Carbohydrates and Lipids Flashcards
What is a condensation reaction?
The formation of polymers through polymerisation which produce water
What is a hydrolysis reaction?
Polymers that are broken down with the addition of water
What is metabolism?
All chemical processes that take place in living organisms
What is a monomer?
Smaller units from which larger molecules are made
-e.g- Monosaccharide, Amino Acids, Nucleotides
What is a polymer?
Molecules made from a large number for monomers joined together
What is the basic monomer of carbohydrates?
Monosaccharide
What is the product formed from combining 2/multiple monosaccharides?
Disaccharide
Polysaccharide
What are common monosaccharides?
Glucose
Galactose
Fructose
What does a condensation reaction between two monosaccharides form?
Glycosidic bond
How are these disaccharide formed:
Maltose
Sucrose
Lactose
Maltose - Condensation reaction between two glucose molecules
Sucrose - Condensation reaction between a fructose and glucose molecule
Lactose - Condensation reaction between a galactose and glucose molecule
What is the test for reducing sugars? + What is reduction?
Reduction - chemical reaction which involves the gain of electrons/hydrogen
A reducing sugar can donate electrons to another chemical
When a reducing sugar is heated with Benedict’s Solution, the solution will turn a brick red precipitate of copper oxide
How is the reducing sugars test carried out?
- 2cm^3 of food solution in a test tube (in liquid form)
- Add an equal volume of Benedict’s Solution
- Heat solution for 5 minutes
What is the test for non-reducing sugars?
+ give examples of non reducing sugars
Some disaccharides are non-reducing sugars (maltose)
Benedict’s test is used but they do not change the colour of Benedict’s Solution
when heated with it. As a result, the non-reducing sugar should be hydrolysed into monosaccharides first.
How is the test for non-reducing sugars carried out?
- Sample must be in liquid form
- Add 2cm^3 of food sample and 2cm^3 of Benedict’s solution in test tube
- Heat for 5 minutes, if it does not change colour then a reducing sugar is not present
- Add 2cm^3 of food sample to dilute hydrochloric acid and heat test tube for 5 minutes (this hydrolyses disaccharide into its monosaccharides)
- Add hydrogencarbonate to test tube to neutralise hydrochloric acid + test pH of solution to check if it is alkaline
- Re-test the food solution by adding same volume with Benedict’s solution + heating it
- If a non-reducing sugar was present, solution will turn a brick red
How are polysaccharides formed and what are their properties?
Formed by combining many monosaccharides, joined by glycosidic bonds from condensation reactions
Properties:
- Very large -> insoluble therefore good for storage
- (Cellulose) -> gives structural support in plants
When hydrolysed they are broken down into monosaccharides or disaccharides
What is the test for starch?
Iodine is added to starch solution, if starch is present, solution will change from yellow to blue-black
How is the test for starch carried out?
- Add 2cm^3 of sample into a test tube
- Add two drops iodine solution and shake/stir
- Solution will turn blue-black if starch is present
What is the structure of starch and why is it important?
Starch is made up of chains of alpha glucose monosaccharides joined by glycosidic bonds, formed by condensation reactions
-may be branched or unbranched (unbranched chains are tightly coiled to become compact)
What is the role of starch? and how does it structure help this?
-Mainly energy storage
Structure:
- Insoluble -> does not affect water potential -> water does not move into cell by osmosis
- Large/insoluble -> does not diffuse out of cells
- Compact -> a lot can be stored in a small space
- Forms alpha glucose when hydrolysed -> easily transported and used in respiration
- Branched form has many ends -> easily acted on by enzymes to readily/rapidly release glucose monomers
What is the role of starch? and how does it structure help this?
-Mainly energy storage
Structure:
- Insoluble -> does not affect water potential -> water does not move into cell by osmosis
- Large/insoluble -> does not diffuse out of cells
- Compact -> a lot can be stored in a small space
- Forms alpha glucose when hydrolysed -> easily transported and used in respiration
- Branched form has many ends -> easily acted on by enzymes to readily/rapidly release glucose monomers
What is the difference between starch and glycogen?
Glycogen:
Found in animal cells only
Shorter chains and more branched than starch
Stored as small granules in muscles + liver
How does the structure of glycogen help its role?
Role: storage
- Insoluble -> does not affect water potential -> water does not move into cell by osmosis
- Large/insoluble -> does not diffuse out of cells
- Compact -> a lot can be stored in a small space
- More highly branched than starch -> more ends that can be acted on simultaneously by enzymes + is rapidly broken down into glucose monomers for respiration (as animals have a higher metabolic rate than plants due to being more active they need glucose more readily available)
What is the structure of cellulose?
- Made of monomers of beta glucose
- Straight, unbranched chains
- Chains run parallel to each other and are cross linked by hydrogen bonds (for strength)
- Grouped to form microfibrils, forming fibres for strength
What are the differences/similarities between starch and cellulose?
Similarities
- Polysaccharides
- Made from glucose monomers
- Insoluble
- In plants
Differences
- Starch is made of alpha glucose
- Cellulose is made of beta glucose
- Starch is the main energy store in plants
- Cellulose forms microfibrils for structural support
What are the main properties of lipids?
+ The two main groups of lipids
- Contain hydrogen, carbon and oxygen
- Proportion of oxygen to carbon and hydrogen is smaller compared to carbohydrates
- Insoluble in water
- Soluble in organic solvents like alcohol
- Main group of lipids is triglycerides + phospholipids
What are the roles of lipids?
- In cell membranes -> allow flexibility and transfer of lipid soluble substances
- Source of energy -> when oxidised release twice the energy that a carbohydrate would as well as water
- Waterproofing -> Plants/insects have waxy cuticles to limit water loos
- Insulation -> Slow conductors of heat and retain body heat
- Protection -> Fat is stored around delicate organs
How are triglycerides formed?
Condensation reaction of one molecule of glycerol and three fatty acids
What is the difference between a saturated and unsaturated fatty acid?
Saturated - no carbon-carbon double bonds (all carbon atoms are linked to all H atoms)
Unsaturated:
Poly-unsaturated: More than one double bond between carbon atoms
Mono-unsaturated: One double bond between carbon atoms
How is the structure of triglycerides related to its properties?
- High ratio of energy-strong carbon-hydrogen bonds to carbon atoms -> good source of energy
- Low mass to energy ratio
- > good for storage
- Large and insoluble -> do not affect osmosis/water potential
- High ratio of hydrogen to oxygen atoms -> release water when oxidised (important source of water)
What is the difference between a phospholipid and a triglyceride?
Phospholipids have the same structure as triglycerides but one fatty acid is replaced by a phosphate group
What is the structure of a phospholipid?
- Hydrophilic head
- Hydrophobic tail
The phosphate group attracts water where as fatty acids repel water
What does polar mean?
Molecules with two ends that behave differently
How is the structure of phospholipids related to its properties?
- Polar -> In aqueous environment, form a bilayer in membranes so a hydrophobic barrier is formed between outside and inside of the cell
- Hydrophilic heads -> hold at the surface of membrane
- Phospholipid structure -> Can form glycolipids when combined with carbohydrates (important for cell recognition)
What is the test for lipids ?
Emulsion test:
- 2cm^3 of sample with 5cm ^3 of ethanol
- Shake test tube to dissolve any lipid in sample
- Add 5cm^3 of water
- Milky-white solution will form if lipid is present
