introduction
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CYL414: An Introduction to Biochemistry
Cell as structural and functional units of life
Instructor: Yashveer Singh, Chemistry
29 July 2015
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High degree of chemical complexity and microscopic organization
System for extracting, transforming and using energy from the
environment
Defined functions for organism’s components and regulated
interactions among them
Mechanism for sensing and responding to alterations in their
surroundings
Capacity for precise replication and self assembly
Capability to survive over time by gradual evolution
Distinguishing features of living organisms
Lehninger Principles of Biochemistry
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What is common to all life forms?
Whole bacteria comprises just one cell
(unicellular organisms)
An adult human body comprises
30 trillion cells
(multicellular organisms)
All living organisms, whether big or small, contain cells
Even a single cell is able to carry out essential life processes
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What is common to all life forms?
Lehninger Principles of Biochemistry
Diverse organisms, with nothing in common, are shown in the
painting, except the fact that all contain one or more cells
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All molecules, whether big or small, contain atoms
Atoms are units of molecule
What is common to all molecules?
Stoker’s Chemistry
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All buildings, whether big or small, will contain bricks
What is common to all buildings?
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Male reproductive organ produces several hundred million sperms
every day, which undergo division to form spermatozoa
Female reproductive organs produces (~2 million) eggs, which
undergo division to produce ovum
How does life begins in multicellular organisms?
http://www.biology.iupui.edu/biocourses/N100H/ch9meiosis.html
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The spermatozoa and ovum (called gametes) fuses during the
fertilization to form a zygote
Zygote, which is a single cell, undergo division and differentiation
to form a multicellular organism in less than a year after fertilization
Ever for multicellular organisms, life begins as a single cell
How does life begins in multicellular organisms?
http://www.biology.iupui.edu/biocourses/N100H/ch9meiosis.html
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The zygote undergoes mitotic division to form blastula, which is a
hollow ball of cells
Ultimately, three germ layers are produced: ectoderm, mesoderm,
and endoderm
How does life begins in multicellular organisms?
https://smartsite.ucdavis.edu/access/content/user/00002950/bis10v/week10/13z
ygoteembroyo.html
csls-text2.c.u-tokyo.ac.jp
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The three layer differentiate and arrange into tissue, organs, and
organ systems. Ectoderm gives rise to skin and nervous system;
endoderm to the lining of digestive and respiratory tracts, parts of the
liver and pancreas, and bladder lining; and mesoderm to muscles,
skeleton, circulatory system, excretory system, gonads, and inner
layer of skin (dermis)
All the structure of a multicellular organism arises from division
and differentiation of a single cell
All functions carried out by a multicellular organism is due to the
arrangement of cells into tissue, organs, and organ system
How does life begins in multicellular organisms?
https://smartsite.ucdavis.edu/access/content/user/00002950/bis10v/week10/13z
ygoteembroyo.html
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Therefore, the structural and functional unit of life is cell
No matter which organism it is, it must posses at least a cell
To understand life, one must go to cellular level
What is the unit of life?
Lehninger Principles of Biochemistry
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Living organism unlike nonliving materials, are rich in carbon,
hydrogen, and oxygen
It suggest possibility of carbon (organic) compounds
Chemical composition of living organisms
Biochemistry by Garrett and Grisham
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Carbon can form single, double, and triple bonds
A single carbon can form multiple bonds with variety of atoms
Carbon compounds also contain diverse set of functional groups
Chemical composition of living organisms
Lehninger Principles of Biochemistry
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Therefore, carbons have the unique ability to form complex
structures with long chain along with variety of rings and functional
groups
Chemical composition of living organisms
Lehninger Principles of Biochemistry
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Cells have universal set of small molecules: amino acids,
nucleotides, sugars and their phosphorylated derivatives, and mono-,
di-, and tricarboxylic acids
These molecules are used to assemble macromolecules:
polysaccharides, proteins, nucleic acids, and lipids (not a true
polymer)
Chemical composition of cells
Lehninger Principles of Biochemistry
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Stereochemistry also plays an
important role
A macromolecule may have cis-
an/or trans center
As a results the two isomers may
have very different structures
Chemical composition of cells
Lehninger Principles of Biochemistry
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If molecular asymmetry is present, macromolecules may also
exhibit optical isomerism
As a result interactions between macromolecules are stereospecific
Chemical composition of cells
Lehninger Principles of Biochemistry
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Cells in true sense a hierarchical organization of biomolecules or
macromolecules (continued on next slide)
Chemical composition of cells
Lehninger Principles of Biochemistry
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In the first step, macromolecules or biomecules are assembled.
Amino acids are used for protein synthesis, nucleotides for nucleic
acids, sugars for polysaccharide, and so on. These macromolecules
are formed using mainly covalent bonds
The macromolecules are then assembled into supramoleculer
assemblies (cell organelles) using noncovalent interactions. For
example, plasma membrane is assembled using lipid and proteins and
chromosomes are assembled using protein and nucleic acids
Finally, supramolecular assemblies (organelles) are arranged into a
cell structure
Chemical composition of cells
Lehninger Principles of Biochemistry
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Therefore, biochemistry is understanding the molecular basis of life
processes occurring at the level of cells
Then, what is biochemistry?
Lehninger Principles of Biochemistry
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Different classes of organisms
Lehninger Principles of Biochemistry
All living organisms are grouped into three categories: bacteria,
archaea, and eukarya
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Aerobic
Needs oxygen Anaerobic
Do not need oxygen
Obligate
Will not survive in the
presence of oxygen
Facultative
Will survive with or
without oxygen
Bacteria and archaea
Bacteria and archaea are unicellular organisms and can be either
aerobic or anerobic
Different classes of organisms
Lehninger Principles of Biochemistry
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Different classes of organisms
Living organisms are also categorized based on their source of
energy as shown above
Lehninger Principles of Biochemistry
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Viruses are considered non-living
because they need host cells to
grow and reproduce
What about viruses?
Timberlake’s Chemistry