proteins (biomols) Flashcards
what elements make up proteins
carbon, hydrogen, oxygen, nitrogen, and soemtimes sulphur
what monomers make up proteins
amino acids
describe structure of an amino acid
amino group (NH2) and carboxyl group (COOH) and r group
how many diff amino acids are there
20, each carrying a different R group
how many amnio acids are non essential, conditionally essential, essential
5=non essential
6= conditionally essential
9=essential
what reaction is needed to join amino acids
a condensation reaction
what is a dipepetide
2 amino acids joined tg
What is a polypeptide
Many amino acids joind together
How do amino acids join together
Its a reaction between the amino group of 1 amino acid and the carboxyl group of another amino acid. As it is a condensation reaction the H20 is lost
What is the bond between amino acids
Peptide bonds
What enzyme is involved in joining amino acids together
Peptidyl Transferases
Where are protein mades
ribosomes
How do you turn dipeptide back into amino acids
Do a hydrolysis reaction
When does a polypeptide become a functional protein
When polypeptide chains twist and fold into different shapes
What is the primary structure of a protein
This is the precise number and sequence of amino acids in the polypeptide chain
How is the precise number and sequence of amino acids in a polypeptide chain determined
It is detemined by the genetic code in the DNA
Describe the structure of a polypeptide chain
At one end of the polypeptide, theres a carboxyl(COOH) group and at the other end of the chain there will be an amino/NH2 group sticking out.
What is the secondary structure of a protein
The hydrogen/oxygen/nitrogen in the polypeptide primary structure interact (not the R- groups) to form hydrogen bonds. holding the structure in a secondary shape. Hydrogen bonds form at various points along the polypeptide chain, pulling the chain into regularly arranged shapes - either ALPHA HELIX or BETA-PLEATED SHEET
What is a tertiary structure of a protein
This is how the protein folds up into its specific 3D shape. Again, this is only involves ONE POLYPEPTIDE. This involves the R-GROUPS of different amino acids in the secondary structure interacting with each other when they are close enough to do so.
When do hydrogen bonds form in the tertiary structure
These will form whenever there are 2 R- groups close together with the following atoms; one with a slightly positive hydrogen atom, and one with a slightly negative oxygen atom
When do ionic bonds form in the tertiary structure
These will form when oppositely charged R-groups are positioned close together in the amino acid chain
When do disuphide bonds form in the tertiary structure
These will form whenever there are 2 CYSTEINE amino acids close together - these R- groups contain SULPHUR atoms, and when 2 are close together, they form a strong bond.
What is the quaternery structure of a protein
Quaternery proteins have more than one polypeptide joined together. Quaternery structures are held together by the same types of bond that hold together the tertiary structures.
What are two quaternary structure proteins
Collagen and Haemoglobin
What is the structure of collagen
Collagen is a long rigid structure in which three alpha chain polypeptides are wound around one another in a triple helix
What is the structure of Haemoglobin
Haemonglobin is made from four polypeptides , two alpha, two beta. Each chain has an iron containing “HAEM” group, which pick up O2.
How is it possible to have thousands of different proteins with all different shapes
The sequence of amino acids in the chain determines how the chain will fold up to makee protein
What is the test for proteins
Biuret test
Two centimetres of sample and two centimetres of biuret
If protein is present it will change from blue to purple
What are the characteristics of globular proteins
- compact, water soluble, usually spherical
-hydrophilic R group, on the outside of thr protein = protein soluble in water - easily transported around organism
- usually have metabolic roles (hormones, enzymes, transport proteins
What are the three examples of globular proteins
-Haemoglobin
-Insulin
-Amylase
What is haemoglobin and what is its structure
Haemoglobin is made from 4 polypeptide chains joineed together.
It carries oxygen around the body in RBC
Its known as a conjugated protein - this means its a protein with a non-protein group attached
Non - protein = prosthetic group
Each of the four polypeptide chains in haemoglobin has a prosthetic group called haem. Haem group contains iron, which oxygen binds to.
What is insulin and what is its structure
Insulin is a hormone secreated by the pancreas that regulates blood glucose level.
It consists of two polypeptide chains which are held together by disulfide bonds. When they are in the pancreas, six of these molecules bind together to form a large, globular structure
What is amylase and what is its structure
Amylase is made from one polypeptide chain twisted and folded.
Amylase is an enzyme that catalyses the breakdown of starch in the digestive system. The secondary structure of this protein contains both sections of alpha helix and beta-pleated sheets.
What are the characteristics of fibrous proteins and why do they have these characteristics
- long,thin structures
-insoluble in water (as they have small hydrophobic R group)
-metabolically inactive
-often have structural roles
-strong
They have these characteristics because they contain a limited range of amino acids and have a repetitive primary sequence.
Why are fibrous not water soluble
They contain alot of amino acids with small hydrophobic R- groups
What are three examples of fibreous proteins
Keratin/Elastin/Collagen
What is the structure of Keratin
It is strong and inflexible. This protein is made from two parallel alpha helices twisted arond each other.It has alot of cysteine( the sulphur containing amino acid). this results in strong disulfide bonds forming strong, inflexible and insoluble
What determines the flexiblity of Keratin
The amount of disulfide bonds. Fewer bonds = more flexible.
What is Elastin and its structure
Its a fiberous proteins found in elastic fibres in the walls of blood vessels and surrounding the alveoli. Elastin is made up of stretchy proteins fibres called tropoelastin. Tripoelastin has the ability to stretch and recoil.
What is collagen and what is its structure
Its a fibreous protein.Its a connective tissue found in skin, tendons, ligaments and the nervous system. There are a number of different forms but all are made up of three polypeptides wound together in a long and strong rope like structure. Like rope, collagen has flexibility. Many of these triple helices then form cross bridges between each other & join to form collagen fibrils, then many of these join to form collagen fibres.
What level of protein structure do keratin/elastin/collagen all show
They’re all quarternary protein structures, made from more than one polypeptide chain.
Computer modeling systems that predict the structure of a protein base on the amino acid sequence. What are the two modeling systems called
AB initio protein modeling; the computer interprets the phscial & electrical prpoerties of the atoms of each amino acid present. It then uses the infomation to predict the possible outcomes in terms of the secondary & tertiary structure of the final protein. Sometimes these several possible outcomes!
Comparative protein modeling/protein threading; this scans amino acids sequences against a daata base of known protein structures & produces models of what the final structure of the protein might be. Again, there may be more than one possible outcome.
