5 Flashcards
Where does photosynthesis take place in eukaryotic plants?
Photosynthesis takes place within cell organelles called chloroplasts.
What surrounds chloroplasts?
Chloroplasts are surrounded by a double membrane.
Adaptations of a leaf
Large surface area to absorb as much sunlight as possible
Thin so short diffusion distance
Stomata that open and close
What are grana?
Grana are stacks of up to 100 disc-like structures called thylakoids where the light-dependent stage of photosynthesis takes place. Within the thylakoids
What is found within the thylakoids?
The photosynthetic pigment called chlorophyll is found within the thylakoids.
What are inter-granal lamellae?
Inter-granal lamellae are tubular extensions that join up with thylakoids in adjacent grana.
What is the stroma?
The stroma is a fluid-filled matrix where the light-independent stage of photosynthesis takes place.
What structures can be found within the stroma?
Within the stroma are a number of other structures such as starch grains.
What is the purpose of the light-dependent reaction of photosynthesis?
To add an inorganic phosphate (P,) molecule to ADP, making ATP and to split water into H* ions and OH ions through photolysis.
Define oxidation.
The process when a substance gains oxygen or loses hydrogen.
Define reduction.
The process when a substance loses oxygen or gains hydrogen.
What happens to electrons during oxidation?
Electrons are lost.
What happens to electrons during reduction?
Electrons are gained.
What is the relationship between oxidation and reduction?
They always take place together.
What occurs when a chlorophyll molecule absorbs light energy?
It boosts the energy of a pair of electrons, raising them to a higher energy level. These electrons are in an excited state
What is photoionisation?
The process by which chlorophyll becomes oxidized after losing a pair of electrons.
What role do electron carriers play in photosynthesis?
They take up the electrons that leave chlorophyll and pass them along in a series of oxidation-reduction reactions.
What is the chemiosmotic theory?
It explains the mechanism by which ATP is produced during photosynthesis.
How are protons pumped into the thylakoid chambers?
Using protein carriers in the thylakoid membrane called proton pumps.
What drives the process of pumping protons into the thylakoids?
Electrons released when water molecules are split by light during photolysis.
Fill in the blank: Oxidation can be described as the loss of _______ or gain of _______.
[electrons], [oxygen]
Fill in the blank: Reduction can be described as the gain of _______ or loss of _______.
[electrons], [oxygen]
True or False: Oxidation results in energy being taken in.
False
True or False: Reduction results in energy being given out.
False
What is photolysis?
The splitting of water molecules into H* ions and OH ions using light energy.
What is the significance of the electron transfer chain?
It allows electrons to lose energy at each stage, some of which is used to make ATP.
What is the process by which water is split using light energy in photosynthesis?
Photolysis of water
This process yields protons, electrons, and oxygen.
What increases the concentration of protons inside the thylakoid space?
Photolysis of water
This process produces protons that increase their concentration in the thylakoid space.
What maintains a concentration gradient of protons across the thylakoid membrane?
Photolysis of water
It results in high proton concentration inside and low concentration in the stroma.
How can protons cross the thylakoid membrane?
Through ATP synthase channel proteins
The membrane is impermeable to protons except through these channels.
What are the small granules formed by ATP synthase channels on the membrane surface called?
Stalked granules
These structures facilitate the passage of protons.
What process does the passage of protons through ATP synthase catalyze?
The combination of ADP with inorganic phosphate to form ATP
This is essential for energy production in photosynthesis.
What is the result of the loss of electrons from chlorophyll when light strikes it?
Chlorophyll becomes short of electrons
This necessitates the replacement of electrons to continue absorbing light energy.
What is the chemical equation representing the photolysis of water?
2H₂O → 4H⁺ + 4e⁻ + O₂
This equation shows the products of the reaction.
Fill in the blank: The protons are actively transported into the thylakoid using energy from _______.
Electrons from chlorophyll
This process involves electron transport chains.
True or False: The concentration of protons is higher in the stroma than in the thylakoid space.
False
The concentration of protons is higher in the thylakoid space.
What is the main product of the light-dependent stage of photosynthesis?
Reduced NADP
Reduced NADP serves as a potential source of chemical energy for the plant.
What happens to protons in the thylakoid space during photosynthesis?
They pass out through the ATP synthase channels and are taken up by NADP.
What occurs when NADP takes up protons?
NADP becomes reduced.
What is the role of reduced NADP in the light-independent reaction?
It carries electrons from chlorophyll molecules.
What is a by-product of the photolysis of water during photosynthesis?
Oxygen.
What happens to the oxygen produced during photosynthesis?
It is either used in respiration or diffuses out of the leaf as a waste product.
Fill in the blank: The __________ is a channel through which protons pass out of the thylakoid space.
ATP synthase.
True or False: The light-dependent stage of photosynthesis produces ATP and reduced NADP.
True.
What is the significance of reduced NADP for plants?
It is a potential source of chemical energy.
How does the process of photolysis relate to photosynthesis?
It produces oxygen as a by-product.
What are the two main products produced during the light-dependent stage of photosynthesis?
ATP and reduced NADP.
What is the primary function of the Calvin cycle?
To produce useful organic substances such as glucose
The Calvin cycle is also known as the light-independent reaction of photosynthesis.
What is the starting molecule that carbon dioxide reacts with in the Calvin cycle?
Ribulose bisphosphate (RuBP)
RuBP is a 5-carbon sugar involved in the Calvin cycle.
What enzyme catalyzes the reaction between carbon dioxide and ribulose bisphosphate?
Ribulose bisphosphate carboxylase (rubisco)
Rubisco is essential for the fixation of carbon dioxide in the Calvin cycle.
What are the products of the reaction between carbon dioxide and RuBP?
Two molecules of glycerate 3-phosphate (GP)
GP is a 3-carbon acid produced during the Calvin cycle.
What is the role of reduced NADP in the Calvin cycle?
To reduce glycerate 3-phosphate to triose phosphate (TP)
Reduced NADP is obtained from the light-dependent reactions.
What type of sugar is triose phosphate (TP)?
A 3-carbon sugar
TP is an important product in the Calvin cycle and is used to form glucose.
What energy source is used in the reduction of glycerate 3-phosphate?
ATP
ATP provides the necessary energy for the reduction process in the Calvin cycle.
Fill in the blank: Carbon dioxide enters the leaf through _______.
stomata
Stomata are small openings on the leaf surface that allow gas exchange.
What is the first step of the Calvin cycle?
Carbon dioxide diffuses into the leaf and reacts with RuBP
This step occurs in the stroma of the chloroplast.
True or False: The Calvin cycle requires light to occur.
False
The Calvin cycle is known as the light-independent reaction.
What is the main role of ribulose bisphosphate (RuBP) in the Calvin cycle?
RuBP acts as a carbon dioxide acceptor in the Calvin cycle
RuBP combines with carbon dioxide to initiate the process of carbon fixation.
What happens to NADP in the light-dependent reaction?
NADP is reduced by accepting protons and electrons
This reduction process is crucial for the light-independent reactions.
Fill in the blank: The light-independent reaction of photosynthesis takes place in the _______.
stroma of the chloroplasts
What are some organic substances that triose phosphate molecules are converted into?
- starch
- cellulose
- lipids
- glucose
- amino acids
- nucleotides
These substances are essential for plant metabolism and structure.
How do triose phosphate molecules contribute to the regeneration of ribulose bisphosphate?
Most triose phosphate molecules are used to regenerate RuBP using ATP
This regeneration is necessary for the continuation of the Calvin cycle.
What does the term ‘law of limiting factors’ refer to in the context of photosynthesis?
The rate of photosynthesis is determined by the factor that is in shortest supply
Only one factor can limit the process at any given time.
What adaptations does the chloroplast have for carrying out the light-independent reaction?
- The stroma contains all necessary enzymes
- Membrane-bound stroma maintains a high concentration of enzymes and substrates
- Stroma surrounds the grana for efficient diffusion of products
- Contains DNA and ribosomes for quick protein manufacture
These adaptations enhance the efficiency of photosynthesis.
True or False: The products of the light-dependent reaction cannot diffuse into the stroma.
False
The products can readily diffuse into the stroma from the grana.
What is the significance of the stroma’s fluid environment?
It allows for a high concentration of enzymes and substrates to be maintained
This specialized environment is crucial for facilitating the chemical reactions of photosynthesis.
Fill in the blank: The process of photosynthesis is complex and affected by multiple factors, but the rate is primarily controlled by the factor with the _______.
lowest availability
What is produced as a result of the light-dependent reactions of photosynthesis?
ATP and reduced NADP
These products are essential for the light-independent reactions.
