Untitled Quiz

Study Notes

Biology is the study of living things and provides an understanding of life.
Cell biology is a specialized branch of biology that focuses on the study of cell structures and their functions.
Cytology deals with the scientific study of cells.
Cells are the fundamental building blocks of all living organisms.

Prokaryotic cells:
- Examples: Bacteria
- Characteristics:
  - Smaller size (1-5 µm)
  - Have a cell wall outside the cell membrane
  - Lack a nuclear envelope separating DNA from other cellular constituents
  - Lack histones bound to their DNA
  - Lack membranous organelles
  - Divide by binary fission
Eukaryotic cells:
- Examples: Amoeba
- Characteristics:
  - Larger than prokaryotic cells
  - Have a distinct nucleus surrounded by a nuclear envelope
  - Histones are associated with genetic material
  - Numerous membrane-bound organelles are present in the cytoplasm
  - Divide by mitosis and meiosis

The eukaryotic cell consists of two main parts:
- Cytoplasm: Contains matrix (cytosol), organelles, cytoskeleton, and deposits of carbohydrates, lipids, and pigments. The cytoplasm of eukaryotic cells is divided into several distinct compartments by membranes that regulate the intracellular traffic of ions and molecules.
- Nucleus: Contains the cell's genetic material (DNA)

The outermost component of the cell, separating the cytoplasm from the extracellular environment.
Acts as a barrier between the cell's interior and its surroundings
Regulates the passage of substances in and out of the cell
Acts as a unique identifier for the organism
In multicellular organisms, cell junctions with specialized features of the plasma membranes connect cells together and facilitate communication between neighboring cells.

The structure and function of the cell's plasma membrane depend on:
- Lipid solubility: Lipid-soluble molecules enter cells more rapidly than water-soluble molecules suggesting lipids are a component of the plasma membrane.
- Lipid properties: The formation of biological membranes is based on lipid properties, and all cell membranes share a common structural organization - a bilayer of phospholipids with associated proteins.
- Fluid-mosaic model: The widely accepted model proposes that the membrane is a fluid phospholipid bilayer in which protein molecules are partially or wholly embedded.
These various proteins vary in structure and function, creating a mosaic pattern within the membrane.

The aqueous environment inside and outside the cell prevents membrane lipids from escaping the bilayer.
Membrane lipids can move about and change places within the plane of the bilayer, making the membrane a two-dimensional fluid, essential for its function.

Proteins constitute 25-75% of the mass of various cell membranes.
Membrane proteins carry out specific functions for different membranes.
Two general classes of membrane proteins:
- Integral membrane proteins: Directly embedded in the lipid bilayer. Transmembrane proteins span the lipid bilayer with proteins exposed on both sides.
  - Other types include membrane-associated or lipid-linked proteins.
- Peripheral membrane proteins: Not inserted into the lipid bilayer, associated with the membrane indirectly, generally called protein attached through interactions with integral membrane proteins.

The carbohydrate chains of glycolipids and glycoproteins serve as the cell's "fingerprints," unique identification markers.
The carbohydrate chains form a carbohydrate coat enveloping the outer surface of the plasma membrane.
Proteins serve as links to the cytoskeletal filaments on the inside and to the extracellular matrix on the outside.