Protein Overview

Question 1

Body Composition

Answer 1

Protein ~20% (17%)
Water 65%
Fat 10%
Minerals 4%
Carbohydrates 1%

Question 2

Protein Synthesis

Answer 2

It is estimated that a typical human cell is required to synthesise approx. 10,000 different proteins.

Question 3

Discovery

Answer 3

Proteins were first discovered in 1839 by the Chemist Gerhard Mulder.

Question 4

Protein Chemical Structure

Answer 4

• Proteins are organic compounds that contain Carbon, Hydrogen, Oxygen and Nitrogen.
• The presence of Nitrogen distinguishes proteins from fats and carbohydrates.

Question 5

Protein Structure

Answer 5

• Proteins are macromolecular polypeptides i.e. very large molecules composed of many peptide bonded amino acids.
• Proteins are formed of a few dozen to several hundred amino acids. The term protein is often used interchangeably with polypeptide
• The amino acid chain (the ‘primary structure’) folds in a certain pattern to create its 3D structure. This structure is closely linked to the function of the protein (i.e. lock and key
• Not all amino acids are protein building blocks. There are hundreds of ‘non protein’ or ‘non proteinogenic amino acids’ that aren’t encoded for in the genetic code, but may have other uses.

Question 6

Amino Acid Components

Answer 6

• Amino acids are the basic building blocks of proteins. Each amino acid contains:
- An amino group NH 2
- A carboxylic acid group COOH
- A unique side group ( R group ) which differentiates amino
• There are approximately 1000 amino acids in nature.

Question 7

Amino Acid

Answer 7

The human body uses 20 amino acids coded for in our genetic code for protein synthesis.

Question 8

Amino Acid Role

Answer 8

Amino acids can form proteins with roles as diverse as providing skeletal muscle (all essential amino acids are needed for this) through to antioxidant synthesis (glutathione synthesis requires just three: cysteine, glutamic acid, and glycine).

Question 9

Amino Acid Types

Answer 9

Non-essential
More than half of the 20 amino acids used by the body are considered non essential; the body can synthesise them.

Essential
There are 9 amino acids that humans cannot synthesise either in sufficient quantities or at all, so they must be supplied in the diet; they are termed essential.

Conditionally Essential
Sometimes non essential amino acids can become essential under specific circumstances, i.e. conditionally essential.

Question 10

Amino Acid Sources

Answer 10

• Animal sourced protein contain all 9 essential amino acids, and are hence considered a ‘complete protein’.
• A vegan/vegetarian diet can supply all essential amino acids when a variety of legumes, grains, nuts and seeds are consumed in a day.

Question 11

Non- Essential AA’s

Answer 11

Alanine
Aspartic acid
Glutamic acid
Serine
Asparagine

Question 12

Essential AA’s

Answer 12

Phenylalanine
Valine
Threonine
Tryptophan
Isoleucine
Methionine
Histidine
Leucine
Lysine

Question 13

Essential AA’s Pneumonic

Answer 13

PVT TIM HiLL

Question 14

Conditionally Essential AA’s

Answer 14

Arginine
Cysteine
Glutamine
Glycine
Proline
Tyrosine

Question 15

Histidine

Answer 15

• It is debated as to whether the correct number of essential amino acids is 8 or 9.
• Today, most experts say 9 which includes histidine since it’s not synthesised in adults.
• However, bacteria can produce histidine, although its not clear how much of our need is provided by intestinal bacteria . Histidine is also the only amino acid that does not appear to impair protein synthesis when it is deficient in the diet so that seems to make it non essential in nature.
• As a result, some regard histidine as “conditionally essential” and some continue to exclude it completely. Resources will vary.