Biochemistry

1
Biochemistry

• Enzymes, Vitamins, Hormones

2
Metabolism

• Metabolism is the sun total of all the enzyme
  catalyzed reactions of the body
• Catabolic reactionsbreak down large molecules
  into smaller parts plus release energy
• Anabolic reactionsbuild up large molecules to be
  used in growth and repair. These always require
  energy

3
Enzymes

• Largest and most specialized class of proteins.
• Function is to act as biological catalysts.
• Make biological reactions go much faster
• Enzymes are used over and over, so they only need
  to be present in small amounts
• Usually made of only one protein chain, but can
  be composed of several and have non-protein parts

4
Enzyme Terms

• Apoenzymeprotein part of the enzyme molecule
• Cofactoradditional non-protein part, usually a
  metal ion or complex organic molecule
• Coenzymeany complex organic cofactor
• Prosthetic groupcofactor permanently bonded to
  the enzyme
• Substratesubstance or substances the enzyme acts
  upon
• Active sitespecific area of the enzyme which
  attaches to the substrate. There may be more
  than one

5
Enzyme Names and Classes

• Enzymes were originally named with in suffix,
  but this was changed by biochemists in 1961. Now
  enzymes are named according to their substrate
  and have an ase suffix.
• Enzyme classes
• Hydrolasescatalyze hydrolysis reactions
• carbohydrases, proteases, nucleases,
  etc.
• Oxidoreductasesadd oxygen or remove hydrogen
• from a molecule
• Transferasesmove functional groups from one
• molecule to anothertransaminase, transacylase,
  
• transphosphatase
• Lyaseforms double bonds
• Isomerasechanges one isomer into another
• Ligasemakes new bonds between pieces

6
Examples of Enzymes

• Hydrolasessucrasebreaks down sucrose
• pepsinbreaks down protein
• Transferasestransphosphataseadds phosphate to
  different molecules in metabolism
• Oxidoreductasepyruvate dehydrogenasetakes
  hydrogen from pyruvate in cellular respiration

7
Method of Enzyme Action

• Enzymes apparently work, according to
  observation, in three steps
• 1. Enzyme and substrate bond together.
• 2. The bound enzyme-substrate becomes activated
  through the active site
• 3. The reaction takes place and the product or
  products are released, leaving the enzyme ready
  to work again

8
Speed of Enzyme Action

• Enzymes only work when the conditions are ideal
  pH and temperature must be right. Only then will
  the maximum rate be achieved.
• The efficiency of an enzyme is measured by its
  turnover number, the number of substrate
  molecules transformed in one minute by one
  molecule. Some are very fast, up to 36 million
  per minute, others not so fast.
• If a molecule has a rate of 30,000 per minute,
  how many per hour? Use the bridge method
• 30000 molecules 60 min 1,800,000 /
  hr
• 1 min 1 hr

9
Enzyme Specificity

• Enzymes are different than inorganic catalysts in
  that they will only work on one type of reaction
  and often on only one substrate
• This specificity is explained through the
  lock-and-key or induced-fit theories. Both state
  that the shape, whether fixed or influenced, is
  the reason for recognition of one substrate and
  no other.

10
Factors Affecting Enzymes

• pHdue to the isoelectric point previously
  studied, enzymes will function best at one
  specific pH, less at slightly higher or lower,
  and not at all if too high or low. The reason
  for buffer systems is often to make sure the pH
  is right for enzymes to work.
• Temperaturespeed of molecules is increased or
  decreased directly by temperature variations, but
  enzymes can be totally destroyed by too high of
  temperature. Most enzymes work best in a range
  of 35-45º C, body temperatures. The reason
  refrigerators work is that they slow enzyme
  action, but do not stop it. This is why spoilage
  still does happen, especially after removal from
  the refrigerator.

11
Inhibition of Enzymes

• Some enzymes are ones we dont want to work, such
  as in viruses and bacteria. Drugs are used often
  to slow or inactivate enzyme action
• Irreversiblethe agent removes or blocks the
  active site of the enzyme. Cholinesterase is
  necessary to transmit nerve impulses, but nerve
  gas combines with part of the molecule and blocks
  the action. Nerve gas thus paralyzes an animal
  by blocking nerve action

12
Inhibition of Enzymes

• Reversiblecan be due to competitive or
  non-competitive molecules affecting the enzyme
• Competitivea similar molecule to the substrate
  attaches to the active site, but does not react
  as the substrate does
• Non-competitivea molecule attaches to a
  different part of the enzyme and deactivates it
  so that it no longer works on its substrate

13
Special Inhibitors

• Antibioticschemicals extracted from organisms
  which inhibit or destroy microorganisms. Some
  act to inhibit enzymes which make important
  growth factors, others to stop production or to
  weaken structures within a bacteria
• Chemotherapychemicals which interfere with
  enzymes important in the rapid reproduction of
  cancer cell DNA. One of these is 5-fluoro
  uracil, which disrupts DNA formation and RNA
  action.

14
Homework 18-a

• p. 459 CYU all
• p. 463 CYU all
• p. 467 CYU all
• p. 481ff 2, 5, 6, 8, 10, 13, 14, 18

15
Regulation

• Enzymes must be controlled so that they do not
  all work at once. This is done by selective
  inhibition of the regulatory enzyme in a
  multi-step process. This regulatory enzyme has
  extra sites which control its action
• Some of these regulatory enzymes are controlled
  by the end product of the process in a feedback
  inhibition system.

16
Hormones

• Hormones are chemicals formed in glands which
  perform regulatory functions. Each has target
  organs or cells influenced by its presence.
• Two varieties have typical functions
• Steroid hormones, such as estrogen and
  testosterone act as activators of genetic factors
• Peptide hormones, such as insulin and HGH attach
  to cells to cause the cell to adapt to their
  commands

17
Hormones

• From the list on p. 471 in the book, know the
  following
• Site of manufacture, action, necessary
  materials for manufacture, common names for
  thyroxine, insulin, epinephrine, oestrogen, and
  testosterone

18
Secondary Messengers

• Some molecules which act like hormones, but are
  not made in only one place, are the secondary
  messengers. These include cyclic AMP and
  prostaglandins
• Cyclic AMP is made within cells and acts when a
  hormone attaches to a cell. It is responsible in
  making the cell respond to the instructions of
  the hormone.
• Prostaglandins are made from fatty acids and
  alert the body to problem conditions. Once the
  problem is known however, we usually want to
  block their effects, such as fever and
  inflammation. This can be done with ASA
  (aspirin) or hydrocortisone.

19
Homework 18b

• p. 474 CYU all
• p. 483 20, 21, 22

20
Vitamins

• Vitamins are small organic molecules that are
  essential to maintain health. A proper diet will
  give adequate amounts of vitamins, but when they
  are deficient, several diseases can occur.
• Vitamins are either fat or water soluble and
  their ability to be stored depends upon that.
• From the table on p. 476, know the following
• Sources, deficiency problems, and chemical names
  for Vitamins A, C, D, B12, and B6

21
Vitamins

• Water soluble
• Vitamin Cneeds to be replaced daily, helps to
  make collagen and acts as a reducing agent in the
  body
• Vitamin B familyseveral compounds which act as
  coenzymes in metabolism

22
Vitamins

• Fat soluble
• Vitamin Astored in liver, maintains healthy
  skin and vision, poisonous if in excess
• Vitamin Kimportant in the blood clotting
  mechanism
• Vitamin Eprevents free radicals from attacking
  membranes, especially in reproductive organs
• Vitamin Dcontrols concentration of calcium
  ions, important for bones and muscle action. Can
  be made in the skin by sunlight

23
Homework 18c

• p. 480 CYU all
• p. 483ff 24, 27, 28, 30