Biological Molecules Revision Notes
Molecular Bonding
Elements
-different atoms are elements (periodic table)
-bond together to form molecules (C,H,O,N)
-some are used for important metabolic functions (Na, K, Cl)
Ions – where an atom has gained or lost an electron. Can be cations (positively charged) or anions (negatively charged)
Covalent Bond – a bond between atoms where electrons are shared
Condensation Reaction
-occurs when 2 molecules are joined together and a molecule of water is produced
-OH- from one molecule and H- from another for to make a water molecule (H2O)
Hydrolysis
-molecules are split apart by the addition of water
Polymerisation
-where lots of monomers are joined together to form a polymer
Hydrogen Bonding
-water is polar molecule and hydrogen bonding occurs
-as O is more electronegative, the electrons are closer so this causes the O to be δ-ve and the hydrogen to be δ+ve.
-the hydrogen δ+ve is attracted to δ-ve oxygen and hydrogen bonding occurs
-each water molecule can form 4 hydrogen bonds (1 on either H and 2 on the O)
Water
-it is a polar molecule because the O is slightly negatively charged and the H is slightly positively charged due to the distribution of the
electrons.
-the electrons spend most their time around the O and not H hence the polar charges.
Liquid:
-lots of hydrogen bonds are continuously made and broken in liquid state
Effect on Organisms: provide a habitat for aquatic life, major component of living tissues
High Specific Heat Capacity:
-lots of heat energy is required to break all of the many hydrogen bonds to change it state (lakes, oceans are around a constant temperature)
Effect on Organisms: need stable environment to live; conditions need to be stable for enzyme-controlled reactions to take place
High Latent Heat of Evaporation:
-requires a lot of energy to break all the bonds hence it has a high boiling point
Effect on Organisms: mammals are cooled when sweat evaporates
Solvent:
-interact with other charges of molecules – water can spread around ions of other molecules and dissolve them
Effect on Organisms: excellent transport medium, molecules can react in water (cell cytoplasm)
Cohesion
-hydrogen bonds causes water molecules to bond to one another
Effect on Organisms: water is pulled up via capillary action in xylem of tissue
Surface Tension:
-molecules more attracted to water molecules beneath than the air – being pulled down so they are closer together at the top
Effect on Organisms: small animals can walk on water
Density
-ice is less dense than water as the molecules align themselves differently so it floats
Effect on Organisms: reduces heat loss from the body of water maintaining temperature
Molecular Bonding
Elements
-different atoms are elements (periodic table)
-bond together to form molecules (C,H,O,N)
-some are used for important metabolic functions (Na, K, Cl)
Ions – where an atom has gained or lost an electron. Can be cations (positively charged) or anions (negatively charged)
Covalent Bond – a bond between atoms where electrons are shared
Condensation Reaction
-occurs when 2 molecules are joined together and a molecule of water is produced
-OH- from one molecule and H- from another for to make a water molecule (H2O)
Hydrolysis
-molecules are split apart by the addition of water
Polymerisation
-where lots of monomers are joined together to form a polymer
Hydrogen Bonding
-water is polar molecule and hydrogen bonding occurs
-as O is more electronegative, the electrons are closer so this causes the O to be δ-ve and the hydrogen to be δ+ve.
-the hydrogen δ+ve is attracted to δ-ve oxygen and hydrogen bonding occurs
-each water molecule can form 4 hydrogen bonds (1 on either H and 2 on the O)
Water
-it is a polar molecule because the O is slightly negatively charged and the H is slightly positively charged due to the distribution of the
electrons.
-the electrons spend most their time around the O and not H hence the polar charges.
Liquid:
-lots of hydrogen bonds are continuously made and broken in liquid state
Effect on Organisms: provide a habitat for aquatic life, major component of living tissues
High Specific Heat Capacity:
-lots of heat energy is required to break all of the many hydrogen bonds to change it state (lakes, oceans are around a constant temperature)
Effect on Organisms: need stable environment to live; conditions need to be stable for enzyme-controlled reactions to take place
High Latent Heat of Evaporation:
-requires a lot of energy to break all the bonds hence it has a high boiling point
Effect on Organisms: mammals are cooled when sweat evaporates
Solvent:
-interact with other charges of molecules – water can spread around ions of other molecules and dissolve them
Effect on Organisms: excellent transport medium, molecules can react in water (cell cytoplasm)
Cohesion
-hydrogen bonds causes water molecules to bond to one another
Effect on Organisms: water is pulled up via capillary action in xylem of tissue
Surface Tension:
-molecules more attracted to water molecules beneath than the air – being pulled down so they are closer together at the top
Effect on Organisms: small animals can walk on water
Density
-ice is less dense than water as the molecules align themselves differently so it floats
Effect on Organisms: reduces heat loss from the body of water maintaining temperature
