J a v a d J a m s h i d i

F a s a U n i v e r s i t y o f M e d i c a l S c i e n c e s

An Introduction to

Cellular & Molecular Biology

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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.

How old are we?!

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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

The Biology

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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.

The Biology cont.

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From Atoms to Organism

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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)

The Molecules of Life

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ATP Energy Transfer

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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)

Cell Macromolecules

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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.

Proteins

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Proteins have a variety of functions in the cell:

Enzymes

Structural proteins

Cell signaling and ligand binding

Proteins Functions

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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 20400 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 10-9 g

protein 20 percent of a cell 's weight 7X 10-10 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 109

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

Proteins Functions cont.

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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

Nucleic Acids

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DNA strands are composed of monomers called nucleotides

Nucleic Acids cont.

Pentose

Nitrogenous base

Phosphate group

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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 5000.

Humans and other metazoans have between 13,000 and 23,000, while many plants like Arabidopsis have more

Nucleic Acids cont.

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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,

Polysaccharides

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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.

Cellular Membranes

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Cellular Membranes

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The biological universe consists of two types of cells

Prokaryotic Lack a defined nucleusHave a relatively simple internal organizationInclude two kingdoms: the eubacteria (true bacteria) and archaea.

EukaryoticContain a defined membrane-bound nucleus Extensive internal membranes that enclose the organellesInclude four kingdoms: the plants, animals, fungi, and protists.

Cell Types

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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

Prokaryotes

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Prokaryotic cell

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Comprise all members of the plant and animal kingdoms, as well as fungi and protozoans

Eukaryotic cells are commonly about 10-100 μm,

Most eukaryotic contain organelles, which are separated from the cytoplasm by membranes.

Each type of organelle contains a collection of specific proteins,

Eukaryotic Cells

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Eukaryotic Cell

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How Eukaryotic Cells evolved

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DNA Is Packaged Within Chromosomes

Image From: The University of Waikato | http://www.sciencelearn.org.nz

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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.

Cell-Cell and Cell Matrix Adhesions

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Cell-Cell and Cell Matrix Junctions

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Cell Cycle

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

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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

Embryonic Development