Biology - Biological molecules

What is a monomer?

Smaller molecule of which larger molecules are made up of

What is a polymer?

Molecule made of lots of repeating units joined together

What is a condensation reaction

When 2 monomers join together and form a covalent bond with the elimination of a water molecule

What is a hydrolysis reaction

Breaking the covalent bond between monomers with the addition of a water molecule

What is an isomer

Compounds with the same chemical formula but different structural arrangements

What is a disaccharide

Two monosaccharide join via a condensation reaction and form a glycosidic bond

State the structure, properties and uses of starch

• alpha glucose

• Amylopectin → 1-4 and 1-6 glycosidic bonds, long branched chains which increase the SA so it can hydrolyse glycosidic bonds

• Amylose → 1-4 glycosidic bonds, long unbranched chains. Has coils so it can hold more in small space

• Uses → excess glucose store (plants), insoluble so doesnt affect water potential, energy store

State structure, properties and uses of glycogen

• alpha glucose

• 1-6 glycosidic bonds, long branched chains which increase the SA so it can hydrolyse glycosidic bonds

• Uses → excess glucose store, energy store, insoluble

State structure, properties and uses of cellulose

• beta glucose

• long unbranched chains, 1-4 glycosidic bonds.

• cellulose chains linked together by hydrogen bonds between glucose molecules make microfibrils

• microfibrils are strong and flexible bc of hydrogen bonds between cellulose

• Uses → supports cell walls

What is the test for sugars ?

• Reducing → Benedicts solution

• Add benedicts solution to sample, then heat in water bath above 80°

• Blue → green, orange, yellow, brick-red

• Non-reducing → Add dilute HCl then heat in waterbath to break bonds, then add alkali to neutralise

• Add benedicts solution, then heat in water bath above 80°

• Blue → green, orange, yellow, brick-red

What is the test for starch ?

• Iodine

• Browny-orange to blue-black

What are the roles of lipids ?

• energy source

• waterproofing

• protects organs

• forms hormones and membranes

• insulates organisms & myelin

How is triglyceride function linked to its structure ?

• high C-H bonds → good energy source

• insoluble → doesn’t affect water potential

• low mass → more energy stored in small vol.

State structure of a phospholipid

• One glycerol molecule, one phosphate group, two fatty acid chains joined together by ester bonds

• Phosphate head is hydrophilic and points outwards - towards water

• Fatty acid tails are hydrophobic and face inwards - away from water

• forms phospholipid bilayer

State structure of a triglyceride

• glycerol and three fatty acid chains joined via ester bonds

• non-polar, fatty acid tails are hydrophobic so its insoluble

• uses: energy store

Difference between saturated and unsaturated fatty acids?

Saturated → no double C-C bonds, maximum amount of hydrogen atoms

Unsaturated → one double C-C bond, fewer hydrogen atoms and double C-C bond causes bend

What is the test for lipids ?

• Add ethanol and then water and shake

• Milky white emulsion forms

What is a dipeptide

Two amino acids join via condensation reaction, forming a peptide bond between their carboxyl and amine groups

What is the primary structure

• sequence of amino acids in polypeptide chain

• determines the shape and function

What is the secondary structure

• alpha helix or beta pleated sheets

What is the tertiary structure

• 3d shape of the polypeptide chain

• maintained by weak hydrogen bonds, ionic bonds and strong disulfide bridges

What is the quaternary structure ?

• multiple polypeptide chains joined together

What is the test for proteins ?

• Add Biuret test and shake

• Turns from blue to lilac

What is an enzyme?

• biological catalyst that speeds up reactions by lowering activation energy

• has specific active site so can only bind to specific substrate

• can form enzyme-substrate complexes because its active site is complementary

What is the Lock and Key Model ?

States that the enzyme active site is exactly complementary to the substrate and the substrate fits exactly when forming an ES complex

What is the Induced-fit Model?

States that the enzyme’s active site is not exactly complementary to the substrate and changes shape in order to form an ES complex

What are the factors affecting enzyme action ?

• enzyme concentration

• substrate concentration

• temperature and pH

How does enzyme concentration affect enzyme action

• more active sites for substrate to bind to so more ES complexes form

• substrate concentration becomes limiting factor

How does substrate concentration affect enzyme action

• more frequent collisions so more ES complexes form

• enzyme concentration becomes limiting factor

How does temperature affect enzyme action

• kinetic energy increases so more frequent collisions and more ES complexes form

• at extreme temps, enzyme denatures and bonds that maintain tertiary structure break so ES complexes can form

How does pH affect enzyme action

• at extreme pH’s, the enzyme denatures and no ES complexes can be formed as the active site changes shape

What is a competitive inhibitor

• similar shape to the substrate

• binds to active site and blocks substrate from binding so no ES complexes are formed

What is a non competitive inhibitor

• binds to the enzyme’s allosteric site which changes the shape of the active site so no ES complexes can form