2.2 Biological Molecules Flashcards
(38 cards)
How do hydrogen bonds form between water molecules?
Water is polar Forms O𝛿- (slightly negative) & H𝛿+ (slightly positive).
There are intermolecular forces of attraction between a on O𝛿- of one molecule & H𝛿+ on an adjacent molecule.
State 7 biologically important properties of water.
reaches maximum density at 4 degrees celcius
high surface tension
incompressible
solvent for chemical reactions
high specific heat capacity
high latent heat of vaporisation
cohesion between molecules
Why is the incompressible nature of water important for organisms?
Provides turgidity to plant cells.
Provides hydrostatic skeleton for some small animals
Explain why ice floats on water. Why is this important for organisms?
Ice is less dense than water because H-bonds hold molecules in fixed positions further away from each other.
Insulates water in arctic climates so aquatic organisms can survive
Why is the high surface tension of water important for organisms?
Slows water loss due to transpiration in plants.
Water rises in narrow tubes, lowering demand on root pressure.
Some insects can skim across the surface of water.
Why is water an important solvent for organisms?
Polar universal solvent dissolves
Why are the high specific heat capacity and latent of vapourisation of water important for organisms?
Cooling effect when water evaporates from skin surface as sweat/ from mouth when panting.
Define monomer and polymer. Give some examples.
monomer: smaller units that join together to form larger molecule
monosaccharides (glucose, fructose, galactose, ribose)
amino acids
nucleotides
polymer: molecules formed when many monomers join together
polysaccharides
proteins
DNA/ RNA
What happens in condensation and hydrolysis reactions?
Condensation: chemical bond forms between 2 molecules & a molecule of water is produced.
Hydrolysis: a water molecule is used to break a chemical bond between 2 molecules
Name the elements 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
Draw the structure of alpha-glucose and beta-glucose.
:)
Describe the properties of alpha glucose.
Small & water soluble
Draw the structure of ribose.
:)
What type of bond forms when monosaccharides react?
Glycosidic bonds and water are formed
Describe how disaccharides form.
Name 3 disaccharides.
Molecular formula
Condensation reaction forms glycosidic bond between 2 monosaccharides.
maltose: glucose + glucose
sucrose: glucose + fructose
lactose: glucose + galactose
all have molecular formula C12H22O11
Describe the structure and functions of starch.
Storage polymer of alpha glucose in plant cells:
insoluble
large
made from amylose:
1,4 alpha glycosidic bonds
helix
and amylopectin:
1,4 & 1,6 alpha glycosidic bonds
branched = many ends for hydrolysis into glucose
Describe the structure and functions of glycogen.
Store of alpha glucose
1,4 & 1,6 glycosidic bonds.
Branched = many ends for hydrolysis.
Insoluble
Compact.
Describe the structure and functions of cellulose.
Polymer of beta-glucose gives rigidity to plant cell walls
1,4 glycosidic bonds.
Straight-chain, unbranched molecule.
Alternate glucose molecules are rotated 180°.
H-bond crosslinks between parallel strands
How do triglyglcerides form?
Condensation reaction between 1 molecule of glycerol &
3 fatty acids
forms ester bonds.
Contrast saturated and unsaturated fatty acids.
Saturated:
contain only single bonds
straight-chain molecules
higher melting point = solid at room temp
Unsaturated:
contain C=C double bonds
kinked molecules
lower melting point = liquid at room temp
Relate the structure of triglycerides to their functions.
High energy:mass ratio = energy storage
Insoluble hydrocarbon chain = waterproof plants
Slow conductor of heat = thermal insulation
Less dense (floats) water = buoyancy of aquatic animals.
Describe the structure and function of phospholipids.
glycerol attached to 2 hydrophobic fatty acid tails & 1 hydrophilic polar
phosphate head.
Forms phospholipid bilayer in water = component of membranes.
Tails can splay outwards = waterproofing
Are phospholipids and triglycerides polymers?
No. They are macromolecules.
Describe the structure and function of cholesterol.
Steroid structure of 4 hydrocarbon rings. Hydrocarbon tail on one side, hydroxyl group (-OH) on the other side.
Adds stability to cell surface phospholipid bilayer by connecting molecules & reducing fluidity.
