1.1,1.2&1.3 Monomers And Polymers, Carbs and Lipids Flashcards
What are monosaccharides?
•Monosaccharides are the monomers from which larger carbohydrates are made.
•Glucose, galactose and fructose are common monosaccharides.
•Simplest - single sugars
•Same number of C as O atoms
•Have the general formula (CH20) n
where n is any number between 3 and 7
•White crystalline solids
•Dissolve in water to form sweet tasting
solutions
What forms a glycosidic bond?
A condensation reaction between two monosaccharides
How are disaccharides formed?
formed by the condensation of two monosaccharides
What are carbohydrates?
Carbohydrates are organic compounds which comprise
of only
C, H, and O
Carbo-Hydr-ate
What are the types of carbohydrates?
Monosaccharides
Disaccharides
Polysaccharides
What is maltose?
a disaccharide formed by condensation of two glucose molecules
What is sucrose?
a disaccharide formed by condensation of a glucose molecule and a fructose molecule
What is lactose?
a disaccharide formed by condensation of a glucose molecule and a galactose molecule
What are the structures of glucose?
alpha glucose and beta glucose
What does the alpha structure look like?
H |__ O H
\/ \ /
/ \ \ /
HO \____/ \OH
What is the structure of β-glucose?
H |__ O OH
\/ \ /
/ \ \ /
HO \____/ \H
What are alpha and beta glucose?
Isomers
How are polysaccharides formed?
By the condensation of many glucose units
What are the three types of polysaccharides?
Starch
Cellulose
Glycogen
What is the structure and function of starch?
•The alpha -helical/ spiral structure of starch makes it good for storage (it’s compact)
•Starch is insoluble due to its structure which means it doesn’t affect the water potential of cells (stops movement of water by osmosis)
•It is therefore the main plant storage sugar
- Starch is a mixture of two polysaccharides: amylose and amylopectin
- Amylopectic is branched. The branches are hydrolysed by enzymes to quickly release the glucose
- Starch is made from alpha glucose
What is the structure and function of cellulose?
•Cellulose contains beta - glucose joined by glycosidic bonds
•Alternate glucose molecules are inverted
•Beta glucose bonds are rigid, so cellulose molecules form straight chains
•Hundreds of chains are linked together by hydrogen bonds between the chains to form cellulose microfibrils
What is the structure and function of glycogen?
•Glycogen is formed from alpha-glucose
•Glycogen is insoluble
•Glycogen is more branched than starch it acts as a storage compound in animals
• compact
What are the two groups of lipid?
Triglycerides and phospholipids
How are triglycerides formed?
By the condensation of one molecule of glycerol and three molecules of fatty acid
What bond is formed between glycerol and a fatty acid?
An ester bond
Is the R-group of a fatty acid saturated or unsaturated?
Both
What are phospholipids made from?
Glycerol and fatty acids (only 2) and a phosphate group
What do the spare charges on the phosphate group mean?
Means that it can form hydrogen bonds with water so the phosphate region is hydrophilic but the other ends are still hydrophobic
Hydrophilic
Likes water
Hydrophobic
Doesn’t like water
What are the properties of the phosphate group head?
Polar and hydrophilic
What are the properties of the fatty acid tail?
Non-polar and hydrophobic
Why is the phospholipid structure the shape it is?
Due to their polar nature and the way they interact with water
What happens when phospholipids are exposed to water?
Form micelle or bilayer
Which way do the heads and tails face in a phospholipid?
Hydrophilic heads face water
Hydrophobic tails face inwards
Where does the condensation reaction occur in a triglyceride
Between the carboxyl group of the fatty acid and the hydroxyl group of the glycerol
Properties of the hydrocarbon tail in a triglyceride
Can be saturated or unsaturated and can also vary in length
Properties of triglycerides
Hydrophobic - there are no spare oxygen molecules for water to form hydrogen bond with
- Makes them insoluble in water
Characteristics of lipids
•Lipids contain C, H and O(Lipids have a lot less oxygen than carbohydrates)
•Lipids are non-polar molecules, so are insoluble in water
•They are soluble in organic solvents
•They are generally hydrophobic
•Building blocks are fatty acids and glycerol
•Do not form Polymers
What are the different types of lipids
Triglyceride
Phospholipids
Steroids
Hormones
Cholesterol
Waxes
What is the structure and function of a lipid?
•The function depends on the structure
•There is a wide range of lipids and each one has its own function
•General functions include : energy storage and as a metabolic water source, membrane structure, water proofing, insulation and hormones
What is the structure of fatty acids?
Consist of a long chain of carbons and hydrogens with a carboxyl group at one end
Structure of a saturated fatty acid
O H H H H H H H H H
\ | | | | | | | | |
C-C-C-C-C-C-C-C-C-C-H
/ | | | | | | | | |
O H H H H H H H H H
The hydrocarbon chain has only single bonds
Structure of unsaturated fatty acids
O H H H H H
\ | | | | | H
C-C-C-C-C-C- | H
/ | | | | C= | H
O H H H H C- | H
C- |
| C-
H | H
H
The hydrocarbon chain consists of at least one double bond
Describe the test for lipids
•Take a completely dry and grease -free test tube
• To 2cm^3 of the sample being tested, add 5 cm^3 of ethanol
• Shake the tube thoroughly to dissolve any lipid in the sample
• Add 5cm^3 of water and shake gently
• A cloudy-white colour indicates the presence of a lipid
• As a control, repeat the procedures using water instead of the sample: the final solution should remain clear
Describe the test for non-reducing sugars
•Add 2cm^3 of the food sample being tested to 2cm^3 of Benedict’s reagent in a test tube
• Place the test tube in a gently boiling water bath for five minutes. If the Benedict’s reagent doesn’t change colour (the solution remains blue), then a reducing sugar is not present
• Add another 2cm^3 of the food sample to 2cm^3 of dilute hydrochloric acid in a test tube and place the test tube in a gently boiling water bath for five minutes. The dilute hydrochloric acid will hydrolyse any disaccharide present into its constituent monosaccharides
• Slowly add some sodium hydrogencarbonate solution to the test tube in order to neutralise the hydrochloric acid (Benedict’s reagent will not work in acidic conditions.) Test with pH paper to check that the solution is alkaline
• Re-test the resulting solution by heating it with 2cm^3 of Benedict’s reagent in a gently boiling water bath for 5 minutes
• If a non-reducing sugar was present in the original sample, the Benedict’s reagent will now turn orange-brown. This is due to
the reducing sugars that were produced from the hydrolysis of the non-reducing sugar
Describe the test for sugars
•Add 2cm^3 of the food sample to be tested to a test tube. If the sample is not already in liquid form, first grind it up in water
• Add an equal volume of Benedict’s reagent
• Heat the mixture in a gently boiling water bath for five minutes
• positive result: changes from blue to an orange/brick red
Describe the test for starch
•Place 2cm^3 of the sample being tested into a test tube
• Add two drops of Iodine solution and shake or stir
• The presence of starch is indicated by a blue-black colouration
What is a monomer?
The smaller units from which larger molecules are made
What are polymers?
Molecules made from a large number of monomers joined together
What does a condensation reaction do?
Joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.
Joins monomers to make polymers
What does a hydrolysis reaction do?
a water molecule is used to break a chemical bond between two molecules
Give 3 examples of monomers.
- monosaccharides
- amino acids
- nucleotides
Give 3 examples of polymers.
- polysaccharides
- proteins
- DNA
What does a condensation reaction look like
(OH) (H) (OH) (H)
\ / \ /
( ) ( )
Monomer 1 Monomer 2
/ (O)
/—-> (H2)
Copolymers 1 and 2 /
(OH) (H)
\ /
( ) ———— ( )
(Brackets are circles)
What does a hydrolysis reaction look like?
HO——(1)—(2)—(3)—(4)—-H
\
\
How are triglycerides formed?
By the condensation of one molecule of glycerol and three molecules of fatty acid
Why are triglycerides hydrophobic?
There are no spare oxygen molecules for water to form hydrogen bonds with.
What is the structure of triglycerides?
- Three fatty acids combined with glycerol.
- High ratio of energy-storing carbon-hydrogen bonds to carbon atoms so are a very good source of energy.
- Low mass to energy ratio so good storage molecules as much energy can be stored in a small volume.
- Large, non-polar molecules so are insoluble in water so don’t affect osmosis or the water potential in cells.
What are the two polysaccharides starch are a mixture of?
Amylose
Amylopectin - branched.
Name the 3 hexose monosaccharides
- glucose
- fructose
- galactose
What is the structure of a saturated fatty acid?
- contain only single bonds
- straight chain molecules have many contact points
- higher melting point = solid at room temperature
- found in animal fats
What is the structure of an unsaturated fatty acid?
- contain double carbon bonds
- ‘kinked’ molecules have fewer contact points
- Lower melting point - liquid at room temperature
- found in plant oils
Relate the structure of triglycerides to their functions
• high energy:mass ratio = high calorific value from oxidation (energy storage)
• insoluble hydrocarbon chain = no effect on water potential of cells and used for waterproofing
• slow conductor of heat = thermal insulation
• less dense than water = buoyancy of aquatic animals
Compare phospholipids and triglycerides
• both have glycerol backbone
• both may be attached to a mixture of saturated and unsaturated fatty acids
• both contain the elements C,H,O
• Both formed by condensation reactions
Contrast phospholipids and triglycerides
Phospholipids:
• 2 fatty acids and 1 phosphate group attached
• hydrophilic head and hydrophobic tail
• used primarily in membrane formation
Triglycerides:
• 3 fatty acids attached
• entire molecule is hydrophobic
- used primarily as a storage molecule
