Biology

Matthias Schleiden

1838- made a careful study of plant issues and develop the first statement of the cell theory

Theodor Schwann

1839-reported that all animal issues also consist of individual cells

Robert Hooke and Anton van leeuwenhoek

used glass lenses to magnify small cells and cause them to appeal larger than the 100 micrometer limit imposed by the human eye

Robert brown

1831- called it the nucleus plural, nucleic from the latin word for kernel

cell surfaces in animals

• extracellular matrix

• junctions

• cytoskeleton

junctions between animal cells

• adhesion junctions

• tight junctions

• gap junctions

permeability of the plasma membrane

• channel protein

• carrier protein

• vesicle

how solutes create osmotic pressure

• isotonic solution

• hypotonic solution

• hypertonic solution

maintaining osmotic balance

• extrusion

• isosmotic solutions

• turgor pressure

bulk passage into and out of cells

• endocytosis

• exocytosis

forms of endocyosis

• phagocytosis

• pinocytosis

• receptor mediated endocytosis

cell size

• cube

• volume

• surface area

protein fiber

• microfilaments actin filaments

• microtubules

• intermediate filaments

the idea that all organisms are composed of cells is called the cell theory

• all organisms are composed of one or more cells, within which the processes of life occur

• cells are the smallest living things. nothing smaller than a cell is considered alive

• cells arise only by division of a previously existing. although life likely evolved spontaneously in the environment of the early earth, biologists have concluded that no additional cells are originating spontaneously at present. rather, life on earth represents a continuous line of descent from those early cell

why are most cells so tiny?

most cells are small because larger do not function as efficiently. in the center of every cell is a command center that must issue orders to all parts of the cell, directing the synthesis of certain enzymes, the entry of ions and molecules from the exterior, the assembly of the new cell parts

• these orders must pass from the core to all parts of the cell, and it takes them a very long time to reach the periphery of a large cell. for this reason, an organism made up of relatively small cells is at an advantage over one composed of larger cells

for this reason, an organism made up of relatively small cells is at an advantage over one composed of larger cells

surface-to-volume ratio

as cell size increases, volume grows much more rapidly than surface area. for a round cell, surface area increases at the square of the diameter, whereas its volume increases as the cube.

• to visualize this, consider the two single cells in

  • the large cell to the rights 10 times bigger than the small cell, but while its surface area is 100 times greater 10(2), its volume is 1,000 times 10(2) the volume of the smaller cell

a cell’s surface provides the interior’s only opportunity to interact the environment, with substances passing into and out of the cell across its surface. large cells have far less surface for each units of volume than do small ones

an overview of cell strcute

all cells are surrounded by a delicate membrane, called a plasma membrane that controls the permeability of the cell of water and dissolved substances.

• a semifluid matrix called cytoplasm fills the interior of the cell. it used to be thought that the cytoplasm was uniform, like jello, but we now know that it is highly organized

resolution