Acqua (H2O)

Gliceraldeide - lo zucchero più piccolo OH H H2 (CH20)3 = Carbo - idrato (CH20)n n compreso tra 3 e 8

monomeri polimeri

What is a protein? A protein is a polymer of of fixed length, composition and structure made by a combination of the 20 naturally occurring amino acids.

I legami che aiutano le proteine a ripiegarsi

cisteine:cisteine ponti disolfuro

The structure of proteins can be defined in a hierachical way Primary structure: the AA sequence (Thr-Gly-Leu-Pro-…) Secondary structure: local repetitive motifs common to most classes of protein structures Tertiary structure: the 3D arrangement of the secondary structure motifs to form a compact protein. Quaternary structure: the arrangements of several proteins units to form a functional multimeric structure. The coordinates of all the known structures of proteins can be found in the Protein Data Bank: http://www.rcsb.org/pdb

a-helix

Secondary structure. The a-helix. The a-helix is the most common secondary structure found in proteins. Low strain and intramolecular repulsion of backbone and side chains. a-helices are stabilized by a number of factors. Favorable dipolar interaction in the backbone. Very compact structure, small solvent exposed surface.

Beta foglietto 1998 GARLAND PUBLISHING

Secondary structure. The b-sheet. The b-sheet is made by parallel or antiparallel extended strands connected by a network of hydrogen bonds. Parallel b-sheet Antiparallel b-sheet

Tertiary structure. a-b proteins.

Tertiary structure. b-barrel. Greek key motif

Tertiary structure. Membrane proteins.

Tertiary structure. DNA-binding proteins. Cys Cys Zn Cys Cys The zinc finger

Quaternary structures. K+ channel Haemoglobin HIV-1 protease

PrPc NORMAL CONFORMATION Predominantly alpha-helical Protease sensitive Glycoside modification Sialoglycoprotein associated to cell membrane by covalent attachement to phospholipid (GPI anchor)

PrPc NORMAL CONFORMATION Normally associated to cell membrane of neurons Probably involved in synaptic function

THE DISEASE-ASSOCIATED ISOFORM: PrPsc Predominantly beta-sheet Relatively resistant to proteases It accumulates in brain tissue and can cause apoptosis The infectious form has the same aminoacidic sequence seen in the normal one

PrPc & PrPsc From alpha helical to beta-sheet: the change of conformation is due to a distension of the protein structure

AMPLIFICATION OF PrPsc PrPc PrPSc PrPSc PrPSc Amplification of PrPSc and possible depletion of PrPc The distorted protein can bind to others and induce them to change their conformation as well, producing a chain reaction

Alzheimer’s: Protein Folding gone Wrong…. An amyloid plaque in Alzheimer’s disease is a tangle of protein filaments The amyloid protein (42-43 residues) is derived by proteolytic cleavage of the amyloid precursor protein, a constituent of many healthy cells APP has a-helical conformation, the amyloid protein can change into b-conformation forming aggregates, and plaques

monomeri polimeri

Struttura tipo di un nucleotide

A Nucleoside(-tide) Base H+ Sugar P O OH HO NH2 N - OH O CH2 H Phosphate NH2 N Base - H+ OH O CH2 Sugar H 2’ 3’ 4’ 5’ 1’ Nucleotide Legame N- glicosilico Nucleoside Ribosio 2-Deossiribosio OH

A G C U T

C cytosine OH NH2

Struttura tipo di un nucleotide

nucleoside nucleotide H adenosina ATP ADP AMP

Functions of nucleotides: Energy cycle Cofactors for enzymes Phosphate donors Information flow

Nucleotides Are Very Important Nucleotides have many other functions: • They carry chemical energy in their easily hydrolyzed phosphoanhydride bonds. Example - ATP 2. They combine with other groups to form coenzymes. Example - coenzyme A (CoA) 3. They are used as specific signaling molecules in the cell. Example - cyclic AMP (cAMP)

What is ATP? An organic molecule that stores and releases chemical energy for use in body cells r

Nucleotides and the Energy Cycle 8 Nucleotides and the Energy Cycle NTP NDP + Pi

ATP + Pi ADP

LA CELLULA PERSEGUE DUE OBIETTIVI FONDAMENTALI: la crescita cellulare il differenziamento cellulare In un contesto cellulare sociale, quale il tessuto e/o l’organo, i meccanismi responsabili della crescita e del differenziamento cellulare devono essere tra loro integrati e finemente regolati (omeostasi cellulare). I programmi di crescita e differenziamento cellulare sono geneticamente determinati.

Gli Acidi Nucleici sono le macromolecole depositarie dell’informazione genetica. Due Tipi di Acidi Nucleici DNA → polimero di desossiribonucleotidi RNA → polimero di ribonucleotidi I Nucleotidi sono le subunità degli Acidi Nucleici

Il DNA è un polimero di desossiribonucleotidi

Il RNA è un polimero di ribonucleotidi

Gli Acidi Nucleici sono polimeri di nucleotidi legati tra loro da legami fosfodiesteri tra i C 5’ e 3’