Proteins part 1 Flashcards
What is a protein?
A protein is a macromolecule consisting of
amino acids arranged in a particular
structure that enables it to carry out a
specific function in a particular context
What are the two types of proteins and their characteristics?
Proteins may be structural (e.g. actin
‘scaffold’ within a cell or keratin in skin) or
functional (e.g. catalytic function of
enzymes or antibodies in immune defence)
Steps before protein synthesis (basic )?
DNA is both a blueprint and instruction
manual for different proteins
It tells cells how to make messenger
RNA (mRNA)
TRANSCRIPTION
mRNA is used by the cell as a code to
make chains of amino acids
TRANSLATION
These chains go on to form proteins!
What are the nucleotides that make up DNA ?
adenine, cytosine, guanine and thymine
Nucleotides that make up mRNA?
adenine ,cytosine, guanine and uracil
Describe amino acid structure?
always a central carbon atom
always amine group (NH2) on left
carboxylic acid group on the right
always a hydrogen attached to second carbon
has a variable r group
What does an amino acid being chiral mean?
distinct orientation in space despite common chemical constitution
-true for all except glycine (R is H )
Why are amino acids affected by acid-base?
Have COOH - can lose hydrogen ions
amine group- can behave like a base
What happens when amino acids are subjected to pH?
may take on positive or negative charge
What happens to AA in low pH?
Lots of H+ ions
carboxylic acid group takes up hydrogen and becomes slightly positive
cation
What happens to AA in high pH?
not many h+ ions
carboxylic acid loses hydrogen and becomes slightly negative
anion
Amino acids at pH 7?
two charges
What are aliphatic amino acids?
R group consisting of hydrocarbon chains
increasing long hydrocarbon - non polar properties
What are aromatic amino acids?
r group consisting of hydrocarbon ring
Why are there sulphur-containing amino acids?
The presence of sulphur allows interactions called disulphide bridge to form
What are di- sulphide bridges?
Covalently bonded linkages that occur between two sulphur containing amino acids and help increase strength
What are the acidic amino acids?
aspartate and glutamate
What are the basic amino acids?
- Lysine
- Hisitidine
- Arginine
What are polar amino acids?
Can carry charge at the end of R group
What is the miscellaneous amino acid and why?
proline , unusual ring shape- which is very difficult to break
Describe primary structure?
The sequence in which amino acid monomers are
bonded together to form a polypeptide chain
What is a peptide bond?
amine and carboxylic acid groups both react together
dehydration reaction
What is secondary structure?
This is the 3D spatial arrangement of amino acids
located near each other in the polypeptide chain
Relies on hydrogen bonding between the amino
hydrogen of one amino acid and the carboxyl oxygen of another amino acid in the same chain
What are the types of secondary structure?
alpha helix
and beta pleated sheet
Two examples of proteins with spiral alpha helices?
troponin - released from myocardium
myoglobin
What do troponins tell us?
elevations in troponins can help determine if a patient has had a myocardial infarction.
What are porin proteins?
porin proteins act as channels that allow water into cells
What is the tertiary structure?
Results when functional groups of ‘R’ chains of amino
acids in the polypeptide chain interact with one another
Van der Waals, ionic, hydrogen, disulphide and
hydrophobic interactions can all be involved
Functional proteins exist as, at least, a tertiary structure
What is the quaternary structure?
Sometimes several polypeptides interact with one
another to form a quaternary structure
Describe structure of haemoglobin?
haemoglobin contains four highly-folded
polypeptide chains and four iron-containing heme
groups with one group tucked within the interior of
each folded polypeptide subunit
What is denaturation?
Occurs when a protein’s chemical bonds are
disrupted (possibly destroyed) within its
secondary and tertiary structure
Biological functionality is LOST
Denaturation processes are rarely strong enough
to break the primary structure of individual
peptide bonds, so the primary structure remains
the same even after denaturation
