PROTEINS

LIFE IS AN ORGANIZED SYSTEM OF COMPLEX CHEMICAL REACTIONS

THE FOUR MOST IMPORTANT MACROMOLECULES IN A LIVING SYSTEM ARE:

NUCLEIC ACIDS: Such as DNA and RNA Nucleic Acids store and transfer chemical information needed by the cell.

CARBOHYDRATES Such as glucose and sucrose Carbohydrates provide the energy to the cell to make ATP

Lipids

Lipids Long–term Energy storage molecules and membranes

PROTEINS Proteins control the chemical activity of the cell and provide the structure of the cell

THERE MAY BE AS MANY AS 60,000 DIFFERENT PROTEINS IN THE HUMAN BODY

Some proteins, such as these collagen fibers, give strength to structures in the body

This genetic condition involving extra stretchy collagen is known as Ehlers- Danlos Syndrome

Hair is made of the protein keratin

The protein melanin gives skin the various shades of color

The protein hemoglobin is in red blood cells and transports oxygen to the cells of the body.

Some hormones are proteins, such as insulin which controls the uptake of glucose by the cells

Beta cells produce the hormone insulin and release it into the blood

Cells have insulin receptors transmembrane proteins that are activated by insulin to allow glucose to move into the cell by facilated difussion

If the cells of the pancreas do not produce insulin, then the person has diabetes and must take insulin produced by other organisms

Other proteins called antibodies protect the body from foreign substances

Such as these antibodies attacking a virus in the blood

Muscles are mostly protien

Both of the muscle fibers, actin and myosin, are proteins

Proteins in the cell membrane allow substances to move into and out of the cell

Perhaps the most important proteins in organisms are enzymes.

Enzymes are proteins that control the rate chemical reactions in the cell

Enzymes do not cause a reaction they make the reaction easier to happen

The enzyme amylase in saliva breaks down starches in the mouth

PROTEINS

All proteins are chains of amino acids

Such as the protein insulin, which is two strands of about fifty amino acids in a chain.

There are about 20 different amino acids. Proteins are different because they have different orders of amino acids.

Amino acids have the same basic structure but the side chains are different, giving them different chemical properties

The side- chains of an amino acid is referred to as an R-group

The R-group is in white.

Some R-groups are polar

Some polar groups have stronger positive or stronger negative areas

The primary structure of a protein is the type and order of the amino acids

Amino acids are linked together by peptide bonds

Peptide bonds are another example of dehydration synthesis

Short chains of amino acids are termed Polypeptides

The secondary structure of a protein is the folding of the amino acid chain.

Tertiary structure is the actual folded structure of the protein

Primary structure is the sequence of amino acids

The secondary is the sheet and helix structures that gives the protein rigidity.

The tertiary structure is the folding of the protein to give it shape

The quaternary structure is the final shape of the protein after it is assembled with other polypeptides

The primary structure is the sequence of the amino acids

Amino acids are connected by covalent peptide bonds

SECONDARY STRUCTURE Alpha Helix

The alpha helix sections of trans- membrane proteins often form the channel in facilitated transport proteins, such as this glucose transport protein

Beta sheets give a protein rigidity

Cystine bonds form between the sulfur atoms in the R- group of the cystine

Disulfide bonds are important in determining the tertiary structure

Disulfide bonds form where the amino acid cystine are brought close together

The difference between curly and straight hair is the the number of disulfide bonds between cystine amino acids in the keratin protein

These two proteins are different because they have a different number and a different order of amino acids.

Some proteins have less than 100 amino acids

Most proteins have many hundred amino acids

The shape of the enzyme proteins are essential for their proper function.

A mistake in the hemoglobin protein can cause a condition called sickle cell disease.

Sickle cell disease is caused by one amino acid difference in the 150 amino acids that make up the hemoglobin molecule.

How do the cells make proteins

We eat proteins in our food. In the stomach and the small intestines digestive enzymes break down the proteins into separate amino acids.

In the small intestines the amino acids are absorbed through the villi into the blood vessels of the circulatory system.

The circulatory system carries the amino acids to all parts of the body in the serum of the blood.

In the capillaries amino acids diffuse into the cells.

In the cytosol the amino acids attach to specific transfer-RNA

Each type of t-RNA combines with a specific amino acid

You have to eat 8 of the amino acids, your body can make the rest. These are called the essential amino acids.

RIBOSOME PROTEIN In the cytoplasm of the cells, amino acids are assembled into the correct order to make the right protein

Ribosomes are very small structures in the cytoplasm of all cells including bacteria Proteins are made on the ribosomes

DNA has the information for the correct order of the amino acids to make a working protein

DNA Ribosomes Messenger-RNA carries the information from the DNA in the nucleus to the ribosomes in the cytoplasm

The information is carried to the ribosomes by RNA

RNA is an exact copy of the information for the sequence of the amino acids to make the protein

DNA is made of four different bases connecting the two sides of the spiraling sides.

The order of the four bases are the code for the order of the amino acids in the protein. The four bases are adenine (A), guanine (G), thymine (T) and cytosine (C).

RNA copies the order of the complimentary bases from the DNA

Each three bases of DNA is the code of one amino acid

DNA makes RNA. RNA takes code out of nucleus to the ribosome

The process of making RNA from DNA is called Transcription

Transcription begins when RNA polymerase attaches to a region of DNA called a promoter

The promoter defines the start of a gene, the direction of transcription and the strand to be transcribed

RNA Polymerase binds to the promoter and binds complementary bases until it reaches a stop sequence

The primary RNA molecule is modified and prepared to leave the nucleus.

1. A cap is added to tell the molecule where to attach to the ribosome

2. The introns are removed by enzymes called spliceosomes

3. The mature RNA leaves the nucleus through a nuclear pore

Introns- Sections of “junk DNA” The functions of introns is truly unknown but the thoughts are: -Allow RNA to be spliced together in slightly different orders -Regulate gene feedback -Allow for complexity in organisms without increasing the amount of DNA

Once the RNA has left the nucleus it is taken to the ribosomes

Ribosomes are made of Ribosomal RNA (rRNA) with a variety of proteins and are broken into two subunits

rRNA provides a binding site for the mRNA and the tRNA once binded the large molecule is called a polyribosome

When the mRNA binds to rRNA translation can occur

Translation occurs in three steps: Initiation- The start codon of the mRNA binds to the small subunit of the rRNA, the initiator tRNA binds along with the large subunit

2. Elongation

3. Termination- When the rRNA reaches a stop codon, the polypeptide is released, and the rRNA breaks into its two subunits

As the protein is being made, the first couple amino acids act as a tag to determine where the protein will end up. When the protein is released from the ribosome if needed, it will be taken to the ER and/or golgi for folding, processing, tagging and packaging

Review of RNA How many types? Functions? What does the R mean? What nucleotides make up RNA?

Sickle Cell Disease is caused by a single mutation in the gene for the globin part of the hemoglobin molecule.

A hemoglobin molecule is made of four globin molecules.

A change of one base in the DNA, will change the base in the RNA, which may change the amino acid, which may change the protein.

If the globin molecules in the hemoglobin protein have the mutation, the cell becomes sickle shape.

If only one of the the globin molecules has the mutation, the cell appears normal..

The sickle-cell hemoglobin changes shape when the oxygen is not attached. This change causes a change in the shape of the red blood cell to a crescent shape.

Under low oxygen conditions the cells with mutated hemoglobin become sickle shaped

Round, normal red blood cells easily pass through the junctions of the capillaries

Sickle red blood cells tend to become trapped at these junctions causing swelling and sometimes life threatening clots

Sickle cell disease is a painful conditions but many individuals, such as this professional model, can lead normal lives with precautions.