We tend to think of protein as a mass noun: a homogeneous substance, something that your diet should contain in a certain proportion. But if you ever work in a molecular biology lab (say, for a summer internship), protein may start to look very different to you.
How so? Well, you may see firsthand that protein isn’t just a single substance. Instead, there are lots and lots of different proteins in an organism, or even in a single cell. They come in every size, shape, and type you can imagine, and each one has a unique and specific job. Some are structural parts, giving cells shape or helping them move. Others act as signals, drifting between cells like messages in a bottle. Still others are metabolic enzymes, putting together or snapping apart biomolecules needed by the cell. And, odds are, one of these unique molecular players will become yours for the duration of your research!
Proteins are among the most abundant organic molecules in living systems and are way more diverse in structure and function than other classes of macromolecules. A single cell can contain thousands of proteins, each with a unique function. Although their structures, like their functions, vary greatly, all proteins are made up of one or more chains of amino acids. In this article, we will look in more detail at the building blocks, structures, and roles of proteins.
How much protein do I need?
According to nutritional recommendations, A normal person should get about 0.8 g protein / kg body weight a day1. Are you a physically active person? Then you may need more protein! Physical exercise increases the use of protein in the body. In fact, athletes are recommended to eat twice as much protein. However, eating more protein than 1.6 g / kg / day does not appear to have any additional effect on strength and muscle growth. In other words, you should be somewhere between 0.8 g – 1.6 g protein / kg body weight / day. So if you weigh 70kg, you should be consuming between 56 – 112 grams of protein every day. That’s around 3 chicken breasts.
Protein quality:
There are multiple systems which rate proteins by their serviceability to an organism based on their relative percentage of amino acids and, in some systems, the eatable of the protein source. They include biological value, net protein utilization, and PDCAAS (Protein Digestibility Corrected Amino Acids Score) which was developed by the FDA as a modification of the Protein efficiency ratio (PER) method. The PDCAAS rating was adopted by the US Food and Drug Administration (FDA) and the Food and Agricultural Organization of the United Nations/World Health Organization (FAO/WHO) in 1993 as “the preferred ‘best'” method to determine protein quality. These organizations have suggested that other methods for evaluating the quality of protein are inferior. In 2013 FAO proposed changing to Digestible Indispensable Amino Acid Score.
Dietary recommendations:
According to US & Canadian Dietary Reference Intake guidelines, women aged 19–70 need to consume 46 grams of protein per day while men aged 19–70 need to consume 56 grams of protein per day to minimize risk of deficiency. These Recommended Dietary Allowances (RDAs) were calculated based on 0.8 grams protein per kilogram body weight and average body weights of 57 kg (126 pounds) and 70 kg ((154 pounds), respectively. However, this recommendation is based on structural requirements but disregards use of protein for energy metabolism. This requirement is for a normal sedentary person. In the United States, average protein consumption is higher than the RDA. According to results of the National Health and Nutrition Examination Survey (NHANES 2013–2014), average protein consumption for women ages 20 and older was 69.8 grams and for men 98.3 grams/day.
Protein deficiency:
Protein deficiency and malnutrition (PEM) can lead to variety of ailments including Intellectual disability and kwashiorkor.Symptoms of kwashiorkor include apathy, diarrhea, inactivity, failure to grow, flaky skin, fatty liver, and edema of the belly and legs. This edema is explained by the action of lipoxygenase on arachidonic acid to form leukotrienes and the normal functioning of proteins in fluid balance and lipoprotein transport
Results and discussion:
n this section, the hydro-thermal histories followed by the liquid droplets and the air during drying are simulated by the model of a spray-drying process and analyzed (adapted from Bernard et al., 2006, Bernard et al., 2008).
the time evolution of product temperature Tp and product moisture content np in a dry basis (kg of water per kg of dry matter) for the four spray-drying operating conditions. We observe a long period during which the product temperature