B3 - Biological Molecules Flashcards
What are monomers and polymers?
Monomers are the building blocks of more complex molecules, called polymers. Polymers consist of repeating molecular units.
What are natural polymers?
Proteins, carbohydrates and lipids are described as natural polymers or biopolymers because they are built up from smaller molecules into much larger structures by living cells.
What are protein molecules made up from?
Protein molecules are made up from long chains of amino acids.
Why does the chain of amino acids in a protein have a special shape?
Due to cross-linkages
What happens to the protein when subjected to high temperatures?
The protein loses its shape and becomes denatured because these cross-linkages are broken and so the protein loses its original properties.
What do all carbohydrates contain?
carbon, hydrogen, and oxygen.
What are the types of carbohydrates?
Monosaccharides, disaccharides, polysaccharides
What is a monosaccharide?
Sugars with a single carbon ring, e.g. glucose and fructose
What is a polysaccharide?
carbohydrates that have many glucose molecules joined together. e.g. strach
What is a disaccharide?
sugars with 2 carbon rings, e.g. maltose and sucrose.
What are lipids?
LIpids are fats and oils that contain carbon, hydrogen, and oxygen.
What is a molecule of fat made up from?
A molecule of fat is made of 3 molecules of an organic acid called fatty acid, combined with 1 molecule of glycerol.
What do lipids form?
LIpids form part of the cell membrane and the internal membranes of the cell such as the nuclear membrane.
What are the steps to Benedict’s test for glucose?
- Add 1cm of Benedict’s solution to 1cm of food or glucose in a test tube.
- Heat the mixture in a water bath without boiling.
In Benedict’s test for glucose, how do we know that glucose is present?
A brick-red colour is positive for glucose. With sucrose, a negative test remains a blue colour
What are the steps for the test for sucrose?
- Add 10 drops of 2M HCl to 1cm of food or sucrose in a test tube.
- Heat gently in a water bath without boiling.
- Add 0.5 cm of Benedict’s solution and heat gently without boiling in a waterbath.
In the test for sucrose, how do we know that sucrose is present?
The mixture should turn blue.
How do you test for starch?
Add 2 drops of iodine solution to 1cm solution of food or starch.
In the test for starch, how do we know starch is present?
A black/blue colour indicates the presence of starch.
What are the steps to the ethanol emulsion test for fats and oils?
- Dissolve substances to be tested in ethanol (2ml).
- Allow to settle for 2 minutes.
- Empty any clear liquid into a test tube containing 2ml of distilled water.
In the ethanol emulsion test, how do we know fats and oils are present?
A milky emulsion shows fats are present, if the mixture remains clear, no fats are present.
How is water important as a solvent?
- Dissolved substances can be easily transported around organisms
- Digested food molecules are moved to cells all over the body
- Toxic substances and substances in excess of requirements dissolve in water which makes them easy to remove from the body.
- Water is also an important part of the cytoplasm and plays a role in ensuring metabolic reactions can happen necessary in cells.
What are the steps to the biuret test for proteins?
- To a 1 cm solution of food in a test tube, add an equal amount of 5% NaOH.
- Dribble a small amount of 1% CuSO4 solution down the side of the test tube.
What indicates the presence of protein in the biuret test for proteins?
A purple ring at the interface indicates the presence of protein.
