Cell Biology: Cytoskeleton, Cilia, and Flagella

Cell Structure and Function

• Mitochondria and chloroplasts have circular DNA and reproduce by binary fission, similar to bacteria.
• They are similar in size to some bacteria.

Cytoskeleton

• The cytoskeleton is the structural framework of the cell, supporting and holding it up.
• It allows organelles to move within the cell and moves chromosomes during cell division.

Cilia and Flagella

• Cilia are hair-like projections on the surface of cells, while flagella are tail-like projections at the end of cells.
• They allow the cell to move or create movement, consisting of microtubules encased in extensions of the plasma membrane.

Vacuoles

• Vacuoles are membrane-bound liquid-filled spaces that act as storage components.
• In plant cells, there is a single large vacuole called a cell sap, which provides structure and storage, and contains enzymes.
• In animal cells, there are many smaller vacuoles that are temporary, with adipose cells having large vacuoles that store lipids.

Cell Wall

• The cell wall is a layer surrounding the plasma membrane, providing strength and rigidity for the cell.
• It is found only in plants, bacteria, and fungi, and is made of cellulose, hemicellulose, and pectin.

Plasma Membrane

• The plasma membrane is the boundary layer of a cell, separating the cell's internal environment from its surroundings.
• It regulates all interactions between the cell and its outside environment.

Cell Types

• Cells are the basic structural unit of all living things.
• Cell theory states that all organisms are composed of cells, all cells come from pre-existing cells, and the cell is the smallest living organizational unit.

Prokaryotic Cells

• Prokaryotic cells are small in size and have a simple cell structure, including bacteria and archaea.
• They lack membrane-bound organelles and have a singular circular DNA chromosome in a nucleoid.

Eukaryotic Cells

• Eukaryotic cells are larger in size and have a complex cell structure, including animal, plant, fungi, and protist cells.
• They contain membrane-bound organelles and can be unicellular or multicellular.

Bacteria

• Bacteria are microscopic organisms that play an important role in the ecosystem, breaking down substances such as plant and animal wastes.
• There are two types of bacteria: gram-positive, which has a thicker layer of murein in the cell wall, and gram-negative, which has a thin layer of murein.

Cell Transport

• Pinocytosis is the entry of fluid and nutrient substances into the cell.
• Phagocytosis is the entry of large particles like bacteria and cell debris into the cell.
• Receptor-mediated endocytosis uses receptor proteins to acquire targeted molecules.
• Exocytosis is the movement of substances out of the cell, using transport vessels containing waste or secretory substances that fuse with the plasma membrane.

Cell Theory and Replication

• Cell theory states that all organisms are composed of cells, all cells come from pre-existing cells, and the cell is the smallest living organizational unit.
• Cell replication is a form of cell division that produces genetically identical daughter cells to help with the nucleus-cytoplasm ratio, growth and development, and maintenance and repair.