Protein Flashcards
Protein quick facts
After water it is the second most abundant compound found in the body.
On average 43% can be found in skeletal muscle.
Makes up about 20% of total bodyweight.
Not a preferred energy source, normally contributing only 10-15% of our daily energy needs.
Role of protein
Acting as the building block for enzymes.
Formatting the structure of hair, skin, nails, tendons and ligaments.
Making up clotting agents in blood plasma.
The synthesis of cellular components and DNA / genetic material.
Acting as the building block for enzymes.
Producing haemoglobin.
Occasionally acting as hormones.
Regulating the pH of fluids in the body
Protein Requirements
On average men and women, between the ages of 19 and 50 years, require 56g and 45g of protein per day respectively. Body size influences how much protein is required - the bigger the person, the more they need.
More accurate protein requirements can be calculated by multiplying body weight in kilograms (kg) by 0.75, assuming that every kg of body weight requires 0.75 grams of protein to function. This recommendation is based on the requirements for individuals leading a sedentary lifestyle.
Protein Requirement calculation
o calculate the daily protein needs for Ryan, a male office worker who weighs 80kg and has no additional dietary protein requirements:80 x 0.75 = 60
Structure of Proteins
Proteins, like fats and carbohydrates, are made up of carbon, oxygen and hydrogen. However, in addition, they also contain nitrogen.
They are made up of chains of single building blocks called amino acids.
Protein obtained from food cannot function in the body until it is broken down into these component parts.
Amino Acids
Around 20 amino acids can be found in different plant and animal sources. The body is able to produce 12 itself: these are referred to as non-essential amino acids as they do not need to be consumed through the diet. The remaining eight must be consumed through our diet - as the body is unable to produce them - and are therefore referred to as essential amino acids
Conditially essential amino acids
These are normally non-essential amino acids, but in times of stress - such as periods of intense exercise training or illness - the body may not be able to produce enough to meet its demands. One such amino acid is glutamine, which is commonly recommended for sports people exercising hard. Children are also unable to produce all of the non-essential amino acids, for example arginine and histidine, but instead of supplementation, a healthy diet should be recommended unless a medical practitioner suggests otherwise.
Essential amino acids
Leucine, Isoleucine, and Valine (known collectively as branched chain amino acids) Lysine Methionine Phenylalanine Threonine Tryptophan
Non essential amino acids
Alanine Arginine Asparagine Aspartic acid Cysteine Glutamic acid Glutamine Glycine Histidine Proline Serine Tyrosine
Protein metabolism
Amino acids circulating in the bloodstream and body tissues arrive there in two ways. Firstly through the breakdown of dietary protein into amino acids during the digestive process; providing the body with the essential amino acids. Secondly by the production of amino acids from nitrogen, carbohydrate metabolism, and the modification of other amino acids, providing the body with the non-essential amino acids.
Protein for energy
Each gram of protein provides 4 kcal of energy but, due to the range of other roles protein has in the body, it is not a major energy source in normal circumstances, and is only relied upon when carbohydrate stores run low. It is first broken down into amino acids before being converted through various steps into glucose. This process is known as gluconeogenesis, meaning ‘to make new glucose.
Classification of Protein
Complete protein foods are generally animal meat which contain all essential proteins, incomplete proteins are typically found in protein from plants.
The more essential amino acids in food the higher its biological value.
Complete protein sources
Dairy products eggs meat fish poultry
Incomplete protein sources
beans, lentils, peas, nuts (Legumes)
Barley, Bulgar wheat, oats, pasta, rice, bread (Cereal grains)
Protein for vegetarians
To ensure that protein requirements are met through plant-based sources, it is essential that a varied diet is consumed, containing the right combination of plant proteins. Combining a plant protein limited in certain amino acids with other plant proteins high in the same amino acids is an effective way of consuming what the body requires to function properly.
Examples: Peanut butter sandwich Tofu (with veg & rice) Chilli bean taco, Beans on toast, Musli with oats and nuts.
