Chapter 1 - Biological Molecules Flashcards
What are carbohydrates?
Compounds comprising only of hydrogen, carbon and oxygen units
What type of molecule is a carbohydrate?
A polymer
Characteristics of polymers
Long, complex molecules made of chains of monomers
Examples of monomers (3)
Monosaccharides, amino acids and nucleotides
What are the monomers of carbohydrates?
Monosaccharides
Examples of monosaccharides (3)
Glucose, fructose, galactose
What type of sugar is glucose and why?
Hexose sugar - it has 6 hydrogen atoms
Glucose + glucose =
Maltose
Glucose + fructose =
Sucrose
Glucose + galactose =
Lactose
What are the two types of glucose?
Alpha - and Beta - glucose
What are isomers?
Molecules with the same molecular formula but the atoms are bonded in a different way
What is a condensation reaction?
Two monosaccharides join together to form a disaccharide and a molecule of water is produced
What bond is formed in a disaccharide?
Glycosidic
What can a hydrolysis reaction do?
Break apart polymers
How does a hydrolysis reaction work?
It breaks the glycosidic bond in a disaccharide using a water molecule to form the original monosaccharides but only under the correct conditions
What are reducing sugars?
Chemicals that readily reduce others (donate electrons) when in solution
How to test for a reducing sugar?
Add 1 cm3 sugar to test tube
Add 1 cm3 benedict’s reagent
Heat in a water bath at 70c for 4 minutes
Positive result for Benedict’s test for reducing sugar?
Goes brick red if a lot of sugar is present
How to test for a non reducing sugar?
Add 1 cm3 solution to test tube
Add 1 cm3 hydrochloric acid to hydrolyse the sugar
Add sodium hydrogen carbonate until universal indicator paper turns green
Add 1cm3 benedict’s solution
Place in a water bath at 70c for 4 minutes
non-reducing result for Benedict’s test for non-reducing sugars?
Goes brick red
When are polysaccharides formed?
When more than two monosaccharides join together in a condensation reaction
Examples of polysaccharides (3)
Starch, glycogen and cellulose
Which monomers make up cellulose?
Beta glucose
Structure of cellulose
Straight, unbranched chains of beta glucose run parallel to each other
Hydrogen bonds form between the chains
This forms microfibrils, which group to make fibres
Function of cellulose
Structural support
Which monomers make up glycogen?
Alpha glucose
Structure of glycogen
Large, branched chains of alpha glucose provide a large surface area for enzymes to act upon
Function of glycogen
Stores glucose to be released when we need it
How do you test for starch?
Add a solution of iodine dissolved in potassium iodide solution and it should change from brown to blue black
Function of starch
Plants store excess glucose as starch so it can be broken down into glucose when the plant needs energy
Advantages of starch (2)
Large so can’t fit through cell membranes to upset osmotic potential
Insoluble so doesn’t impact osmotic balance
Which monomers make up starch?
Alpha glucose
Structure of starch
Made of two alpha glucose polysaccharides:
Amylose - long, unbranched chains which coil up and make it very compact
Amylopectin - long, branched chain of glucose which provides a large surface area for enzymes to act on
What are triglycerides?
One molecule of glycerol with three fatty acid tails
What are the fatty acid tails made from?
Hydrocarbons
Are fatty acid tails hydrophilic or phobic?
Hydrophobic - they repel water
How are triglycerides produced?
A condensation reaction occurs between one fatty acid tail and the glycerol molecule, forming an ester bond and a molecule of water. This happens three times
Bonding in triglycerides
Ester