AP Biology - Chapter 8 (Autotrophs-CAM Plants)

Autotrophs

Autotrophs

Self feeders

Phototrophs

Plants that make their own food from the sun’s energy

Heterotrophs

Consumers, live on compounds made from autotrophs

Photosynthesis

The biochemical process by which green plants, algae, and some bacteria convert light energy, typically from the sun, into chemical energy stored in glucose. During this process, these organisms use carbon dioxide from the atmosphere and water from the soil, releasing oxygen as a byproduct. This process not only sustains the life of the autotrophs performing it but also provides the essential oxygen and organic matter that support heterotrophic life forms.

Xylem

Vascular tissue in plants responsible for transporting water and minerals from the roots to the leaves.

Reduction

Addition of an Electron

Oxidation

Loss of an Electron

Engelmann’s Experiment

A landmark experiment that demonstrated the role of light in photosynthesis by observing the growth of algae in different light wavelengths, highlighting which wavelengths were most effective for photosynthesis.

Best Wavelengths for Photosynthesis

Red (700) and Violet-Blue (400-500)

Glyceraldehyde 3-Phosphate (G3P)

3 Carbon carbohydrate that is a direct product of the Calvin Cycle

Calvin Cycle

The Calvin Cycle, also known as the light-independent reactions, occurs in the stroma of chloroplasts and is an anabolic pathway that synthesizes glucose from carbon dioxide. It primarily involves three phases: Carbon fixation, Reduction, and Regeneration of ribulose bisphosphate. The cycle consumes ATP and NADPH produced during the light reactions of photosynthesis, facilitating the conversion of inorganic carbon (CO₂) into organic molecules. During the Reduction phase, 3-phosphoglycerate is reduced to Glyceraldehyde 3-phosphate (G3P) using ATP and NADPH. G3P can then be used to form glucose and other carbohydrates, providing crucial energy and structural components for the plant.

Phase 1 of the Calvin Cycle

Carbon Fixation occurs where CO₂ is fixed to ribulose bisphosphate (RuBP) by the enzyme RuBisCO, forming 3-phosphoglycerate (3-PGA). This sets the stage for the following reduction phase.

Phase 2 of the Calvin Cycle

Reduction occurs where 3-phosphoglycerate (3-PGA) is converted into Glyceraldehyde 3-Phosphate (G3P) using ATP and NADPH. This process facilitates the synthesis of glucose and other carbohydrates.

Phase 3 of the Calvin Cycle

Regeneration occurs where Glyceraldehyde 3-Phosphate (G3P) is used to regenerate ribulose bisphosphate (RuBP), allowing the cycle to continue. This phase requires ATP.

RuBP

Ribulose bisphosphate is a five-carbon sugar that acts as the CO₂ acceptor in the Calvin Cycle of photosynthesis, facilitating the fixation of carbon dioxide.

C₃ Plant

A type of plant that uses the Calvin Cycle for photosynthesis, fixing carbon dioxide directly into a three-carbon compound (3-phosphoglycerate). This is the most common form of photosynthesis, ideal for moderate climates.

C₄ Plant

A type of plant that utilizes a unique photosynthesis pathway, fixing carbon dioxide into a four-carbon compound (oxaloacetate) before entering the Calvin Cycle. This adaptation allows them to efficiently photosynthesize under high light intensities, temperatures, and low carbon dioxide conditions, often found in arid environments.

Photorespiration

Process in plants in which oxygen is consumed and carbon dioxide is released, occurring when the enzyme RuBisCO reacts with oxygen instead of carbon dioxide. This process is generally wasteful as it counteracts photosynthesis, reducing overall productivity.

CAM Photosynthesis

CAM is a photosynthetic adaptation found in some plants, particularly succulents, where they fix carbon dioxide at night into organic acids, which are then used during the day for photosynthesis. This process helps to minimize water loss in arid conditions.

Things that are Reduced in Photosynthesis

6CO₂ and C₆H₁₂O₆

Things that are Oxidized in Photosynthesis

6H2₂O and 6O₂

Photosynthesis Equation

(Light) Energy + 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Carotenoid

A class of pigments found in plants, often responsible for the yellow, orange, and red colors. Carotenoids play important roles in photosynthesis by capturing light energy and protecting cells from damage caused by excess light.

Chlorophyll B

A pigment found in plants that assists in photosynthesis by absorbing light primarily in the blue and red wavelengths, complementing the absorption capabilities of chlorophyll A.

Chlorophyll A

A green pigment crucial for photosynthesis, primarily absorbing blue and red light, and plays a vital role in converting solar energy into chemical energy.

Photons

Particles of light that carry energy and are the fundamental particles of electromagnetic radiation, including visible light. They exhibit both wave-like and particle-like properties.

What is used to make one molecule of Glucose

18 ATP and 12 NADPH

Reducing Agent in the Calvin Cycle

6 NADPH

Phloem

Vascular tissue in plants responsible for transporting sugars and nutrients produced by photosynthesis from the leaves to other parts of the plant.