Nutrition in Plants and Protists

Definition: Photosynthesis is the biochemical process whereby certain organisms synthesize food using sunlight as an energy source.
- Photosynthetic Organisms: Most plants are photosynthetic and thus autotrophic. Examples:
- Heterotrophic Plants: Some plants like dodder (a parasitic flowering plant) and Indian pipe (which gets nutrients from fungi) do not photosynthesize.
- Carnivorous Plants: Certain insect-eating plants can both photosynthesize and obtain nutrients from other organisms.
- Microorganisms: Algae and various microorganisms are also capable of photosynthesis.
Importance of Photosynthesis:
- Produces food available to various organisms.
- Releases oxygen necessary for cellular respiration in most living organisms.

In photosynthesis, organisms use energy from sunlight to synthesize food.
Organisms that can synthesize their own food are called autotrophs; organisms that must obtain food from the environment are called heterotrophs.
A by-product of photosynthesis necessary to most living organisms is oxygen.
If all photosynthetic processes were to cease, life on Earth would face catastrophic repercussions, as oxygen levels would drop drastically and organic food sources for heterotrophs would diminish.

Photosynthesis is essentially the reverse of aerobic cellular respiration. Here's a breakdown:
- Aerobic Cellular Respiration: Glucose is broken down in the presence of oxygen, producing carbon dioxide and water.
- Photosynthesis: Carbon dioxide and water are converted into glucose and oxygen.
- Energy flow: In respiration, energy from glucose is stored in ATP, while in photosynthesis, energy from ATP is stored in glucose.
- Unique process: Photosynthesis utilizes absorbed light energy to produce ATP, a process not mirrored in respiration.

Glucose and oxygen are products of the process of photosynthesis.
Carbon dioxide and water are raw materials for the process of photosynthesis.
Glucose is broken down by the process of cellular respiration.
Carbon dioxide and water are the raw materials for the process of photosynthesis. Glucose is formed by the Calvin Cycle.

Definition: Light is a form of electromagnetic energy.
- Light travels through space in the form of waves.
- Wavelengths for visible light range from 3,600 Å (violet) to 7,600 Å (red). A mixture of all visible wavelengths appears white.
- Energy transmission: The energy of light is delivered in units called photons (quanta). The energy of each photon varies inversely with the wavelength; shorter wavelengths carry more energy.

When photons of the correct wavelength hit a pigment, energy is absorbed by electrons. Color perception depends on wavelengths that pigments reflect rather than absorb.
Definition of Pigments: Materials that absorb certain wavelengths of light.
Chlorophyll: The most vital pigment for photosynthesis, existing in two main forms:
- Chlorophyll a
- Chlorophyll b
- Chemical Structure: Similar to hemoglobin but with magnesium instead of iron.
- Absorption: Chlorophyll absorbs blue-violet and red-orange light but only minimally absorbs yellow and green, hence appearing yellow-green.
Other pigments (like carotenes and xanthophylls) assist in photosynthesis by absorbing different light wavelengths.

The most important pigment in photosynthesis is chlorophyll.
Other pigments found in green plants include carotenes and xanthophylls.
Hemoglobin contains iron; chlorophyll contains magnesium.
Objects that absorb all wavelengths of light except red will appear red in color.
The colors of light not absorbed by chlorophyll are yellow and green.
The color of chlorophyll is yellow-green.

Chloroplasts: Cellular organelles in photosynthetic organisms where the reactions of photosynthesis occur.
- Structure includes a membrane-sandwiched stack of structures called grana composed of thylakoids and the surrounding fluid known as stroma.

The rate of photosynthesis can be influenced by:
- Temperature: Optimal growth range typically falls between 0°C - 40°C.
- Light Intensity: Higher intensity generally boosts rates until saturation.
- Carbon Dioxide Concentration: Increased concentration initially raises the rate before hitting a plateau.
- Minerals: Essential minerals required include nitrogen, magnesium, iron, copper, manganese, and zinc.

As temperature increases from 0°C to 40°C, the rate of photosynthesis rises up to a peak and then declines if temperature continues to rise.
In bright light, the optimal temperature range for maximum photosynthesis is typically between 20°C to 30°C.
As light intensity increases, the rate of photosynthesis increases until saturation.
As CO₂ concentration increases, the rate of photosynthesis increases and then stabilizes.

Thylakoids: Membrane-bound structures within chloroplasts containing the chlorophyll where light-dependent reactions occur.
- Grana: Stacks of thylakoids.
- Stroma: The fluid matrix surrounding the grana in a chloroplast.
Endosymbiotic Theory: Scientists postulate that mitochondria and chloroplasts may share an evolutionary origin with free-living prokaryotic cells due to similar size, structure, and DNA characteristics.

Photosynthesis: The process by which autotrophs convert sunlight into usable energy.
Pigment: Molecule that absorbs certain wavelengths of light and reflects/transmits others.
Chlorophyll: The most common and important photosynthetic pigment in plants and algae.
Chloroplasts: Organelles that contain chlorophyll.
Stroma: Gel-like material surrounding the thylakoids in chloroplasts.
Grana: Stack of disk-shaped structures that contain chlorophyll.
Photosystems: Light-collecting units of the chloroplast.

The wavelengths absorbed by chlorophyll include blue-violet and red; reflected are green and yellow.
Light energy is crucial to the photosynthetic process as it powers the conversion of CO₂ and water to glucose.
Oxygen is produced during the light-dependent reactions of photosynthesis and is released as a byproduct.
The Calvin Cycle requires carbon dioxide, ATP, and NADPH, derived from the light-dependent reactions.
- The main compound formed from carbon dioxide in the Calvin cycle is glucose.
Plants store energy in the form of starch for later use.