Section A - Cells and Section A - Cells and macromoleculesmacromolecules

单虫无核原生动物 原生动物 植 物 真 菌 动 物

ContentsContents

A1 Cellular classificationA1 Cellular classification Eubacteria, Archea, Eukaryotes, Cellular differentiation

A2 Subcellular organellesA2 Subcellular organelles Nuclei, Mitochondria and chloroplasts, Endoplasmic reticulum

, Microbodies, Organelle isolation

A3 MacromolecularesA3 Macromoleculares Protein and nucleic acids, Polysaccharides, Lipids,

Complex Macromolecules

A4 Large macromolecular assembleA4 Large macromolecular assemble Protein complex, Nucleoprotein, Membranes,

Noncovalent interactions

A1 Cellular classificationA1 Cellular classification--EubacteriaEubacteria

• The The EubacteriaEubacteria are one of two are one of two subsubdivisiodivisions(ns( 亚门亚门 ) of the ) of the prokaryotesprokaryotes..

• Escherichia.coliEscherichia.coli is the best studied euba is the best studied eubacterium.cterium.

• Prokaryotes are the simplest living cells.Prokaryotes are the simplest living cells.

• Most prokaryotes are Most prokaryotes are uniunicellularcellular(( 单细单细胞胞 ), some, however, are ), some, however, are multimulticellularcellular(( 多多细胞细胞 ). forms in which certain cells carry ). forms in which certain cells carry out specialized functions.out specialized functions.

STRUCTURESTRUCTUREFlagella ： Cell movement.Pili ： To allow the cell to attach to other cells and surface.Capsule ： A well organized layer, it can be the cause of

various diseases.Cell wall ： To prevent cell lysis in environments of low o

smolarity.Plasma membrane: Lipid bilayer and embedded proteins for small molecule exchange.Nucleiod ：Single and circular chromosome.Ribosmes ：protein synthesis machinery

A1 Cellular classification—A1 Cellular classification—ArcheaArchea

• The Archaea, or Archaebacteris, from the second subdivision of the prokaryotes and tend to inhabit extreme environments.

• Structurally, they are similar to eubacteria. But their rRNA are similar to eukaryotes (18s rRNA) .

• It appears that the archaea and the eukaryotes share a common evolutionary (( 进化的进化的 )) ancestorancestor which diverged from the ancestor of the Eubacteria.

A1 Cellular classification—A1 Cellular classification—EukaryotesEukaryotes

• Eukaryotes are classified taxonomically ( 分类学 ) into four kingdoms comprising animals, plants, fungi, and protists.

Cancerous HeLa cells (It can be indefinitely cultured as long as conditions are favorable )

Animal cells Plant cells

Cytoskeletal Fiber ：1. Controls the shape and movement of the cell2. Organizes some metabolic functions

A1 Cellular classification—A1 Cellular classification—DifferentiationDifferentiation

• Cell divides: the daughter cells may be idential in every way.

• In all but a few exceptional case, the DNA content remains the same, but the genes which are transcriptional have changed.

• Differentiation is regulated by developmental control genes.

In some cases, a highly unequal cell division occurs in mammalian oocytes , resulting in one larger daughter cell than another.

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

For example

1.Spore formation among prokaryotes and lower eukaryotes.

2.Embryonic cell differentiate into highly specialized cells among higher eukaryotes.

Fig

Fig

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

backback

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

tadpole

Differentiation is regulated by developmental control genes

• In the center of the diagram are three of the early steps in the development of a mammal. On the top and bottom are some of the fully-differentiated cell types that will eventually form in the adult.

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 m, no distinct subcellular organelles, pili, flagella

10-100 m,Organelles

Biochemistry

rRNA molecules are different among these kingdoms

(rRNA based phylogeny)Ester linkage（酯键）

Ether linkage （醚键）

Ester linkage（酯键）

Energy production, metabolism

Replication, transcription and translation

Differentiation Formation of spores Embryonic cell differentiation

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

A2 Subcellular organelles—A2 Subcellular organelles—Nuclei Nuclei （细胞核）（细胞核）

• Bounded by a nuclear membrane having pores connecting it with the endoplasmic reticulum.

• Contains one or more paired, linear chromosomes composed of deoxyribonucleic acid (DNA) associated with histone proteins .

• Contain nucleolus.

The cell nucleus is a remarkable

organelle because it functions to:

1) Store genes on chromosomes.

2) Organize genes into chromosomes

to allow cell division.

3) Transport regulatory factors &

gene products via nuclear pores.

Nuclear Envelope Structure-two unit membranes with a fluid-filled space. Two membranes were separated by 10 to 50nm. -nuclear pores present. -outer membrane may be continuous with the endoplasmic reticulum. Function -selectively permeable to control movement in or out.           -contains nuclear contents.

Average approximately 3000 nuclear pores per cell.

A2 Subcellular organelles—A2 Subcellular organelles— Mitochondria and chloroplastsMitochondria and chloroplasts

• Mitochondria are the site of cellular respiration where nutrients are oxidized to CO2 and water, and ATP is generated.

• Photosynthesis takes place in the chloroplasts.

Mitochondrion

Chloroplast

Lighter energy GlucoseATPChemical energy

A2 Subcellular organelles—A2 Subcellular organelles— Endoplasmic reticulumEndoplasmic reticulum

The endoplasmic reticulum (ER) is repsonible for the production of the protein and lipid components of most of the cell's organelles.

A2 Subcellular organelles—A2 Subcellular organelles—MicrobodiesMicrobodies

• A microbody is a cytoplasmic organelle of a more or less globular shape that comprises degradative enzymes bound within a single membrane.

• Types include lysosomes, peroxisomes, glyoxisomes, glycosomes and Woronin bodies.

A2 Subcellular organelles—A2 Subcellular organelles—Organelle isolationOrganelle isolation

Density gradient centrifugationRate zonal (velocity) centrifugationEquilibrium centrifugation

Differential (speed) centrifugation:

A3 Macromoleculares—A3 Macromoleculares— Protein and nucleic acidsProtein and nucleic acids

• Proteins are polymers of amino acids, and nucleic acids DNA and RNA are polymers of nucleotides.

A3 Macromoleculares—A3 Macromoleculares—PolysaccharidesPolysaccharides

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

A3 Macromoleculares—A3 Macromoleculares—LipidsLipids

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

Phospholipids( 磷脂 )

Cholesterol （胆固醇）

Glycolipids （糖脂）

A3 Macromoleculares—A3 Macromoleculares— Complex macromoleculesComplex macromolecules

• NucleoproteinsNucleoproteins

• GlycoproteinsGlycoproteins

• ProteoglycansProteoglycans

• Lipid-linked proteinsLipid-linked proteins

• LipoproteinsLipoproteins

• GlycolipidsGlycolipids

Histone, Chromatin, Telomerase, RNP (RNA/Histone, Chromatin, Telomerase, RNP (RNA/protein complex), and Protaminesprotein complex), and Protamines

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

A4 Large macromolecular assemble—A4 Large macromolecular assemble— Protein complexesProtein complexes

• Cilia and flagella are also composed of microtubules complexed with dynein and nexin.

Protein complexProtein complex

microbulemicrobule microfilamentmicrofilament intermediate fibreintermediate fibre

A4 Large macromolecular assemble—A4 Large macromolecular assemble—NucleoproteinNucleoprotein

• Nucleoproteins comprise both nucleic acid and protein.

1.Ribosome: ribosomal proteins ＋ rRNAs

2.Caryotin: deoxyribonucleoprotein consisting of DNA & histones to form a repeating unit called nucleosome

3.Viruses: protein capsid + RNA or DNA

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

5.Ribonuclease P: tRNA maturation. Protein ＋ P RNA

A4 Large macromolecular assemble—A4 Large macromolecular assemble—MembranesMembranes

1. Membrane Lipid( Glycolipid, Phospholipid)

2. Membrane proteins( Integral protein, Transmembrane protein, Peripheral protein, Glycoprotein)

A4 Large macromolecular assemble—A4 Large macromolecular assemble— Noncovalent interactionsNoncovalent interactions

• Van Der Waals Force; Dispersion forces; HVan Der Waals Force; Dispersion forces; Hydrogen Bonds; Ionic bonds ; Hydrophobic ydrogen Bonds; Ionic bonds ; Hydrophobic interactions interactions

• Charge-charge interactions (salt bridges): Charge-charge interactions (salt bridges): charged molecucharged molecu

lesles

• Charge-dipole, dipole-dipole: Charge-dipole, dipole-dipole: either or both of the participaeither or both of the participa

nts is a dipole.nts is a dipole.

• Dispersion interactions: Dispersion interactions: non-poplar moleculenon-poplar molecule

• van der Waals forces: van der Waals forces: noncovalent associations between noncovalent associations between uncharged molecules.uncharged molecules.

• Hydrogen bonds (dipole-dipole): Hydrogen bonds (dipole-dipole): nucleic acidsnucleic acids

• Hydrophobic interaction: Hydrophobic interaction: proteinsproteins

Multiple choice Multiple choice questionsquestions

1 ． The glycosylation of secreted proteins takes place in the .

A mitochondria. B peroxisomes. C endoplasmic reticulum. D nucleus.

2 ． Which of the following is an example of a nucleoprotein?

A keratin. B chromatin. C histone. D proteoglycan.

3 ． Which of the following is not a polysaccharide?

A chitin. B amylopectin. C glycosaminoglycan. D glycerol.

4. Transmembrane proteins . A join two lipid bilayers together. B have intra- and extracellular domains. C are contained completely within the membra

ne. D are easily removed from the membrane.

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