Chapter 10 - Photosynthesis Flashcards
what is photosynthesis?
photosynthesis is the process that converts solar energy into chemical energy
what does photosynthesis do?
directly or indirectly photosynthesis nourishes almost the entire living world
what are autotrophs?
autotrophs sustain themselves without eating anything derived from other organisms
- autotrophs are producers
- almost ALL plants are photo-autotrophs
what are photo-autotrophs?
using the energy of sunlight to make organic molecules from H2O and CO2
what are heterotrophs?
heterotrophs obtain their organic material from other organisms
- heterotrophs are consumers
- Almost ALL heterotrophs including humans, are dependent on autotrophs for food and O2
Photosynthesis occurs in?
plants, algae, certain protists and some prokaryotes
chloroplasts are…?
Chloroplast are structurally similar to and likely evolved from photosynthetic bacteria
- the structural organization of these cells allows for the chemical reactions of photosynthesis
what is the major location of photosynthesis?
the leaves are the major locations of photosynthesis
what is chlorophyll?
the green colour of leaves and a plant which come from the green pigment within the chloroplast
what is the stomata?
CO2 enters and O2 exists through the leaf through microscopic pores called stomata
what is the mesophyll?
the interior tissue of the leaf
- chloroplasts are found mainly in the cells of the mesophyll (30 - 40 chloroplasts in one cell)
what are thylakoids?
chlorophyll is in membranes of thylakoids (connected sacs of chloroplast); thylakoids may be stacked in columns called grana
what is the stroma?
chloroplasts also contain stroma, a dense fluid
what are the 3 steps of photosynthesis?
- Photosynthesis oxidizes water to oxygen, respiration reduces oxygen to water
- Respiration removes high energy electrons from reduced organic substrates to form ATP and NADH
- Photosynthesis uses low energy electrons to form ATP and NADPH, which are then used to reduce CO2 to carbohydrate
Photosynthesis is what kind of process?
Photosynthesis is a REDOX and ENDERGONIC process in which H2O is split and electrons are transferred along with hydrogen ions from water to carbon dioxide, reducing it further to sugar
What are the 2 stages of Photosynthesis?
- Light dependent Reactions
2 Light Independent Reactions (Calvin Cycle)
What happens during the Light Dependent Reactions of Photosynthesis?
The light reactions convert solar energy to chemical energy
- Split H2O
- Release O2
- Reduce NADP+ to NADPH
- Generate ATP from ADP by Photophosyphorylation
- No sugar produced
Where does the light dependent reaction occur?
in the thylakoid membranes
what happens during the Light Independent Reactions (Calvin Cycle)?
The Calvin Cycle forms sugar from CO2, using ATP and NADPH
- The Calvin in cycle beings CARBON FIXATION, incorporating CO2 into organic molecules
Where does the Light Independent Reaction Occur (Calvin Cycle)?
In the Stroma
what is light?
Light is a form of electromagnetic energy, also called electromagnetic radiation
- light travels in rhythmic waves
what is a wavelength?
wavelength is the distance between crests of waves
- Wavelength determines the type of electromagnetic energy
what is the electromagnetic spectrum?
is the entire range of electromagnetic energy, or radiation
what is visible light?
visible light consists of wavelengths (including those that drive photosynthesis) that produce colours we can see
what are photons?
Light also behaves as though it consists of discrete particles called photons
what are photosynthetic pigments?
- Pigments are substances that absorb visible light
- different pigments absorb different wavelengths
- wavelengths that are not absorbed are reflected or transmitted
- leaves appear green because chlorophyll reflects and transmits green light
what is a spectrometer?
measures a pigments ability to absorb various wavelengths
- sends light through pigments and measures the fraction of light transmitted at each wavelength
what is an absorption spectrum?
is a graph plotting a pigments light absorption versus wavelength
what is the absorption spectrum of CHLOROPHYLL A
The absorption spectrum of chlorophyll a suggest that violet-blue and red light work best for photosynthesis
- chlorophyll a is the main photosynthetic pigment
what is an action spectrum?
profiles the relative effectiveness of different wavelengths of radiation in driving a process
Who is Theodor W. Engelmann?
The action spectrum was first demonstrated by Theodor W. Engelmann
- In his experiment he exposed different segments of a filamentous alga to different wavelengths
what is chlorophyll b?
accessory pigments, such as chlorophyll b, broaden the spectrum used for photosynthesis
what are carotenoids?
Accessory pigments called carotenoids, absorb excessive light that would damage chlorophyll
What happens when a pigment absorbs light?
when a pigment absorbs light, it goes from ground state to an excited state, which is unstable
what is a Photosystem?
consists of a reaction-centre complex ( a type of protein complex containing chlorophyll a) surrounded by light-harvesting complexes
what are light-harvesting complexes?
(pigment molecules bound to proteins) funnel the energy of photons to the reaction centre
What is a primary electron acceptor?
A primary electron acceptor in the reaction centre accepts an excited electron from chlorophyll a
what is the first step of light dependent reactions?
solar-powered transfer of an electron from a chlorophyll a molecule to the primary electron acceptor is the first step of the light reactions
There are two types of photosystems in the thylakoids, what are they?
- Photosystem || (PS||)
2. Photosystem | (PS|)
what is photosystem ||?
functions first (the numbers reflect order of discovery) and is the best at absorbing wavelength of 680nm - The reaction-centre chlorophyll a of PS|| is called P680
what is photosystem |?
is the best at absorbing a wavelength of 700nm
- The reaction-centre of chlorophyll a of PS| is called P700
During light reactions, how many possible routes are there for electron flow?
- Cyclic
2. Linear
what is Linear electron flow?
the primary pathway, involves both photosynthesis and produces ATP and NADPH using light energy
What is cyclic electron flow?
uses photosystem | and produces ATP and not NADPH
- cyclic electron low generates surplus ATP, satisfying the higher demand in the Calvin Cycle
Killing Weeds by inhibiting Electron Transport?
- Common herbicides bind to a core protein of PS||
- Light reactions Serve as a target of herbicides
- some herbicides produce oxygen radicals, which are toxic to human tissue
The Calvin Cycle?
Uses ATP and NADPH to convert CO2 to sugar
- The calvin cycle builds sugar from smaller molecules (anabolic reaction) by using ATP and the reducing power of electrons carried by NADPH
what is glyceraldehyde-3-phosphate (G3P)?
carbon enters the cycle as CO2 and leaves as a sugar names gyceraldehyde-3-phosphate (G3P)
For net synthesis of 1 G3P…?
For the net synthesis of 1 G3P, the cycle must take place of three times, fixing 3 CO2 molecules
The Calvin Cycle has three phases?
- Carbon fixation (Catalyzed by Rubisco)
- Reduction
- Regeneration of the CO2 acceptor (RuBP)
What are C3 Plants?
In most plants (C3 Plants), initial fixation of CO2, via rubisco, forms a three-carbon compound
What is photorespiration?
In photorespiration, rubisco adds O2 instead of CO2 in the calvin cycle
- Photorespiration consumes O2, and organic fuel and releases CO2 without, producing ATP or sugar
