high
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25
What are the limiting factors of photosynthesis ?
* Light intensity (LDR) * CO2 levels (LIR) * Temperature (enzyme controlled steps) * Mineral/magnesium levels (maintain normal functioning of chloropyll * Chlorophyll concentration
26
Wnat are some techniques agricultural producers incorporate to remove limiting factors?
* growing plants with artificial lighting to maximise light intensity * heating a greenhouse to increase temperature * burning fuel to release more co2
27
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
28
# ****3.5.2 Respiration**** What are the two types of respiration?
* Aerobic and Anaerobic respiration
29
What is aerobic respiration?
* Aerobic respiration is the splitting of a respiratory substrate, to release carbon dioxide as a waste product.
30
What is anaerobic respiration?
* Anaerobic respiration occurs in the absence of oxygen.
31
What are the main stages of aerobic respiration?
1. glycolysis (cytoplasm) 2. the link reaction (mitochondrial matrix) 3. the krebs cycle (mitochondrial matrix) 4. oxidative phosphorylation (inner membrane cristae of mitochrondria)
32
What happens in glycolysis?
* this is the first process of both aerobic and anaerobic respiration. * ****glucose**** is ****phosphorylated**** to ****glucose phosphate**** using ****ATP**** * This produces ****2**** molecules of ****triose phosphate**** * ****TP**** is ****oxidised**** to produce ****2 molecules of pyruvate****, with a ****net gain**** of ****2× ATP**** and ****2×NADH****
33
What happens in the link reaction?
* the ****pyruvate**** from ****glycolysis**** is ****actively transported**** into the ****mitochondrial matrix**** * ****pyruvate**** is ****oxidised**** to ****acetate**** producing ****reduced NAD**** in the process * ****acetate combines**** with ****co-enzyme A**** in the link reacrion to produce ****acetylcoenzyme A**** * ****Per glucose molecule 2 molecules of acetyl coenzyme A are formed and 0 ATP****
34
What happens in the krebs cycle?
* ****acetylcoenzyme A reacts**** with a ****four-carbon molecule****, ****releasing coenzyme A**** and ****producing a six-carbon molecule**** that ****enters the Krebs cycle**** * in a ****series of oxidation-reduction reactions****, the ****Krebs cycle generates reduced coenzymes**** and ****ATP**** by ****substrate-level phosphorylation****, and ****carbon dioxide is lost**** * The ****Krebs cycle turns 2 times**** ****per**** molecule of ****glucose**** * ****per**** molecule of ****glucose**** ****2 ATP**** molecules, ****6 NADH**** molecules, ****2 FADH**** molecules and ****4 CO2**** molecules are ****produced.****
35
What happens in oxidative phosphorylation?
* the current model for this process is the ****chemiosmotic theory**** * ****synthesis of ATP**** by ****oxidative phosphorylation**** is associated with the ****transfer of electrons down the electron transfer chain**** and ****passage of protons**** across ****inner mitochondrial membranes**** and is ****catalysed by ATP synthase**** embedded in these membranes * ****Hydrogen atoms**** are ****donated**** by ****reduced NAD**** (NADH) and ****reduced FAD**** (FADH2) ****from the Krebs Cycle**** * ****Hydrogen atoms split**** into ****protons (H+ ions) and electrons**** * The ****high energy electrons enter**** the ****electron transport chain**** and ****release energy**** as they ****move through**** the ****electron transport chain**** * The ****released energy**** is ****used**** to ****transport protons across**** the ****inner mitochondrial membrane**** from thematrix ****into the intermembrane space**** * A ****concentration gradient of protons**** is ****established between**** the ****intermembrane space and the matrix**** * The ****protons return to**** the ****matrix via facilitated diffusion**** ****through**** the ****channel protein ATP synthase**** * The ****movement of protons down**** their ****concentration gradient**** ****provides energy for ATP synthesis**** * ****Oxygen**** acts as the ****'final electron acceptor'**** and ****combines**** with ****protons and electrons**** at the ****end of the electron transport chain to form water****
36
What is the role of oxygen in aerobic respiration?
* acts as the final electron acceptor
37
What is the benefit of an electron transfer chain rather than a single electron?
* energy is released gradually * less energy is released as heat
38
What happens to the pyruvate produced in glycolysis if respiration is only anaerobic?
* pyruvate can be ****converted**** to ****ethanol or lactate**** using ****reduced NAD****. * The ****oxidised NAD produced**** in this way ****can be used in further glycolysis****.
39
Name 2 types of molecule that can be used as alternative respiratory substrates
* amino acids from **proteins** * glycerol and fatty acids from **lipids**
40
How can lipids act as an alternative respiratory substrate?
* Lipid--->glycerol+fatty acids 1. Phosphorylation of glycerol--> TP for glycolysis 2. Fatty acid--> acetate a) acetate enters lin reaction b) H atoms produced for oxidative phosphorylation
41
How can amino acids act as an alternative respiratory substrates?
* Deamination produces: 1. 3Ccompounds-->pyruvate for link reaction 2. 4C/5C compounds--> intermediates in krebs cycle
42
Name the stages in respiration that produce ATP by substrate-level phosphorylation
* Glycolysis (anaerobic) * Krebs Cycle (aerobic)
43
# ****3.5.3 Energy and ecosystems**** What is an ecosystem?
* includes all the organisms living in a particular area known as the community as well as all the non-living elements of that particular environment.
44
What is the distribution and abunance of organisms in a habitat controlled by?
* both biotic factor (living) e.g. predators, disease and abiotic factors (non-living) such as light levels and temperature. * Each species has a particular role in its habitat called its niche which consists of its biotic and abiotic interactions with the environment.
45
What are the sugars synthesised by plants used for?
* Most of the sugars synthesised by plants are used by the plant as respiratory substrates. * The rest are used to make other groups of biological molecules. * These biological molecules form the biomass of the plants.
46
What is biomass and how can it be measured?
* Total dry mass of tissue or mass of carbon measured over a given time in a specific area * The chemical energy store in dry biomass can be estimated using calorimetry
47
What is the importance of the sun?
* The sun is the source of all energy in ecosystems with photosynthetic organisms using this to produce their own food
48
Why is most of the suns energy not converted to organic matter?
* Most solar energy is absorbed by atmosphere or reflected by clouds * photosynthetic pigments cannot reabsorb some wavelengths of light * not all light falls directly on a chloropyll molecule * energy is lost as heat during respiration/photosynthesis
49
What are autotrophs?
* they are producers and make their own foods
50
What are heterotrophs?
* Those organisms that cannot synthesise their own food * all animals being these
51
What is gross primary production?
* ( GPP) is the chemical energy store in plant biomass, in a given area or volume
52
What is net primary production?
* ( NPP) is the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account, * This net primary production is available for plant growth and reproduction. * It is also available to other trophic levels in the ecosystem, such as herbivores and decomposers.
53
What is the equation that links GPP, NPP and R together?
* NPP = GPP – R where GPP represents gross production R represents respiratory losses to the environment.
54
How can the net production of consumers be calculated?
* N = I – ( F + R) I=chemical energy store in ingested F=chemical energy store lost to the environment in faeces and urine R= respiratory losses to the environment
55
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
56
What is primary and secondary productivity?
* Primary and secondary productivity is the rate of primary or secondary production, respectively. * It is measured as biomass in a given area in a given time eg kJ ha–1 year–1
57
Outline some common farming practices used to increase the efficiency of energy transfer
* Exclusion of predators- no energy lost to other organisms in a food web * Artificial heating-reduce energy lost to maintain it * Restriction of movement * Feeding is controlled at the optimum * reducing respiratory losses within a human food chain.
58
Give a general equation for % efficiency
energy converted to useful form (j) x 100 / total energy supplied (j)
59
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
60
What is a pyramid of biomass?
* Diagram that shows the biomass at each trophic level
61
Why is a pyramid of biomass preferable to a pyramid of numbers?
* shape of pyramid of numbers may be skewed since a small number of producers can support many consumers
62
# ****3.5.4 Nutrient cycles**** What happens to nutrients?
* Nutrients are recycled within natural ecosystems, exemplified by the nitrogen cycle and the phosphorus cycle.
63
What is nitrogen?
* Nitrogen is an element used in many biological molecules of which there is a finite amount on earth. * Due to this it must be recycled from dead organisms and waste products. * Most of this is carried out by bacteria in the soil.
64
What are the 4 stages of the nitrogen cycle?
1. Ammonification 2. Nitrification 3. Dentrification 4. Nitrogen fixation
65
Why cant organisms use nitrogen directly from the atmosphere?
* N2 is very stable due to strong covalent triple bond
66
# 1. What happens in ammonification?
* ****microbes**** known as ****saprobionts break down organic matter**** to ****ammonia**** in a two stage process. * Firstly, ****proteins**** are ****broken down**** into ****amino acids**** ****with**** the ****use of extracellular protease enzymes****. * These are then ****subsequently broken down further**** to ****remove amino groups**** with the ****use of deaminase enzymes**** * ****Saprobionts use**** the ****products of decomposition for respiration****.
67
What happens in nitrification?
* ****nitrifying bacteria convert ammonia**** to ****nitrite ions, NO2-**** in an ****oxidation reaction****, ****with a nitrate ion, NO3-, intermediate****. * Most ****plants**** can ****take in nitrate ions**** ****through**** their ****roots****
68
What happens in dentrification?
* ****nitrate ions****, NO3-, are ****converted to nitrogen gas****, N2, ****by**** the ****anaerobic denitryfing bacteria****. * This ****process is wasteful**** and ****can be prevented**** from ****occurring by soil**** being ****well drained and aerated****.
69
What happens in nitrogen fixation?
* ****nitrogen gas**** is ****fixed**** into ****other compounds by bacteria**** with ****nitrogen fixing ability****. * They do so ****by reducing nitrogen gas to ammonia**** ****which**** subsequently ****dissolves to form ammonium ions****. * ****Nitrogen fixing bacteria live in root nodules of leguminous plants****. * The ****relationship between nitrogen fixing bacteria**** and the ****plant is**** known as ****mutualistic****, as it is ****beneficial to both organisms****.
70
Outline the role of bacteria in nitrogen fixation
* Mutualistic nitrogen-fixing bacteria in nodules of legumes and free-living bacteria in soil * use the enzymes nitrogenase to reduce gaseous nitrogen into ammonia
71
Explain the significance of nitrogen to living organisms
* Plant roots uptake nitrates via active transport and use them to make biological molecules e.g Amino acids, NAD/NADP, nucleic acids
72
Give 3 benefits of planting a different crop on the same field each year
* Plants with nitrogen-fixing bacteria grow 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
73
Name two categories of fertiliser and state the purpose of using fertiliser
* **Organic/Natrual**-decaying organic matter and animal waste -reduced risk of leaching/eutrophication but slower release of minerals * **Inorganic/Artificial**-minerals from rocks usually containing nitrogen, phosphorus and potassium - faster release of minerals and higher concentration but risk of leaching/eutrophication and lowers water potential of soil (so plant absorbs less water by osmosis) * Purpose of **fertiliser** is to **increase gross productivity for higher yield**
74
# ``` 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
75
Outline 2 main environmental issues caused by the use of fertiliser
* **Leaching**-nitrates dissolve in rainwater and "runoff" into water sources * **Eutrophication**-water sources becomes putrid as a result of algal bloom
76
What is phosphorus?
* Phosphorus is another element found in many biological molecules that needs to be recycled. * Plants can take in phosphate ions, PO43-, from soil.
77
Name the general stages in the phosphorus cycle
* Weathering * Runoff * Assimilation * Decomposition * Uplift
78
Why is the phosphorus cycle a slow process?
* Phosphorus has no gas phase so there is no atmospheric cycle
79
What happens during weathering and runoff?
* Phosphate compounds from sedimentary rocks leach into surface water and soil
80
What is phosphate released from?
* ****Phosphate**** is ****released from sedimentary rocks**** as a ****result of weathering,**** as well as ****through the decay of bones, shells**** and the ****excreta of some birds****.
81
What happens during uplift?
* Sedimentary layers from oceans (formed by the bodies of aquatic organisms) are brought up to land over many years
82
Explain the significance of phosphorus to living organisms
* Plants convert inorganic phosphate intio biological molecules e.g. DNA ATP NADP * Phosphorus is passed to consumers via feeding
83
How does mining affect the phosphorus cycle?
* Speeds up uplift
84
What is the role and importance of mycorrhizae in the phosphorus cycle?
* Mycorrhizae are ****important**** in ****facilitating the uptake of water and inorganic ions by plants****. * These ****are associations between**** certain ****types of fungi**** and the ****roots**** of the ****vast majority of plants****. * They ****increase the surface area**** and ****act as a sponge**** ****holding water and minerals****. * As a result a ****plant can better resist drought**** and ****take up inorganic ions more easily****.
85
What are natural and artificial fertilisers used for during cycles?
* to ****replace**** the ****nitrates and phosphates lost**** by ****harvesting plants**** and ****removing livestock****.
86
What are nitrogen fertilisers used for?
* ****greatly increase crop yields**** and therefore ****can help to deal with the demands of a growing human population****. * However they have ****negative effects on the environment**** which include ****reducing biodiversity, leaching and eutrophication****
87
What is leaching?
* **process by** which **mineral ions**, such as **nitrate, dissolve in rainwater** and are **carried from the soil to end up in rivers and lakes**. * As a result of this **eutrophication occurs**
88
What is eutrophication?
* if large amounts of chemical fertilisers are sprayed onto fields and heavy rainfall occurs, the fertiliser may leach into local water sources * the fertiliser will travel and build up in ponds or lakes * Nitrates will be absorbed and used by Algae which will lead to an increase growth of algae = algal bloom * the algae grows on the upper surface of the water, this prevents light reaching the plants at the bottom of the water * these plants cannot photosynthesise, so die * these provide more nutrients to saprobiotic decomposers, so these increase in number * the decomposers will aerobically respire, using up the oxygen in the water * therefore fish die as less oxygen is available
89
How can the risk of eutrophication be reduced?
* Sewage treatment marshes on farms * pumping nutrient-enriched sediment out of water * using phosphate-free detergent

A2 Biology (4 decks)

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