ET III Ch.20 Proteins

Describe proteins

Most important biochemical compound

• Function both structurally and dynamically

• Form biological membranes along with lipids

• Responsible for transport and communication across cell membranes

• Act as hormones and antibodies, form a portion of the oxygen-carrying molecules hemoglobin and myoglobin

• As enzymes, serve as regulators of all biological reactions

• Proteins play a large structural role as collagen and elastin

• The focus of an embalmer

What is the composition of proteins?

• contain carbon, hydrogen, oxygen, and nitrogen

• Very large molecules with molecular masses ranging from 35,000 to 50,000,000

What are proteins polymers of?

Amino acids

Upon hydrolysis what do proteins form?

Mixtures of amino acids

Proteins are hydrolyzed by acids, bases, and enzymes called _________

Proteases

Proteins are composed of a combination of __ amino acids

20

What do the compounds of proteins contain?

Carboxyl groups (-COOH) and the amino group -NH2

What do all amino acids contain?

Another carbon, another hydrogen, and a side chain called an R group

What is a alpha carbon?

The amino group is always attached to the carbon next to the carboxyl group

Match a photo of glycine

What is glycine?

The simplest amino acid

• Used and found absolutely everywhere

what is glycine commonly used in/found in?

• Sleep aids

• Herbicides

• Tail of comet Wild 2

How does amphoterism apply to amino acids?

Amino acids contain a carboxyl group as well as an amino group, allowing them to act as both acids and bases

When carboxyl groups are in a compound, it will act as a

weak acid (proton donor)

Presence of an amino group in a compound will give it ______ properties

basic (proton accepting)

Due to amino acids _____________ nature they buffer or protect solutions against changes in pH by neutralizing either acids or bases that enter them

Amphoteric

What is another name for a dipolar ion?

Twizitterion

What is the product of joining together two or more amino acids?

A dipeptide

What is formed when two or more amino acids come together to make a dipeptide?

A joined amino acid and water

What is the group that joins two amino acids together called?

The peptide linkage

What does a peptide linkage contain?

A carbonyl group and an imide group

What is putrefaction?

Anaerobic decomposition of proteins brought about by the action of enzymes

When does putrefaction begin?

after cellular death

The rate at which putrefaction occurs depends on what?

several factors (temperature, humidity, moisture content of the body, cause of death)

• Favored by moisture and the presence of bacteria and increases with temperature

What are the first tissues to be affected by putrefaction?

Tissues containing high concentrations of proteolytic enzymes

• Ex. lining of gastrointestinal tract, epithelium of pancreas

What is the chemical reaction that initiates the putrefactive process?

Hydrolysis

Hydrolysis is a chemical property of what:

Water

What happens during hydrolysis?

Biological compounds are broken apart and water is incorporated into their structures

What is necessary for hydrolysis to occur?

Enzymes

What is deamination?

Part of the putrefactive process, it is the removal of the amino group from an amino acid

What are generally the products of deamination?

ammonia and an organic acid

Extensive putrefaction creates high levels of _________, thereby increasing formaldehyde demand

ammonia

The end of the rigor cycle signals the beginning of what cycle?

The decomposition cycle

What is decarboxylation?

Part of the putrefactive process, it is the removal of the carboxyl group from an amino acid

What does deamination produce?

carbon dioxide, water, and an amine

What do amines further decompose into during/after decarboxylation?

ammonia

Decomposition of amino acids containing sulfur liberate what?

hydrogen sulfide