CHAPTERS 21 AND 22CHAPTERS 21 AND 22

CONCURRENT ENROLLMENTCONCURRENT ENROLLMENT

NUCLEIC ACIDNUCLEIC ACID► A biomolecule involved in the transfer of genetic A biomolecule involved in the transfer of genetic

information from existing cells to new cellsinformation from existing cells to new cells► Living cells can produce exact replicas of Living cells can produce exact replicas of

themselvesthemselves► RNA (ribonucleic acid)RNA (ribonucleic acid)

A nucleic acid found mainly in the cytoplasm A nucleic acid found mainly in the cytoplasm of cellsof cells

Does have a -OH group on the 4th carbonDoes have a -OH group on the 4th carbon► DNA (deoxyribonucleic acid)DNA (deoxyribonucleic acid)

A nucleic acid found primarily in the nuclei of A nucleic acid found primarily in the nuclei of cellscells

Does not have a -OH group on the 4th Does not have a -OH group on the 4th carbon, both are carbon, both are ββ configuration configuration

NUCLEOTIDENUCLEOTIDE

► The repeating structural unit or monomer of The repeating structural unit or monomer of polymeric nucleic acids( has three parts)polymeric nucleic acids( has three parts)

► Pyrimidine - two -N– in a heterocyclic, 6 ringPyrimidine - two -N– in a heterocyclic, 6 ring Uracil (found only in RNA), thymine (found Uracil (found only in RNA), thymine (found

only in DNA), and cytosineonly in DNA), and cytosine► Purines - two N– in a heterocyclic, 6 and 5 ringPurines - two N– in a heterocyclic, 6 and 5 ring

Adenine an guanineAdenine an guanine Look on page 651Look on page 651

► Second a sugar D-ribose or D-deoxyriboseSecond a sugar D-ribose or D-deoxyribose► Third is a phosphate derived from phosphoric Third is a phosphate derived from phosphoric

acidacid

STRUCTURE OF DNASTRUCTURE OF DNA

► AMP - has one phosphate, one sugar and AMP - has one phosphate, one sugar and one baseone base

► Nucleic acid backboneNucleic acid backbone The sugar and phosphate chain, each one is The sugar and phosphate chain, each one is

linked by a 3' - 5' phosphodiester linked by a 3' - 5' phosphodiester

SECONDARY STRUCTURESECONDARY STRUCTURE

► Do learning check on page 653 as a problemDo learning check on page 653 as a problem► Watson and Crick based on research by Watson and Crick based on research by

Rosalind Franklin and Wilkins found that all Rosalind Franklin and Wilkins found that all DNA percentages of adenine and thymine DNA percentages of adenine and thymine were equal to each other, this caused a were equal to each other, this caused a double helix to formdouble helix to form

► They run in opposite direction, the two chains They run in opposite direction, the two chains attach by hydrogen bonds. Adenine and attach by hydrogen bonds. Adenine and thymine have two hydrogen bonds. Guanine thymine have two hydrogen bonds. Guanine and cytosine have three hydrogen bonds.and cytosine have three hydrogen bonds.

► If we had a base sequence of CCAATTG. What If we had a base sequence of CCAATTG. What is the complementary strand?is the complementary strand?

DNA REPLICATIONDNA REPLICATION► ChromosomeChromosome

A tightly packed bundle of DNA and protein that is A tightly packed bundle of DNA and protein that is involved in cell divisioninvolved in cell division

► GeneGene An individual section of a chromosomal DNA An individual section of a chromosomal DNA

molecule that is the fundamental unit of hereditymolecule that is the fundamental unit of heredity► ReplicationReplication

The process by which an exact copy of a DNA The process by which an exact copy of a DNA molecule is producedmolecule is produced

► Semiconservative replicationSemiconservative replication A replication process that produces DNA molecules A replication process that produces DNA molecules

containing one strand from the parent and a new containing one strand from the parent and a new strand that is complementary to the strand from strand that is complementary to the strand from the parentthe parent

► Replication forkReplication fork A point where the double helix of a DNA molecule A point where the double helix of a DNA molecule

unwinds during replicationunwinds during replication

PROCESS OF REPLICATIONPROCESS OF REPLICATION► Step 1Step 1

Unwinding the double helixUnwinding the double helix► Step 2Step 2

Synthesis of DNA segmentsSynthesis of DNA segments Okazaki fragment - a DNA fragment produced Okazaki fragment - a DNA fragment produced

during replication as a result of strand growth in a during replication as a result of strand growth in a direction away from the replication forkdirection away from the replication fork

► Step 3Step 3 Closing the nicksClosing the nicks An enzyme called DNA ligase catalyzes this final An enzyme called DNA ligase catalyzes this final

stepstep Replication occurs simultaneously at many points Replication occurs simultaneously at many points

on the DNAon the DNA Page 660 fig 21.12Page 660 fig 21.12

PCRPCR

► Laboratory technique to mimic replicationLaboratory technique to mimic replication► Using a buffered solution with DNA Using a buffered solution with DNA

polymerase, cofactor MgClpolymerase, cofactor MgCl22, the four , the four nucleotide building blocks, and primers the nucleotide building blocks, and primers the PCR mixture is taken through three stepsPCR mixture is taken through three steps

► Heat for several minutes to unravel the DNAHeat for several minutes to unravel the DNA► Cool tube for several minute, this causes the Cool tube for several minute, this causes the

primers to hydrogen bond to the DNAprimers to hydrogen bond to the DNA► Tube is heated for several minutes and the Tube is heated for several minutes and the

DNA polymerase synthesizes a new strandDNA polymerase synthesizes a new strand

RNARNA► RNA differs from DNA in two waysRNA differs from DNA in two ways

Sugar unitSugar unit RNA has uracil instead of thymineRNA has uracil instead of thymine RNA are single-stranded except in virusesRNA are single-stranded except in viruses RNA do contain regions of double-helical loopRNA do contain regions of double-helical loop Found throughout the cellFound throughout the cell

► Three types of RNAThree types of RNA Messenger RNA (mRNA) - carries genetic Messenger RNA (mRNA) - carries genetic

information from the DNA in the cell nucleus to the information from the DNA in the cell nucleus to the site of protein synthesis in the cytoplasmsite of protein synthesis in the cytoplasm► Has a short lifetime - usually less than an hourHas a short lifetime - usually less than an hour

Ribosomal RNA (rRNA) - constitutes about 65% of Ribosomal RNA (rRNA) - constitutes about 65% of the material in ribosomes, the sites of protein the material in ribosomes, the sites of protein synthesis synthesis ► Ribosome - a sub cellular particle that serves as Ribosome - a sub cellular particle that serves as

the site of protein synthesis in all organismsthe site of protein synthesis in all organisms

ContinueContinue► Transfer RNA (tRNA)Transfer RNA (tRNA)

Delivers individual amino acid molecules to the site Delivers individual amino acid molecules to the site of protein synthesisof protein synthesis

Anticodon - a three-base sequence in tRNA that is Anticodon - a three-base sequence in tRNA that is complementary to one of the codons in mRNAcomplementary to one of the codons in mRNA

► Page 663 fig 21.14Page 663 fig 21.14► Central dogma of molecular biologyCentral dogma of molecular biology

The well-established process by which genetic The well-established process by which genetic information stored in DNA molecules is expressed in information stored in DNA molecules is expressed in the structure of synthesized proteinsthe structure of synthesized proteins

► There are two steps involved to flow genetic There are two steps involved to flow genetic information information

► Transcription and translationTranscription and translation► In eukaryotes the DNA containing the stored In eukaryotes the DNA containing the stored

information is in the nucleus and protein synthesis is in information is in the nucleus and protein synthesis is in the cytoplasmthe cytoplasm

TRANSCRIPTION AND TRANSLATIONTRANSCRIPTION AND TRANSLATION

► TranscriptionTranscription The transfer of genetic information from a DNA molecule The transfer of genetic information from a DNA molecule

to a molecule of messenger RNAto a molecule of messenger RNA► TranslationTranslation

The conversion of the code carried by messenger RNA into The conversion of the code carried by messenger RNA into an amino acid sequence of a proteinan amino acid sequence of a protein

► Transcription: RNA synthesisTranscription: RNA synthesis RNA polymerase catalyzes the synthesis of RNARNA polymerase catalyzes the synthesis of RNA The DNA helix begins to unwind just before the gene that The DNA helix begins to unwind just before the gene that

needs to be transcribed (only one DNA strand is needs to be transcribed (only one DNA strand is transcribed)transcribed)

One sequence of bases is recognized as the starting point. One sequence of bases is recognized as the starting point. MRNA is synthesized in the 5' to 3' direction MRNA is synthesized in the 5' to 3' direction

It runs until it reaches another sequence of bases the is a It runs until it reaches another sequence of bases the is a termination pointtermination point

The mRNA molecule move away and the DNA rewindsThe mRNA molecule move away and the DNA rewinds Example 21.2 page 665Example 21.2 page 665

ContinueContinue► IntronIntron

A segment of a eukaryotic DNA molecule that A segment of a eukaryotic DNA molecule that carries no codes for amino acidscarries no codes for amino acids

► ExonExon A segment of a eukaryotic DNA molecule that is A segment of a eukaryotic DNA molecule that is

coded for amino acids coded for amino acids ► Heterogeneous nuclear RNA (hnRNA) Heterogeneous nuclear RNA (hnRNA)

RNA produced when both introns and exons of RNA produced when both introns and exons of eukaryotic cellular DNA are transcribedeukaryotic cellular DNA are transcribed

► hnRNA undergoes a series of enzyme-catalyzed hnRNA undergoes a series of enzyme-catalyzed reactions that cut and splice the hnRNA to produce reactions that cut and splice the hnRNA to produce mRNAmRNA

► Page 667 fig. 21.18Page 667 fig. 21.18

GENETIC CODEGENETIC CODE► There are sequences of three bases in the mRNA, There are sequences of three bases in the mRNA,

there are 64 possible combinationsthere are 64 possible combinations► CodonCodon

A sequence of three nucleotide bases that A sequence of three nucleotide bases that represents a code word on mRNA moleculesrepresents a code word on mRNA molecules

► With very few exceptions a given amino acid is With very few exceptions a given amino acid is coded by the same codon in every organismcoded by the same codon in every organism

► Most amino acids are represented by more than one Most amino acids are represented by more than one codon this is called DEGENERACYcodon this is called DEGENERACY

► No single codon can represent more than one amino No single codon can represent more than one amino acidacid

► 61 out of 64 base triplets represent amino acids, the 61 out of 64 base triplets represent amino acids, the other three (UAA, UAG, UGA) are signals to chain other three (UAA, UAG, UGA) are signals to chain terminationtermination

► AUG is the only start codon if it is the first codon in a AUG is the only start codon if it is the first codon in a sequencesequence

TRANSLATIONTRANSLATION► There are three major stages of protein synthesisThere are three major stages of protein synthesis

Initiation of the polypeptide chain - ribosomes are Initiation of the polypeptide chain - ribosomes are made up of a large subunit and a small subunit. made up of a large subunit and a small subunit. The initiation process begins when the mRNA is The initiation process begins when the mRNA is aligned on the surface of the small subunitaligned on the surface of the small subunit

Elongation of the chain - a second site, called the Elongation of the chain - a second site, called the A site (aminoacyl site), is located on the mRNA-A site (aminoacyl site), is located on the mRNA-ribosome complex next to the P site. The A site is ribosome complex next to the P site. The A site is where the tRNA comes to release the amino acidwhere the tRNA comes to release the amino acid

Termination of the polypeptide - when a stop Termination of the polypeptide - when a stop codon is reached the chain is terminated by a codon is reached the chain is terminated by a termination factor binding to the stop codontermination factor binding to the stop codon

Page 671-672Page 671-672 Learning check page 672Learning check page 672

► Read pages 673 to 678 some of this will be on the Read pages 673 to 678 some of this will be on the testtest

NUTRITIONAL NUTRITIONAL REQUIREMENTSREQUIREMENTS

► Read pages 684-693 this will be on the testRead pages 684-693 this will be on the test► Cellular respirationCellular respiration

Entire process involved in the use of oxygen by cellsEntire process involved in the use of oxygen by cells Glucose + OGlucose + O22(g) ---> CO(g) ---> CO22(g) + H(g) + H22O(l) + energyO(l) + energy Fig 22.10 page 694Fig 22.10 page 694

► MetabolismMetabolism The sum of all reactions occurring in an organismThe sum of all reactions occurring in an organism

► CatabolismCatabolism All reactions involved in the breakdown of All reactions involved in the breakdown of

biomoleculesbiomolecules► AnabolismAnabolism

All reactions involved in the synthesis of All reactions involved in the synthesis of biomoleculesbiomolecules

► Metabolic pathwayMetabolic pathway A sequence of reactions used to produce one A sequence of reactions used to produce one

product or accomplish one processproduct or accomplish one process

CATABOLISMCATABOLISM► Three stagesThree stages

Digestion - large molecules are chemically Digestion - large molecules are chemically broken into small ones. Most common reaction is broken into small ones. Most common reaction is hydrolysishydrolysis

Small molecules from digestion are degraded to Small molecules from digestion are degraded to even smaller units -primarily two carbon acetyl even smaller units -primarily two carbon acetyl portion of acetyl coenzyme A. Some energy is portion of acetyl coenzyme A. Some energy is releasedreleased

The citric acid cycle followed by electron The citric acid cycle followed by electron transport and oxidative phosphorylation - transport and oxidative phosphorylation - COMMON CATABOLIC PATHWAY -ATP is formed COMMON CATABOLIC PATHWAY -ATP is formed (body’s form of energy)(body’s form of energy)

Page 696 fig 22.11Page 696 fig 22.11

ATPATP► At the cells pH all protons in ATP are ionized (has a At the cells pH all protons in ATP are ionized (has a

charge of 4-)charge of 4-)► Other triphosphates can form from the other basesOther triphosphates can form from the other bases► A transfer of a phosphate group to water releases A transfer of a phosphate group to water releases

energy (this is free energy ∆G)energy (this is free energy ∆G)► ATP-ADP cycleATP-ADP cycle

In biological systems, ATP functions as an In biological systems, ATP functions as an immediate donor of free energy rather than as a immediate donor of free energy rather than as a storage formstorage form

► Mitochondria - a cellular organelle where reactions Mitochondria - a cellular organelle where reactions of the common catabolic pathway occur. Enzymes of the common catabolic pathway occur. Enzymes the catalyze the formation of ATP are found herethe catalyze the formation of ATP are found here

ContinueContinue

►Mitochondrion contains and inner and Mitochondrion contains and inner and outer membraneouter membrane The inner membrane are called cristae The inner membrane are called cristae

and the space surrounding it is called the and the space surrounding it is called the matrix. The enzymes are found in the matrix. The enzymes are found in the inner membrane. The enzymes to the inner membrane. The enzymes to the citric acid cycle are found in the matrixcitric acid cycle are found in the matrix

► Read about the following coenzymes: Read about the following coenzymes: coenzyme A, NADcoenzyme A, NAD++, and FAD these will , and FAD these will be on the test pages 700-705be on the test pages 700-705