proteins Flashcards
what is a peptide bond
formed when two amino acids are joined in a condensation reaction
what is a dipeptide
a peptide composed of two amino acids
properties of an amino acid
has an:
-amino group- H-N-H
-hydrogen atom
-carboxyl group O=C-OH
-an R group
what type of bond is a peptide bond
covalent
what happens during condensation of amino acids
-removal of hydroxyl group (H2O)
-a bond between crabon and nitrogen is formed
-forms a peptide bond and a dipeptide molecule
function of proteins
-growth and repair
-enzymes
-hormones
what is the primary structure of a protein
the sequence of amino acids join by peptide bonds
what is the secondary structure of a protein (alpha)
has a helix structure held by hydrogen bonds
what is the secondary structure of a protein (beta)
-folds in a zig-zag structure known as a beta pleated sheet
what is the tertiary structure of a protein
when the coils/folds start to form, this causes the R groups of different amino acids to be closer together and they start to form interactions
what types of interactions are formed in tertiary structure
-hydrogen bonds
-ionic bonds
-disulphide bridge
-hydrophobic and hydrophillic interactions
types of proteins
fibrous and globularpro
properties of a fibrous protein
-polypeptide chains form long twisted strands linked together
-insoluble in water
-stable structure
-strength gives structural function (collagen in bones)
properties of a globular protein
-polypeptide chains roll up into a spherical shape
-soluble in water due to position of hydrophillic and hydrophobic R group
-have specific shapes to take up a function
-relatively unstable
-metabolic functions (enzymes)
examples of fibrous proteins
collagen, keratin and elastin
function of collagen
-found in artery walls to prevent bursting in high pressure
-found in tendons, cartilage, connective tissues
structure of collagen
-made of repeating sequences of amino acids which form a spiral structure
-made from 3 polypeptide chains wound together like a rope
-hydrogen bonds hold chains together
-flexible but doesn’t stretch
function of keratin
-found in fingernails, hair, fur, feathers
-provides mechanical protection
-waterproof
-impermeable barrier to infection
-hard and strong
structure of keratin
-rich in cysteine
-many disulphide bridges between polypeptide chains
-hydrogen bonds make molecule strong
function of elastin
found in lungs, living blood vessels, skin
-helps blood vessels stretch and recoil
structure of elastin
-cross-linking and coiling make the structure strong and flexible
-recoils after being deformed
-hydrogen bonds
examples of globular proteins
haemoglobin, insulin and pepsin
function of haemoglobin
-a haem group found on the outside of the chain, when oxygen binds to the iron in the haem group- oxygenates the haemoglobin
structure of haemoglobin
-Quaternary structure, 4 polypeptides
-two alpha globin and two beta globin polypeptide chains- each having their own tertiary structure
-has a prosthetic group where oxygen binds to (contains iron ions)
-haem group found on the outside of the chain
-can change shape
function of insulin
-binds to glycoprotein receptors on the outside of muscle and fat cells to increase uptake of glucose which decreases blood glucose concentration
structure of insulin
-two polypeptide chains
-A chain- begins with an alpha helix
-B chain- begins with a beta chain
tertiary structure joined by disulphide links
-R groups on the outside so it is soluble
-specific fixed shape
function of pepsin
digests proteins in stomach
what is a conjugated protein
a protein with a prosthetic group bound to it attached by hydrogen, covalent and ionic bonding
what does a disulphide bond form between
between the R groups of two amino acids that contain sulfur
what does an ionic bond form between
between R groups of different amino acids
