1
Q
What is the balanced symbol equation for photosynthesis?
A
6CO2(g) + 6H2O(l) -> 6O2(g) +C6H12O6
2
Q
How is the chloroplast structure adapted to their fucntion?
A
- have stacks of thylakoids (grana), providing a large surface area for attatching chlorphyll, electrons and enzymes
- network or proteins in grana hold chlorophyll in a orientation to absorb more light
- granal membranes have ATP sunthase channels which are selectively permeable to create a proton gradient
- have DNA and ribosomes to synthesise proteins
3
Q
What is oxidation and reduction?
A
oxidation- when a substance loses elctrons, lose H+
reduction- when a substance gains electrons, gain H+
4
Q
What is a photosystem?
A
- funnel-like structures in the thylakoid membrane
- made from accesory pigments (cluster), absorbing light energy to transfer it to primary pigment reaction centre (chlorophyll)
- energy funneled tor eaction centre causes photoionisation of chlorophyll, loss of an electron
5
Q
What is the role of coenzymes?
A
pick up and provide hydrogen atoms to complete a reaction and make a substance
6
Q
What is the first stage of photosynthesis?
A
Light Dependent Reaction:
- chlorophyll / photosystem absorbs light;
- electron lost by chlorophyll in photoionisation
- splitting of water / photolysis replaces electron;
- passing of excited electrons between chlorophyll molecules in photosystems;
- electron passed from photosystem II to carriers (in thylakoid membrane);
- production of ATP in this way is called photophosphorylation;
- electron causes pumping of protons into the thylakoid;
- proton gradient used by ATPase to drive ATP production;
- electron passes to photosystem I at end of carrier chain;
- electron re-excited and emitted by photosystem I;
- electron passed to / used to reduce NADP+;
- NADPH + H+ / reduced NADP produced;
- cyclic photophosphorylation using photosystem I, electron carriers and ATPase only;
7
Q
What is the second stage of photosynthesis?
A
Light Independent Reaction: Calvin Cycle
- light-independent reaction fixes CO2;
- to make glycerate 3-phosphate;
- glycerate 3-phosphate / GP / phosphoglyceric acid becomes reduced;
- to triose phosphate / phosphoglyceraldehyde / glyceraldehyde 3-phosphate;
- using NADPH;
- using ATP;
- ATP needed to regenerate RuBP;
- ATP is made in light-dependent reactions;
- light causes photoactivation / excitation of electrons;
- flow of electrons causes pumping of protons into thylakoid;
- ATP formation when protons pass back across thylakoid membrane;
- electrons are passed to NADP / NADP+;
- NADPH produced in the light dependent reactions;
8
Q
What are the limiting factors of photosynthesis?
A
- light intensity- graph increases then plateaus
- CO2 concentration- graph increases then plateaus
- temperature- graph increases then decreases (as enzyme denatures)
9
Q
What is the balanced symbol equation for respiration?
A
6O2(g) +C6H12O6 -> 6CO2(g) + 6H2O(l)
10
Q
How is the mitochondria structure adapted to their fucntion?
A
- rod shaped organelles, 0.5-1μm
- site of aerobic respiration in eukaryotic cells, synthesises ATP
- organelles: matrix, cristae, ribosomes, circular DNA
- double membrane structure, with an inner layer with many folds to create a high surface area
11
Q
Why is respiration important?
A
- provides energy required for condensation ADP-> ATP
- for each 30.5kJmol-1 of energy released by hydrolysis of ATP, the same energy must also be input from respiration to reform ATP
- energy from condensation reaction comes from chemical energy in glucose
- releases small packets of energy to prevent cell damage so minimal energy is wasted
12
Q
What substances are required for repsiration?
A
- glucose and oxygen
- ADP & ATP
- co-enzymes: NAD, FAD, co-enzyme A
13
Q
What are the 4 stages of respiration?
A
- glycolysis
- link reaction
- kreb cycle
- oxidative phosphorylation/ electron transport chain
14
Q
What is the glycolysis stage of respiration and where does it take place?
A
- in the cytoplasm
- no O2 requires
- glucose splits into 2 pyruvates (3C) sugar
- 2 parts: energy investment phase and energy pay off phase
15
Q
What occurs during glycolysis?
A
phosphorylation: glucose(6C) -> hexose-1,6-bisphosphate(6C)
- 2ATP -> 2ADP
lysis: hexose-1,6-bisphosphate(6C) -> TP(3C) TIMES 2
oxidation: 2TP(3C) -> intermediate 3C
- ADP -> ATP
- NAD -> NADH
dephosphorylation: intermediate 3C -> pyruvate
- ADP -> ATP
16
Q
What is the link reaction stage of respiration and where does it take place?
A
- occurs in matrix of mitochondria (pyruvate moves in)
- enzyme controlled reaction
- pyruvate converted into acetyl CoA
17
Q
What occurs during the link reaction?
A
- start with pyruvate (2 per glucose)
- decarboxylated (remove CO2)
- add enzyme CoA
- oxidised as NAD converted to reduced NADH
- produces acetyl coA (2C)
18
Q
What is the krebs cycle stage of respiration and where does it take place?
A
- occurs in mitochondiral matrix
- involves redox reactions
- 2 cycles per glucose
- occurs 6 times for balanced equation
- TP used to generate useful organic substances
19
Q
Why is the krebs cycle significant?
A
- breaks larger molecules into smaller ones
- produces H atoms, essential to reduce coenzymes for use in oxidative phosphorylation
- regenerates 4C molecule w/ acetyl Co A to restart cycle
- source of intermediate compounds to be used in cells in body
20
Q
What occurs during the krebs cycle?
A
- acetyl CoA (2C) joins to oxaloacetate (4C) to form** citrate (6C)**
- citrate (6C) gets oxidised as NAD reduced to NADH and gets decarboxylated to form intermediate 5C
- intermediate 5C gets oxidised as NAD reduced to NADH and getd decarboxylated to form intermediate 4C
- intermediate 4C dephosphorylates (ADP -> ATP), is oxidised (FAD -> FADH and NAD -> NADH) to reform oxaloacetate (4C)
21
Q
What is the use of TP?
A
TP: used to produce hexose phosphates (6C), which can be used to produce starch, sucrose or cellulose, lipids for cell membranes and amino acids for protein synthesis
22
Q
What is the oxidative phosphorylation stage of respiration and where does it take place?
A
- highest no. of ATP produced
- uses H from co-enzymes
- takes place in cristae membrane and intermembrane space
23
Q
What occurs during oxidative phosphorylation?
A
- NADH and FADH releases H atom, which splits into an electron and proton (H+)
- electrons get excited and move through the e.t.c. in redox reactions, transferring/ losing energy
- energy released used to synthesise ATP and pump protons into i.m. space, creating an electrochemical gradient
- H+ ions want to move in due to gradient, using ATP synthase channels which convert ADP+Pi to ATP as the channels change shape
- oxygen combines with protons in ATP synthase channels and electrons in e.t.c.: O2 + 4H+ + 4e- -> 2H2O (oxygen acts as electron acceptor)
- NAD & FAD go back to earlier stages in respiration
24
Q
What is anaerobic respiration?
A
- respiration without O2 present
- occurs in cytoplasm (mainly glycolysis as NAD/FAD can’t be used in these stages)
- if no O2, NADH & FADH can’t be reoxidised in e.t.c. as there’s an absence of O2 to pick up H and e-
25
How does anaerobic respiration occur in mammals?
**lactate fermentation:**
- occurs in mostly muscle cells when ATP demand is high and O2 deficit
- in animals and some bacteria
- oxidised NAD reused in glycolysis as H carrier produces 2ATP
- **pyruvate(3C) -> lactate(3C)**
- lactate dehydrogenase used to reoxidise NADH to NAD
26
How does anaerobic respiration occur in plants and fungi:
**ethanol fermentation:**
- pyruvate decarboxylated, accept H
- oxidised NAD reused
- **pyruvate(3C) -> ethanal(2C) -> ethanol(2C)**
- uses pyruvate decarboxylase to convert pyruvate to ethanal, losing CO2
- uses ethanol dehydrogenase to convert ethanal to ethanol, reoxidising NADH to NAD
27
What is a respiratory substrate?
- the organic nutrients oxidised at the time of respiration
- oxidation of organic nutrients occurs to obtain energy (ATP)
- order of preference of organic nutrients as respiratory substrates are – carbohydrates, lipid, proteins
28
How does lipids act as a respiratory substrate?
- important for many tissues (e.g. muscle)
- lipids are hydrolysed to fatty acids and glycerol
- **glycerol is phosphorylated, converted into TP** which can then enter the glycolysis pathway
- **fatty acid broken down** into 2C fragments, into** acetyl CoA**
- generates **NADH, FADP & acetyl CoA** to enter the Krebs cycle
- oxidation of lipids produces many 2C molecules used in oxidative phosphorylation
- for the same mass, **lipids release more than 2x the energy of carbohydrates as they produce more ATP**
29
How does proteins act as a respiratory substrate?
- amino acids used as substrates in excess
- **proteins first hydrolysed to individual amino acids**, taken to liver where amino group is removed in deamination
- removed amino group converted to urea, moved by kidneys as waste
- **remaining amino acid converted to an intermediate**
- **no. of carbon atoms involved determines next step e.g. 3C= pyruvate**
30
What is biomass?
- organic material that makes/ is produced living things
- mass of carbon or dry mass of tissue per given area
31
How is energy lost at each trophic level?
- energy always disspiated as heat loss (in respiration/ faeces)
- lost as not all an organism is consumed (e.g. bones) and not all energy available for the next organism
- less energy available to sustain living tissue at higher food chain level
32
What are the types of pyramids measuring energy transfer?
- **numbers**
- **biomass-** dry mass of living material
- **energy** released per unit mass
33
What are limitations of the pyramid of biomass?
- takes into account size of organism but it's only a snapshot of the amount of material present at a given time
- changes at different times of the year
- doesn't state the date of primary consumers (e.g. excretes/ not eaten/ faeces)
34
What do pyramids of energy represent?
- more accurate representation of flow of energy (energetics) obtained by measuring energy content material and displaying info0. as pyramids of energy
- using energy valuyes determined from given area over a specified period of time for each trophic level (e.g. kJm-2yr-1)
35
How can the chemical energy store in dry biomass can be estimated?
using calorimetry/ bomb calorimeter
36
How does a bomb calorimeter work?
- determines energy content of material by burning a known mass of dry material in pure oxygenn
- results in complete combustion, an accurate measure of energy content
37
Why is dry mass used to measure energy transfer?
- potential energy contained in sample in kJ where 4.24KJ equal to heat required to raise temp. of 1kg of water by 1°C
38
What is the equations required for energy released and energy for pyramid?
- energy released= mass x s.h.c x △t
- energy for pyramid= H2O energy released ÷ biomass burned/ kg ÷ time
39
Where does primary and secondary production come from?
- **primary production-** producers
- **secondary production-** consumers
40
What is gross primary production (GPP)?
chemical energy store in plant biomass, in a given area or volume
41
What is net primary production (NPP)?
the chemical energy store in plants biomass after respiratory losses to the environment have been taken into account
**NPP= GPP - R(respiratory losses)**
- NPP available for plant growth/ reproduction and to other trophic levels (conumers) in the ecosytstem
42
What is secondary production?
energy used to make new consumer tissue
43
What is net production of consumers equation?
N= I - (F+R)
44
What is the equation for efficiency?
efficiency= (net production of trophic level/ net production of previous trophic level) x 100
45
How do you increase efficiency?
reduce energy lost to other organisms and respiration:
- simplifying food webs resuces energ loss to other organisms
- reducing respiratory losses, energy transferred more efficiently
46
How does simplifying food webs increase efficiently?
| non-human food chain
- reduce pest numbers, using **chemical pesticides**
- **intensive farming**/ integrated system using chemical and biological methods, increase NPP
- **biological agents** reduce pest no.s, crops lose less energy and biomass, increasing efficiency of energy transfer
47
How does reducing respiratory losses increase efficiency?
- increase net production of livestock, control conditions they live in so **energy used for growth, not used in respiration**
- **restricting movement** (keep livestock indoors in pens, warmer conditions
- more biomass produces, more chemical energy stores, **increasing NPP and efficiency of energy transfer to humans**
- more food produced at low cost in shorter time, however restricts natural behaviour
48
How does the natural ecosystm work?
- hasn't been changed by human activity, recycles nutrients in foodworks
- microorganisms (e.g. fungi and bacteria) play important roles in fod webs
49
What are saprobionts?
- a type of **decomposer**
- feeds on remains of dead plants and animals and on their waste products, breaking them down to **recycle chemical elements**
- secrete enzymes, digest their food externally and **absorb nutrients they need (extracellular digestion)**
- organic molecules get broken down into inorganic ions, (obtaining nurients- **saprobiotic nutrition**)
50
What are mycorrhizae?
- **saprophtic fungi that form a symbiotic/ mutualistic relationship w/ plant roots**
- saprobionts/ fungi made up of long, this strands (**hyphae**) connected plant roots
- hyphae **increase surface area** of plants root system, so they can absorb ions and form soil that are unusually scarce (e.g. PO4-) and **increase H2O uptake**
- in turn, **fungi obtain organic compounds** (e.g. glucose) from the plant
51
Why is the nitrogen cycle required?
- needed to make **proteins and nucleic acids**
- atmosphere 78% N2 gas but can't be used in that form
- essential for **genetics, plant growth and therefore for the food we grow**
- artificial fertelisers/ lightning can also fix atmospheric nitrogen
52
Why is the phosphorus cycle required?
- needed for **phospholipids (cell membranes), DNA and ATP**
- found in rocks, dissolved in oceans
- travel by erosion/ run off
- found in guano (bird excretion)
53
What is the nitrogen cycle?
1. nitrogen fixation: N2 -> NH3 -> NH4+
2. ammonification: dead -> NH3 -> NH4+
3. nitrification: NH4+ -> NO2- -> NO3-
4. denitrification: NO3- -> N2
54
What occurs in nitrogen fixation?
- **N2 -> NH3 > NH4+**
- when N2 gas converted into nitrogen containing compounds (NH3/ ammonia) which goes on to form ammonium ions in solution **(used by plants)**
- carried out by **nitrogen fixing bacteria** (e.g. rhizobium)
- found in root nodules of leguminous plants
- form mutualistic relationship (provide plants with N, plants provide them with carbohydreates)
55
What occurs in ammonification?
- **dead -> NH3 -> NH4+**
- when **nitrogen compounds from dead organisms are converted into ammonia by saprobionts**, which then form ammonium
- **animal waste (e.g. urine and faeces) turned into ammonia by saprobionts** and ammonia with nitrogen compounds
56
What ocurs in nitrification?
- **NH4+ -> NO2- -> NO3-**
- when ammonium ions in the soil are converted into nitrites then itrates to be **used by plants**
- occurs in **aerobic conditions**
- **nitrifying bacteria** (nitrosomonas): ammonium -> nitrites
- **nitrifying bacteria** (nitrobacter): nitrites -> nitrates
57
What occurs in denitrification?
- **NO3- -> N2**
- when nitrates i soil are converted into nitrogen gas by **denitrifying bacteria**
- use nitrates in soil to respire, producing N2 gas
- happens under **anaerobic conditions (no O2, e,g, water logged soils)**
58
What occurs in the phosphorys cycle?
- phosphate ions in **rocks** are released into soil be **weathering**
- phosphate ions are taken into plants by **roots (mycorrhizae greatly increase rate which phosphorus can be assimilated/ absorbed)**
- phosphate ions transferred through the **food chain** when consumed
- phosphate ions lost from animals in **waste products/ excretion**
- when plants and animals die, **saprobionts** break down the organic compounds, releasing phosphate ions into soil for **assimilation** by plants
- saprobionts also release phosphate ions from **urine and faeces**
- **weathering of rocks** also releases phosphate ions into seas, lakes and rivers
- this is taken up by **aquatic producers** (e.g. algae) and passed along the food chain to birds
- **waste produced by sea birds (guano)** and contains high proportion of phosphate ions
- guano returns lots of phosphate to soild, often used as **natural ferteliser**
59
Why do farmers use fertelisers?
- when crops are harvested their minerals and nutrients aren't returned to the soil or replaced
- fertelisers used to **replace minerals that haven't been returned to the soil**
- so more energy from the ecosystem can be used for **growth and to increase efficiency**
60
What are the types of fertelisers?
- natural (organic matter)
- artificial (inonganic matter)
61
What are natural fertelisers?
- **composed of organic matter, improves soil structure**
- nutrients release over long periods of time
- not highly concentrated so large amounts required
- e.g. manure, compost vegetables, crop residues, kelp
62
What are artificial fertelisers?
- **inorganic matter, contain pure chemical compounds**
- **known concentration**: know how much to apply and yield outcome
- highly concentrated: small amounts needed, lower transport costs
- e.g. ammonium nitrate, ammonium phosphate
63
What are environmental issues with fertelisers?
- sometimes more ferteliser applied than plants able to use (leads to **leaching**)
- **leaching-** when water soluble compounds in soik wash away into ponds, rivers nearby by rain/ irrigation systems
- inorganic ions in chemical ions are **relatively soluble**
- excess minerals aren't used immediately, easy to leach
- **leaching less likely in natural fertelisers**, N & P need to decompose by microorganisms before absorption, more controlled uptake by plants
- P less water soluble than N, leaching less likely
- ferteliser changes **balance of nutrients in soil**
- too much of a nutrient causes crops/ other plants death
64
What is eutrophication?
1. mineral ions leached from fertelsied fields stimulates **rapid algae growth** in ponds and rivers
2. large amounts of algae **blocks light** from reaching plants below
3. eventually **plants die** as they don't have sunlight and so **can't photosynthesise**
4. **bacteria** feed on dead plant matter, increased no. of bacteris **reduce O2 conc.** in water by carrying out **aerobic respiration**
5. fish and aquatic organisms **die** as there isn't enough O2 dissolved
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