2.9 Photosynthesis

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  • Created by: sofiedb
  • Created on: 20-03-18 16:28
most common plant pigment
chlorophyll - located in chloroplasts of plant cells
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beginning of photosynthesis
photons of light captured in chloroplasts at beginning of photosynthesis - used to produce organic carbon compounds
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Energy in photons
used to produce simple carbohydrates which then form more complex carbon compounds (conversion of light energy into chemical energy)
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Plants photosynthesis requirements
need light of certain wavelengths, CO2 & H2O to make all carbon compounds
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Waste product
oxygen (gas)
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Photosynthesis reaction
6CO2 + 6H2O --> C6H12O6 (glucose) + 6O2
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Photosynthesis
the reaction of CO2 & H2O using energy from light to produce carbohydrates (carbon compounds) & O2 in cells
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Chloroplasts
tiny organelles in plant or algae cells where photons (fundamental particle of light) are captured
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Visible light
wavelengths between 400 & 700 nm (violet shortest, red longest)
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Why are chloroplasts green?
Chlorophyll a & chlorophyll b, pigments that capture photons, reflect green light & absorb most of other wavelengths in visible light spectrum
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Colour of leaves
determined by colour of light from visible spectrum that is reflected
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Chlorophyll absorption & reflection
absorbs red & blue most effectively/reflects green light more than other colours
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Action spectrum
shows efficiency of photosynthesis or rate of photosynthesis achieved over various wavelengths of light from visible spectrum
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Absorption spectrum
shows which wavelength of visible light is absorbed by a particular photosynthetic pigment such as chlorophyll a or b
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Photolysis
splitting of water by light (photo - light, lysis - splitting), energy in photons is used to split water molecules
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Reaction
Generates hydrogen ions, e- & O2: 2H2O + photons --> 4e- + 4H+ + O2
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Electrons function
used to generate ATP through cyclic or non-cyclic photophosphorylation
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Functions ATP & hydrogen ions
Both ATP (produced by movement of e- through chain of carriers) & hydrogen ions are used in later stages of photosynthesis while oxygen is a waste product that diffuses out of plant
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Photosynthesis stages
light-dependent reaction, light-independent reaction
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Light-dependent reaction
requires light & occurs on the thylakoids of chloroplasts
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Light-independent reaction
has no light requirement and takes place in the stroma of chloroplasts
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Chemical reactions
require energy (ATP) - electron transport chain involved in production of ATP
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Chloroplasts
use an electron transport chain & ATPase enzyme to make ATP
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Calvin cycle
name for light-independent reactions; cycle of chemical reactions where CO2 is the starting material for the production of carbohydrates
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Limiting factor
factor that restricts the rate of a reaction when present in low amount
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Limiting factors photosynthesis
water, light intensity, CO2, temp.
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Water
limiting factor under extreme conditions (photosynthesis will stop if the plant dies due to lack of water)
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Light intensity
rate of photosynthesis increases as light increases - beyond a certain point, the chemical reactions of photosynthesis cannot speed up
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CO2
raw material in production of carbohydrates in Calvin cycle - once all active sites of enzymes involved in cyclic process are occupied with substrate, further increase in CO2 concentration will not increase rate
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Temperature
when increased beyond optimum temp, enzymes denature - at optimum temp, rate of photosynthesis is limited by light intensity & CO2 concentration
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Photosynthesis effect
changes in oxygen content of Earth's atmosphere, oceans & rock deposition can be attributed to photosynthesis
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General increase in... over years
oxygen partial pressure PO2 - introduction of single-celled algae & primitive plants
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Earliest photosynthetic organisms
prokaryotes - cyanobacteria (2700 million years ago
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2100 million years ago
eukaryotes appeared
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Building up of Earth's atmospheric oxygen
due to saturation of oceans & deposits
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Photosynthesis accounts for...
O2 in Earth's atmosphere, oceans & rock deposition over the past 2 billion years
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Chromatography
technique used to separate a mixture of substances based on movement of different substances on a piece of paper by capillary action - use of mobile phase & stationary phase for separation process
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Paper chromatography - stationary phase
Paper
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Paper chromatography - mobile phase
Solvent used to develop chromatogram
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Pigment separation
commonly through using mixture of propanone & petroleum ether
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Pigments in leaf separation
separated into chlorophylls (beta carotene & xanthophyll) using paper chromatography
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Retention factor calculation
ratio of distance moved by pigment to distance moved by solvent is constant - Rf = (distance travelled by sample)/(distance travelled by solvent)
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Thin layer chromatography - stationary phase
silica gel, aluminium oxide or cellulose
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Thin layer chromatography advantages
same principle as paper chromatography but better result - well-defined & well-separated spots are obtained
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Metabolic pathways
linked series of chemical reactions occurring within cell & controlled by enzymes
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Photosynthesis as a metabolic pathway
CO2 + H2O used to produce carbohydrates (& O2 as a by-product)
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Accessory pigments
allow some plants to take advantage of the green wavelengths of light - competitive advantage or advantage in low-light conditions (i.e. underwater)
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Rate of photosynthesis calculation
rate = change/time
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Photosynthesis change indicators
oxygen production, CO2 uptake (change in pH), change in biomass (glucose production)
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Photosynthesis change indicators (experiment no. 1)
Oxygen production (using gas syringe, inverted measuring cylinder or counting bubbles)
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Photosynthesis change indicators (experiments no. 2)
CO2 uptake (increase in pH - CO2 reacts with H2O producing bicarbonate & H+ ions which increases acidity of solution i.e. increased CO2 uptake --> increased pH --> increased rate of photosynthesis)
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Photosynthesis change indicators (experiments no. 3)
Change in biomass (glucose production) - starch levels in a plant can be identified by staining with iodine solution, which can be quantitated with a calorimeter
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Oxygen in atmosphere stage 1 (3.85 - 2.45 bill. years ago (Ga))
(practically) no O2 in atmosphere & oceans
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Oxygen in atmosphere stage 2 (2.45 - 1.85 Ga)
O2 produced & rose to values of 2-4% but absorbed in oceans & seabed rock
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Oxygen in atmosphere stage 3 (1.85 - 0.85 Ga)
O2 starts to gas out of the oceans but is absorbed by land surfaces - no significant change in atmospheric oxygen level
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Oxygen in atmosphere stage 4 & 5 (0.85 - present)
O2 sinks filled & gas accumulates in the atmosphere to current level of approx 20%
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Cyanobacteria
prokaryote - contains chlorophyll & first performed photosynthesis 2.45 bill years ago
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Banded iron formations
absorbed oxygen produced rocks with layers rich in iron oxide
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Oxygen generation allowed for...
the formation of the ozone layer (O3) - ozone shielded the Earth from damaging levels of UV radiation, which lead to evolution of a wider range of organisms
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Other cards in this set

Card 2

Front

beginning of photosynthesis

Back

photons of light captured in chloroplasts at beginning of photosynthesis - used to produce organic carbon compounds

Card 3

Front

Energy in photons

Back

Preview of the front of card 3

Card 4

Front

Plants photosynthesis requirements

Back

Preview of the front of card 4

Card 5

Front

Waste product

Back

Preview of the front of card 5
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