Key questions

• What is a monomer?


  Smaller units from which large molecules are made
• What is a polymer?


  Molecules made from many monomers joined together
• Name examples of monomers


  Monosaccharide; amino acids, nucleotides.
• What reaction joins monomers together?

  A condensation reaction.
• What happens in a condensation reaction?


  Two monomers are bonded together, water is formed as a by product.
• What reaction takes place when biological molecules are separated?

  A hydrolysis reaction.
• What happens in a hydrolysis reaction?

  Two monomers are separated by breaking a bond. Water is used up in this reaction
• What are larger complex carbohydrates made from?

  Monosaccharides
• What are the common monosaccharides?

  Glucose, galactose and fructose
• What reaction forms the bond between two monosaccharides?

  A condensation reaction.
• What bond forms when monosaccharides join?

  A glycosidic bond.
• What is a disaccharide?

  A molecule made from 2 monosaccharides
• How is a disaccharide formed?

  A condensation reaction between 2 monosaccharides
• What is maltose and what is it formed from?

  A disaccharide formed from the consation reaction between 2 glucose molecules.
• What is sucrose and what is it formed from?

  A disaccharide formed from the consation reaction between a glucose and a fructose molecule.
• What is lactose and what is it formed from?

  A disaccharide formed from the condensation reaction between glucose and a galactose molecule.
• What is an isomer?

  Molecules where the formula stays the same, but the structure is slightly different.
• What are the isomers of glucose?

  Alpha (α) and beta (β) glucose.
• What is the difference between alpha and beta glucose?

  The OH group on carbon 1 of α-glucose is below the ring, on β-glucose it is above.

  Alpha Below Beta Above (ABBA)
• Draw Alpha Glucose and Beta Glucose
• What is a polysaccharide?

  A complex carbohydrate formed from the condensation reactions of many monosaccharides.
• What is glycogen and what is it made of?

  A complex carbohydrate, a polysaccharide made from multiple α-glucose molecules. Glucose storage molecule in animals.
• What is starch and what is it formed from?

  A complex carbohydrate, a polysaccharide made from multiple α-glucose molecules.
• What is cellulose?


  A complex carbohydrate, a polysaccharide made from multiple β-glucose molecules.
• What is the purpose of glycogen?

  It is an insoluble store of glucose in animals.
• What is the purpose of starch?

  It is an insoluble store of glucose in plants, and an energy source for animals
• What is the purpose of cellulose?

  It is an insoluble structural molecule for plants, especially for their cell walls.
• What are the two molecules that together make up starch?

  Amylose - a helical molecule

  Amylopectin - a branched (and helical) molecule

  All starches contain both of these but proportions can vary in different plants.
• What is the structure of glycogen?

  Heavily branched polymer of α-glucose molecules.

  Linked at 1-4 glycosidic bonds. Branched with 1-6 glycosidic bonds.
• How is glycogen's structure related to its function

  Insoluble so no osmosis

  Insoluble so does not diffuse out of cells

  Compact due to helical structure so lots of glucose stored in small space

  Highly branched so many ends can be simultaneously hydrolysed by enzymes
• What is the structure of starch?

  Lightly branched polymer of α-glucose molecules.

  Linked at 1-4 glycosidic bonds. Branched with 1-6 glycosidic bonds.
• How is starch's structure related to its function

  Insoluble so doesn't affect water potential and no osmosis

  Large and insoluble so doesn’t diffuse out of cells

  Compact due to helical structure so lots of glucose stored in small space

  Hydrolysed to form α-glucose so easily transported and used for respiration

  Branched so more enzymes can hydrolyse bonds simultaneously
• What is the basic structure of cellulose?

  Straight chains of β-glucose molecules. Bonded with 1,4 glycosidic bonds.
• How are the monosaccharides in cellulose arranged?

  Alternative β-glucose molecules are turned upside down
• How is cellulose's structure related to its function

  Made up of β-glucose so form long, straight unbranched chains/chains run parallel to each other and are crossed linked by hydrogen bonds which add collective strength/molecules are grouped to form microfibrils which are also grouped to form fibres which provides more strength
• Based on the arrangement of cellulose molecules, explain why cell walls provide strength and support to plant cells.

  Cellulose molecules form hydrogen bonds with each other to make microfibrils

  - microfibrils join to make macrofibrils

  - macrofibrils join to make fibres

  - fibres are insoluble and tough
• What are examples of reducing sugars?

  All monsaccharides - glucose, galactose, fructose. Also some disaccharides - e.g. lactose
• What is an example of a non-reducing sugars?

  Sucrose
• What does the Benedict's test test for?

  Reducing sugar
• What is the test for reducing sugars

  Add equal volumes of the sample and Benedict's reagent, then gently heat for 5 minutes and if reducing sugar present then colour from blue to red/green/orange