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These lecture notes provide a comprehensive introduction to cell biology, covering fundamental concepts such as the definition and characteristics of cells, the history of cell discovery, and the cell theory. The notes delve into the structure of prokaryotic and eukaryotic cells, exploring key organelles and their functions. Additionally, they discuss the chemical bonds that hold biological macromolecules together, including ionic, covalent, hydrogen, and van der waals bonds. The notes also cover acids and bases, reactive organic molecules, and carbohydrates, providing a solid foundation for understanding the building blocks of life.
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Cell Biology Lecture Notes Introduction: A. Definition of a cell : fundamental structural and functional unit of all living organisms B. Characteristics of cells :
G) 1889- R.Altman -purified nucleic acids H) 1944- Oswald Avery , Colin MacLeod, and MacLyn McCarty- -Demonstrated that DNA was the heredity molecule -DNA could transform bacterial cells I) 1952-Alfred Hershey and Martha Chase -also demonstrated that DNA was the heredity molecule -Radioactive DNA from a virus was able to infect and transform bacterial cells J) 1953-James Watson and Francis Crick -developed the 3-D structure of DNA
L) 1961- Brenner, Jacob, Meselson -discovered RNA M) 1966- Nirenberg and Khorana -elucidated the chemical nature of the genetic code N) 1972-1973- Berg, Boyer, and Cohen - discovered gene cloning O) 1975- Gilbert and Sanger -developed chemical techniques to rapidly sequence DNA Cell Structure: I. Most cells are microscopic and cannot be seen by the naked eye. II. Microscopes were developed to visualize cells. III. Resolution is the minimum distance where 2 objects can be visually separated -Unresolved -Partially resolved -Resolved -Depends on: a. Wavelength of light b. Refractive index of the medium c. Of the light -The naked eye can resolve two separate objects separated by 200 um Metric system: -1 meter = 3.3 feet, 1 km = 10^3 m, 1cm = 10-2^ m, 1mm = 10-3^ m, 1um = 10-6^ m, 1nm = 10-9^ m, 1 A = 10-10^ m, 1pm = 10 -12^ m
Eukaryotic Cell - (eu=true karyon=nucleus)
Function
s in the breakdo wn of fats attached to the rough ER in the Golgi complex a. Golgi apparatus-a membranous organelle that packages and sorts newly synthesized secretory proteins a. Lysosome- organelle which contains digestive enzymes e. Mitochondrion-semiautonomous eukaryotic cell organelle -Site of respiration -Consists of an outer membrane and a convoluted inner membrane -Site of ATP production within the cell a. Microbody-organelle within a cell containing specialized enzymes whose functions involve hydrogen peroxide (peroxisome) b. Microtubules-composed of tubulin h. Microfilaments-composed of actin -Both (g and h) are involved in cellular movement a. Intercellular-includes flagella and cilia b. Intracellular- cytoplasmic streaming Plant cell organelles : -Chloroplast- involved in photosynthesis -Central vacuole- provides support to the plant via osmotic pressure -Cell wall- composed of cellulose, which provides extra strength and rigidity i. Specialized protozoan cell organelle: -Contractile vacuole- used to maintain proper osmotic pressure and secretes waste and excess H 2 O -Two types of nuclei
Reactive Organic Molecules:
E. Disaccharide = 2 monosaccharide subunits linked together -Ex: maltose = 2 glucose molecules linked together -Glycosidic bond = is the bond between 2 carbohydrate subunits formed by the eliminated of water F. Examples of Polysaccharides:
-A nonpolar side chain is attached at one end of the ring structure and a polar side group is attached to the opposite end of the ring structure -R’ is a polar unit and R is a nonpolar unit -The combination of polar and nonpolar side groups gives phospholipids dual solubility properties -An example of a sterol is cholesterol -Cholesterol is an important component of the cell membrane in all animal cells -Cholesterol also can be deposited inside arteries causing blockage, which contributes to the disease arteriosclerosis (hardening of the arteries) -Hormones are steroids and they play major roles in cell regulation, cell metabolism, and cell growth I. Proteins carry out many cellular functions:
-Peptide bond - is a bond in which the carboxyl group of one amino acid is joined to the amino group of a second amino acid via a condensation reaction -Peptide - is a chain composed of 2 or more amino acids and contains one or more peptide bonds -Ex: dipeptide = chain composed of 2 amino acids -Tripeptide = chain composed of 3 amino acids -Polypeptide is an amino acid chain composed of 3 or more amino acids -The amino acid sequence of a polypeptide chain is called the primary structure of a protein E. Secondary structure of proteins - is the conformation imposed on the polypeptide chain by hydrogen bonding between amino acids
6-aminopurine (adenine) 2-amino-6-hydroxypurine (guanine)
5’-dTMP = deoxythymidine-5’-PO 4 5’-dCMP = deoxycytidine-5’-PO 4 VI. Nomenclature of nucleotides in RNA base - ribose - phosphate 5’-AMP = adenosine-5’- PO 4 5’-GMP = guanosine-5’- PO 4 5’-UMP = uridine-5’- PO 4 5’-CMP = cytidine-5’- PO 4 VII. Nomenclature of nucleoside triphosphates ATP = adenosine-5’-triphosphate dATP = deoxyadenosine-5’-triphosphate VIII. Nucleic acids RNA and DNA -Nucleotides held in chains by bridging a phosphate group that extends between the 5’-carbon of one sugar with the 3’-carbon of a second sugar (held together by a phosphodiester bond) -Produces a backbone chain of alternating sugar and PO 4 groups -DNA exists in a double helix that contains 2 intertwined chains of nucleotides -RNA is single-stranded Enzymes:
-Enzymes are specific in their activity; each enzyme catalyzes the reaction of a single type of molecule or a group of closely related molecules -Enzymes are saturated by high substrate concentrations -Many enzymes contain nonprotein groups called cofactors -Inorganic cofactors = metal ions -Organic cofactors = coenzymes (ex: vitamins) I. Activation energy: the energy in excess of the ground state that must be added to a molecular system to allow a chemical reaction to start (e.g. rock on a cliff must be pushed to roll down the hill) -One way to supply energy is to heat the reactants -Second way is to add a catalyst -Catalyst forms a complex with the reactant, thus bringing the reactants closer together so they can react -In biological systems a catalyst is called an enzyme, which lowers the activation energy of the system -Graph: II. Three enzymatic mechanisms which can contribute to the formation of a transition state is a catalyzed biological reaction a) Enzyme brings reacting molecules into close proximity b) Enzyme orients reactants into positions to induce favorable interactions c) Enzymes alter the chemical environment of the reactants to promote interaction -E.g. is to create a nonpolar environment -Favorable condition for reactant nonpolar molecules III. Factors affecting enzyme activity
a) Substrate concentration b) Enzyme inhibition
-Very common situation in the study of drug action -Many drugs work by competing with the normal substrate molecules for the active site of enzymes -Lineweaver-Burke plot:
-Due to the fact that cellular chemical reactions are coupled to form metabolic pathways A B C D E -Three major known mechanisms by which enzyme activities appear to be regulated: a) Change in the rate of synthesis of the enzyme -Induction of the enzyme & repression of the enzyme contribute to gene regulation b) Feedback inhibition of the enzyme - cellular control mechanism by which the end product of a series of metabolic reactions inhibits the activity of an earlier enzyme in the metabolic pathway; thus, when the end product accumulates, its further production ceases c) Allosteric regulation (inhibition): -Occurs by reversible combination of substances with sites on the enzyme other than the active site -Enzyme is called an allosteric enzyme - an enzyme whose active site can be altered by the binding of a small molecule at a non-overlapping site -Enzyme can be activated by this binding = allosteric activation -Enzyme can be inhibited by this binding = allosteric inhibition RNA based enzymes (ribozymes): -First discovered in the protozoan Tetrahymena -RNA molecule involved in splicing (or modifying) RNA intermediate structures -Discovered by Tom Cech DNA structure: -Structure of DNA was deduced by x-ray diffraction and proposed by Watson and Crick 8 characteristics: