B1 Biological Molecules

• What are monomers?

  Monomers are small units that are the components of larger molecules.
• Give examples of monomers.

  Examples of monomers include monosaccharides, amino acids, and nucleotides.
• What are polymers?

  Polymers are molecules made from many monomers joined together.
• How are monomers joined together?

  Monomers are joined by a chemical bond in a condensation reaction.
• What happens during hydrolysis?

  Hydrolysis is when water is added to break a chemical bond between two molecules.
• What elements do carbohydrates consist of?

  Carbohydrates consist only of carbon, hydrogen, and oxygen.
• What is a monosaccharide?

  A monosaccharide is a single monomer of carbohydrates.
• What is a disaccharide?

  A disaccharide is formed from a pair of monosaccharides.
• What is a polysaccharide?

  A polysaccharide is formed by combining many monosaccharides.
• What type of bond joins monosaccharides in carbohydrates?

  Monosaccharides are joined by a glycosidic bond formed in a condensation reaction.

  
• What is glucose classified as?

  Glucose is classified as a monosaccharide.
• How many carbon atoms are in a glucose molecule?


  Glucose contains six carbon atoms in each molecule.
• What are the two isomers of glucose?

  The two isomers of glucose are alpha and beta glucose.
• What is the general formula for common monosaccharides?

  The general formula for common monosaccharides is (CH₂O)_n where n can be any number from three to seven.
• How is maltose formed?

  Maltose is formed by the condensation of two glucose molecules.

  
• How is sucrose formed?

  Sucrose is formed by the condensation of glucose and fructose.
• How is lactose formed?

  Lactose is formed by the condensation of glucose and galactose.

  
• What are glycogen and starch formed from?

  Glycogen and starch are formed from many glucose units joined together.
• What is the main energy storage molecule in animals?

  Glycogen is the main energy storage molecule in animals.
• How is glycogen structured?

  Glycogen is formed from many molecules of alpha glucose joined by 1,4 and 1,6 glycosidic bonds.
• Why does glycogen have many side branches?

  Glycogen has many side branches allowing energy to be released quickly as enzymes can act simultaneously on these branches.
• What is the function of starch in plants?

  Starch stores energy in plants.
• What are the two polysaccharides that make up starch?

  Starch is a mixture of amylose and amylopectin.
• What is amylose?

  Amylose is an unbranched chain of glucose molecules joined by 1,4 glycosidic bonds.
• What is amylopectin?

  Amylopectin is a branched chain of glucose molecules joined by 1,4 and 1,6 glycosidic bonds.
• What are the key properties of starch?

  Starch is insoluble, compact, and releases alpha glucose when hydrolyzed.
• What is cellulose composed of?

  Cellulose is composed of long, unbranched chains of beta glucose joined by glycosidic bonds.
• What are microfibrils?

  Microfibrils are strong threads made of long cellulose chains running parallel to one another.
• What is the role of cellulose in plant cell walls?

  Cellulose stops the cell wall from bursting under osmotic pressure.
• How does cellulose help plant cells stay turgid?

  Cellulose exerts inward pressure that stops the influx of water, keeping cells turgid and rigid.
• What reagent can be used to test for reducing sugars?

  Benedict’s reagent can be used to test for the presence of reducing sugars.
• What are reducing sugars?

  Reducing sugars are sugars that can donate an electron to Benedict’s reagent.
• What happens when a reducing sugar is added to Benedict’s reagent and heated?

  It forms an insoluble red precipitate (copper (I) oxide).
• What is the procedure for the Benedict's Test for reducing sugars?

  1. Add 2cm³ of the food sample to be tested (liquid form).
  2. Add 2cm³ of Benedict’s reagent.
  3. Heat gently in a water bath for five minutes.
  4. If the solution turns brick red (orange-brown), a reducing sugar is present.
• How can you test for non-reducing sugars?

  Non-reducing sugars can be tested by hydrolyzing them into monosaccharides first.
• What is the procedure for testing non-reducing sugars using Benedict's Test?

  1. Add 2cm³ of food sample to 2cm³ of Benedict’s reagent and heat.
  2. If no color change occurs, add 2cm³ of dilute hydrochloric acid and heat.
  3. Neutralize with sodium hydrogencarbonate.
  4. Retest with Benedict’s reagent.
  5. A color change to brick red indicates a non-reducing sugar is present.
• What is the chemical test for starch?

  The chemical test for starch is iodine/potassium iodide.
• What color change indicates the presence of starch?

  If the solution turns blue/black from orange-brown, starch is present.
• What are lipids made of?

  Lipids are made of carbon, hydrogen, and oxygen.
• What are the main types of lipids?

  The main types of lipids are triglycerides and phospholipids.