Photosynthesis Flashcards
What is the natural source of light for plants?
sunlight
Other than natural light what source of light can you use for plants?
artificial light
Where is artificial light used and what is it used for?
Artificial light is often used in greenhouses stimulate growth
What can increasing light do?
Increase growth up to a certain saturation point where no more light can be absorbed and photosynthesis will level off
How many sources of carbon dioxide do plants have?
Plants have 2 sources of carbon dioxide one is external the other is internal
Where do plants get most of their carbon dioxide from?
the atmosphere - this is external
Where do plants get carbon dioxide from internally?
their own cellular respiration
What is sometimes used to stimulate growth in a greenhouse?
Artificial sources of carbon dioxide e.g. burning gas in a greenhouse
Why are artificial sources of carbon dioxide sometimes used?
to stimulate growth e.g. burning gas in a greenhouse
What is an example of an artificial source of carbon dioxide?
burning gas in a greenhouse
How is water absorbed from the soil and what does travel up?
By the roots of plants, the stem
What is water absorbed from the soil used for in plants?
photosynthesis
How many stages of photosynthesis are there are what are they called?
2
Light Stage and Dark Stage
Where does the light stage take place?
In the grana of the chloroplast
What does the light stage involved?
the very fast movement of electrons and is not controlled by enzymes
Is the light stage controlled by enzymes?
no
What is light absorbed by?
A range of pigment clusters found in the chloroplast (almost all colours of light are absorbed but green is normally reflected)
What colours of light are absorbed by pigment clusters?
almost all of them
What colours of light are reflected by pigment clusters?
green
Where is the range of pigment clusters found?
in the chloroplast
What is the light energy transferred to after being absorbed by pigment clusters?
the electron that has been passed to the chlorophyll
Where is the chlorophyll that the electron is passed to?
in the pigment cluster and strategically placed near an electron acceptor
What does the pigment cluster do?
Absorbs as much light energy as possible and passes it to the chlorophyll which passes it to the electron
What is the energised electron passed to after it absorbs as much light energy as possible?
The energised electron is passed to the electron acceptor which can the send it on one of two pathways
How many pathways can the energised electron be sent on?
1 of 2
draw a diagram of the light stage
with pigments in pretty colours
What happens in Electron Flow Pathway 1?
In pathway 1 the electrons pass from the first electron acceptor to a series of other electron acceptors and back again to the chlorophyll.
What happens as the electrons are passed around?
As the electrons are passed around they lose energy
What is energy lost by electrons used for?
To join a phosphate to ADP to form high energy ATP. Water is also formed in this process.
What is formed by energy lost by electrons other than high energy ATP?
Water
Write a formula for cyclic phophorylation
ADP + Energy + P -> ATP + Water
What is phosphorylation?
The addition of phosphate to ADP is called phosphorylation
What is Cyclic Phosphorylation?
The addition of phosphate to ADP while an electron travels in a cycle and returns to its original chlorophyll
What happens first in electron pathway 2?
2 high energy electrons at a time are passed from chlorophyll to the electron acceptor and then along another series of electron acceptors. In this case the electrons do not return to the original chlorophyll. They lose energy as they pass from electron acceptor to electron acceptor and this energy is used to make more ATP.
Do electrons in pathway two return to the original chlorophyll?
no
How many electrons are passed down electron pathway two from the chlorophyll to the electron acceptor at a time?
2 high energy electrons at a time
What happens after the electron is passed from electron acceptor to electron acceptor and the extra energy is to make ATP?
the 2 electrons are passed to combine with NADP+ to form NADP-. The chlorophyll molecule is now short of electrons and gains more from the splitting of water. The splitting of water using light energy is called photolysis.
what is the splitting of water using light energy called?
photolysis
What happens when the 2 electrons in pathway 2 combine with NADP+?
it forms NADP-
How does the cholorophyll molecule gain electrons when it is short of them in pathway 2?
the splitting of water
What is attracted to NADP-? What happens because of this?
The protons that were stored in the proton pool are attracted to NADP- and combine with it to form NADPH.
What is pathway 2 also known as and why?
Because the electrons start at a chlorophyll and finish at NADPH and form ATP on their way this pathway is known as Non cyclic photophosphorylation.
Draw a diagram of pathway 2
now
What are the two different sections of the light stage?
Phosphorylation Making ATP
Photolysis Splitting Water
What are the five stages of phosphorylation?
Chlorophyll traps sunlight, electrons are energised, electrons lose energy to ADP which joins with P to form ATP, Other electrons join with NADP to form NADP-, Hydrogen ions join with NADP- to form NADPH.
Show the stages of photolysis?
Water (H20) split into Hydrogen ions H+ (Used to convert NADP to NADPH), Electrons E- (Go back to chlorophyll), Oxygen O2 (By product, excreted through a leaf)
How many end products of the light stage are there?
There are three end products of the light stage
Name the three end products of the light stage?
ATP this will provide energy for the dark stage
NADPH this will provide protons + energised electrons for the dark stage
Oxygen is made when water is split
What is photosynthesis?
Plants making their own food
What are the roles of photosynthesis?
Plants use it to make food
Animals get their food from plants
It produces oxygen which is needed in respiration to produce energy
It is responsible for forming fossil fuels
It removes carbon dioxide from the air
Write a balanced equation for photosynthesis
6CO2 (carbon dioxide) + H2O (water) + light -> C6H12O6 (glucose) + 6O2 (oxygen)
What does photosynthesis require?
carbon dioxide, water, light energy, chlorophyll
What does photosynthesis produce?
Glucose and waste oxygen
What does photosynthesis convert into what?
Light energy -> chemical energy
What kind of energy is light energy converted into in photosynthesis?
glucose
What are the stages of photosynthesis?
Light is absorbed Water is split Products are produced (4 protons, 4 electrons and oxygen) Light energises electrons Glucose is formed
How is light absorbed in photosynthesis?
The light that reaches a plant is trapped by chlorophyll
Chlorophyll is found in the chloroplasts of plant cells
Therefore photosynthesis occurs in chloroplasts
The trapped light provides the energy the plants need to make glucose
How is water split in photosynthesis? con ecuación
Some of the trapped light energy is used to split water into oxygen gas (O2) protons (H+) and electrons (e-)
Summarised as 2H2O -> 4H+ and 4e- and O2
What happens to these products?
- The electrons are passed to chlorophyll
- The protons are stored in a proton pool for later use
- The oxygen may pass out of the leaf into the atmosphere or else may be used for plant respiration
How does light energise electrons?
The electrons that were passed to the chlorophyll become energised by some of the trapped light energy – this changes them into high energy electrons
How is glucose formed?
The high energy electrons along with protons from the proton pool are combined with carbon dioxide to form glucose (C6H12O6)
What may the dark stage also be referred to as? Why?
This may also be called the light independent stage as it can occur in the light but does not need to use it
Where does the dark stage take place?
In the stroma of the chloroplast
What is the dark stage controlled by? What feature does this fact cause?
enzymes
Can be affected by temperature
What happens in the dark stage?
Carbon dioxide from the air enters the chloroplast where they combine with protons + electrons to form glucose
What do the dark stage require?
energy and protons + electrons
What does the dark stage obtain energy from?
It uses energy got from breaking down ATP into ADP + P
What does the dark stage obtain hydrogen ions and electrons from?
It uses hydrogen ions and electrons got from breaking down NADPH into NADP+ + 2 electrons + H+
What is reduction?
the addition of electrons to anything
What is carbon dioxide reduced to?
Glucose
What happens at different stages of the dark stage?
- CO2 is reduced
- Oxygen atom is removed, hydrogen ions are added and electrons are added
- Glucose is formed (C6H12O6)
What are the main events in photosynthesis?
Light energy is absorbed by chlorophyll
Water is split
The electrons are passed to chlorophyll
The protons are stored in the chloroplasts
The oxygen is released
Sunlight transfers energy to electrons
The high energy electrons, stored protons (the hydrogen ions) and carbon dioxide are used to make glucose
Draw a diagram of photosynthesis
with skittles
What play a vital role in trapping and transferring energy in cellular activities?
ATP, NADP+ and NAD+
What is ADP an abbreviation of and what is it?
ADP is an abbreviation for Adenosine Diphosphate this is a molecule found in the cells of all organisms
What is ADP made of?
The base adenine, a 5 carbon sugar called ribose and 2 phosphate groups
What type of molecule is ADP?
A low energy molecule
If another phosphate is added to ADP what does it form?
ATP
What is ATP an abbreviation of?
Adenosine Triphosphate
What is also added when ADP turns into ATP? Why?
extra energy as there is an extra bond between the last two phosphate groups
What is addition of a phosphate (e.g ADP to ATP) called?
phosphorylation
What is ATP rich in and how is it stored?
energy
by carrying it around in the cell
Can ATP store energy for long? Why?
No, it breaks down, releasing energy and converting back to ADP.
How fast do most cells release energy from ATP? What is this energy used for?
10 million times every second
cellular reactions
What is NADP+?
A low energy molecule involved in photosynthesis
What can NADP+ combine with?
2 high energy electrons and a proton to form NADPH
What is NADPH?
A very high energy molecule
What is NADPH’s energy used for?
To form glucose in photosynthesis
What is NAD+ used in?
respiration
What can NAD+ combine with and what does this form?
2 high energy electrons and a proton to form NADH which is very high in energy
What are NADP+ and NAD+ used for and how do we remember this?
NADP+ is used in photosynthesis and NAD+ is used in respiration. Remember P for photosynthesis.
What do both NADH and NADPH release when they break down into NAD+ and NADP+? What is this used for?
Electrons, protons and energy used by cells
