AMENDED AND RESTATED
 
                          CERTIFICATE OF INCORPORATION
 
                                       OF
 
                                 METABOLIX, INC.
 
          Metabolix, Inc., a corporation organized and existing under the laws
     of the State of Delaware (the "Corporation"), hereby certifies as follows:
 
     1.   The name of the Corporation is Metabolix, Inc. The original
certificate of incorporation of Metabolix, Inc. was filed with the Secretary of
State of the State of Delaware on September 1, 1998.
 
     2.   This Amended and Restated Certificate of Incorporation was duly
adopted in accordance with the provisions of Sections 242 and 245 of the
Delaware General Corporation Law (the "DGCL").
 
     3.   The text of the Certificate of Incorporation of this corporation be
hereby amended and restated in its entirety to provide as herein set forth in
full.
 
                                    ARTICLE I
 
     The name of the Corporation is Metabolix, Inc.
 
                                   ARTICLE II
 
     The address of the Corporation's registered office in the State of Delaware
is c/o The Corporation Trust Company, 1209 Orange Street in the City of
Wilmington, County of New Castle. The name of its registered agent at such
address is The Corporation Trust Company.
 
                                   ARTICLE III
 
     The purpose of the Corporation is to engage in any lawful act or activity
for which corporations may be organized under the DGCL.
 
                                   ARTICLE IV
 
                                  CAPITAL STOCK
 
     The total number of shares of capital stock which the Corporation shall
have authority to issue is One Hundred Five Million (105,000,000) shares, of
which (i) One Hundred Million (100,000,00) shares shall be a class designated as
common stock, par value $.01 per share (the
 
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"Common Stock"), and (ii) Five Million (5,000,000) shares shall be a class
designated as undesignated preferred stock, par value $.01 per share (the
"Undesignated Preferred Stock").
 
     The number of authorized shares of the class of Undesignated Preferred
Stock may from time to time be increased or decreased (but not below the number
of shares outstanding) by the affirmative vote of the holders of a majority of
the outstanding shares of Common Stock entitled to vote, without a vote of the
holders of the Undesignated Preferred Stock (except as otherwise provided in any
certificate of designations of any series of Undesignated Preferred Stock).
 
     The powers, preferences and rights of, and the qualifications, limitations
and restrictions upon, each class or series of stock shall be determined in
accordance with, or as set forth below in, this Article IV.
 
                                 A. COMMON STOCK
 
          Subject to all the rights, powers and preferences of the Undesignated
Preferred Stock and except as provided by law or in this Article IV (or in any
certificate of designations of any series of Undesignated Preferred Stock):
 
               (a)  the holders of the Common Stock shall have the exclusive
right to vote for the election of directors of the Corporation (the "Directors")
and on all other matters requiring stockholder action, each outstanding share
entitling the holder thereof to one vote on each matter properly submitted to
the stockholders of the Corporation for their vote; PROVIDED, HOWEVER, that,
except as otherwise required by law, holders of Common Stock, as such, shall not
be entitled to vote on any amendment to this Certificate (or on any amendment to
a certificate of designations of any series of Undesignated Preferred Stock)
that alters or changes the powers, preferences, rights or other terms of one or
more outstanding series of Undesignated Preferred Stock if the holders of such
affected series are entitled to vote, either separately or together with the
holders of one or more other such series, on such amendment pursuant to this
Certificate (or pursuant to a certificate of designations of any series of
Undesignated Preferred Stock) or pursuant to the DGCL;
 
               (b)  dividends may be declared and paid or set apart for payment
upon the Common Stock out of any assets or funds of the Corporation legally
available for the payment of dividends, but only when and as declared by the
Board or any authorized committee thereof; and
 
               (c)  upon the voluntary or involuntary liquidation, dissolution
or winding up of the Corporation, the net assets of the Corporation shall be
distributed pro rata to the holders of the Common Stock.
 
                         B. UNDESIGNATED PREFERRED STOCK
 
          The Board of Directors or any authorized committee thereof is
expressly authorized, to the fullest extent permitted by law, to provide for the
issuance of the shares of
 
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Undesignated Preferred Stock in one or more series of such stock, and by filing
a certificate pursuant to applicable law of the State of Delaware, to establish
or change from time to time the number of shares of each such series, and to fix
the designations, powers, including voting powers, full or limited, or no voting
powers, preferences and the relative, participating, optional or other special
rights of the shares of each series and any qualifications, limitations and
restrictions thereof.
 
                                    ARTICLE V
 
                               STOCKHOLDER ACTION
 
     1.   ACTION WITHOUT MEETING. Except as otherwise provided herein, any
action required or permitted to be taken by the stockholders of the Corporation
at any annual or special meeting of stockholders of the Corporation must be
effected at a duly called annual or special meeting of stockholders and may not
be taken or effected by a written consent of stockholders in lieu thereof.
 
     2.   SPECIAL MEETINGS. Except as otherwise required by statute and subject
to the rights, if any, of the holders of any series of Undesignated Preferred
Stock, special meetings of the stockholders of the Corporation may be called
only by the Board of Directors acting pursuant to a resolution approved by the
affirmative vote of a majority of the Directors then in office. Only those
matters set forth in the notice of the special meeting may be considered or
acted upon at a special meeting of stockholders of the Corporation.
 
                                   ARTICLE VI
 
                                    DIRECTORS
 
     1.   GENERAL. The business and affairs of the Corporation shall be managed
by or under the direction of the Board of Directors except as otherwise provided
herein or required by law.
 
     2.   ELECTION OF DIRECTORS. Election of Directors need not be by written
ballot unless the By-laws of the Corporation (the "By-laws") shall so provide.
 
     3.   NUMBER OF DIRECTORS; TERM OF OFFICE. The number of Directors of the
Corporation shall be fixed solely and exclusively by resolution duly adopted
from time to time by the Board of Directors. The Directors, other than those who
may be elected by the holders of any series of Undesignated Preferred Stock,
shall be classified, with respect to the term for which they severally hold
office, into three classes, as nearly equal in number as reasonably possible.
The initial Class I Directors of the Corporation shall be Edward M. Muller and
Simon F. Williams, Ph.D.; the initial Class II Directors of the Corporation
shall be Jack W. Lasersohn, Jay Kouba, Ph.D., and Oliver P. Peoples, Ph.D.; and
the initial Class III Directors of the Corporation shall be Edward M. Giles,
Anthony J. Sinskey, Sc.D., and James J. Barber, Ph.D. The initial Class I
Directors shall serve for a term expiring at the annual meeting of stockholders
to be held
 
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in 2007, the initial Class II Directors shall serve for a term expiring at the
annual meeting of stockholders to be held in 2008, and the initial Class III
Directors shall serve for a term expiring at the annual meeting of stockholders
to be held in 2009. At each annual meeting of stockholders, Directors elected to
succeed those Directors whose terms expire shall be elected for a term of office
to expire at the third succeeding annual meeting of stockholders after their
election. Notwithstanding the foregoing, the Directors elected to each class
shall hold office until their successors are duly elected and qualified or until
their earlier resignation or removal.
 
     Notwithstanding the foregoing, whenever, pursuant to the provisions of
Article IV of this Certificate, the holders of any one or more series of
Undesignated Preferred Stock shall have the right, voting separately as a series
or together with holders of other such series, to elect Directors at an annual
or special meeting of stockholders, the election, term of office, filling of
vacancies and other features of such directorships shall be governed by the
terms of this Certificate and any certificate of designations applicable
thereto.
 
     4.   VACANCIES. Subject to the rights, if any, of the holders of any series
of Undesignated Preferred Stock to elect Directors and to fill vacancies in the
Board of Directors relating thereto, any and all vacancies in the Board of
Directors, however occurring, including, without limitation, by reason of an
increase in size of the Board of Directors, or the death, resignation,
disqualification or removal of a Director, shall be filled solely and
exclusively by the affirmative vote of a majority of the remaining Directors
then in office, even if less than a quorum of the Board of Directors, and not by
the stockholders. Any Director appointed in accordance with the preceding
sentence shall hold office for the remainder of the full term of the class of
Directors in which the new directorship was created or the vacancy occurred and
until such Director's successor shall have been duly elected and qualified or
until his or her earlier resignation or removal. Subject to the rights, if any,
of the holders of any series of Undesignated Preferred Stock to elect Directors,
when the number of Directors is increased or decreased, the Board of Directors
shall, subject to Article VI.3 hereof, determine the class or classes to which
the increased or decreased number of Directors shall be apportioned; PROVIDED,
HOWEVER, that no decrease in the number of Directors shall shorten the term of
any incumbent Director. In the event of a vacancy in the Board of Directors, the
remaining Directors, except as otherwise provided by law, shall exercise the
powers of the full Board of Directors until the vacancy is filled.
 
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     5.   REMOVAL. Subject to the rights, if any, of any series of Undesignated
Preferred Stock to elect Directors and to remove any Director whom the holders
of any such stock have the right to elect, any Director (including persons
elected by Directors to fill vacancies in the Board of Directors) may be removed
from office (i) only with cause and (ii) only by the affirmative vote of the
holders of 75% or more of the shares then entitled to vote at an election of
Directors. At least forty-five (45) days prior to any meeting of stockholders at
which it is proposed that any Director be removed from office, written notice of
such proposed removal and the alleged grounds thereof shall be sent to the
Director whose removal will be considered at the meeting.
 
                                   ARTICLE VII
 
                             LIMITATION OF LIABILITY
 
     A Director of the Corporation shall not be personally liable to the
Corporation or its stockholders for monetary damages for breach of fiduciary
duty as a Director, except for liability (a) for any breach of the Director's
duty of loyalty to the Corporation or its stockholders, (b) for acts or
omissions not in good faith or which involve intentional misconduct or a knowing
violation of law, (c) under Section 174 of the DGCL or (d) for any transaction
from which the Director derived an improper personal benefit. If the DGCL is
amended after the effective date of this Certificate to authorize corporate
action further eliminating or limiting the personal liability of Directors, then
the liability of a Director of the Corporation shall be eliminated or limited to
the fullest extent permitted by the DGCL, as so amended.
 
     Any repeal or modification of this Article VII by either of (i) the
stockholders of the Corporation or (ii) an amendment to the DGCL, shall not
adversely affect any right or protection existing at the time of such repeal or
modification with respect to any acts or omissions occurring before such repeal
or modification of a person serving as a Director at the time of such repeal or
modification.
 
                                  ARTICLE VIII
 
                              AMENDMENT OF BY-LAWS
 
     1.   AMENDMENT BY DIRECTORS. Except as otherwise provided by law, the
By-laws of the Corporation may be amended or repealed by the Board of Directors
by the affirmative vote of a majority of the Directors then in office.
 
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     2.   AMENDMENT BY STOCKHOLDERS. The By-laws of the Corporation may be
amended or repealed at any annual meeting of stockholders, or special meeting of
stockholders called for such purpose as provided in the By-laws, by the
affirmative vote of at least 75% of the outstanding shares entitled to vote on
such amendment or repeal, voting together as a single class; PROVIDED, HOWEVER,
that if the Board of Directors recommends that stockholders approve such
amendment or repeal at such meeting of stockholders, such amendment or repeal
shall only require the affirmative vote of the majority of the outstanding
shares entitled to vote on such amendment or repeal, voting together as a single
class.
 
                                   ARTICLE IX
 
                    AMENDMENT OF CERTIFICATE OF INCORPORATION
 
     The Corporation reserves the right to amend or repeal this Certificate in
the manner now or hereafter prescribed by statute and this Certificate, and all
rights conferred upon stockholders herein are granted subject to this
reservation. Whenever any vote of the holders of voting stock is required to
amend or repeal any provision of this Certificate, and in addition to any other
vote of holders of voting stock that is required by this Certificate or by law,
such amendment or repeal shall require the affirmative vote of the majority of
the outstanding shares entitled to vote on such amendment or repeal, and the
affirmative vote of the majority of the outstanding shares of each class
entitled to vote thereon as a class, at a duly constituted meeting of
stockholders called expressly for such purpose; PROVIDED, HOWEVER, that the
affirmative vote of not less than 75% of the outstanding shares entitled to vote
on such amendment or repeal, and the affirmative vote of not less than 75% of
the outstanding shares of each class entitled to vote thereon as a class, shall
be required to amend or repeal any provision of Article V, Article VI, Article
VII, Article VIII or Article IX of this Certificate.
 
                                  [End of Text]
 
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     THIS AMENDED AND RESTATED CERTIFICATE OF INCORPORATION is executed as of
this ____ day of __________, 2006.
 
 
                                      METABOLIX, INC.
 
 
                                      ------------------------------------------
                                      By: James Barber,
                                      Its: Chief Executive Officer and President