biological molecules Flashcards
describe the structure of a water molecule
oxygen atom covalently bonded to 2 hydrogen atoms. It is a non-linear shape
what bond can link two water molecules together
hydrogen bond
what is a hydrogen bond
a weak interaction that can occur whenver moleucles contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen
where does hydrogen bonds occur between water molecules
between a hydrogen on one molecules and the oxygen of another molecule
define polar
has 2 poles - one slightly positive, other slightly negative
why is water a polar molecule
electrons are more attracted to the oxygen atom so is pulled towards it, causing the O to be slightly negative and the Hs to be slightly positive
define electronegativity
measure of the tendency of an atom to attract a bonding pair of electrons
define electronegativity
measure of the tendency of an atom to attract a bonding pair of electrons
define dipole
a molecule in which a concentration of positive electric charge is separated from a concentration of negative charge
list roles water plays in life
solvent, transport medium, habitat, reactant, thermal stability, solvent
why is water a useful solvent
polar and charged molecules interact with polar water molecules - cluster around them which keeps them apart
why is water a useful transport medium
water stays a liquid over a large temperature range - H bonds require lots of energy to break.
why is water a useful coolant
high specific heat capacity - H bonds require lots of energy to break
why is water a useful habitat
maintains a constant temp.
why is water a useful habitat
maintains a constant temperature due to energy required to break H bonds
define hydrophilic
property of a molecule that is attracted to water
define hydrophobic
property of a molecule that is repelled by water
define cohesion
water molecules attracted to one another
define adhesion
water molecules attracted to other substances
how is water being transparent to light make it useful for life
plants growing under water can get light for photosynthesis and aquatic animals can see underwater
explain how water can dome above the level of the container it is in
cohesion between water molecules causing surface tension due to hydrogen bonds
explain how water can form a meniscus in a measuring cyclinder
adhesion to sides of container draws molecules up
explain capillary action of water in a narrow tube
cohesion between water molecules and adhesion to other molecules causes water to move up narrow spaces
define monomer
individual molecules that make up a polymer
define polymer
long-chain molecules compsed of multiple individual molecules (monomers) in a repeating pattern
define macromolecule
large complex molecules with large molecular masses
define dimer
a molecule consisting of two identical molecules linked together
define oligomer
a polymer whose molecules consist of relatively few repeating units
define condensation reaction
reaction between two molecules to form a bigger one, releases a water molecule
define hydrolysis reaction
the breakdown of a molecule into two smaller molecules requiring the addition of a water molecule
define metabolism
chemical processes in a living organism in order to maintain life
define catabolic reaction
reactions of metabolism that break molecules into smaller units. release energy
define anabolic reaction
reactions of metabolism that construct molecules from smaller units - require energy from hydrolysis of ATP
4 main categories of biological molecule
carbohydrates
lipids
proteins
nucleic acids
what is a single bond
chemical bond which one pair of electron is shared between two atoms
define double bond
chemical bond that shares two pairs of electrons between two atoms
what elements are present in carbohydrates
carbon, hydrogen, oxygen
general formula of carbohydrates
(CH2O)n
define monosaccharide
a single sugar molecule
define disaccharide
a molecule comprised of two monosaccharides joined by a glycosidic bond
define polysaccharide
a polymer made of many sugar monomers
define pentose sugar
a monosaccharide composed of 5 carbons
define hexose sugar
a monosaccharide composed of 6 carbons
define triose sugar and give an example
monosaccharide composed of 3 carbons
e.g. glyceraldehyde
define furanose ring
5 membered ring
e.g. fructose
define pyranose ring
a 6-membered ring e.g. glucose
define isomer
molecules with same atoms but arranged differently
what is the difference between alpha and beta glucose
the hydrogen and hydroxyl groups on carbon 1 are reversed
what are the differences between alpha glucose and ribose
glucose is pyranose, ribose is furanose
glucose used in starch and glycogen
ribose used in RNA
which monosaccharides make up sucrose
alpha glucose and fructose
which monosaccharides make up maltose
two alpha glucose
which monosaccharides make lactose
alpha glucose and galactose
how do two glucose molecules form a disaccharide
condensention reaction on carbons 1 and 4, between hydroxyl groups
water is lost, bond is formed by remaining oxygen atom
what is the reaction that breaks glycosidic bonds
hydrolysis - breaking the bond by the addition of water
why does alpha glucose form starch and beta glucose form cellulose
due to the arrangement of the H/OH on carbon 1.
1-4 glycosidic bonds in alpha glucose mean they can bond all facing the same way up but beta needs need to flip 180 degrees every time.
which polysaccharides make up starch
amylose (1-4 bonds only) and amylopectin (both 1-4 and 1-6)
why are glycosidic bonds 1-4, 1-6
describes the bonds between the OH group on either carbon 1-4 or 1-6
describe the structure of cellulose fibre
several cellulose molecules = microfibril
several microfibrils = macrofibril
macrofibrils laid down in layers to form cell wall
what are the properties and functions of starch
coils into helix
amylase unbranched, amylopectin branched
compact and insoluble - ideal for storage, food store in plants
properties and functions of glycogen
more branched than amylopectin
coils into helix
compact and insoluble - ideal for storage in animals and fungi
properties and functions of cellulose
