Section A: Cells and MacromoleculesYang Xu, College of Life Sciences Molecular Biology Code of Course: School of Life Science, CCNU Prof. Yang Xu

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences Section A Cells and Macromolecules

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences A1 Cellular Classification Prokaryotes –Eubacteria –Archaea Eukaryotes –Animals –Plants –Fungi –Protists (algae and protozoa)

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences Eubacteria Structural organization – Plasma membrane – Most have a rigid cell wall – Cytoplasm contains a nucleoid – Ribosomes – Pili and flagella Other components Plasmids /RNA /proteins and so on 质粒 cell wall

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences 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.

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences 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.

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences Eukaryotes Cytoskeleton (protein fibers) –Microtubules, made of tubulin –Microfilaments, made of actin

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences A1 Fig. 2. Schematic diagram of a typical eukaryotic cell

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences A3 Macromolecules Proteins (See Section B) Nucleic acids (See Section C) Polysaccharides Lipids Complex macromolecules

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences 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.

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences A3 Fig.1. The structure of celluose (b) Starch  (l→4)linkages (a) Cellulose  (l  4) linkages

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences 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.

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences 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

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences Lipids (II) Phospholipids –are important constituents of all cell membranes, –consists of glycerol esterified to two fatty acids and one phosphoric acid. –The phosphate is also usually esterified to a small molecule ： serine or choline and so on. Sphingolipids Sphingomyelin

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences Complex macromolecules Nucleo/proteins –contain both nucleic acid and protein, –for example: telomerase and 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

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences A3 Fig.3. Glycoprtein structure

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences A4 Large Macromolecular Assemblies Protein complexes Nucleoprotein Membrances

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences 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 dynein and nexin.

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences 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.

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences 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.

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences A4 Fig. 2. Schematic diagram of a plasma membrance

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences 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).

Section A: Cells and MacromoleculesYang Xu, College of Life Sciences That’s all for Section A