Chapter 1 Cells and macromolecules

Prokaryotic cell

Eukaryotic cell

Protein

DNA

RNA

Other macromolecules unrelated to MB course

Polysaccharides

lipids

Complex macromolecules including these molecules

1.1 Cellular classification (Eubacteria,

Archea, Eukaryotes, Cellular differentiation)

1.2 Subcellular organelles (Nuclei,

mitochondria and chloroplasts, endoplasmic reticulum,

microbodies, organelle isolation)

1.3 Macromolecules (protein and nucleic

acids, polysaccarides, lipids, complex macromolecules)

1.4 Large macromolecular

Assemblies (protein complex, nucleoprotein,

membranes, noncovalent interactions)

1.1 Cellular classification

Prokaryotic cell

Eukaryotic cell

Classifying organisms according to cell types

Prokaryotes （原核生物）(Simplest living cells) Eukaryotes

（真核生物）Eubacteria（真细菌）

Archaea（古细菌）

Structural features

1-10 mm, no distinct subcellular organelles, pili, flagella

10-100 mm,Organelles

Biochemistry

rRNA molecules are different among these kingdoms

(rRNA based phylogeny, Fig. S2)Ester linkage （酯键） (link)

Ether linkage （醚键）

Ester linkage （酯键）

Energy production, metabolism

Replication, transcription and translation

Differentiation (link)

Formation of spores Embryonic cell differentiation

重点

Phylogenetic tree determined by rRNA sequence comparisons(rRNA 序列比较得到的系统发育树）

Fig. S2

典型原核细胞示意图

( 类核 ) ( 纤毛 )

( 鞭毛 )

重点

Cell wall: to prevent cell lysis in environments of low osmolarityPlasma membrane: lipid bilayer and embedded proteins for small molecule exchangeGenetic materials: nucleiod (single and circular chromosome), plasmidRibosmes: protein synthesis machineryPili: to allow the cell to attach to other cells and surfaceFlagella: cell movement

典型真核细胞示意图

重点

Cytoskeletal Fiber ：1.Controls the shape and

movement of the cell2.Organizes some metabolic

functions

1. Definition: The daughter cells change their patterns of gene expression to become functionally different from the parent cell after cell division.

2. The main molecular reason: change of the genes being transcribed, but not that of the DNA content.

3. Regulated by developmental control genes, mutations in these genes result in abnormal body plans.

Cellular differentiation ( 细胞分化 )

For example

•Spore formation among prokaryotes and lower

eukaryotes

•Embryonic cell differentiate into highly

specialized cells among higher eukaryotes.

Cross with Cell Biology Course

Cell differentiation in yeast ( 酵母）Mating: n + n 2nSpore formation: 2n n + n

Embryonic cell differentiation in Xenopus ( 爪蟾属 ) ： from a single cell to an adult

tadpole

Differentiation is regulated by developmental control genes

Fig. S4

1.2 Subcellular

organelles

•Nuclei

•mitochondria and chloroplasts,

•endoplasmic reticulum,

•microbodies,

•organelle isolation

Cross with Cell Biology

（核）

DNA replicationRNA transcription & processing Ribosome assembly

（线粒体）

Main function: cellular respiration/ATP production via oxidative phosphorylation

DNA replication, RNA transcription, protein synthesis

Nuclear-encoded Mitochonrial proteins: synthesis and transportation

（类囊体）

（基粒）

Photosynthesis, the light-dependent assimilation of

CO2 and H2O to form carbohydrates and O2

DNA replication, RNA transcription, protein synthesis

A plant specific organelle

（叶绿体）

Nuclear-encoded chloroplast proteins: synthesis and transportation

drug oxidation and detoxificatin

( 内质网 )

Protein synthesis

（酯类代谢）（药物的氧化和解毒）

Microbodies (lysosomes, peroxisomes and glycoxysomes)（溶酶体，过氧化物酶体，醛氧化酶体）

Glyoxysomes are specialized plant peroxisomes which carry out the reactions of glyoxylate cycle （乙醛酸循环） .

Organelle isolation: centrifugation ( 离心 )Density gradient centrifugationRate zonal (velocity) centrifugationEquilibrium centrifugation

Differential (speed) centrifugation:

Sedimentation coefficient (s)

Density gradients: to prevent convective mixing of the components after separation and to ensure linear sedimentation rates of the components

Supporting materials: sucrose ( 蔗糖） , Ficoll, cesdium chloride （氯化铯）

1.3 Macromolecules

Protein (Section B)

Nucleic acids (Section C)

Polysaccharides

Lipids

Complex macromolecules

MB course (X),

Biochemistry ()

Immunology ()

Polysaccharides are polymers of simple sugars covalently linked by glycosidic bonds.

Lipids: individual lipids are not strictly macromolecules, large lipid molecules are built up from small monomeric units and involved in many macromolecule assembly

Triglycerides ( 甘油三酯 )

Complex macromolecules ( 复合大分子）

Covalent or noncovalent associations of more than one major classes of large biomolecules which greatly increases the functionality or structural capabilities of the complex.

Nulceoprotein: nucleic acids + protein (Section A4)

Glycoprotein: carbohydrate + protein

Lipoprotein: Lipid + protein

生物大分子间相互作用的化学力

生物大分子的基本结构是靠共价键结合的，但是生物学功能的执行是靠生物大分子之间的相互作用来实现的。如：①蛋白质与DNA 的相互作用；②蛋白质与 RNA 的相互作用；②蛋白质与蛋白质的相互作用。

生物大分子间相互作用的化学力 1 扩散作用 (Diffusion) 2 专一性相互作用结构基序，离子键，氢键，范德华力

1 、共价键 (Covalent bond) ：成键原子间通过电子对共享形成的。键

能一般在 200KJ/mol 以上。 磷酸二酯键、肽键、二硫键，－ S － S －2 、弱键（非共价键 noncovalent

bond ）：小于 20KJ/mol 。（ 1 ）氢键 (Hydrogen bond)

（ 2 ）盐键（离子键）静电作用力 (Ionic bond)

（ 3 ）范德华力（短程力） (Van der Waals force)

（ 4 ）疏水作用 (Hydrophobic interaction)

3 、配位键一般在 250KJ/mol 以上

生物大分子内部相互作用的化学键

1.4

Large macromolecular

Assemblies

Protein complexes

Nucleoprotein

Membranes

Noncovalent interactions

protein complexes

Long polymers of tubulin

Fig.1. Schematic diagram showing the (a) cross-sectional and (b) surface pattern of tubulin a and b subunits in a microtubule

(microfilament)

actin and myosin, components of muscle fibers as well

keratin

(cilia and flagella)

Noncovalent interaction

重点

Crystal structure of 50S rRNA

Nulceoprotein (1) associations of nucleic acids and proteinRibosome: ribosomal proteins ＋

rRNAs

重点

•Chromatin ( 染色质 ):

•Viruses:

•Telomerase ( 端粒酶 ) :

•Ribonuclease P ：

deoxyribonucleoprotein consisting

of DNA & histones to form a repeating unit called nucleosome

protein capsid + RNA or DNA

replicating the ends of eukaryotic chromosomes. RNA acts as the replication template, and protein catalyzes the reaction

tRNA maturation. Protein ＋ P RNA

Nulceoprotein (2)重点

Noncovalent interactionsThe force of macromolecule assembly

van der Waals forces: noncovalent associations between uncharged molecules.

*Hydrogen bonds (dipole-dipole): nucleic acids*Hydrophobic interaction: proteins

Charge-charge interactions (salt bridges): charged

molecules

Charge-dipole, dipole-dipole: either or both of the

participants is a dipole .

Dispersion interactions: non-poplar molecule

重点

( 偶极 )

(uncharged molecules)