Chapter 5.2 Flashcards
What is much of the glucose produced by plants converted to?
Cellulose and other structural tissues. It may also be converted to carbohydrates
How much dry weight do products of photosynthesis account for in plants?
95%
What are the starting reactants of photosynthesis?
Carbon dioxide and water
What are the end products of photosynthesis?
Glucose and oxygen
What are the 2 reactions that make up photosynthesis called?
Light-dependant reactions and light-independent reactions
What happens in light dependant reactions?
Solar energy is trapped and used to generate high energy compounds called ATP and NADPH
What does NADPH have a lot of?
A large amount of reducing power
What happens in light independent reactions?
The energy of ATP and the Reducing power of NADPH are used to reduce carbon dioxide to make glucose
What do pigments within the Thylakoid do during light dependant reactions?
Absorb light energy
Where are pigments found?
In the Thylakoid
What is a Photosynthetic pigment?
A compound that traps light energy and passes it on to other chemicals which use the energy to synthesize high energy compounds
What is the main photosynthetic pigment in plants?
Chlorophyll
Why does chlorophyll appear green?
Because it absorbs other colors and reflects green
What is an absorbance spectrum?
A graph that shows the relative amounts of light of different colors that a compound absorbs
What does an action spectrum show?
The relative effectiveness of different wavelengths of light for promoting photosynthesis
How does the Absorbance spectrum and the action spectrum show the link between oxygen production with wavelengths?
They show that the production of oxygen is increased at certain wavelengths
What are photosystems?
How chlorophyll and other pigments are arranged in the thylakoid membrane in clusters
What are the 2 photosystems found in the chloroplasts of plants?
Photosystem I (PSI) Photosystem II (PSII)
What are photosystems made of?
Pigment molecules that include one dozen or more chlorophyll molecules. Also, a molecule that accepts electrons
Where do photosystems pass absorbed energy to?
The reaction center
What is the reaction center?
A specialized electron accepting chlorophyll found in the photosystems
What happens when the reaction center has received the energy passed to it?
A electron becomes excited and raised to a higher level and passed on to an electron accepting molecules
What happens when the electron acceptor receives the electron?
It become reduced so it has high energy
What happens reaction system to photosystem II when the electron leaves?
IT is missing an electron so it must be replaced before the photosystem II can absorb more energy
Where does the photosystem gain an electron to replace to old one?
The water molecule that is split in a series of reactions. This is where the oxygen is produced
What happens to the electron after it get to the electron acceptor?
It is carried along electron carrying molecules
What is the electron transport system?
Molecules that transport the electron from the electron acceptor
What happens to the electron with each transfer on the electron transfer system?
It releases a small amount of energy
What is the energy that is released by the electron on the electron transport system used for?
It is used to push hydrogen ions from the stoma, across the thylakoid membrane into the thylakoid space
Where is the energy that an electron releases during the electron transport system stored?
A hydrogen ion concentration gradient across the thylakoid membrane
What happens in photosystem I as the other events are taking place?
- Light energy is absorbed and the energy is transferred to the reaction center
- The electron is passed to an electron acceptor
- The lost electron is replaced by the electron that has travelled through the energy transport system of photosystem II
- The electron lost is used to power light independent reactions
Where does the electron that is replaced in photosystem II come from?
From the water molecule that is split in a series of reactions
Where does the electron that is replaced in photosystem I come from?
The electron that was lost from photosystem II and passed down the electron transport system
What are the steps to the path of light dependant reactions?
- Light energy is absorbed in photosystem II and passed down to the reaction center
- The reaction center releases an electron to the electron acceptor
- The electron acceptor moves it into the electron transport system where it goes to photosystem I
What is the energy from the hydrogen ions used for?
To produce ATP and ADP
What happens when hydrogen ions are forced from the stoma to the thylakoid space?
They cannot diffuse across the membrane back because they are charged
What provides a pathway for hydrogen ions to move down their concentration gradient?
A special structure called ATP synthase embedded in the thylakoid membrane
What is the ATP synthase linked to?
A mechanism that bonds free phosphate an ADP molecule to form ATP
How does the ATP synthase bond ADP to ATP?
As the hydrogen ions move through it the energy is used to bond phosphate groups to ADP
What is chemiosmosis?
The linking of the movement of hydrogen ions to the production of ATP
What is the product of hydrogen burning?
Pure, clean water
What happens when there is a sufficient amount of NADPH and ATP in the stroma of chloroplasts?
The energy can be used to synthesize glucose in the presence or absence of light
What is the Calvin-Benson Cycle?
The series of reactions by which carbohydrates are synthesized
What are the stages in the Calvin Benson Cycle?
- Fixing Carbon dioxide
- Reduction
- Replacing RuBp
What happens in the first stage of the Calvin Benson cycle?
Carbon Dioxide gets fixed by carbon dioxide being chemically bonded to a preexisting molecule in the stroma and this is called ribulose biphosphate (RuBP). This is unstable and quickly breaks down into three identical carbon compounds
What is carbon dioxide fixation?
When the carbon atom in carbon dixoide is bonded to a molecule in the stroma which produces RuBP
What are plants the demonstrate carbon fixing called?
C3 plants
How can the fixing of carbon dioxide in the Stroma be summarized?
CO2 + RuBP → unstable C6 → 2 C3
What happens in the second stage of the Calvin Benson cycle?
Reduction. The new 3 carbon compounds are low energy and need to be reduced. To reduce them they are activated by ATP and the reduced by NADPH. The result is two molecules of PGAL. Some PGAL leave the cycle to make glucose and others move on to the next stage of the cycle
What happens in the third stage of the Calvin Benson Cycle?
The reduced PGAL molecules are used to make RuBP. Energy from ATP is used to break the chemical bonds from PGAL into RuBP
How many times must the Calvin Benson Cycle be completed?
6 times in order to synthesize one molecule of glucose
What is done with the 12 PGAL produced in the Calvin Benson cycle?
10 are used to regenerate RuBP and 2 are used to make glucose
