Carbs & Lipids Flashcards
Monomer Definiton
Monomers are small identical or similar molecules which can be condensed to make polymers
Polymer Defintion
Polymers are large molecules made from joining many identical or similar monomers together.
Condensation reaction
joins two monomer units together with the removal of one water molecule.
Hydrolysis reaction
adding one molecule of water to break the bond between two monomers.
Types of monomers and polymers
Monomer, Polymer, Bond, Example
Monosaccharides e.g. α glucose, Disaccharides, Glycosidic Maltose, Lactose
Monosaccharides e.g. α/β glucose, Polysaccharides, Glycosidic Starch, glycogen, cellulose
Amino acids, Polypeptide or protein, Peptide, haemoglobin
Nucleotides,Nucleic acids, Phosphodiester DNA, RNA
Monosaccharides
Glucose (alpha)
Galactose
Fructose
Forming Disaccharides
Glucose+Glucose→Maltose (enzyme=maltase)
Galactose+Glucose→Lactose (enzyme=lactase)
Glucose+Fructose→Sucrose (enzyme=sucrase)
Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein
- Glucose and galactose
- Joined by condensation
- Joined by glycosidic bond
- Added to polypeptide in Golgi
Starch
- energy storage in plants
- amylase= helical
- amylopectin= branched
- insoluble
- a (1-4)(1-6) glycosidic bonds
- large surface area- Does not diffuse out of cells
Cellulose
- cell wall structure in plants
- long, straight, unbranched chains
- insoluble
- B (1-4) glycosidic bonds
- many weak hydrogen bonds cross linked
- chains form microfibrils
- provides strength/ rigidity
Glycogen
- energy storage in animals
- highly branched
- shorter chains
- insoluble
- a (1-4)(1-6) glycosidic bonds
A starch molecule has a spiral shape. Explain why this shape is important to its function in cells
Compact
Give one feature of starch and explain how this feature enables it to act as a storage
substance.
- Helical So compact
- Branched chains So rapid hydrolysis to remove glucose for respiration
Describe how the student would show that reducing sugars were present in a solution.
- Add equal volumes of Benedict’s solution;
- Heat to 95 ⁰C;
- Red precipitate (shows reducing sugar present);
A student carried out the Benedict’s test. Suggest a method, other than using a colorimeter, that this student could use to measure the quantity of reducing sugar in a solution.
Filter
Dry
Weigh
Describe how the student would show that a non-reducing sugar was present in a solution
- Complete Benedict’s test and observe negative result
- Add acid to sugar solution. Heat to 95℃
- Neutralise with alkali
- Add equal volume Benedict’s
- Heat again to 95℃
- Red ppt
- only for sucrose
Producing a calibration curve
- Make up several known concentrations of maltose/glucose/lactose/galactose/ fructose;
- Carry out the Benedict’s test on each sample;
- Use a colorimeter to measure the colour of each solution and plot a calibration curve; Conc on X axis and absorbance on Y.
- Find the concentration of the unknown sample using the calibration curve;
Describe how you would test a sample of food for the presence of starch
- Add potassium iodide solution to the food sample;
- Blue/black indicates starch is present;
Amylase test
- Add biuret (reagent) and becomes purple
- Add starch, test for reducing sugar
Describe how you would test a liquid sample for the presence of lipid box and how you would recognise a positive result.
- Crush
- Mix with ethanol and shake
- Add water and shake
- forms cloudy white emulsion
Lipid Formation
Lipids are formed by joining three fatty acid molecules to a glycerol molecule by condensation reactions, forming Ester bonds.
Triglyceride Formation
one molecule of glycerol joined by Ester bonds to three fatty acids.
Saturated Vs Unsaturated Fatty Acid
Saturated fatty acids do not have any double bonds between carbons within the hydrocarbon chain.
Unsaturated fatty acids do have double bonds between the carbon atoms within the hydrocarbon chain.
Describe how an ester bond is formed in a phospholipid molecule.
- Condensation (reaction)
- Between glycerol and fatty acid;
What are the differences between a triglyceride and a phospholipid?
- Fatty acid removed;
- Replaced with a phosphate group;
Compare and contrast the structure and properties of triglycerides and phospholipids
- Both contain ester bonds
- Both contain glycerol
- Both are insoluble in water
- Both contain C, H and O but phospholipids are also contain P
- Triglyceride has three fatty acids and phospholipids have two fatty acids plus phosphate group
- Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region
- Phospholipids form bilayer but triglycerides don’t.
