2.6. Proteins. Flashcards
More than _______of the dry mass of most cells is protein
50%
Proteins have many important functions such as?
-All enzymes are proteins
-Proteins are essential components of cell membranes
-Some hormones are proteins, for example, insulin and glucagon
-The oxygen carrying pigments, hemoglobin and myoglobin are proteins
-Antibodies which attack and destroy invading microorganisms are protein
-collagen is a protein that adds strength to many animal tissues, for example, bone and the wall of arteries
-hair nails, and the surface layers of skin contain the protein keratin
-actin and myosin are the proteins responsible for muscle contraction
-proteins maybe storage products for example casein in milk and ovalbumin in eggs
What is the general structure of amino acid
Center carbon atom
Amino group on the right
Carboxylic acid group on the left
The functional group on the top
The hydrogen element the bottom
Have our peptide bonds formed?
One element loses a hydroxyl group from its carboxylic acid group while the other loses a hydrogen group from its amino group. This leaves the carbon atom of the first amino acid free to bond with the nitrogen atom of the second.. this link is called a peptide bond
Have our peptide bonds formed?
One element loses a hydroxyl group from its carboxylic acid group while the other loses a hydrogen group from its amino group. This leaves the carbon atom of the first amino acid free to bond with the nitrogen atom of the second.. this link is called a peptide bond
What is a peptide bond?
The covalent bond joining neighboring amino acids together in proteins, it is a C-N link between two amino acid molecules
A protein molecule may have just one polypeptide chain or it may have
Two or more chains
Hydrolysis of protein happen naturally in
Stomach and small intestine during digestion of proteins in food
What is the primary structure?
The particular amino acids contained in the chains and the sequence in which they joined
How is the secondary structure formed?
The amino acids in a polypeptide chain may have an effect on each other, even if they’re not next to each other in the primary sequence of amino acids. This is because the polypeptide chain can bend back on itself. Polypeptide chain, or part of it often calls into a cockscrew shape forming a secondary structure called alpha helix
What causes the secondary structure?
The hydrogen bonding between the oxygen of C=O group of one amino acid and the hydrogen of -NH of the amino acid four places ahead of it
Sometimes hydrogen bonding in proteins can lead to
Result in a much looser straighter shape than the alpha helix which is called a beta pleated sheet
Sometimes hydrogen bonding in proteins can lead to
Result in a much looser straighter shape than the alpha helix which is called a beta pleated sheet
What is the secondary structure?
The structure of a protein molecule, resulting from the regular coiling or folding of the chain of amino acids(m
What is alpha helix?
A helical structure formed by a polypeptide chain held in place by hydrogen bond
What is a beta pleated sheet?
A loose sheet like structure formed by hydrogen bonding between parallel polypeptide chains
Although the hydrogen bonds are strong enough to hold the alpha helix and beta- plated sheet structures in shape, they are easily broken by
High temperatures and pH changes
Why do some proteins have no regular arrangement in its secondary structure
Some proteins do not show regular arrangement because it depends on which R groups are present and what attraction occurs between amino acids in the chain
What is tertiary structure?
The compact structure of a protein molecule, resulting from three dimensional coiling of the chain of amino acids
The secondary structure is itself coiled or folded to form the tertiary structure
What are the four types of bond that helped to keep folded proteins in their precise ship?
-hydrogen bonds
-Disulfide bonds from between two cysteine(a sulphur containing amino acids) molecules contain sulfur atom.
-ionic bonds form between R groups containing amino and carboxyl groups
-hydrophobic interactions that occur between R groups that are non polar. Such R groups are hydrophobic so tend to avoid water if possible. If the protein is in a typical watery environment inside the cell, then the hydrophobic R groups tend to come together excluding water.
How are the R groups that are hydrophobic and hydrophilic present in a tertiary structure?
The R groups are typically oriented towards the center of the proteins facing away from the watery environment, with the hydrophilic R groups surrounding them and pointing towards and in contact with the watery environment
How are the R groups that are hydrophobic and hydrophilic present in a tertiary structure?
The R groups are typically oriented towards the center of the proteins facing away from the watery environment, with the hydrophilic R groups surrounding them and pointing towards and in contact with the watery environment
What is the quarternary structure?
The three dimensional arrangement of two or more polypeptides or of polypeptide and non protein component such as haemoglobin
How is hemoglobin an example of protein with quaternary structure?
It has four polypeptide chains
