Macromolecules

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Macromolecules Background

  • There are four classes of macromolecules: carbohydrates, lipids, proteins, nucleic acids
    due to the ability of carbon to form a backbone and the unique functional groups attached to it.
  • All of them are called polymers. Poly means “many.”  Polymers are made up of many repeating units called

Carbohydrates

  • CHO in a 1:2:1 ratio
  • This is the body’s quick energy source; major form of energy.
  • They are in rings and chains.
  • Be able to draw the ring structure of glucose . 
  • Most simple carbohydrates in our bodies are hexoses. Hex = 6, and –ose means sugar
  • C6H12O6 Most common ones are glucose, fructose, galactose.
  • Pentoses have 5 carbons.

Dehydration Synthesis

  • Forming a bond while losing water
  • Through dehydration synthesis, you link monosaccharides together to form disaccharides
  • You have three major disaccharides in the body, (formed by dehydration synthesis):       
    •  Maltose  (glucose + glucose)
    • Sucrose (glucose + fructose)
    • Lactose  (glucose + galactose)    

Hydrolysis

  • water going into the molecule to break it down
  • The process by which digestion occurs

Polysaccharides

  • GLYCOGEN is animal starch,
    • α-1,4 glycosidic bonds;
    • highly branched sugar storage in an animal cell;
    • glycogen does not pull in water via osmosis as simple sugars do.
  • STARCH IS FROM PLANTS, α-1,4-GLYCOSIDIC BONDS
  • CELLULOSE IS FROM PLANTS, β-1,4-GLYCOSIDIC BONDS.
    No human enzymes will digest it.
  • CHITIN HAS LINKAGES SIMILAR TO CELLULOSE, but has nitrogen in it.  

Lipids

  • Lipids are diverse structurally, but they have in common that they are nonpolar, and that is why they are all grouped in this category
  • Triglycerides are the main source of dietary lipids
  • In the body, triglycerides are made by dehydration synthesis.
  • Saturated vs. unsaturated

  • Omega-3: means the double bond is 3 carbons from the CH3

    • Ω-3 fatty acids are beneficial to us;
    • they reduce cardiovascular disease. 
    • If there is a double- bond between 3 and 4 carbons from the end it’s called Ω-3 fatty acid.

  • Cis and Trans Fatty acids

    • Trans fatty acids stay straight (3-dimensionally; they do not form kinks), like a saturated fat. 
    • Both trans fats and saturated fats
      • Raise total blood cholesterol
      • raise LDLs (bad cholesterol
      • contribute to atherosclerosis
      • lower HDLs (good cholesterol, which helps to prevent atherosclerosis)

  • Ketone Bodies

    • 4-Carbon compounds
    • breakdown products of fatty acids, formed during fasting
    • acetone breath (sweet) results
    • Ketosis - when fatty acids break down into ketones
    • Ketosis could result in ketoacidosis, which seriously lowers blood pH, which could be deadly (diabetics can’t metabolize glucose and therefore they break down fats excessively and this could happen).

  • Phospholipids

    • Amphipathic – part polar and part nonpolar
      • Their amphipathic nature allows them to interfere with water’s surface tension, and therefore they are a good lung surfactant, preventing too much surface tension and lung collapse.
    • they have a polar head made up primarily of phosphate, and two fatty acid tails
    • make up the membrane bilayer
    • Micelles - structures formed when phospholipids are dissolved in aqueous solutions; 
      • similar to the structures formed when phospholipids are free in blood.

  • Steroids

    • These are lipids, nonpolar, ring molecules
    • Cholesterol – sits in the plasma membrane
    • Many hormones, such as gonad hormones like testosterone, estrogen, are derived from cholesterol. Also, corticosteroids like the stress hormone cortisol from the adrenal cortex.
    • They also play important roles in vitamin D formation

  • Prostaglandins

    • Prostaglandins regulate: blood vessel diameter, ovulation, uterine contractions, inflammation, blood clotting.
    • A type of fatty acid with a cyclic hydrocarbon
    • Name is derived from “prostate,” where they were originally found

Proteins

  • made up of amino acids
  • Examples are Hormones, enzymes, antibodies, proteins of muscle contraction

  • Amino acids

    • There are twenty different functional groups
    • 8 are essential; 12 are nonessential
    • essential = required in your diet
    • nonessential = not required in your diet because your body can make them 
    • amino acids are joined together by peptide bonds to form a chain (primary structure)
      this is due to dehydration synthesis

  • Protein folding

    • PRIMARY STRUCTURE – is the linear sequence of amino acids.
    • SECONDARY STRUCTURE: primary structure folds in on itself (secondary structure is due to hydrogen bonds) and forms α-helices and β-pleated sheets
    • Tertiary structure forms when the α-helices  and β-pleated sheets fold in on themselves DUE TO MANY TYPES OF BONDS (ionic, hydrogen, hydrophobic interactions)
      Since weak bonds hold tertiary structure together, a protein is easily denatured (unfolded) by changes in pH or temperature.  This is one reason that fevers are so bad for the body.  Prions (mad cow disease) result from changes in the shapes of normal proteins. 
    • Quaternary structure is due to multiple polypeptides coming together
      such as in the case with HEMOGLOBIN, which is four polypeptide chains coming together.
    • Folding is extremely important in distinguishing the function of the protein  SHAPE IS IMPORTANT.
    • There are also conjugated proteins (p. 43), which are proteins with a nonprotein component; hemoglobin is one because it has the heme; myoglobin also has heme, some are glycoproteins, such as the cell surface markers of red blood cells.

Nucleic Acids

  • Building blocks for nucleic acids, DNA and RNA
  • DNA is double stranded; RNA is single stranded, but has double stranded regions due to the RNA folding back on itself.
  • Composed of a five-carbon sugar, a phosphate group, and a nitrogenous base
  • Nitrogenous bases fall into two categories:
    • Pyrimidine:  a single carbon ring + nitrogen
      • Cytosine, thymine, uracil
    • Purine: 2 carbon rings + nitrogen
      • Guanine, adenine
  • Pentose sugars are deoxyribose or ribose
  • The sugar in this molecule is called deoxyribose and can bind to one of four nitrogenous bases:
    • Guanine
    • Thymine
    • Cytosine
    • Adenine
  • Deoxyribose bonds with a phosphate group (via dehydration synthesis) to form a long chain, which serves as the backbone of the molecule.
  • Remember the differences between DNA and RNA

  • Types of RNA

    • Different types of RNA are used to take information for assembling a protein out of the nucleus and to actually assemble it:
      • Pre-MRNA,
      • Messenger RNA (mRNA)
      • Transfer RNA (tRNA)
      • Ribosomal RNA (rRNA)
      • Other RNA-related molecules serve important functions in the body
        • ATP, GTP – energy carriers
        • cAMP - regulation
        • NAD, FAD – co-enzymes

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