CH18: AMINOC ACIDS & PROTEINS

OSU BIOPHRM 3311

ID these structures

ammonium ion, amino group

ID this structure

hydroxyl group

ID this structure

carbonyl group

ID these structures

carboxyl group, carboxylate anion

ID this structure

amide group

ID this structure

carboxylic acid ester

ID these structures

phosphates, mono-, di-, tri-

ID this structure

hemiacetal group

ID this structure

acetal group

ID these structures

thiols, sulfides, disulfides

________ must continuously break down food molecules, generate and store energy, build up new biomolecules, and eliminate waste

Biochemical reactions

principal classes of biomolecules are:

• Carbohydrates

• Lipids

• Proteins

• Nucleic acids, and

• Their combinations (Glycolipids, glycoproteins and lipoproteins)

Even though some biomolecules are large and complex, the chemical reactions involving their functional groups are_________.

similar to those in simpler organic molecules

Carbohydrates are organic molecules composed of _______, typically in a ratio of _____.

• carbon, hydrogen, and oxygen

• 1:2:1

3 main classes of carbohydrates

• monosaccharides

• disaccharides

• polysaccharides

Glucose + fructose = _______

sucrose

Carbohydrates contain ______

H, C, and O

main energy source in the body is _______

ATP

Glycogen is made up of a LOT of ____ compounds

glucose

The energy storage of glycogen is not an ________. The variety in the linking of compounds assists in determining the ________

• immediate source of energy

• purpose of the molecule

monosaccharides definition

simple sugars made of a single unit, such as glucose and fructose, and an energy source

disaccharides definition

two monosaccharides linked together, such as sucrose, and an energy source

polysaccharides definition

long chains of monosaccharides and an energy storage (starch, glycogen) and structural support (cellulose)

_____are organic molecules that occur naturally in both plants and animals, and they exhibit solubility in non-polar organic solvents - H2O insoluble

Lipids

lipids contain these elements: _______

Carbon, Hydrogen and Oxygen; some may also contain nitrogen and phosphorus

examples of lipids are: ______

Triacylglycerols, certain vitamins (A, D, E and K), and steroid hormones

lipid functions

Energy storage, thermal insulation, components of cell membrane, vitamins and precursor of hormones

_____ contains a saturated chain, a mono-unsaturated chain, and poly-unsaturated chain

Triacylglycerol

Saturated = ______

fats

Unsaturated = ______

oils

Steroid is a _______

hormone

proteins contain these elements: _______

Carbon, Hydrogen, Oxygen, Nitrogen, and sometimes Sulfur and Phosphorus

Nature has ________ different amino acids found in proteins

20

Polypeptides and proteins are built by connecting_______

amino acids with peptide bonds

proteins can contain multiple ________

polypeptides

Some proteins need an extra component called a ______ for their function

co-factor

The human body has many proteins, estimated between _______, each with its unique shape, structure, and function

80,000 to 400,000

enzymes function

catalyze biochemical reactions

hormones function

regulate body functions by carrying messages to receptors

storage proteins function

make essential substances available when needed

transport proteins function

carry substances through body fluids

structural proteins function

provide mechanical shape and support

protective proteins function

defend the body against foreign matter

contractile proteins function

do mechanical work

Nucleic acids are polymers of nucleotides and exist in two main types: _________

deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)

A __________ contains a five-carbon sugar bonded to a heterocyclic nitrogen base (nucleobase) and phosphates

nucleotide

nucleic acids contain these elements: ________

carbon, hydrogen, oxygen, nitrogen and phosphorus

Nucleic acids store and transmit ________

genetic information and direct the synthesis of proteins, which are essential for all cellular functions

An α-Amino acid contains an alpha carbon (Cα), that is bound to four specific groups: _____

1. An alpha primary amine -NH

2. a carboxyl group -COOH

3. a hydrogen atom, and

4. a R group called side chain that is specific for individual α-amino acids

_____, NH2 group is bond to R group; forming a cyclic secondary amine

Proline

α-amino group is mostly a ________

primary amine

Amino acids are frequently represented by their______

initial three letters

3-letter code for: alanine

Ala

3-letter code for: cysteine

Cys

3-letter code for: Glutamate

Glu

3-letter code for: Glycine

Gly

3-letter code for: Lysine

Lys

3-letter code for: Serine

Ser

Standard amino acids are commonly classified by their ________ of the side chains

dietary requirements or properties

9 Essential amino acids definition

our body cannot synthesize or synthesize enough of these - MUST BE INCLUDED IN OUR DIETS

11 Non-essential amino acids definition

our body synthesize enough of these - DO NOT NEED TO BE INCLUDED IN OUR DIETS

Properties of the side chains (R groups) in our body:

1. Neutral nonpolar

2. Neutral polar

3. Basic and positively charged

4. Acidic and negatively charged

The _____ is the pH at which an amino acid carries no net electrical charge, meaning that the number of positive charges equals the number of negative charges within the molecule

isoelectric point (PI)

Non-polar amino acids mainly have_______

hydrocarbon side chains

non-polar amino acids exhibit: ______

• hydrophobic characteristics

• tend to interact with each other

• typically found within the interior of proteins, often buried in the protein core

____ contains thesulfide functional group (C-S-C; AKA thioether)

Methionine

_____ is unusual in that the α-nitrogen atom forms a five-membered ring with the 3-carbon side chain

Proline

______ is the largest amino acid with 9 carbons and a nitrogen in the side chain, in which the nitrogen does not act as a base due to resonance with the aromatic ring

Tryptophan

in resonance amino acids, the N does not have a lone pair of e-!! Therefore, does not serve as a ________

proton acceptor

There are 6 neutral polar amino acids with polar functional groups, including _________

amide (Asn and Gln), thiol (Cys), alcohol (Ser and Thr), and phenol (Tyr)

amide (Asn and Gln), thiol (Cys), alcohol (Ser and Thr), and phenol (Tyr) amino acids can form ________

hydrogen bonds among themselves, with each other, and with water molecules.

Neutral amino acids (polar or nonpolar) have PI range ______

5-6

three amino acids with basic side chains:

lysine, arginine, histidine

_____ contains a primary s-amine group in the side chain. At body pH 7.4, this amine group accepts a proton forming NH3+, resulting in ____ having a net positive charge

Lysine (both)

________ has a total of three nitrogen atoms in its side chain. At pH 7.4, this is positively charged

Arginine

The PI of Lysine and Arginine are of high values ______

(9.7 and 10.8)

The PI of Histidine (7.6) is closest, among all amino acids, to the physiological pH (7.4), therefore, it can ______

exist in 2 forms

Small variations in environmental pH can significantly alter the charged state of histidine. The side chain can shift from being ______, to becoming ______.

• neutral and a proton acceptor

• positively charged and a proton donor

Histidine's acid-base characteristics enable it to participate in _______.

catalytic biochemical reactions

Two amino acids, _______, contain acidic side chains; a carboxyl functional group

aspartate and glutamate

Because of aspartate’s and glutamate’s isoelectric points are lower than the physiological pH of 7.4, both exist predominantly in their ________

deprotonated (carboxylate anion) forms in the body, carrying a net negative charge.

aspartate and glutamate are more accurately referred to as ______, the conjugate base forms present under physiological conditions

aspartic acid and glutamic acid

9 non-polar amino acids

Glycine, Alanine, Isoleucine, Leucine, Methionine, Phenylalanine, Tryptophan, Proline, Valine

6 polar amino acids

Asparagine, Cysteine, Glutamine, Serine, Threonine, Tyrosine

3 basic (+)-charged amino acids

Arginine, Histidine, Lysine

2 acidic (-)-charged amino acids

aspartate/Aspartic acid, Glutamic acid/Glutamate

ID this amino acid

glycine

ID this amino acid

alanine

ID this amino acid

cysteine

ID this amino acid

serine

ID this amino acid

glutamic acid

ID this amino acid

lysine

An amino acid has at least two ionizable groups:

acidic and basic

acidic amino acid definition

α-carboxyl group which can donate a proton to become carboxylate anion

Basic amino acid definition

α-amino group which can accept a proton to become ammonium ion

protonated form of aciddic amino acids

—COOH & —NH3+

deprotonated form of basic amino acids

—COO- & —NH2

is there a charge delocalization w/ acid amino acids?

yes (resonance) w/ a weaker base and stronger acid

is there a charge delocalization w/ basic amino acids?

no w/ a stronger base and weaker acid

-COO- is a _____ base than –NH2

weaker