3.1.4 proteins Flashcards
3.1.4 proteins
in terms of monomers and polymers what are proteins
poteins are polymers and are made of monomers called amino acids
draw an amino acid representing the R group with an R
should have a carboxilic acid group , amine group and an alpha carbon with an R group attatched to it
how many diffrent R groups are there , and also how many diffrent amino acids are there
20
what bond is formed between amino acids and between which groups
polypeptide bond
between the carboxilic acid group and the amine group
what type of reaction is need for a polypeptide bond
condensation reaction
what are the four levels of structure of proteins
primary (found in all proteins)
secondary (found in all proteins)
tertiary (found in some proteins)
quarternary (found in some proteins)
describe what primary structur is
The sequence (and number) of amino acids in the polypeptide chain is known as the primary structure, linked by peptide bonds only
Determines shape and function of protein
describe what a secondary structure is
The chains fold into two different regular shapes – alpha helices (most common) and beta pleated sheets (less common).
H-bonding forms between the –CO and the -NH of adjacent amino acid. No R groups are involved.
These are found in all proteins (because all proteins have same backbone) and some proteins will have both helices and pleated sheets within their structure.
Secondary structure results in the R groups sticking out to the side ready to bond forming the tertiary structure.
describe / draw out the structue of beta pleated sheets and alpha helicies
check with the internet ,
but one should form neatly crumpled sheets and one should form a helicies
why are beta pleated sheets formed
The sheet is not flat but pleated because of the carbon having tetrahedral angles
describe what a tertiary structure is
H-bonds (weak)
Ionic bonds (stronger and vulnerable to changes in pH)
Disulphide bridge (very strong, covalent bonds)
and hydrophobic interactions
describe what a quaternary structure is
Where more than one (2 or more) polypeptide chains combine to form complexes
Joined by bonds similar to those in the tertiary structure
Only some proteins exhibit quaternary structure
For example, Haemoglobin consists of 4 polypeptide chains held by disulphide bridges and a non protein prosthetic group.
what are the two main types of quarternary proteins
fibrous
globular
describe the distinct featurs of fibrous proteins
Fibrous proteins such as collagen have structural roles, they consist of polypeptide chains linked in parallel chains or sheets with numerous cross links to make fibres
often have simular repeating units
collogen is used to link muscle of bone and to provide strength and flexibility.
describe the distinct featurs of globular proteins
Globular proteins such as enzymes perform metabolic functions. Their shape is compact and folded - spherical.
e.g antibodys
how do you test for proteins
add a solution that you wish to test in equal amounts of NaOH and copper (II) sulphate CuSO4
(could also say Biuret reagent )
purple means that theres proteins
while
light blue means theres no proteins
info card (read and then try to recite as much as you can )
Fibrous :
Have structural functions e.g. keratin a resistant protein found in skin cells helps to prevent the entry of pathogens
The polypeptide chain has regular repetitive sequences and is coiled into a helix or pleated sheet - secondary structure. Sheets provide flexibility to the molecule
Structure maintained by H bonding
Parallel polypeptide chains cross linked to form long fibres, which provide strength
Stable ( less effected by pH changes and tempreature)
Usually insoluble in water (external R groups are non polar)
info card (read and then try to recite as much as you can )
Globular :
Have metabolic functions e.g. enzymes such as amylase, hormones such as insulin
Polypeptide chains have irregular sequences of amino acids that form secondary and tertiary structures and have a specific 3d shape (tightly folded to form a spherical shape)
Structure maintained by H bonding, ionic bonds and disulphide bridges between atoms in R groups. Also hydrophobic bonds as their non polar R groups point inwards
Surface of the molecule has depressions in it into which other molecules can fit
Relatively unstable - 3d structure can be affected by temp and pH
Usually soluble in water (external R groups are polar)
what are the main functions of proteins
Transport
Movement
Sensitivity and coordination (nervous system and the hormone system)
Reproduction
Protection (immune system)
globular vs fibrous :
shape
GLOB :
messy rough
FIB :
long strands
globular vs fibrous :
amino acid sequence
GLOB :
irregular and wide range of R groups
FIB :
repeated with limited range of R groups
globular vs fibrous :
function
GLOB :
enzymes , hormones , immuno globlins , transport molecules
FIB:
structure
globular vs fibrous :
examples
GLOB :
haemoglobin , enzymes ,antibodys , insulin
FIB :
kreatin , collogen , fibrin
globular vs fibrous :
solubility
GLOB :
solubule in water generaly
FIB :
insoluable in water generaly
