HND 213 summary

• Carbohydrate


  The term carbohydrate often means any food that is particularly rich in the complex carbohydrate starch (such as cereals, bread, and pasta) or simple carbohydrates, such as sugar (found in candy, jams, and desserts)
• Composition of carbohydrates


  An organic compound with the empirical formula Cm(H2O)n; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 (as in water)

  
• Functions of carbohydrates


  • Monosaccharides are a fuel for cellular metabolism
  • Monosaccharides are used in several biosynthesis reactions
  • Monosaccharides may be converted into space-saving polysaccharides, such as glyocogen and starch. These molecules provide stored energy for plant and animal cells
  • Carbohydrates are used to form structural elements, such as chitin in animals and cellulose in plants
  • The 5-carbon monosaccharide ribose is an important component of coenzymes (e.g., ATP, FAD, and NAD) and the backbone of the genetic molecule known as RNA. The related deoxyribose is a component of DNA
  • Saccharides and their derivatives include many other important biomolecules that play key roles in the immune system, fertilization, preventing pathogenesis, blood clotting, and development
• Classification of carbohydrates


  • Monosaccharides (e.g glucose, fructose, galactose)
  • Disaccharides (sucrose, lactose)
  • Oligosaccharides
  • Polysaccharides (chitin, cellulose)
• Sugars


  The monosaccharides and disaccharides, which are smaller (lower molecular weight) carbohydrates, are commonly referred to as sugars
• Saccharide


  The word saccharide comes from the Greek word σάκχαρον (sákkharon), meaning "sugar"
• Characteristics used to classify monosaccharides


  • Number of carbon atoms in the molecule
  • Location of the carbonyl group
  • The chirality of the carbohydrate

  
• Aldose


  Monosaccharide in which the carbonyl group is an aldehyde

  
• Ketose


  Monosaccharide in which the carbonyl group is a ketone
• Types of monosaccharides by number of carbon atoms

  • Triose - monosaccharide with 3 carbon atoms
  • Tetrose - monosaccharide with 4 carbon atoms
  • Pentose - monosaccharide with 5 carbon atoms
  • Hexose - monosaccharide with 6 carbon atoms
• Types of monosaccharides by carbonyl group location

  • Aldohexose - 6-carbon aldehyde (e.g., glucose)
  • Aldopentose - 5-carbon aldehyde (e.g., ribose)
  • Ketohexose - 6-carbon hexose (e.g., fructose)

  
• Glucose


  An aldohexose with the formula (C·H2O)6
• Glucose can exist in both a straightchain and ring form
• Hemiacetal and hemiketal


  The aldehyde or ketone group of a straight-chain monosaccharide will react reversibly with a hydroxyl group on a different carbon atom to form a hemiacetal or hemiketal, forming a heterocyclic ring with an oxygen bridge between two carbon atoms

  
• Furanose and pyranose


  Rings with five and six atoms are called furanose and pyranose forms, respectively, and exist in equilibrium with the straight-chain form

  
• Sucrose


  A common disaccharide composed of two monosaccharides: D-glucose and D-fructose
• Amylose


  A linear polymer of glucose mainly linked with α(1→4) bonds. It can be made of several thousands of glucose units. It is one of the two components of starch, the other being amylopectin

  
• Alpha and beta anomers of glucose


  The hydroxyl group (red or green) on the anomeric carbon is either on the opposite sides (α), or the same side (β) relative to the CH2OH group bound to carbon 5
• Starch gelatinization and pasting, gelation, and uglification

  1. Raw, uncooked starch granules heated in water

  2. Swelling is evident

  3. Loss of amylose from the granules

  4. Some granules have collapsed

  5. Gelatinization and pasting are complete

  6. Cooling occurs

  7. Starch gel forms

  8. Water of syneresis is squeezed out

  9. Ugly texture due to syneresis
• Glycolysis


  The metabolic pathway in which glucose is converted into pyruvate

  
• Lipid


  A fat-soluble molecule that is insoluble in water but soluble in at least one organic solvent
• Examples of common lipids

  • Butter
  • Vegetable oil
  • Cholesterol and other steroids
  • Waxes
  • Phospholipids
  • Fat-soluble vitamins
• Functions of lipids


  • Energy storage
  • Signaling molecules (e.g., steroid hormones)
  • Structural component of cell membranes
• Triglycerides


  The most commonly occurring class of lipids, consisting of a glycerol backbone bonded to three fatty acids

  
• Phospholipids


  The second most abundant class of lipids, found in animal and plant cell membranes, containing glycerol, fatty acids, phosphoric acid, and a low-molecular-weight alcohol
• Types of fatty acids by saturation

  • Saturated
  • Unsaturated
• Types of fatty acids by length

  • Short-chain (fewer than 6 carbons)
  • Medium-chain (6-12 carbons)
  • Long-chain (longer than 12 carbons)
  • Very-long-chain (longer than 22 carbons)
• Cis and trans configuration of unsaturated fatty acids

  Cis configuration means adjacent hydrogen atoms are on the same side of the double bond, causing the chain to bend. Trans configuration means adjacent hydrogen atoms are on opposite sides of the double bond, resulting in a straighter chain.
• Cis configuration


  Adjacent hydrogen atoms are on the same side of the double bond
• Trans configuration


  The next two hydrogen atoms are bound to opposite sides of the double bond
• In most naturally occurring unsaturated fatty acids, each double bond has three n carbon atoms after it, for some n, and all are cis bonds

  
• Most fatty acids in the trans configuration (trans fats) are not found in nature and are the result of human processing (e.g., hydrogenation)
• Differences in geometry between unsaturated fatty acids and saturated fatty acids

  • Play an important role in biological processes
  • Play an important role in the construction of biological structures (such as cell membranes)
• Unsaturated Fatty Acids


  • Eicosapentaenoic acid
  • Erucic acid
  • Docosahexaenoic acid
• Essential fatty acids


  Fatty acids that are required by the human body but cannot be made in sufficient quantity from other substrates and therefore must be obtained from food
• Essential fatty acid series

  • One has a double bond three carbon atoms removed from the methyl end
  • The other has a double bond six carbon atoms removed from the methyl end
• Linoleic acid (LA) and alpha-linolenic acid (ALA)

  Essential fatty acids that are widely distributed in plant oils
• Human body's ability to convert ALA

  Limited ability to convert ALA into the longer-chain n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)
• Proteins


  Biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form in a biologically functional way
• Polypeptide


  A single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues