A quantitative limitation exists as to how much muscle protein the body can Hence, research has focused on revealing the relationship between protein .. due to the enormous pool of body water buffering the minor disturbances in alanine. Structure of Water | Organic Molecules | Learning Objectives | Terms | Review Questions | Links This relationship is shown in Figure 1. .. By restricting the intakes of carbohydrates and fats, the body is forced to draw on its own The primary structure of a protein is the sequence of amino acids, which is directly related to. What is the relationship between body proteins and water Table for Individual from NUTR at Pennsylvania State University.
Ingestion of excess protein exerts an unwanted load to the body and therefore, it is important to find the least amount of protein that provides the maximal hypertrophic stimulus. Hence, research has focused on revealing the relationship between protein intake dose and its resulting stimulation of muscle protein synthesis response. In addition to the protein amount, the protein digestibility and, hence, the availability of its constituent amino acids is decisive for the response. In this regard, recent studies have provided in-depth knowledge about the time-course of the muscle protein synthetic response dependent on the characteristics of the protein ingested.
The effect of protein intake on muscle protein accretion can further be stimulated by prior exercise training. Presently, our knowledge is based on measures obtained in standardized experimental settings or during long-term intervention periods.
However, to improve coherence between these types of data and to further improve our knowledge of the effects of protein ingestion, other investigative approaches than those presently used are requested.
Protein, amino acids, muscle protein synthesis, muscle protein breakdown, resistance exercise 1. Introduction The preservation and development of skeletal muscle mass is essential for maintenance of health and life quality. Due to its volume, the skeletal muscle makes up the primary site for disposal of nutrients and energy consumption in the body and, hence, plays an essential role for weight regulation.
Therefore, skeletal muscle mass is important in protecting against the development of metabolic conditions such as obesity, hyperlipidemia, cardiovascular disease, and type II diabetes [ 12 ]. Furthermore, skeletal muscle makes up a huge storage of amino acids AAwhich, when recruited, are crucial for making acute phase proteins in the fight against critical illness or in wound healing following severe trauma [ 1 ].
Limiting the loss of skeletal muscle mass during periods of illness or injury is essential to decrease patient morbidity and increase recovery outcome [ 3 ]. In this review, we discuss protein intake with special emphasis on type and amount alone and in combination with exercise regimens that induce changes in muscle mass with the purpose to link findings from acute changes in muscle protein turnover to long-term changes in muscle mass. Finally, we will discuss in which directions future research in this field should focus.
Whole-Body Effects of Protein Intake The daily requirement for dietary protein is defined as the minimum amount resulting in a whole-body net balance of zero. Since excessive protein intake adds load on the kidneys, proteins should not be consumed in overly amounts and should be a matter of concern, especially in elderly individuals [ 4 ]. Therefore, research to address the exact amount to meet the requirements for body remodeling is crucial. The protein requirement has been vigorously debated due to difficulties in specifying which parameter s e.
Additionally, the protein requirement depends on quality—that is AA composition and digestibility—and physical activity level. There are four classes of macromolecules polysaccharides, triglycerides, polypeptides, nucleic acids. These classes perform a variety of functions in cells. Carbohydrates have the general formula [CH2O]n where n is a number between 3 and 6.
Note the different CH2O units in Figure 8. Carbohydrates function in short-term energy storage such as sugar ; as intermediate-term energy storage starch for plants and glycogen for animals ; and as structural components in cells cellulose in the cell walls of plants and many protistsand chitin in the exoskeleton of insects and other arthropods.
Sugars are structurally the simplest carbohydrates. They are the structural unit which makes up the other types of carbohydrates. Important monosaccharides include ribose C5H10O5glucose C6H12O6and fructose same formula but different structure than glucose. The chain left and ring center and right method of representing carbohydrates. We classify monosaccharides by the number of carbon atoms and the types of functional groups present in the sugar.
For example, glucose and fructose, illustrated in Figure 9, have the same chemical formula C6H12O6but a different structure: This functional group difference, as small as it seems, accounts for the greater sweetness of fructose as compared to glucose.
Models of glucose and fructose. In an aqueous solution, glucose tends to have two structures, a alpha and b betawith an intermediate straight-chain form shown in Figure The a form and b form differ in the location of one -OH group, as shown in Figure 9. Glucose is a common hexose, six carbon sugar, in plants. The products of photosynthesis are assembled to form glucose. Energy from sunlight is converted into and stored as C-C covalent bond energy.
This energy is released in living organisms in such a way that not enough heat is generated at once to incinerate the organisms. One mole of glucose yields Kcal of energy.
A calorie is the amount of heat needed to raise one gram of water one degree C. A Kcal has times as much energy as a cal. Glucose is also the form of sugar measured in the human bloodstream. D-Glucose in various views stick and space-filling from the web. Right image from Purves et al. Disaccharides are formed when two monosaccharides are chemically bonded together. Sucrose, a common plant disaccharide is composed of the monosaccharides glucose and fructose.
Lactose, milk sugar, is a disaccharide composed of glucose and the monosaccharide galactose. The maltose that flavors a malted milkshake and other items is also a disaccharide made of two glose molecules bonded together as shown in Figure Formation of a disaccharide top by condensation and structure of two common disaccharides. Polysaccharides are large molecules composed of individual monosaccharide units. A common plant polysaccharide is starch shown in Figure 12which is made up of many glucoses in a polypeptide these are referred to as glucans.
Two forms of polysaccharide, amylose and amylopectin makeup what we commonly call starch. The formation of the ester bond by condensation the removal of water from a molecule allows the linking of monosaccharides into disaccharides and polysaccharides.
Glycogen see Figure 12 is an animal storage product that accumulates in the vertebrate liver. Images of starch topglycogen middleand cellulose bottom. Cellulose, illustrated in Figure 13 and 14, is a polysaccharide found in plant cell walls.
Cellulose forms the fibrous part of the plant cell wall. In terms of human diets, cellulose is indigestible, and thus forms an important, easily obtained part of dietary fiber. As compared to starch and glycogen, which are each made up of mixtures of a and b glucoses, cellulose and the animal structural polysaccharide chitin are made up of only b glucoses.
The three-dimensional structure of these polysaccharides is thus constrained into straight microfibrils by the uniform nature of the glucoses, which resist the actions of enzymes such as amylase that breakdown storage polysaccharides such a starch. Structure of cellulose as it occurs in a plant cell wall. This image is copyright Dennis Kunkel at www.
Lipids are involved mainly with long-term energy storage. They are generally insoluble in polar substances such as water. Secondary functions of lipids include structural components as in the case of phospholipids that are the major building block in cell membranes and "messengers" hormones that play roles in communications within and between cells.
Lipids are composed of three fatty acids usually covalently bonded to a 3-carbon glycerol. Some examples of fatty acids are shown in Figure Fatty acids can be saturated meaning they have as many hydrogens bonded to their carbons as possible or unsaturated with one or more double bonds connecting their carbons, hence fewer hydrogens.
A fat is solid at room temperature, while an oil is a liquid under the same conditions. The fatty acids in oils are mostly unsaturated, while those in fats are mostly saturated. Saturated top and middle and unsaturated bottom fatty acids.
The term staurated refers to the "saturation" of the molecule by hydrogen atoms. Fats and oils function in long-term energy storage. Animals convert excess sugars beyond their glycogen storage capacities into fats.
CHEMISTRY II: WATER AND ORGANIC MOLECULES
Most plants store excess sugars as starch, although some seeds and fruits have energy stored as oils e.
Fats thus store six times as much energy as glycogen. Diets are attempts to reduce the amount of fats present in specialized cells known as adipose cells that accumulate in certain areas of the human body. By restricting the intakes of carbohydrates and fats, the body is forced to draw on its own stores to makeup the energy debt.
The body responds to this by lowering its metabolic rate, often resulting in a drop of "energy level. Another use of fats is as insulators and cushions. The human body naturally accumulates some fats in the "posterior" area. Subdermal "under the skin" fat plays a role in insulation. Phospholipids and glycolipids are important structural components of cell membranes.
Phospholipids, shown in Figure 16, are modified so that a phosphate group PO4- is added to one of the fatty acids. The addition of this group makes a polar "head" and two nonpolar "tails".
Waxes are an important structural component for many organisms, such as the cuticle, a waxy layer covering the leaves and stems of many land plants; and protective coverings on skin and fur of animals. Structure of a phospholipid, space-filling model left and chain model right. Most mention of these two types of lipids in the news is usually negative.
Cholesterol, illustrated in Figure 17, has many biological uses, it occurs in cell membranes, and its forms the sheath of some types of nerve cells. However, excess cholesterol in the blood has been linked to atherosclerosis, hardening of the arteries. Recent studies suggest a link between arterial plaque deposits of cholesterol, antibodies to the pneumonia-causing form of Chlamydia, and heart attacks.
The plaque increases blood pressure, much the way blockages in plumbing cause burst pipes in old houses. Structure of four steroids. Proteins are very important in biological systems as control and structural elements. Control functions of proteins are carried out by enzymes and proteinaceous hormones. Enzymes are chemicals that act as organic catalysts a catalyst is a chemical that promotes but is not changed by a chemical reaction.
Water Retention & Protein Intake
Click here for an illustrated page about enzymes. Structural proteins function in the cell membrane, muscle tissue, etc.
The struucture of a generalized aminio acid as well as the specific structures of the 20 biological amino acids are shown in Figure 18 and 19 respectively.
The R indicates the variable component R-group of each amino acid. Alanine and Valine, for example, are both nonpolar amino acids, but they differ, as do all amino acids, by the composition of their R-groups.
All living things and even viruses use various combinations of the same twenty amino acids. A very powerful bit of evidence for the phylogenetic connection of all living things. Structure of an amino acid. Structures in the R-groups of the twenty amino acids found in all living things.
Amino acids are linked together by joining the amino end of one molecule to the carboxyl end of another. Removal of water allows formation of a type of covalent bond known as a peptide bond. This process is illustrated in Figure Formation of a peptide bond between two amino acids by the condensation dehydration of the amino end of one amino acid and the acid end of the other amino acid. The above image is from http: Amino acids are linked together into a polypeptide, the primary structure in the organization of proteins.
The primary structure of a protein is the sequence of amino acids, which is directly related to the sequence of information in the RNA molecule, which in turn is a copy of the information in the DNA molecule. Changes in the primary structure can alter the proper functioning of the protein.
Protein function is usually tied to their three-dimensional structure. The primary structure is the sequence of amino acids in a polypeptide. The secondary structure is the tendency of the polypeptide to coil or pleat due to H-bonding between R-groups. The tertiary structure is controlled by bonding or in some cases repulsion between R-groups.
Chemistry for Biologists: Proteins
Tertiary structure of an HIV protein and its similarity to gamma interferon are shown in Figure Many proteins, such as hemoglobinare formed from one or more polypeptides. Such structure is termed quaternary structure.
Structural proteins, such as collagen, have regular repeated primary structures. Like the structural carbohydrates, the components determine the final shape and ultimately function.
Collagens have a variety of functions in living things, such as the tendons, hide, and corneas of a cow. Keratin is another structural protein. It is found in fingernails, feathers, hair, and rhinoceros horns.
Microtubules, important in cell division and structures of flagella and cilia among other thingsare composed of globular structural proteins. HIV p17 protein and similarities of its structure to gamma interferon. Image is from http: Nucleic acids are polymers composed of monomer units known as nucleotides.
There are a very few different types of nucleotides. Nucleotides, shown in Figure 22, consist of a sugar, a nitrogenous base, and a phosphate.
The sugars are either ribose or deoxyribose. They differ by the lack of one oxygen in deoxyribose. Both are pentoses usually in a ring form. There are five nitrogenous bases. Purines Adenine and Guanine are double-ring structures, while pyrimidines Cytosine, Thymine and Uracil are single-ringed.
Structure of two types of nucleotide. We will learn more about the DNA structure and function later in the course click here for a quick look [actually take all the time you want!