Download CHAPTERS 21 AND 22

CHAPTERS 21 AND 22
CONCURRENT ENROLLMENT
NUCLEIC ACID
►A
biomolecule involved in the transfer of genetic
information from existing cells to new cells
► Living cells can produce exact replicas of
themselves
► RNA (ribonucleic acid)
 A nucleic acid found mainly in the cytoplasm of
cells
 Does have a -OH group on the 4th carbon
► DNA (deoxyribonucleic acid)
 A nucleic acid found primarily in the nuclei of
cells
 Does not have a -OH group on the 4th carbon,
both are β configuration
NUCLEOTIDE
► The
repeating structural unit or monomer of
polymeric nucleic acids( has three parts)
► Pyrimidine - two -N– in a heterocyclic, 6 ring
 Uracil (found only in RNA), thymine (found only
in DNA), and cytosine
► Purines - two N– in a heterocyclic, 6 and 5 ring
 Adenine an guanine
 Look on page 651
► Second a sugar D-ribose or D-deoxyribose
► Third is a phosphate derived from phosphoric acid
STRUCTURE OF DNA
► AMP
- has one phosphate, one sugar and one
base
► Nucleic acid backbone
 The sugar and phosphate chain, each one is linked by
a 3' - 5' phosphodiester
SECONDARY STRUCTURE
► Do learning check on page 653 as a problem
► Watson and Crick based on research by Rosalind
Franklin and Wilkins found that all DNA
percentages of adenine and thymine were equal to
each other, this caused a double helix to form
► They run in opposite direction, the two chains
attach by hydrogen bonds. Adenine and thymine
have two hydrogen bonds. Guanine and cytosine
have three hydrogen bonds.
► If we had a base sequence of CCAATTG. What is
the complementary strand?
DNA REPLICATION
Chromosome
 A tightly packed bundle of DNA and protein that is
involved in cell division
► Gene
 An individual section of a chromosomal DNA molecule
that is the fundamental unit of heredity
► Replication
 The process by which an exact copy of a DNA molecule
is produced
► Semiconservative replication
 A replication process that produces DNA molecules
containing one strand from the parent and a new strand
that is complementary to the strand from the parent
► Replication fork
 A point where the double helix of a DNA molecule
unwinds during replication
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PROCESS OF REPLICATION
Step 1
 Unwinding the double helix
► Step 2
 Synthesis of DNA segments
 Okazaki fragment - a DNA fragment produced during
replication as a result of strand growth in a direction
away from the replication fork
► Step 3
 Closing the nicks
 An enzyme called DNA ligase catalyzes this final step
 Replication occurs simultaneously at many points on
the DNA
 Page 660 fig 21.12
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PCR
► Laboratory
technique to mimic replication
► Using a buffered solution with DNA polymerase,
cofactor MgCl2, the four nucleotide building blocks,
and primers the PCR mixture is taken through
three steps
► Heat for several minutes to unravel the DNA
► Cool tube for several minute, this causes the
primers to hydrogen bond to the DNA
► Tube is heated for several minutes and the DNA
polymerase synthesizes a new strand
RNA
RNA differs from DNA in two ways
 Sugar unit
 RNA has uracil instead of thymine
 RNA are single-stranded except in viruses
 RNA do contain regions of double-helical loop
 Found throughout the cell
► Three types of RNA
 Messenger RNA (mRNA) - carries genetic information
from the DNA in the cell nucleus to the site of protein
synthesis in the cytoplasm
► Has a short lifetime - usually less than an hour
 Ribosomal RNA (rRNA) - constitutes about 65% of the
material in ribosomes, the sites of protein synthesis
► Ribosome - a sub cellular particle that serves as the
site of protein synthesis in all organisms
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Continue
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Transfer RNA (tRNA)
 Delivers individual amino acid molecules to the site of
protein synthesis
 Anticodon - a three-base sequence in tRNA that is
complementary to one of the codons in mRNA
Page 663 fig 21.14
Central dogma of molecular biology
 The well-established process by which genetic
information stored in DNA molecules is expressed in the
structure of synthesized proteins
There are two steps involved to flow genetic information
Transcription and translation
In eukaryotes the DNA containing the stored information
is in the nucleus and protein synthesis is in the cytoplasm
TRANSCRIPTION AND TRANSLATION
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Transcription
 The transfer of genetic information from a DNA molecule to a
molecule of messenger RNA
Translation
 The conversion of the code carried by messenger RNA into an
amino acid sequence of a protein
Transcription: RNA synthesis
 RNA polymerase catalyzes the synthesis of RNA
 The DNA helix begins to unwind just before the gene that needs to
be transcribed (only one DNA strand is transcribed)
 One sequence of bases is recognized as the starting point. MRNA
is synthesized in the 5' to 3' direction
 It runs until it reaches another sequence of bases the is a
termination point
 The mRNA molecule move away and the DNA rewinds
 Example 21.2 page 665
Continue
Intron
 A segment of a eukaryotic DNA molecule that carries
no codes for amino acids
► Exon
 A segment of a eukaryotic DNA molecule that is coded
for amino acids
► Heterogeneous nuclear RNA (hnRNA)
 RNA produced when both introns and exons of
eukaryotic cellular DNA are transcribed
► hnRNA undergoes a series of enzyme-catalyzed reactions
that cut and splice the hnRNA to produce mRNA
► Page 667 fig. 21.18
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GENETIC CODE
There are sequences of three bases in the mRNA, there are
64 possible combinations
► Codon
 A sequence of three nucleotide bases that represents a
code word on mRNA molecules
► With very few exceptions a given amino acid is coded by
the same codon in every organism
► Most amino acids are represented by more than one
codon this is called DEGENERACY
► No single codon can represent more than one amino acid
► 61 out of 64 base triplets represent amino acids, the other
three (UAA, UAG, UGA) are signals to chain termination
► AUG is the only start codon if it is the first codon in a
sequence
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TRANSLATION
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There are three major stages of protein synthesis
 Initiation of the polypeptide chain - ribosomes are made
up of a large subunit and a small subunit. The initiation
process begins when the mRNA is aligned on the surface
of the small subunit
 Elongation of the chain - a second site, called the A site
(aminoacyl site), is located on the mRNA-ribosome
complex next to the P site. The A site is where the tRNA
comes to release the amino acid
 Termination of the polypeptide - when a stop codon is
reached the chain is terminated by a termination factor
binding to the stop codon
 Page 671-672
 Learning check page 672
Read pages 673 to 678 some of this will be on the test
NUTRITIONAL REQUIREMENTS
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Read pages 684-693 this will be on the test
Cellular respiration
 Entire process involved in the use of oxygen by cells
 Glucose + O2(g) ---> CO2(g) + H2O(l) + energy
 Fig 22.10 page 694
Metabolism
 The sum of all reactions occurring in an organism
Catabolism
 All reactions involved in the breakdown of biomolecules
Anabolism
 All reactions involved in the synthesis of biomolecules
Metabolic pathway
 A sequence of reactions used to produce one product
or accomplish one process
CATABOLISM
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Three stages
 Digestion - large molecules are chemically broken into
small ones. Most common reaction is hydrolysis
 Small molecules from digestion are degraded to even
smaller units -primarily two carbon acetyl portion of
acetyl coenzyme A. Some energy is released
 The citric acid cycle followed by electron transport and
oxidative phosphorylation - COMMON CATABOLIC
PATHWAY -ATP is formed (body’s form of energy)
 Page 696 fig 22.11
ATP
At the cells pH all protons in ATP are ionized (has a charge
of 4-)
► Other triphosphates can form from the other bases
► A transfer of a phosphate group to water releases energy
(this is free energy ∆G)
► ATP-ADP cycle
 In biological systems, ATP functions as an immediate
donor of free energy rather than as a storage form
► Mitochondria - a cellular organelle where reactions of the
common catabolic pathway occur. Enzymes the catalyze
the formation of ATP are found here
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Continue
► Mitochondrion
membrane
contains and inner and outer
 The inner membrane are called cristae and the
space surrounding it is called the matrix. The
enzymes are found in the inner membrane. The
enzymes to the citric acid cycle are found in the
matrix
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Read about the following coenzymes:
coenzyme A, NAD+, and FAD these will be
on the test pages 700-705