The main principles of the Cell theory. Prokaryotes and eukaryotesBiology/topic 2-3

The first steps in study of cells

he history of the discovery and study of cells connected with the invention and an improvement of the microscope. Cell was opened in 1665 by Robert Hooke, who described the cell walls of cork. Levenguk first observed the single-celled organisms. Purkinje described the internal contents of the cell - the protoplasm. R.Broun opened the nucleus.

The wacky history of cell theory

In 1839 zoologist T. Schwann used the data (information) of botanist M. Schleiden formulated the basic position of the Cell theory:

1. All living organisms are composed of cells;

2. Cells of animals and plant similar in structure and chemical composition.

3. German Virchow added to the Cell theory position: Each cell is formed by division of the mother cell.

Modern cell theory includes the following statements:• 1) The cell - the smallest structural and

functional unit of life.• 2) The cells of all living organisms are

similar in structure and chemical composition, metabolic processes and the most important manifestations of life.

• 3) The new cells are formed by the division of the mother cell.

• 4) The cells of multicellular organisms are specialized by function and form tissues, which make up the organs.

•The study of cells is important for the development of science and medicine in particular. So, in many diseases are affected cells, and knowledge of the mechanisms of cell division, of metabolic processes in the cell will allow to develop new methods of treatment of these diseases.

Live organisms

Prokaryotes Eukaryotes

What is prokaryotes?Cells without nucleuspro - "before“Karyon - "nut or kernel"

Prokaryotes - is organisms, cells of which do not have a nucleus, they lack a membrane-bound nucleus (karyon). They include bacteria and cyanobacterias.

Cell structure of a bacterium, a member of one of the two domains of prokaryotic life

Cells without nucleuspro - "before“Karyon - "nut or kernel"

Diagram of a cyanobacterium.

What is eukaryotes?Cells with nucleuseu - “true“Karyon - "nut or kernel"

Eukaryotes - are organisms whose cells have a nucleus, demarcated from the cytoplasm by nuclear membrane. Eukaryotes include all animals, plants and fungi.

A typical animal cellA typical animal cell

Similarities and differences of prokaryotes and eukaryotes cellsFeatures Prokaryotes Eukaryotes

Nucleus

Nucleoid

DNA molecule

Мosaic structure of DNA

Ribosomes

Мembranous organelles

Cytocentrum

Мezosomy

Cell size

Cell division

Similarities and differences of prokaryotes and eukaryotes cellsFeatures Prokaryotes Eukaryotes

Nucleus - +

Nucleoid + -

DNA molecule forms a ring divided into fragments

Мosaic structure of DNA - +

Ribosomes + +

Мembranous organelles - +

Cytocentrum - +

Мezosomy + -

Cell size small (0,2-10 мкм) big (10-100 мкм)

Cell division direct binary division mitosis, meiosis

The main features of prokaryotes:

1) no nucleus; instead nucleus is nucleoid (equivalent of nucleus) devoid of the nuclear membrane and consisting of a DNA molecule in the form of a ring; 2) there are no organelles with the membrane structure; 3) have mezosomy (invagination of plasma membrane) that function as membrane organelles; 4) characteristically by simple binary division.

The main features of eukaryotes:

1) DNA-associated with proteins - histone and forms the chromatin which at the division of cells is transformed into chromosomes;2) DNA have a mosaic structure (between the genes are uninformative areas – spacers; in genes are exons - informative sites and introns - non-informative sites);3) have all cytoplasmic organelles with the membrane and non-membrane structure;4) eukaryotic cells divide by mitosis, meiosis.

Recap quiz: What are Prokaryotes? What are Eukaryotes? What kind of Prokaryotes do you know? What kind of Eukaryotes do you know? Who first did enter the term “nucleus”? Who did formulate the cell theory ? What is Homeostasis? What statements does Modern cell theory

include? What is the difference between the Prokaryot

and Eukaryot cells? What is the similarity between the Prokaryot

and Eukaryot cells?

Home task:•Learn definitions which you wrote on the lesson

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