2.2 Biological Molecules Flashcards
How do hydrogen bonds form between water molecules ?
Water is a polar molecule as oxygen and hydrogen have a sufficient difference in electronegativity
A slight charge forms on O and H, which allows intermolecular forces to form between molecules
State 7 biologically important properties of water
•Reaches maximum density at 4•C
•High surface tension
•Incompressible
•Solvent for chemical reactions
•High specific heat capacity
•High latent heat of vaporisation
•Cohesion between water molecules
Why is the incompressible property of water important for organisms ?
Provides turgidity for plants
Provides hydrostatic skeleton for some small organisms
Explain why ice floats on water and why this is important for organisms
Ice is less dense than water as Hydrogen bonds cause molecules to expand when becoming solid
This is important for life as it forms insulating ice caps at the poles and keeps the planets water at a suitable temperature
Why is the high surface tension of water important for organisms ?
It allows some organisms to live on the surface of water.
Why is water an important solvent for organisms ?
Allows the transport of molecules with a charge or dipole for inter and extra cellular purposes.
Why is the high specific heat capacity and latent heat of vaporisation of water important for organisms ?
SHC - Hydrogen bonding in water means that water temperature wont change drastically as kE will be used weakening H-bonds. This allows organisms to resist fluctuations in temperature
LH - High energy required to vaporise water. Allows organisms to sweat to lose heat energy from the body
Define monomer and polymer. Give examples of both
Monomers (such as monosaccharides, amino acids and nucleotides) are small repeating units which bond to form larger molecules
Polymers (such as polysaccharides, proteins and DNA) are formed when many monomers are bonded together
What happens in condensation and hydrolysis reactions ?
Condensation - a reaction which joins two biological monomers and gives H2O as a biproduct
Hydrolysis - a reaction in which a bond between two monomers is broken using water
Name the molecules found in carbohydrates, lipids, proteins and nucleic acids.
Carbohydrates/lipids : C, H, O
Proteins : C, H, O, N, S
Nucleic acids : C, H, O, N, P
Describe / draw the structure of α-glucose and β-glucose.
Both are hexose monosaccharides
Both have OH groups on all carbons but 5
Both have a methyl-OH group on C5
Both have an O between carbon 1 and 5, forming a ring
The only difference between the two molecules is that α-glucose has both hydroxyl groups on 1 and 4 pointing down and β-glucose has the C1 OH pointing up.
Describe the properties of α-glucose.
Small and easily soluble, allows for easy transportation in the blood
Complementary shape for antiport (swap) for co-transport for absorption in the gut
Complementary shape for enzymes for glycolysis
Describe / draw the structure of a ribose sugar.
A pentose monosaccharide with OH groups on all carbons except C4
A methyl-OH group is on C4
An oxygen is bonded between C1 and 4
What type of bond forms when monosaccharides react? What are the molecules called ?
The types of glycosidic bonds are α 1-4, α 1-6 and β 1-4
(α 1-2 exists only in sucrose)
Two monosaccharides bonded are a disaccharide, any more is a polysaccharide.
Name three disaccharides and describe their structure.
Maltose : glucose + glucose
Sucrose : glucose + fructose
Lactose : glucose + galactose
Describe the structure and functions of starch.
Starch is an energy store for plant cells made of α-glucose
It is insoluble so doesn’t affect Ψ and is large so doesn’t leave the cell
It is made from amylose and amylopectin
Amylose - 1-4 bonds in a helix shape. Compact with H bonds
Amylopectin - 1-4 and 1-6 in a branched shape. Many ends to hydrolyse and get glucose for ATP
