10: Photosynthesis, C3, C4 and CAM pathways, Corn, Starch: Flashcards
Compare and contrast C3 and C4 photosynthesis.
C3: CO₂ directly enters the Calvin cycle; more common but inefficient in hot, dry environments due to photorespiration.
C4 (e.g., corn): CO₂ first fixed into a 4-carbon compound in mesophyll cells, then sent to bundle sheath cells for the Calvin cycle; more efficient, especially under high heat/light.
Evaluate the impact of synthetic fertilisers and pesticides on corn and the environment.
Fertilisers (Haber-Bosch process) boost yields but release greenhouse gases.
Pesticides help control pests but cause bioaccumulation and biomagnification, harming ecosystems and reducing biodiversity.
Explain the significance of hybridisation in corn agriculture.
Hybridisation boosts crop yield through heterosis (hybrid vigour),
but it prevents farmers from saving seeds, making them rely more on companies for new seeds each season, which can reduce their economic independence
How has corn shaped human societies, especially in the Americas?
Corn was domesticated by Indigenous peoples and became a staple crop, central to diet and culture.
Today, it holds economic importance globally in food, fuel, and industry.
What are angiosperms?
Flowering plants, the most diverse group of land plants.
Define C3 photosynthesis.
A pathway where the first stable carbon fixation product is a 3-carbon compound; most common form but less efficient in hot/dry conditions.
Define C4 photosynthesis.
A pathway where CO₂ is first fixed into a 4-carbon compound in mesophyll cells, then delivered to bundle sheath cells—found in plants like corn.
What is chloroplast?
The organelle in plant cells where photosynthesis occurs.
What is chlorophyll?
A green pigment in plants that absorbs light for photosynthesis.
What does ‘domesticated’ mean in plant biology?
Plants bred and genetically modified by humans for desirable traits.
What is heterosis (hybrid vigour)?
Enhanced qualities (size, yield, resilience) in offspring from crossing genetically distinct parents.
What is hybridisation?
The crossing of two genetically different individuals to produce offspring with desirable traits.
What is inbreeding depression?
Reduced fitness due to mating between closely related individuals.
Describe light-dependent reactions.
Occur in thylakoids; convert light energy into ATP and NADPH.
Describe light-independent reactions (Calvin cycle)?
Occur in the stroma; use ATP and NADPH to fix CO₂ into glucose.
What does ‘monoecious’ mean?
A plant that has both male and female reproductive organs.
Define photorespiration.
A process where Rubisco binds O₂ instead of CO₂, reducing photosynthesis efficiency.
What is Rubisco?
an enzyme that fixes CO₂ in the Calvin cycle and also initiates photorespiration.
What is the stroma?
The fluid inside chloroplasts where the Calvin cycle occurs
Define teosinte.
A wild grass from Mexico/Central America, the ancestor of modern corn.
What is the thylakoid membrane?
Structure within chloroplasts where light-dependent reactions take place.
