Biological Molecules Flashcards
define monomer and give some examples
small units that join together to form larger molecules
-monosaccharides (glucose, fructose, galactose)
-amino acids
-nucleotides
define polymer and give some examples
molecules formed when many monomers join together
-polysaccharides
-proteins
-DNA/RNA
what happens in a condensation reaction?
a chemical bond forms between to molecules and a molecule of water is produced
what happens in a hydrolysis reaction?
a water molecule is used to break a chemical bond between 2 molecules
name 3 hexose monosaccharides
-glucose
-fructose
-galactose
all have the molecular formula C6H12O6
name the type of bond formed when monosaccharides react
(1,4 or 1,6) glycosidic bond
if there are 2 monomers there’s 1 chemical bind and it’s called a disaccharide
if there are multiple monomers there will be many chemical bonds so it’s called a polysaccharide
name 3 disaccharides and describe how they form
-maltose: glucose + glucose
-sucrose: glucose + fructose
-lactose: glucose + galactose
a condensation reaction forms a glycosidic bond between 2 monosaccharides
they all have the formula C12H22O11
draw the structure of alpha glucose
now google it to check you did it right :)
(going round clockwise, the OH should be down down up down)
draw the structure of beta glucose
now google it to check you did it right
(going clockwise the OH should be up down up down)
describe the structure and functions of starch
starch is a storage polymer of alpha glucose in plant cells
- it’s insoluble so it has no osmotic effect on plants
- its large so it doesn’t diffuse out of cells
starch is made from amylose:
- 1,4 glycosidic bonds
- helix structure with intermolecular H-bonds so it is is compact
and from amylopectin:
- 1,4 and 1,6 glycosidic bonds
- is branched so it has many terminal ends for hydrolysis into glucose
describe the structure and functions of glycogen
it’s the main storage polymer of alpha glucose in animal cells (but it is also found in plant cells)
- 1,4 and 1,6 glycosidic bonds
- is branched so it has many terminal ends for hydrolysis
- it is insoluble so there is no osmotic effect and it does not diffuse out of cells
- it is compact
describe the structure and functions of cellulose
it is a polymer of beta glucose which gives righty to plant cell walls (prevents bursting under turgid pressure and holds stem up)
-1,4 glycosidic bonds
- straight chain in branched molecule
- Hbond cross links between parallel strands from microfibrils so it has high tensile strength
describe the benedict’s test for reducing sugars
1) add an equal volume of benedict’s reagent to a sample
2) heat the mixture in an electric water bath at 100 degrees C for 5 mins
3) positive result: colour change from blue to orange and brick red precipitate forms
describe benedict’s test for non reducing sugars
1) negative result: benedict’s reagent remains blue
2) hydrolyse non-reducing sugars (eg sucrose) into their monomers by adding 1cm cubed of HCl. heat in boiling water bath for 5 mins
3) neutralise mixture using sodium carbonate solution
4) proceed with benedict’s test as usual
describe the test for starch
1) add iodine solution
2) positive result: colour change from orange to blue-black
outline how colorimetry could be used to give qualitative results for the presence of sugars and starch
1) make standard solutions with known concentrations. record absorbance or % transmission values
2) plot calibration curve: absorbance or % transmission (y-axis), concentration (x-axis)
3) record absorbance or % transmission values of unknown samples. use calibration curve to read off concentration
describe how to test for lipids in a sample
1) dissolve solid samples on ethanol
2) ass an equal volume of water and shake
3) positive result: milky while emulsion forms
how do triglycerides form
condensation reaction between 1 molecule of glycerol and 3 fatty acids forms ester bonds
contrast saturated and unsaturated fatty acids
saturated
-contain only single bonds
-straight chain molecules have many contact points
-higher melting point (solid at room temperature)
-found in animal fats
unsaturated
-contain carbon carbon double bonds
-‘kinked’ molecules have fewer contact points
-lower melting point (liquid at room temperature)
-found in plant oils
relate the structure to function of triglycerides
-high energy to mass ratio so there is high calorific value from oxidation
-insoluble links hydrocarbon chain so no effect in water potential of cells and used for waterproofing
-slow conductor of heat so has thermal insulation
-less dense than water so helps buoyancy of aquatic animals
describe the structure and function of phospholipids
amphipathic molecule: glycerol backbone attached to 2 hydrophobic fatty acid tails and 1 hydrophobic polar phosphate head
- forms phospholipid bilayer which is the component of membranes
- the tails can go outwards which makes it waterproof
compare phospholipids and triglycerides
- both have glycerol back bone
- both may be attached to a mixture of saturated, monounsaturated and polyunsaturated fatty acids
- both contain the elements C, H, O
- both formed by condensation reactions
contrast phospholipids and triglycerides
phospholipids
- 2 fatty acids and 1 phosphate group attached
-hydrophilic head and hydrophobic tail
- used primarily in membrane formation
triglycerides
- 3 fatty acids attached
- entire molecule is hydrophobic
- used primarily as a storage molecule
are phospholipids and triglycerides polymers?
NO; they are not made from a small repeating unit. they are macromolecules
why is water a polar molecule?
oxygen is more electro negative than hydrogen so it attracts the electron density in the covalent bond more strongly
forms oxygen delta negative (slightly negative charge) and hydrogen delta positive (slightly positive charge)
state 4 biologically important properties of water
due to polarity and intermolecular hydrogen bonds
- metabolite/ solvent for chemical reactions in the body
- high specific heat capacity
- high latent heat of vaporisation
- cohesion between molecules
explain why water is significant to living organisms
- solvent for polar molecules during metabolic reactions
- enables organisms to avoid fluctuations in core temperature
- cohesion-tension of water molecules in transpiration stream
what are inorganic ions and where are they found in the body?
- ions that do not contain carbon atoms
- found in cytoplasm and extra cellular fluid
- may be in high or very low concentrations
explain the role of hydrogen bonds in the body
- high concentration of H+ ions means there is a low (acidic) pH
- H+ ions interact with H-bonds and ionic bonds in tertiary structure of proteins, which can cause them to denature
explain the role of iron ions in the body
- Fe2+ binds to porphyria ring to form haem group in haemoglobin
- haem group has binding site to transport 1 molecule of O2 around the body in the blood stream
- 4 haem groups per haemoglobin molecule
explain the role of sodium ions in the body
- involved in cotransport for absorption of glucose and amino acids in lumen of gut
- involved in propagation of action potentials in neurons
explain the role of phosphate ions in the body
component of:
- DNA
- ATP
- NADP
- cAMP
