3.1.2 Carbohydrates

• Examples of monosaccarides of carbohydrates?

  
  

  Glucose, Fructose, Galactose 
• Starch 

  A polysaccharide found in plant cells made up of alpha-glucose - comprised of amylose (alpha-1,4 glycosidic bonds) and amylopectin (alpha-1,4- and alpha-1,6-glycosidic bonds).
• Polysaccharide 

  Made of many sugar units that are formed by a condensation reaction. Monosaccharides are joined by a glycosidic bond.
• Non-reducing sugar

  A sugar which cannot serve as a reducing agent.An example is sucrose.
• Isomer 

  Two or more compounds with the same formula but a different arrangement of atoms in the molecule and therefore different properties.
• Reducing sugar

  A sugar that serves as a reducing agent. All monosaccharides are reducing sugars along with some disaccharides.
• Hydrogen Bond

  Chemical bond formed between the positive charge on a hydrogen atom and the negative charge on another atom of an adjacent molecule.

  Often between negative oxygen and positive hydrogen atoms.
• Hexose sugar

  A sugar made up of 6 carbons.
• Glycosidic bond

  Bond between sugar molecules in disaccharides and polysaccharides.
• Glycogen

  A highly branched polysaccharide made up of alpha-glucose found in animal cells (alpha-1,4- and alpha-1,6-glycosidic bonds).
• Glucose

  C6H12O6 - a single sugar which is used in respiration.
• Disaccharide 

  Made up of two sugar units that are formed by a condensation reaction.Monosaccharides are joined by a glycosidic bond.
• Cellulose 

  A polysaccharide made up of beta-glucose found in plant cells (beta-1,4-glycosidic bonds).
• Beta Glucose 

  An isomer of glucose that can bond together to form cellulose.
• Alpha glucose 

  An isomer of glucose that can bond together to form starch or glycogen.
• What is the structure of cellulose?

  • Long unbranched molecule formed from the condensation of b glucose joined by 1-4 glycosidic bonds.
  • Cellulose chains are linked by hydrogen bonds forming thicker fibres called microfibrils (strong but flexible)
  • To form straight chain the alternate glucose molecules have to rotate.
• What is cellulose?

  • major structural component of cell walls
  • providing support 
  • allowing cells to become turgid
• Describe the difference between Amylose and Amylopectin: (AMYLOSE)

  • Amylose
  • is a long unbranched molecule which forms a coil/spring shape. - a glucose molecules linked by a 1-4 glycosidic bond. - amylose chains forms a helix held together bonds.  - coiling - compact, so can be stored in a smaller space.
• • Describe the difference between Amylose and Amylopectin: (AMYLOPECTIN)
  • Amylopectin
  • is a long branched molecule (similar to glycogen).- a glucose molecules linked by a 1-4 glycosidic bond with side chains (branches) linked by a 1-6 glycosidic bond.- branched molecule - increase surface area for enzymes to hydrolyse glycosidic bonds allowing glucose to be released quickly.
• How is starch formed?

  Made from a mixture of 2 types of polymer - amylose and amylopectin, both of which are formed from condensation of a glucose.
• When can starch be hydrolysed to release glucose for respiration?

  During low levels of photosynthesis.
• Definition of insoluble:

  Does not affect water potential.
• What is starch?

  • Storage form of carbohydrates (excess glucose) found in plants.
  • Insoluble
  • Can be hydrolysed to release glucose for respiration.
• What is the structure of glycogen?

  Branched molecule - increase surface area for enzymes to hydrolyse glycosidic bonds allowing glucose to be released quickly.

  Formed by the condensation of a glucose molecules bonded to each other by a 1-4 glycosidic bonds with side chains bonded via a 1-6 glycosidic bonds.
• What is glycogen?

  • Storage form of carbohydrates (excess glucose) in mammals found in large quantities in liver and muscle cells.
  • Energy store that can be hydrolysed to release glucose quickly when respiration demands increase.
  • Compact molecule (easier to store).
• State which is Alpha/Beta glucose from glycogen, starch and cellulose:

  • Alpha glucose - Glycogen & Starch
  • Beta glucose - Cellulose
• What are polysaccharides?

  Polysaccharides are polymers formed from multiple monosaccharides joined together by glycosidic bonds during condensation reactions.
• State if the disaccharide is an example of reducing/non-reducing sugar: (Maltose/Sucrose/Lactose)

  • Maltose - reducing sugar,
  • Sucrose - non-reducing sugar,
  • Lactose - reducing sugar.
• Which monosaccharides bond together to form the following disaccharides? (Maltose,Sucrose and Lactose)

  
  

  • Maltose - glucose molecules,
  • Sucrose - glucose and fructose molecules,
  • Lactose - glucose and galactose molecules.
• What are disaccharides (and what bond is formed)?

  Disaccharides are formed when 2 monosaccharides bond together in a condensation reaction.

  They form a glycosidic bond with water being produced as a by-product.
• What is an isomer?

  Isomer : compunds with the same formula but a different arrangement of atoms.
• What are carbohydrates, and what elements are they composed of?

  Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen in a ratio of 1:2:1.
• What are the two isomers of glucose?

  Alpha Glucose and Beta Glucose
• Name three common monosaccharides:

  Glucose (C6H12O6), Fructose (C6H12O6), and Galactose (C6H12O6).
• What is the main function of monosaccharides in living organisms?

  Monosaccharides serve as a primary source of energy for cellular processes.
• Define disaccharide and give an example.

  A disaccharide is a carbohydrate formed by the covalent bonding of two monosaccharide units. Example: Sucrose (glucose + fructose).
• Describe how a disaccharide is formed.

  Disaccharides are formed through a condensation reaction where a molecule of water is removed as two monosaccharides join together.
• Explain the structural difference between starch and cellulose.

  Starch is composed of alpha-glucose molecules and is branched or unbranched, whereas cellulose is composed of beta-glucose molecules and forms straight chains.
• What is the role of cellulose in plant cells?

  Cellulose provides structural support and rigidity to plant cell walls, allowing them to maintain their shape and withstand mechanical stress.
• Describe the process of hydrolysis as it relates to carbohydrates.

  Hydrolysis is the chemical process by which a molecule of water is added to break a covalent bond between monosaccharide units in a polysaccharide, resulting in the breakdown of the polysaccharide into its constituent monosaccharides.