Biology Cell Theory and Types

Cell Theory

• All living things are made of one or more cells, or their byproducts.
• Cells are the basic unit of life, capable of carrying out all life processes.
• All cells arise from pre-existing cells, not from non-living matter.

Types of Cells

• Prokaryotic cells: These are the most ancient cell type, still found today. They are simple, single-celled organisms lacking a membrane-bound nucleus. A key example is bacteria cells.

• Eukaryotic cells: These are more complex cells that can exist as single or multicellular organisms. They have a more complex internal organization, including a nucleus. Examples include amoebas, plants, and animals.

Cell Organelles

• Cells contain smaller parts called organelles, each with specific functions for maintaining life processes.
• Some organelles are common to both plant and animal cells while others differ.

Cell Membrane

• A flexible, protective barrier that holds the cell's contents and regulates the exchange of substances.
• It communicates with other cells and provides support.
• Composed of a phospholipid bilayer, where the outside of the membrane is hydrophilic (attracted to water) and the inside is hydrophobic (repelled by water).
• Also a semi-permeable membrane, controlling what substances enter and leave the cell.

Cytoplasm

• The jelly-like substance filling the cell.
• Surrounds the organelles.
• Contains nutrients needed by the cell and is where many chemical reactions occur.
• Allows movement of nutrients and organelles within the cell.

Nucleus

• Controls all cell activities and contains all genetic information (DNA).
• Surrounded by a nuclear envelope with pores to allow material transport.

Inside the Nucleus

• Genetic information is stored in chromosomes.
• Chromosomes contain DNA, which carries coded instructions for all cell activities.
• The nucleolus is a dense region inside the nucleus where ribosomes are made. (Ribosomes are the protein factories of the cell).

Vacuoles

• Membrane-bound, fluid-filled organelles that store nutrients, wastes, and other substances.
• In plant cells, a large central vacuole stores water, maintaining cell firmness.
• Animal cells have smaller vacuoles.

Mitochondria

• Often called the "power plants" of the cell.
• They convert chemical energy (from sugar) into energy usable by the cell (cellular respiration).

Lysosomes

• Small, round organelles filled with enzymes.
• Digest invading bacteria or damaged cell parts.
• Only found in animal cells.

Endoplasmic Reticulum (ER)

• A network of interconnected tubes that transports materials within the cell.
• Rough ER: Associated with protein production, studded with ribosomes.
• Smooth ER: Associated with fat and oil production, lacks ribosomes.

Golgi Apparatus

• Receives proteins from the ER.
• Modifies, sorts, and packages them for delivery within or outside the cell.
• Involved in mucus production.
• Looks like a stack of flattened membranes.

Cytoskeleton

• An internal network of protein fibers that maintains the cell's shape.

Organelles in Plant Cells

• Only certain organelles are found specifically in plant cells, like the cell wall.
• The cell wall is a rigid structure providing strength, protection, and support.

Chloroplasts

• Found in plant cells and some algae.
• Contain chlorophyll, which uses sunlight to convert carbon dioxide and water into sugar and oxygen (photosynthesis).

Test your knowledge on cell theory, the types of cells, and the organelles that make up living organisms. This quiz covers fundamental concepts essential for understanding biology, including the differences between prokaryotic and eukaryotic cells. Dive into the components that help sustain life at the cellular level.