12.1 CARBOHYDRATES Flashcards
WHAT IA A MONOMER?
Small identical or similar molecules which can be condensed (joined or inked together) to make larger molecules called polymers
EXAMPLES- Amino Acids, Monosaccharides and nucleotides
POLYMER
They are large molecules from joining many ( 3 or more) identical or similar monomers together.
EXAMPLES - DNA, RNA, starch and haemoglobin
HOW A BOND IS FORM?
A condensation reaction joins the 2 molecules together with the formation of a chemical bond and involves the elimination of a molecule of water. This is catalysed by an enzyme. H2O is removed.
common monosaccharides
glucose, galactose and fructose
Disaccharides and example
Disaccharides (dimer) are formed by condensation of 2 monosaccharides
Eg. Maltose, Lactose
and Sucrose
Maltose
2 Alpha glucose
Lactose
Alpha glucose + Galactose
Sucrose
Alpha Glucose + Fructose
condensation equation
C6H12O6 + C6H12O6 ——→ C12H22O11 + H2O
Reducing sugar test
Add (equal volume/ 2cm^3) Benedict’s solution and heat
A coloured changed from Blue to green/yellow/orange/red
precipitate indicates the presence of a reducing sugar If there is NO CHANGE in colour there could be a non-reducing sugar present.
Describe how a student would show the of reducing sugars were present in solution
Add equal volumes of Benedict’s solution;
Heat to 95°C
Red/orange/
yellow/green precipitate (shows reducing sugar is present)
Non-reducing sugar test
- Heat a sample with acid for a few minutes to hydrolyse the glycosidic bond then neutralise the solution with an alkali. Acid = HCL Alkali = Sodium hydrogen carbonate
- Heat again with Benedict’s reagent
- Brick red precipitate shows a positive result ( for non resulting sugar)
Unknown conc of sugars
Benedict test (semi-quantitive) test for sugars as it only gives you an idea if sugars are present due to the colours but not the concentration.
colorimeter is quantitive as it measures that intensity of light passing through the solution/sample.
Increasing the amount of sugars increase the mass of the precipitate.
Standardising the method
Samples should always be shaken before testing
Zero the colorimeter before use (with a control)
Use the same filter throughout
Use same volume for each reading
TO DETERMINE CONC OF UNKNOWN SOLUTION
Make up several known conc of maltose/ glucose/ maltose/ lactose/ fructose
Carry out the Benedict’s test on each sample
Take readings of absorbance/transmission using a colorimeter
Plot readings to produce a graph called a calibration curve with
X axis —> concentration of named sugar/ mol dm-3
Y axis ^^ absorbance/transmission /
AU/%
Draw the line of best fit
TRiglycerides
- Make from one molecule of glycerol to 3 fatty acids joined by ester bonds.
- It’s not a polymer as it’s not make from the same/similar monomers.
- They are commonly found in food
- Conducts heat slowly
- Stored around delicate organs to protect them
Saturated
fatty acids don’t have double bonds between carbon atoms within the hydrocarbon chain.
Unsaturated
fatty acids have double bonds between carbon atoms within the hydrocarbon chain.
Test for lipids
- Crush/grind sample (if needed)
- Mix with ethanol and shake
- Then add water
- Forms a cloudy white emulsion if lipid is present.
PHOSPHOLIPIDS
Similar to triglycerides but one of the fatty acids is replaced by a phosphate group
The tails are 2 fatty acid tails - non-polar (no charge) and hydrophobic (hate water)
The phosphate group (PO4^3-) is hydrophilic , is polar and has a negative charge
STARCH
1:4 and 1:6 glycosidic bonds
Branched chain of alpha glucose/coiled into a helix
Structure is compact so it’s good for storage and it takes up less space
Insoluble so it doesn’t affect water potential (osmosis)
LARGE so it’s doesn’t diffuse out of cell
Provides a large surface area for rapid hydrolysis and respiration
GLYCOGEN
ONLY FOUND IN ANIMAL CELLS
similar to starch but:
- it has shorter chains
- More highly branched
- Larger surface area
Stored in muscles and liver
short chains lead to glycogen to be more rapidly hydrolysed into glucose for respiration
Animals require glycogen to be hydrolysed into glucose faster than plants can hydrolyse starch
It’s insoluble like starch
CELLULOSE
Beta glucose are joined through condensation And are flipped 180 degrees one after each one AND FORM 1-4 B-GLYCOSIDIC BONDS
They form long straight unbranched chains
Form microfibrils or macro-fibrils which provide support and strength to place cells as the cell wall are made from cellulose.
Formed by many weak hydrogen bonds between OH groups and adjacent H from another unbranched cellulose molecules to form microfibrils/ macro-fibrils.
Why starch has a spiral shape? Why is it’s shape important for its function in cells.
It is compact/occupies small space/ tightly packed
Explain one way in which starch molecules are adapted for their function in plant cells
- It’s insoluble so doesn’t affect water potential
- Helical SO COMPACT
- Large so molecules can’t leave cell
