Molecular Biology Code of Course: 84310024

1. Molecular BiologyCode of Course: 84310024 School of Life Science, CCNU Prof. Yang Xu Yang Xu, College of Life Sciences

2. Section ACells and Macromolecules Yang Xu, College of Life Sciences

3. A1 Cellular Classification • Prokaryotes • Eubacteria • Archaea • Eukaryotes • Animals • Plants • Fungi • Protists (algae and protozoa) Yang Xu, College of Life Sciences

4. cell wall 质粒 Eubacteria • Structural organization • Plasmamembrane • Most have a rigidcell wall • Cytoplasmcontains a nucleoid • Ribosomes • Pili and flagella • Other components Plasmids /RNA /proteins and so on Yang Xu, College of Life Sciences

5. Archaea • Structurally, they are similar to eubacteria; • In energy production and metabolism they are most like those of eubacteria; • In replication, transcription and translation they are more similar to those of eukaryotes. Yang Xu, College of Life Sciences

6. Eukaryotes • Subcellular compartments (organelles): • Nuclei /mitochondria Golgi complex /endoplasmic reticula ; • They bounded by lipid membranes ; • They are the sites of distinct biochemical processes and define the eukaryotes. Yang Xu, College of Life Sciences

7. Eukaryotes • Cytoskeleton (protein fibers) • Microtubules, made of tubulin • Microfilaments, made of actin Yang Xu, College of Life Sciences

8. A1 Fig. 2. Schematic diagram of a typical eukaryotic cell Yang Xu, College of Life Sciences

9. A3 Macromolecules • Proteins (See Section B) • Nucleic acids (See Section C) • Polysaccharides • Lipids • Complex macromolecules Yang Xu, College of Life Sciences

10. Polysaccharides(I) Polysaccharides are polymers of simple sugars covalently linked by glycosidic bonds. Glucose of plants: Cellulose is a linear polymer with  (l4) linkages; Starch contains two components: - -amylose, a linear polymer with  (l→4) linkages; - amylopectin, a branched polymer with additional  (l→6) linkages. Yang Xu, College of Life Sciences

11. (b) Starch  (l→4)linkages (a) Cellulose  (l4) linkages A3 Fig.1. The structure of celluose Yang Xu, College of Life Sciences

12. Polysaccharides (II) • Glucose polymers of animals: • Glycogen is a branched polymer like amylopectin • Chitin is similar to cellulose, but the monomer is different • is found in fungal cell walls, and • is found in the exoskeleton of insects • Muco/poly/saccha/rides form the gel-like solutions, in which the fibrous proteins of connective tissue are embedded. Yang Xu, College of Life Sciences

13. Lipids (I) Lipid molecules are mainly hydrocarbon • Glycerides have one, two or three long-chain fatty acids esterified to a molecule of glycerol; • In animal triglycerides are solid (fats) at room temperature; • In plant triglycerides are liquids (oils) at room temperature Yang Xu, College of Life Sciences

14. Lipids (II) • Phospholipids • are important constituents of all cell membranes, • consists of glycerol esterified to two fatty acids and onephosphoric acid. • The phosphate is also usually esterified to a small molecule：serine or choline and so on. • Sphingolipids • Sphingomyelin Yang Xu, College of Life Sciences

15. Complex macromolecules • Nucleo/proteins • contain both nucleic acid and protein, • for example: telomeraseand ribonuclease P • Glyco/proteins and proteo/glycans • are proteins with covalently attached carbohydrate • and are generally found on extracellular surfaces • Lipid-linked proteins: covalently attached Lipo/proteins: noncovalently attached • Glycolipids • covalently linked lipid and carbohydrate Yang Xu, College of Life Sciences

16. A3 Fig.3. Glycoprtein structure Yang Xu, College of Life Sciences

17. A4 Large Macromolecular Assemblies • Protein complexes • Nucleoprotein • Membrances Yang Xu, College of Life Sciences

18. Protein complexes • The eukaryotic cytoskeleton consists of various protein complexes: • microtubules (made of tubulin) • Microfilaments (made of actin and myosin) • intermediate filaments(containing various proteins). • These organize the shape and movement of cells and subcellular organelles. • Cilia and flagella are also composed of • microtubules complexed with dyneinand nexin. Yang Xu, College of Life Sciences

19. Nucleoprotein • Ribosomes • Bacterial 70S ribosomes have • a 50S subunit, with 23S and 5S RNA molecules and 31 proteins, • a 30S subunit, with a 16S RNA molecule and 21 proteins. • Eukaryotic 80S ribosomes have • a 60S (28S, 5.8S and 5S RNAs) subunit, and • a 40S (18S RNA) subunits. • Chromatin contains DNA and basic histone proteins. • Viruses are also nucleoprotein complexes. Yang Xu, College of Life Sciences

20. Membranes • Lipid bilayers • Membrane phospholipids and sphingolipids form bilayers • the polar groups on the exterior surfaces and • the hydrocarbon chains in the interior. • Membrane proteins • may be peripheral or integral and • act as receptors, enzymes, transporters or mediators of cellular interactions. Yang Xu, College of Life Sciences

21. A4 Fig. 2. Schematic diagram of a plasma membrance Yang Xu, College of Life Sciences

22. Membrane protein functions • Receptors for signaling molecules such as hormones and neurotransmitters; • Enzymes for degrading extracellular molecules before uptake (吸收); • Channels for the selective transport of small, polar ions and molecules; • Mediators of cell-cell interactions (mainly glycoproteins). Yang Xu, College of Life Sciences

23. That’s all for Section A Yang Xu, College of Life Sciences