Biological molecules Flashcards
What is a monomer?
A small, soluble molecule which can join to other similar monomers
What is a polymer?
A large, insoluble molecule which is made up of many similar repeating monomers
Give 3 examples of monomers, their polymers and biological molecules
- Monomer: monosaccharides
Polymer: disaccharides/polysaccharides
Biological molecule: carbohydrates - Monomer: amino acids
Polymer: polypeptides/proteins
Biological molecule: proteins - Monomer: nucleotides
Polymer: polynucleotides
Biological molecule: DNA/RNA
What is a condensation reaction?
A reaction which forms a chemical bond between monomers whilst releasing a water molecule to make a polymer
What is a hydrolysis reaction?
A reaction that breaks the chemical bond between monomers whilst adding a water molecule
What is the difference between alpha and beta glucose?
The structure (in terms of the far right OH)
Alpha
Below
Beta
Above
What is the chemical formula for disaccharides?
C12H22O11 (there are 2 less hydrogen and 1 less oxygen than C12H24O12 because a water molecule is lost during condensation)
Which disaccharide does alpha glucose and alpha glucose form?
Maltose (malt sugar)
Which disaccharide does alpha glucose and fructose form?
Sucrose
Which disaccharide does alpha glucose and galactose form?
Lactose (milk sugar)
What is a polysaccharide?
Formed by the condensation of many glucose monomers
What type of bonds do disaccharides/polysaccharides have?
Glycosidic bonds
Give 3 examples of polysaccharides
Glycogen, starch and cellulose
Which monomers form glycogen, starch and cellulose?
Glycogen and starch - alpha glucose
Cellulose - beta glucose
How does the structure of beta glucose change in a condensation reaction?
Every other beta glucose molecule is inverted/flipped
How do you test for carbohydrates in REDUCING sugars?
- Add Benedict’s reagent
- Heat at 95°C
- Blue to brick-red colour change
How do you test for carbohydrates in NON-REDUCING sugars (sucrose)?
- Add hydrochloric acid and heat (adds a water molecule so it can be hydrolysed)
- Neutralise with sodium hydrogen carbonate
- Add Benedict’s reagent
- Heat at 95°C
- Blue to brick-red colour change
What happens when a chemical test is performed on sucrose?
Precipitate formed is twice the mass of the sample
How do you test for carbohydrates in STARCH?
- Add iodine in potassium iodide
- Yellow-brown to blue-black colour change
How is the structure of starch related to its function?
- Branched (glucose hydrolysed more quickly)
- Helix shape (compact so lots can fit in a small space for storage)
- Insoluble (doesn’t affect water potential/osmosis)
- Large molecule (can’t diffuse out of plant cells)
How is the structure of glycogen (animal cells only) related to its function?
*Similar to starch (helix, insoluble)
* More highly branched and shorter chains (larger surface area so glucose hydrolysed more quickly)
How is the structure of cellulose related to its function?
Many hydrogen bonds - creates crossbridges between chains of cellulose molecules (microfibrils) which make it stronger (structural carbohydrate)
Give 2 examples of lipids
Triglycerides and phospholipids
What is the difference between saturated and unsaturated fatty acids?
Saturated = single bonds between carbons in long hydrocarbon chain
Unsaturated = double bonds
How are triglycerides formed?
By the condensation of one molecule of glycerol and 3 molecules of fatty acids
Why are triglycerides not polymers?
Aren’t made up of same repeating monomers
What is this called?
O || OH --- C
Carboxylic acid
What types of bonds do triglycerides/phospholipids have?
Ester bonds C - O - C
How are phospholipids different to triglycerides?
Have a phosphate molecule instead of the 3rd fatty acid