Biological Molecules Flashcards
Define monomer and give some examples
Monomers are smaller units that join together to form larger ones.
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 during a condensation reaction?
2 molecules join together and form a chemical bond and a water molecule is removed
What happens during a hydrolysis reaction?
A water molecule is used to break a chemical bond between 2 molecules.
Name the 3 hexose monosaccharides and their chemical formula.
glucose
fructose
galactose
C₆H₁₂O₆
Name the type of bond formed when monosaccharides react
glycosidic bonds (1,4) or (1,6)
2 monomers = disaccharide
multiple monomers = polysaccharide
Name 3 disaccharides and describe how they form
Maltose: glucose+glucose
Sucrose: glucose+fructose
Lactose: glucose+galactose
condensation reaction forms glycosidic bond between 2 monosaccharides
Describe the structure of starch
amylose:
1,4 glycosidic bonds
helix with intermolecular hydrogen bonds meaning it is compact (can fit into small spaces)
amylopectin:
1,6 glycosidic bonds
branched structure so there is a larger surface area for quick hydrolysis to glucose
Describe the functions of starch
Storage polymer of alpha-glucose in plant cells
it is insoluble so no osmosis can happen
large so does not diffuse in and out of cells
Describe the structure of glycogen
1,4 and 1,6 glycosidic bonds
Describe the structure of glycogen
insoluble so no osmosis occurs
compact
Describe the functions of glycogen
main storage polymer of alpha-glucose in animal cells (also found in plant cells)
found in muscle and liver cells
Describe the structure of cellulose
1,4 glycosidic bonds
straight chain/unbranched molecule
hydrogen bonds between layers to form microfibrils for increased strength
Describe the function of cellulose
polymer of beta-glucose
provides strength to plant cell wall (holds stem up, prevents bursting) Describe the function of cellulose
Describe the benedicts test for reducing sugars
- Add an equal volume of benedicts reagent to a sample
- Heat the mixture in a water bath at 100 for 5 minutes
- A positive result will show a colour change from blue to brick-red, orange, yellow or green.
(brick-red shows there are a lot of reducing sugars, green shows there aren’t as many)
Describe the benedicts test for non reducing sugars
- Prove it is a non reducing sugar by carrying out the benedicts test and getting anegative result (colour blue)
- Hydrolyse non reducing sugars by adding acid and heat in a water bath.
- Neutralise the mixture by adding an alkali
- Redo the benedicts test for a positive result
Describe the test for starch
- Add iodine solution
- A positive result will show a colour change to black/blue
Describe how to test for lipids in a sample
- Dissolve solid sample in ethanol
- Add water and shake gently
- Positive result is milky white emulsion
How do triglycerides form?
condensation reaction between 1 molecule of glycerol and 3 fatty acids to form ester bonds
Contrast saturated and unsaturated fatty acids
saturated:
contain single bonds only between carbon atoms
higher melting point
solid at room temp
unsaturated:
has atleast one double bond between carbon atoms
lower melting point
liquid at room temperature
Relate the structure of triglycerides to their functions
Insoluble hydrocarbon chain = no effect on water potential hence used for waterproofing.
slow conductor of heat + used as a thermal insulation.
Describe the structure and function of phospholipids
a glycerol backbone attached to 2 hydrophobic fatty acid tails and 1 hydrophilic polar phosphate head.
Tails splay outwards for waterproofing.
Compare phospholipids and triglycerides.
Both have a glycerol backbone.
Both may be attached to saturated/unsaturated/polyunsaturated fatty acids
Contrast phospholipids and tryglycerides.
phospholipids:
2 fatty acids and 1 phosphate group.
Hydrophylic head and hydrophobic tail.
Used primarily in membrane formation.
Triglycerides:
3 fatty acids
Entire molecule is hydrophobic.
Used primarily as a storage molecule.
What does hydrophobic mean?
Doesn’t like water