proteins

Question 1

homomeric proteins
heteromeric proteins

Answer 1

proteins that contain copies of the same polypeptides
proteins that are made up of different polypeptides

Question 2

the alpha amino acid structure is common to all amino acids except?

Answer 2

Proline

Question 3

features of an amino acid

Answer 3

the carboxyl group
amino group
hydrogen
a variant(side chain)

Question 4

which side do we start from when naming amino acids?

Answer 4

the side closest to the alpha (chiral) carbon atom

Question 5

what is the variant group of glycine?

Answer 5

a hydrogen atom

Question 6

describe the structure of proline

the function of the cyclic structure in proline

Answer 6

the side chain is bonded to the alpha-amino nitrogen

it induces bends in the resulting polypeptide

Question 7

oxidization of the SH group of a cysteine means?

the SH groups of two cysteines can be oxidized to form a dimer, which contains a covalent cross-link called

Answer 7

a hydrogen atom is lost from the group

a disulfide bond

Question 8

features of amino acids with an acidic side chain

Answer 8

hydrophilic
negatively charged
polar
they have an extra carboxyl group

Question 9

features of amino acids with basic side chains

Answer 9

hydrophilic
polar
positively charged

Question 10

what is the function of histidine, and where is it found

Answer 10

helps to catalyze the making and breaking of bonds
it is often found in enzyme-active sites

Question 10

what is meant by a physiological pH?

what is special about histidine when it is at physiological pH

Answer 10

refers to the pH that is typical and optimal for the normal functioning of living organisms

it can switch between being positively charged and neutral

Question 11

state the features of cysteine that make it special

Answer 11

it is reactive, as it has the sulfhydryl group

Covalently links to other cysteine residues to form a disulfide bridge

Question 11

state the features of Proline that make it special

Answer 11

it’s amino group is part of a ring structure

it lacks hydrogen bonds and therefore does not interact well in secondary structures

hydrophobic

produces kinks or hinges in proteins

Question 12

the R group of glycine

is there a chiral carbon in glycine?

Answer 12

H

no, because, none of the carbons in glycine are bonded to four different atoms or molecules

Question 13

what is the feature of a D-alpha amino acid

what is the feature of a L-alpha amino acid

Answer 13

it presents the NH2 group on the right side of the asymmetric-carbon

it presents the NH2 group on the left side of the asymmetric-carbon

Question 14

of what optical configuration is the amino acids found in human proteins

Answer 14

the L-configuration ( they are L-alpha amino acids)

Question 15

can amino acids absorb visible light?
what color are they consequently?

Answer 15

no, they cannot, and are therefore colorless

Question 16

what is special about amino acids with aromatic side chains in regard to their spectral properties

at what wavelength do aromatic amino acids possess this special property

Answer 16

they have a characteristic UV absorption and therefore allow protein concentration to be spectroscopically estimated

280nm

Question 17

how many aromatic amino acids are there?
name them

Answer 17

three
Phenylalanine
Tyrosine
Tryptophan

Question 18

is proline an aromatic amino acid

Answer 18

no, because it does not have an aromatic ring structure

Question 19

hydroxylation of amino acids

importance of hydroxylation

Answer 19

refers to adding hydroxyl groups to amino acids, typically to their side chains

they stabilize collagen fibres through hydrogen bonds(more H bonds)
increases the polarity of the amino acid
makes amino acid more hydrophillic

Question 19

what can hinder the hydroxylation of amino acids in humans, and what effect would this have on the person

Answer 19

vitamin C deficiency

could cause scurvy

Question 20

methylation of amino acids

Answer 20

refers to adding a methyl group onto an amino acid

Question 21

importance of histone methylation

Answer 21

it regulates gene expression (genes closer together, so less expressed)

Question 22

is which protein is N-methyllysine found

Answer 22

myosin

Question 23

carboxylation of amino acids

Answer 23

adding a carboxyl(COO-) group to an amino acid

Question 24

the effect of vitamin K deficiency

Answer 24

hinders the carboxylation of glutamate, causing clotting problems and hemorrhage

Question 24

phosphorylation of amino acids

Answer 24

the addition of phosphate groups to amino acid residues

Question 24

in eukaryotes, proteins may be phosphorylated at which amino acid residues

Answer 24

serine
tyrosine
threonine

Question 24

zwitterions

Answer 24

A zwitterion (also known as an inner salt or dipolar ion) is a molecule or chemical species that contains both positive and negative electric charges within the same molecule, resulting in a net charge of zero

Question 25

at physiological pH, amino acids exist as ……………….. ions

Answer 25

dipolar (zwitterions)

Question 25

the ionization state of an amino acid varies with pH, true or false?

what is typically the net charge of amino acids at acidic pH?

Answer 25

true

+1

Question 26

what is typically the net charge of amino acids at basic pH?

Answer 26

-1

Question 27

amino acids are ……………. linked via peptide bonds

Answer 27

covalently

Question 28

are peptide bonds ever charged?

Answer 28

no, the peptide bond is uncharged at any physiological pH of interest.

Question 29

define these structures of proteins;
Primary

Secondary

Tertiary

Quaternary

Answer 29

the sequence of amino acids in polypeptide chain

Simple structures resulted from arrangements in space between adjacent amino acids

The complex 3D shape of the protein

this is when there is more than one polypeptide chain in a protein structure

Question 30

knowledge of the primary structure of an amino acid can help predict

Answer 30

Final 3D structure of a polypeptide
Mechanism of action of a protein
Associated pathologies of a protein

Question 31

forms of the secondary structure of a protein

Answer 31

alpha helix
beta pleated sheets

Question 32

facts about the alpha helix form of polypeptides

Answer 32

It is a spiral structure, consisting of a tightly packed, coiled polypeptide backbone core.

The side chains of the component amino acids extend outward.

Stabilized by hydrogen bonds.

Each turn of an α-helix contains 3.6 amino acids.

Question 33

bonds present in the tertiary structure of amino acids

Answer 33

disulfide bonds
hydrogen bonds
ionic bonds
London forces
hydrophobic bonds

Question 34

examples of proteins with a quaternary structure

Answer 34

haemoglobin
collagen

Question 35

factors that can cause proteins to denature(change in the shape of the active site of a protein)

can proteins ever be renatured (i.e is denaturation reversible)

Answer 35

extreme pH
extreme temperatures
extreme levels of specific chemicals like urea

yes, but this is rarely done