1. Biological Molecules Flashcards
Define ‘covalent bonding’
Atoms share a pair of electrons in their outer shells, resulting in the outer shells of both electrons being filled, forming a stable molecule.
Define ‘ionic bonding’
Ions with opposite charges attract one another, causing a transfer of electrons, forming an ionic bond by electrostatic attraction.
Define ‘hydrogen bonding’
The electrons are polarised. The negative region and positive region of the polarised molecule attract each other, forming a weak electrostatic bond between the two.
Define ‘monomer’
One of many small molecules that combine collectively to form a larger one known as a ‘polymer’.
Define ‘polymer’
Large molecules made up of repeating smaller molecules/monomers.
Define ‘polymerisation’
Process by which polymers are formed.
Describe the process of a condensation reaction
Chemical process in which 2 molecules combine to form a more complex one with the elimination of a simple substance, usually water.
Describe the process of hydrolysis
The breaking down of large molecules into smaller ones by the addition of water molecules.
Define metabolism
All the chemical processes that take place collectively in an organism
What is a single carbohydrate monomer called?
Monosaccharide
What is a pair of monosaccharides called?
Disaccharide
What are many monosaccharides called?
Polysaccharide
What is the general formula of monosaccharides?
(CH2O)n
What is the name of the test for reducing sugars?
Benedit’s test
Describe the Benedict’s test for reducing sugars?
-Add 2cm^3 of the food sample to be tested to a test tube. If the sample is not already in liquid, first grind it up in water.
-Add an equal vol of Benedict’s reagent.
-Heat the mixture in a gently boiling water bath for 5 mins.
If reducing sugar is present, solution turns orange-brown.
Which monosaccharides make up the disaccharide maltose?
Glucose & glucose
Which monosaccharides make up the disaccharide sucrose?
Glucose & fructose
Which monosaccharides make up the disaccharide lactose?
Glucose & galactose
What is the bond formed between 2 monosaccharides?
Glycosidic bond
What is the test for non-reducing sugars?
Benedict’s test
Describe the Benedict’s test for non-reducing sugars
- If food sample isn’t already liquid, it should be ground.
- Add 2cm^3 of the food sample to 2cm^3 of dilute hydrochloric acid in a test tube and place in a gently boiling water bath for 5 mins. The dilute hydrochloric acid will hydrolyse any disaccharide present into its constituent monosaccharides.
- Slowly add sodium hydrogencarbonate solution to the test tube in order to neutralise the hydrochloric acid. Test with pH paper that the solution is alkaline.
- Heat the resulting solution with 2cm^3 Benedict’s reagent in a water bath for 5 mins.
- If non-reducing sugar present, the Benedict’s solution will turn orange-brown.
Describe the test for starch
- Place 2cm^3 of the sample to a test tube.
- Add 2 drops of iodine solution and shake.
- Starch will turn solution blue-black.
What is starch made up of?
Chains of alpha-glucose monosaccharides linked by glycosidic bonds formed in condensation reactions.
What is the function of starch?
Energy storage in plants
How is the structure of starch adapted to its function?
- Insoluble, doesn’t affect water potential so water is not drawn into cells by osmosis.
- Large and insoluble, doesn’t diffuse out of cells.
- Compact, a lot stored in a small place.
- Hydrolysis produces alpha-glucose, easily transported and used in respiration.
- Branched, has many ends, enzymes can act simultaneously and release glucose monomers.
What is glycogen made up of?
Chains of alpha-glucose monosaccharides linked by glycosidic bonds formed in condensation reactions.
What is the main function of glycogen?
The main carbohydrate storage product of animals. Stored as granules in liver/muscles.
How is the structure of glycogen related to its function?
- Insoluble, doesn’t affect water potential so water is not drawn into cells by osmosis.
- Large and insoluble, doesn’t diffuse out of cells.
- Compact, a lot stored in a small place.
- Highly branched, enzymes can act simultaneously to form glucose- used in respiration, animals have a higher metabolic rate than plants.
What is cellulose made up of?
Made of monomers of beta-glucose, which form straight, unbranched chains.
What is the main function of cellulose?
Provides rigidity to plant cell- prevents cell from bursting as water enters by osmosis. Cellulose exerts an inward pressure, preventing any further influx of water. Makes plant cells turgid, pushing against one another, important in maintaining rigidity of stems/leaves, maximising area for photosynthesis.
How is the structure of cellulose related to its function of providing support and rigidity?
- Cellulose made of beta-glucose and form long, unbranched chains.
- These cellulose molecular chains run parallel to each other, cross linked by hydrogen bonds to add collective strength.
- Cellulose molecules grouped together to form microfibrils, which in turn are grouped to form fibres, all of which providing more strength.
What are the two main groups of lipids?
Triglycerides and phospholipids