Http:// Gene Expression Defines Cells.
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Transcript of Http:// Gene Expression Defines Cells.
Principle information molecules in the cell
Linear polymer of nucleotides (or bases)
Two types Deoxyribonucleic Acid – DNA
Information storage in cells Ribonucleic Acid – RNA
Information carrier in cells
DNA is a Nucleic Acid
For DNA bases are A, C, G, T Sugar is deoxyribose (no OH at 2’ position)
For RNA bases are A, C, G. U Sugar is ribose (OH at 2’ position)
DNA and RNA
Holds nucleic acid strands together
H-bonding between complementary bases This is an interaction that is easily broken
A pairs with T (DNA), (A-U for RNA)
G pairs with C (both DNA and RNA)
Complementary Base Pairing
Transcription Initiation
http://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Simple_transcription_initiation1.svg/721px-Simple_transcription_initiation1.svg.png
Promoter with Transcription Factors
http://stemcells.nih.gov/StaticResources/info/scireport/images/figurea6.jpg
Transcription and Translation
Proteins
Primary functional molecules of the cell; execute the tasks directed by the genetic material
1. Structural molecules (e.g., hair, fingernails, connective tissue)
2. Transmitting Information between cells (e.g., hormones)
3. Defense against infection (e.g., antibodies)
4. Enzymes (catalyze nearly all biochemical reactions)
Building Blocks are Amino Acids
20 different amino acids in proteins
Chemical properties of side chains determine function
Central carbon atom (Ca)
1. H atom
2. Amino group (NH3+)
3. Carboxyl group (COO-)
4. R group (side chain)
R-group (Side Chain)
R -group determines identity, function
A.A. are categorized by chemical properties of the side chains
1) Polar (uncharged) = hydrophilic
2) Positively charged (basic) = ionic
3) Negatively charged (acidic) = ionic
4) Nonpolar = hydrophobic
Nonpolar Amino Acids
The side chains of these a.a. tend to be located in the interior of proteins, where they are not in contact with water.
Peptide Bond
Links amino acids
Amide linkage between -NH3 and -COO-
Defines amino (N) terminus and carboxy (C) terminus
Protein Structure
Polypeptide (protein) chains fold into globular structure
Defines cracks and crevices that can interact with other molecules
Allows proteins to be enzymes
Enzymes
Enzymes are catalysts
They increase the rate of reactions
This allows rapid synthesis and degradation of products in cells
Building Proteins -Translation
mRNA contains 3 nucleotide codons Each codon specifies an amino
acid
Triplet codons are decoded by tRNA decoding is base pairing between
codon on mRNA and anticodon on tRNA
Each tRNA carries a specific amino acid codon-anticodon pairing delivers
specific aa to the growing polypeptide chain
"protein: synthesis." Online Art. Britannica Student Encyclopædia.
10 Aug. 2008 <http://student.britannica.com/eb/art-1692>.