Experemint 10 As described in the lab manual:
Analysis of Proteins 6. Twenty different types of amino acids occur naturally in proteins. Proteins differ from each other according to the type, number and sequence of amino acids that make up the polypeptide backbone. As a result they have different molecular structures, nutritional attributes and physiochemical properties.
Proteins are important constituents of foods for a number of different reasons. They are a major source of energy, as well as containing essential amino-acids, such as lysine, tryptophan, methionine, leucine, isoleucine and valine, which are essential to human health, but which the body cannot synthesize.
Proteins are also the major structural components of many natural foods, often determining their overall texture, e. Isolated proteins are often used in foods as ingredients because of their unique functional properties, i. Typically, proteins are used as gelling agents, emulsifiers, foaming agents and thickeners.
Many food proteins are enzymes which are capable of enhancing the rate of certain biochemical reactions. These reactions can have either a favorable or detrimental effect on the overall properties of foods. Food analysts are interested in knowing the total concentration, type, molecular structure and functional properties of the proteins in foods.
Determination of Overall Protein Concentration 6. Kjeldahl method The Kjeldahl method was developed in by a brewer called Johann Kjeldahl. A food is digested with a strong acid so that it releases nitrogen which can be determined by a suitable titration technique.
The amount of protein present is then calculated from the nitrogen concentration of the food. The same basic approach is still used today, although a number of improvements have been made to speed up the process and to obtain more accurate measurements.
It is usually considered to be the standard method of determining protein concentration. Because the Kjeldahl method does not measure the protein content directly a conversion factor F is needed to convert the measured nitrogen concentration to a protein concentration.
A conversion factor of 6. The Kjeldahl method can conveniently be divided into three steps: Principles Digestion The food sample to be analyzed is weighed into a digestion flask and then digested by heating it in the presence of sulfuric acid an oxidizing agent which digests the foodanhydrous sodium sulfate to speed up the reaction by raising the boiling point and a catalyst, such as copper, selenium, titanium, or mercury to speed up the reaction.
Digestion converts any nitrogen in the food other than that which is in the form of nitrates or nitrites into ammonia, and other organic matter to C02 and H The solution in the digestion flask is then made alkaline by addition of sodium hydroxide, which converts the ammonium sulfate into ammonia gas: The low pH of the solution in the receiving flask converts the ammonia gas into the ammonium ion, and simultaneously converts the boric acid to the borate ion: The following equation can be used to determine the nitrogen concentration of a sample that weighs m grams using a xM HCl acid solution for the titration: A blank sample is usually ran at the same time as the material being analyzed to take into account any residual nitrogen which may be in the reagents used to carry out the analysis.
Once the nitrogen content has been determined it is converted to a protein content using the appropriate conversion factor: Advantages and Disadvantages Advantages. The Kjeldahl method is widely used internationally and is still the standard method for comparison against all other methods.
Its universality, high precision and good reproducibility have made it the major method for the estimation of protein in foods.
It does not give a measure of the true protein, since all nitrogen in foods is not in the form of protein. Different proteins need different correction factors because they have different amino acid sequences.
The use of concentrated sulfuric acid at high temperatures poses a considerable hazard, as does the use of some of the possible catalysts The technique is time consuming to carry-out. Enhanced Dumas method Recently, an automated instrumental technique has been developed which is capable of rapidly measuring the protein concentration of food samples.
This technique is based on a method first described by a scientist called Dumas over a century and a half ago.
It is beginning to compete with the Kjeldahl method as the standard method of analysis for proteins for some foodstuffs due to its rapidness. General Principles A sample of known mass is combusted in a high temperature about oC chamber in the presence of oxygen.
The CO2 and H2O are removed by passing the gasses over special columns that absorb them.Lab # Digestive Physiology p.1 Lab # Digestive Physiology and chemical digestion, whereby through the use of enzymes released into the digestive tract large chyme through chemical and physical digestion in the stomach aids this process.
The proteases. Rock River Laboratory uses approved physical, chemical, enzymatic, volumetric, and gravimetric techniques to measure core nutrients, vitamins, minerals, or digestion of feed and forage samples.
A sample is dried and ground down to around a ground-coffee size to ensure sample uniformity.
REVIEW SHEET EXERCISE 8 Chemical and Physical Processes of Digestion Carbohydrate Digestion The following questions refer to Activity 1: Assessing Starch Digestion by Salivary. A high scoring A practical report for outcome 3 of biology. Very detailed responses which outline how you can complete your own assignment to a high standard. Includes a background, introduction, methodology, results, discussion and conclusion for an experiment that investigated how substrate concentration affected the rate of enzyme activity. PhysioEx ™ Laboratory Simulations in Physiology is an easy-to-use laboratory simulation software and lab manual that consists of 12 exercises containing 66 physiology lab activities that can be used to supplement or substitute wet labs. PhysioEx allows you to repeat labs as often as you like, perform experiments without harming live animals, and conduct experiments that are difficult to.
Processes of Digestion - Chemical and Physical Processes of Digestion Exercise 39A / 39 (begins page in 8th edition, page in 9th and 10th chemical and physical processes of digestion lab report questions activity 1 what is the difference between the iki assay and benedicts assay?
iki . Thousands of chemical reactions take place during digestion. As soon as you put food in your mouth, an enzyme in your saliva called amylase starts to break down sugars and other carbohydrates into simpler forms your body can absorb.
Digestion Lab Report: Digestion Lab: educationalvideo: Egg Cell Experiment. Ice Cream Lab. Questions: What is a physical reaction?
What is matter? What is a molecule? Is ice-cream an example of a physical change or a chemical change?
2.) Why is salt required to make ice-cream? What does salt do to the ice and the bag mixtures? Unit 9: Physical, Chemical and Energy Changes in Digestion. Objectives: 6a: distinguish between physical and chemical changes in matter Energy Transformations in Digestion Lab.
Energy Transformations Lab CleanUp. Energy Transformations in Digestion. QUIZLET: U9 Organic vs Inorganic.