Biological Molecules Past Paper PDF

by CELL :01110983031 002011109830315 [email protected]  1. List the chemical elements that make up: – carbohydrate – fats – proteins 2. State that large molecules are made from smaller molecules, limited to: starch and glycogen from glucose – cellul...

by CELL :01110983031 002011109830315 [email protected]  1. List the chemical elements that make up: – carbohydrate – fats – proteins 2. State that large molecules are made from smaller molecules, limited to: starch and glycogen from glucose – cellulose from glucose – proteins from amino acid – fats and oils from fatty acids and glycerol 3. Describe the use of: – iodine solution to test for starch – Benedict’s solution to test for reducing Sugars – biuret test for proteins – ethanol emulsion test for fats and oils – DCPIP test for vitamin C 4. Explain that different sequences of amino acids give different shapes to protein molecules 5. Relate the shape and structure of protein molecules to their function, limited to the active site of enzymes and the binding site of antibodies 6. State that water is important as a solvent Supplement 7. Describe the structure of DNA as: two strands coiled together to form a double Helix each strand contains chemicals called bases cross-links between the strands are formed by pairs of bases the bases always pair up in the same way A with T, and C with G (full names are not required) 8. Describe the roles of water as a solvent in organisms with respect to digestion, excretion and transport. CELL :01110983031 002011109830315 [email protected]  Biological molecules Nutrition and Nutrients Importance of food: 1. For growth 2. For tissue repair 3. For production of energy 4. For protection against diseases Classes of food 1. Proteins 2. Fats or lipids 3. Carbohydrates or Saccharides 4. Vitamins 5. Minerals 6. Roughages 7. Water CELL :01110983031 002011109830315 [email protected]  Importance of Carbohydrates 1. Production of energy by the process of respiration 2. Stored in the cells - In plant cells it is stored in the form of starch - In animal cells it is stored in the form of glycogen 3. Cellulose is used in formation of cell walls of plant cells Storage of Carbohydrates Carbohydrates are stored in the form of polysaccharides because this insoluble form has no osmotic effect In mammals Excess carbohydrates are stored in liver and muscles in the form of glycogen Excess carbohydrates are also converted into fats to be stored under the skin and around certain organs such as kidney. CELL :01110983031 002011109830315 [email protected]  CLASSIFICATION OF CARBOHYDRATES NAME EXAMPLE SOURCE FORMULA PROPERTIES MONOSACCHARIDES Glucose, Grapes, C6H12O6  Are the basic units of fructose, fruits carbohydrates galactose  Are called simple sugars  Are soluble in water  Have sweet taste DISACCHARIDES Maltose, Barley, C12H22O11  Each molecule can be lactose, milk, decomposed into two sucrose sugar, molecules of sugarcane monosaccharides  Soluble in water  Sweeter than  Monosaccharides Can be found in the form of crystals or white powder POLYSACCARIDES Starch, Potatoes, (C12H22O11)n  Each molecule can be cellulose, vegetables, decomposed into many glycogen liver molecules of mono and disaccharides  Insoluble in water  No sweet taste  Only starch is a white powder CELL :01110983031 002011109830315 [email protected]  practice 1. 2. PROTEINS Made UP of long chain of subunits called Amino acids. which are joined together in a particular sequence coded by genes. elements (C,H,O,N) (there are 20 different types of amino acids). Sources of proteins Animal sources: meat, milk, fish and eggs. Plant sources: leguminous plants such as beans and lentils CELL :01110983031 002011109830315 [email protected]  Importance of proteins 1. As a source of energy. 2. Growth and tissue repair. 3. Formation of enzymes and hormones. 4. Protection against diseases as white blood cells and antibodies are made of proteins. 5. building the cell membrane. Properties of proteins 1. Amino acids are water soluble. 2. Some proteins are water soluble (ex: haemoglobin). 3. Other proteins are water insoluble (ex: keratin in hairs & finger nails) 4. In humans Excess amino acids are deaminated in liver and excreted as urea. Fats or Lipids Chemical Structure - are composed of three elements carbon, hydrogen and oxygen. The basic units, fatty acids and glycerol. Lipids are fats and oil - fat is a lipid solid at room temperature. - oil is a liquid which is liquid at room temperature. CELL :01110983031 002011109830315 [email protected]  Importance of fats 1. source of energy in respiration. (The energy produced by fats is nearly double that produces by carbohydrates about 39 kl/gram) 2. Form a part of the cell membrane (cholesterol) 3. Stored in the body As a food reserve 4.Protection to protect and support certain organs such as kidneys. 5. Insulation (Thermal insulation ) to act as an insulating layer that reduces the rate of heat loss. (electrical insulation) in the nerve cells. 6. Form a water proof layer for skin, fur and feathers. Notice Explain Carbohydrates are the best source of energy for players and not fats although the energy produces by fats is more than that produces by carbohydrates because the metabolism of fats takes a longer time. CELL :01110983031 002011109830315 [email protected]  Food test Food type Procedure Result Positive Negative Starch Add Iodine solution Blue black or The colour (has a yellow brown dark blue remains yellow colour) colour brown Glucose add Benedict s solution Orange red or Remains blue (blue colour) brick red (Reducing and heat. precipitate is sugar) Precautions: formed. 1. Hold the tube with a holder. (the gradual 2. Direct the opening of change in the tube away from your colour from face blue to red 3. Do not fill more than according to the half of the tube to avoid concentration splashes when the of the sugar) solutions boils. 4.It is preferable to use a water bath. CELL :01110983031 002011109830315 [email protected]  proteins this test is known as Purple-mauve- blue biuret test) (blue) lilac this test is known as Cloudy Clear ethanol or emulsion test) FATS 1. Add ethanol, fats dissolve in ethanol forming clear solution. 2. - Add drops of water to the clear solution 4.DNA The chemical that make up our genes ,chromosomes which are responsible for controlling the cell activity and transfer the features from then parents to then offspring. CELL :01110983031 002011109830315 [email protected] 1. DNA is an amazing molecule. It carries a ‘code’, which instructs the cell which amino acids to link together, in which sequence, to make proteins. 2. The sequence of bases in the DNA molecule determines the sequence of the amino acids that are used to build a protein. Because proteins have so many different functions in organisms. DNA STRUCTURE 1. DNA is made of smaller molecules called nucleotides. Each nucleotide contains a base. There are four bases, A, C, G and T. 2. A DNA molecule contains two chains of nucleotides, coiled around one another This shape is called a double helix. The two chains or strands are held together by HYDROGEN bonds that form between the bases of opposite strands. 3. A always forms bonds with T, and C with G. This is called complementary base pairing. IMPORTANCE 1. controlling the cell activity 2. transfer the features from then parents to then offspring through the genes. GENE A sequence of bases (genetic information) that codes for a protein. CELL :01110983031 002011109830315 [email protected]  How the trait is formed 1. Each gene carries a series of code words for synthesis of proteins. 2. Each code word on DNA is made up of 3 bases 3 letters) in a certain sequence. 3. Each code word is called a triplet, which corresponds to a single amino acid In a protein. CELL :01110983031 002011109830315 [email protected]  Different types of food molecules VITAMINS Source Importance Deficiency 1. Vitamin C Citrus fruit, Helps in formation of Scurvy tomatoes& protein collagen in symptoms vegetables skin, bones & blood 1. Pain in joints vessels thus: and muscles 1-strengthen blood 2. Bleeding from vessels. gums and other 2- keep teeth and places. gum healthy. 3. Skin ulcers 3- protects cells from 4. Poor healing of aging by wounds keeping skin healthy. PROPERTIES OF VITAMIN C 1. Water Soluble vitamin therefore it cannot be stored in the body. 2. Spoils if food heated or canned. 3. Destroyed by being exposed to air e.g. if food is grated or minced as this activities enzymes in food which destroyed vitamin C. 4. Refrigeration keeps the vitamin c content of the food but to a certain limit TESTING THE PRESENCE OF VITAMIN C(DCPIP) 1. Vitamin C is not a carbohydrate, fat or protein. We can test for it using a blue solution called DCPIP. 2. DCPIP loses its colour when vitamin C is mixed with it. CELL :01110983031 002011109830315 [email protected] METHOD : 1. Put about 1 cm depth of DCPIP into a test tube. 2. Use a dropper pipette to add lemon juice to the DCPIP. 3. Lemon juice contains a lot of vitamin C, so this should make the DCPIP lose its colour( changed from blue to colourless). VITAMIN D Source Importance Deficiency 2. Vitamin D Butter, egg 1. Helps calcium and 1. Rickets in yolk, phosphorus to be children fish liver oil. absorbed for Bones become Sunlight. 2. making bones and soft, bent teeth. and deformed. 2. In adults Osteomalacia ( i.e fragile bones) PROPERTIES OF VITAMIN D Fat Soluble vitamin therefore it can be stored in the body (in liver) NOTICE 1. Sailors are liable to be infected by scurvy because they use stored or canned food. 2. It is important to expose children to sun rays to avoid rickets, because vitamin D can be formed in their bodies by the effect of the ultra violet rays of the sun. CELL :01110983031 002011109830315 [email protected]  6. MINERALS SOURCE IMPORTANCE DEFICIENCY IRON Red meat, Formation of 1. Anaemia (rapid spinach haemoglobin in tiredness and & liver Red blood shortness of breathing cells, which due to lack of carries haemoglobin oxygen, which is used to carry needed for oxygen to the different respiration, to parts of the body all body cells. 2. Pale skin 3. Shortness of breath. 4. Feeling tired. CALCIUM Milk, dairy For bones, 1. Weak bones & teeth.. products, teeth, blood 2. Poor clotting of blood. bread clotting 3. Uncontrolled muscle contractions(spams) 4. Rickets& osteomalacia 7. FIBERS SOURCE IMPORTANCE DEFICIENCY Fibres Cereals grains. Stimulate Constipation & Bread and peristalsis of the cancer vegetables intestine colon,as less to squeeze food fibers causes 1 along the gut less peristalsis. CELL :01110983031 002011109830315 [email protected]  8. IMPORTANCE OF WATER 1. It is the main component of the cytoplasm 2. Metabolic reactions 3. transporting of digested food. 4. dissolving gases for exchange. 5. Transporting of excretory products. 6. secreting sweat is necessary for regulating the body temperature. 7.Dissolving Enzymes and hormones. CELL :01110983031 002011109830315 [email protected]