Photosynthesis as an Energy Transfer Process (Cambridge (CIE) A Level Biology): Flashcards
Exam code: 9700
1/590Still learning
Know0
- FrontChloroplasts
Define chloroplast.
Was this flashcard helpful?
Cards in this collection (59)
Define chloroplast.
A chloroplast is the organelle in plant and algal cells that is the site of photosynthesis.
How is the structure of the thylakoid membranes related to their function?
They provide a large surface area for the attachment of chlorophyll, electron carriers and enzymes.
This maximises light absorption for the light-dependent stage.
What is the function of the stroma in a chloroplast?
The stroma is the fluid-filled matrix that is the site of the light-independent stage (Calvin cycle).
It contains the enzymes needed to fix carbon dioxide.
Define granum.
A granum is a stack of thylakoids within the chloroplast, connected to other grana by intergranal lamellae.
A chloroplast is surrounded by a double membrane called the .
A chloroplast is surrounded by a double membrane called the envelope.
Why do chloroplasts contain DNA and 70S ribosomes?
So they can synthesise some of their own proteins, including enzymes used in photosynthesis.
What is the function of the starch grains found in the stroma?
They store the carbohydrate products of photosynthesis as an insoluble energy reserve.
What are the two stages of photosynthesis and where does each occur?
The light-dependent stage occurs in the thylakoids.
The light-independent stage (Calvin cycle) occurs in the stroma.
Which two products of the light-dependent stage are used in the light-independent stage?
ATP and reduced NADP.
What are ATP and reduced NADP used for in the Calvin cycle?
They provide the energy and reducing power needed to convert carbon dioxide into complex organic molecules.
Energy transferred as ATP and from the light-dependent stage is used in the Calvin cycle.
Energy transferred as ATP and reduced NADP from the light-dependent stage is used in the Calvin cycle.
Why is the Calvin cycle described as light-independent?
It does not use light directly.
However, it depends on the ATP and reduced NADP made in the light-dependent stage.
True or False?
The light-independent stage produces complex organic molecules such as carbohydrates.
True.
The Calvin cycle uses ATP and reduced NADP to build complex organic molecules from carbon dioxide.
Define thylakoid.
A thylakoid is a flattened, membrane-bound sac inside the chloroplast, made up of a thylakoid membrane and a thylakoid space.
Thylakoids are arranged in stacks called .
Thylakoids are arranged in stacks called grana.
Which part of the chloroplast is the site of the light-dependent stage?
The thylakoids (thylakoid membranes and thylakoid spaces), which occur in stacks called grana.
Which part of the chloroplast is the site of the light-independent stage?
The stroma.
What are the two components of a thylakoid?
The thylakoid membrane and the thylakoid space (the fluid-filled interior).
Name the four chloroplast pigments.
Chlorophyll a, chlorophyll b, carotene and xanthophyll.
What is the role of chloroplast pigments in the thylakoids?
They absorb light of different wavelengths and transfer the energy to reaction centres for the light-dependent stage.
Which pigment is the primary pigment, and what are the others called?
Chlorophyll a is the primary pigment.
Chlorophyll b, carotene and xanthophyll are accessory pigments.
Define accessory pigment.
An accessory pigment absorbs wavelengths of light that chlorophyll a cannot, then passes the energy on to chlorophyll a.
The primary photosynthetic pigment, which absorbs mainly red and blue light, is .
The primary photosynthetic pigment, which absorbs mainly red and blue light, is chlorophyll a.
To which group of pigments do carotene and xanthophyll belong?
The carotenoids.
They absorb light and also protect chlorophyll from damage by excess light.
Why is it an advantage for a plant to have several different pigments?
Each pigment absorbs a different range of wavelengths, so a wider range of light can be used for photosynthesis.
Define absorption spectrum.
An absorption spectrum is a graph showing the wavelengths of light absorbed by a photosynthetic pigment.
Define action spectrum.
An action spectrum is a graph showing the rate of photosynthesis at different wavelengths of light.
What does a close correlation between the absorption and action spectra suggest?
That the pigments absorbing that light are responsible for driving photosynthesis at those wavelengths.
At which wavelengths are light absorption and the rate of photosynthesis highest?
In the blue (~400–450 nm) and red (~650–700 nm) regions.
Both are lowest in the green region.
The rate of photosynthesis is lowest in light because it is mostly reflected by chlorophyll.
The rate of photosynthesis is lowest in green light because it is mostly reflected by chlorophyll.
Why do the absorption spectrum and action spectrum have a similar shape?
The more light a pigment absorbs at a given wavelength, the more energy is available, so the rate of photosynthesis is higher.
Define chromatography (in the context of chloroplast pigments).
Chromatography is a technique used to separate a mixture of chloroplast pigments so they can be identified.
Why do different pigments travel different distances during chromatography?
They have different solubilities in the solvent.
More soluble pigments are carried further up the paper.
What is an Rf value and how is it calculated?
The Rf value is a ratio used to identify a pigment.
Rf = distance moved by pigment ÷ distance moved by solvent front.
How is an Rf value used to identify a pigment?
The calculated Rf value is compared with known (database) Rf values measured under the same conditions.
The distance moved by a pigment divided by the distance moved by the solvent front gives its .
The distance moved by a pigment divided by the distance moved by the solvent front gives its Rf value.
Why is an Rf value always less than 1?
A pigment can never travel further than the solvent front, so its distance is always the smaller value.
Define photophosphorylation.
Photophosphorylation is the synthesis of ATP using light energy during the light-dependent stage of photosynthesis.
What are the two types of photophosphorylation, and when do they occur?
Cyclic and non-cyclic photophosphorylation.
Both occur during the light-dependent stage.
Which photosystem is involved in cyclic photophosphorylation?
Only photosystem I (PSI).
Outline what happens in cyclic photophosphorylation.
Chlorophyll in PSI is photoactivated, releasing electrons.
The electrons pass along carriers and return to PSI, and ATP is synthesised.
True or False?
Cyclic photophosphorylation produces both ATP and reduced NADP.
False.
Cyclic photophosphorylation produces only ATP — no reduced NADP is made and no water is split.
Which photosystems are involved in non-cyclic photophosphorylation?
Both photosystem I (PSI) and photosystem II (PSII).
In non-cyclic photophosphorylation, what catalyses the photolysis of water?
The oxygen-evolving complex.
Define photolysis of water.
Photolysis is the splitting of water using light energy, producing protons (H^+^), electrons and oxygen.
What are the products of non-cyclic photophosphorylation?
ATP and reduced NADP.
Oxygen is also released as a by-product of photolysis.
During photophosphorylation, how do energetic electrons release their energy?
As they pass through the electron transport chain in the thylakoid membrane.
How is the energy released by electrons used to set up a proton gradient?
It is used to transfer protons across the thylakoid membrane, into the thylakoid space.
How is ATP synthesised during photophosphorylation?
Protons return to the stroma from the thylakoid space by facilitated diffusion through ATP synthase.
This provides the energy to synthesise ATP.
What is the role of the enzyme rubisco in the Calvin cycle?
Rubisco catalyses the fixation of carbon dioxide by combining it with RuBP.
What is ribulose bisphosphate (RuBP)?
RuBP is the 5C compound that carbon dioxide combines with at the start of the Calvin cycle.
What is formed when carbon dioxide combines with RuBP?
Two molecules of glycerate 3-phosphate (GP), a 3C compound.
How is glycerate 3-phosphate (GP) converted to triose phosphate (TP)?
GP is reduced to TP in reactions that use reduced NADP and ATP.
How is RuBP regenerated in the Calvin cycle?
RuBP is regenerated from triose phosphate (TP) in reactions that use ATP.
Carbon dioxide combines with RuBP to form two molecules of .
Carbon dioxide combines with RuBP to form two molecules of glycerate 3-phosphate (GP).
How many carbon atoms are in RuBP, GP and TP?
RuBP = 5C
GP = 3C
TP = 3C
Which molecules can triose phosphate (TP) be used to produce?
Carbohydrates, lipids and amino acids.
Which molecules can glycerate 3-phosphate (GP) be used to produce?
Some amino acids.
In the Calvin cycle, triose phosphate is used to make carbohydrates, lipids and .
In the Calvin cycle, triose phosphate is used to make carbohydrates, lipids and amino acids.
Sign up to unlock flashcards
or