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Home , Cell (biology)

Introduction to , Cell and Molecular II

Losiana Nayak Indian Statistical Institute http://www.isical.ac.in/~losiana_t/

A field of science concerned with studying the chemical and processes of biological phenomena at the molecular level.

A branch of biology dealing with the ultimate physicochemical organization of living matter and especially with the molecular basis of inheritance and synthesis.

Ref: http://www.britannica.com/

Cell: structural unit of

A cell can be distinguished into a outer Cell membrane, central nucleus nucleus and .

cytoplasm Typical of a cell

Robert Hooke, an English scientist, first described cells in 1665. consists of three basic points: 1. All living things are made of cells. 2. The cell is the smallest living thing that can perform all the functions of life. 3. All cells must come from preexisting cells. An Cell cells are different from animal cells. They contain the green photosynthetic pigment . Growth

The answer is , which is of two types

1. [Somatic division] 2. [Genetic division/ Reductional division] Functions of a cell?

Genetic control house Support Storage Packaging Transport Central Dogma of molecular biology Information Only Goes One Way

The central dogma states that once “information” has passed into protein it cannot get out again. The transfer of information from to nucleic acid, or from nucleic acid to protein, may be possible, but transfer from protein to protein, or from protein to nucleic acid, is impossible. Information means here the precise determination of sequence, either of bases in the nucleic acid or of residues in the protein.

Francis Crick, 1958 octomer

2 nm

G

Histone T

C A

C A

T

G

T

A

G

C

A

T

C

T

G

G

C

A

T

Packaging DNA G

C B DNA Helix A Histone octomer

2 nm

G

Histone proteins T

C A

C A

T

G

T

A

G

C

A

T

C

T

G

G

C

A

T

Packaging DNA G

C B DNA Helix A Histone octomer 11 nm Nucleosome

2 nm

G

Histone proteins T

C A

C A

T

G

T

A

G

C

A

T

C

T

G

G

C

A

T

Packaging DNA G

C B DNA Helix A Packaging DNA

Histone H1

A G T C A

T A G

C

C G A T Packaging DNA

Histone H1

A G T C A

T A G

C

C G A T Packaging DNA “Beads on 11 nm a string”

A G T C A 30 nm Looped

T A 200 nm Domains G Tight helical C fiber C G A T

Protein scaffold Packaging DNA 11 nm Nucleosomes 30 nm 700 nm T 200 nm Looped Domains G Tight helical fiber

C

A 2 nm Protein scaffold B DNA Helix A “Simple” Eukaryotic

Transcription Start Site 3’ Untranslated Region 5’ Untranslated Region Introns

5’ Exon 1 Int. 1 Exon 2Int. 2 Exon 3 3’

Promoter/ Terminator Control Region Exons Sequence RNA Transcript Eukaryotic

Cytoplasm

DNA Nuclear Packaging pores Degradation

Transcription Transportation RNA RNA Modification Processing R ib o s o Degradation etc. m AAAAAA G AAAAAA mRNA G e Export Nucleus Stages of Transcription

„ Transcription can be logically divided into three distinct stages:

1. Initiation

2. Elongation

3. Termination Transcription Initiation

„ Proteins called transcription factors bind to the promoter region of a gene „ If the appropriate transcription factors are present, RNA polymerase binds to form an initiation complex „ RNA polymerase melts the DNA at the transcription start site „ Polymerization of RNA begins Coding (sense) strand 5’ 3’ 3’ 5’ Template (antisense) strand Transcription

Coding (sense) strand 5’ 3’ 3’ 5’ RNA Template Pol. (antisense) strand 5’ RNA Transcription

Coding (sense) strand 5’ 3’ 3’ 5’ Template RNA (antisense) strand Pol.

5’ Transcription Termination

There are two types of termination:

„ Rho dependent requires a protein called Rho, that binds to and slides along the RNA transcript. The terminator sequence slows down the elongation complex, Rho catches up and knocks it off the DNA

„ Rho independent termination depends on both slowing down the elongation complex, and an AT rich region that destabilizes the elongation complex Termination (Rho Independent)

RNA Pol.

RNA RNA 5’ Pol.

RNA Pol.

5’ RNA 5’

Terminator Termination (Rho Dependent)

Terminator

RNA Pol.

RNA 5’ ρ Help, rho RNA hit me! Pol.

RNA ρ Pol. 5’ RNA 5’ ρ Products of Transcription

„ Transcription produces three major RNA products: 1.Ribosomal RNA (rRNA) - Several rRNAs are vital constituents of 2.Transfer RNA (tRNA) - The that physically couples nucleic acid codons with specific amino acids 3.Messenger RNA (mRNA) - The nucleic acid messenger that carries encoded information from on DNA to the protein manufacturing ribosomes Requirements for Translation

„ Ribosomes - rRNA and Protiens

„ mRNA - Nucleotides

„ tRNA

„ Aminoacyl-tRNA Synthetase,

„ L Amino Acids

„ ATP - For energy Structure

Peptidyl-tRNA Aminoacyl-tRNA binding site binding site Exit site P A E Large subunit

5’ GAG...C-AGGAGG-NNNNNNNNNN-AUG---NNN---NNN---NNN---NNN--- 3’ mRNA Small subunit Translation - Initiation

fMet

Large P A subunit E

UAC 5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 3’ Small mRNA subunit Translation - Elongation

Polypeptide Met Arg Phe Leu Ser Gly Aminoacyl tRNA

Ribosome P A E UCU

CCA 5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 3’ mRNA Translation - Elongation

Polypeptide Met Phe Leu Ser Gly Arg

Aminoacyl tRNA

P A Ribosome E

CCA UCU 5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 3’ mRNA Translation - Elongation

Polypeptide Met Phe Leu Ser Gly Arg

P A Ribosome E

CCA UCU 5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 3’ mRNA Translation - Elongation

Polypeptide Met Phe Ala Leu Ser Gly Arg Aminoacyl tRNA

Ribosome P A E CGA CCA UCU 5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 3’ mRNA Translation - Elongation

Polypeptide Met Phe Leu Ser Gly Arg Ala

A CC P A Ribosome E

UCU CGA 5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 3’ mRNA Translation - Termination

Met Phe Leu Ser Gly Polypeptide Arg Ala Val

P A Ribosome E CGA CGA 5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-STOP AT GCA...TAAAAAA 3’ mRNA

3’ A

AAAAAA P

STOP E AT GCA...T

GA C Val Ala Arg --AGA--GCU--GUA--UGA- Gly Ser

Leu

A G

Phe C Polypeptide Met -AUG--UUC--CUU--AGU--GGU Translation - Termination mRNA GAG...CU 5’ Transcription And Translation In

5’ 3’

3’ 5’ RNA Pol.

Ribosome mRNA Ribosome 5’ AN OVERVIEW OF

CARBOHYDRATE METABOLISM METABOLISM PROTEIN METABOILSM ENERGY METABOLISM WHAT IS METABOLISM?

A Continuous gradual process of biological systems that includes both building and breaking of macronutrients for the purpose of growth, and . WHAT IT INCLUDES?

METABOLISM

ANABOLISM

GENESIS PROTEINS

Fatty acids Aminoacids Glycerol Other Sugers

Acetyl Co A CO A

ATP ADP

O2 e CITRIC

OXIDATIVE ACID PHOSPHORYLATION CYCLE

2CO2

Signal transduction pathway?

„ Signal means any communication that encodes a message

„ involves conversion of a signal from extracellular environment to functional changes within the cell

„ A Signal transduction pathway is a series of steps that enable signal transmission through physical barriers like , membrane and nuclear membrane General process of a STP

„ Extracellular signal is present outside a cell: typically a , neurotransmitter or

„ Signal binds to a causing a change in receptor conformation, thus transmitting a signal to the interior of the cell

„ The signal precipitates many catalyzed protein interactions, ultimately causing changes in the cell’s functions (ex. glucose uptake, cell division, transcription)

Reference

™ Biochemistry by Lubert Stryer

™ Cell and Molecular Biology by De Roberties and De Roberties

Some Slides are taken from

Timothy G. Standish, Ph. D.