0:16 Welcome to the sixth week of the course basics of food and nutrition and in this session we are going to deal about proteins which are the building blocks of life and nutrition. So at the end of this session you will be able to explain the structure, composition, properties and functions of proteins. Classify amino acids and proteins with suitable examples. Describe the digestion, absorption of proteins. Discuss protein nutrition including requirements, quality assessment and methods for improving protein quality. relate proteins to clinical and practical applications including protein estimation and protein energy malnutrition. So before going into the details of
1:03 protein its classification structure let's start with the history. So the origin of protein is in the year 1838 and the term protein was suggested by a Dutch chemist Moulder. He used it to describe the complex organic nitrogenous substances found in both animal and plant tissues. Derived from the Greek word proteio, the meaning of first importance, it tells or reflects the essential role of protein in life. Talking about the bodily composition, the proteins constitute approximately 3/4 of your body. that is roughly about
1:48 75%age. So what are its core functions? Proteins help in biochemical processes, biohysical processes, physiological processes. The usual and regular chemical reactions are assisted by proteins. The structure and physical properties of various systems is supported by protein and body functions and regulations are also governed by protein. Because protein is a major source of multiple components in your body. These are few examples. For example, the enzymes that is present inside the body which helps in various biochemical processes like pepsin is made up of protein. Similarly, important
2:34 components like hemoglobin which helps in oxygen transport is also made up of protein. The biohysical processes like collagen formation which helps in the structural support, actin and meiosin which helps in muscle contraction is also formed from protein and the physiological processes like blood coagulation wherein fibbrinogen which is a clotting factor and imunoglobulins that is required for immune defense is also made from protein. So these are all the core functions where protein is essential for life. Now let's see the chemical composition of protein. So when we talk about the
3:20 macronutrients, carbohydrate, fats and proteins, all three are made up of the basic structure which is carbon, oxygen and hydrogen. Protein has an additional component which is nitrogen. So the proteins are complex organic molecules made up of carbon, hydrogen, oxygen and nitrogen. Most of the proteins also contain sulfur and specific conjugated proteins. They also have phosphorus. So the picture shows the basic structure of proteins. There is an interesting concept because of the presence of nitrogen which is called as the nitrogen factor or the 16%age rule. So nitrogen
4:08 basically makes up to 16 percentage of protein and we can estimate the amount of protein in a food by measuring its nitrogen content. So the conversion factor is calculated as 100 by 16 which comes to 6.25. So what we do is to measure the nitrogen content and multiply it by 6.25 and you get the total protein content of that particular food. So this is called as the nitrogen factor. Talking about the physical and chemical properties, we will discuss about its amphoteric nature, the solubility and colloidal nature. So proteins can act as both acids and bases because they have
4:55 the NH2 group which is basic and CO group which is acidic and they help in the maintenance of body pH or they act as a buffer. So proteins help to keep your body pH stable. Talking about solubility, different proteins dissolve differently. Some proteins are soluble in water for example albamin. Some of them are soluble in salt example is globalin and some proteins like keratin and collagen is insoluble. So solubility can also be changed by adding acids or by changing the temperature. That is by changing the
5:40 pH and temperature the solubility can be changed. So some protein dissolves in water, some in salt and some do not dissolve. Talking about the colloidal nature, proteins are larger molecules. So it cannot pass through cell membrane easily. It needs carriers or coransporters for the transport. So because of this colloidal nature, it helps in osmotic balance and it can also form gels. For example, the cooked egg. So when you cook the egg you can see the change of state into a jelly formation. That's because of the property of colloidal nature of proteins. Now let's see the classifications. So when we talk about proteins, there
6:27 are two types of classifications that's usually given which is a classification of protein itself and classification of amino acids. We'll first see the classification of proteins. So the major three classifications are simple proteins, conjugated proteins and derived proteins. So what are simple proteins? When hydrayed they yield only amino acids. Examples albamin, globulins, glutalins, prolamins, fibrous proteins, histones, proamins. What is conjugated protein? It is a combination of protein and a nonproin group. For example, nucleoproteins. It's a combination of nucleic acids and protein. Glyoprotein is a combination of
7:14 carbohydrate and protein. And other examples like phosphoproins, chromoproins and leithoproins. Now what is derived proteins? The proteins which are derived from simple or conjugated proteins either by dennaturation which is called as a primary derived proteins or by hydrarolysis which is a secondary derived proteins. Again the examples for them are proteins, metaproins and coagulated proteins for primary derived proteins and proteiosis pepones peptides for the secondary derived proteins. So this is the basic classification of proteins. Now when we talk about the classification of amino acids, it's based on
8:00 six different criterias. So the first is based on the properties of the R group. The R group is the side chain in an amino acid. So based on its properties, it is divided into non-polar polar uncharged acidic basic, aromatic and sulfur containing amino acids. It is also classified based on the position of primary amino group which is alpha amino group, beta amino group and gamma amino group. It is also classified based on the stereochemistry of alphaarbon. That's the structure um of the particular amino acid which is the L amino acids and D amino acids and it is also classified based on the net charge whether it is positively
8:48 charged or negatively charged or neutral. So we have three under that which is neutral, acidic and basic. Talking about the nutrition, we have classifications as essential amino acids, non-essential amino acids and conditionally essential amino acids. And based on the metabolic fate, what is the purpose of that particular amino acid? It is classified as gluccogenic, ketogenic, gluccogenic and ketogenic amino acids. Here I would like to signify the nutrition classification in this particular course because this is how the nut a nutritionist or in food based evaluation we classify the amino acids as essential non-essential and
9:35 conditionally essential amino acids. So now let's see what are they. So based on nutrition we have essential amino acids. These are the amino acids that is produced. It is not produced inside your body and it has to be taken from the food and that is why the word essential has been given. Non-essential amino acids are those which is produced inside your body and it is not much required from the food. And conditionally essential amino acids are those amino acids that were non-essential amino acids but due to certain conditions like stress, burns, trauma etc. the amino acid becomes an essential amino acid at that particular
10:21 period. So that is why the name conditionally essential amino acids. So we have a good list of essential amino acids like histadine, isolucin, leucin, lysine methionin phenylin thriionin tryptophan and balin. Under conditionally essential amino acids we have arginine, cyin, glutamine and so on. And on non-essential amino acids we have alanine, aspartic acid, glutamic acid, serin etc. So this is the basic classification of amino acids. So now we have seen the structure, the functions and the classification. Let's move on to protein digestion and absorption. So what happens when you eat a protein richch food or to the protein that you have consumed? The basic
11:08 digestion is called as hydraysis because you need water for the protein digestion and that's why the protein digestion is otherwise termed as hydrarolysis of protein and you require enzymes and they are called as proteasis. Now this digestion occurs in two phases which is gastric phase and intestinal phase. As the name suggests gastric phase happens in the stomach and intestinal phase happens in the small intestine. So this picture can actually show the protein digestion process very simply. So it's the hydrarolysis that's happening and what happens when you put the food in your mouth. The dietary proteins are in your mouth and there is
11:53 no significant protein digestion because protein digestion does not start in your mouth. We don't have enzymes. So only breakdown of the food particles happens. Now this food enters into the stomach. Now it denatures and partially gets hydrayed by the HCL that is hydrochloric acid which is secreted in the stomach and it activates the pepsin which helps in the degradation or dennaturation of the protein. Now the denatured proteins enters into the next system that is the small intestine where the protein is digested further and it becomes small peptides and amino acids. Now who helps here is
12:41 the proteasis that is secreted like trison kimotriin caroxyeptidase aminopeptidase deptidase. After this digestion, the whole protein that you have consumed gets converted into amino acids which is a simpler form of protein or the by or the product of protein digestion. Now this has to get absorbed. So it goes to the intestinal lining and amino acids are getting absorbed into the bloodstream. So the protein that you have taken is converted to polyeptides and then into peptides and amino acids. Now what happens to this amino acids? It gets further absorbed. So where is the site?
13:27 The site of absorption is the small intestine. So amino acids are absorbed mainly in the small intestine. And talking about the mechanism, there is going to be an active transport that's going to happen. So when I say active transport it means that it is energy dependent that is the transportation requires energy in terms of ATP. So energy ATP adinosentin triphosphate is used to move the amino acids into the intestinal cells and then they are transported into the blood. There are specific carriers that is required for each amino acid. So for every amino acid that is getting transported you need specific carriers and they are different for different
14:13 amino acids and there are two key factors which we need to remember that is the L isomers that is a naturally occurring amino acids will get transported faster than the D isomers which is the synthetic or not naturally occurring amino acids. And the second point that we need to remember here is it requires sodium and vitamin B6 that is pyrooxin for the transportation. Sodium is essential for co coransportation or it acts as a coransporter and vitamin B6 supports the amino acid metabolism and absorption. So these two nutrients are also important.
15:01 So this is about the absorption of amino acids. Now we have seen what is protein, what are its functions, what happens when you consume the protein, what is happening in the digestion and absorption. Now we will see certain nutritional aspects in relation to protein. So the nutritional aspects of protein is about what are the types of protein that is present in the foot. So you have different types based on its quality. The three different categories are complete protein, partially incomplete protein and incomplete protein. So what is complete protein is it contains all essential amino acids in adequate amounts. Example egg, milk, meat, fish
15:49 and soy. Partially incomplete proteins are those that contains all essential amino acid but one or more are present in limited amounts like wheat, rice and pulses. Incomplete proteins they lack one or more essential amino acids like gelatin or zane which is a maze protein. So what is the nutritional significance of these three categories? When I eat a complete protein, it means it's going to support the growth, tissue repair and maintenance. But when I eat a partially incomplete protein alone, it can maintain life but may not adequately support the growth. And when I eat incomplete protein, the protein quality of pro uh the
16:36 protein quality is questionable and it cannot support the normal growth and maintenance. There are also different evaluations seen to assess the protein quality. Few evaluations that have come up till now is the protein efficiency ratio PER, digestibility coefficient DC, DAS that is digestible independent amino acid score, biological value, net protein utilization, chemical score and PD CAS. So we have various formulas for calculating and assessing the protein quality of the
17:22 food and based on the interpretation we can say that the protein quality of the food is good poor or fair. The PR actually focuses on how much the protein has helped in the growth. Whereas the DC that is the digestibility coefficient tells how well the protein gets digested inside your body. Methods like CS DAS and PDAS tells the quality of amino acids and methods like biological value net protein utilization tells the utilization of the protein in the body. So these aspects can be utilized when a food is prepared or to
18:07 know the protein quality of what food you are consuming. The next concept is nitrogen balance. This is a clinical measure which is used to understand the protein metabolism. So this nitrogen balance is nothing but the intake and output. So nitrogen equilibrium is attained when intake equals the output. It's usually seen in healthy adults. Positive nitrogen balance it's the intake when it exceeds the output. Then it is called as positive nitrogen balance usually occurs during the growth phase, pregnancy, recovery from illness. The negative nitrogen balance is when the output exceeds the intake. When the body needs
18:53 more protein and it is being utilized and it is the nitrogen is getting wasted in your fcal or urine then it is negative nitrogen balance. It indicates that the body needs more protein. This happens in certain conditions like starvation, fever and severe injury. Now another important aspect of protein for a nutritionist is improving protein quality. So when I eat a proteinrich food, I should be knowing the quality of protein and I should also know how to improve the quality of protein. So one method by which we can improve our protein intake is by mutual supplementation. It is otherwise called
19:40 as a blending or complementation process. What's the concept? It's combining two or more incomplete proteins so that the excess amino acid in one makes up for the deficiency in the other. For example, the serial pulse synergy. So cereals like rice and wheat, they are low in lysine but rich in methionine. Whereas pulses or legumes are low in methionine but rich in lysine. So to obtain all the essential amino acids you can consume both cereals and pulses together so that there is no deficiency in any particular amino acid. So this is one method by which you can improve the quality of protein. The
20:27 other method is fortification which is supplementation with pure amino acids. So the concept behind this is directly adding the specific limiting essential amino acid to a food product during processing. So this application is seen uh in various food products like supplementing wheat flour with lysine, supplementing infant formulas with methionin or tryptophen to match the profile of human milk. So this procedure or this method is often used in large scale food programs to combat malnutrition without changing the dietary habits. So when you identify a group of people or a com or a large scale number of people
21:14 and you find that there is malnutrition to address that issue these kind of steps can be taken. Right now we have uh found how to identify the quality of protein. Now how will you determine what is the protein requirement for you? So based on a factorial method which includes the total nitrogen losses in the body you can actually determine the protein requirements. So for which you require UFSG that is the urinary loss nitrogen lost in urine. the fal loss which is unabsorbed nitrogen and skin loss sweat hairs skin and the growth the extra need for growth pregnancy or lactation. So
22:02 you total this up and you get the protein requirement. So basically the total protein requirement is the sum of all losses and the growth needs. Now with this as the basic concept ICMR N guidelines has been formulated to know or to advocate the protein requirements for Indian adults. So the average protein requirement for an Indian adult is approximately 0.66 g per kg per day. That is you are supposed to give 0.66 g for every kg in a day. The safe intake level is approximately 0.83 83 g per kg per day
22:48 and the energy contribution that has to come from protein is 10 to 15%age that is from the overall energy I need to get 10 to 15%age of energy from proteins now where do you get it from from the dietary sources like cereals pulses and milks for vegetarian and for non-ve Vegetarian it is fish, poultry, meat they are high quality protein. Now when I say high quality protein from the previous slides you would understand the what is a quality protein. So these are the common sources from where you get the protein from diet.
23:35 Now what happens if there is a deficiency? So when you don't take the adequate protein requirements as per the recommendation you end up with lot of problems very common and a basic protein um issue that we can talk in this particular course is the protein energy malnutrition. The types of deficiencies that comes in PEM which is mostly occurring in children is first one is the quashio. Quashi occurr mainly protein deficiency and marasmus is a protein and calorie deficiency and there is a combination of features also seen in various children which is marasmic quashi the clinical features are edema moon face fatty liver hair and
24:24 skin changes and apathy in quashi since it's only protein deficiency and we all know now that the protein is important for fluid balance there is going to be an imbalance when there is a deficiency and hence fluid accumulation is a very uh a common symptom that you can see in quashio like edema and moon phase whereas marasmus shows severe wasting skin and bones loss of fat and muscle and no edema is seen here the child will be alert but very hungry the biochemical changes that happens in kashi is decreased serum albamin and fatty liver and in maras Arasmus the near normal albamin and no fatty liver. So quasi is basically a protein
25:10 deficiency and marasmus is a total starvation which includes both protein and calories. So it's a very common problem that is prevalent when there is going to be protein inadequacy. Now let's see a detail on the protein sources which is also recommended by the ICMR nin the smart protein choices. Now how will you eat protein in such a way that you got you get all the essential amino acids from the concepts that we have seen before you can uh well understand these points. So prioritize whole foods. So you take diverse uh foods from the food groups
25:57 include lot of sources like chana, rajma, peas and other protein rich sources. Concentrate more on plant-based focus because they are going to be the top protein sources. Optimal ratios. This is very important. We need to take serial pulses in a ratio of 3 is to1 so that you get all the essential amino acids. Now you can remember the concept I told before on the blending where you can improve the protein quality. So optimal ratios will help you achieving the uh essential amino acid. Moderate animal protein. This is to have some control on fat. So you can include eggs, fish and lean meat and try to avoid red
26:44 meat so that you restrict on the excess amount of fat intake. Whereas eggs, fish and lean meat will give you a very good quality and high biological value protein. And the other options are dairy that is milk and its products. So inclusion of these not only gives you protein but also calcium. Now the sources to include to consolidate is legumes and pulses, nuts and seeds, dairy products and animal sources. Now what are you supposed to avoid? Protein powders. The guidelines tells you that you are not supposed to take or consume protein powders unless recommended and excessive amount of red meats has to be avoided to control the fat intake. So
27:32 these are the foods to be avoided or at least limited. To summarize, proteins are the building blocks of life and nutrition. What are they? They are made of amino acids and they contain carbon, hydrogen, oxygen, nitrogen. Sometimes they also have sulfur and phosphorus. What are the functions essential for life processes especially in terms of growth and repair, enzymes and hormones, immunity, fluid and blood balance, digestion and absorption. The organs that are involved here are stomach and small intestine for digestion where the
28:18 proteins are converted to polyeptides and polyeptides to amino acids. And small intestine is where the absorption takes place and the amino acids are absorbed into the bloodstream by an active transport mechanism. Talking about the quality depends on the essential amino acids present in the food and its digestibility. combines food or you can fortify the food to improve the quality of protein. Talking about the deficiency we saw it leads to protein energy malnutrition. Examples were quashi and marasmus. So the key key takeaway is eat balanced good quality protein for growth and health and also for the wellbeing. Thank
29:05 you.
