1 - Biological Molecules Flashcards
Monomer
one of many small molecules that joins together to make a large one (polymer)
Polymer
a large molecule made up of small repeating units called monomers
Monosaccharide
sweet tasting, soluble, single sugar molecules
General formula of monosaccharides
(CH2O)n
Condensation
joining together of two units/molecules to form a larger one with the elimination of a water molecule
Hydrolysis
breaking apart of two units/molecules to form monomers requiring a molecule of water
Carbohydrates
carbon and water molecules
Carbon’s special properties
can form 4 covalent bonds and bond with itself to form a ‘backbone’ in organic compounds
Glucose
monosaccharide, a hexose (6 carbon sugar), two possible isomers/arrangements
Alpha glucose structure and formula
C6H12O6, OH bonded at the bottom
Beta glucose structure and formula
C6H12O6, OH bonded at top on right side
Reducing sugar (all mono and some disaccharides)
a sugar that is able to donate an electron to another chemical
Reduction
a chemical reaction that involves the gain of electrons or hydrogen
Benedict’s reagent
an alkaline solution of copper II sulfate, when heated with a reducing sugar it forms an insoluble red precipitate of copper oxide
Method to test for reducing sugars
add equal volume of (liquid) sample to Benedict’s reagent, heat in a water bath for 5 minutes
Disaccharides
monosaccharides bonded in pairs
Maltose
glucose + glucose
Sucrose
fructose + glucose
Galactose
lactose + glucose
Monosaccharide bonding
a condensation reaction occurs and a glycosidic bond is formed, a molecule of water is released
Disaccharides splitting/breaking apart
a hydrolysis reaction occurs and a glycosidic bond is broken, a molecule of water is required
Non-reducing sugars
sugars that cannot donate an electron to another chemical (eg. sucrose), must be hydrolysed to see if it is non-reducing
Test for non-reducing sugars
Benedict’s test as normal, if a reducing sugar is not shown to be present add equal volume of fresh sample to HCl. Heat in a water bath for 5 mins (hydrolysis). Slowly add NaHCO3 to neutralize. Test pH to check alkalinity. Retest with Benedict’s reagent, if goes orange/brown, non-reducing sugar present in initial sample
Polysaccharide
many monosaccharides bonded with glycosidic bonds from condensation reactions
Polysaccharide properties
Insoluble so good for storage, when hydrolysed form monos. and disacc.
Some are used for structural support in plants (cellulose)
Starch
200-100000 alpha glucose molecules bonded together by glycosidic bonds, can be branched or unbranched
Starch; where it is found
found as granules/grains in plants, in seeds and storage organs
Starch; role
main role is energy storage, important component in foods as it is main energy source
Starch; structure
Insoluble so doesn’t affect water potential or diffuse out of cells, hydrolysed into alpha glucose monomers for respiration, wound into tight coils so compact (large amounts of energy can be stored in a small space)
Glycogen
found in animals but not plants, main carb storage, shorter and more highly branched than starch, stored as granules in liver and muscles
Glycogen; suitable for storage
Insoluble so doesn’t affect water potential (osmosis), doesn’t diffuse out of cells, compact so large amounts of energy stored in small space
Glycogen; short and highly branched
quicker to be worked at by enzymes to produce glucose for respiration
Cellulose
straight, unbranched, parallel chains of beta glucose, chains grouped together in microfibrils (arranged in fibres)
Cellulose; cross linkages
hydrogen bonds form cross links that overall add to its strength making it a valuable structural material
Cellulose; uses
cell wall - gives cells rigidity and stops them bursting due to too much water entering by osmosis
Important for stems and leaves to maintain max. SA
Cellulose; rotation
alternate molecules rotated 180 degrees so -OH groups are next to each other to form glycosidic bonds
Triglycerides
formed by the condensation of one molecule of glycerol and three molecules of fatty acid to form ester bonds
Triglycerides; source of energy
high ratio of energy storing carbon-hydrogen bonds to carbon atoms so excellent source of energy
Triglycerides; low mass to energy ratio
store lots of energy in a small volume, beneficial to animals as it reduces volume of mass they have to carry around
Triglycerides; non-polar molecules
large, non-polar and so insoluble in water - doesn’t affect water potential in cells
Triglycerides; ratio of hydrogen to oxygen
high ratio of hydrogen to oxygen atoms, so releases water when oxidised - important source of water in desert animals
Triglycerides; differences in properties
differences in properties of triglycerides is due to differences in the structures of the fatty acids they contain
Fatty acids
represented by RCOOH, R represents a saturated or unsaturated backbone, all have the functional group -COOH (carboxyl group)
Fatty acids; saturation
can be saturated, monounsaturated or polyunsaturated
Saturated
no double bonds between CARBON atoms
Monounsaturated
one double bond between CARBON atoms
Polyunsaturated
more than one double bond between CARBON atoms
Phospholipids
lipid containing a phosphate group, consists of a molecule of glycerol, 2 molecules of fatty acid and one phosphate molecule
Phospholipids; properties
hydrophilic head (phosphate) and hydrophobic tail (fatty acids), makes them polar molecules as they have two poles/ends that behave differently with water
Phospholipids; bilayers
in aqueous environments they form a phospholipid bilayer (eg. within cell membranes) causing a hydrophobic barrier to be formed between the inside and outside of a cell
Phospholipids; glycolipids
phospholipid structure allows them to combine with carbohydrates to form glycoproteins within the cell membrane, these are important in cell recognition
Glycerol
each of the three OH hydroxyl groups can form an ester bond (C-O-C) with a fatty acid or phosphate group
Phosphate group
RPO2(OH)2 - hydrophilic groups that form an ester bond when they bond to glycerol
Amino acids
monomer units of polypeptide chains, which make up proteins
have a central carbon atom with a amine group, carboxyl group, R group, and hydrogen attached
Peptide bonds
bonds that form between amino acids in condensation reactions (between carboxyl group and amine group)
Primary structure of proteins
sequence of amino acids in polypeptide chain
decides its ultimate shape and hence function
Secondary structure of proteins
H bonds between -NH group at one location and -C=O group at another location
causes polypeptide chain to be held in a folded shape eg. helix
Tertiary structure of proteins
secondary structure (helix) can often be twisted and coiled further by ionic bonds and disulfide bridges to give a more complex shape
Disulfide bridges in proteins
single covalent bond between two sulphur atoms of different amino acids, strong and not easily broken
Ionic bonds in proteins
form between any carboxyl and amino groups that are not involved in forming peptide bonds
weaker than disulfide bridges
easily broken by changes in pH
Quaternary structure of proteins
structure formed by presence of many polypeptide chains linked together
may include non-proteins (prosthetic) components eg. haem group
Biuret test for proteins
add sample to test tube
add equal volume of sodium hydroxide solution
add few drops of very dilute copper II sulphate solution
purple colour indicates presence of peptide bonds and hence proteins
alternatively, add Biuret solution to sample for same observations
Enzymes
globular proteins that act as biological catalysts by lowering the activation energy of reactions (allows metabolic processes to occur at internal body temperature
Catalysts
alter the rate of chemical reaction without undergoing permanent changes themselves (can be reused and so are effective in small amounts)
For reactions to occur naturally:
reactant molecules must collide with SUFFICIENT ENERGY to alter the arrangement of atoms
the free energy of the reactant must be more than that of the products
activation energy must be supplied
Functional region of enzyme…
active site
Induced fit model
active site forms as the enzyme and substrate interact, enzymes can change the shape of their active site so that it is complementary to the substrate
as it changes shape, strain is put on the substrate molecule, distorting bonds in the substrate and lowering the activation energy
Substrate and enzyme have shapes that are
complementary (not the same but have ability to fit together)
Enzyme + substrate =
enzyme-substrate complex
Lock and key theory
a substrate will only fit the active site of a particular enzyme
(suggests enzymes have a rigid structure)
Competitive inhibitors
have a molecular shape similar to that of the substrate and is also complementary to the active site of the enzyme
able to occupy enzymes active site and prevent formation of enzyme-substrate complexes
Substrate concentration increased, effect of COMPETITIVE inhibitor…
reduced
Non-competitive inhibitors
bind to the enzyme at a site other than the active site, this alters the shape of the enzyme and hence the shape of the active site
prevents formation of enzyme-substrate complex
Substrate concentration increased, effect of NON-COMPETITIVE inhibitor…
not changed - the substrate and non-competitive inhibitor are not competing for the same site
