Cellular Life: Nutrition, Energy, and Plant Processes
Essential Life Functions and Cellular Basis
Three Vital Functions for Organisms
Living organisms perform three vital functions:
- Nutrition: Obtaining the matter and energy necessary to live.
- Interaction/Relationship: Taking in information from the environment and responding to it for survival.
- Reproduction: Giving rise to new living beings, similar to those from which they originated.
The Cell: Fundamental Unit of Life
The cell is the structural and functional unit of all living beings, capable of performing these three vital functions. Cells can be unicellular or multicellular. In multicellular organisms, cells tend to specialize and form part of organ systems.
Nutrition: Acquiring Energy and Matter
Phases of Nutrition
Nutrition in an organism involves several phases:
- Obtaining nutrients.
- Transporting nutrients into the cells.
- Obtaining energy from these nutrients.
What Are Nutrients?
Nutrients are elements that organisms need from their environment to perform essential vital functions. Some nutrients are obtained directly, while others are acquired from the environment through processes like photosynthesis or the digestion of food.
Types of Nutrients
- Inorganic Nutrients: Water, gases (like carbon dioxide), and mineral salts.
- Organic Nutrients: Carbohydrates, fats (lipids), proteins, and nucleic acids.
Nutrient Transport
In unicellular organisms, nutrition occurs through the direct incorporation of necessary environmental nutrients. Multicellular organisms typically obtain nutrients through specialized body structures, such as roots and leaves in plants, or the stomach and intestines in animals.
Energy Acquisition
Living beings are capable of utilizing different forms of energy, primarily light energy (for photosynthesis) and chemical energy (from food).
Matter and Energy Utilization
When energy is obtained, it is used to perform other vital functions, including:
- Maintaining internal conditions (homeostasis).
- Growth and development.
- Internal movement.
This organic matter is formed by organic molecules (organic nutrients).
Types of Nutrition and Energy Acquisition
Organisms acquire energy in different ways:
- Autotrophic Nutrition: Organisms produce their own food (e.g., plants through photosynthesis).
- Heterotrophic Nutrition: Organisms obtain food by consuming other organisms or organic matter.
Cells use chemical energy from molecules for internal processes. The method of extracting this energy can be:
- Aerobic Respiration: Utilizes oxygen to break down glucose molecules, releasing energy.
- Anaerobic Respiration (Fermentation): Occurs without oxygen, breaking down molecules to release energy.
Plant Nutrition: The Foundation of Life
Plants form the base of the food chain for most organisms in the biosphere. They are autotrophic and typically aerobic.
Obtaining Nutrients in Plants
Plants obtain external inorganic matter through photosynthesis.
Simple Plants: Bryophytes and Algae
Simpler plants, such as bryophytes and algae, absorb water, mineral salts, and gases directly through their entire surface.
Complex Plants: Pteridophytes and Spermatophytes
More complex plants, like pteridophytes and spermatophytes, have specialized structures for obtaining nutrients:
- Stomata: These are small openings on the plant’s surface that allow the exchange of carbon dioxide and other gases with the external environment. They can open and close regularly.
- Roots: These plants absorb water and minerals from the soil through their roots. Roots significantly increase the surface area for contact with the soil, enhancing water and nutrient absorption capacity.
Photosynthesis: Converting Light to Chemical Energy
Photosynthesis is the process by which plants synthesize organic molecules from inorganic molecules using solar energy. The production of organic molecules occurs from inorganic molecules absorbed from the environment, such as carbon dioxide and water. The energy needed is captured by a green pigment, chlorophyll, which accumulates light energy and transforms it into chemical energy stored in glucose molecules. This process releases oxygen as a waste product into the external environment.
Nutrient Transport in Plants
Pteridophytes and spermatophytes have specialized conducting vessels to transport substances throughout the organism’s cells. There are two main types of conducting vessels:
- Xylem: Formed by hollow, tubular cells that create woody vessels. These cells are rigid and conserve their cell walls. Xylem transports raw sap (water and dissolved minerals absorbed by the roots) from the roots up to the leaves.
- Phloem: Composed of living cylindrical sieve tubes. Phloem transports elaborated sap (water, glucose, and other organic compounds produced during photosynthesis) from the leaves to the rest of the plant.
Energy Acquisition in Plant Cells
All cells of an organism need energy to perform vital functions. This energy is extracted by decomposing organic molecules and releasing chemical energy.
Cellular Respiration
Cellular respiration is a process of molecular decomposition that produces energy with the intervention of oxygen. It primarily occurs in the mitochondria. One molecule of glucose combines with oxygen to produce energy, which is stored in ATP molecules. This process also eliminates carbon dioxide from the organism and depends on the availability of glucose.