10: Photosynthesis Flashcards
Module 2, Lesson 4
Almost all life on Earth ultimately depends on…
Energy from the Sun
A process that produces oxygen is termed…
Oxygenic
List three groups of organisms that can perform photosynthesis.
- Cyanobacteria
- 7 types of algae
- Most plants
During photosynthesis…
Carbon dioxide, water, and sunlight are converted into glucose, water, and molecular oxygen.
The process of photosynthesis is very similar to ____, but in reverse.
Aerobic respiration
The oxidation of water and reduction of carbon dioxide is driven by…
The energy from the Sun
The metabolic processes in chloroplasts and mitochondria form a(n)…
Energy cycle
Photosynthesis uses the products of ____ as starting substrates.
Respiration
Aerobic respiration uses the products of ____ as starting substrates.
Photosynthesis
In plants, photosynthesis occurs in the…
Chloroplasts
In leaves, cells called ____ contain a large number of chloroplasts.
Mesophylls
Chloroplasts have a ____ membrane.
Triple
The inner membrane of a chloroplasts interact with…
The stroma
(an interior compartment)
The stroma contains…
Thylakoid discs
Thylakoid discs are stacked in columns called…
Grana
The thylakoid disks are separated from the stroma by the…
Thylakoid membrane
The area enclosed by the thylakoid membrane is called the…
Thylakoid space or lumen
The thylakoid space contains ____ and ____.
Photosynthetic pigments and protein complexes
List the two main stages of photosynthesis.
- Light-dependent reactions
- Light-independent reactions
Light-dependent reactions occur in the…
Thylakoids
Processes that occur during the light-dependent phase include…
(four)
- Capturing of solar energy
- Generation of ATP
- Reduction of NADP+ to NADPH
- Production of oxygen from water
Light-independent reactions take place in the…
Stroma
Processes that occur during the light-independent phase include…
(three)
- Carbon fixation
- Calvin cycle
- Production of organic molecules
____ are molecules that absorb visible light photons.
Pigments
A ____ is a packet of light that acts like a discrete bundle of energy.
Photon
A photon’s ____ is inversely proportional to its ____.
Energy ; wavelength
The ____ describes the process by which photons can remove electrons from molecules.
Photoelectric effect
What happens in a molecule if an incoming photon has precisely the right energy?
- The photon is absorbed
- Its energy is transfered to an electron
- The electron moves to a higher energy level
____ electrons are those that have received energy from a photon.
Excited
During photosynthesis, the pigments in a chloroplast act as…
Photoelectric devices
Each pigment has a characteristic…
Absorption spectra
(can only absorb a specific wavelength of light)
List the three main pigments found in chloroplasts.
- Chlorophyll A
- Chlorophyll B
- Carotenoids
The main pigment in plants is…
Chlorophyll A
Which wavelengths (colors) of light can chlorophyll A absorb?
Violet-blue and red
True or false:
Chlorophyll A is the only pigment that can directly convert light into chemical energy.
True
Chlorophyll B and carotenoids are considered…
Accessory pigments
Which wavelengths (colors) of light can chlorophyll B absorb?
Blue and red-orange
Which wavelengths (colors) of light can carotenoids absorb?
Blue and blue-green
True or false:
Many plants appear green because they absorb green light.
False
Plants appear green because they reflect green light.
Cells that contain carotenoids will often appear…
Orange
In addition to their role in photosynthesis, carotenoids also function as…
Anti-oxidants
Light is captured by the…
Photosystems
What is a photosystem?
A complex of pigments and proteins on the surface of the membrane
List the two components of a photosystem.
Antenna complex and the reaction center
The ____ contains hundreds of accessory pigment molecules.
Antenna complex
The function of the antenna complex is to…
Gather photons and feed light to the reaction center
The ____ contains one or more chlorophyll A molecules.
Reaction center
The function of the reaction center is to…
Excite electrons and transfer them to an electron acceptor
In plants, ____ is the electron donor.
Water
Chloroplasts contain ____ linked photosystems.
2
The electrons from water are transferred to ____, which is then used to produce ____ and ____.
NADP+
NADPH
ATP
The process of photosynthesis begins at….
Photosystem II
List the major steps of the light-dependent phase of photosynthesis.
(seven steps)
- Photons are absorbed and electrons are excited
- Water is oxidized
- Electrons are transferred to the b6f complex
- The energy from electrons is used to create a proton gradient
- Electrons are transferred to photosystem I, where they are reenergized
- Electrons enter the electron transport chain
- Electrons are transferred to NADP+ to form NADPH
For each pair of electrons from water, the light-dependent reactions produce…
1 NADPH
~1 ATP
During photosynthesis, a proton gradient is created across the…
Thylakoid membrane
When the proton gradient is created, the concentration is ____ in the thylakoid space than in the stroma.
Greater
In addition to the electron transport chain, photosynthesis can also produce a proton gradient by…
- The release of protons from the oxidation of water
- The loss of protons due to NADPH generation
True or false:
Chloroplasts can use ATP synthase to produce ATP.
True
During ATP synthesis in a chloroplast, protons move down their gradient from the ____ to the ____.
Thylakoid space to the stroma
List the two types of photophosphorylation.
- Non-cyclic
- Cyclic
During non-cyclic photophosphorylation…
The electron pair from water is transferred to NADP+, generating NADPH and ATP.
True or false:
Non-cyclic photophosphorylation produces enough energy to build organic molecules.
False
Cells must use cyclic photophosphorylation to do this.
During cyclic photophosphorylation…
Cells short-circuit photosystem I to create a larger proton gradient and cycle electrons back to the b6f complex.
Cyclic phosphorylation uses ____ to make ATP instead of NADPH.
High-energy electrons
True or false:
A cell can switch between cyclic and non-cyclic photophosphorylation as needed.
True
A major process that occurs during the light-independent phase is the…
Calvin cycle
What is the Calvin cycle?
A biochemical pathway that enables carbon fixation
During the Calvin cycle, the products of the light-independent phase are used to…
Convert inorganic CO2 to organic carbohydrates
The Calvin cycle is also called…
C3 photosynthesis
List the three phases of the Calvin cycle.
- Carbon fixation
- Reduction
- Regeneration of RuBP
The Calvin cycle occurs in the…
Stroma
During carbon fixation…
RuBP and CO2 are used to produce 2 molecules of PGA
Carbon fixation is catalyzed by…
Rubisco
(an enzyme)
(possibly the most abundant enzyme on earth!)
During the reduction phase of the Calvin cycle…
PGA is reduced to G3P, and some G3P is released from the cycle
During the regeneration phase of the Calvin cycle…
Most of the G3P is used to make RuBP
The Calvin cycle must take place ____ time(s) to incorporate enough carbon for a G3P molecule.
Three
The Calvin cycle must take place ____ time(s) to have enough carbon for one glucose molecule.
Six
True or false:
Glucose is a direct product of the Calvin cycle.
False
The Calvin cycle produces G3P, a component of glucose.
For every six CO2 molecules that enter the Calvin cycle, ____ G3P molecules are released.
2
Glucose is produced in the ____ using G3P.
Cytoplasm
Cells may also convert glucose into ____ or ____.
Sucrose (for transport)
Starch (for long-term storage)
List the two enzymatic activities of rubisco.
- Carboxylation
- Oxidation
Under normal conditions, rubisco favors ____, which leads to…
Carboxylation ; carbon fixation
Carboxylation is the addition of ____ to RuBP.
CO2
Under hot, dry conditions, rubisco favors ____ which leads to…
Oxidation ; photorespiration
Oxidation is the addition of ____ to RuBP, resulting in the release of ____.
O2 ; CO2
At 25 degrees Celsius, carboxylation happens 4x more often that oxidation, so…
20% of fixed carbon is lost to photorespiration
Photorespiration often results in hot, dry environments because…
Plants close their stomata to prevent water loss, which cuts of their supply of CO2 and traps O2 inside.
Plants can minimize photorespiration using the..
C4 and CAM pathways
Some plants can prevent photorespiration by…
Using PEP carboxylase to add CO2 to PEP, creating a 4-carbon molecule with more affinity for CO2 than rubsico
C4 plants minimize photorespiration by…
Separating the C3 and C4 pathways into different cells.
CAM plants minimize photorespiration by…
Using C4 pathways at night and C3 pathways during the day