Javad Jamshidi Fasa University of Medical Sciences

2 The age of the universe is about 13.8 billion years The age of the Earth is 4.54 million years 3.6 billion years ago, simple cells (prokaryotes) 2 billion years ago, complex cells (eukaryotes) 1 billion years ago, multicellular life 200 million years ago, mammals 2.5 million years ago, the genus Homo (human predecessors) 200,000 years ago, anatomically modern humans.

3 Forms and structures of the living world today are the results of billion of years of evolution Natural selection All biological systems are composed of the same types of molecules and employ similar organization at the cellular level. Genes (DNA), ultimately define biological structure and maintain the integration of cellular function

4 Many genes encode proteins, the primary molecules that make up cell structures and carry out cellular activities. Mutations, provide the random variation The last common ancestor of all life on earth was a cell All cells use the same molecular building blocks, similar methods for metabolism and activity.

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6 Water, inorganic ions, and a wide array of relatively small organic molecules account for 75 to 80 percent of living matter by weight These small molecules are imported into the cell or synthesized within the cell. The footprint of evolution in the structures of many small molecules An important and universally conserved small molecule is adenosine triphosphate (ATP)

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8 Certain small molecules (monomers) can be joined to form polymers, also called macromolecules Cells produce three types of large macromolecules: Proteins Nucleic Acids Polysaccharides (Carbohydrates)

9 Proteins, are the most abundant and functionally versatile of the cellular macromolecules. Cells string together 20 different amino acids in a linear, commonly range in length from 100 to 1000 amino acids Linear chain of amino acids folds into a complex shape, conferring a distinctive three-dimensional structure and function on each protein Humans obtain amino acids either by synthesizing them from other molecules or by breaking down proteins that we eat.

10 Proteins have a variety of functions in the cell: Enzymes Structural proteins Cell signaling and ligand binding

11 How can 20 amino acids form all the different proteins needed to perform these varied tasks? A "typical" protein is about 400 amino acids long, there are possible different amino acid sequences. How many protein molecules a cell needs to operate and maintain itself? Take a typical eukaryotic cell: the cell would weigh 3.5X g protein 20 percent of a cell 's weight 7X g. The average protein has a molecular weight of 52,700 g/mol Total number of protein molecules per cell is about 7.9 X 10 9 Consider that a liver cell contains about 10,000 different proteins; thus each cell would on average contain close to a million molecules of each type of protein

12 It’s functional properties make it the cell's "master molecule.“ The three-dimensional structure of DNA, first proposed 60 years ago The double-helical structure of DNA, is critical to the phenomenon of heredity

13 DNA strands are composed of monomers called nucleotides Pentose Nitrogenous base Phosphate group

14 The genetic information carried by DNA resides in its sequence Specific segments of DNA, termed genes, carry instructions for making specific proteins Most bacteria have a few thousand genes; yeasts and other unicellular eukaryotes have about Humans and other metazoans have between 13,000 and 23,000, while many plants like Arabidopsis have more

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16 Polymeric carbohydrate molecules composed of long chains of monosaccharide units Homopolysaccharides contain only a single type of monomer; some serve as storage forms of monosaccharides, starch and glycogen. Other homopolysaccharides (cellulose and chitin) heteropolysaccharides contain two or more different Provide extracellular support for organisms of all kingdoms. For example, the peptidoglycan,

17 Plasma membrane, prevents the free flow of molecules in and out Phospholipids are the conserved building blocks of all cellular membranes Smaller amounts of other lipids, such as cholesterol, are inserted into the phospholipid framework.

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19 The biological universe consists of two types of cells Prokaryotic Lack a defined nucleus Have a relatively simple internal organization Include two kingdoms: the eubacteria (true bacteria) and archaea. Eukaryotic Contain a defined membrane-bound nucleus Extensive internal membranes that enclose the organelles Include four kingdoms: the plants, animals, fungi, and protists.

20 Eubacteria, arc single-celled organisms; included are the cyanobacteria, or blue-green algae, which can be unicellular or filamentous chains of cells Commonly 1-2 μm. Bacterial cells possess a cell wall composed of layers of peptidoglycan, a complex of proteins and oligosaccharides Many archacans grow in unusual, often extreme, environments

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22 Comprise all members of the plant and animal kingdoms, as well as fungi and protozoans Eukaryotic cells are commonly about μm, Most eukaryotic contain organelles, which are separated from the cytoplasm by membranes. Each type of organelle contains a collection of specific proteins,

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25 Image From: The University of Waikato |

26 To became a multicellular organism, cells have to stay together Animal cells are often "glued" together by cell-adhesion proteins (often called cell adhesion molecules, or CAMs) on their surface Some CAMs bind cells to one another; other types bind cells to the extracellular matrix, forming a cohesive unit.

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28 Image From: Lodish, Molecular Cell Biology 7e. 2013

29 The human body consists of some 100 trillion cells, yet it develops from a single cell, the zygote, resulting from fusion of a sperm and an egg. The early stages in the development of an embryo are characterized by rapid cell division and the differentiation of cells into tissues. The embryonic body plan, the spatial pattern of cell types (tissues) and body parts, emerges from two influences: a program of genes that specify the pattern of the body, and local cell interactions