Biological Molecules Flashcards
What is a monomer?
small units which are the components of larger molecules eg monosaccharides- glucose
What is a polymer?
molecules made up of many monomers joined together eg proteins, DNA
How are polymers formed?
polymerisation occurs by condensation reactions and broken down by hydrolysis reactions
What is a condensation reaction?
a chemical bond forms between two molecules and a molecule of water is produced
What is a hydrolysis reaction?
a molecule of water is used to break a chemical bond between two molecules
Why do we need carbohydrates?
energy source, energy reserve and structural support
What are monosaccharides (with examples)
single sugars- glucose, fructose and galactose (last two are isomers of glucose)
What are disaccharides
double sugars formed by the condensation of two monosaccharides resulting in a glycosidic bond (1,4 or 1,6)
Name three disaccharides
maltose- two alpha glucose (1,4)
sucrose- glucose and fructose (1,4)
lactose- glucose and galactose (1,4)
What is a polysaccharide (with examples)?
formed from many glucose units eg starch, glycogen, cellulose
What are carbohydrates?
molecules that exist of carbon, hydrogen and oxygen- mono, di and polysaccharides
What is the structure of starch?
made from amylose- long straight unbranched chain of alpha glucose (1,4 glycosidic bonds) - 1,4 mean it is compact and coiled
and amylopectin- highly branched polymer of alpha glucose (1,4 and 1,6 glycosidic bond)
Describe the structure of amylopectin
it is highly branched which means there are many terminal ends for hydrolysis to occur very quickly (into glucose) enzymes act on ends
large so it is insoluble
What is starch?
main storage component in plants
insoluble so no osmotic effect on plants
compact so lots of energy can be stored in small spaces
What is the structure of glycogen?
same overall structure as amylopectin with more branching (1,4 and 1,6 glycosidic bonds)
allows glucose to be released quicly
polymer of alpha glucose
What is the function of glycogen?
branched so more terminal ends that can be hydrolysed by enzymes to release glucose
polymer of a glucose so releases glucose for respiration
branched/coiled so is compact
insoluble so doesn’t affect water potential of cells
What is the structure of cellulose?
long, straight, unbranched chains of beta glucose joined by condensation
alternate glucose monomers are rotated 180 degrees
What gives cellulose its strength?
long straight chains, microfibrils are joined by hydrogen bonds which gives it strength
Describe the biochemical test for starch
starch- iodine turns from orange to blue black
Describe the biochemical test for reducing sugars
benedict’s reagent- heat in water bath and turns brick red if positive
Describe the biochemical test for non reducing sugars
benedicts reagent- stays blue
add dilute HCL + add sodium hydrogencarbonate, (neutralise) and heat
add benedicts- brick red
What is a reducing sugar?
all monosaccharides and some disaccharides (eg maltose)
What are lipids?
fats and oils made up of hydrogen, carbon and oxygen , main forms are triglycerides and phospholipids
What are the properties of lipids?
insoluble in water, store lots of energy
How do triglycerides form?
condensation reaction between 1 glycerol molecule (-OH) and 3 fatty acids (R-COOH)
forms an ester bond
releases 3 molecules of water
What is a saturated fatty acid?
the r group has no double carbon bonds as much hydrogen bonding as possible no kink in chain high melting and boiling point found in animal fats
What is an unsaturated fatty acid?
r group contains double carbon bonds
kink in chain
lower melting point
found in plant oils
What are the functions of triglycerides?
high energy:mass ratio- high calorific value from oxidation
high proportion of carbon and hydrogen - high calorific value
insoluble in water- no osmotic effect on cells
low density- buoyancy of aquatic animals
What is the structure of phospholipids?
similar to triglycerides but one of the fatty acids is replaced by a phosphate molecule
fatty acids are hydrophobic
phosphate is hydrophilic
What is the function of phospholipids?
forms phospholipid bilayer in aqueous environments
hydrophilic heads are exposed
amphipathic- one end of molecule will mix with water and other end won’t
What are the characteristics of the phospholipid bilayer?
the organisation is spontaneous
large molecules and small polar molecules cant pass through
small non polar molecules, lipid soluble molecules can pass through
What is the test for lipids?
emulsion test- dissolve solid samples in ethanol
add water and shake
milky white emulsion forms if positive
What are proteins?
formed of many amino acids joined together to form polypeptides
proteins are made up of one or more polypeptide
What is the structure of an amino?
amino acids have an amine group (NH2), carboxyl group (COOH) and an R group
20 amino acids
How do amino acids join?
amino acids are joined by peptide bonds in condensation reactions where a molecule of water is released
NH2 joins to COOH group
can form dipeptides or polypeptides
they are broken down by hydrolysis
What is the primary structure of a protein?
sequence of amino acids in the polypeptide chain
determined by the sequence of codons on the mRNA
What is the secondary structure of a protein?
hydrogen bonds form between amino acids (NH and CO group) in chain
can coil into alpha helix- all N-H bonds on same side of protein chain
h bonds parallel to helical axis
can fold into beta pleated sheet- two or more parts of the chain run parallel to each other- linked by h bonds
What is the tertiary structure of a protein?
the 3D shape formed from the coiled or folded chain coiled further
What bonds are found in the tertiary structure?
hydrogen bonds- form between different parts of the polypeptide chain and are numerous and easily broken
ionic bonds- form between carboxyl and amine groups that aren’t involved in peptide bonds and easily broken by changes in pH
disulphide bridges- covalent bonds in sulphur atoms between two cystine amino acids - strong
What is a fibrous protein?
long, narrow strands used for structure and support that are insoluble in water
What is a globular protein?
spherical and compact with a 3D molecular structure involved in metabolic processes
What is the quaternary structure of a protein?
functional protein composed of more than one polypeptide chain
3D structure held together by same bonds as in tertiary structure
Chromatography to separate amino acids
capillary tube to spot mixture onto pencil line
place chromatography paper in solvent
allow solvent to run
use revealing agent to see spots
calculate Rf values and match to database
What is the test for proteins?
the biuret tests for the presence of a peptide bond
add a few drops of sodium hydroxide
add copper sulfate solution
blue to purple if protein is present
enzymes
globular proteins + biological catalysts
speed up reactions by lowering activation energy and are not used up in reactions
induced fit model
substrate binds to active site of an enzyme
enzyme substrate complex forms
active site slightly changes shape so it is complementary to substrate
reduces activation energy
specificity of enzymes
active site is specific to certain substrates
complementary and forms ES complex
active site determined by primary structure/ amino acid sequence and tertiary structure
changes in bonds in tertiary structure change shape of active site- no longer complementary to substrate
temperature
particles have more kinetic energy so more ESc form
collide with more energy to overcome activation energy
high temp causes denaturation as H bonds holding tertiary structure are disrupted which changes shape of active site- no longer complementary
irreversible
pH
once pH goes beyond optimum, enzymes denature
ionic bonds in tertiary structure break/ disrupted
charges on amino acids change so primary structure changes
substrate conc
rate increases with more substrate as more substrates can collide with enzymes to form ESC
levels off as enzyme molecules become saturated with substrate so all active sites are used up
adding more substrate has no effect
enzyme conc
rate increases with more enzymes as more ESC form
at high enzyme conc substrates become limiting factor as there are no more substrates to bind with enzymes and form ESC
inhibitors
prevent the binding of substrates to active sites so fewer ESC are formed
competitive
inhibitor is similar shape to substrate
fits/bind to active site (complementary)
prevent enzyme substrate complexes forming
chemically different so product is not formed
reversible
at high substrate conc, some enzyme is still available to bind so more enzyme substrate collisions + more ESC form
non competitive
attaches to enzyme at site away from active site
changes shape of active site by changing tertiary structure
active site no longer complementary so less substrate can bind
irreversible
at high substrate conc, enzyme is no longer available so less chance of ESC forming
enzyme reactions
catabolic- large molecules are broken down into smaller subunits
eg one substrate binds and is broken into two molecules
anabolic- two molecules enter the enzymes active site and form into one molecule
