KIN 280 A - Chapter 5: Protein Study Guide

Vocabulary practice flashcards covering protein structure, synthesis, digestion, nitrogen balance, dietary needs, and related disorders from Chapter 5.

Amino acids

The building blocks of proteins containing carbon, hydrogen, oxygen, and nitrogen, each composed of a central carbon, an amine group, an acid group, a hydrogen atom, and a unique side chain.

Essential amino acids

A group of $9$ amino acids that cannot be produced in sufficient quantities by the body and must be obtained from food.

Nonessential amino acids

A group of $11$ amino acids that can be produced by the body in sufficient quantities.

Transamination

A process that transfers an amino group from one amino acid to another compound, used by the body to synthesize nonessential amino acids.

Peptide bonds

The chemical bonds that join amino acids together to form proteins.

Transcription

The process in which genetic information from DNA is copied into messenger RNA (mRNA) to be carried to the ribosome.

Translation

The process at the ribosome where mRNA instructions are read and transfer RNA (tRNA) brings the correct amino acids to assemble them in the proper order.

Protein degradation

The breakdown of existing proteins, releasing amino acids that can be recycled to build new proteins.

Dipeptide

A protein chain consisting of $2$ amino acids.

Tripeptide

A protein chain consisting of $3$ amino acids.

Oligopeptide

A protein chain consisting of $4\text{ to }9$ amino acids.

Polypeptide

A protein chain consisting of $10$ or more amino acids, according to the lecture slides.

Protein turnover

The continuous process of making new proteins and breaking down existing proteins in the body.

Amino acid pool

The supply of amino acids available in the body from dietary intake and the breakdown of existing proteins.

Limiting amino acid

An essential amino acid that is missing or present in the smallest supply relative to the body's needs, thereby restricting protein synthesis.

Hydrochloric acid (HCl)

A stomach acid that denatures proteins during digestion by unfolding their structure.

Pepsinogen

An inactive enzyme precursor secreted in the stomach that is activated into pepsin.

Pepsin

An active stomach enzyme that breaks down proteins into shorter polypeptides and smaller pieces.

Gastrin

A hormone that helps regulate hydrochloric acid production and pepsin release in the stomach.

Trypsin

A pancreatic enzyme in the small intestine that breaks proteins and polypeptides into smaller peptides.

Chymotrypsin

A pancreatic protease in the small intestine that breaks proteins into smaller peptides.

Carboxypeptidase

A pancreatic enzyme in the small intestine that removes amino acids from the ends of peptide chains.

Enterocytes

Nutrient-absorbing cells lining the small intestine that contain peptidases to break dipeptides and tripeptides into individual amino acids.

Hepatic portal vein

The blood vessel through which amino acids travel from the intestinal wall to the liver.

Nitrogen balance

A comparison between the amount of nitrogen entering the body through protein intake and the amount of nitrogen leaving the body through excretion.

Positive nitrogen balance

A condition in which nitrogen intake is greater than nitrogen excretion, seen during growth, pregnancy, and recovery from illness or protein deficiency.

Negative nitrogen balance

A condition in which nitrogen excretion is greater than nitrogen intake, associated with starvation and low-energy-intake diets.

Complete protein

A protein source that contains sufficient amounts of all nine essential amino acids.

Complementary proteins

Two or more incomplete protein sources that, when combined in the diet during the same day, provide all nine essential amino acids.

Cystic fibrosis

An inherited, single-gene disorder caused by a mutation that results in an abnormal chloride transport protein, producing thick mucus that affects respiratory and gastrointestinal systems.