Biology Chapter 3: Cells

Study Notes

The cell is the most basic and fundamental unit of an organism, often referred to as the building block.
Robert Hooke discovered cells using cork, showcasing their varied shapes and sizes based on functions and compositions.

Lack a nucleus; genetic material is freely suspended in a region called the nucleoid.
Typically unicellular microorganisms, measuring 0.1 - 0.5 μm in diameter.
Reproduce asexually through binary fission.
Examples include archaea, bacteria, and cyanobacteria.

Contain a nucleus and are generally larger, ranging from 10 to 100 μm in diameter.
Can reproduce both sexually and asexually.
Found in plants, fungi, and animals, with a plasma membrane for nutrient transport and communication.

Simple Microscope: Basic device using a single lens for low magnification, useful for small object examination; e.g., magnifying glass.
Compound Microscope: Utilizes multiple lenses and light for higher magnification; essential in biological research.
Scanning Electron Microscope (SEM): Scans surfaces with an electron beam; produces 3D images, expensive, and unsuitable for internal structure viewing.
Transmission Electron Microscope (TEM): Transmits electrons through thin specimens, providing detailed internal images; cannot be used on living specimens.

Cells provide structure, support, and maintenance of the organism’s shape.
Organelles within the cell, such as the nucleus and vacuoles, perform essential functions like containing genetic information and maintaining water balance.
The cell membrane (plasma membrane) regulates entry and exit of substances, and the cell wall (only in plants) provides additional protection and support.

Protoplasm: Composed of the nucleus and cytoplasm, where the nucleus contains DNA.
Ribosomes: Sites of protein synthesis, either freely in the cytoplasm or attached to the endoplasmic reticulum.
Golgi Apparatus: Involved in manufacturing, storing, packing, and transporting materials within the cell.
Chloroplasts: Conduct photosynthesis, uniquely found in plant cells.
Vacuoles: Store substances and help maintain cell shape; larger in plant cells.
Lysosomes: Digest unwanted materials; known as the cell’s 'suicide bags'.
Endoplasmic Reticulum (ER): Synthesizes molecules; Rough ER has ribosomes for protein synthesis, while Smooth ER assists metabolism and transports molecules.

Both types contain cell membrane, nucleus, cytoplasm, ribosomes, and mitochondria, yet differ in structure and function.
Plant cells have a fixed shape due to a cell wall and large vacuoles, while animal cells have irregular shapes and smaller vacuoles.

Stem cells can differentiate into various cell types; groups of similar cells are organized into tissues.
Four main tissue types in humans: muscle (movement), connective (support), nervous (communication), and epithelial (protection).

Diffusion: Movement of substances from high to low concentration; essential for nutrient and gas exchange.
Osmosis: Movement of water across a semipermeable membrane, driven by concentration differences; vital for cellular hydration and function.

Surface area must be large relative to volume for effective transport of materials; as cells grow, volume increases faster than surface area, potentially limiting nutrient intake and waste removal.