Unit 7-Photosynthesis Flashcards
Define autotrophs
Make their own food
Define photo-autotrophs
Use light as energy and make their own food
Ie) plants
Define photosynthesis
Pants concert CO2 and H2O to their own organic molecule and release O2 as a by product
Define heterotrophs
Can’t make their own food
What do photo-autotrophs need from their environment to make their good
Light
CO2
H2O
What does the green colour of plants come from
The chlorophyll found inside the chloroplasts
They are light absorbing pigments
Where are chloroplasts concentrated
In the cells of the mesophyll
Green tissue in the interior of the leaf
What are the tiny pores called that lets out oxygen
Stomata
What is the fluid called that is within the chloroplasts
Stroma
What are the thylakoids
Where are the chlorophyll molecules within this
Interconnected membrane sacs that inclose the thylakoid space and are stacked up in grana
Chlorophyll is built into the thylakoid membranes
What is the equation for photosynthesis
6CO2 + 6H2O -> C6H12O6 + 6O2
What type of process is photosynthesis
A redox process
Explain light dependent reactions
Include the steps that convert light energy into chemical energy and release O2
Water is split providing a source of electrons and giving off O2 as a byproduct. Light energy is absorbed by the chlorophylls
And generates ATP from ADP
What does the chlorophyll do in the light dependent reaction
Used the light to drive the transfer of electrons and H+ from water to the electron acceptor NADP+ and reduces it to NADPH
Where does light dependent reactions take place
In the thylakoid membranes
Does light dependent reactions produce sugar
NO
Explain the Calvin cycle
A series of cycle reactions that assembles sugar molecules by using CO2 and the products from the first step
What is carbon fixation in the Calvin cycle
The incorporation of carbon from CO2 into organic compounds
Where does the Calvin cycle take place
In the stroma of the chloroplasts
After carbon fixation what occurs
Enzymes make sugars by further reducing the carbon compounds
What is used in the Calvin cycle to reduce carbon
The NADPH from the light dependent reaction
For chloroplasts to produce sugar from CO2 in the dark they would need to be supplied with what
ATP and NADPH
What are pigments how do they work
Light absorbing molecules
Only absorb some wavelengths and the others are either reflected off the chloroplast or transmitted through the chloroplast
Why do plants show green
Because different pigments can absorb different wavelengths and in plants Chlorophyll a participates which plays in a role with what type of light is absorbed or reflected
Define a photon
A packet of energy
Does shorter wavelengths mean more or less energy
More energy
What are the three phases of the Calvin cycle
Fixation
Reduction
Regeneration
What happened when a pigment molecule absorbs a photon of light
One of the pigments electrons jumps to an energy level further from the nucleus this makes the electron have more potential energy and is now in an excited state
What happens when the electron falls back to the ground state
It emits its energy as heat and light
Define a photosystem
Consists of a number of light harvesting complexes surrounding a reaction centre complex
What are the two types of complexes
Light harvesting complex - Contains various pigment molecules - Acts as a light gathering antenna Reaction centre complex - contains the pair of special chlorophyll a molecules and the primary electron acceptor
In photosynthesis __ is oxidized and ___ is reduced
Water
Carbon dioxide
What are produced by reactions that take place in the thylakoids and consumed by reactions in the stroma
ATP
NADPH
When light strikes chlorophyll molecules in the reaction centre complex they lose electrons which are ultimately replaced by
Splitting water
The reactions of the Calvin cycle are not directly dependent on light but they usually do not occur at night why?
The Calvin cycle depends on products of the light dependent reactions
How many turns of the Calvin cycle are required to produce one molecule of glucose
6
What does not occur during the Calvin cycle
Release of oxygen
Why is it difficult for most plants to carry out photosynthesis in very hot dry environments such as deserts
The closing of stromata keeps CO2 from entering and O2 from leaving the plant
In the light dependent reaction electrons removed from __ pass from ___ to ____ to ____
H2O
Photosystem II
Photosystem I
NADP+
Where do photo excited electrons go
From the photo system I they are passed through a short electron transport chain to NADP+ reducing it to NADPH
What powers ATP synthesis in the light dependent reactions
Chemiosmosis
What is the chemiosmotic production of ATP called in photosynthesis
Photo phosphorylation
How des photo and oxidative phosphorylation compare
In cellular respiration the high energy electrons passed down the chain come from the oxidative molecules and in photo light energy is used to drive electrons that originally came from water
What is regenerated with each turn of the Calvin cycle
A five carbon sugar called ribulose bisphosphate
What happens in the carbon fixation step of the Calvin cycle
The enzyme rubisco attaches CO2 to the 5 carbon sugar
What happens in the reduction reaction of the Calvin cycle
NADPH reduced the organic acid by using ATP to make a sugar molecule but to complete it it needs three molecules of carbon but it is only give one carbon per cycle
To synthesize one glucose molecule the Calvin cycle uses __ CO2 and ___ ATP and __ NADPH.
6
18
12
