Monomers and polymers, Carbohydrates and Lipids

describe the chemical reactions involved in converting monomers into polymers (2)

a condensation reaction joins monomers together and forms a chemical bond and releases water

describe the chemical reactions involved in converting polymers to monomers (2)

a hydrolysis reaction occurs to break the chemical bond between monomers and uses water

what is a monomer (1)

a smaller unit from which larger polymers are made

describe a biolchemical test to show that there is non-reducing sugars in a sample (3)

• heat the sample with acid and neutralise

• heat again with benedicts solution

• red percipitate for positive test

why would the use of a colorimeter improve the repeatibility of a student’s results (1)

standardises the method

how do you calculate total percentage error (1)

(percentage error A / vol of A) + (percentage error of B / vol of B ) x 100

describe the differences between the structure of a cellulose molecule and a glycogen molecule (4)

• cellulose only contains 1-4 glycosidic bonds whereas glycogen contains both 1-4 and 1-6 glycosidic bonds

• cellulose is made up of beta glucose whereas glycogen is made up of alpha glucose

• cellulose molecule has a straight chain whereas glycogen is branched

• cellulose molecule has a straight chain whereas glycogen is coiled

describe and explain features of starch that make it a good storage molecule (4)

• insoluble in water so it does not affect the water potential

• coiled therefore the molecule is compact and many can fit in a small area

• branched so has fast breakdown and enzyme action

• large molecule so it cant cross the cell membrane

what test is used to show the presence of starch (1)

iodine test

common monomers of glucose and what they are made of (3)

• maltose - glucose + glucose

• lactose - glucose + galctose

• sucrose - glucose + fructose

what type of bond joins together the glucose monomers (1)

glycosidic bond

explain how cellulose molecules structures are adapted for their function in plant cells (3)

• have long and straight chains

• these chains become linked together by many hydrogen bonds to form fibrils

• that provide strength in the cell wall

what is the general structure of a fatty acid (1)

RCOOH

what is the group represented by COOH in a fatty acid called (1)

carboxyl group

describe the test for the presence of a lipid in a sample (2)

• add ethanol and then add water and mix

• a milky emulsion shows a positive result

describe how a trigylceride is formed (3)

• 1 glycerol and 3 fatty acids

• condensation reaction occurs and removed 3 molecules of water

• an ester bond is formed

describe how an ester bond is formed in a phospholipid molecule (2)

• condensation reaction removes a water molecule

• between glycerol and fatty acid

what bond is formed in a triglyceride (1)

an ester bond

describe how you would test a piece of food for the presence of a lipid (2)

• dissolve in alcohol and then water

• milky emulsion shows a positive result

name 3 polysaccharides (3)

• starch

• glycogen

• cellulose

what are the roles of lipids (3)

• insulation

• waterproofing

• source of energy when oxidised

what is an alpha helix structure (1)

hydrogen bonds form every 4th peptide bond

what is a beta pleated sheet structure (1)

protein folds so two parts of polypeptide chain are parallel to each other enabling hydrogen bonds to form

what is a globular protein (1)

compact, roughly spherical protein which is soluble in water

what is a fibrous protein (1)

long strands of polypeptide chains with cross-linkages due to hydrogen bonds which is insoluble in water

what is the molecular structure of hemoglobin (7)

• 4 polypeptide chain

• globular protein therefore soluble in water

• hydrophilic R-groups face outwards

• maintains its 3D spherical shape

• hydrophobic R-groups face inwards

• maintains its solubility

• each subunit has a haem group which contains ironII

what is the function of hemoglobin (1)

binds to oxygen in the lung

what is the molecular structure of collagen (5)

• insoluble fibrous protein

• has 3 polypeptide chains

• these chains are held by hydrogen bonds

• helix shape

• in its primary structure, almost every 3rd amino acid is glycine

compare the structure of hemoglobin and collagen (6)

• collagen has 3 polypeptide chains whereas haemoglobin has 4

• collagen is long and thin whereas haemoglobin is spherical

• collagen is fibrous whereas haemoglobin is globular

• collagens amino acid chain is repetitive whereas haemoglobins is variable

• haemoglobin has a haem group and collagen does not

• collagen is insoluble in water whereas haemoglobin is soluble

compare the properties of a phospholipid and triglyceride (4)

• triglyceride consists of a glycerol molecule and 3 fatty acids whereas a phospholipid contains 2 fatty acids, one glycerol molecule, and a phosphate group

• phospholipids are amphipathic whereas triglycerides are non-polar

• phospholipids have a structural role in cell membranes whereas triglycerides provide long-term energy storage and insulation

• phospholipids are soluble in water whereas triglycerides are insoluble in water