biological molecules Flashcards
what is meant by hydrogen bonding?
as the electrons in a molecule are not evenly distributed but spend more time in one position this region is more negatively charged than the rest of the molecule. when a weak electrostatic attraction is formed between teh positive end of one moleculae and the negative end of another a weak electrostatic bond is formed, this is called an hydrogen bond.
what is meant when a molecule is polarised?
it has a negative region and also a positive region.
what is polymerisation?
polymerisation is process in which polymers are formed. polymers are long chains of monomers, these are usually are based on carbon.
what is a condensation reaction?
in the formation of polymers from polymerisation a water molecule is produced each time a new sub-unit is attached
what is hydrolisation?
polymers can be broken down by the addition of water. they break the bonds in between the sub units, in polysaccharides these are called glycosidic bonds.
what is a molar solution?
a solution that contains one mole of solute in each liter of solution.
what is the basic monomer unit of carbohydrates?
a sugar unit. this is also known as a saccharide. a single monomer is therefor called a monosaccharide, two are a disaccharide, and more than two is a polysaccharide.
what is a monosaccharide?
a monosaccharide are soluble substances that have the general formula (CH2O)n where n can be any number from 3 to 7.
what is a reducing sugar?
a reducing sugar is a sugar that can donate electrons to another chemical
wha is the test for a reducing sugar?
the benedicts test. benedict’s is an alkaline solution of copper (II) sulphate. when a educing sugar is heated with benedicts it gives off an insoluble red precipitate of copper(I) oxide
what are the 3 examples of disaccharides?
glucose joins to glucose to form maltose.
glucose joins to fructose to form sucrose
glucose joins to galactose to form lactose
what is the bond between two monosaccharides called?
a glycodic bond
what is the test for non reducing sugars?
firstly carry out the test for non educing sugar. if the result is negative then add 2cm3 of the sample to 2cm3 of dilute HCL and then place the solution in a gently boiling water bath for 5 min. (the HCL will hydrolyse any disaccharide present). slow add some sodium hydrogen carbonate to neutralise the HCL. re test the resulting solution for reducing sugars.
what are polysaccharides?
polysaccharides are polymers, formed by combining together many monosaccharides molecules.
what is the test for starch?
place the sample being tested into a test tube add two drops of iodine solution and stir. if starch is present then the solution will go blue-back.
what is starch?
starch is a polysaccharide that is sound in many parts of a plant in forms of small grains. it forms a major component if food and is the major energy source in most diets.
why does starches structure make it great for energy storage?
it is insoluble and therefor doesn’t affect water potential s water is not drawn into the cell by osmosis
being large and insoluble, it does not defuse out of cells
it is compact, so a lot of it can be stored in a small space
when hydrolysed it forms alpha glucose, which is both easily transported and also readily used in respiration.
the branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released easily and very rapidly
what is glycogen?
glycogen is a polysaccharide that is found in animal and bacteria but never in plant cells. it is similar to starch but is shorter and is more highly branched. in animals it is mainly stored as granules in the muscles and the liver.
why does glycogens structure suit it for storage?
it is insoluble and their for does not tend to draw water in to the cell via osmosis
being, insoluble it does not diffuse out of cells
it is compact so a lot can be stored in a small space
it is more branched than starch so has more ends that can be acted on simultaneously by enzymes. it is therefor more rapidly broken down to form glucose monomers, which are used in reparation. important in animals which have a high metabolic rate.
what is cellulose?
cellulose unlike both starch and glycogen uses beta glucose instead of alpha, this produces fundamental differences in the structure and the function of this polysaccharide. cellulose does not have a coil structures inside it has straight unbranched chain. these run parrealel to each other allowing hydrogen bonds to form between them. while each inividua hydrogen bind adds very little to the strength of the molecule, the sheer overall number of the, makes a considerable contribution to strengthening the the cellulose
the cellulose molecules group to gather to form microfibrils which are arranged in parallel groups called fibres. cellulose provides rigidity to the cell. stops the cell bursting as water enters by osmosis (exerts an inward pressure)
why does the structure of cellulose make it suitable to its job?
cellulose molecules are made up of beta glucose and so form long straight, unbranched chains.
these cellulose molecular chains run parallel to each other and are cross linked by hydrogen bonds which add collective strength
these molecules are grouped together to form microfibrils which n turn are grouped to form fibres all of which provides yet more strength.
what are lipids?
lipids are a group of substances that share the following characteristics
they contain hydrogen, carbon, oxygen
the the proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates
they are insoluble in water
they are soluble in organic solvents
the main group of lipids are triglycerides and phospholipids.
what are the roles of lipids?
source of energy - when oxidised, lipids provide more than twice the same mass or carbohydrate and release valuable water
waterproofing - lipids are insoluble in water and therefore useful in water proofing
insulation - fats are slow conductors of heat and when stored beneath the body surface help to retain body fat. they also act as electrical insulators in the myelin sheath around nerve cells.
protection - fat is often stored around delicate organs, such as the kidney.
what are triglycerides?
a molecule that contains there fatty acids combine with a glycerol. each fatty acid forms an ester bind with the glycerol. as glyceride is alwase the same the variation in the molecule come from the fatty acids. there are over 70 different fatty acids
