Cellular Biology School of Life Sciences Shaanxi Normal University
CHAPTER 1 CELLULAR BIOLOGY AND CELLS
Introduction Molecular Biology and Molecular Genetics The fast developed branches of modern biology Cellular Biology Immunology and Molecular Immunology
II. Properties of cells Before longer than 80 years ago, Wilson said that every key problem can be discovered in cells! CELL 1. Most basic and smallest unit to exhibit life, and life is the most basic property of cells. 2. Can be cultured in vitro where they will grow and reproduce for extended periods of time. 3. Can renew and expand themselves in vivo under exact regulation by their community. The first culture of human cells was begun by George Gey of Johns Hopkins University in 1951, and that was named as Hela cell from human malignant tumor because the donor’s name is Henrrietta Lacks. Hela cells are still used in many labs now in the world. The cell culture in vitro has become an essential tool of cellular or molecular biologists. Cell culture in vitro is so important that if you can not do it you can not do any life research almost!
Dimensions of some example cells. 1 mm = 10−3 m; 1 μm = 10−6 m; 1 nm = 10−9 m
Two Fundamentally Different Classes of Cells Human cells Animal cells Eukaryotic CellsParasite or parasite cells (Protozoa) Plant cells Fungi Acidophiles Cells ArchaebacteriaMenthanogens (Extremophiles)Halophiles Thermophiles Prokaryotic CellsBacteria Mycoplasts* EubacteriaRickettsia Chlamydia Others *Mycoplast is the smallest cell type in the world.
Differences Between Prokaryotic and Eukaryotic Cells AThe tiny chromosomes of mitochondria and chloroplasts are exceptions; like prokaryotic chromosomes they are often circular. BThe S value, or Svedberg unit, is a sedimentation rate. It is a measure of how fast a molecule moves in a gravitational field, and therefore in an ultracentrifuge.
Basic Properties of Cells • Structural properties of cells: • Cells are highly complex and organized • Cells have membrane with specific permeability, dialysis, or penetration • Cells have genetic substance (DNA/RNA) • Cells have ribosome (For protein synthesis) • Functional properties of cells: • Cells possess a genetic program and the means to use it (Heritance). Human genetic program contains enough information, if converted to words, to fill millions of pages of text.But the information is packaged into the space of a cell nucleus —— thousands of times smaller than the dot on this i. • Cells are capable of producing more of themselves (Proliferation). • Cells acquire and utilize materials and energy for every function. • Cells carry out a variety of chemical reactions. Enzyme, Reaction, Metabolism • Cells engage in numerous mechanical activities: Mobility, changes in shapes. • Cells are able to respond to stimuli. • Cells are capable of self-regulation for maintaining a complex, ordered state.
Morphological properties of cells: Cells are very variable in size and shape. Cells have highly complex and ordered parts inside.
The Chemical Basis of Life (Molecular Basis of Cells) The chemical components of a cell (Bacterial cell) Components Ratio to the cell weight (%) Water 70 Salts 1 Sugar and their precursors 1 Amino acids and their precursors 0.4 Nucleotides and their precursors 0.4 Fatty acids and their precursors 1 Other small molecules 0.2 Big molecules (Proteins, Nuclear acids, Polysaccharides) 26
The basic components of a cell includes O, C, H, N, Si, K, Ca, P and Mg. the ratio of O, C, H and N is over 90 percent of the cell weight. All components can be divided into two parts as organics and inorganics. • Water: The importance of water to cells can not be evaluated enough anyhow: • Resolve salts and proteins for forming a reaction system • Regulate temperature • Participate in enzyme reactions • Participate in metabolism • Maintain the cell structure • Maintain the cell function • Free water • Water in cell • Combined with protein (4.5%)
Covalent bonds The molecule of water is polarized, with partial negative charge on the oxygen and partial positive charges on the two hydrogens
Salts: • Roles of the Salts in Cells • Components of the cell structure: C, H, N, O, P and S. • Necessary to the enzyme reactions: Ca2+, Cu2+, Mg2+, K+, Na+ and Cl-. • Necessary to the enzyme activities: Co2+, Cu2+, Fe3+, Mn2+ and Zn2+. • Maintaining the pH and osmotic pressure in cells. • The proteins or lipids that combined with some salts are necessary to some special cell functions.
Cl Cl Chlorine gas consists of two chlorine atoms, each of which consists of a positively charged nucleus surrounded by negatively charged electrons. Like oxygen, chlorine atoms tend to accept electrons when they become available, but the battle is equal in the chlorine molecule: The two atoms share their electrons equally and the molecule is non-polar
Ionic compounds will dissolve only in polar solvents. The solutions are formed as the result of the interaction between the polar molecules and non-polar molecules: Acids are molecules that give H+ to water. Bases are molecules that take H+ from water.
Four types of important organic molecules and biological macromolecules: • Sugars • Carbohydrates—sugars and the macromolecules built from them—have many different roles in cells and organisms. All carbohydrates are formed from the simple sugars called monosaccharides or glucose. • Sugars: Monosaccharide (Glycose, Glucose, Monosaccharose), Simple sugars (Disaccharide, Disaccharose, Oligosaccharide, Oligosaccharose), Polysaccharide (Polysaccharose, Polyose). • Glucose is the basic energy provider to cells by serial oxygenic reactions to release energy, water and CO2, and basic molecule component to polysaccharose. • Polysaccharose is big bio molecule involved with cell structure, immunity (Antigen or semi-antigen), nutrition and others.
Cellulose Membrane component Structural polysaccharose Chitin Polysaccharose Starch (Plant cell) Nutritive storage polysaccharose Glycogen (Animal cell)
2. Proteins Generally, proteins are the macromolecules composed by amino acids that carry out virtually all of a cell’s activities; they are the molecular tools and machines that make things happen. It is estimated that a typical mammalian cell may have as many as 10,000 different proteins having a diverse array of functions. Proteins in cell can play roles as enzyme, structural cables, hormones, antibodies, antigens, cytokines, gene activators, transmitters, receptor, toxins and many others. So, “The nature of life is protein, the property of life is motility, and the motility is the essential of protein” is well known as a phrase.
Structure of protein: Proteins are capable of such a wide variety of activities because they can exhibit such a great variety of structures. Proteins have shapes that allow them to interact selectively with other molecules. Proteins, in other words, exhibit a high degree of specificity. Proteins have four grades of structure shown as the following fig:
Primary structure:Polypeptide sequence composed of 20 amino acids by peptide bond Secondary structure:Polypeptide chain forms the α-helix and β-pleated sheet by hydrogen bonds Tertiary structure: The conformation of the entire protein. Tertiary structure is unlimitedly stabilized by an array of noncovalent bonds between the diverse side chains of the protein. In results, the function domains or motifs are formed. Quaternary structure:Some proteins are composed of only one polypeptide chain, such as myoglobin. But most are made up of more than one chain, or subunits. It is called as quaternary structure that the subunits linked together often by noncovalent bonds between hydrophobic “patches” on the complementary surface of neighboring polypeptides.
3. Lipids Lipids of importance in cellular function include fats, steroids, and phospholipids. Fats: Fats consist of a glycerol molecule linked by ester bonds to three fatty acids forming triglyceride.
Steroids: One of the most important steroids is cholesterol, a component of animal cell membranes and a precursor for the synthesis of a number of steroid hormones. Cholesterol is largely absent from plant cells, that is why vegetable oils are considered “cholesterol free”. Phospholipids: Phospholipids contain two ends: The end containing the phosphate group has a distinctly hydrophilic character; the other end composed of the two fatty acid tails has a distinctly hydrophobic character. Based on the characters above, phospholipids are the basic components of bio membranes, and also, they participate in cell metabolism.
4. Nucleic acids Components of nucleic acids Nucleosides Nucleotides Adenine (A) Adenosine monophosphate (AMP) Deoxygenated adenosine monophosphate (dAMP) Guanine (G) Guanine monophosphate (GMP) Deoxygenated guanine monophosphate (dGMP) Thymine (T) Deoxygenated thymine monophosphate (dTMP) Cytosine (C) Cytosine monophosphate (CMP) Deoxygenated cytosine monophosphate (dCMP) Uracil (U) Uracil monophosphate (UMP)
The nucleotides triphosphate used to synthesize DNA are as the follows: Deoxygenated adenosine triphosphate (dATP) Deoxygenated guanine triphosphate (dGTP) Deoxygenated thymine triphosphate (dTTP) Deoxygenated cytosine triphosphate (dCTP) Denaturation: The step by that the closed DNA helixes is opened and separated. Melting temperature (Tm): The temperature that makes DNA denaturated. The higher G+C ratio, the higher Tm. The higher A+T ratio, the lower Tm. Renaturation or annealing: The procedure by that the opened DNA double strands assemble together. So, the steps of a Polymerase Chain Reaction (PCR) should be denaturation, annealing and extension.
III. Viruses • Not cellular organism • Smallest organism in the world • Parasite in cells • Simplest organisms that contain nucleic acids inside only • Simplest life cycle that shows nucleic acids replication only • Usually, viruses are very harmful to humans, animals and plants
DNA viruses RNA viruses Viruses Phages Reverse transcription viruses (RT-viruses) Tumor viruses (Oncoviruses)