C1.3 photosynthesis Flashcards
(97 cards)
1
Q
What are photoautotrophs?
A
organisms that use light to produce their own food
2
Q
What are heterotrophs?
A
are organisms that cannot produce their own food
3
Q
What are autotrophs?
A
organisms that can produce their own food. Not all autotrophs are photoautotrophs, some are chemoautotrophs, which use chemical reactions to obtain their energy
4
Q
What is photosynthesis?
A
is the process where light energy is converted into chemical energy, allowing organisms to make glucose from carbon dioxide and water. Oxygen is released as a byproduct. This happens in the chloroplasts
5
Q
What is the equation for photosynthesis?
A
Carbon dioxide + water ->(light) glucose + oxygen
(carbon dioxide - glucose) become reduced
(water - oxygen) becomes oxidized
6
Q
What part of a leaf contains the green pigment responsible for photosynthesis?
A
chloroplasts contain the green pigment chlorophyll and are the site of photosynthesis in the leaf cells
7
Q
What is the dominant photosynthetic pigment in most plants?
A
chlorophyll is the dominant pigment, with **chlorophyll a and b **being the most common types
8
Q
Why do plants appear green?
A
Plants appear green because chlorophyll reflects green light while absorbing other wavelengths for photosynthesis
9
Q
What are **carotenoids **and what do they include?
A
Carotenoids are accessory pigments in plants that help absorb light. They usually include carotenes (orange pigments) and xanthophylls (yellow pigments)
10
Q
What is chromatography used for in plant pigment studies?
A
It is used to seperate and identify the different pigments present in a plant
11
Q
How does chromotagrophy work?
A
- Apply Pigment: A small spot of pigment (like crushed leaf extract) is placed near the bottom of a strip of chromatography paper.
- Dip in Solvent: The bottom of the paper is placed in a solvent, but the pigment spot stays above the solvent level.
- Capillary Action: The solvent travels up the paper by capillary action, carrying the pigments with it.
- Separation: Different pigments move at different speeds based on their size, solubility, and interaction with the paper. More soluble pigments move further.
- Result: A pattern of colored bands appears — each representing a different pigment.
12
Q
How to calculate Rf value for each pigment?
A
distance moved by substance / distance moved by solvent
13
Q
What does chromatography help scientists determine in plant cells?
A
Chromatography helps scientists determine the pigments present in chloroplasts
14
Q
What does a high Rf value indicate about a pigment in chromatography?
A
A high Rf value indicated that the pigment is more soluble in the solvent and has a lower affinity for the chromatography paper
15
Q
What types of pigments typically have high Rf values?
A
smaller pigments that are more soluble in the solvent typically have high Rf values
16
Q
What part of the electromagnetic spectrum do plants use for photosynthesis?
A
Plants use the visible portion of the electromagnetic spectrum for photosynthesis
17
Q
How can you see the different colors that make up sunlight?
A
You can see the different colors of sunlight by passing sunlight through a prism
18
Q
A
18
Q
What happens when light strikes a substance?
A
the substance can either:
- absorb the light (energy is absorbed and may be used)
- reflect the light (energy is not absorbed and you see that color)
19
Q
What determines a photoautotroph’s ability to absorb light energy?
A
The pigments present on the membranes of the chloroplasts determine a photoautotroph’s ability to absorb light energy
20
Q
What is the absorption spectrum?
A
this is a graph showing how much light is absorbed by a pigment at different wavelengths
21
Q
How can the rate of photosynthesis be measured?
A
The rate of photosynthesis can be calculated either the rate of oxygen production or the rate of carbon dioxide consumption.
22
Q
Characteristics of absorption spectrum
A
- varies depending on type of photosynthetic pigment present
- respresents the amount of light energy being absorbed by the photosynthetic pigment
- for the plant, this spectrum represents the light absorbed by all the pigments present
- chlorophyll a and b have a high absorption of light energy in the violet-blue and red light wavelengths
- Pigments like carotenoids absorb light energy at different wavelengths compared to chlorophyll a and b
- other pigments are not as efficient at absorbing light energy as chlorophylls a and b
23
Q
Characteristics of action spectrum
A
- varies depending on type of photosynthetic pigment present
- represents the rate of the photosynthetic process being carried out by the pigment
- for the plant, this spectrum represents the rate of photosynthesis as a result of all the pigments present
- chlorophyll a and b create a relatively high efficiency rrate of photosynthesis
- pigments like carotenoids allow photosynthesis at different wavelengths
- other pigments are not as effective at achieving high rates of photosynthesis as chlorophylls a and b
24
What happens when a pigment absorbs light?
the energy is used to raise an electron in the pigment to a higher energy level, a process called **excitation of electrons**
25
What is needed to excite (give energy) an electron to a higher energy level?
A specific amount of energy or specific photons of light
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Why do different pigments absorb different wavelengths of light?
Because each pigment requires a different wavelength to excite its electrons
27
What is the result of electrons being excited to a higher energy level?
The energy can be used to make chemical bonds, transforming light energy into chemical energy
28
How does the rate of cell respiration in plants change over time?
the rate of cell respiration in plants is fairly consistent throughout the day and night and remains at a relatively low level, since plants require less ATP than animals.
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How does the rate of photosynthesis in plants vary?
The rate of photosynthesis is highly variable and depends on environmental factors such as light intensity and air temperature. It is typically higher during the day, especially on warm, sunny days, and may drop to zero at night
30
What happens to gas exchange in plants at night?
At night, photosynthesis stops, so plants may release carbon dioxide and take in oxygen to support their consistent but low rate of cellular respiration
31
What is a photosynthometer and how is it used?
a photsynthometer is an apparatus used to measure oxygen production by an aquatic plant. By collecting and measuring the volume of oxygen produced, it helps determine the rate of photosynthesis and how it is affected by environmental factors like light intensity or temperature
32
What is the law of limiting factors in photosynthesis?
It states that a process dependent on multiple factors will be limited by the factor in the shortest supply or least favorable condition
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What are some common limiting factors of photosynthesis?
Water availability, sunlight (light intensity), temperature, carbon dioxide concentration, and the presence of chloroplasts and chlorophyll
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How does increasing light intensity affect the rate of photosynthesis?
Photosynthesis rate increases with light intensity until a point where enzymes reach their maximum rate, after which it plateaus
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How does temperature affect the rate of photosynthesis?
The rate increases with temperature due to more molecular collisions, but drops sharply if enzymes denature at high temperatures
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How does increasing carbon dioxide concentration affect photosynthesis?
The rate of photosynthesis increases until it levels off, unless other factors like light or temperature are also increased.
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How does increasing carbon dioxide affect plant productivity?
Increasing carbon dioxide levels generally increases plant productivity, as CO2 is a limiting factor in photosynthesis. However, weeds tend to show greater growth increases than crops and trees
38
What did Peter Wayne's study on ragweed show about CO2 levels?
The study showed that doubling CO2 levels increased ragweed pollen production by 61%, which may worsen allergy symptoms in sensitive individuals
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What are FACE experiments and why are they important?
(Free-air Carbon dixioxide enrichment) experiments study the effects of rising CO2 on plants in natural or agricultural ecosystems, giving more realistic insights than controlled greenhouse studies.
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What are the two stages of photosynthesis?
Photosynthesis consists of light-dependent reactions and light-independent reactions (also called **calvin cycle**). Light-dependent reactions capture light energy, while the calvin cycle uses that energy to synthesize carbohydrates
41
Where do photosystems occur, and what is their role?
Photosystems are located in the thylakoids of chloroplasts and are essential to the light-dependent reactions of photosynthesis. They capture and transfer light energy
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What is the reaction centre of a photosystem?
The reaction centre is the core of a photosystem where special chlorophyll molecules absorb energy and transfer electrons to a primary electron acceptor
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How does light energy reach the reaction centre in a photosystem?
Pigments in the light-receiving complexes absorb photons and transfer the energy from molecule to molecule until it reaches the reaction centre
44
What is a photosystem?
is a **protein-pigment complex** in the thylakoid membrane of chloroplasts that plays a crucial role in the light-dependent reactions of photosynthesis. It captures lights energy and converts in into chemical energy by exciting electrons, which are then transferred through ETC to produce ATP and NADPH
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What is the reaction centre?
The reaction centre is the core of a photosystem where a pair of special chlorophyll a molecules transfer excitted electrons to a primary electron acceptor
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What surrounds the reaction centre in a photosystem?
The reaction centre is surrounded by pigment molecules and proteins called the light-harvesting complex, which pass absorbed light energy to the centre.
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What happens when pigment molecules in the photosystem absorb light?
the energy from absorbed light is transferred from pigment to pigment until it reaches the reaction centre, where it excites an electron
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What is the first step in the light-dependent reactions of photosynthesis?
A photon is absorbed by pigments in photosystem II, exciting an electron in the P680 reaction centre chlorophyll a to a higher energy level
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What happens to the excite electron in photosystem II?
It is captured by the primary electron acceptor and begins its journey down the electron transport chain
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What is photolysis and where does it occur in the light-dependent reactions?
Photolysis is the splitting of water by light energy, producing electrons, H+ ions, and oxygen. It occurs in photosystem II to replace lost electrons
51
What is the role of ETC in photosystem II?
As electrons move down the chain, they lose energy which powers proton pumps, creating a gradient used to make ATP via chemiosmosis
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How is ATP produced during the light-dependent reactions?
The energy lost from electrons powers proton pumps. Protons diffuse through ATP synthase, driving the phosphorylation of ADP to ATP (chemiosmosis)
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What triggers photosystem I (P700) to excite another electron?
A second photon of light is absorbed, and the energy excites another electron in the P700 chlorophyll a molecule to a higher energy level
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What happens to the excited electron in photosystem I?
It is passed down a short electron transport chain and eventually transferred to NADP+ by the enzyme NADP reductase
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What is the final product of electron transport in photosystem 1?
NADP+ combines with an electron and a hydrogen ion to form NADPH
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Why do photosystems contain multiple types of accessory pigments?
Multiple accessory pigments allow absorption of a broader range of light wavelengths, ensuring that the ligh-dependent reactions of photosynthesis can proceed efficiently
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What would happen if a photosystem only had one pigment?
Photosynthesis would not proceed effectively beyond the light-dependent reactions because a single pigment cannot capture the full spectrum of light
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How do accessory pigments contribute to thee action spectrum of photosynthesis?
they each absorb different wave lengths of light, working together to increase the overall rate of photosynthesis
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What is the relationship between the number of accessory pigments and the rate of photosynthesis?
The greater the number of accessory pigments, the higher the potential rate of photosynthesis
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What role does chlorophyll a play in photosystems?
is a **primary pigment** and is essential for transferring absorbed energy to the reaction centre
61
What are the final products of the light-dependent reactions in photosynthesis?
Reduced NADP (NADPH) and ATP
62
What is the function of ATP and NADPH produced in the light-dependent reactions?
They supply the chemical energy and reducing power needed for the calvin cycle (light-independent reactions)
63
Where does the oxygen released by photosynthesizing plants come from?
It comes from the splitting of water (photolysis) during the light-dependent reactions
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Why is oxygen released as a waste product in photosynthesis?
Because only the protons and electron from water are used in the process, oxygen is left over and released
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How did photosynthetic oxygen affect Earth's atmosphere and geology?
The release of waste oxygen from photosynthesis significantly altered Earth's atmosphere and influenced geological processes.
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What is chemiosmosis?
is the process that enables phosphorylation of ADP to form ATP, powered by a flow of protons across a membrane
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What is the source of energy for chemiosmosis in photosynthesis?
The energy comes from light, which drives electron movement and proton pumping across the thylakoid membrane
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What is the production of ATP using light energy in photosynthesis called?
Photophosphorylation
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What is phosphorylation?
is the process of adding a phosphate group to a molecule. most commonly ADP, forming ATP
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Characteristics of respiration chemiosmosis
- involves an electron transport chain embedded in the membranes of the cristae
- energy is released when electrons are exchanged from one carrier to another
- released energy is used to pump hydrogen ions actively into the intermembrane space, creating a proton gradient
- hydrogen ions come from the matrix
- hydrogen ions diffuse back into the matrix through the channels of ATP synthase
- ATP synthase catalyses the photophosphorylation of ADP to form ATP
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Characterisitics of photosynthesis chemiosmosis
- involves an ETC embedded in the membranes of the thylakoids
- energy is released when electrons are exchanged from one carrier to another
- released energy is used to pump hydrogen ions actively into the thylakoid space, creating a proton gradient
- hydrogen ions come from the stroma
- hydrogen ions diffuse back into the stroma through the channels of ATP synthase
- ATP synthase catalyses the photophosphorylation of ADP to form ATP
73
What role does the cytochrome complex play in ATP production?
pumps H ions into the thylakoid space, creating a proton gradient that drives chemiosmosis and ATP synthase
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What is non-cyclic photophosphorylation?
electrons move through the electron transport chain and are eventually used to reduce NADP+ to NADPH, while producting ATP
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What is cyclic photophosphorylation?
electrons from photosystem 1 are recycled back into the ETC instead of reducing NADP+. this allows ATP to be produced without forming NADPH
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What is the difference between photosystem I and II?
II is first in chain, whereas I is second
II electron source is water, wheres in I it is electrons from II
product in II is ATP, and in I it is NADPH
II splits water, whereas I does not
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What does the light-dependent reaction capture?
It captures light energy, which is then needed for the synthesis of carbohydrates in the calvin cycle. These reactions take place in thylakoids of the chloroplasts, whereas calvin cycle takes place in the stroma
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Is the calvin cycle dependent on light?
Directly it is **not **dependent on light, but indirectly it is dependent because it requires the energy carriers ATP and reduced NADP (NADPH), which are produced by the light-dependent reactions. These 2 carriers provide the energy and reducing power for the calvin cycle to occur
79
What are the main steps in the calvin cycle?
1. **Carbon fixation**: C02 binds to RuBP with help from Rubisco, forming an unstable 6-carbon compound (initially there is a 5-carbon compound)
2. This compound splits into two 3-carbon molecules called glycerate 3 - phosphate (GP)
3. GP is converted to triose phosphate (TP) using ATP and NADPH (a reduction reaction)
4. Some TP leaves the cycle ro form sugars, most regenerates RuBP
5. ATP is used ro regenerate RuBP, allowing the cycle to continue
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What is RuBP and what is its role in the calvin cycle?
this is a 5-carbon compound that binds with CO2 during **carbon fixation**. It's regenerated at the end of the calvin cycle using ATP
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What is Rubisco?
This enzyme catalyses the fixation of carbon dioxide by attaching it to RuBP, starting the calvin cycle
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What is carbon fixation in photosynthesis?
is the process of taking **inorganic carbon dioxide** from the atmosphere and converting it into **organic** carbon compounds (like sugars) that can be used by living organisms
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What types of carbon compounds can be made from calvin cycle intermediates?
Glucose, sucrose, cellulose, starch, fatty acids, glycerol, and amino acids can be synthesized from calvin cycle intermediates
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How is glucose phosphate used in plants?
It is the starting point for the production of cellulose and starch
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What is intermediate is used to produce fatty acids and glycerol?
Glycerate 3-phosphate (GP)
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How are amino acids formed from Calvin cycle intermediates?
By adding nitrogen to the hydrocarbon backbone of GP
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Where does all the carbon in plant tissues ultimately come from?
from carbon fixed in the calvin cycle
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What are the two main stages of photosynthesis?
Photosynthesis includes **light-dependent and light-independent reactions**
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What are the products of the light-dependent reactions and why are they important?
The light-dependent reactions produce ATP and reduced NADP (NADPH), which provide the energy and electrons needed for the light-independent reactions
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What happens if carbon dioxide is not available during photosynthesis?
If carbon dioxide is absent, the photosystems in the light-dependent reactions cannot function properly, halting the entire process of photosynthesis
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Characterisitics of light-dependent reactions
- occur in thylakoids
- use light energy to form ATP and reduced NADP
- Split water in photolysis to provide replacement electrons and H+, releasing oxygen to the atmosphere as waste
- include two ETC's and photosystems I and II
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characteristics of Light-independent reactions
- occur in the stroma
- use ATP and reduced NADP to form triose phosphate
- return ADP, inorganic phosphate and NADP to the light-dependent reaction
- involve the calvin cycle
