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Transcript of Human Biochemistry
m = Mass of the water
c = Heat capacity (4.18 kJ mol- for water)
ΔT = Change in temperature of the water Proteins are natural polymers that make up about 15% of our bodies. They are made up of Carbon, Hydrogen, Oxygen, Nitrogen, and sometimes Sulfur.
Their primary use is to provide amino acids, which are used to produce new proteins for growth and repair of body tissues and to make hormones, enzymes, and antibodies. Proteins are polymeric substances made up of long molecules formed by sequences amino acids, which contain a carboxyl group (-COOH) and an amino group (-NH2).
The R group can be hydrogen, and alkyl group, or a complex substitute. All amino acids in natural proteins are 2-amino acids. This is because the amino acid group is attached to the 2-carbon atom. B.2.1 Draw the general formula of 2-amino acids. B.2.3 Describe the condensation reaction of 2-amino acids to form polypeptides Because amino acids have a carboxyl group and an amino group, they can undergo condensation reactions to form substituted amides.
The product is a dipeptide, which is made up of two amino acids joined by a peptide bond. Water is the other product formed in the process.
Two amino acids can give two different products depending which has the free amino end and which has the free carboxyl end. Different tripeptides can be formed using three different amino acids, if each amino acid is used only once.If a compound contains many of these peptide bonds, it is a polypeptide, which becomes a protein.The 20 naturally occurring amino acids can undergo condensation reactions to produce a wide variety of proteins. H H H N C C O OH R (B.2.4) Describe and explain the primary, secondary, tertiary, and quaternary structure of proteins. PRIMARY STRUCTURE is the sequence of amino acid residues that form the protein.
This is indicated by using a three-letter code.
For example, a tripeptide containing lysine, glycine, and leucine would be lys-gly-leu.
Each type of protein in a biological organism has its own unique primary sequence of amino acids, which sequence gives the protein its ability to carry out its characteristic functions. SECONDARY STRUCTURE is the manner in which a polypeptide folds itself, due to intramolecular hydrogen bonding, in particular patterns that repeat themselves.Two features that are found in the structure are the a-helix and the B-pleated sheet. In the a-helix structure, the peptide chain resembles a right handed spiral staircase, called a helix. It maintains it’s shape through regular intramolecular hydrogen bonds. The H-bonding in the helix is parallel to the axis of the helix. In the beta-pleated sheet, several different polypeptide chains are bound together by hydrogen bonds to create an ordered alignment of protein chains where the H-bonding is perpendicular to the sheet structure giving it a repeating, pleated pattern.
(If a particular part of a polypeptide chain does not exhibit a repeating pattern it is said to contain random coils.) TERTIARY STRUCTURE is the folding or curling due to the interaction between the sequence of amino acids that maintains the three dimensional shape of the protein.The amino acid arranges itself to form the unique twisted or folded shape.There are four ways for the the amino acid chains to interact and stabilize their tertiary shapes:
1. Covalent bonding.
2. Hydrogen bonding between –NH2 and -COOH groups on the side chain.
3. Salt bridges between –N+H3 and –COO groups.
4. The R group side chain affects the 3D structure of the resulting proteins depending on whether or not they’re polar. QUATERNARY STRUCTURE occurs only in proteins that are composed of more than one polypeptide chain which are held together by non-covalent bonds.These consist of hydrophobic interactions, hydrogen bonding, and ionic bonding.When a protein consists of more than one polypeptide chain, each is called a subunit.Quaternary structure is how the polypeptide subunits are held together in a more complex 3D arrangement. B.2.5 Explain how proteins can be analyzed by chromatography and electrophoresis. Electrophoresis is the method of separating molecules on the basis of their electric charges.The peptide bonds in the protein must first be hydrolyzed to release the individual amino acids.After a protein has been hydrolyzed, each amino acid in the mixture produced has a different isoelectric point.Meaning, they can be separated using electrophoresis.Separation can occur using paper, or other solid supports. The solid support is saturated with a buffer solution of a known pH.Amino acids with positive charges move to the cathode and amino acids with negative charges move to the anode.The sample consisting of a mixture is applied to the center of the paper; the electrodes and ends of the paper are placed in the buffered solution and a high electrical potential is applied to the electrodes. After separation occurs, the paper strip is dried and the paper can be compared with known samples to determine what amino acids are present.
Chromatography is a useful method for the separation of mixtures of substances which are otherwise not readily separated.Paper chromatography is best for identifying components of a very small sample of mixture. It’s particularly suitable for separating hydrophilic substances such as amino acids.The solubility of different amino acids varies in the stationary phase (water) and the mobile phase (solvent).Amino acids with greater solubility in the solvent will travel further in the direction of the solvent flow.The components of the mixture move with the solvent at different rates depending on their solubility in the stationary and moving phases.
Amino acid residue composition can be determined by hydrolyzing the peptide bonds with chromatography or electrophoresis.
B.2.6 List the major functions of proteins in the body. Proteins carry out important functions in the body such as proving structure, acting as enzymes, hormones, immunoproteins, and transportation energy, as well as acting as an energy source.
STRUCTURAL: Collagen and keratin provide structure and strength.
BIOLOGICAL CATALYSTS: Enzymes catalyze almost every reaction in the body, and without them the reactions would occur too slowly.They also provide an alternate pathway for the reaction, which lowers the activation energy and speeds up the reaction.
HORMONES: Important proteins in humans and animals (ex. Insulin)
ANTIBODIES: Produced as a result of the presence of foreign materials in the body, which provide immunity for diseases.Also provide protection against viral infection.
TRANSPORT: Hemoglobin in the red blood cells carries oxygen from the lungs to the cells. ENERGY: Proteins can be used to provide energy when supplies of carbohydrates and fats are insufficient (ex. During starvation)
Carbohydrates have the empirical formula CH2O, and are the main energy source for our bodies and are vital to the synthesis of cells.They serve as food sources for living organisms and provide structural support for plants.Important carbohydrates are: starch, lactose, sucrose, glucose, and fructose.Most carbohydrates are changed to glucose, as a result of digestion, then carried by the blood to body cells where it gets oxidized. The available energy goes to physical activities, keeps the body warm, and is used for repair and growth of cells.Excess carbohydrates are converter to fats and stored in the body.
Cellulose is the major component of plant cells.
B.3.1 Describe the structural features of monosaccharides. B.3.2 Draw the straight-chain and ring structural formulas of glucose and fructose. B.3.3 Describe the condensation of monosaccharides to form dissacharides and polysaccharides. B.3.4 List the major functions of carbohydrates in the human body. B.3.5 Compare the structural properties of starch and cellulose and explain why humans can digest starch but not cellulose. B.3.6 State what is meant by the term dietary fiber. B.3.7 Describe the importance of a diet high in dietary fiber. Monosaccharides, literally meaning “one sugar”, are the smallest molecular units of carbohydrates with the formula (CH2O)nEx. Glucose, galactose, and fructoseThey are aldehydes or ketones containing a carbonyl (C=O) group and at least two hydroxyl (-OH) groups.They have low molar masses, are sweet and readily soluble in water due to hydrogen bonding between water and the –OH groups.They form crystalline solids, due to intramolecular hydrogen bonding between the –OH groups.
The carbon atoms in glucose are numbered, starting with 1 at the carbonyl group. There are four similar chiral (asymmetrical) carbon atoms.Glucose is found almost always in a ring or cyclic structure in aqueous solution.
When monosaccharides form dissacharides or when smaller polysaccharides form larger polysaccharides they do it through condensation reactions by getting rid of a water molecule. This is called the glycosidic linkage.
Energy source: potatoes, corn, rice, bread, and fruits contin carbohydrates.Energy reserve: animals use glycogen stored in the liver as their energy storage polysaccaride.It can be broken down by enzymes into glucose which can be transported by the blood to cells.Precursor of other biologically important molecules: Heparin, which occurs in intestinal walls and is used as an anticoagulant, is formed from carbohydrates.Carbohydrates are also found as components of nucleic acids.
Starch and cellulose are polymers of glucose units.
Starch exists in two forms: amylose (a-1,4 linkage), and amylopectin (a-1,4 and a-1,6 linkages).
Cellulose contains only B-1,4 linkages, which can be hydrolyzed to glucose by the enzyme cellulase, which does not exist in most animals, including mammals, so we cannot digest it.
Dietary fiber is mainly plant material that is part of fruits, grains and vegetables that the human body cannot digest because it is not hydrolyzed by enzymes within the digestive tract.
Examples include cellulose, hemicellulose, lignin, and pectin.
There are two types of dietary fiber:
1-Water insoluble fiber, cellulose and lignin, are mainly present in whole grain foods. They absorb water, providing bulk and moving food through the digestive system.
2-Water soluble fiber includes pectins, which undergo fermentation in the large intestine by bacteria to produce short chain fatty acids. They have positive health effects such as stabilizing lipid and blood glucose levels, providing immune protection through stimulating the production of antibodies, and preventing the following conditions:
A. Constipation and Diverticulosis
B. Irritable Bowel Syndrome
D. Crohn’s Disease
B.4.1 Compare the composition of the three types of lipids found in the human body B.4.2 Outline the difference between HDL and LDL cholesterol and outline its importance B.4.3 Describe between the difference in structure between saturated and unsaturated fats B.4.4 Compare the structures of the two essential fatty acids linoleic (omega-6 fatty acid) and linoleic (omega-3 fatty acid) and state their importance B.4.5 Define the term iodine number and calculate the number of C=C double bonds in an unsaturated fat/oil using addition reactions B.4.6 Describe the condensation of glycerol and three fatty acid molecules to make a fat B.4.7 Describe the enzyme-catalysed hydrolysis of fats during digestion B.4.8 Explain the higher energy value of fats as compared to carbohydrates B.4.9 Describe the important roles of lipids in the body and the negative effects that they can have on health B.5.1 Outline the difference between micronutrients and macronutrients B.5.2 Compare the structures of retinol (vitamin A), calciferol (vitamin D) and absorbic acid (vitamin C). B.5.3 Deduce whether a vitamin is water or fat soluble from its structure B.5.4 Discuss the causes and effects of nutrient deficiencies in different countries an suggest solutions B.6.1 outline the production an functions of hormones in the body B.6.2 Compare the structures of cholesterol and the sex hormones B.6.3 Describe the mode of action of oral contraceptives B.6.4 Outline the use and abuse of steroids Changes the release of hormones (FSH/LH)
Prevents ovulation/egg release
Prevents the attachment of eggs to the uterus
Prevents the sperm from reaching the egg Hormones are chemical messengers that are secreted by endocrine glands and are controlled by the pituitary gland. (Controlled by the hypothalamus) Adrenaline - Circulation
Thyroxine - Growth
Insulin - Regulates glucose intake
-LH, FSH, Progestorone, Estrogen
Steroids serve as effective ways to increase muscle mass.
-cancer recovery The abuse of steroids can lead to many negative side-affects:
-Emotional swings Nutrients in food play specific roles in the metabolism of the human body. Vitamins, for example, are organic compounds required for metabolism. They function as coenzymes to act as catalysts for reactions throughout the body. Micronutrients: Substances required in small dosages to act as co-factor to enzymes. They are essential for proper body function. They do not produce energy adn must be taken in by diet. Macronutrients: Chemical substances that are required in large amounts in order to provide energy to the body required for growth and maintenance. ex/proteins, fats, carbs, minerals, etc. Vitamin A - required for the production of rhodopsin (light-sensitive material in the rods of the retina). Deficiency can cause night blindness and xerophthalmia.
Vitamin D - required for the uptake of calcium from food. Deficiency can cause weak bones (rickets).
Vitamin C - essential in the production of collagen : the protein of connective tissue. Deficiency can cause scrobutus (scurvy). Vitamins such as A,D,E and K contain long hydrocarbon groups which make them more fat-soluble in organic non-polar or polar solvents. Vitamins B and C are not storable and must be consumed everyday as the dissolve in water. They contain highyl responsive OH groups which hydrogen bond with water. Iron deficiency - Anemia
Iodine deficiency - Goitre
Vitamin A deficiency - night blindness
Vitamin D deficiency - rickets Lipids, otherwise known as fats, are substances found in living organisms that are defined in terms of their solubility. They are soluble in organic solvents which are non-polar or of low polarity. Lipids can be divided into three groups:
Triglycerides- fats an oils
Phospholipids - complex lipids containing phosphorous
Steroids - cholesterol Lipoprotein - contain different proportions of lipids and proteins and trasport cholesterol throughout the body. HDL - higher density lipoproteins carrying a ratio of 40-55% protein and 45-60% fat. More is good.
LDL - lower density lipoproteins carrying a ratio of
20-25% protein and 75-80% fat. More is bad. EFAs provide energy during lipid oxidation and promote good health, maintain healthy cholesterol levels, maintain good circulation, and support a healthy immune system. :D
An EFA deficiency can lead to lethargy, irritability, dry skin, reduced brain function, etc. FAT ADDITION REACTION: -The extent of unsaturation of a fat--tested by I2. By calculating the number of moles that react with a fat, the number of double bonds will be discovered. This is because the double bonds between C atoms are broken, and I bonds itself to the C. One I will bond to each former double-bond location--every molecule of I2 used indicates one double bond. Electrophillic addition:
R-C=C-R + I2 ---> R-I-C-C-I-R -When the reaction occurs, the iodine will become clear. The number of C=C bonds can be determined from the number of moles of I2 which add to one mole of fat. Fats and oils are triglycerides that are formed by condensation reactions of propane-1,2,3-triol (glycerol) and fatty acids (long-chain carboxylic acids). The fatty acid chains can be classified as saturated or unsaturated
Triglycerides are the most common lipids found in living organisms Triglyceride Phospholipid Steroids Phospholipids are similar in structure to triglycerides BUT one of the fatty acid groups is replaced with a phosphate group, and are hence known as diglycerides. The phosphate group is ionized and negatively charged, therefore water molecules are attracted to this polar part of the molecule, this end is then hydrophilic and soluble in water. Steroids do NOT contain fatty acids but are still considered to be lipids, this is because they have similar properties to triglycerides and are synthesized using common intermediates. Steroids all contain a 17-carbon atom skeletonthat varies due to the functional groups and their oxidation states. Found in both plants and animals
Form bile acids that help to emulsify and solubilize lipids during the digestion process. Glycerol itself has three hydroxyl groups, all of which are able to undergo a condensation reaction with a fatty acid molecule to form an ester. Through dehydration synthesis three water molecules are given off. Fats and oils are efficient long-term stores of chemical energy. Typical fats and oils provide about 38 kJ/g of energy while typical carbohydrates provide only 17 kJ/g. This is due to the composition of lipids which contain a higher proportion by mass of hydrogen and carbon than sugar. Hydrolysis is basically the opposite of condensation (esterification). Covalent bonds are split by a reaction by water and the fats are split into carboxylic acids adn glycerol. Pros:
Insulation and protection of organs
Increased risk of heart disease
HUMAN BIOCHEMISTRY Iodine number: the mass of iodine in grams that is consumed by 100 grams of a chemical substance.