Download Ppt for Genetics II

Insulin: Weight = 5733, 51 amino acids
Glutamine Synthetase: Weight = 600,000, 468 amino acids
Amino Acids &
Dehydration Synthesis
Amino acid structure:
Functional groups
Peptide bonds
Sample amino acid structures:
carboxyl group-blue
alpha carbon-gray
amino group-green
R groups-beige
The
twenty
essential
amino
acids.
Note R
groups
in blue
Amino Acids w/ various R
groups
Nonpolar amino acids
Neutral Amino Acids
Ionic amino acids
Amino acids are joined together in
proteins by peptide bonds.
• A peptide bond forms between the
carboxyl group of one amino acid
(amino acid 1 in the figure preceding)
and the amino group of the adjacent
amino acid (amino acid 2).
Dehydration
synthesis
Dehydration synthesis animation
Dehydration Synthesis
Dehydration Synthesis:
Amino acid 1
Amino acid 2
Amino group
Dipeptide
(Peptide bond)
Protein Structure
• Amino acid structure
• Dehydration synthesis
Insulin: Weight = 5733, 51 amino acids
Glutamine Synthetase: Weight = 600,000, 468 amino acids
Four ‘levels’ of
protein structure
Four
levels of
protein
structure
Primary structure:
Visualized as a straight chain of aa’s,
but with a specific sequence,
As determined by its gene
Secondary structure:
alpha helix or beta pleated sheet
Tertiary structure: coiled chains
of aa’s are folded & wound
around themselves
Close up of 2o & 3o Protein Structure
Quarternary structure:
separate polypeptide chains
are combined
Levels of Protein Structure
Four Levels of
Protein Structure
(note change in
scale from 2o to 3o)
Collagen molecule
Actin molecule
Myosin molecule
Hemoglobin molecule
Antibody molecule
(purple) Reverse
transcriptase
of HIV1 w/
a fragment of
DNA (colors)
Protein
Synthesis:
Transcription
& Translation
Transcription:
Making a copy
of the blueprint
Morse Code Key
Using the Genetic Code:
DNA :: mRNA :: Protein
• Get from ‘language’ of DNA (A,G,C,orT)
to ‘language’ of protein (aa’s)
• DNA’s ‘language’ is a triplet code in
which 3 nucleotide bases (a codon)
specify 1 amino acid in protein.
DNA (1 gene) :: mRNA :: polypeptide
Steps in
Transcription
Transcription:
Note the free
nucleotides
DNA unzips
Complementary base pairing
mRNA- final product of
Transcription
mRNA moves off
to ribosome
Transcription:
Getting the
plan straight
(copying the
gene)
Transcription
animation
Transcription animation
Translation
Building the protein
from the plan
Using the Genetic Code:
DNA :: mRNA :: Protein
• Get from ‘language’ of DNA (A,G,C,orT)
to ‘language’ of protein (aa’s)
• DNA’s ‘language’ is a triplet code in
which 3 nucleotide bases (a codon)
specify 1 amino acid in protein.
Structure of a Ribosome
Structure
of a tRNA
Translation:
purple = mRNA
blue = ribosome
yellow = tRNA
(note anticodon)
white = amino acids
red = peptide bond
Translation initiation
Translation initiation (cont)
Translation- elongation
Translation- termination
A Polysome: With more than one ribosome
translating an mRNA at one time, it is possible
to produce many polypeptides simultaneously
from a single mRNA.
Protein
Synthesis
In a prokaryotic cell, transcription and translation are
coupled; that is, translation begins while the mRNA is still
being synthesized.
In a eukaryotic cell, transcription occurs in the nucleus,
and translation occurs in the cytoplasm.
Protein
synthesis in
eukaryotes
Antibiotic
Mechanism
Antibiotic
Mechanism
Collagen molecule
Actin molecule
Myosin molecule
Antibody molecule
Hemoglobin molecule
Enzymes
Definitions:
• Catalyst = An additive that speeds up a
chemical reaction without itself being
consumed or changed by the reaction
• Enzyme = A protein that acts as a catalyst,
usually in a biological context.
– All enzymes are proteins, not all proteins
are enzymes
Enzyme mechanism of action:
An enzyme improves the odds
of ‘useful’ collisions
between substrate molecules.
Steps in enzyme function
Enzyme-substrate animation
S = substrate
E = enzyme
P = product
ES = enzymesubstrate complex
Lock & Key Model:
Enzymes are very specific and it was suggested by Emil
Fischer in 1890 that this was because the enzyme had a
particular shape into which the substrate(s) fit exactly. This
is often referred to as "the lock and key" hypothesis. An
enzyme combines with its substrate(s) to form a shortlived enzyme-substrate complex.
Induced fit hypothesis:
In 1958 Daniel Koshland suggested a modification to the "lock and key"
hypothesis. Enzymes are rather flexible structures. The active site of an
enzyme could be modified as the substrate interacts with the enzyme.
The amino acids side chains which make up the active site are molded into
a precise shape which enables the enzyme to perform its catalytic function.
In some cases the substrate molecule changes shape slightly as it enters
the active site.
A suitable analogy would be that of a hand changing the shape of a glove
as the glove is put on.
Enzyme Animation
Enzyme Websites:
• Enzyme notes in ppt format, few diagrams:
•
http://www.hcc.mnscu.edu/programs/dept/chem/V.28/page_id_2897.html
• animation of enzyme action
•
http://web.ukonline.co.uk/webwise/spinneret/other/hienz.htm
• written outline- enzymes by Worthington
•
http://www.worthington-biochem.com/introBiochem/introEnzymes.html
• asd
Enzyme & Cell
Regulation
• Gene activation
• Feedback loops for enzyme activity
Various possible routes of feedback in the
production-regulation of a given protein
Changing the conformation (shape) of an enzyme’s
active site changes its ability to act as a catalyst
Zymogens: Enzyme Precursors
Competitive Enzyme Inhibition
Allosteric Modulation of an Enzyme
Genes can be either inducible or repressible.
Many genes are normally blocked by the action
of a repressor protein. This prevents the RNA polymerase
enzyme from binding to the gene and transcribing the
structural gene. Such genes are induced by the arrival
of an inducer molecule which binds to the repressor
protein and rendering it inactive. This allows transcription
from the structural gene and the production of a protein.
Other genes are normally active and able to be constantly
transcribed, because the repressor protein is produced in an
inactive form. On the arrival and binding of the corepressor
molecule the complex can act as a functional repressor and
block the structural gene by binding at the operator site.
Steps in
Transcription
DNA
Technology
Bases:
A- adenine
G- guanine
T- thymine
C- cytosine
Other translation animations:
• Add an amino acid to tRNA•
http://www.phschool.com/science/biology_place/biocoach/translation/addaa.html
• Initiation of Translation•
http://www.phschool.com/science/biology_place/biocoach/translation/init.html
• Elongation of Polypeptide•
http://www.phschool.com/science/biology_place/biocoach/translation/elong1.html
• Termination of Polypeptide•
http://www.phschool.com/science/biology_place/biocoach/translation/term.html