Ioe Protien Structure And Function

Front 1

protiens are the most

Back 1

The most versatile macromolecules in living systems

Front 2

they Function as: what (4)

Back 2

Function as: catalysts,
transporters,
mechanical support,
immune protection

Front 3

what do protiens control

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They also control movement, growth and development and they transmit nerve impulses

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protiens are...

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Linear polymers built from monomer units called amino acids

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contain a wide range of

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Contain a wide range of functional groups

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can interact with...

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Can interact with one another and with other biological molecules to form complex assemblies

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what type of strucutres can they have

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Can have very rigid structures or can display flexibility

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Amino acids can exist as either....

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Amino acids can exist as either L- or D- isomers, however only the L-form is found in proteins

Front 9

draw Ionization state as a function of pH of protiens

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Front 10

draw the structures of glycine and alanine

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Front 11

list all the amino acids with aliphatic side chains

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valine, leucine, isoleucine, methionine

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which amino acid has a cyclic strucutre

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proline

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which amino acids have aromatic side chains

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phenylalanine

tyrosine


tryptophan

Front 14

what are the basic amino acids

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lysine, arginine, histidine

Front 15

what do pka values represent

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pKa values represent the pH at which 50% of the molecules are ionised and 50% are not

Front 16

what do pka values depend on

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ionic strength, temperature, and the micro environment of the ionisable group

Front 17

what does protein primary structure consist of

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-carboxyl group of one amino acid joined to the -amino group of another

A series of amino acids joined by peptide bonds form a polypeptide chain

Front 18

why does a polypeptide chain have polarity

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A polypeptide chain has polarity because its ends are different

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what is taken as the beginning of a polypeptide chain

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By convention the amino end is taken as the beginning of a polypeptide chain

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The linking of two amino acids is accompanied by

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the loss of a molecule of water. The reaction requires the input of free energy

Front 21

draw a diagram for peptide bond formation

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Front 22

what doe polypeptide chains consist of

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Polypeptide chain consists of a constant backbone and variable side chains

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draw thes structure of a polypeptide chain

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Front 24

Proteins have unique amino acid sequences that are specified by

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genes

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The formation of a disulphide bond from two cysteine residues is an

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oxidation reaction

Front 26

show the formation of a disulphide bond between 2 cysteine residues

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Front 27

disulphide bonds can either be

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The disulphide bonds can be either inter- or intra-chain

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The peptide bond has considerable double –bond character, which prevents

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prevents rotation about this bond

Front 29

peptide bonds are what shape

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planar

Front 30

how are some polypeptide chains flexible

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Some of the bonds in the polypeptide backbone are capable of rotation

This freedom of rotation allows proteins to fold in many different ways

Front 31

which bonds in polypeptides have freedom of rotation

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Bonds between the amino group and the -carbon atom and between the -carbon atom and the carbonyl group are single bonds and have freedom of rotation

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The structure of each amino acid in a polypeptide can be adjusted by

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the rotation about 2 single bonds

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what is phi and what is psi

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Phi () is the angle of rotation about the bond between the nitrogen and -carbon atoms. Psi () is the angle of rotation about the bond between the -carbon and the carbonyl carbon atoms

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what is protein secondary structure

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Polypeptide chains can fold into regular structures such as:
Alpha helix
Beta sheet
Turns
Loops

Front 35

how does hydrogen bonding occur in an alpha helix

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The CO group of residue n forms a hydrogen bond with the NH group of residue n+4

Front 36

what is ferritin and what is it an example of

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Ferritin, an iron storage protein, is built from a bundle of  helices


and is an example of A largely helical protein

Front 37

how does coilin occur in the alpha helices

where are such structures found

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The helices wind around one another to form a superhelix.

Such structures are found in many proteins including keratin in hair, quills, claws and horns

Front 38

what can beta sheets be stabilised by

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Beta sheets are stabilised by hydrogen bonding between polypeptide strands

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what 2 forms can beta sheets be in

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Beta sheets can be antiparallel with adjacent β strands running in opposite directions

Beta sheets can be parallel with adjacent β strands running in the same direction

Front 40

describe the hydrogen bonding for a beta helix on an antiparralel sheet

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Hydrogen bonds between NH and CO groups connect each amino acid with a single amino acid on an adjacent strand, stabilising the structure

Front 41

describe the hydrogen bonding for a beta helix in a parallel sheet

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Hydrogen bonds connect each amino acid on one strand with two different amino acids on the adjacent strand

Front 42

a protein rich in beta sheets also contains...

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Proteins also contain loops and turns which contribute to both structure and function

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what is protein tertiary structure

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The 3-dimensional folding of polypeptide chains is referred to as its tertiary structure

Front 44

what is this folding often devoid of

in globular protiens give an e.g, what does the interior consist almost entirely of?

where are charged amino acids often found

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This folding is often devoid of symmetry

In globular proteins e.g. myoglobin the interior consists almost entirely of nonpolar residues

Charged amino acid residues are often located on the surface

Front 45

what is protein quaternary structure

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Some proteins contain more than one polypeptide chain

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what is a subunit

polypeptide chains can assemble into what type of strucutre

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Each polypeptide chain in such a protein is called a subunit

Polypeptide chains can assemble into multisubunit structures

Front 47

what may these multisubunit structures contain

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These multisubunit structures may contain many copies of the same subunit (e.g.Virus coat proteins) or they may be made of different subunits

Front 48

what is the cro protein

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The Cro protein of bacteriophage  is a dimer of identical subunits

Front 49

The amino acid sequence of a protein determines its

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The amino acid sequence of a protein determines its three dimensional structure

Front 50

Amino acids have different propensities for forming

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Amino acids have different propensities for forming alpha helices, beta sheets and beta turns

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what are polypeptides and how are they orientated

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Polypepides are linear chains oriented from amino terminus to carboxy terminus

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the properties of amino acid side chains dictate

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The properties of the amino acids side chains dictate the structure and function of proteins