Fundamentals of Life: Cells, Nutrition, and Reproduction

Differences Between Living and Non-Living Things

Living things exhibit several defining characteristics:

• They are made of cells and perform the three vital functions: relationship, nutrition, and reproduction.
• They are composed of essential biomolecules: carbohydrates, lipids, proteins, and nucleic acids.

Cell Theory Fundamentals

Cell Theory establishes three core principles:

1. All living things are made up of cells.
2. Cells are formed from pre-existing cells.
3. A cell performs the three vital functions (relationship, nutrition, and reproduction).

Cell Types and Structure

Cell Types

• Prokaryotes: These are the most primitive cells and do not have a defined nucleus.
• Eukaryotes: These cells possess a nucleus where the genetic material is stored.

Basic Structure of the Cell (Eukaryotic)

• Plasma Membrane: It is a thin wrapper surrounding the cell, regulating the flow of nutrients.
• Cytoplasm: A gel-like substance where cellular organelles float.
• Nucleus: The central organelle of the cell where the genetic material is located. The nucleus is unique to eukaryotes.

Nutrition: Autotrophic Processes

Autotrophic nutrition occurs in certain organisms, such as plants and some bacteria, allowing them to produce their own food.

Phases of Photosynthesis

1. Absorption and Transport: The roots absorb water and minerals from the ground. These substances travel up the trunk and reach the leaves, where they combine with carbon dioxide (CO₂) and sunlight.
2. Conversion (Photosynthesis): In the chloroplasts, photosynthesis takes place. Using sunlight, water, and mineral salts, the plant produces glucose (sugar) and releases oxygen.
3. Distribution: The generated organic matter (glucose) is distributed throughout the plant, serving to regenerate structures and facilitate growth.
4. Cellular Respiration: Glucose is broken down in the presence of oxygen, resulting in water and CO₂.

Importance of Photosynthesis

During photosynthesis, plants produce significantly more oxygen than they consume through respiration. This crucial process is responsible for creating and maintaining an atmosphere suitable for life to exist on Earth.

Nutrition: Heterotrophic Processes

Heterotrophs are organisms that must feed on other living things because they cannot perform photosynthesis.

Stages of Heterotrophic Nutrition

• Incorporation of organic matter from the environment.
• Gas exchange.
• Transportation of nutrients.
• Use of the organic matter (metabolism).
• Disposal of waste substances into the environment.

Reproduction: Maintaining Life on Earth

Reproduction ensures the continuation of life on Earth and the perpetuation of species.

Asexual Reproduction in Unicellular Organisms

Reproduction in unicellular organisms typically involves cell division. The individuals generated through this type of asexual reproduction are genetically identical to each other and to their parent.

Asexual Reproduction in Animals

Asexual reproduction occurs even in some more evolved species. Two common types include:

1. Fragmentation: A part of the individual separates from the body and develops into new individuals. If an individual has been injured, it can often repair the injured part through regeneration.
2. Budding: Cells on the parent individual generate a bulge called a bud. This bud develops into a new individual. If the bud separates from the parent, it gives rise to an independent organism.