Proteins Flashcards
What is the monomer for proteins?
Amino acids
What are the elements that make up proteins?
Carbon, Hydrogen, Oxygen, Nitrogen and sometimes Sulphur
How many proteins are proteinogenic?
20
What are the difference parts of an amino acid?
- An R-group
- An amino group
- A carboxyl group
What is the R-group?
It is a side chain added on to the amino acid
What is the bond between 2 amino acids?
It is a peptide bond with the C, O, N and H
What is the primary structure?
The sequence of amino acids are joined in a protein chain
What is the average chain of a primary structure?
100 amino acids
What are the bonds in the primary chains?
Peptide chains
What is the secondary structure?
It is the initial folding of singular polypeptide chains
What is the alpha helix structure?
The alpha helix is a secondary structure in a helix structure with 36 amino acids and 10 turns of the helix,
It has H bonds
Left hand is anticlockwise and right is clockwise
What are the bonds holding the secondary structures together?
Peptide bonds
Hydrogen bonds between the -NH groups and the -CO of another 4 places ahead the chain
What is the beta pleat structure?
Some fold slightly in a zig-zag structure, where the chains folds over in itself, forming a sheet like structure
It has H bonds
What is the tertiary structure?
This is when the coils and pleats start to fold, along with the areas of straight chains of amino acids.
It has a very specific shapes which are held together by bonds between close amino acids.
What is the tertiary structures shape?
Spherical
Supercoiled
What is the quaternary structure?
It is multiple polypeptide chains are arranged to make the complete protein molecule.
What holds a quaternary structure together?
Peptide bonds Hydrogen bonds Ionic bonds Disulphide links Hydrophilic and hydrophobic interactions
What holds a tertiary structure together?
Peptide bonds Hydrogen bonds Ionic bonds Disulphide links Hydrophilic and hydrophobic interactions
Where are the hydrogen bonds?
They are between an amino group and carboxyl group or between polar areas of the R- groups
Where are the ionic bonds?
Form between the carboxyl and amino groups that are part of R-groups. These ionise into NH3+ and COO- groups. The positive and negative ions cause the ionic bonds
Where are the disulphide links?
In between the R-groups of the amino acids cysteine contains sulphur, disulphide bridges are formed between the R-groups of 2 cysteine to make strong covalent bonds.
Where are the hydrophilic and hydrophobic interactions and why do they happen?
They happen when the R-groups are hydrophilic or hydrophobic.
If the R-group is hydrophilic it will mean it will be near the water
If the R-group is hydrophobic it will mean it will be away from the water
What are the features of globular proteins?
Compact
Roughly spherical
It is soluble
How is a globular protein formed?
It is when the proteins fold so hydrophilic R-groups are away from the water and the hydrophobic R-groups are close to the water
What is a globular proteins used for?
Used in chemical reactions
Immunity
Muscle contractions
What is insulin?
- It is a globular protein
- It is a hormone that regulates glucose concentration in the blood
- It has a secondary structure of helixes and is folded into a tertiary structure
- It is water soluble
- It has a specific shape for its function
What is the structure of haemoglobin?
- It is a globular protein
- It has 4 subunits that are wrapped in a haem group.
- Each haem group has an iron inside it
- It has 2 alpha and 2 beta subunits
- It is a conjugated protein
What is myoglobin?
-It is a globular protein
What is pepsin?
- It is a globular protein
- It is an enzyme to break down proteins in the stomach
- It is a symmetrical tertiary structure
- It has mostly acidic amino acids so it is stable in the stomachs acidic conditions
- The tertiary structure is held together by hydrogen bonds and 2 disulphide bridges
What is catalase?
- It is a globular protein
- It is in a quaternary protein shape
- It as 4 haemprosthetic groups
- It contains Iron in the prosthetic groups
- It breaks down H2O2 which is a toxic byproduct of metabolism, so the catalase gets rid of it
How is a fibrous protein formed?
- It is a long insoluble chain because of the many hydrophobic R-groups in the primary structure
- It has a limited range of amino acids with small R-groups
- They make long strong molecules that aren’t folded into complex structures
- It is strong, tough and fibrous
What is a fibrous proteins used for?
It has mostly structural uses
Where is collagen found?
- Used in connective tissue
- Found in skin, tendon and ligaments
- Made up of 3 polypeptides wound in a long and strong rope-like structure
- It is flexible
What is keratin?
- Found in hair, nails, skin
- Large portion of sulphur-containing amino acids, so there are many disulphide bonds
- The disulphide bonds make the material strong an inflexible
- The more rigid the structure the more disulphide bonds there are
where is elastin used
-In the walls of blood vessels and in the alveoli of the lungs
-It gives the vessels and alveoli flexibility to expand and retract
It is a quaternary protein mede from stretchy molecules and tropoelastin
What is the structure of collagen?
- peptide bonds , between amino acids / in polypeptide
- every 3rd amino acids is , same / glycine
- coil / twist / spiral / helix
- left-handed (helix)
- glycine / small R group , allows closeness / twisting (of polypeptide chains)
- three polypeptide chains
- hydrogen / H , bonds between (polypeptide) chains
- no / few, hydrophilic (R) groups on outside (of molecule)
- (adjacent molecules joined by) crosslinks
- crosslinks / ends of molecules , being staggered
- fibril
What is the structure of haemoglobin?
-globular
-hydrophobic (R) groups on inside / hydrophilic
(R) groups on outside
-4 , chains / sub-units / polypeptides
-idea that subunits are (two) different types
-α / alpha , helix
idea that proportion of glycine similar to that, of other amino acids / in other proteins
What does the iron do in a haemoglobin?
haem group reversibly binds with oxygen
What is a chain of amino acids called?
Polypeptide chain
How many oxygen atoms can 1 haemoglobin bind to?
4 oxygen atoms in each haemoglobin
