Biological Molecules Flashcards
Which disaccharide is not a reducing sugar?
Sucrose
Which monomers make up lactose?
a-glucose and galactose
Which monomers make up maltose?
a-glucose and a-glucose
Which monomers make up sucrose?
a-glucose and fructose
What are the two polymers that make up starch?
Amylose and amylopectin
Which covalent bonds are present in carbohydrates?
Glycosidic bonds
Which covalent bonds are present in proteins?
Peptide bonds
Which covalent bonds are present in lipids?
Ester bonds
Which covalent bonds are present in nucleic acids?
Phosphodiester bonds
Which monomers makes up cellulose?
b-glucose
Which monomers makes up glycogen?
a-glucose
What physical features are found in amylose?
a-glucose, helix (coiled) shape and 1,4 glycosidic bonds
What physical features are found in amylopectin?
a-glucose, branched chain (every ~20 monomers) and 1,4 + 1,6 glycosidic bonds
What are the physical features found in glycogen?
a-glucose, branched (every ~10 monomers) and 1,4 + 1,6 glycosidic bonds
What is the main role of glycogen?
Mid-term energy storage in animals
What is the main role of starch?
Energy storage in plants
What is electronegativity?
Measuring an atom’s pull on a shared pair of electrons
What occurs due to oxygens high electronegativity in water?
Partial charges (oxygen is slightly negative, hydrogens are slightly positive), causing water to be polar
What is cohesion?
‘Stickiness’ between water molecules
What is adhesion?
‘Stickiness’ between water molecules and other polar molecules eg. Xylem wall
What does hydrophobic mean?
Not soluble in water (will not dissolve)
What does hydrophilic mean?
Soluble in water (will dissolve)
Why is water used as a transport medium?
It is a universal solvent and a metabolite
What does thermostable mean?
Temperature is not going to fluctuate much: buffers changes in temperature
Define large latent heat of vapourisation
Takes a large amount of thermal energy to evaporate
What is the reducing sugars test?
Add Benedict’s solution and heat in water bath, if positive colour changes from blue to red
What is the non-reducing sugars test?
Negative result for reducing sugars test, add HCl to solution and boil, then add sodium hydrogen carbonate to neutralise and repeat reducing sugars test
What is the test for starch?
Add iodine solution, if positive colour changes from yellow to blue/black
What is the test for proteins?
Add Biuret’s reagent, if positive colour changes from blue to purple
What are the two main types of lipids?
Triglycerides and phospholipids
Are lipids soluble in water?
No as they are hydrophobic - they are only soluble in other organic solvents eg. Alcohols
What are the components of triglycerides?
1 glycerol and 3 fatty acid chains
What are saturated fatty acids?
Straight chains with only single c-c bonds
What are unsaturated fatty acids?
Bent chains with single c-c bonds and double c=c bonds
Which fatty acid type has high melting and boiling points?
Saturated fatty acids as they fit closer together in a regular pattern and form stronger associations between the molecules, so they have higher melting and boiling points
What is formed in the condensation reaction of 1 glycerol and 3 fatty acids?
Produces 1 triglyceride, 3 water molecules are released and 3 ester bonds are formed
What physical part has a phospholipid got that a triglyceride doesn’t?
A phosphate molecule on the glycerol (but therefore only 2 fatty acid chains)
Describe the charge of phospholipids
The phosphate group on the molecule is charged so therefore is hydrophilic (head) and the fatty acid chains are uncharged and are therefore hydrophobic (tails)
Where are phospholipids found?
Plasma membranes in a ‘phospholipid bilayer’ due to their bipolar nature
What is the test for lipids?
Mix the sample being tested with alcohol, shake the tube thoroughly, add cold water and shake gently, if positive then a milky-white emulsion is formed
What is the monomer found in proteins?
Amino acids
What is the polymer for a protein called?
Polypeptide chain
What are the 4 types of amino acids?
Hydrophilic, charged/ionic, hydrophobic and thiol (sulphur)
What is a dipeptide?
2 amino acids joined by a peptide bond
What is the primary structure of proteins?
Sequence of amino acids in the polypeptide chain
What is the secondary structure of proteins?
Weak hydrogen bonds are formed between the slightly positive N-H group and the slightly negative C=O group of another amino acid. This forms either an alpha helix (coil) or beta pleated sheets
What is the tertiary structure of proteins?
Further folding of polypeptide chain to give very specific 3D structure. Types of bonding that could be formed are hydrogen bonds, hydrophobic interactions, disulphide bridges and ionic bonds
What is the quaternary structure of proteins?
Same bonding types as in tertiary, but between more than one polypeptide chain and/or non-protein ‘prosthetic’ groups
What are the two types of proteins?
Globular and fibrous
Describe the characteristics of globular proteins
They are hydrophilic, they are spherical and have a compact structure, used in metabolic processes eg. Enzymes and haemoglobin
Describe characteristics of fibrous proteins
Fibre like - long chains which run parallel to each other, linked by many cross-bridges so are very strong and stable eg. Collagen
How many polypeptide chains does haemoglobin have?
4
How many polypeptide chains does collagen have?
3
What are enzymes?
Globular proteins that act as biological catalysts
What are catalysts?
Substances that increase the rate of a chemical reaction and are not used up
What are anabolic reactions?
‘Building’ reactions using energy
What are catabolic reactions?
‘Breaking down’ reactions that release energy
What is an enzyme-substrate complex?
Complex formed when a substrate bunds to the active site of an enzyme
What does sucrase do?
Catalyses the hydrolysis of sucrose
What does sucrose synthase do?
Catalyses condensation of sucrose
What biological molecule are enzymes?
Globular proteins
Why are enzymes very specific to one reaction?
The binding of the substrate to the active site of the enzyme is very specific - substrate must be complimentary to active site
What is the induced fit model?
As the complimentary substrate binds to the active site, the active site changes shape slightly to better fit the substrate. The ES complex that is formed puts strain/stress on the bonds causing bonds to break/make + form products. When products leave the active site it returns to its original shape
How do enzymes speed up the rate of reactions?
They lower the activation energy (Ea)
What is activation energy?
Minimum energy required to get a reaction going
What factors affect enzyme activity?
Temperature, pH, enzyme concentration + substrate concentration
What are enzyme inhibitors?
Substances that directly/indirectly affect the functioning of the active site of a specific enzyme therefore preventing substrate binding, so no ES complex formed and therefore decreases the rate of reaction
What are competitive inhibitors?
Similar shape/structure to substrate so can also bind to active site, so substrate competes with inhibitor for the active site. Not permanent
What are non-competitive inhibitors?
Binds to allosteric site of enzyme, which causes change in tertiary structure of enzyme, therefore changing shape of active site and it is no longer complementary to substrate. May be permanent
