C20 - Photosynthesis and Environmental Management Flashcards
What’s succession?
The gradual change in community over time.
The natural development of an ecosystem.
During succession, organisms within the environment/ecosystem change its abiotic enable better adapted organisms to colonise.
What’s primary succession?
When organisms colonise a lifeless habitat.
What’s secondary succession?
When organisms re-colonise a devastated ecosystem.
What’s a climax community?
A stable community which has no more succession and contain high biodiversity.
What are pioneers?
Organisms/species which are very specialised and are the first to inhabit an area.
E.g. With sand dunes, the pioneer species is marram grass.
What are abiotic factors?
Non-living factors e.g. Salinity, temperature, pH etc.
What are biotic factors?
Living factors e.g. Disease, predators, competition etc.
What’s a xerophyte?
Species of plant adapted to survive in an arid environment, adapted to conserve water.
What’s a halophyte?
A species of plant that grows in waters of high salinity in contact with saline water.
What’s deflected succession?
When the formation of a climax community is prevented by human activities e.g. Land management (e.g. Mowing, coppicing and agriculture).
Deflected succession results in a phagioclimax community.
How are forests managed?
Deciduous woodland makes up the majority of the community but many native deciduous trees have been removed and replaced with non-native trees to meet timber and fuel demands.
Remaining woodland is managed by coppicing and rotation so different stages of succession are always present.
How do ecologists monitor biodiversity?
By sampling parts of the ecosystem.
How does sample size affect results?
Larger samples are more representative of the whole ecosystem.
This increases validity but can be limited by time, money, labour, equipment etc.
Bias should also be avoided.
What are the two methods for assessing biodiversity?
Random sampling and systematic sampling.
What’s random sampling?
Location of the sample points is decided by generating random numbers which are used as grid coordinates.
A quadrat is placed at the coordinates and the species present are observed, identifies and counted to calculate a percentage cover.
It avoids bias but can produce unrepresentative data of the ecosystem, especially is the area is large.
What are the two types of systematic sampling?
Stratified sampling and transects.
What’s a stratified sample?
When the ecosystem is divided into smaller areas based on the distribution of habitats. This is a more representative method.
What’s a transect?
Belt transect- when quadrants are placed at regular intervals along a straight line transect.
Line transect - only what touches the line is measured.
It’s usually used where a correlation may exist between an abiotic variable.
Where do light dependent reactions take place in the chloroplasts?
The grana / thylakoid membranes.
Where do light independent reactions take place in the chloroplast?
Stroma
What are grana?
Stacks of thylakoid membranes within chloroplasts.
What are thylakoids?
Flattened membrane discs stacked on top of one another to form grana.
What’s the stroma?
The fluid filled matrix containing all enzymes required for light independent photosynthesis.
How are chloroplasts adapted for their role (5)?
1) The inner membrane has transport proteins and is less permeable than the outer membrane. This allows control of substances entering the stroma.
2) Stacked thylakoids (producing grana) increases surface area.
3) Photosynthetic pigments are organised in photosystems to maximise light absorption efficiency.
4) Grana are surrounded by the stroma so products from the LDR can pass directly to enzymes catalysing LIDR (independent).
5) Chloroplasts contain their own DNA and ribosomes. They can produce some of their own photosynthetic proteins rather than importing them from the cell cytoplasm.
What energy conversions take place in chloroplasts in the light dependent stage?
Light energy to chemical energy (in photosystems).
Kinetic energy of proton flow through ATP-synthase to form ATP (chemical energy)
What is the role of photosystems do in LDR of photosynthesis?
They convert light energy into chemical energy
What do the photosystems do in LDR of photosynthesis?
Chlorophyll b molecules and accessory pigments in light-harvesting complexes absorb photons.
This energy is funnelled down to a reaction centre at the heart of a photosystems.
Electrons in 2 chlorophyll a molecules in the reaction centre are excited and rise to a higher E level. These high-E electrons are transferred to nearby molecules, known as electron acceptors.
The e- are passed through several electron carriers via redox reactions. (The Electron Transport Chain). The e- lose energy so energy is released.
The energy is used to pump proteins across the thylakoid membrane into space within the thylakoids, producing a proton gradient.
What is photophosphorylation?
The harnessing of light energy to produce ATP.
After use of the photosystems, the protons that accumulated inside the thylakoids move back across the membrane down the concentration gradient.
Chemiosmosis occurs as protons flow through the ATP synthase.
The ATP synthase converts kinetic to chemical energy and bonds ADP and Pi to form ATP.
What’s photolysis?
The splitting of water into H+ ions, electrons and oxygen by the enzyme in photosystems II.
What occurs during photolysis?
Water is split into H+ ions, electrons and oxygen.
2H2O —> 4H+ + 4e- + O2
What happens to the products of photolysis?
H+ ions are pumped into the thylakoid space, enabling ATP synthase to produce ATP via chemiosmosis.
They can also reduce NADP to NADPH in the stroma in the LIDR stage.
Electrons replace those lost by the oxidation of the chlorophyll a in photosystems II.
Oxygen is a waste product and will either diffuse out of the leaves through stomata or be used by plant cells in aerobic respiration.
What is produced at the end of the light dependent stage of photosynthesis?
ATP and NADPH is produced on the stromal side of the thylakoid membranes.
Both are necessary for the light independent stage.
What is the other name for the light independent stage of photosynthesis?
The Calvin Cycle
What is the role of CO2 in the Calvin cycle?
CO2 is fixed in the stroma of chloroplasts.
It acts as the carbon source for all photosynthetic organisms.
What is the role of ATP in the Calvin cycle?
ATP that is generated in the light dependent stage provides the energy to drive the carbon fixation reactions and the production of carbohydrates.
3 molecules of ATP are used for every turn of the Calvin cycle.
What is the role of NADPH in the Calvin cycle?
NADPH provides the reducing power (donating the hydrogen from the LDR) to enable the conversion of glycerate-3-phosphate (GP) to triode phosphate (TP).
The H from NADPH is added to GP to form TO and ATP provides the energy for this.
2 NADPH molecules are used for every turn of the cycle.
What occurs in the Calvin cycle?
1) CO2 diffuses through the stomata, plasma membrane, cytoplasm and chloroplast into the stroma.
2) The enzyme RuBisCo catalyses the reaction between RuBP (ribulose bisphosphate) and CO2.
3) The 5C RuBP molecule and the single C atom in CO2 combine to produce 2 molecules of GP (3C).
4) ATP and NADPH are used to reduce GP to another 3C molecule, TP.
5) NADP has been regenerated and returns to the light-dependent stage, where it can be reduced again by accepting further H+ ions.
6) Some TP is converted to molecules that can be used by the plant e.g. glucose.
7) The majority of TP is used to regenerate RuBP and continue the cycle. Additional ATP is needed.
How is GP (glycerate-3-phosphate) made?
By the carboxylation of RuBP (combining with CO2).
