Unit: 06- Cell Structures and Functions

Microscopy is the technical field of using microscopes to view samples or objects. There are three well-known branches of microscopy, optical, electron and scanning probe microscopy.

Permeability is a measure of the ability of a material to transmit fluids. [A semipermeable membrane, also termed a selectively-permeable membrane, is a membrane that will allow certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion." The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Depending on the membrane and the solute, permeability may depend on solute size, solubility, properties, or chemistry. An example of a semi-permeable membrane is a lipid bilayer, on which is based the plasma membrane that surrounds all biological cells. Many natural and synthetic materials thicker than a membrane are also semipermeable. An example of this is the thin film on the inside of an egg.]

the measure of how much of a given substance there is mixed with another substance. This can apply to any sort of chemical mixture, but most frequently the concept is limited to homogeneous solutions, where it refers to the amount of solute in a substance.

The term synthesis is used in many fields, usually to mean a process which combines together two or more pre-existing elements resulting in the formation of something new. Example: [1]Photosynthesis, the conversion of light energy into chemical energy by living organisms.[2]DNA replication occurs during the S phase (Synthesis phase) of the cell cycle.

the property to regulate the internal environment of the body so as to maintain a stable, constant condition.

Prokaryotic cells differ significantly from eukaryotic cells. They don't have a membrane-bound nucleus and instead of having chromosomal DNA, their genetic information is in a circular loop called a plasmid. Bacterial cells are very small, roughly the size of an animal mitochondrion (about 1-2µm in diameter and 10 µm long). Prokaryotic cells feature three major shapes: rod shaped, spherical, and spiral. Instead of going through elaborate replication processes like eukaryotes, bacterial cells divide by binary fission.

A group of phospholipids (consisting of a phosphate head and 2 fatty-acid tails) arranged into a double-layer, with the hydrophilic phosphate heads exposed to the water content outside and within the cell and the hydrophobic fatty-acid tails hidden in the inside.

[The phospholipid bilayer is the most permeable to small, uncharged solutes. Protein channels float through the phospholipids, and, collectively, this model is known as the fluid mosaic model.]

Animals, plants, fungi, and protists are eukaryotes, organisms whose cells are organized into complex structures enclosed within membranes. The defining membrane-bound structure which differentiates eukaryotic cells from prokaryotic cells is the nucleus. Many eukaryotic cells contain other membrane-bound organelles such as mitochondria, chloroplasts and Golgi bodies.

The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer") is a selectively permeable lipid bilayer found in all cells.[1] It contains a wide variety of biological molecules, primarily proteins and lipids, which are involved in a vast array of cellular processes such as cell adhesion, ion channel conductance and cell signaling. The plasma membrane also serves as the attachment point for both the intracellular cytoskeleton and, if present, the cell wall. [2]Membranes are vital because they separate the cell from the outside world. They also separate compartments inside the cell to protect important processes and events.