Biology

1665; Published the book, "Micrographia" in which he gave about 60 observations about the cells in detail using a compound microscope.

1665; He coined the term ‘cell’.

1674; Discovery of the existence of single-cell organisms. Upon examining pond water, he observed dozens of protists, which he called 'animalcules' as well as spirogyra (green algae).

1838; 1) All organisms are made up of cells. 2) Cells are the basic units of life. He made these conclusions after comparing observations of plant and animal cells.

1839; Proposed The Classical Cell Theory. It implied that this relationship was a specific and lawful one, i.e. that germs of a certain kind, all else being equal, would produce adult organisms of the same kind, and vice versa.

The Cell Theory

1855; Proposed that new cells are formed only from cells that already exist. "Omnis cellula e cellula*". Proposed the more recent version of the Cell Theory.

The smallest structural unit of an organism that is capable of independent functioning.

It is composed of a nucleus, cytoplasm and various organelles surrounded by a selectively permeable membrane.

Major Structural Features of Eukaryotic Cells

It provides different local environments that facilitate the occurence of complex metabolic reactions or even incompatible processes, simultaneously and in the correct sequence within the same cell.

Also known as the 'cell membrane' defines the boundary of the cell and retain its contents.

Houses the DNA that directs cellular activities.

Where various cellular functions are localized.

The semi-fluid substance in which all the organelles are suspended. Fits between the nucleus and cell membrane and consists mainly of water excluding the organelles in it.

Cytoplasmic Organelles

Make up protists (unicellular organisms which include protozoa), fungi, plants and animals. Has no plasmids.

They have a true Nucleus that houses their DNA and contain numerous membrane-bound organelles where multiple biochemical processes can occur simultaneously and independetly.

A small, circular, double-stranded DNA molecule that is distinct from a cell's chromosomal DNA.

An example of which would be bacteria and archaebacteria.

Have a single compartment enclosed by a cell membrane. They lack true nuclei and all the cell components such as DNA, RNA, ribosomes and other molecules are not separated from each other in the cell's interior.

Endoplasmic Reticulum

Cytoplasmic Inclusions

Tabular and non-granular structure due to the absence of ribosomes. It manufactures and metabolizes lipids. It also facilitates in the break down of drugs and alcohols.

Has the presence of ribosomes. It is the site of protein synthesis. It is in charge of the folding, quality control and dispatch of proteins.

Processing, packaging and sorting of secretory material for use within and outside the cell.

It is the powerhouse the cell. It contains enzymes—chemical oxidation of food molecules and produces energy in ATP (Adenosine Triphosphate).

Small spherical membrane-bound organelles which contain a number of enzymes
for intracellular digestion.

Thin barrier that forms a boundary between separating an individual cell from the external environment.

A small structure within a cell, consisting of fluid enclosed by a lipid bilayer. They form naturally during the processes of secretion*, uptake** and transport of materials within the cytoplasm.

An energy-consuming process that expels secretory vesicles containing nanoparticles (or other chemicals) out of the cell membranes into the extracellular space.

A cellular process for ingesting and eliminating particles larger than 0.5 μm in diameter, including microorganisms, foreign substances, and apoptotic cells. It is found in many types of cells and it is, in consequence an essential process for tissue homeostasis.

Are specialized for carrying out oxidative reactions using molecular oxygen. They generate hydrogen peroxide, which they use for oxidative purposes—destroying the excess by means of the catalase they contain.

Are protein factories of the cell. They can be found in the Rough ER and they synthesize protein molecules.

Small dense region of cytoplasm that serves as the main microtubule organizing center.

A network of protein fibers that support the shape of the cell and anchors organelles to fixed locations.

Are long slender protein tubes. They form the cytoskeleton of the cell.

The storehouse of DNA inside the cell. Protects the DNA at all times.

Nucleus includes

Can be found in PLANT CELLS only:

A two-layered outer limit of the nucleus separating it from the cytoplasm.

Responsible for ribosome formation.

Selective channels between the cytoplasm and the inside of the nucleus. Allows molecules which contain the correct localization signal to pass in and out.

Made up of DNA and proteins and form chromosomes during cell division.

Contains the genes inherited by the offspring from their parents.

Its main component is cellulose. It provides structural support and gives the plant its rigid shape.

Cell wall has:

Forms during the growth period of the cell.

Forms when the growth of the cell ceases.

Large and more centrally located in the plant cell. Store enzymes and waste products.

are double-membrane organelles that are responsible for manufacturing and storing of food. These often contain pigments that are used in photosynthesis.

Tissues

Are co-axial membranous channels that cross walls of adjacent plant cells, linking the cytoplasm, plasma membranes and ER of cells and allowing direct cytoplasmic cell-to-cell communication of both small molecules and macromolecules.

Covers all body surfaces, lines body cavities and hollow organs and the major
tissue in glands. Closely packed, flat cells with very little intercellular space and only a small amount of intercellular substance. Does not contain blood vessels.

Intercellular junctions that attach EPITHELIAL TISSUES:

When there is anchoring of the cytoskeleton of one cell to another.

type of junction that prevents leaking.

Communication between cells.

Helps in the breakdown of alcohol.

Types of Epithelial Tissues

Type of epithelial tissue that is only one cell thick

Type of epithelial tissue that is two or more cells thick

Type of epithelial tissue that is composed of a single layer of cells that are of different sizes.

Shapes of Epithelial Tissues

Shape of epithelial tissue that lines the lungs, capillary walls and blood
vessels. It forms membrane that allows selective diffusion of materials to pass through. It is flat.

Shape of epithelial tissue that lines the kidney tubules and absorbs molecules. It is a cube shape.

Shape of epithelial tissue that lines the trachea and aids in movement of mucus. It is shaped like alternating strata.

Shape of epithelial tissue that lines the small intestine. Its primary functions: secretion, excretion, and absorption. It is shaped like columns.

How does epithelial tissue renew?

Binds structure together. It also forms a framework and support for organs and the body as a whole. Additionally, it helps repair damaged tissues.

Types of Connective tissue

It provides flexibility, shock absorption, and reduction of friction on load bearing surfaces. These can be mostly seen in joints.