3.6, 3.7, Proteins, Types of Protein Flashcards
What are the properties of each amino acid determined by?
Their Variable group
Describe the basic structure of an amino acid.
-There are 3 groups in an amino acid.
-One Amine group (NH2)
-One Carboxyl group (COOH)
-One Variable Group (R)
Are amino acids soluble or insoluble?
-Amino acids are soluble in water, and form polar ions when added to water, some R groups are non-polar.
What are peptides?
-Short chains made up of amino acid molecules
What are proteins made up of?
Proteins consist of one or more polypeptides arranged as complex macromolecules, and all have specific biological functions
What elements do all proteins contain?
Carbon, Hydrogen, Oxygen and Nitrogen
What group determines which amino acid it will be?
The R group.
How many different amino acids are there?
20
How is a dipeptide produced?
When the amine group of one amino acid and the carboxyl group of another react with eachother in a condensation reaction
What type of bond connects two amino acids together?
A peptide bond
What catalyses the reaction between two amino acids?
Peptidyl transferase
What type of reaction is it when polypeptide is broken down?
Hydrolysis reaction.
How do polypeptides form proteins?
Different R groups of the amino acids making up a protein interact with eachother, forming different types of bond.
What determines the shape of a protein?
The sequence of the amino acids
What does the shape of a protein determine?
Its function
How many levels of protein structure are there? And what are their names?
4, Primary, Secondary, Tertiary, Quarternary
What is the Primary Structure of a protein?
-The sequence in which the amino acids are joined.
What are amino acids joined by in a polypeptide chain?
Peptide bonds
What directs the sequence of amino acids?
Information carried within DNA
What does the particular amino acids in a sequence influence?
How the polypeptide folds to give the protein’s final shape.
What is the Secondary Structure of proteins the result of?
Hydrogen bonds pulling polypeptide chains into different shapes.
How is the Secondary Structure formed?
-The oxygen, nitrogen and hydrogen atoms of the repeating structure of the amino acids interact.
-Hydrogen bonds form within the amino acid chain, or between polypeptide chains, and pull the structures into one of two shapes.
What are the two shapes found in secondary structure?
Alpha Helix or Beta Pleated Sheet
Do all proteins have a secondary structure?
Yes
True or false: Proteins can only have one shape in their structure
False, proteins can have both alpha helixes AND beta pleated sheets in their structure, but the helix is the most common of the two
How do proteins form the secondary structure of an alpha helix?
Hydrogen bonds form WITHIN an amino acid chain, pulling it into a coiled shape, which is the alpha helix.
How do proteins form the secondary structure of a beta pleated sheet?
-Hydrogen bonds join SEPARATE polypeptide chains that lie parallel to eachother.
-The pattern formed by the individual amino acids causes the structure to appear pleated (forming the shape of a beta-pleated sheet)
Where do the Secondary Structures form?
Regions along long protein molecules
What is Tertiary Structure?
The folding of a protein into its final shape, that often involves sections of secondary structure.
How does Tertiary Structure form?
The folding of sections of proteins into their secondary structures brings R groups of different amino acids closer together, so they are close enough to interact and further foldings of these sections occurrs.
What are the different types of interactions between R-Groups in Tertiary Structure?
-Hydrophobic and Hydrophilic interactions
-Hydrogen bonds
-Ionic bonds
-Disulfide bonds/bridges
What are hydrophilic and hydrophobic interactions in Tertiary Structure?
Weak interactions between polar and non-polar R groups
What are hydrogen bonds in Tertiary Structure?
The weakest of the bonds formed
What are ionic bonds in Tertiary Structure?
Stronger than hydrogen bonds, and formed between oppositely charged R groups. Vulnerable to changes in pH
What are disulfide bonds in Tertiary Structure?
Covalent, and the strongest of the bonds.
Only formed between R-groups that contain sulfur atoms, between adjacent cysteine molecules.
What does Tertiary Structure produce?
A variety of complex-shaped proteins, with specialised characteristics and functions.
What is Quarternary Structure?
A result of the association of two or more individual polypeptide chains.
What makes Quarternary Structure similar to Tertiary Structure?
The interactions between the subunits are the same.
What makes Quarternary Structure different to Tertiary Structure?
In Tertiary Structure, the subunits in the interactions are amino acids in the same protein molecule. In Quarternary Structure, the subunits are different protein molecules.
What are the subunits in Quarternary Structure?
Individual proteins
True or false: Protein subunits have to be different in Quarternary Structure
False, they can be identical OR different
What types of subunits do Enzymes contain?
Two identical proteins
What types of subunits does Insulin contain?
Two different proteins
What types of subunits does Haemoglobin contain?
4 subunits, made up of 2 sets of 2 identical proteins
Is a protein the same thing as a polypeptide chain?
Yes
What polypeptide chains does haemoglobin contain?
Two alpha subunits, two beta subunits. ALSO a non-protein group known as a PROSTHETIC GROUP
What is haemoglobin required for?
Oxygen transport in the blood
Describe the group in Haemoglobin
It is a non-protein group known as a PROSTHETIC GROUP, called HEME, that contains Iron 2+. In one molecule of Haemoglobin, there are 4 FE2+ ions present.
What 3 groups can proteins be classified into?
Globular, conjugated and fibrous
What determines what role the protein will play in the body?
The tertiary and quarternary structure of the protein.
What is the general shape of globular proteins?
Compact, spherical shape
What is the name for a protein without a prosthetic group?
Simple protein
Are globular proteins water soluble?
Yes
Why are globular proteins water soluble?
Because the Amino acids with hydrophobic R groups are on the inside of the sphere, and amino acids with hydrophilic R groups are on the outside. This is a feature of tertiary structure.
Are globular proteins affected by temp change and pH?
Yes, they denature at high temperatures and extreme pH.
Are globular proteins generally reactive or unreactive?
Reactive
Are globular proteins repetitive or not?
Not, there are few repetitive amino acid sequences
Give an example of a globular protein.
Insulin
What is insulin?
A globular protein involved in the regulation of blood glucose concentration. It is soluble and precisely shaped
Why are globular proteins precisely shaped?
So that they can bond to complementary receptors on the plasma membrane of cells
State the features and properties of globular proteins.
-Precise 3D shape
-Spherical
-Soluble
-Simple protein
-Compact
-Reactive
-Affected by changes in pH and temp.
What is produced when a protein and a carbohydrate react?
A glycoprotein
What is produced when a protein and a lipid react?
A lipoprotein
What are conjugated proteins?
Globular proteins that contain a non-protein component (or prosthetic group)
What is a prosthetic group?
A non-protein component
List some of the different types of prosthetic groups.
Lipids, carbohydrates, metal ions, molecules derived from vitamins
What is the name of the prosthetic group that both Catalase and Haemoglobin contain?
Haem group
What is haemoglobin?
A red, oxygen-carrying pigment found in red blood cells. Contains a haem group, containing Fe2+ ions that can combine reversibly with an oxygen molecule, which enables it to transport oxygen around the bloodstream.
What enables haemoglobin to carry oxygen around the bloodstream?
The haem group which contains Fe2+ ions that can combine reversibly with an oxygen molecule
What is Catalase?
An enzyme that catalyses the breakdown of hydrogen peroxide.
What is hydrogen peroxide?
A common byproduct of the metabolism, damaging to cells and cell components if allowed to accumulate.
What are fibrous proteins?
Proteins formed from long, insoluble molecules that are strong.
Are fibrous proteins soluble?
No.
What makes fibrous proteins insoluble?
Contains a high proportion of amino acids with hydrophobic R groups, making them non-polar and therefore insoluble in water.
Do fibrous proteins have a repetitive structure? Why?
Yes, because there is a limited range of amino acids, usually with small R groups.
Why do fibrous proteins have very organised structures?
Because there are a limited range of amino acids, usually with small R groups
What are the general properties of Fibrous proteins?
Insoluble in water, flexible, unreactive, high tensile strength, not affected by changes in pH or temp.
Are there crosslinkages in fibrous proteins? Between what?
Yes, between amino acids of adjacent polypeptide chains.
List the structures that fibrous proteins have.
Repetitive primary structure, limited secondary structure (because they are not folded into 3D shapes), very limited tertiary structure.
Give some examples of fibrous proteins.
Keratin, Elastin, Collagen
Where is Keratin present?
In hair, skin and nails
What is a large proportion of keratin made of?
The amino acid Cysteine
What determines the flexibility of keratin?
The amount of disulfide bonds in the protein strand
What type of protein is Keratin?
Fibrous protein
What type of protein is Elastin?
Fibrous protein
What type of protein is Collagen?
Fibrous protein
What is collagen?
A fibrous protein and connective tissue
Where is collagen found?
Skin, tendons, ligaments and the nervous system.
What is a key property of collagen?
Flexible
What are all the forms of collagen made up of?
3 polypeptides wound together in a long and strong rope-like structure
Where is elastin found?
Walls of blood vessels, skin, and the alveoli in the lungs
What is the role of elastin?
To give the structures it is found in the flexibility to expand when needed
What is the quarternary structure of elastin made from?
Many stretchy molecules called tropoelastin
Describe a typical fibrous protein structure
-3 long parallel polypeptide chains
-Hydrogen bonds forming cross-linkages between the chains, forming a tight triple helix.
What does lysozyme break down?
Peptidoglycan, the molecule found in the cell walls of bacterial cell walls.
