Carbohydrates And Lipids Flashcards
What are monomers
Small identical similar molecule which are condensed together to make large molecules called polymers
What are polymers
Larger molecules made from 3+ small identical similar molecules by condensation reaction
What is a condensation reaction?
Removal of a water molecule to form a bond
What is hydrolysis reaction?
Addition of a water molecule to break a bond between two monomer
structure of alpha glucose
Difference between structure of alpha glucose and beta glucose
ABBA
Hydroxyl group below carbon in Alpha glucose
Hydroxyl group above carbon and beta glucose
Glucose plus glucose
Enzyme
Maltose
Maltase
Glucose plus galactose
Enzyme
Lactose
Lactase
Glucose plus fructose
Enzyme
Sucrose
Sucrase
What is the name of the bond between these monomers
Glycolytic bond
Three polysaccharide
Starch
Glycogen
Cellulose
Use of glycogen and starch
Storage in humans and plants
Structure of starch (plants)
Two molecules= amylose and amylopectin
Both alpha glucose
Amylose = has 1-4 glycosidic bonds , helical shape so compact
, insoluble in water so doesn’t effect water potential, large so doesn’t diffuse out of cell
Amylopectin =1-4 and 1-6 glycosidic bonds. Large surface area for rapid hydrolysis by enzymes to realise glucose by respiration
Structure of glycogen
Alpha glucose
Similar to starch but shorter chains , more highly branched, larger surface area
Insoluble in water so doesn’t effect water potential
More shorter chains so more rapid hydrolysis into glucose as faster than in plants
Use of cellulose
Structural molecule in plant cells
Structure of cellulose
Long straight branched chains of beta glucose joined by many weak hydrogen bonds which provide strength and rigidity.
Only 1-4 glycosidic bonds
Forms microfibrils
Every other beta glucose molecule flipped 180°
Benedict test for reducing sugars
- Add equal volumes of Benedict solution.
- Heat to 95°C
- Colour change from blue to brick red precipitate in presence of reducing sugar
Type of non-reducing sugar
Sucrose
Test for non-reducing sugar
- Do reducing sugar test and get negative result
- Heat with acid (HCl) to hydrolyse glycosidic bonds to 95°C
3 . Neutralise with alkali- sodium hydrogen carbonate - Add equal volumes of Benedict solution
- Heat again to 95°C
- Blue to brick red ppt
Iodine test for starch
- Add potassium iodide solution.
- Turns/Black, if presence of starch
What does semiquantitative mean?
We have some idea of sugar quantity present by the range of colours but doesn’t tell the concentration of sugar in the solution
What equipment do you use to test unknown concentration of reducing sugar?
Colorimeter
What does a colorimeter measure?
The intensity of light transmitted through sample
Method to determine concentration of unknown solution (6)
- Make up several known concentrations of name sugar.
- Carry out biochemical test on each sample
- Take readings of absorbance using a colorimeter
- Plot a graph called a calibration curve
X axis = concentration of name sugar
Y axis = absorbance - Draw a line of best fit
- Read unknown sample absorbance and use line of best fit to determine concentration
How to standardise this method (4)
- Sample should always be shaken before testing.
- Zero the colorimeter before you
- Use same absorbent filter throughout
- Use same volume for each reading
Two types of lipids
Phospholipids= form cell membrane of cell
Triglycerides = found in food
Uses of lipids
Conduct heat slowly so good thermal and electrical insulators for your neurons
Stored around delicate organs to protect them
Structure of triglyceride
One glycerol and three fatty acid joined by Ester bond by condensation reaction
What is a unsaturated fatty acid?
Double bonds between carbon atoms within the hydrocarbon chain
Emulsion test
Add ethanol and shake
Add water and shake
If presence of lipid then white cloudy emulsion
Structure of phospholipid
One glycerol, two fatty acids and phosphate group
Features of phospholipids
Phosphate group is hydrophilic as it’s polar
Fatty acids are nonpolar so are hydrophobic
Forms a bilayer
Compare and contrast the structure
and properties of triglycerides and
phospholipids
Both contain ester bonds (between glycerol and fatty acid);
Both contain glycerol;
Fatty acids on both may be saturated or unsaturated;
Both are insoluble in water;
Both contain C, H and O whereas phospholipids also contain P;
Triglyceride has three fatty acids whereas phospholipid has two fatty acids plus phosphate group;
Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region;
.
Phospholipids form bilayer in water whereas triglycerides don’t; (or monolayer on surface)
Why do phospholipids form a bilayer, but triglycerides do not
Phospholipid has two hydrophobic fatty acid tails and a hydrophilic phosphate head
Triglycerides have three hydrophobic fatty acid tails only.
The hydrophilic phosphate group on phospholipids attracts water to either side of the bilayer.
Describe alternative ways to measure the concentration of a reducing sugar.
- Filter and dry precipitate. Find the mass.
