Biomolecules 2

• Digestible disaccharides in food:

  Sucrose, lactose & maltose
• What is sucrose made of?


  glucose & fructose
• What is lactose made of?


  galactose & glucose
• What is maltose made of?


  Glucose x2
• What are carb. stores controlled by?


  insulin & glucagon
• Why can't excess carbs be the basis of weight gain?


  Storage capacity is limited & controlled
• Are carbs a long or short term fuel source?


  Short term
• Examples of structural sugars:

  Deoxyribose & ribose
• What is the general formula of simple sugars?

  (CH2O)n n= 3, 4, 5 or 6

  Simple sugars have 2 or more OH groups

  either have aldehyde group (aldoses) or ketone group (ketoses)
• What are hexose derivatives?


  OH replaced with another group

  E.g, glucosamine used for joint health in supplements
• What is a glycan?


  Carbohydrate polysaccharide
• What is a glucan?


  Glucose polysaccharide
• Homopolysaccharides:


  Polymers of single type of sugar
• Heteropolysaccharides:


  Polymers of different sugars (2 monomer types)
• Structure of glycogen:


  Alpha glucose chains

  More compact than starch

  Similar to amylopectin but more branched

  Degradation from non-reducing ends (no free C=O)
• Where is glycogen stored?

  Liver & skeletal muscle

  Also Uterus & Kidney

  (Stores glucose in animal cells)
• Structure of starch:

  Homopolysaccharide- alpha glucose

  Amylose (unbranched)

  Amylopectin (branched)
• Glycogen storage diseases (Type IB):


  Storage in liver & other organs increased

  Symptoms: tiredness, fatigue, liver failure
• Cellulose structure:


  Tough, fibrous glucose homopolysaccharide in plant cell walls.

  Glucose units linked by b1-4 glycosidic links
• What are chitins?


  Homopolysaccharide composed of N-acetylglucosamine units.

  In exoskeleton of insects & crustaceans.
• What are Dextrans?


  Extensively branched sticky glucose polymers synthesised by bacteria & yeast. Main component of dental plaque.
• What are proteoglycans?


  Proteins on cell surface or in extracellular membrane- contain GAG chains attached to serine residues.
• What are glycoproteins?


  On cell membrane or ECM. Contain oligosaccharides covalently linked to serine, threonine (O-linked) or asparagine residues (N-linked).
• What are glycolipids?


  Plasma membrane lipids covalently linked to oligosaccharides- found on extracellular surface
• What are glycosaminoglycans?


  Heteropolysaccharide polymers of repeating disaccharides of amino sugars & other sugars.

  Link to core proteins to form proteoglycans.
• What are GAGs important for?


  Cell hydration & providing structural framework.
• Where are GAGs found?


  ECM & cell surfaces
• What is a major constituent of connective tissues?

  GAGs & proteoglycans
• Describe the extracellular membrane:


  Amorphous & cements cells together.

  Comprised of proteins (e.g, collagen & elastin) & heteropolysaccharides (glycosaminoglycans (GAGs))
• What is important for making GAGs & glycoproteins?


  Glucose amino sugars
• Examples of GAGs:

  • hyaluronic acid (HA)
  • Chondroitin sulphate
  • heparan sulphate
• What does HA & other GAGs do?

  Help form hydrated gels (e.g, HA in synovial fluid), provide viscosity, lubrication, adhesiveness, tensile strength & elasticity.
• Primary structure of a protein:


  Amino acid chains covalently linked by peptide bonds.
• Functions of proteins:

  Enzymes, structural, channel/carrier & receptors
• How many amino acids makes a polypeptide?


  3 or more
• Examples of simple proteins:

  • Collagen- 3 strands of collagen helically linked ( alpha helix)
  • alpha keratin (in nails)
  • beta keratin (in reptilian scales)
• Protein synthesis:


  Unique sequence of amino acids controlled genetically by cell
• What are simple proteins?


  Consisting of only amino acids
• What are conjugated proteins?


  Proteins with amino acid sequence with prosthetic groups attached. E.g, hb.
• Quaternary structure of proteins:


  Arrangement of subunits in a multi-subunit protein.