20) Photosynthesis and environmental management Flashcards
(90 cards)
1
Q
Give 5 key adaptations of chloroplasts
A
- thylakoid stacking - large surface area for light dependent reactions
- organisation of photosynthetic pigments into photosystems - maximises efficiency of light energy absorption
- grana surrounded by stroma - products from light-dependent reactions can pass directly to enzymes catalysing light-independent reactions
- inner membrane less permeable than outer and is embedded with transport proteins - control over substances entering stroma from cell cytoplasm
- contain own DNA and ribosomes - can produce some of their photosynthetic proteins rather than importing them from the cell cytoplasm
2
Q
Define grana (granum sing.)
A
thylakoid stacks; site of light-dependent stage
3
Q
Define thylakoid
A
flattened membrane compartment
4
Q
Define stroma
A
fluid-filled matrix with enzymes; site of light-independent stage
5
Q
State 6 key parts of a chloroplast
A
grana thylakoid stroma intergranal lamella outer membrane inner membrane
6
Q
Describe the 4 steps of the light-dependent stage
A
- photosystem converts light energy into chemical energy (photons of light are absorbed by pigment molecules and energy is funnelled down the light-harvesting complex to a chlorophyll a molecule which is oxidised and transfers electrons (excited to a higher energy) to a primary acceptor and subsequent electron carriers
- energy is released as the electron transport chain progresses (as each new electron carrier occupies a lower energy level) and is used to pump protons across the thylakoid membrane, establishing a proton gradient
- protons flow through ATP synthase (chemiosmosis) enabling the regeneration of ADP -> ATP, used in the Calvin cycle (light independent)
- protons reduce NADP in the stroma to NADPH, used in the Calvin cycle
7
Q
Define photophosphorylation
A
the harnessing of light energy to produce ATP
8
Q
Define photolysis
A
an enzyme-catalysed reaction of photosynthesis that uses light energy to split water
9
Q
Give an equation for photolysis
A
2H2O -> 4H+ + 4e- + O2
10
Q
Where do the electrons produced by photolysis go?
A
replace those lost by the oxidation of chlorophyll a in photosystem II
11
Q
Where does the oxygen produced by photolysis go?
A
diffuses out of the leaves through stomata or is used by plant cells in aerobic respiration
12
Q
Describe the 7 steps of the light-independent reaction (Calvin cycle)
A
- carbon dioxide diffuses into the stroma
- ribulose bisphosphate, RuBP (5C) is converted to 2 molecules of glycerate 3-phosphate, GP (3C) - catalysed by the enzyme RuBisCO
- 2 x GP are reduced – (ATP -> ADP + Pi) –> 2x triose phosphate, TP (3C)
- this provides the reducing power to regenerate NADP from NADPH, which then returns to the light-dependent stage
- some TP, as a source of common respiratory substrates, is converted to useful molecules
- majority of TP is used to regenerate RuBP, which requires an extra ATP -> ADP + Pi
13
Q
Give a term to describe what happens to CO2 in the Calvin cycle
A
CO2 is fixed - converted from a gas to organic molecules
14
Q
How many molecules of ATP are required in the Calvin cycle and what for?
A
3 molecules overall
for carbon fixation reactions and the production of carbohydrates
15
Q
Describe what may happen to the small amount of TP that is converted into useful molecules
A
2TP -> 6C sugars e.g. glucose + fructose
converted to glycerol which forms triglycerides with fatty acids
16
Q
Define limiting factor
A
a variable that limits the rate of a particular process
17
Q
State 6 limiting factors of photosynthesis
A
light intensity, wavelength and duration
CO2 concentration
temperature
pH
18
Q
Explain light intensity as a limiting factor of photosynthesis
A
- positive correlation with rate of ATP + NADPH production in light dependent reactions;
- GP concentration increases; RuBP and TP concentrations decrease with increased light intensity
19
Q
Explain light wavelength as a limiting factor of photosynthesis
A
in some environments and laboratory conditions plants might not receive all wavelengths to an equal extent
20
Q
Explain light duration as a limiting factor of photosynthesis
A
daylight hours
21
Q
Explain CO2 concentration as a limiting factor of photosynthesis
A
- RuBP increases, GP limited with increasing concentration of CO2
- optimum = 0.1%, atmospheric = 0.04%
22
Q
Explain temperature as a limiting factor of photosynthesis
A
- high temperatures increase kinetic energy > denatures enzymes
- little effect on light-dependent stage as few enzymes required, except photolysis
- whereas, each light-independent reaction is catalysed by an enzyme so temperature has a more significant impact
23
Q
Explain pH as a limiting factor of photosynthesis
A
can denature proteins
24
Q
Describe the use of a photosynthometer as a method for investigating the factors affecting photosynthesis
A
- rate of oxygen production is used as a measure of photosynthetic rate
- O2(g) bubbles collected in capillary tube and volume of O2 evolved (length of bubble x Pi x r^2) per unit time calculated
- adding sodium hydrocarbonate to water generates CO2
25
Define DCPIP (2,6-dichlorophenol-indophenol)
a blue dye that acts as an electron-acceptor which becomes colourless when reduced
26
How can DCPIP be used to investigate the factors affecting photosynthesis?
enables reducing agents produced in the light-dependent reactions of photosynthesis to be detected
27
Give a method for the use of DCPIP to investigate the factors affecting photosynthesis
1. grind leaves in ice-cold sucrose 2% solution
2. centrifuge to form a pellet (high chloroplast concentration) and supernatant (low chloroplast concentration)
3. store leaf extract in ice-cold water bath
4. DCPIP solution + leaf extract pellet (light) -> generates electrons, DCPIP decolourises, green colour of chloroplasts
28
Give 4 controls that could be used when using DCPIP to investigate the factors affecting photosynthesis
DCPIP solution + leaf extract pellet (dark)
DCPIP solution + sucrose solution (light)
distilled water + leaf extract pellet (light)
DCPIP solution + supernatant (light)
29
What may you observe when using the control, DCPIP solution + supernatant (light), when using DCPIP to investigate the factors affecting photosynthesis? Why?
decolourise slowly
| may contain a low concentration of chloroplasts
30
Define compensation point
the light intensity at which the rate of photosynthesis matches the rate of respiration
31
Above compensation point...?
CO2 is taken up
| plants increase in biomass
32
Below compensation point...?
CO2 is given out
33
When is compensation point normally reached?
in early morning and evening
34
In relation to compensation point, why will increased daylight hours increases growth rates?
compensation point is exceeded for longer periods when day length increases
35
How can you investigate compensation point?
with hydrocarbonate indicator solution
atmospheric CO2 concentration = red
below compensation point, pH drops = yellow
above compensation point, pH rises = blue
36
Nitrogen cycle: nitrogen in atmosphere -> ammonium ions
nitrogen fixation by free-living bacteria using Azotobacter
37
Nitrogen cycle: nitrogen in atmosphere -> nitrogen-containing molecules e.g. proteins in producers
nitrogen fixation by mutualistic bacteria e.g. Rhizobium (live in mutualistic relationships with plants and fix N with enzyme nitrogenase in return for carbohydrates)
38
Nitrogen cycle: ammonium ions -> nitrite ions, NO2 -
nitrification by nitrifying bacteria, Nitrosomonas
| oxidation reaction releases energy
39
Nitrogen cycle: nitrite ions, NO2 - -> nitrate ions, NO3 -
nitrification, Nitrobacter
| oxidation reaction releases energy
40
Nitrogen cycle: nitrate ions, NO3 - -> nitrogen in atmosphere
denitrification by denitrifying bacteria (anaerobic and favour waterlogged soils lacking O2)
poorly aerated soils with high H2O concentration reduce availability of N containing compounds and limits growth rate
41
Define denitrification
conversion back to N(g)
42
Define nitrogen fixation
atmospheric N is converted into N-containing compounds e.g. ammonia, by nitrogen-fixing bacteria
43
Nitrogen cycle: nitrate ions, NO3 - -> nitrogen-containing molecules e.g. proteins in producers
absorption
44
Nitrogen cycle: nitrogen-containing molecules e.g. proteins in producers -> nitrogen-containing molecules e.g. proteins in consumers
feeding and digestion
45
Nitrogen cycle: nitrogen-containing molecules e.g. proteins in producers -> ammonium-containing molecules e.g. proteins in decomposers (saprobiotic microorganisms)
death
46
Nitrogen cycle: nitrogen-containing molecules e.g. proteins in consumers -> ammonium-containing molecules e.g. proteins in decomposers (saprobiotic microorganisms)
death and excretion
47
Nitrogen cycle: ammonium-containing molecules e.g. proteins in decomposers (saprobiotic microorganisms) -> ammonium ions
ammonification by saprotrophic bacteria
48
Define ammonification
breakdown of proteins, nucleic acids and vitamins from dead organisms and nitrogenous waste to produce NH3 and NH4 + and add them to soils
49
Define histology
microscopic tissue structure
50
The histology of a root nodule can be studied by...?
treating a thin section with crystal violet and observing under a light microscope
the central region stained purple contains nitrogen-fixing bacteria and is surrounded by a cortex
51
Define bioluminescence
visible light generated by an organism
52
What does a food chain illustrate?
the transfers of energy between organisms within an ecosystem
53
Define ecosystem
the organisms and non-living components of a specific area and their interactions
54
Producers convert _ energy -> _ energy and are eaten by _.
light
chemical
primary consumers
55
Define trophic level
each stage within a food chain
56
Give an equation for energy transfer
energy transfer = (energy available after transfer / energy available before transfer) x 100
57
Why is some energy lost between trophic levels?
inedible / indigestible parts
excretory waste
heat from respiration
58
Define ectotherms, give an example and how they affect their food chain
organisms which rely on external sources of heat to regulate body temperature
fish
improve the efficiency of energy transfer in their food chain
59
Give two ways of improving efficiency and sustainability in food production
fish farming / aquaculture
| promoting consumption of species low in the food chain
60
Define ruminants
animals that digest plant material slowly, in specialised stomachs, and regurgitate food to chew it a second time
61
A ruminant stomach is an ecosystem with _?
its own specific abiotic conditions (anaerobic environment)
62
Name 4 key parts of a ruminant stomach
rumen
reticulum
omasum
abomasum
63
Describe the rumen of a ruminant stomach
contains microorganisms able to digest cellulose and carbohydrates -> disaccharides and monosaccharide, other bacteria convert these molecules into fatty acids
64
Describe the abomasum of a ruminant stomach
acts like a human stomach by secreting hydrochloric acid and protease enzymes, which digest bacterial proteins into amino acids
65
Define primary productivity / gross primary productivity, GPP
the energy fixed by photosynthesis over the course of one year (MJm-2 yr-1)
66
Define net primary productivity, NPP
the rate of production of new biomass in producers (mass per unit area per year)
67
Give an equation for net primary productivity
NPP = GPP - respiration loss
68
State 7 manipulating factors which increase energy available to consumers
```
light
temperature
water
nutrients
competition
pests
disease
```
69
Explain how light can be a manipulating factor which increases energy available to consumers
- under light banks in greenhouses (constant, optimal light intensity and duration)
- timing of sowing (max. leaf area during optimum conditions photosynthesis)
- sowing density (prevent overshadowing)
70
Explain how temperature can be a manipulating factor which increases energy available to consumers
regulated warm
71
Explain how water can be a manipulating factor which increases energy available to consumers
```
irrigation
drought-resistant variants
genetically modified (GM)
```
72
Explain how nutrients can be a manipulating factor which increases energy available to consumers
rotate crops
nitrogen-fixing crops (replenish nitrate levels in soil within rotation cycle)
application of fertilisers (if organic, increase water-holding capacity and structure)
73
State how competition can be a manipulating factor which increases energy available to consumers
herbicides
74
Explain how pests can be a manipulating factor which increases energy available to consumers
pesticides - maintain leaf area for photosynthesis
| GM pest-resistant plants (Bt gene)
75
Explain how diease can be a manipulating factor which increases energy available to consumers
fungicides
| GM disease-resistant crops
76
Define secondary productivity
the rate at which animals convert the chemical energy in the plants that they consume into their own biomass
77
State and explain 5 factors to increase secondary productivity
* antibiotics - reduce energy expenditure of immune systems by reducing infections
* zero grazing (limiting movement) - increase energy into growth
* maintenance of a constant temperature - reduce energy for thermoregulation
* selective breeding - increase productivity
* harvesting animals before adulthood - invest a greater percentage of energy into growth than adults
78
Intensive rearing of livestock produces large quantities of _ that requires _
```
waste
safe storage (prevent leaking and eutrophication
```
79
Extensive farming requires less _ than intensive farming?
chemicals
money
labour
80
Give 4 methods to conserve ecosystems
```
crops (seeds and nectar) to attract birds, bees + butterflies
maintain hedgerows (shelters and food sources)
maintain dry stone walls (habitat for moss and lichen)
creating buffer strips between intensive agriculture and natural habitats
```
81
Define succession
natural development of an ecosystem / directional change in a community of organisms over time
82
Define deflected succession
the changes resulting from human activities (land management, farming) that can prevent a climax community from forming and instead produce a stable community, plagioclimax
83
Succession: _ conditions, _ species diversity + _ -> _ conditions, _ species diversity + _
```
hostile
low
instability
less hostile
high
stability
```
84
State a typical sequence of succession
barren land -> pioneer species / primary colonisers e.g. lichen -> secondary colonisers e.g. mosses -> tertiary colonisers e.g. grasses -> scrubland e.g. shrubs + small trees -> climatic climax e.g. forest
85
State a typical sequence of deflected succession
barren land -> pioneer species / primary colonisers e.g. lichen -> secondary colonisers e.g. mosses -> tertiary colonisers e.g. grasses -> plagioclimax e.g. farmland
86
Give 3 reasons for the deforestation of deciduous woodland
non-native trees (timber and fuel)
agricultural spaces
deteriorated soil dominated by heather
87
Suggest 3 reasons why plants cannot use the ATP produced in the light-dependent stage of photosynthesis as their only source of ATP
photosynthesis only occurs in the light
the rate of production is insufficient to supply plant with concentrations of ATP required
some plant cells lack chloroplasts and would not be able to generate ATP
88
Name two useful molecules that can be produced from GP and describe one way in which a plant can use each molecule
fatty acids uses (when combined with glycerol) include: plasma membrane formation; waterproofing e.g. waxy cuticles; energy source
amino acids uses: protein formation e.g. enzyme production
89
Suggest the role of DNA and ribosomes in a chloroplast
produce photosynthetic pigments
| DNA codes for genes/proteins (e.g. enzymes used), for electron carriers, ATP synthase
90
Explain how the 3 reaction pathways, glycolysis, Calvin cycle and Krebs cycle are able to work independently of each other in the same leaf cell
```
compartmentalisation
take place in different parts / organelles:
glycolysis - cytoplasm
Calvin cycle - chloroplast
Krebs cycle - mitochondria
```
