BIO 1140 Lecture Notes - Lecture 1: Micelle, Cell Membrane, Membrane Transport Protein

69 views8 pages
BIO 1140 Reading #1
The Universal Features of Cells on Earth
Progeny: a descendant or the descendants of a person, animal, or plant; offspring.
Heredity: the passing on of physical or mental characteristics genetically from one generation to
another.
Most living organisms are single cells; others, such as ourselves, are vast multicellular cities in which
groups of cells perform specialized functions and are linked by intricate systems of communication
1013 cells that form a human body. The whole organism has been generated by cell divisions from a
single cell
Complex: Assembly of molecules that are held together by non-covalent bonds. Protein complexes
perform most cell functions.
All Cells Store Their Hereditary Information in the Same Linear Chemical Code (DNA)
Living cells, like computers, deal in information, and it is estimated that they have been evolving and
diversifying for over 3.5 billion years
All living cells on Earth, without any known exception, store their hereditary information in the form of
double-stranded molecules of DNAlong unbranched paired polymer chains, formed always of the
same four types of monomersA, T, C, G.
These monomers are strung together in a long linear sequence that encodes the genetic information,
just as the sequence of 1s and 0s encodes the information in a computer file.
We can take a piece of DNA from a human cell and insert it into a bacterium, or a piece of bacterial DNA
and insert it into a human cell, and the information will be successfully read, interpreted, and copied.
Using chemical methods, scientists can read out the complete sequence of monomers in any DNA
moleculeextending for millions of nucleotidesand thereby decipher the hereditary information that
each organism contains.
DNA (deoxyribonucleic acid): Polynucleotide formed from covalently linked deoxy-ribonucleotide units.
It serves as the store of hereditary information within a cell and the carrier of this information from
generation to generation.
Polymer: Large molecule made by covalently linking multiple identical or similar units (monomers)
together.
Molecule: Group of atoms joined together by covalent bonds
All Cells Replicate Their Hereditary Information by Templated Polymerization
Each monomer in a single DNA strandthat is, each nucleotideconsists of two parts: a sugar
(deoxyribose) with a phosphate group attached to it, and a base, which may be either adenine (A),
guanine (G), cytosine (C) or thymine (T)
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in
Each sugar is linked to the next via the phosphate group, creating a polymer chain composed of a
repetitive sugar-phosphate backbone with a series of bases protruding from it.
The DNA polymer is extended by adding monomers at one end. For a single isolated strand, these can, in
principle, be added in any order, because each one links to the next in the same way, through the part
of the molecule that is the same for all of them. In the living cell, however, there is a constraint: DNA is
not synthesized as a free strand in isolation, but on a template formed by a pre-existing DNA strand.
The bases protruding from the existing strand bind to bases of the strand being synthesized, according
to a strict rule defined by the complementary structures of the bases: A binds to T, and C binds to G. A
double-stranded structure is created, consisting of two exactly complementary sequences of As, Cs, Ts,
and Gs. The two strands twist around each other, forming a double helix.
The bonds between the base pairs are weak compared with the sugar-phosphate links, and this allows
the two DNA strands to be pulled apart without breakage of their backbones. Each strand then can serve
as a template for the synthesis of a fresh DNA.
In different types of cells, this process of DNA replication occurs at different rates, with different
controls to start it or stop it, and different auxiliary molecules to help it along. But the basics are
universal: DNA is the information store, and Templated polymerization is the way in which this
information is copied throughout the living world.
Monomer: Small molecular building block that can serve as a subunit, being linked to others of the same
type to form a larger molecule (a polymer).
Nucleotide: Nucleoside with one or more phosphate groups joined in ester linkages to the sugar moiety.
DNA and RNA are polymers of nucleotides.
Sugar: Small carbohydrates with a monomer unit of general formula (CH2O)n. Examples are the
monosaccharide glucose, fructose and mannose, and the disaccharide sucrose (composed of a molecule
of glucose and one of fructose linked together).
Base: A substance that can accept a proton in solution. The purines and pyrimidines in DNA and RNA are
organic nitrogenous bases and are often referred to simply as bases.
Template: A single strand of DNA or RNA whose nucleotide sequence acts as a guide for the synthesis of
a complementary strand
Complementary: Two nucleic acid sequences are said to be complementary if they can form a perfect
base-paired double helix with each other.
Double helix: The three-dimensional structure of DNA, in which two DNA chains held together by
hydrogen bonding between the bases are wound into a helix.
All Cells Transcribe Portions of Their Hereditary Information into the Same Intermediary Form (RNA)
DNA must also express its information, putting it to use so as to guide the synthesis of other molecules
in the cell. This also occurs by a mechanism that is the same in all living organisms, leading first and
foremost to the production of two other key classes of polymers: RNAs and proteins.
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in
The process begins with a Templated polymerization called transcription, in which segments of the DNA
sequence are used as templates to guide the synthesis of shorter molecules of the closely related
polymer ribonucleic acid, or RNA.
Later, in the more complex process of translation, many of these RNA molecules serve to direct the
synthesis of polymers of a radically different chemical classthe proteins
In RNA, the backbone is formed of a slightly different sugar from that of DNAribose instead of
deoxyriboseand one of the four bases is slightly differenturacil (U) in place of thymine (T)
The other three basesA, C, and Gare the same, and all four bases pair with their complementary
counterparts in DNAthe A, U, C, and G of RNA with the T, A, G, and C of DNA.
During transcription, RNA monomers are lined up and selected for polymerization on a template strand
of DNA in the same way that DNA monomers are selected during replication, consisting of RNA
monomers instead of DNA monomers.
The cell's archive of genetic information in the form of DNA is fixed and sacrosanct (important), the RNA
transcripts are mass-produced and disposable. They serve as messenger RNA (mRNA) to guide the
synthesis of proteins according to the genetic instructions stored in the DNA.
RNA molecules have distinctive structures: Being single-stranded, their backbone is flexible, so that the
polymer chain can bend back on itself to allow one part of the molecule to form weak bonds with
another part of the same molecule
This occurs when segments of the sequence are locally complementary: a ...GGGG... segment, for
example, will tend to associate with a ...CCCC... segment. These types of internal associations can cause
an RNA chain to fold up into a specific shape that is dictated by its sequence
The shape of the RNA molecule, in turn, may enable it to recognize other molecules by binding to them
selectivelyand even, in certain cases, to catalyze chemical changes in the molecules that are
bound. More extensive catalysis by RNA played a central part in the early evolution of life
Cell division: Separation of a cell into two daughter cells. In eukaryotic cells it entails division of the
nucleus (mitosis) closely followed by division of the cytoplasm (cytokinesis).
Transcription (DNA transcription): Copying of one strand of DNA into a complementary RNA sequence
by the enzyme RNA polymerase.
RNA (ribonucleic acid): Polymer formed from covalently linked ribonucleotide monomers.
Translation (RNA translation): Process by which the sequence of nucleotides in a messenger RNA
molecule directs the incorporation of amino acids into protein. It occurs on a ribosome.
Messenger RNA (mRNA): RNA molecule that specifies the amino acid sequence of a protein. Produced
by RNA splicing (in eukaryotes) from a larger RNA molecule made by RNA polymerase as a
complimentary copy of DNA. It is translated into protein in a process catalyzed by ribosomes
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 8 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Progeny: a descendant or the descendants of a person, animal, or plant; offspring. Heredity: the passing on of physical or mental characteristics genetically from one generation to another. Most living organisms are single cells; others, such as ourselves, are vast multicellular cities in which groups of cells perform specialized functions and are linked by intricate systems of communication. The whole organism has been generated by cell divisions from a single cell. Complex: assembly of molecules that are held together by non-covalent bonds. All cells store their hereditary information in the same linear chemical code (dna) Living cells, like computers, deal in information, and it is estimated that they have been evolving and diversifying for over 3. 5 billion years. All living cells on earth, without any known exception, store their hereditary information in the form of double-stranded molecules of dna long unbranched paired polymer chains, formed always of the same four types of monomers a, t, c, g.

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
Booster Classes
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
Booster Classes