Biological molecules - Carbohydrates Flashcards
What is a monomer?
A small unit which is a component of a larger molecule.
What is a polymer?
A molecule made from a large number of monomers joined together.
Give examples of monomers.
Glucose, amino acids and nucleotides.
What is a condensation reaction?
A reaction that joins two molecules together in a chemical bond that involves the elimination of one molecule of water.
What is a hydrolysis reaction?
A reaction that breaks the chemical bond between two molecules, using a water molecule.
What is a monosaccharide?
A monomer from which carbohydrates are made.
Give three common monosaccharides.
Glucose, galactose and fructose.
What are the isomers of glucose, and how many carbons has it got?
Glucose has 6 carbons and has isomers called alpha and beta glucose.
What is a disaccharide?
A molecule made of two monosaccharides joined together by glycosidic bonds in a condensation reaction.
Which monosaccharides form maltose?
Two alpha glucose molecules.
Which monosaccharides form sucrose?
Alpha glucose and fructose.
Which monosaccharides form lactose.
Alpha glucose and lactose.
What are polysaccharides?
Molecules made up of lots of units of glucose joined together by glycosidic bonds.
What is glycogen?
It is the main energy storage molecule for animals and is formed from many molecules of alpha glucose joined together by 1,4 and 1,6 glycosidic bonds.
Why is glycogen ideal as an energy storage molecule.
- It has a large number of side branches meaning that energy can be released quickly as enzymes can act simultaneously on these branches.
- It is relatively large but compact, maximising the amount of energy it can store.
- It is insoluble so it won’t affect the water potential of cells and can’t diffuse out of cells.
What is cellulose?
A component of cell walls in plants that is composed of long, unbranched chains of beta glucose, which are joined by glycosidic bonds.
What are microfibrils?
Strong threads which are made of long cellulose chains running parallel to each other. These are joined together by hydrogen bonds forming strong cross linkages.
What is the function of cellulose in plant cell walls?
Cellulose stops the cell wall from bursting under osmotic pressure. This is because it exerts inward pressure which stops the influx of water. This means that cells stay turgid and rigid, helping to maximise surface area of plants for photosynthesis.
What are the polysaccharides in starch?
Amylose and amylopectin.
What is the structure of amylose?
It is an unbranched chain of glucose molecules joined by 1,4 glycosidic bonds, and as a result it is coiled and compact, meaning it can store a lot of energy.
What is the structure of amylopectin?
It is a branched chain of glucose molecules joined by 1,4 and 1,6 glycosidic bonds.It has many side branches which can be acted on by enzymes.
Why is starch ideal as a storage molecule?
- It is insoluble so will not affect cell water potential
- It is compact so a lot of energy can be stored in a small space.
- When it is hydrolysed the released alpha glucose can be transported easily.
