Cell Structure and Nucleus of Eukaryotic Cells

Eucaryotic Cell Structure

• The cell membrane is composed of proteins and phospholipids, separating the cell from the outside and regulating the passage of nutrients and waste with selective permeability.

The Eucaryotic Nucleus

• The nucleus is the "command center" of the cell, controlling all cellular functions.
• It consists of three components: nucleoplasm (gelatinous matrix), chromosomes, and a nuclear membrane with holes.
• Chromosomes are embedded in the nucleoplasm, consisting of linear DNA molecules and proteins (histones).
• Genes are located along chromosomes, with each gene containing information to produce one or more gene products (usually proteins).
• The human genome consists of between 20,000 and 30,000 genes.

Eucaryotic Nucleus, cont.

• Although most genes code for proteins, some code for two types of ribonucleic acid (RNA): ribosomal RNA (rRNA) and transfer RNA (tRNA).
• The number and composition of chromosomes and the number of genes on each chromosome are characteristic of a particular species of organism.
• Human diploid cells have 46 chromosomes (23 pairs).

Cell Structure and Taxonomy

• The cell is the fundamental unit of any living organism, exhibiting the basic characteristics of life (obtaining nutrients, metabolism, mutation).
• Cytology is the study of the structure and function of the cell.
• There are two categories of cells: eucaryotic and procaryotic.

Acellular and Cellular Microbes

• Eucaryotic cells contain a "true" nucleus, whereas procaryotic cells do not.
• Eucaryotic cells possess a complex system of membranes and membrane-bound organelles, whereas procaryotic cells do not.
• Both eucaryotic and procaryotic cells possess a cell membrane with selective permeability.

Procaryotic Cell Structure

• Procaryotic cells are about 10 times smaller than eucaryotic cells.
• Procaryotic cells are simple compared to eucaryotic cells and reproduce by binary fission.
• All bacteria are procaryotes, as are archaea.
• The cytoplasm of procaryotic cells is not filled with internal membranes.

Procaryotic Cell

• The cytoplasm of procaryotic cells is surrounded by a cell membrane, a cell wall (usually), and sometimes a capsule or slime layer.
• The cell membrane is similar in structure and function to the eucaryotic cell membrane, being selectively permeable and flexible.