Carbohydrates, Lipids & Proteins by HC130110074239


									Carbohydrates, Lipids & Proteins
• General properties:
  – Hydrophillic (dissolve in water)
  – Generic chemical formula: (CH2O)n
     • Glucose is a 6-carbon sugar…C6H12O6
  – Generally have “root” names with “sacchar” as
    prefix, and/or “-ose” as suffix
     • Glucose, sucrose, saccharide etc.
     • Both sacchar- and –ose mean “sugar/sweet” in latin
• Monomeric sugar: the simplest form
  – Glucose, galactose (milk) and fructose
     • All are chemically: C6H12O6
     • All are isomers of one another (same chemicals make
       them up, but they are arranged into different shapes)
• Dimers of carbohydrates (2-monomers)
   – Sucrose, lactose and maltose
      • Sucrose = table sugar
      • Lactose = milk sugar
      • Maltose…for malted beverages (beer etc.)
   – In the diet, complex polymers of carbohydrates are
     digested into dimers first
      • These dimers are then digested into monomers on the
         surface of the absorptive cells in the intestine
      • You can’t absorb a dimer…you can only absorb a
           – Lactose indigestion = no lactose digesting
• Polymers of carbohydrates (polysaccharides)
  – Long chains of sugar monomers
  – Can be quite large (can be seen with a
    microscope…can crystallize)
• Glycogen:
  – Liver is the primary “body store” for glucose (in
    the form of glycogen)
     • After a meal, blood glucose rises (digestion and
       absorption of dietary carbohydrates)
     • Liver receives insulin signal to remove blood glucose
       (to restore homeostasis)
     • Liver polymerizes glucose into glycogen
     • After a meal (like now), blood glucose drops (rest of
       the body uses up the glucose in the blood)
     • Liver starts to break down glycogen into glucose and
       releases glucose into the blood (to restore glucose
• Glycogen:
  – Formation of glycogen (making the glucose
    tree) = gluconeogenesis or glucogenesis
    • Glycogen anabolism/polymerization = glucogenesis /

  – Breaking down of glycogen (to free up
    glucose into the blood) = gluconeolysis
    • NOT glycolysis or glucolysis (this is something different
      that we’ll cover later)
    • Catabolism/digestion of glycogen = gluconeolysis
• Starch:
  – Primary glucose storage form in PLANTS
     • Made by photosynthesis (we make glycogen
       by using the energy in ATP)
  – The most significant source of dietary
    polysaccharides (carbohydrates)
• Uses:
  – Our bodies use carbohydrates (glucose) for
     • Any carbohydrates that are digested and absorbed are
       eventually formed into glucose (galactose and
       fructose are “converted”)

  – Additional uses:
     • Attaching to proteins (glycoproteins…ie glycocalyx,
     • Attaching to lipids in the plasma membrane
• General properties:
  – Water insoluble (water and oil don’t mix)
  – Similar chemical formula to carbohydrate
    (C-H-O), BUT:
    • VERY HIGH H:O ratio
       – Tristearin (fat) = C57H110O6 (note how many more
         H there is than O)
• 5 types of lipid:
   – Fatty acid (perhaps the most basic form…monomer)
   – Triglyceride (can also be thought of as a basic
     form…but it’s made of 3 fatty acids)
   – Phospholipid
   – Eicosanoid
   – Steroid
• Fatty acid:
    – Chain of 4-24 Carbon atoms
        • On one end of the chain is a carboxyl group (-COOH-)
        • On the other end is a methyl group (CH3)
           – Thus…COOH-----C-C-C-C-C-C------CH3-

Carboxyl group                                    Methyl group
 (C+O+O+H)                                        (C+H+H+H)
• Fatty acid:
  – Chain can be “saturated” or “unsaturated”
     • Depends on the presence / absence of double
       covalent bonds (C=C, versus single C-C)
        – Saturated = NO double bonds (C-C throughout)
        – Unsaturated = at least 1 double bond (C=C
          somewhere along the chain)
            » Mono-unsaturated = single C=C bond
            » Polyunsaturated = 2 + C=C bonds
• Fatty acid:
  – Chain can be “saturated” or “unsaturated”
     • Presence of a C=C double covalent bond
       implies that you can add another C or
       anything else that can bind to the C=C
        – This is why mono- and polyunsaturated fats/oils
          are considered “healthy”…because your body can
          attach stuff to them…saturated fats/oils can’t have
          anything more attached
• Fatty acid:
  – Most fatty acids can be made by your
     • BUT, there are some “essential fatty acids”
        – we cannot make them (don’t have the enzymes to
          make them)
        – Must be eaten or infused
• Triglyceride:
  – 3 fatty acids covalently bonded to a
    glycerol (looks like a trident or 3-pronged
    fork without the handle)
Dehydration synthesis
1.   Remove OH- from the glycerol head (called a glycerol “backbone”)
2.   Remove H+ from the tails (3 fatty acids),
3.   Attach the 3 fatty acid tails to the glycerol
• Phospholipids:
  – Similar to triglyceride, but instead of 3
    fatty acids, there are only 2 fatty acids
    • A phosphate replaces the 3rd fatty acid
    • Imparts hydrophilic nature (phospholipid
       – Therefore, this kind of lipid is “schitzophrenic”
          » Has hydrophobic (fatty acids) domain
          » Has hydrophilic (phosphate) domain
          » Called “amphiphilic”



A “phospholipid” has 2 fatty acid tails, and 1 phosphate group. This phosphate
group is hydrophilic (water friendly).
• Phospholipids:
  – Important because every cell will be
    “made” of phospholipid
    • If every cell in your body were to be made of
      pure fat/lipid, they would repel water…repel
      the ingredients in your blood
       – No contact with water = no way to get nutrients,
         no way to communicate…we’
• Eicosanoids:
  – All are derived from one single type of
    fatty acid (arachadonic acid)
  – Hormone-like signaling molecules
  – Example: prostaglandins
    • Where the C-C chains are re-arranged into
    • Important during inflammation
       – The recent COX-2 drug recall (Vioxx, Celebrex)
         were an attempt to permit prostaglandin synthesis
         but still give arthritis patients a working anti-
         arthritic drug
• Steroids:
  – Primarily made in the liver
  – Not present/available in plants
  – BUT, despite no presence in plants, only
    about 15% of your total cholesterol is
    derived from your diet (liver makes the
• Cholesterol confusion/controversy
  – The advertising is actually incorrect …
    there isn’t a good/bad cholesterol …
    • The good/bad is actually a lipoprotein, not
       – A complex “bead” of cholesterol, fat,
         phospholipid and protein
       – BAD: low density lipoprotein (LDL) = full of
         lipid, cannot be “added” to
       – GOOD: high density lipoprotein (HDL) = not full
         yet…body can still add to it
• Cholesterol confusion/controversy
  – Remember the saturated and unsaturated
    fats (from the fatty acid slides)?
    • It is actually saturated fat that is “mislabeled”
      as “bad cholesterol” rather than cholesterol
• The most important “molecules”
  – Will make and break down carbohydrate
  – Will make and break down lipids
  – Will make and break down proteins
• Polymers of amino acid
  – Amino acids are individual molecules
    made from a single carbon atom
    • Each carbon atom has a carboxyl and amino
       – Similar to a lipid, but instead of a methyl group
         (CH3), there is an amino or nitrogen group (NH3)
    • There are 20 different amino acids
       – Structurally, they are almost identical (1 central
         Carbon, with carboxyl and amino groups)
           » Differences lie in a 2rd group (R-group)
             attached to the Carbon
                              Unique “identifier”
             (aka radical)

Carboxyl                      Amino
(COOH-)                       (NH3-)

    Basic structure of amino acid
• The 20 amino acids are unique from
  one another based on the “R-group” or
  “radical” attached to the carbon atom
  – This R-group can be hydrophobic
    (hydrophobic amino acid)
  – Can be hydrophilic (hydrophilic amino
  – Some can be polar and others are non-
• In order to polymerize amino acids (join them
  together), you need to form a “peptide bond”
   – Bond is formed by dehydration synthesis (just
     like carbohydrates and lipids)
       • Remove the hydroxyl (OH-) group from the
         carboxyl portion of 1 amino acid
       • Remove the H+ from the amino portion of the
         next amino acid
       • Covalently bind the two amino acids together
• As you polymerize amino acids, just like with
   – Dipeptide = 2 amino acids
   – Tripeptide = 3 amino acids
   – Oligopeptide = 10-15 amino acids
   – Polypeptide = more than 15 amino acids
• Remember: despite the length of the amino acid
  chain, there will be only 1 amino group and 1
  carboxyl group on the ENTIRE chain
   – AND, they will be on opposite ends of the amino
     acid chain
• Protein structure is VITAL
  – Different “levels” of protein structure
    • Primary structure = amino acid sequence
       – Each protein is “unique” because of the order of
         the amino acids that are used to “make” it
           » Recall that there are 20 amino acids…each
             protein is a unique arrangement of these 20
             amino acids
• Protein structure is VITAL
  – Different “levels” of protein structure
     • Primary structure = amino acid sequence
     • Secondary structure = coiled or sheet-shape within
       the protein
         – Some amino acids can also interact with other
           amino acids by “hydrogen bonds”
             » This interaction often results in structures like
               an alpha helix (-helix), or
             » Beta sheet (-sheet)
         – Many proteins have BOTH -helix and -sheet
             » Some even have multiple -helices and -
• Recall that some amino acids are
  hydrophilic, and others are hydrophobic
    • An -helix (like a tube) can arrange
      hydrophobic amino acids outwards, and place
      the hydrophilic amino acids INSIDE the
      helix, forming a “water tube”
       – This is important for many membrane transport
       – The hydrophobic amino acids will interact with
         the lipid core of the plasma membrane
       – The hydrophilic amino aids can interact with the
         fluid environment outside/inside the cell
Tertiary structure: the entire protein shape (remember that a
protein can have many alpha helices and beta sheets…many
areas of secondary structure)

                            C                            C
               C     C
 C                                              C
                                 Vs.                         C
              C         C
              Insulin                                   C

• Thus, how you “shape” a protein is very
  important in how it works
  – If the protein is not “shaped” correctly, it
    will be useless
     • Useless proteins = wasted energy to make
     • Useless proteins can also be quite dangerous
• What do they do? (hint…EVERYTHING)
  – Structure: for tissue structure & cell shape
  – Communication: hormones and receptors & other
    signaling proteins
     • Hormones released by 1 cell can signal another
       cell (hormones are proteins)
     • Hormone signals are “received” by receptors
       unique to each hormone (receptors are proteins)
     • “second messengers” often utilize proteins
• What do they do?
  – Membrane transport:
     • Membrane transport proteins (ion channels,
       nutrient transporters, drug transporters)
       permit movement of molecules and
       compounds across a cell membrane
  – Catalysts: enzymes are specialized proteins
      • Specialized for making or breaking bonds…chemical,
        carbohydrate, lipid, amino acid etc.)
   – Recognition and protection: immune recognition
      • Recall how each cell in your body has a “host
        identifier” protein on it’s surface
     Enzymes and metabolism
• Enzyme: specialized protein that catalyzes a
  – Some “older” enzymes are still called by their “original”
     • Trypsin, pepsin etc.
  – More common/scientific names will identify:
     • Substrate (what the enzyme works on)… “___-ase”
        – Carbonic anhydrase (works on carbonic acid)
            » Anhydrase = remove water…remove water
              from carbonic acid
        – Amylase (works on amyl…starch)
     Enzymes and metabolism
• Catalyze = help a reaction occur faster
  – Enzymes do not “force” a reaction…they allow
    it to occur with LESS energy
     • The reaction that an enzyme “catalyzes” would occur
       naturally without that enzyme, BUT, you would need
       much more energy and much more time
• Enzymes are SPECIFIC…they ONLY work
  on particular ingredients, and ONLY
  produce specific products
  – You have specific enzymes for “everything” that
    needs to be anabolised and/or catabolised

• Enzymes recognize their substrates (the
  targets that they will either join or break
  apart) in an “active site”
• Active site: often relies on the specific
  arrangement of amino acids
  – Recall how they can interact at different levels
    of protein structure
• Enzymatic process:
  – Substrate binds to the “specific” binding site in
    the enzyme
     • Forms an “enzyme-substrate complex”
     • Like a “lock and key”
  – Enzyme will either join the substrates, or breaks
    them up (depending on the function of the
• Key features of the enzymatic process:
   – The enzyme DOES NOT change during the
      • It might change shape, but the amino acid sequence remains the
   – The enzyme can usually perform its function (breaking
     or binding) many times before breaking down (wear and
   – This process isn’t always the same length of time
       • Some reactions require more energy and
         others…therefore take more time than others
• Enzymes must operate within:
   – Optimal pH (outside of the optimal pH, the
     enzyme can be “denatured” or lose its structure)
      • Remember the importance of protein “shape”
   – Optimal temperature
      • Too cold = not enough energy
      • Too hot = denature structure
   – This is why pH and temperature homeostasis are
     so important
      • Out of homeostasis = enzyme malfunction …
        metabolism malfunction
• Enzymatic activity can be altered by:
   – Altering the amount of substrate (more =
     faster…to a point)
      • Like the difference between simple diffusion and
        carrier-mediated transport of a molecule across a
        semi-permeable membrane
• Some enzymes also need organic co-factors
  – Specifically, some require “vitamins”
     • “organic” because they have carbon (C-C-C) bonds,
       but are not proteins
  – Vitamins or their derivatives (needed for some
    enzymes to work) are known as “coenzymes”
  – “Vitamins” are organic molecules (carbon-
    based) that are “fortified” or added to the “first-
    world” diets
• Some enzymes interact with other
  enzymes (require 1 enzyme to finish it’s
  task before it can start)
     – “metabolic pathway” where a number of
       enzymes work together

       Enzyme 1        Enzyme 2           Enzyme 3
 A                B                  C               D

         Intermediate reactions…. “intermediates”
      Enzyme         Enzyme              Enzyme
  A      1     B        2            C      3     D

• In a metabolic pathway, having
  “functional” enzymes is VITAL for the
  final outcome
  – If one enzyme does not work, the
    following enzymes cannot do their task
• Glycogen storage disease (liver disorder):
   – Recall the glycogen, the storage form of glucose, looks
     like a tree of glucose monomers
   – Each “branch and leaf” on that tree requires a particular
      • hence glycogen production (gluconeogenesis) is a metabolic
   – Glycogen storage disease has many forms: all stem from
     an individual defect in one of the many enzymes
     involved in building up the glycogen “tree”
      • Without proper glycogen “production”, the patient usually
        suffers diabetes-like symptoms (inadequate blood-glucose
  Without proper
glycogen assembly,
the entire glycogen
molecule cannot be
 created. You then
 get this action…..
 Because the entire
 glycogen molecule
cannot be assembled,
   blood glucose
    regulation is
           Enzymes in your body
• Various enzymes in your body do different things:
   – Hydrolase: digest/catabolise products
      • Digest fats, proteins, carbohydrates, nucleic acids
            –   Esterase
            –   Carbohydrase
            –   Protease
            –   Nuclease
   –   Decarboxylase removes CO2 from substrates
   –   Isomerase changes the shape of a substrate (isomer)
   –   Deaminase removes NH2 (amine)from a substrate
   –   Dehydrogenase removes H from a substrate

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