Proteins Flashcards by TRISHA ANN APOLINAR

The only amino acids with secondary a-amino group

Proline

How well did you know this?

Not at all

Perfectly

Amino acid without stereocenter (not chiral)

Glycine

How well did you know this?

Not at all

Perfectly

Two amino acids with two stereocenters

Isoleucine and threonine

How well did you know this?

Not at all

Perfectly

Proposed that proteins are long chains of amino acids joined by amide bonds

Emil Fischer (1902)

How well did you know this?

Not at all

Perfectly

A short polymer of amino acids joined by peptide bond; they are classified by the number of amino acids in the chain

Peptide

How well did you know this?

Not at all

Perfectly

A molecule containing two amino acids joined by peptide bonds

Dipeptide

How well did you know this?

Not at all

Perfectly

A molecule containing three amino acids joined by peptide bonds

Tripeptide

How well did you know this?

Not at all

Perfectly

A macromolecule containing many amino acids joined by peptide bonds

Polypeptide

How well did you know this?

Not at all

Perfectly

A biological macromolecule containing at least 30 to 50 amino acids joined by peptide bonds

Protein

How well did you know this?

Not at all

Perfectly

Individual amino acid units

Residues

How well did you know this?

Not at all

Perfectly

Discovered that there is about 40% double-bonded character to the C-N bond and that a peptide bond between two amino acids is planar

Linus Pauling

How well did you know this?

Not at all

Perfectly

Pauling explained the double-bonded character to the C-N bond through the concept of _____

Resonance

How well did you know this?

Not at all

Perfectly

The amino acid at the end of the chain having the free -COO- group

C-terminus

How well did you know this?

Not at all

Perfectly

The amino acid at the end of the chain having the free -NH3+ group

N-terminus

How well did you know this?

Not at all

Perfectly

How do you read the amino acids?

Left-right (N-terminus to C-terminus)

How well did you know this?

Not at all

Perfectly

The sequence of amino acids in a polypeptide chain

Primary structure

How well did you know this?

Not at all

Perfectly

Conformations of amino acids in localized regions of a polypeptide chain

Secondary structure

How well did you know this?

Not at all

Perfectly

Examples of secondary structure

a-helix, b-pleated sheet, random coil

How well did you know this?

Not at all

Perfectly

Complete three-dimensional arrangement of atoms of a polypeptide chain

Tertiary structure

How well did you know this?

Not at all

Perfectly

Spatial relationship and interactions between subunits in a protein that has more than one polypeptide chain

Quaternary structure

How well did you know this?

Not at all

Perfectly

Antidiuretic hormone

Vasopressin

How well did you know this?

Not at all

Perfectly

Affects the contractions of the uterus in childbirth and muscles of the breast in secretion of milk

Oxytocin

How well did you know this?

Not at all

Perfectly

Differences in the structure of vasopressin and oxytocin

Vasopressin: Arg & Phe
Oxytocin: Leu & Ile

How well did you know this?

Not at all

Perfectly

A type of secondary structure in which a section of polypeptide chain coils into a spiral, most commonly a right-handed spiral

a-helix

How well did you know this?

Not at all

Perfectly

A type of secondary structure in which two polypeptide chains or sections of the same polypeptide chain align parallel to each other; the chains may be parallel or antiparallel

b-pleated sheet

In a-helix, there are ____ amino acids per turn of the helix

3.6

The six atoms of each peptide bond in a-helix lie in the _____ plane

same

The N-H groups point in the _____ direction, roughly _____ to the axis of the helix (a-helix)

same, parallel

The C=O groups point in the _____ direction, roughly _____ to the axis of the helix (a-helix)

opposite, parallel

All R-groups of a-helix point _____ from the helix

outward

A polypeptide derived entirely from alanine, where the intrachain hydrogen bonds that stabilize the helix are visible as the interacting C-O and N-H bonds

polyalanine, a-helix

In b-pleated sheet, the six atoms lie in the _____ plane

same

The C=O and N-H groups of the peptide bonds (b-pleated sheet) from _____ chains point _____ each other and in the ____ plane

adjacent, toward, same

All R-group (in b-pleated sheet) on any one chain ___ of the sheet

alternate (above, then below)

The overall conformation of an entire polypeptide chain

tertiary structure

Four ways of stabilization of tertiary structure

Covalent, hydrogen, salt bridges, hydrophobic interactions

Example of tertiary structure stabilization: formation of disulfide bonds between cysteine side chains

Covalent bonds

Example of tertiary structure stabilization: between the -OH groups of serine and threonine

Hydrogen bonding

Example of tertiary structure stabilization: the attraction of the -NH3+ group of lysine and the COO- group of aspartic acid

Salt bridges

Example of tertiary structure stabilization: nonpolar side chains of phenylalanine and isoleucine

Hydrophobic interactions

The arrangement of polypeptide chains into noncovalently bonded aggregation

Quaternary structure

Adult hemoglobin: two alpha chains of ____ amino acids each, and two beta chains of _____ amino acids each

141, 146

Fetal hemoglobin: _____ alpha chains and _____ gamma chains

2, 2

The process of destroying the native conformation of a protein by chemical or physical means

Denaturation

Denaturating agent: can discrupt hydrogen bonding; in globular proteins, it can cause unfolding of polypeptide chains with the result that coagulation and precipiation may take place

Heat

Denaturating agent: disrupts hyrdogen bonding

6M aqueous urea

Denaturating agent: detergents such as sodium dodecylbenzenesulfate (SDS) disrupt hydrogen bonding

Surface-active agents

Denaturating agent: 2-Mercaptoethanol cleaves disulfide bonds by reducing -S-S- groups to -SH groups

Reducing agents

Denaturating agent: transition metal ions form water-insoluble salts with -SH groups

Heavy metal ions

Denaturating agent: penetrates bacteria and kills them by coagulating their proteins

Alcohol

Where will the equilibrium shift if pI>pH?

Left

Where will the equilibrium shift if pI

Right

Net charge if pH>pI

Negative

Net charge if pI>pH

Positive

A sugar alternative that is 200x sweeter than sucrose

Aspartame

Present amino acid in aspartame

Phenylalanine

Effect of configuration in aspartame

D-configuration will lead to a bitter taste (it should be sweet)

Three physiologically important amino acids especially as neurotransmitters

tyrosine, tryptophan, phenylalanine

Low level of L-dopa will lead to ______

Parkinson's disease

Two amino acids associated with L-dopa

Tyrosine and phenylalanine

Serotonin is converted from what amino acid?

Tryptophan

Low levels of serotonin leads to ____

Depression

Extremely high levels of serotonin leads to ______

Manic-depressive schizophrenia (Or bipolar disorder)

Water insoluble complexes from heated test tube (from glycation process)

Advanced glycation end-products (GAE)

pH of hemoglobin

6.8

pI of albumin

4.9

Difference between normal hemoglobin and sickle cell hemoglobin (HbS)

Valine replaces Glutamic Acid in the sixth position

_____ prompts bone marrow to manufacture fetal hemoglobin for sickle cell anemia

Hydroxyurea

True or false. Denaturation affects all structures of proteins

False. Primary structures are not affected, only to a small extent if ever, and it can be reversed

Some denaturation caused by heat can be reversed by _____. They help a partially heat-denatured protein to regain its native secondary, tertiary, and quaternary structures

Chaperones