2) Biological Molecules Flashcards
benedict’s test for reducing sugars
- Add Benedict’s reagent (which is blue as it contains copper (II) sulfate ions).
- Heat the test tube in a water bath/beaker.
- A positive test result is a colour change somewhere along a colour scale from blue
(no reducing sugar) to brown/brick-red (a high concentration of reducing sugar)
-This test is semi-quantitative as the degree of the colour change can give an
indication of how much (the concentration of) reducing sugar present
iodine test for starch
positive : blue-black
negative : orange-brown
emulsion test for lipids
- Add ethanol to the sample ,
shake to mix
add the mixture to a test tube of water. - positive : milky emulsion
negative : clear
biuret test for proteins
- A few drops of copper (II) sulfate solution (which is blue) is added to the sample.
-positive : lilac/purple
negative : remains blue
For this test to work, there must be at least two peptide bonds present in any protein
molecules, so if the sample contains amino acids or dipeptides, the result will be
negative.
benedict’s test for non-reducing sugars
add hydrochloric acid, and neutralise
- then add benedicts solution and heat
colourimeter
- measures absorbance and transmission.
- the paler the solution, the lower the absorbance, higher the transmission (as more light can pass through the sample).
- calibration curve used
serial dilutions
are created by taking a series of dilutions of a stock solution. The
concentration decreases by the same quantity between each test tube
what is a macromolecule ?
a large biological molecule (like protein/polysaccharide/nucleic acid)
define monomer
used as basic building block for SYNTHESIS OF POLYMER.
- many monomers join to form a polymer (usually by condensation reactions)
define polymer
made from many similar repeating subunits joined together in a chain (eg. polysaccharides, proteins, nucleic acids, cellulose)
define monosaccharide
consisting of single sugar unit with general formula (CH2O)n
eg : alpha & beta glucose
define disaccharide
sugar molecule consisting of 2 MONOSACCHARIDES joined together by a GLYCOSIDIC BOND
define polysaccharide
subunits are monosaccharides joined together by glycosodic bonds.
Eg: cellulose, glycogen
whats a glycosidic bond?
bonds between monosaccharides/disaccharides/polysaccharides
name 3 monosaccharides
-glucose
-fructose
-galactose
whats the difference between alpha & beta molecules ?
alpha - both OH is on the bottom
beta - rhs OH is above
glucose, fructose, and maltose are _______ sugars
reducing sugars
is sucrose reducing or non-reducing sugar
non-reducing sugar
what are the 2 branches of starch?
- amylose
- amylopectin
state bonds joining amylose & whether it has branching
- alpha 1-4
- no branching
state bonds joining amylopectin & whether it has branching
- alpha 1-4 & alpha 1-6
- yes branching
state bonds joining glycogen & whether it has branching
- alpha 1-4 & alpha 1-6
- yes branching (more than amylopectin)
state bonds joining cellulose & whether it has branching
- beta 1-4
- no branching
structural description of amylose
- helical
-long - compact
structural description of amylopectin
- helical
- compact
structural description of glycogen
- helical
- compact
structural description of cellulose
- long straight chains
- every other glucose is inverted 180 (flipped)
- bonded via hydrogen bonds
- make microfibrils
functions of amylose
- cellular storage of energy
- does not affect osmotic potential
- found in plants
functions of amylopectin
- cellular storage of energy
- does not affect osmotic potential
- found in animals
- hydrolysed faster than amylose
functions of glycogen
- cellular storage of energy
- does not affect osmotic potential
- found in animals
- hydrolysed faster than amylose
functions of cellulose
- high tensile strength
- insoluble but permeable to water
- strong cell wall for support + prevent osmotic damage
branching = 1-6 bonds
branching = 1-6 bonds
what does non-polar mean ?
hydrophobic
- lack complete/partial charges on their atoms
- insoluble in water
- cannot form hydrogen bonds with water
what does polar mean ?
hydrophilic
- possess regions of positive & negative charge
triglycerides are polar or non-polar?
non-polar hydrophobic
functions of triglycerides
- energy storage (insoluble in water).
- waterproofing of hair/feathers (oily secretions of glands).
- electrical insulation
- insulates body against heat loss.
- increases ability to float well.
describe the molecular structure of a phospholipid
- polar phosphate head
- non-polar fatty acid tail
explain primary structure
- the number, type, and sequence of amino acids
explain secondary structure
- COILING
- often folds/ curls up.
- 3D shape : alpha helix + beta-pleated sheet.
- held in shape by hydrogen bonds.
explain tertiary structure
- 3D globular shape.
- intramolecular bonding.
- 4 types of bonds that hold it in place: hydrogen bond, disulphide bond, ionic bond, hydrophobic interactions
- bonds between R groups are on same polypeptide
explain quaternary structure
- 2 or more polypeptides
- intramolecular bonding
- same 4 bonds as tertiary (hydrogen, disulphide, ionic, hydrophobic interactions)
- can have prosthetic group
- bonds between R groups are on different polypeptides
what’s a prosthetic group?
proteins w non-polypeptide structure = conjugated proteins
describe the 4 types of bonding that holds tertiary and quaternary structures in place. (bonding is between..?)
- hydrogen bonding : between polar R groups.
- ionic bonds between charged R groups.
- hydrophobic interactions between non-polar R groups.
- disulfide bonds between cysteine.
describe the structure of haemoglobin.
- globular protein
- quaternary structure (from 2 alpha chains, 2 beta chains, 1 haem group)
- intramolecular bonding
what is a haem group?
prosthetic group
globular proteins
- soluble
- physiological roles
fibrous proteins
- insoluble
- structural roles
examples of fibrous proteins
keratin(in hair), collagen (in bone)
examples of globular proteins
enzymes, haemoglobin, insulin, antibodies
difference of shape between fibrous and globular proteins
fibrous - long and narrow
globular - round
difference of acid sequence between fibrous and globular proteins
fibrous - repetitive amino acid
globular - irregular amino acid sequence
difference of durability between fibrous and globular proteins
fibrous - less sensitive to changes in temp, pH.
globular - more sensitive
explain the high specific heat capacity of water
- a lot of heat capacity has to be added to water to raise its temp.
- much of the heat energy is used to break hydrogen bonds between water.
explain why high specific heat capacity of water is beneficial for fish
-As it takes so much energy to raise the temperature of the lake water, the temperature will remain relatively stable despite the fluctuating external environment preventing their enzymes denaturing
Polar molecules dissolve in water e.g NaCl (salt). Explain how this works in terms of the ions
Na+ ions are attracted to the oxygen in water
-Cl- ions are attracted to the hydrogen in water
What is meant by the latent heat of vaporisation?
b) Why is it high for water?
energy required to convert water from a liquid to a gas
b) a lot of energy is needed to break the hydrogen bonds
How does the high heat of vaporisation of water favour us when we sweat?
- a large amount of heat is removed from your skin to break the hydrogen bonds to turn it into a gas
- provides a cooling effect for our skin
glucose + fructose = ?
sucrose
how is sucrose made
glucose + fructose
how is maltose made
glucose + glucose
how is lactose made
glucose + galactose
differentiate between saturated and unsaturated atoms
saturated = only single bonds
unsaturated = atleast one double bond
differentiate between semiquantitative & quantitative
- semiquantitative = ESTIMATION of their approximate concentrations.
- quantitative = ACCURATE determination of their concentrations.
differentiate between simple & serial dilutions
- simple = singlestep process
- serial = when the steps are repeated
3 facts about collagen
- every 3rd amino acid is glycine (repeating sequence = makes tightly held together).
- 3 polypeptide chains = quaternary structure.
- fibrous protein.
- held by hydrogen bonds
