Chapter 2: Biological Molecules Flashcards
What are biological molecules?
They are organic substances found in living organisms. including reducing sugars, non-reducing sugars, starch, proteins and lipids.
Hows are biological molecules identified?
Using chemical tests.
What is starch?
Is what is produced when many glucose molecules bond by glycosidic bonds.
What are proteins?
Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues.
explain how the 4 main biologicala molecules can be formed from the simple monomers.
- Monosaccharides link up to form polysaccharides,
- Monosaccharides make nucleotides, which can link up with organic bases to form nucleic acids.
- Amino acids link up to form proteins.
- Fatty Acids and glycerol can link up to mak lipids.
What are macromolecules?
they are laWhatrge bioloigcal molecules such as a protein, polysaccharide or a nucleic acid.
What are Polymers?
They are giant molecules made from many similar repeating subunits joined together in a chain; They are also sometimes referred to as macromolecules.
What are Monomers?
they are relatively simpler molecules which is used as a basic building block for the synthesis of a polymer; many monomers are joined together to make the polymer, usually by condensation reactions; common examples of molecules used as monomers are monosaccharides.
What is a Nucleotide?
A molecule consisting of a nitrogen containing base,a pentose sugar and a phosphate group.
What are carbohydrates?
They are macromolecules consisting of carbon, hydrogen and oxygen. Cx(H2O)y where water: carbon in the ratio 2:1 and therefore is a hydrate.
what are the three main groups of carbohydrates?
Monosaccharides, Disaccharides and Polysacchraides. the sacchride means sugar or swett sbstance.
What is a monosaccharide?
Is a colecule consisting of a single sugar unit with the general formula (CH2O)n
What are the main groups of monosaccharides? Give common examples.
- Trioses (3C)
- Pentoses (5C) e.g. Ribose and Deoxyribose.
- Hexoses (6C) e.g Glucose, Fructose, Galactose.
describe the ring structured nature of glucose.
The presensce of a longer chain of carbon allows the chain to close up on it self, where C1 and C5 joinup together with Oxygen and the C6 does not participate,.
The fact that the OH can easily switch sides allows there to be an α-glucose and a ß-glucose.
what are the roles of monosaccharides in living organisms?
- They can act as an energy source due to their high abundance of C-H bonds which can be broken down to release energy to make ATP using ADP and a phosphate.
- They are used as building blocks for the creation of much larger molecules like glucose, pentose or ribose. the latter can go on to make RNA and DNA.
What is a disaccharide?
Is a sugar molecule consisting of two monosaccharides joined together by a glycosidic bond.
What are the monsaccharide consitituents of the disaccharide, maltose, fructose and galactose?
- Maltose: Glucose + glucose
- Sucrose: Glucose + Fructose
- Lactose: Glucose + Galactose
What is a Glycosidic bond?
it is a C-O-C link between two monsccharide molecules formed by a condensation reaction.
What is the role of enzymes in condensation reactions.
The enzyme decides which -OH bond will participate in the formation of a glycosidic bond, which allows for the creation of a variety of molecules.
What is Hydrolysis?
It is a reaction in which a complex molecule is broken down to simpler ones involving the addition of water.
What are reducing sugars?
They are the sugars that can carry out reduction where they become oxidised. They include all monosaccharides and some disaccharide like maltose.
What is benedict’s reagent?
It is copper(II) sulfate in an alkaline solution with a distinctive blue colour.
What is the chemical formula for benedict’s test?
reducing sugar + Cu2 (blue) -> oxidised sugar + Cu2+ (red brown)
Why is excess reagent used in benedict’s test?
To ensure that all sugar has reacted.
How can we determine the concentration of sugar using a benedict’s test?
- Using colour standards and comparing it OR
2. Use a colourimeter to measure the colour accurately.
How is benedict’s test used in the test for a non reducing sugar?
- The sample is tested with benedicts test, looking for any reducing sugars.
- Then to another sample, it is hydrolysied using HCl and then neutralized with NaOH. this gives the constituent monosaccharides
- Benedicts test is repeated. positive results mean that the sugar were non reducing. a heavier result means that both types were present. should there not be any positive results, then there is no sugars in the sample whatsoever.
What is a polysaccharide?
It is apolymer whose subunits are monsaccharides joined together by glycosidic bonds. e.g. starch, glycogen and cellulose. e.g. Starch, glycogen and cellulose.
explain the storgae of glucose in animal and plants.
glucose is stored as starch in plants and as glycogen in animals because it is too reactive on its own and is likely to disrupt osmosis if left dissolved in a soltion.
What is amylose?
It is a polymer of α-glucose linked by 1,4 linkages forming a curving chain; aylose is a constituent of starch. It is formed by condensation reactions and forms a compact, helical structure.
What is amylopectin?
A polymer of α-glucose monomers linked by 1,4 and 1,6 linkages forming a branched chain; amylopectin is a constituent of starch.
What is the function of amylose and a in mylopectin?
They form grains which are used as storage chloroplasts, storage organs, legumes etc. these grains can be made visible by simply staining it with iodne solution and viewing it with a microscope.
What is glycogen?
It is a polysaccharide made of many glucose molecules linked together; that acts as a glucose store in liver and muscle cells by clumping up and forms granules.
Why does the iodine test work for starches?
Starch molecules form large spirals that have holes, through which an iodine molecule can fit through easily. this then forms a complex that produces a very distinctive blue-black colour.
How do you carry out the iodine test?
drop the iodine onto the starch.
What is cellulose?
It is an structually strong natural polymer used as the main structural component for plants.
Why is cellulose so strong?
it is made with ß-glucose molecules whic have to be successively rotated 180°. This forms hydrogen bonds, composed of small charges. this although weak,together with many bonds makes strong microfibrils which can then go on to make a very strong fibre that run in different directions, cross-linked with other molecules to further increase strength.
What is a hydrogen bond?
It is a relatively weak bond formed by the attraction between a group with a small positive charge on a hydrogen atom and another group carrying a small negative charge.
how does the cell wall give a plant structural support?
cellulose has extremely high tensile strength. which means that it does not stretch very much and therefore it gives the cell turger pressure which can make a cell rigid during osmosis. this gives structural support.
