biological molecules 3.1 Flashcards
aqa biology as level
what is a monomer?
small units that can create larger molecules
what is a polymer?
a molecule made from repeated units called monomers
what are examples of monomers?
glucose amino acids and nucleotides
what polymers can glucose make?
starch glycogen and cellulose
what polymer do amino acids make?
proteins
what polymer do nucleotides make?
DNA and RNA
what is a condensation reaction?
two molecules joining by forming a chemical bond and the removal of one water molecule
what is a hydrolysis reaction?
the breaking of a chemical bond between two molecules involving the use of water
what bond is formed between the condensation reaction of two monosaccharides?
glycosidic bond
how is a disaccharide formed?
condensation reaction between two monosaccharides
what molecules form maltose?
two glucose molecules through condensation reactions
what molecules form sucrose?
glucose and fructose molecules through condensation reactions
what molecules form lactose?
glucose and galactose molecules through condensation reactions
what are the isomers of glucose?
alpha glucose and beta glucose (OH and H group inverted)
what is the polymers of alpha glucose?
starch and glycogen
how are polysaccharides formed?
formed through the condensation of many glucose monomers
what is the polymer of beta glucose?
cellulose
what is the structure and function of starch?
- found in plants (plant cells) and used to store glucose
- a glucose
- 1,4 and 1,6 glycosidic bonds
- highly branched
- helical and compact
- insoluble
what is the structure and function of glycogen?
- found in animals (muscle cells) and used to store glucose
- a glucose
- 1,4 and 1,6 glycosidic bonds
- highly branched
- insoluble
what is the structure and function of cellulose?
- found in plants (cell wall) and used to strengthen plant
- b glucose
- 1,4 glycosidic bonds
- form long straight chains which are held together by h bonds to form fibrils
- many h bonds provide collective strength
- insoluble
what are two groups of lipids?
triglycerides and phospholipids
how are triglycerides formed?
a condensation reaction between 3 fatty acids and a glycerol molecule
how are phospholipids formed?
a condensation reaction between 2 fatty acids a phosphate and glycerol moleule
what bond forms between a glycerol and fatty acid (RCOOH)?
ester bond
what are the types of R groups in fatty acids?
unsaturated and saturated
what is a saturated fatty acid?
only contain carbon single bonds between carbon atoms in hydrocarbon chains
what is a unsaturated fatty acid?
contains one or more carbon double bond between carbon atoms in hydrocarbon chain
what are the properties of a triglyceride?
- high energy storer
- metabolic water source
- insoluble
- low mass so can be stored compactly
what are the properties of a phospholipid?
- hydrophilic head due to negative charge on phosphate
- hydrophobic tail
- two charged regions so polar
how is the plasma membrane structured?
phospholipid bilayer hydrophobic tails point inwards and hydrophilic heads point outwards to water
what is the amino acid structure?
: R
I
H2N —- C —- COOH
I
H
how is a dipeptide formed?
condensation reaction between two amino acids
how are polypeptides formed?
condensation reaction between many amino acids
what is the primary structure of a protein?
the sequence of amino acids in a polypeptide chain
what is the secondary structure of a protein?
when the chain folds into an alpha helix or beta pleated sheet which is held together by hydrogen bonds
what is the tertiary structure of a protein?
further folding of secondary structure to form a unique 3D shape held together by ionic hydrogen and disulphide bonds
what is the quaternary structure of a protein?
protein made up of two or more polypeptide chains
what is an enzyme?
enzymes are tertiary structures that catalyse reactions by lowering activation energy
what is the active site of an enzyme and how does it relate to enzyme function?
active site is specific and unique tertiary structure (bond position determined by primary structure) meaning enzymes can only attach to complementary substrates
what is the induced fit model?
induced fit is when the active site slightly changes shape to fit the substrate so when an ES complex is being formed there is strain put on the bonds in substrate therefore lowering activation energy
what factors effect enzymes?
- pH
- temperature
- substrate concentration
- enzyme concentration
- inhibitors
how does temperature effect enzyme activity?
if the temperature is to low there is not enough kinetic energy for successful collisions between enzyme and substrate if the temperature is to high enzyme denatures so active site changes shape so no more ES complexes can be formed
how does pH effect enzyme activity?
to high or low pH can affect charges in amino acids in the active site which can change bonds in tertiary structure which can lead to active site changing shape denaturing enzyme so less ES complexes form
how does substrate and enzyme concentration effect enzyme activity?
if there is insufficient substrate so reaction lower so less ES complex formed since fewer collision
if there is insufficient enzymes active site will become saturated with substrate so fewer ES complex formed
what is a competitive inhibitor?
inhibitor has same shape as substrate and binds to active site preventing more ES complexes forming
how are competitive inhibitor effects overcome?
if you add more substrate it will out compete inhibitor
what is a non competitive inhibitor?
inhibitor binds to surface of enzyme (not active site) which causes active site shape to change so no more ES complexes formed
can non competitive inhibitor effects be overcome?
no since substrate can no longer bind to enzyme
what is the test for starch?
- add iodine
- turns from orange to blue/black
what is the test for reducing sugars?
- add Benedict’s reagent and heat
- turns from blue to red brick/orange
what is the test for non reducing sugars?
- add HCL to sample and boil
- cool and use sodium hydrogen carbonate to neutralise
- add Benedict’s reagent and heat
- turns from blue to red brick/orange
what is the test for proteins?
- add biuret
- turns from blue to purple/lilac
what is DNA?
DNA codes for amino acid sequence in primary structure of protein so carries genetic information
what is the structure of a nucleotide?
- deoxyribose
- nitrogenous base
- phosphate group
what are the nitrogenous bases called?
adenine - thymine
cytosine - guanine
what is the polymer of nucleotides?
polynucleotides formed from condensation reaction between many nucleotides
what is the bond between nucleotides called?
phosphodiester
what bond is between complementary nitrogenous bases?
hydrogen
DNA bases are joint together to form which structure?
double helix
what is the structure of RNA?
- ribose
- nitrogenous base
- phosphate group
what are the nitrogenous bases in RNA?
adenine - uracil
cytosine - guanine
what is the difference between RNA and DNA?
RNA is more shorter and is single stranded unlike DNA which is longer and double helix
what is the function of RNA?
RNA transfer the genetic code from DNA in the nucleus to the ribosomes and some RNA (rRNA) combines with proteins to create ribosomes
by which process do DNA replicates?
semi conservative replication
why does DNA need to replicate before division?
to provide new copy for new cell
what are the steps of semi conservative replication?
- DNA helices breaks hydrogen bonds between complementary base pairs unwinding double helix
- each DNA strand acts as a template for free floating DNA nucleotides in nucleus to bind to complementary base pair on template
- DNA polymerase joins together adjacent nucleotides in condensation reaction to form phosphodiester bonds
- two sets of daughter DNA formed each containing one original strand and one new strand of DNA
what is the evidence for semi conservation replication?
- Watson and crick discovered DNA structure
- Meselson and Stahl conducted and experiment which proved DNA replication must be semi conservative
what is ATP?
adenosine triphosphate is an immediate source of energy for biological processes
what is the structure of ATP?
- adenine nitrogenous base
- ribose
- three inorganic phosphate chain
how is ATP formed?
a condensation reaction between ADP + Pi using enzyme ATP synthase during respiration
how is ATP broken apart?
a hydrolysis reaction of ATP into ADP + Pi using enzyme ATP hydrolyse releasing small amounts of energy
what is phosphorylation?
inorganic phosphate released during hydrolysis of ATP can bind to other molecules to make them more reactive eg Pi binds to glucose in beginning of respiration to make more reactive
what bond forms between water molecules?
hydrogen
what are the properties of water?
- important metabolite (hydrolysis and condensation)
- important solvent in reactions
- high heat capacity so can buffer temperature change
- high latent heat of vaporisation can provide cooling effect through loss of water
- strong cohesion between water molecules so can provide surface tension and support water columns
how is water a polar molecule?
has a positive hydrogen end and negative oxygen end
what is an inorganic ion?
inorganic ions occur in cytoplasm and body fluids of organisms in high and low concentrations
what is the role of hydrogen ion?
- lower the pH of solutions and impact enzyme/haemoglobin function
- chemiosmosis
what is the role of iron ions?
component of haemoglobin in transport of oxygen
what is the role of sodium ions?
involved in co transport of glucose and amino acids in absorption
what is the role of phosphate ions?
component of DNA (form phosphodiester bonds with deoxyribose) and ATP (phosphorylation)
