1. Albumin 2. Globulin 3. Glutelin 4. Prolamine 5. Albuminoid 6. Histone 7. Protamine

BIOCHEM - Protein & Amino acid chemistry Flashcards by Milleth Jane CAPANGPANGAN

characteristics of proteins

organic nitrogenous substances (CHON)
high molecular weight (a big macromolecule)
found in all plant and animal cells
consist of alpha-amino acids
linked by peptide bonds

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FUNCTIONS OF PROTEINS:

Catalyst of chemical reactions - enzymes
Transport and storage - hemoglobin
Coordinated motion - actin and myosin
Mechanical support - collagen and keratin (structural proteins)
Immune protection - gamma globulins
Transmission of nerve impulses -neurotransmitters
Cell signaling - membrane receptors
Hormones – insulin, thyrotropin, somatotropin

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another example of transport protein.

Example of a substance stored by our
proteins is iron

Albumin

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These serve as a communication, along
with hormones.

that are derived from amino acids

neurotransmitters

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SIMPLE PROTEINS:

Albumin
Globulin
Glutelin
Prolamine
Albuminoid
Histone
Protamine

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soluble in water and dilute aqueous salt solution; heat coagulable

a plasma protein that acts as a transporter. It transports a lot of things in our blood.

Albumin

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insoluble in water; soluble in aqueous salt soln; heat coagulable

Globulin

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soluble in dilute acids and alkalies; heat coagulable

ex. plant proteins – glutenin (wheat), oryzenin (rice)

Glutelin

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alcohol-soluble protein

ex: seed proteins – zein (corn), gliadin
(wheat)

Prolamine

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least soluble

ex: animal proteins – keratin, collagen

Albuminoid

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basic protein; soluble in water, dilute acid and alkali; found in combination with DNA

Histone

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simplest; basic; soluble in water, dilute ammonia, acid and alkali; found in spermatozoa

Protamine

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CONJUGATED PROTEINS (proteins that
contain other functional groups or other
macromolecules):

Nucleoproteins
Glycoproteins and proteoglycans
Chromoproteins
Lipoproteins
Metalloproteins

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contain nucleic acid (DNA, RNA) as the prosthetic group

Ex. histones

Nucleoproteins

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contain carbohydrates

____________ have more carb content than proteins.

___________ have more protein content than carbs.

proteoglycans

Glycoproteins

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contain prosthetic groups that give color

ex. hemoglobin
- Iron is the prosthetic group

Chromoproteins

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have groups
other than our macromolecules

Prosthetic group

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associated with lipids
ex. VLDL chylomicron, LDL, HDL

Transporters of lipids in the body

Lipoproteins

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contain minerals

ex. iron in cytochromes

Metalloproteins

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Somewhat similar to chromoproteins except that in chromoproteins, their prosthetic group would give them color

_________ would contain metal as their prosthetic group like iron, copper, or magnesium

Metalloproteins

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CLASSIFICATION BASED ON THE SHAPE AND CERTAIN PHYSICAL CHARACTERISTICS:

A. FIBROUS PROTEINS
B. GLOBULAR PROTEINS

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tough
involved in structural functions
ex. collagen, keratin

FIBROUS PROTEINS

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(has more functions as transport proteins or enzymes)

involved in mobile and dynamic functions
ex. enzymes, plasma proteins, hemoglobin

GLOBULAR PROTEINS

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FUNCTIONS OF AMINO ACIDS:

Building blocks of proteins
Precursor of various substances
Source of energy
Special amino acids as components of certain types of proteins
Phosphorylation and dephosphorylation
Chemical messengers
Metabolic intermediates

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proteins as Precursor of various substances

a. Glycine b. Glutamic acid c. Phe and Tyrosine d. Tryptophan

the precursor of heme, purine, creatine

Glycine

the precursor of GABA

Glutamic acid

the precursor of thyroxine, & epinephrine

Phe and Tyrosine

the precursor of niacin, serotonin, melatonin

Tryptophan

If our glucose and fat storage is already depleted, the next thing that is used for energy would be_________.

amino acids

substrate for the building blocks of our proteins

amino acids

during prolonged cases of low blood glucose or starvation, the _________ is used as a source of energy

amino acids

Special amino acids as components of certain types of proteins:

a. Hydroxyproline & hydroxylysine b. Gamma-carboxyglutamic acid c. Desmosine (derivative of lysine)

component of collagen

Hydroxyproline & hydroxylysine

component of prothrombin

Gamma-carboxyglutamic acid

component of elastin

Desmosine (derivative of lysine)

Phosphorylation and dephosphorylation of amino acids with rings such as _____________. __________ play a major role in activation and inactivation (or inhibition) of enzymes

serine

In cell signaling, there are other amino acid residues found on receptors that are important in communication such as _________, ___________, & ____________

serine, threonine, and tyrosine

amino acids or their derivatives act as chemical messengers example:

GABA, serotonin

amino acids act as metabolic intermediates:

a. Arg, citrulline, ornithine b. amino acids that are converted to the intermediates of the Krebs cycle

amino acids metabolic intermediates in urea cycle:

Arg, citrulline, ornithine

Each amino acid has a central carbon, called the _________, to which four different groups are attached (chiral carbon):

alpha carbon

4 groups of amino acids:

1. basic amino group (-NH2) 2. acidic carboxyl group (-COOH) 3. hydrogen atom (-H) 4. distinctive side chain (-R)

its distinct side chain is a hydrogen atom hence it is not chiral anymore

Glycine

DIFFERENT FORMS OF AN AMINO ACID:

1. Unionized form 2. Ionized form

Ala or A

Alanine

Arg or R

Arginine

Asn or N

Asparagine

Asp or D

Aspartic acid

Cys or C

Cysteine

Glu or E

Glutamic acid

Gln or Q

Glutamine

Gly or G

Glycine

His or H

Histidine

Ile or I

Isoleucine

Leu or L

Leucine

Lys or K

Lysine

Met or M

Methionine

Phe or F

Phenylalanine

Pro or P

Proline

Ser or S

serine

Trp or W

Tryptophan

Thr or T

Threonine

Tyr or Y

Tyrosine

Val or V

Valine

CLASSIFICATION OF AMINO ACID BASED ON R-GROUP (overview only)

1. Amino acids with nonpolar or hydrophobic R groups 2. Amino acids with uncharged polar R groups 3. Amino acids with positively charged R groups 4. Amino acids with negatively charged R groups

Amino acids with nonpolar or hydrophobic R groups:

a. Amino acids with aliphatic side chains b. Amino acid with aromatic side chains

Amino acids with aliphatic side chains:

1. Glycine 2. Alanine

Branched-chain amino acids (aliphatic):

3. Valine 4. Leucine 5. Isoleucine 6. Methionine 7. Proline

Amino acid with aromatic side chains:

1. Phenylalanine 2. Tryptophan

Amino acids with uncharged polar R groups:

a. Hydroxyl-containing amino acids b. Amide derivatives of Glu and Asp

Hydroxyl-containing amino acids:

1. Serine 2. Tyrosine 3. Threonine

Amide derivatives of Glu and Asp:

1. Glutamine 2. Asparagine 3. Cysteine (Thiol Group)

Amino acids with positively charged R groups a. Basic amino acids

1. Lysine 2. Arginine 3. Histidine

Amino acids with negatively charged R groups a. Acidic amino acids

1. Glutamic acid 2. Aspartic Acid

● Neutral amino acids ● R groups do not bear (+) or (-) charges ● Interact poorly with water ● Play an important role in maintaining the conformation or 3-dimensional structure of proteins

AMINO ACIDS WITH NONPOLAR OR HYDROPHOBIC R GROUPS

Within nonpolar groups, there could be interactions (bonding / ___________ force on non-polar). Due to this force, they could play a role in maintaining the stability of the protein conformation.

Van der Waals

Amino acids with aliphatic (straight hydrocarbon) side chains

1. Glycine 2. Alanine

simplest amino acid. its R group: Hydrogen only; the only amino acid that is NOT CHIRAL

Glycine

Alanine R group:

Methyl group (CH3)

Branched because there is tree-like branching in their R group Differs in hydrocarbon length

Branched-chain amino acids

Branched-chain amino acids:

1. Valine 2. Leucine 3. Isoleucine

these amino acids are the ones affected by metabolic errors for branched chain amino acid metabolism

LIV - branched chain

Other examples of branched-chain amino acids, but belongs to another group

4. Proline 5. Methionine

R group is a distinct closed ring Secondary amino acid or an imino acid Nitrogen is bonded to the α-carbon and the side-chain group

Proline

what do you call when amino group is NH2 instead of NH3

imino acid

what do you call when NH is unable to bond because it is part of the R group

helix-breaker

Sulfur-containing, non-polar amino acid

Methionine

Methionine is converted to ___________, an important methyl group donor in methylation reactions, since it is able to donate the CH3 in its R group

S-adenosylmethionine (SAM)

Amino acid with aromatic side chains:

1. Phenylalanine (benzene ring) 2. Tryptophan (indole ring)

contain unsaturations or double bonds

aromatic

has CH2 in its R group which would contain the phenyl group (“piattos”)

Phenylalanine

Alanine R group is CH3, while here, instead of additional hydrogen, phenyl group is attached

Phenylalanine

the largest of all twenty amino acids side chain is indole, which is aromatic with a binuclear ring structure has phenyl group and attached to that phenyl ring is a 5-membered ring

Tryptophan; indole

have functional groups capable of hydrogen bonding -OH groups serve other functions in proteins

AMINO ACID W/ UNCHARGED POLAR R GROUP

AMINO ACID W/ UNCHARGED POLAR R GROUP:

A. Hydroxyl (-OH) -containing amino acids B. Amide derivatives of Glutamine and Asparagine

OH groups serve other functions in proteins: Formation of the phosphate ester of ____________is a common regulatory mechanism Formation of hydrogen bonds with other macromolecules that would contain covalent bonds OH groups of ___________& ___________ are points for attaching carbohydrates

Tyrosine Serine and Tyrosine

Hydroxyl (-OH) -containing amino acids

1. Serine 2. Threonine 3. Tyrosine

Important in cell-to-cell communication, because these are sites of phosphorylation reaction; -OH can be used as attachment for phosphate groups, which in turn can either activate or inhibit the enzymes - important in regulation of enzyme activity site of glycosylation reaction - important in formation of mucin

Hydroxyl (-OH) -containing amino acids

Simplest amino acid that contains the -OH group

Serine

Has branching but still contain -OH

Threonine

Closely related to Phenylalanine; difference: additional -OH group

Tyrosine

Glutamine is derived from _________ Asparagine is derived from _________

Glutamic acid Aspartic acid

Glutamine and Asparagine Contains -NH2 instead of ________

-OH

Important in detoxification of ammonia Able to get extra ammonia from the body system. Ammonia will be taken up by _________ & ___________ to form Glutamine and Asparagine

Glutamate and Aspartate

lower down our ammonia level, such that __________is the primary source of urinary ammonia

Glutamine

Instead of -OH, it contains a sulfhydryl (-SH) group (a.k.a. thiol group) ● Important in maintenance of protein structure (e.g. insulin, immunoglobulins)

Cysteine

Two cysteine residues combine and form a strong disulfide bond, and _______ is the resulting product.

cystine

Principle behind hair rebonding is that the chemicals used break the disulfide linkages between _______ residues, and by doing so, protein structure is lost.

cysteine

the 21st L-α-Amino Acid ➢ Found in peroxidases and reductases

Selenocysteine

Selenium (Se) atom replaces the sulfur of its structural analog __________

cysteine

There is no codon for this amino acid ➢ Inserted into the polypeptide during translation

selenocysteine

Selenocysteine is not inherently introduced by your sense from your DNA, RNA what happens is that during the synthesis of your cysteine, it is modified, hence ____________ forms selenocysteine

posttranslational modification

AMINO ACID W/ POSITIVELY CHARGED R GROUP:

Basic amino acids - have a net positive charge 1. Lysine 2. Arginine 3. Histidine

contains the guanido group

Arginine

contains the imidazole group

Histidine

responsible for the buffering capacity of hemoglobin

Histidine

AMINO ACID W/ NEGATIVELY CHARGED R GROUP:

Acidic amino acids 1. Glutamic acid or Glutamate 2. Aspartic acid or aspartate

interactions between acidic and basic amino acids results in the formation of ionic bond aka ________________

salt bond, electrostatic bond

Important in maintaining protein structure:

1. Glutamic acid or Glutamate 2. Aspartic acid or aspartate

Types of interactions entered into by the different R groups of amino acids:

1.Hydrogen bonding 2. Ionic interaction 3. Hydrophobic interactions of nonpolar R grps 4. Disulfide bond

Hydrogen is attracted to other electron rich areas

Hydrogen bonding

examples of Hydrogen bonding

a. -O-H …….. O=C b. -O-H …….. O c. -S-H ……… O

usually involved in the carboxyl grp and amino grp of another amino acid -COO- ……..NH3+

Ionic interaction

Hydrophobic interactions of nonpolar R grps :

Van der Waals interaction

PHYSICAL PROPERTIES OF AMINO ACID:

1. Solubility 2. Melting points 3. Taste 4. Appearance 5. Optical property 6. Ultraviolet absorption spectrum of aromatic amino acids 7. Acid-base properties

For all the standard amino acids, except _____________, the & carbon is asymmetric , bonded to four different substituent groups. In this case the &-carbon is a chiral center

glycine

All molecules with a chiral center are _____________ ex. they can rotate the plane-polarized light either to the right (dextrorotatory) or to the left (levorotatory).

optically active

D and L amino acids - due also to the presence of chiral center

Stereoisomerism

Ultraviolet absorption properties of proteins are determined solely by __________, ___________, & _____________(Aromatic AA)

Phe, Tyr and Trp

The amino (NH3) and carboxylic acid (COOH) groups readily ionize

Acid-base properties

Amino will give off its H and will be ______________charged (NH3 -> NH2+)

positively

Carboxylic acid will donate H and will be ______________charged (COOH -> COO-)

negatively

pK (&-COOH)

around pH 2.2

pK (&-NH2)

around pH 9.4

is a constant that determines that R grp is able to give off or receive protons.

COOH will be COO- at pH 2.2 but at pH 1 which is below ph 2.2 , what will happen?

it will not give off H and will remain as COOH

Amino grp will not donate proton at lower pH (less than pH 9.4) like pH 7 (neutral) - it will remain as NH3 but at higher pH beyond pH 9.4 , what will happen?

the amino grp will become NH2+

An amino acid can act as a base or proton recipient and an acid or proton donor (amphoteric). T or F?

True

Different Forms of an Amino Acid:

1. Unionized form 2. Dipolar ion or zwitterion form 3. Fully protonated form (pH 1) 4. Fully ionized form (pH 11)

electrically neutral; zero charge number of positive charge equal to number of negative charge

Zwitterion

remain stationary in an electrical field

Dipolar ion or zwitterion form

Form of an Amino Acid that has net positive charge (+)

Fully protonated form (pH 1)

Form of an Amino Acid that is negatively charge at higher pH

Fully ionized form (pH 11)

is the step-by-step dissociation of the amino acid starting from the fully protonated or positive form up to the fully ionized or negative form.

Protonic equilibria (Titration of Amino Acids)

can predict the charge of the amino acid in a given solution with known pH can devise a procedure of separating amino acids based on their charge

uses of Protonic equilibria (Titration of Amino Acids)

That pH at which an amino acid bears no net charge and hence does not move in an electrical field. - That pH exactly at the midpoint between the pK values on either side of the zwitterion species.

Isoelectric Point (pHI, pI, IpH)

The pI of neutral amino acids are in the neighborhood of 6.0; acidic amino acids – very much below 6.0; basic amino acids – very much above 6.0.

true

titration: At lower pH, if the pKa is 2.34 for the COOH, lower than that (example pH 1) there will be no donation of hydrogen. So the overall net charge of the whole amino structure is +1 what will happen if the pH already exceeded the pKa of the carboxyl group (example pH 7.4)?

the carboxyl group can now readily donate the proton and the net charge of this Alanine is now 0 because the negative charge cancels out the positive charge in the amino group

in the isoelectric zwitterion of Alanine with carboxyl group COO- has pKa of 9.69, what will happen to it in pH 10?

it now exceed the pKa of the Amino group so the amino group donates the proton, the positive charge disappears and what is left behind is the negative charge. So if we calculate the net charge, it will be -1

how to compute for the isoelectric point ?

by getting the average of the pKa of the different groups pI = pK 1 + pK 2 / 2

where the amino acid is electrically neutral

isoelectric point

dissociation constant of &-COOH (most acidic)

pK1

If the R group is able to donate or receive H+. how are you gonna determine the pI?

The basic and acidic amino acids have an additional dissociation constant so there will be an additional pKa that will help you determine the isoelectric point of that amino acid.

amino acid polymers with low molecular weights, typically consisting of less than 50 amino acids.

Peptides

more than 50 amino acids

Proteins

consisting of 2 to 10 amino acids

Oligopeptides

have more than 10 amino acid residues

Polypeptides

PEPTIDES WITH SIGNIFICANT BIOLOGIC ACTIVITIES

1.Glutathione 2. Oxytocin and vasopressin 3. Met-enkephalin and Leu-enkephalin 4. Atrial natriuretic factor 5. Substance P and bradykinin 6. Glucagon 7. Corticotropin 8. Aspartame

(gamma-glutamyl-L-cysteinylglycine) reducing agent; due to –SH group

Glutathione

It is the cysteine group esp. the Sulfhydryl group that is important in its activity. It has to be in an -SH form to be a good reducing agent/ antioxidant (reduced form)

Glutathione

- protects the cell from the destructive effects of oxidation by peroxides - works hand in hand with glutathione peroxidase

Glutathione

Glutathione is Composed of 3 amino acids:

Glutamate, Cysteine, Glycine

contain nine amino acid residues

Oxytocin and vasopressin

stimulates contraction of uterine muscle during childbirth

oxytocin

is an antidiuretic hormone; stimulates water reabsorption in the kidney

vasopressin

pentapeptide; opioid peptides - relieve pain; bind to receptors in the brain and induce analgesia

Met-enkephalin and Leu-enkephalin

- has 28 amino acid residues - stimulates the production of a dilute urine.

Atrial natriuretic factor

The effect is opposite of that Vasopressin.

Atrial natriuretic factor

stimulate the perception of pain

Substance P and bradykinin

has 29 amino acid residues - opposes the action of insulin

Glucagon

with 39 amino acid residues; stimulates adrenal cortex

Corticotropin

artificial sweetener

Aspartame (L-aspartyl phenylalanine methyl ester)

The formation of your peptide bond is very similar to Glycosidic bond, it is a condensation reaction or a dehydration reaction but the interaction is between the ______________

carboxyl group of Amino Acid 1 and the Amino group of Amino Acid 2

LEVELS OF STRUCTURAL ORGANIZATION OF PROTEINS:

a. Primary Structure b. Secondary Structure c. Tertiary Structure d. Quaternary Structure

- quantitative amino acid composition - sequence of amino acids - number of peptide chains

PRIMARY STRUCTURE

Most abundant amino acid in proteins:

Leu, Ala, Gly, Ser, Val Glu

Rarest in proteins are

Trp, Cys, Met His

The backbone of a protein refers to the

atoms that participate in the formation of peptide bonds

The 3-dimensional shape of a folded polypeptide is result of the interactions among the ____________

R groups

Due to the formation of hydrogen bonds between peptide bonds

SECONDARY STRUCTURE

Two types of secondary structure:

1. Coils or helices 2. Sheets or pleats

intrachain hydrogen bonding

Coils or helices

interchain hydrogen bonding

Sheets or pleats

discovered by Linus Pauling in 1951

Alpha-helix

Stabilized by INTER-residue hydrogen bonds formed bet. the H atom attached to a peptide N and the carbonyl O of the residue 4th in line behind in the primary structure Each peptide bond participates in hydrogen bonding

Alpha-helix

forms spontaneously as it is the lowest energy, most stable conformation for a polypeptide chain.

alpha-helix

There are ___________________amino acid residues per turn with a pitch of .54 nm (5.4 A); spacing per residue is .15 nm (1.5 A) - Amino acid R groups extend outward from the helix

3.6

distance bet. corresponding points per turn

pitch

FACTORS THAT DESTABILIZE (destroy) THE ALPHA HELIX:

1. Presence of adjacent similarly charged amino acids (like charges repel) 2. Presence of adjacent bulky R groups. (groups with aromatic ring) 3. Presence of proline

Why presence of proline destabilize the alpha helix?

- contains rigid ring that prevents the N-C bond from rotating - no N-H group available to form intrachain hydrogen bonds (helix breaker; incapable of forming hydrogen bonding)

destabilize = ________

destroy

second most commonly occurring protein 2 degree structure

BETA-PLEATED SHEET

Formed when 2 or more almost fully extended polypeptide chains lie side by side such that hydrogen bonding occurs between adjacent peptide chains

BETA-PLEATED SHEET

Hydrogen bonds in beta-pleated sheets are ______________

interchain

Amino acids with less bulky R groups are present

BPS

BETA-SHEETS OCCUR IN TWO DIFFERENT ARRANGEMENTS:

1. ANTIPARALLEL BETA-SHEET 2. PARALLEL BETA-SHEETS

- neighboring H bonded polypeptide chains run in opposite directions - more stable because the H bond in between is somewhat perpendicular to the plane

ANTIPARALLEL BETA-SHEET

hydrogen bonded chains extend in the same direction.

PARALLEL BETA-SHEETS

FACTORS THAT DESTABILIZE THE BETA-PLEATED SHEETS:

1. Bulky R groups. 2. R groups with like charges

SUPERSECONDARY STRUCTURES OR MOTIFS:

● Combinations of 2 degree structure ● Occur as part of a larger functional unit ● Have a particular function ● Have different functions in different proteins ● Have roughly 10 to 40 amino acid residues each

COMMON SUPERSECONDARY STRUCTURES:

1. Helix-loop-helix 2. Coiled-coil motif 3. Beta-alpha-beta unit 4. Hairpin 5. Zinc finger 6. Leucine zipper 7. Greek key in picture: 8. Beta-meander 9. alpha-alpha units 10. beta-barrel 11. EF hand - E helix and F helix 12. Leucine zipper 12. Zinc finger

3-dimensional structure ● Protein conformation ● Results from further folding of a poly-peptide with regions of α-helix and/or beta-sheet, into a closely packed, nearly spherical shape

TERTIARY STRUCTURE

Indicates how 2 degree structural features – helices, sheets, bends, turns and loops assemble to form domains.

TERTIARY STRUCTURE

Amino acid residues that are distant from each other in the 1 degree structure come into close proximity when the polypeptide folds

tertiary structure

When polypeptide folds, proteins become more compact; most water molecules are excluded from the proteins’ interior making possible the interactions between

polar and nonpolar Amino Acids

Large globular proteins (> 200 AA) often contain several compact units called ________

domains

are structurally independent segments that have specific functions (e.g. binding an ion)

Domains

TYPES OF INTERACTIONS THAT STABILIZE TERTIARY STRUCTURE:

● Hydrophobic interactions [R leu] [CH3] [aromatic rings] ● Electrostatic interactions (salt bridges) [NH3+] ● Hydrogen bonds [O...H] ● Covalent bonds (disulfide bridges) [SH - SH]

PROTEIN FOLDING IS ASSISTED BY :

MOLECULAR CHAPERONES AND ENZYMES

– proteins that have the net effect of increasing the rate of correct folding by binding newly synthesized polypeptides before they are completely folded. - assist in the translocation of polypeptide chains across membranes

Molecular chaperones

examples of molecular chaperons

heat-shock proteins, chaperonins

Enzymes involved in protein folding:

1. Peptidyl prolyl cis-trans isomerase 2. Protein-disulfide isomerase

they are discrete, independent folding units within the 30 structure that perform a particular task such as binding of a substrate or other ligand

DOMAINS OR LOBES

they consist of combinations of several units of supersecondary structures.

DOMAINS OR LOBES

Size of domains varies from 25-30 to about 300 amino acid residues, with an average of about _____ amino acids.

100

Exhibited only by proteins containing more than one polypeptide chain. ● Most proteins with molecular masses above 100 kD, consist of more than one polypeptide chain

QUATERNARY STRUCTURE

Each polypeptide component is called a ______________ maybe identical or different

subunit

proteins are those with more than one subunit

Oligomeric

are identical subunits.

Protomers

describes the characteristic manner in which the individual , folded polypeptide chains fit each other or interact with one another so that they can act as one single molecule.

Quaternary structure

When you have more than 1 tertiary structure, you have a _________

Quaternary structure

a classic example of a quaternary structure, has 4 subunits. Each subunit has a tertiary structure. When you combine them together, you have the quaternary structure of the ------------

Hemoglobin

INTERACTIONS THAT HOLD SUBUNITS TOGETHER:

● Hydrophobic interactions ● Electrostatic interactions ● Hydrogen bonds ● Interpolypeptide disulfide bonds

are the principal forces that hold the subunits together

Hydrophobic interactions

contribute to the proper alignment of the subunits

Electrostatic forces

occurs when a protein loses its native secondary, tertiary and/or quaternary structure; there is cleavage of noncovalent bonds always correlated with the loss of a protein’s function

DENATURATION OF PROTEINS

DENATURING AGENTS:

A. PHYSICAL AGENTS B. CHEMICAL AGENTS

examples of PHYSICAL AGENTS

● extremes of pH and temperature ● high pressure ● ultraviolet light ● ultrasound

examples of CHEMICAL AGENTS

● organic solvents – acids, alkali, urea, guanidine ● Detergents

substances that would disrupt ionic bridges (electrostatic bonds) in between proteins (e.g. soap, lysol)

Detergents

CHEMICAL ALTERATIONS

1. Decrease in solubility – most visible effect in globular proteins 2. Many chemical groups which were inactive become exposed and more readily detectable

Whenever there is decrease in solubility, it can also signify a loss of _________

function

PHYSICAL ALTERATIONS:

● increased viscosity ● decreased rate of diffusion ● increased levorotation ● cannot be crystallized All of these would result in the loss of function of the proteins.

BIOLOGICAL ALTERATIONS:

● increased digestibility ● enzymatic or hormonal activity is destroyed ● antibody functions are altered

BIOCHEM - Protein & Amino acid chemistry Flashcards

(236 cards)