Nutrition: Heterotrophic and Autotrophic Types

Heterotrophic Nutrition

• Heterotrophs rely on autotrophs for organic food.
• Three types: holotrophic, saprophytic, and parasitic.

Autotrophic Nutrition

• Autotrophs produce their own food.

Photosynthesis

• Photosynthesis is a process where autotrophs create organic compounds from inorganic materials.
• The chemical reaction for photosynthesis is: 6CO2 + 6H2O → C6H12O6 + 6O2
• It's a vital process for life on Earth, producing oxygen and forming the base of most food chains.
• Photosynthesis occurs in chloroplasts, specialized organelles within plant cells.
• Photosynthesis is generally comprised of two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle).

Photosynthesis Details

• Chlorophyll is a pigment crucial for photosynthesis, with different types (a and b) absorbing different wavelengths of light.
• Chloroplasts are organelles where photosynthesis occurs.
• Stomata are pores on leaves that regulate gas exchange.

Light-Dependent Reactions

• These reactions occur in the thylakoid membranes of chloroplasts.
• Sunlight provides the energy for the reactions, involving chlorophyll and other pigments.
• Water molecules are split (photolysis), releasing oxygen as a byproduct and providing electrons.
• This energy is converted into ATP (adenosine triphosphate) and NADPH, energy-carrying molecules for the next stage.

Light-Independent Reactions (Calvin Cycle)

• These reactions occur in the stroma of the chloroplasts.
• ATP and NADPH generated from the light-dependent reactions power the Calvin cycle.
• Carbon dioxide from the atmosphere is fixed into organic molecules, primarily glucose.
• The cycle uses carbon dioxide to build sugar molecules.

Chlorophyll and Other Pigments

• Chlorophyll is the primary light-capturing pigment.
• Accessory pigments, like carotenoids, absorb wavelengths chlorophyll can't, expanding the range of usable light energy.

Chemosynthesis

• Chemosynthesis is an alternate process for producing organic compounds. It uses chemicals, not sunlight, as the energy source.

Factors Affecting Photosynthesis

• Light intensity: Increases photosynthesis rate up to a certain point, then has less impact.
• Carbon dioxide concentration: Higher levels generally increase photosynthesis rates until a limit.
• Temperature: Photosynthesis rates increase with temperature within an optimal range, but can decrease outside of it due to impact on enzymes.
• Water availability: Water shortage leads to reduced gas exchange through stomata closure, hindering photosynthesis.
• Nutrients: Essential minerals like magnesium (in chlorophyll) and iron are needed for optimal enzyme function, and shortages limit photosynthesis.

Products of Photosynthesis

• Glucose: A simple sugar, a major energy source for plants.
• Oxygen: Released as a byproduct of the light-dependent reactions.

Significance of Photosynthesis

• Oxygen production: Photosynthesis is the primary source of atmospheric oxygen for most life forms.
• Food source: Producers are the base of most food chains, providing the energy source consumed by primary consumers (herbivores).
• Carbon dioxide removal: Photosynthesis absorbs atmospheric carbon dioxide, reducing greenhouse gases and potentially regulating global climate.