FROM DNA TO PROTEINSCHAPTER 7

AND PAGES 103-105

Molecular Genetics

Proteins review

Proteins determine cell structuresProteins are made up of amino acidsProteins are synthesized by ribosomes

There are 20 different amino acids commonly found in the proteins of living things.

http://www.chem4kids.com/files/aminoacids/

Proteins review

Primary Protein Structure is a sequence of a chain of amino acids.

Secondary Protein Structure occurs when the sequence of amino acids are linked by hydrogen bonds.

Proteins review

Tertiary Protein Structure occurs when certain attractions are present between alpha helices and pleated sheets

Quaternary Protein Structure is a protein consisting of more than one amino acid chain.

Proteins are made of amino acid chains. The amino acids are connected by

peptide bonds. Many different amino acid types combine in different orders to create the millions of proteins you will discover in the natural world.

Scientists are working in their labs to create new proteins that might be used in medicine. 

The amino acids found in proteins are connected with peptide bonds.

You will also find other common bonds in proteins as the protein begins to refine its shape.

There are hydrophobic/hydrophilic interactions and disulfide bridges. 

Structural proteins are not able to be dissolved in water.

Because structural proteins are designed to support an organism and the organism is made water, the proteins would not work if they could be dissolved in the water.

Imagine if the proteins in your muscles could be dissolved in water.

They would just be liquid and your body would wind up with no structure. 

Dipeptides have two amino acids. Polypeptides can have over one hundred. Most proteins are made of several amino

acid chains bonded together. It is not a straight chain. The chains sometimes rest on each other

and remain somewhat independent. The hemoglobin molecule that your body

uses to transport oxygen has four interconnected amino acid chains (subunits). 

Proteins require a very specific order for their amino acids to remain functional.

If one amino acid is missing, the entire protein might not work.

The initial synthesis of the amino acid chain is the time when the series is set in stone.

If the order is incorrect, the protein will most likely fold incorrectly and not be functional. 

 Hemoglobin carries oxygen to your cells.

Insulin is a hormone involved in digestion.

Myosin is a part of your connective tissue. 

Proteins can be found everywhere in an organism.

The can be in the cell, on the membrane, or outside of the cell. 

Review/Introduction to DNA

Deoxyribonucleic acid is DNA.DNA contains genetic code for the organism.

DNA is an organic moleculeDNA also contains instructions for proteins

Central Dogma of Molecular Biology

Dogma is a belief or set of beliefs that is accepted by the members of a group without being questioned or doubted

DN

A Located in the nucleus

RN

A On the side of the DNA in the nucleus which exits the nucleus

Pro

tein sMade in

the cytoplasm by the ribosomes

Discovery of DNA

1920’s Frederick Griffith made an important discovery.

He discovered two different strands of bacterium, called R(rough) strain and S(smooth) strain.

See his experiment on page 150

Avery’s Contribution

Oswald Avery tried to answer questions raised by Griffiths work.

He ruled out proteins as the genetic material.

Concluded that DNA is the substance that controls the characteristics of organisms.

http://www.dnalc.org/view/16375-Animation-17-A-gene-is-made-of-DNA-.html

Hershey and Chase

1950’s Alfred Hershey and Martha Chase did experiments with viruses and bacteria.

They confirmed that DNA is the genetic material.

Chargaff

Edwin Chargaff studied DNA from different species

He was interested in the 4 nitrogen bases of DNA: adenine (A), guanine (G), Cytosine (C), and Thymine (T).

The concentrations of the four bases varied from species to species but had similar ratios within the species.

This is known as Chargaff’s rules

The Double Helix

1950’s Rosalind Franklin starting working with DNA fibers, used x-ray techniques to analyze the structure of DNA.

1953 Francis Crick and James D. Watson published their double helical model of DNA.

DNA has the shape of a double helix, just like a spiral staircase.

The Double Helix

There are 2 sides, called sugar-phosphate backbones.

The steps or rungs of the double helix are made from the base pairs formed between the nitrogen bases.

The double helix is held together by hydrogen bonds.

Because of the complementary nature of DNA, the bases on one strand determine the bases on the other strand.

The bases of adenine and guanine are the purines, two ring structure of nitrogenous bases.

The bases of thymine and cytosine are pyrimidines which have a one ring structure.

By having a purine always combine with a pyrimidine in the DNA double helix, the distance between the two sugar-phosphate backbones is constant, maintaining the uniform shape of the DNA molecule.

Read page 153 and highlight key information.

RNA

DNA alone cannot “tell” cells how to make proteins.

It needs the help of RNA.RNA is a nucleic acid and differs

from DNA in several ways Is single stranded Contains the nitrogen base uracil (U) instead of

thymine Contains the sugar ribose instead of deoxyribose

Types of RNA

Messenger RNA (mRNA) copies and carries

Ribosomal RNA (rRNA) forms ribosomes

Transfer RNA (tRNA) brings amino acids

Video on protein synthesishttp://www.youtube.com/watch?v=YxLdBNA

xqKgComplete the practice activity in the video

with codons

Transcription and Translation

Video 9:35http://www.youtube.com/watch?v=Ynmxwqiv

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