Photosynthesis Flashcards
Autotroph
‘Self-feeder’ - e.g. cyanobacteria (chlorophyll), algae, plants.
- These organisms use light energy to create chemical bonds in more complex molecules.
Photosynthesis requires:
Carbon dioxide, sunlight, water
PHOTOSYNTHESIS (definition):
this is the process where light energy is converted to chemical energy. Autograph organisms are the only organisms that can perform this process. The chemical energy produced is used by the autotrophs themselves in cellular respiration; but they produce enough to provide energy for heterotrophs and the entire BIOSPHERE.
Equation of photosynthesis
6CO2 + 6H20 = C6H12O6 + 6O2
CHLOROPLAST DEFINITION:
this is an organelle that is only found in autotrophs and consists of special green membranes called THYLAKOIDS.
These thylakoids are arranged into stacks (like a column of coins) called GRANA (plural).
The stacks can be linked by thylakoids, known as intergranal thylakoids (lamellae).
The thylakoids float in a liquid cytoplasm forming a membrane free region called the STROMA.
The thylakoids are green due to the presence of chlorophyll.
What is the primary process by which plants convert light energy into chemical energy?
Photosynthesis
True or False: Photosynthesis occurs only in the roots of plants.
False
What are the main reactants in the photosynthesis equation?
Carbon dioxide and water
Fill in the blank: The overall equation for photosynthesis is 6CO2 + 6H2O + light energy → C6H12O6 + 6O2. The product glucose is represented as ______.
C6H12O6
Which organelle is primarily responsible for photosynthesis in plant cells?
Chloroplast
What pigment absorbs light energy for photosynthesis?
Chlorophyll
Multiple choice: Which wavelength of light is least effective for photosynthesis?
Green light
What is the name of the light-dependent reactions of photosynthesis?
Photophosphorylation
True or False: Oxygen is a byproduct of photosynthesis.
True
What are the two main stages of photosynthesis?
Light-dependent reactions and the Calvin cycle
Fill in the blank: The Calvin cycle occurs in the ______ of the chloroplast.
stroma
What is the main purpose of the light-dependent reactions?
To convert solar energy into chemical energy (ATP and NADPH)
Multiple choice: Which molecule is produced during the light-dependent reactions?
ATP & NADPH
What enzyme catalyzes the fixation of carbon dioxide in the Calvin cycle?
Ribulose bisphosphate carboxylase/oxygenase (RuBisCO)
True or False: Photosynthesis only occurs during the day.
False
What is the significance of photosynthesis to life on Earth?
It produces oxygen and organic compounds that are essential for life.
Fill in the blank: The process by which plants release oxygen and take in carbon dioxide is called ______.
Photosynthesis
What factor can affect the rate of photosynthesis?
Light intensity, carbon dioxide concentration, and temperature
Multiple choice: Which of the following is NOT a product of photosynthesis?
Oxygen
Glucose
Carbon dioxide
Carbon dioxide
What happens to the glucose produced in photosynthesis?
It can be used for energy, stored as starch, or converted into other organic compounds.
True or False: All living organisms can perform photosynthesis.
False
Fill in the blank: The light-independent reactions are also known as the ______ cycle.
Calvin
What is photolysis in the context of photosynthesis?
The splitting of water molecules to release oxygen.
Multiple choice: Which plant structure is responsible for gas exchange?
Stomata
Light reaction:
Water goes to the grana where light energy is used to split it into Hydrogen and Oxygen (catabolic reaction). The hydrogen produced in this step moves to the stroma and the oxygen produced is released into the atmosphere. As the bonds holding water together are broken, the energy released is converted into energy carrier molecules which also move to the stroma to provide the energy (chemical) for the Dark stage.
Dark Reaction:
in the stroma, CO2 and H2 from step 1, along with the energy carrying molecules (ATP; NADPH) result in the combination of CHO into the molecule we call glucose - C6H12O6.
Thylakoid
A membrane-bound structure found inside chloroplasts where the light-dependent reactions of photosynthesis occur. It contains chlorophyll and other pigments that capture light energy to produce ATP and NADPH. Thylakoids are stacked into structures called grana.
Grana
Stacks of thylakoids within the chloroplast where the light-dependent reactions of photosynthesis take place. They increase the surface area for capturing light energy and are connected by lamellae.
Lamellae
Thin membranous structures in chloroplasts that connect grana, helping to maintain their structure and facilitate the exchange of molecules between thylakoids. They play a role in photosynthesis by aiding in the distribution of light energy.
How does light effect rate of photosynthesis?
The rate of photosynthesis increases with light until some other factor – eg: CO2 concentration –
becomes rate limiting.
How does CO₂ Concentration effect Photosynthesis Rate?
Higher CO₂ increases photosynthesis because CO₂ is a raw material for the Calvin cycle.
Plateaus at high CO₂ levels when other factors (light, temperature) become limiting.
How does temperature effect rate of photosynthesis?
Increases with temperature as enzymes work faster.
Peak at an optimum temperature (usually 25–35°C for most plants).
Declines at high temperatures as enzymes (e.g., Rubisco) denature.
Limiting factors (Photosynthesis)
Increase in light intensity increases rate of photosynthesis up to a certain point, when light
saturation point is reached (1). Carbon dioxide becomes a limiting factor. Carbon dioxide is a
reactant/substrate required by plants for photosynthesis to make glucose (1) so if carbon
dioxide is constant then so will be the rate of photosynthesis as it is an enzyme driven
biochemical reaction (1).
