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Biology Lesson 1 – Chemistry Review and Enzymes
ThermodynamicsH S -TΔS
- + - Spontaneous at all temperatures
+ - + Non-spontaneous at all temperatures
- - + Spontaneous at low temperatures
+ + - Spontaneous at high temperatures
G = H - T S
G = G + RTlnQ
G = -RTlnK eq
Kinetics
Catalyst – speeds up a reaction by lowering the activation energy by providing an alternate mechanism
(pathway) for the reaction to occur
A catalyst lowers the Ea in both directions, is not consumed in a rxn, and does not shift the equilibrium.
Reaction Coordinate Diagrams
Enzyme KineticsMichaelis-Menton Kinetics
Higher Km, lower affinity for substrate
Substrate Specificity
G1
G>0 K eq> 1 Products favored at eq.
K
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Competitive Inhibition-Inhibitor binds to the active site
-Changes K m but not Vmax
Non-competitive Inhibition-Inhibitor binds somewhere other than the active site
-Changes Vmax not K m
CooperativitySigmoidal curve
Hemoglobin vs. myoglobin
Bohr Effect - H+ and CO2 decrease the affinity of
hemoglobin for O2
Enzyme Regulation
1) Allosteric Regulation (ex. feedback inhibition)
2) Phosphorylation (covalent modification)-Ser, Thr, and Tyr residues can be phosphorylated by kinases (use ATP hydrolysis) or phophorylases
-Phosphatases dephosphorylate enzymes
-Phosphorylation can either activate or inhibit an enzyme depending upon the enzyme3) Zymogens – inactive precursors that become active upon proteolytic cleavage
4) Cofactors – involvement of metal ions or organic molecules (coenzymes)5) Association with other peptides
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Biology Lesson 2 – Cellular MetabolismMetabolism
Catabolism vs. Anabolism
Oxidation/Reduction
Catabolism of Glucose (oxidation of glucose):
C6H12O6 + 6O2 → 6CO2 + 6H2O
Anaerobic Catabolism of Glucose1) Glycolysis (cytosol) – substrate-level phosphorylation
2) Fermentation (production of ethanol) or production of lactate
Aerobic Catabolism of Glucose1) Glycolysis (cytosol) – substrate-level phosphorylation
2) PDC (Mitochondrial Matrix)
3) Kreb’s Cycle (Mitochondrial Matrix)4) Electron Transport Chain (Mitochondrial Inner Membrane) – oxidative phosphorylation
Mitochondrial Structure
Outer membrane, intermembrane space, inner membrane, matrix
Regulation of Glycolysis
ENZYME ACTIVATED BY INHIBITED BYHexokinase Glucose-6-P (minor)
PFK-1 AMPFructose-6-P
Fructose-2,6-BP (liver)
Insulin
ATP
Fructose-1,6-BP
Citrate
Glucagon
Pyruvate Kinase AMP
Fructose-1,6-BP
ATP
Acetyl CoA
Phosphorylation
Alanine
Gluconeogenesis – Production of glucose; the reverse of glycolysis (uses a few different enzymes)-occurs mainly in the liver (but also the kidneys)
Glycogen Metabolism – glucose polymer for glucose storage in the liver and muscles
-insulin activates glycogen synthesis-glucagon and epinephrine promote degradation
Cori cycle – lactate transported to the liver for conversion back to glucose
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Glucose Catabolism
Glycolysis
(cytosol)
Glucose
(6C)
2ATP 2ADP
4ADP 4ATP 2NADH2NAD+
2 Pyruvate
(3C)2NADH2NAD+
2CO2
2 Acetyl-CoA
(2C)( ach e)
T
(K
FAD FA
GDP GT
ADP AT
1 f or e pyruvat
(1 for each pyruvate)
(
Lactate(3C)
Ethanol + CO2
N A D +
N A D H N A D H
N A D +
A n a e r o b i c
C o n d i t i o n s
Electron
Transport
Chain
NAD+NADH FADH2 FAD1/2O2+2H
+
H
+ e-e-
e-
intermembrane space
high [H+]
Yield Per
Glucose2ATP
2GTP
10NADH2FADH2
25ATP
3ATP
32ATP Total*
1NADH = 2.5 ATP
1FADH2 = 1.5 ATP
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Glucose
Glucose-6-Phosphate (G-6-P)
Fructose-6-Phosphate (F-6-P)
Fructose-1,6-Bisphosphate (FBP)
Glyceraldehyde-3-P (G-3-P)
1,3-Bisphosphoglycerate (BPG)
3-Phosphoglycerate (3-PG)
2-Phosphoglycerate (2-PG)
Phosphoenolpyruvate (PEP)
Pyruvate
Dihydroxyacetonephosphate (DHAP)
Glyceraldehyde-3-P (G-3-P)
1,3-Bisphosphoglycerate (BPG)
3-Phosphoglycerate (3-PG)
2-Phosphoglycerate (2-PG)
Phosphoenolpyruvate (PEP)
Pyruvate
ATP
ATP
ATP ATP
ATPATP
ADP
ADP
ADP ADP
ADPADP
NAD+NADH
NAD+NADH
Hexokinase
Glucosephosphate
Isomerase
Aldolase
Triosephosphate
Isomerase
Glyceraldehyde-3-Phosphate
Dehydrogenase
Phosphoglycerate
Kinase
Phosphoglycerate
Mutase
Enolase
Pyruvate
Kinase
Major
Regulatory
Step
H2OH2O
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TCA Cycle (Kreb’s Cycle or Citric Acid Cycle)
Regulation of the TCA Cycle
ENZYME ACTIVATED BY INHIBITED BYCitrate Synthase ADP
Acetyl-CoACitrateSuccinyl-CoA
ATP and NADH (lesser extent)
Isocitrate Dehydrogenase ADP
Ca2+
ATP and NADH (minor)
-Ketoglutarate Dehyrogenase ADPCa
2+
Succinyl-CoA NaDH
ATP (minor)
Pyruvate Carboxylase Acetyl-CoA
Overall Regulation of Glucose MetabolismLow ATP/ADP and NADH/NAD
+ Ratios – Catabolism activated and Biosynthesis inhibited
High ATP/ADP and NADH/NAD+ Ratios – Biosynthesis activated and Catabolism inhibited
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Electron Transport Chain
1NADH = 2.5 ATP
1FADH2 = 1.5 ATP
Chemiosmosis – The electron transport chain establishes a proton gradient (establishing an electrochemical pote
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Lipid Metabolism
Dietary Intake to Storage
Triacylglycerides converted to fatty acids and monoacylglycerides for absorption out of the small intestine.
Reassembled into triacylglycerides and transported via chylomicrons to adipose tissue for storage.
From Adipose Tissue to Energy Production
Triacylglycerides converted to fatty acids and glycerol by hormone-sensitive lipases
-Activated by glucagon and epinephrine in response to fasting, exercise, or stress-Glycerol transported to liver for glycolysis or gluconeogenesis
-Fatty acids transported through the bloodstream to tissues in need (heart and muscles primary)
-oxidation
-Unsaturated fatty acids produce 1 less FADH2 for each double bond
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O
O
SCoA
O
Catabolism of Stearic Acid (18C)
9 Acetyl CoA
8 NAD+
8 NADH
8 FAD
8 FADH2
27 NAD+
27 NADH
9 FAD
9 FADH2
18 CO2
CAC Cycle
ATP
AMP + PPi 2Pi
(Equivalent to 2ATP consumed)
9 GDP
9 GTP
(equal to 9ATP)
8 Rounds of -oxidation
NADH FADH2 ATP
-oxidation 8 8 -2
CAC Cycle 27 9 9Total 35 (= 87.5 ATP) 17 (= 25.5 ATP) 7 TOTAL: 120 ATP
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Photosynthesis
6CO2 + 6H2O→ C6H12O6 + 6O2
Light reactions take place in the thylakoid membrane.
Dark reactions take place in the stroma.
Chlorophylls absorb red light (600-700nm) and blue light (400-500nm).
Antennae chlorophyll molecules pass light energy to reaction centers.
Photophorphorylation
Photosystems are part of an electron transport chain that creates a proton gradient.
The proton gradient powers ATP synthase.
Chloroplasts
Light Reactions
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Dark Reactions (Calvin Cycle)
Ribulose-1,5-bisphosphate
(5C)
3-Phosphoglycerate
(3C)
Glyceraldehyde-3-phosphate
(3C)
Dihydroxyacetone phosphate
(3C)
Glyceraldehyde-3-phosphate
(3C)
3 CO2 + H2O
6 ATP
6 ADP
6 NADPH
6 NADP+
3 ATP
3 ADP
Glycolysis
Carbohydrates
stay in the cycle
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Biology Lesson 3 – Molecular Biology
DNA and RNA
Nucleoside (ribose + base) vs. nucleotide (ribose + base + 3 phosphates)
Purines (guanine and adenine) and pyrimidines (cytosine, thymine, and uracil)
Nucleoside
NH
O
ON
O
HOH
HH
HH
OPO
O-
O
PO
O-
O
P-O
O-
O
sugar
base
triphoshpate
Nucleotide
N
NH
NH2
OC
NH
NH
O
OT
NH
NH
O
OU
Pyrimidines
(CUT the PY)
DNA double helix (right-handed helix)Antiparallel strands
Complementary
Held together by H-bonding
Base stacking
Watson-Crick base pairing
G-C: 3 Hydrogen bondsA-T: 2 Hydrogen bonds
Chromosome Organization
Prokaryotes - One circular chromosome (supercoiled by DNA gyrase)
Eukaryotes – Many linear chromatin (called chromosomes when condensed during mitosis)Wrapped around nucleosomes (histone octamers)
Have centromeres and telomeres
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Replication (Making DNA from a DNA template)1) Helicase unwinds DNA helix and separates strands forming the replication fork at the origin.
Topoisomerase ‘unravels’ DNA ahead of the replication bubble to relieve tension.
2) Single-strand binding proteins bind and stabilize the single stranded DNA.
3) Primase lays RNA primers on the leading (only once) and lagging strand (many times).
4) DNA polymerase (III*) elongates new strands complementary to the leading strand (continuously) and thelagging strand (discontinuously) in the 5’ 3’ direction (for both).The fragments on the lagging strand are called Okazaki fragments.
5) DNA ligase joins the Okazaki fragments together (seals the backbone).
6) DNA Polymerase (Pol I*) replaces the RNA primers with DNA
Semiconservative – new DNA has one ‘parent’ strand and one ‘daughter’ strand
Replication of the telomeres (by telomerase) in eukaryotes
Energy provided by breaking high energy phosphate bonds during formation of phosphodiester linkages.
Reverse Transcriptase – polymerase in retroviruses that synthesizes DNA from an RNA template
Prokaryotic DNA polymerases
DNA Pol Function Exonuclease Activity
DNA Pol I Replace Primers and DNA repair 3’ to 5’ and 5’ to 3’ exonuclease
DNA Pol II ??? SOS ??? ???DNA Pol III Primary pol for elongation 3’ to 5’ exonuclease
Differences between Prokaryotes and Eukaryotes
Prokaryotes Eukaryotes
1 Circular chromosome Many linear chromatin
Supercoiled (by DNA gyrase) Wrapped around nucleosomes (histone octamers)
1 origin of replication Many origins of replicationBi-directional Bi-directional
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DNA Repair
Proofreading – 3’5’ exonuclease can remove the last nucleotide if an error occurs during replication.
Nick Translation – 5’3’ exonuclease activity of DNA Pol I following replication
Mismatch Repair – DNA is methylated prior to replication (prokaryotes); this allows for the parent strand
(methylated) and daughter strand (not methylated) to be distinguished after replication and
any errors during replication in the daughter strand to be repaired.Several enzymes and proteins are involved.
1) The area around the mismatch is removed on the daughter strand.
2) DNA Pol III fills in the gap.3) DNA ligase seals the backbone.
Base-excision Repair – 1) A damaged base is removed leaving an AP site.2) An AP endonuclease removes the rest of that nucleotide.
3) An exonuclease removes several more nucleotides.4) DNA Pol I fills in the gap.
5) DNA ligase seals the backbone.
Nucleotide-excision Repair – most common form of repair for damage caused by UV light.1) The area around the damage is removed.
2) DNA Pol I fills in the gap.
3) DNA ligase seals the backbone.
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Protein Synthesis
Prokaryotes
Eukaryotes
Transcription (Making RNA from a DNA template)
1) RNA Pol binds promoter region and begins unzipping DNA.Promoter region contains a -35 sequence and Pribnow box in prokaryotes.
Promoter region often contains a TATA box in eukaryotes.
2) RNA Pol begins transcribing (forming complementary RNA) at the start site (5’ 3’ direction).It is the template (or non-coding) strand only that is being transcribed.
3) Transcription is terminated at a special sequence.
Template Strand (Non-coding, anti-sense) vs. Coding Strand (Sense)Transcription is the principle site of gene regulation.
Gene – a DNA sequence encoding for a protein.Monocistronic (eukaryotes) vs. polycistronic (prokaryotes)
Prokaryotes Eukaryotes1 RNA polymerase 3 RNA polymerases
(RNA pol I for rRNA – nucleolus)
(RNA pol II for mRNA)
(RNA pol III for tRNA)
Promoter is -35 sequence and
Pribnow box (-10)
Promoter is often TATA box (-25)
Occurs in the cytoplasm Occurs in the Nucleus
Coupled transcription/translation Not coupled (Occur in separate compartments)
No mRNA processing 5’CAP, poly A tail, splicing out introns
Lac Operon (Transcription Regulation)The Lac genes allow for the catabolism of lactose.
The repressor binds to operator preventing transcription.Lactose binds the repressor removing it from the operator.
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Translation (Making a peptide from mRNA)1) Initiation – Small ribosomal subunit binds to mRNA near the 5’ end (along with many initiation factors).
Shine-Dalgarno sequence at -10 in prokaryotes; other sequences in eukaryotes
2) Met-tRNA (fMet in prokaryotes) binds to the start codon (AUG) via its anticodon – will be the P site.
Aminoacyl site (A site), peptidyl site (P site) and exit site (E site)
3) Large ribosomal subunit binds.
4) Elongation - 2nd
charged tRNA binds at the A site (requires GTP hydrolysis).
5) Ribosome catalyzes peptide bond formation.
6) Translocation (APE) – requires GTP hydrolysis.
7) Termination – release factor binds when stop codon appears in the A site.
rRNA, tRNA, and mRNA
Charging tRNA requires ATP hydrolysis.
Ribosomes – 70S (50S&30S) in prokaryotes and 80S (60S&40S) in eukaryotes)
Eukaryotic RNA polymerases
RNA pol I rRNA
RNA pol II mRNARNA pol III tRNA
Post-translational modifications may be made at the ER or Golgi body.
Genetic Code: Degenerate
Replication Transcription Translation
Begins at Origin of Replication Start Site
(upstream promoter region)
Start Codon(AUG)
(upstream Shine-
Dalgarno seq (prokacts as ribosome
binding site)
Elongation Enzyme DNA Polymerase RNA Polymerase Ribosome
Where occurs (prokaryotes) Cytoplasm Cytoplasm Cytoplasm
Where occurs (eukaryotes) Nucleus Nucleus Cytoplasm
Genetic Code Start CodonAUG
Stop Codons
UGA – U Go AwayUAA – U Are Away
UAG – U Are Gone
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Molecular Biology Techniques
PCR (Polymerase Chain Reaction) – DNA amplification
1) Denaturation – DNA strands are separated with heating (>90C)
2) Annealing – The sample is cooled (~55C) to allow primers specific to the target sequence to anneal tothe template strands of the target sequence.
3) Elongation – Taq polymerase replicates the templates (~70C)
4) ‘Thermal cycling” is repeated many times.
Restriction Enzymes – endonucleases that cut dsDNA at a specific sequence leaving either sticky ends or blunt
ends.Eco RI cuts at the palindromic sequence 5' GAATTC 3'
Gene Cloning – Transferring a gene from one cell to another to impart the gene’s function.
Plasmids – small circular dsDNA that has an origin of replication, many restriction sites, andoften antibiotic resistance and a promoter.
A gene is inserted into a plasmid using restriction enzymes and DNA ligase.
The plasmid is used to ‘transform’ bacteria (bacteria take up the plasmid).
Can also be used in eukaryotes as well (needs eukaryotic promoter and poly A signal).
Hybridization – DNA microarrays can be used to detect the presence and amount of specific DNA or RNA
sequences1) PCR (DNA with Taq polymerase; RNA with Reverse Transriptase)
2) DNA is denatured and single strands are allowed to anneal (when complementary) to singlestranded ‘probe’ DNA on an array
3) A marker (often a fluorophore) allows for the detection and quantification of hybridized sequences.
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Biology Lesson 4 – Genetics and Evolution
Genetics
Gene – genetic material coding for a single gene product (peptide, rRNA or tRNA)
Locus – the chromosomal location of a geneAllele – one variant of a gene
Homologous chromosomes – chromosomes that code for the same set of genes (but may have different alleles),
one received from each parent
Genotype vs. phenotype
Law of segregation – separation of alleles in the haploid gametes
Law of independent assortment – genes assort independently to the progeny
Homozygous vs. heterozygous
“Pure breeding” or “True-breeding” strain
Dominant vs. recessive
Complete Dominance –when a heterozygote has the phenotype of only 1 of the alleles (the dominant one)
Incomplete dominance – phenotypes of the progeny are blends of the parental phenotypes
(ex. snap dragons – homozygous red crossed with homozygous white gives pink progeny)
Codominance – both inherited alleles are completely expressed (ex. blood types – ABO)
1) Homozygous yellow peas (dominant) are crossed with homozygous green peas (recessive). The F1
generation is then self-crossed. What will be the phenotypic ratios in the F2 generation?
2) For peas, yellow is dominant to green and round is dominant to wrinkled. Two heterozygous yellow, round
pea plants are crossed (YyRr ). What are the phenotypic ratios in the F1 generation?
3) How would you figure out if a yellow pea plant had the homozygous or heterozygous genotype?
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Pleiotropism – when a gene has multiple phenotypes associated with its expression
Polygenism – when multiple genes affect a trait
Penetrance – probability an organism with a specific genotype will express a particular phenotype
Expressivity – term describing the variation of phenotype for a specific genotype
Epistasis – occurs when the expression of a gene is dependent upon another gene
Autosomes vs. sex chromosomes (X and Y)
Sex-linked Genes
Y-linked traits – rare as there are very few genes on the Y-chromosomeAll Y-linked disorders are passed on to all male offspring (but to no female offspring)
X-linked traits – males only receive a single copy of the X-chromosome from their mother
Mitochondrial inheritance from the mother – any genetic disorders coded by the mitochondrial DNA will be passed on to all offspring
Turner Syndrome (X) – offspring (female) have only a single X chromosome resulting from nondisjunctionKleinfelter Syndrome (XXY) – offspring (male) have an extra X chromosome resulting from nondisjunction
3) Color-blindness is the result of an X-linked recessive allele. What is the probability that a colorblind fatherand a normal mother (homozygous) have a colorblind child (son or daughter)?
4) What is the probability that a heterozygous mother (a carrier) and a normal father have a colorblind
daughter? A color blind son?
MutationsMost mutations are deleterious to the cell.
Point mutation (substitution, insertion, deletion) – change of a single nucleotideMissense mutation –point mutation leading to a codon coding for a different amino acid
Nonsense mutation – point mutation leading to a stop codon
Frame-shift mutations – insertion or deletion leading to a change in the reading frame of a gene
Mutations in replication – low level of ‘natural’ mutations that occur during replication
Mutagens and carcinogens – agents causing mutation (carcinogens when they cause cancer)
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Interphase
G1
S
Protein and nucleic acid synthesis to prepare for replication; production of organelles
DNA Replication
Prophase I Longest phase
Chromosomes condense and tetrad formation (homologous pairs)
Recombination
Disappearance of the nuclear envelope and polarization of the centrioles (MTOCs)
Metaphase I Chromosomes line up on metaphase plate
Spindle fibers attach at centromeres via kinetochores
Anaphase I Spindle fibers pull homologous chromosomes apart towards the centrioles
Cleavage furrow begins forming
Telophase I Nuclear membranes reform
Completion of cytokinesis
Prophase II Chromosomes condense
Disappearance of the nuclear envelope and polarization of the centrioles (MTOCs)
Metaphase II Chromosomes line up on metaphase plate
Spindle fibers attach at centromeres via kinetochores
Anaphase II Spindle fibers pull sister chromatids apart towards the centrioles
Cleavage furrow begins forming
Telophase II Nuclear membranes reform
Completion of cytokinesis
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Nondisjunction – failure of tetrads to separate during meiosis I or sister chromatids in meiosis II(ex. Down syndrome—trisomy 21)
(ex. Turner Syndrome (X) – only a single X chromosome)
(ex. Kleinfelter Syndrome (XXY) – an extra X chromosome)
Translocation – movement of a segment of one chromosome to another non-homologous chromosome
(ex. Down syndrome – chromosome 21 14)
Recombination (single and double crossovers)
Linked genes – genes on the same chromosome that probably will not undergo independent assortment-the closer together on the chromosome the greater the linkage between genes
-the likelihood of recombination increases with distance between genes
5) Lets say that the color and size gene for an organism lie on the same chromosome:
B = blue, b = green, L = large, l = small
Two organisms that are heterozygous for bothcolor and size with the dominant alleles paired on onechromosome and the recessive alleles paired on the other are crossed and the offspring are as follows:
Phenotype Number
Blue and Large 70Blue and Small 3
Green and Large 4
Green and Small 23
Which are the recombinant phenotypes?
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Population GeneticsHardy-Weinberg Equilibrium – allele frequencies remain constant in a gene pool for a population in equilbrium
p + q = 1Assumptions for equilibrium
1. Random mating
2. No mutations
3. No selection (natural or otherwise)
4 No migration
5. Large population size No enetic drift
p = frequency of dominant alleleq = frequency of recessive allele
p2 + 2pq + q
2 = 1
p
2
= frequency of homozygous dominant genotype2pq = frequency of heterozygous genotype
q2 = frequency of homozygous recessive genotype
Evolution
Fitness – the ability of an organism to pass on its alleles
Natural Selection – differential reproduction of an organism based upon fitness in its environment
1) Stabilizing Selection – Selection against the extremes (for the averages)
2) Directional Selection – Selection against one extreme (but favoring the opposite extreme)3) Disruptive (Divergent) Selection – Selection against the averages (for the extremes)
4) Artificial Selection – directional selection done by humans with selecting for traits in animals and crops
5) Sexual Selection – Differential mating between males and females
Species – organisms that are capable of reproduction of ‘fit’ offspring
SpeciationPolymorphism – when multiple phenotypes exist within a population
Adaptation – an inherited trait that confers greater fitness
Specialization – an adaptation to a specific function or environment
Inbreeding –increased likelihood of mating between organisms with similar genotypes (limits genetic variation)
Outbreeding - increased likelihood of mating between organisms with different genotypes
Genetic Drift – random change in allele frequencies in a population
-smaller populations are more susceptible to genetic drift
Bottleneck – dramatic decrease in size of a population making it susceptible to genetic drift
Ontogeny and Phylogeny – Similarities in stages of development (ontogeny) can be used to determine
evolutionary relationships between organisms.
Convergent Evolution – two species possess the same analogous structures unrelated to a common ancestor
Divergent Evolution – divergent leading to distinct populations/speciesParallel Evolution – similar evolutionary changes in different species due to similar environmental pressures
Symbiosis1) Parasitism – when a species requires another species as a host to live, harming the host in the process
2) Commensalism – an organism requires another species as a host to live, but doesn’t harm or benefit the host
in the process
3) Mutualism – symbiotic relationship between two organisms that confers fitness on both
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Origin of Life – Prebiotic Soup?—I decided not to present the current scientific beliefs regarding this topic as Isimply don’t have a lot of faith in them. But it is still required material and I’ll let you find another resource
for this section. My apologies.
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Biology Lesson 5 - MicrobiologyViruses
Non-living, parasitic, infectious agent that can only replicate within a host cell.
-Viruses infect every type of living organism (plant, animal, bacteria, archaebacteria).-Structure - nucleic acid encased in a protein capsid (enveloped or nonenveloped)
-Genome can be linear or circular and can be either dsDNA, ssDNA, dsRNA, or ssRNA.
-Relatively small genomes that can often be read in different reading frames.-Typically uses host’s replication, transcription, and translation machinery.
-Much smaller than prokaryotic or eukaryotic cells
Bacteriophage Life Cycles
Lytic Cycle
1) Adsorption – Bind cell surface via tail (host cell specific interactions)
2) Penetration – puncture cell wall and membrane and inject genome into the host cell
3) Hydrolase (a viral gene product) is produced and degrades the host’s genome.4) Replication of the viral genome (many copies) and synthesis of much capsid protein
5) Assembly of new virus particles6) Production of lysozyme to degrade the cell wall resulting in cell lysis and release of virus particles.
Lysogenic Cycle
1) Adsorption – Bind cell surface via tail (host cell specific interactions)2) Penetration – puncture cell wall and membrane and inject genome into the host cell
3) Integration of the phage genome into the host genome
4) Dormancy – viral genes not expressed by viral genome is transmitted to all progeny during cell division5) Activation – excision of viral DNA and entrance into the lytic cycle
Animal cell viruses have similar cycles to the lytic and lysogenic.Viruses of eukaryotes often have a lipid bilayer envelope and enter the host cell via endocytosis and exit by
budding out of the host cell.
Host cells contain restriction enzymes that will degrade viral DNA. Bacteria methylate their own DNA to
distinguish it from foreign DNA.
Transduction – transfer of genetic material via a virus in the lysogenic cycle.
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Virus Types (by genome)
[+] RNA viruses – viral genome is ssRNA which can also serve directly as mRNA
-must code for an RNA-dependent RNA polymerase for viral replication
[-] RNA viruses – viral genome is ssRNA which is anti-sense (-) and therefore complementary to the mRNA
coding for the viral genes.
Must code for an RNA-dependent RNA polymerase and include this polymerase in its capsidto be infectious
[+] RNA
(can serve
as mRNA)
[-] RNA [-] RNA
(assembled
into capsids
for new viruses)
RNA-dep
RNA Pol
RNA-dep
RNA Pol
viral proteins
t r a n
s l a t i o
n
Retroviruses – [+] RNA viruses that convert their genomes into dsDNA for incorporation into the host’sgenome; must encode an RNA-dependent DNA polymerase (reverse transcriptase)
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Prokaryotes
cilia
flagellum
ribosomes
plasmid
supercoiled
circular
chromosome
plasma membrane
cell wall
-Single circular dsDNA genome and possibly the presence of a plasmid(s).-No nucleus, membrane bound organelles or mitotic apparatus.
-Coupled transcription and translation.
Eubacteria vs. Archaebacteria
Classifications of Bacteria
cocci
(spherical)bacilli
(rod-shaped)
spirilla
(spiral-shaped)
Gram Positive Bacteria – stain dark purple during gram staining
-have cell membrane and cell wall (peptidoglycan)Gram Negative Bacteria – stain pink during gram staining
-have cell membrane, cell wall and outer lipopolysaccharide layer (contains endotoxins)
Flagellar Propulsion – bacterial flagellum used by motile bacteria for locomotion
Chemotaxis- movement is directed toward chemoattractants or away from chemorepellents(sensed by chemoreceptors)
-powered by ATP hydrolysis
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FissionReproduction simply through growth, DNA replication, and cell division.
Doubling times vary but can be as short as 20 minutes under ideal conditions.
Endospores – dormant form produced by some bacteria under harsh conditions.
-have a thick peptidoglycan coat and can survive through extreme conditions
Aerobes – can survive in an oxygen environment
Anaerobes – do not require oxygen to survive
Facultative Anaerobes – Can carry out out metabolic processes with or without oxygen
Conjugation
-way to share genetic information adding to diversity
-common way of conferring antibiotic resistance genes
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Fungi
Eukaryotes including yeast (unicellular) and a variety of multicellular forms.
Have a cell wall made of chitin.
Asexual Reproduction
1) Budding – A fungal cell simply grows out of an existing fungal cell until distinct.
2) Spore Formation – procuded by mitosis, spores will germinate under favorable condition to become active.
Sexual Reproduction
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Biology Lesson 6 – Eukaryotic Cells
Mitochondrial Structure
-PDC and Kreb’s Cycle occur in the matrix-ETC Complexes are located in the inner membrane
-Proton’s are pumped (actively) from the matrix to
the intermembrane space
-ATP synthase is located in the inner membrane andsynthesizes ATP on the matrix side
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Organelle Function
Nucleus DNA storage and site of transcription
Surrounded by a nuclear envelope (2 lipid bilayers) through which nuclear pores regulate
traffic of large moleculesContains the nucleolus (dark spot which is the site of rRNA synthesis)
Ribosomes Translation of mRNA into proteins (present in both pro- and eukaryotes)
Rough ER ER associated with ribosomes that is involved in synthesis and glycosylation of peptides to
form glycoproteins destined for secretion or integration into the membraneSmooth ER Synthesis of lipids (membrane) and hormones often for export from the cell
Breakdown of toxins in liver cells
Golgi Apparatus Modification (glycosylation) and ‘packaging’ of proteins into vesicles for secretion or
transport to cellular destinations (like lysosomes)
Mitochondria Site of ATP synthesis via ATP Synthase as a result of oxidative phosphorylation (PDC,
Kreb’s cycle and the Electron Transport Chain)
Site of fatty acid catabolism (-oxidation)Have their own DNA (circular) and ribosomes for self-replication
Lysosomes Contains acid hydrolases (digestive enzymes) and have pH~5
Degradation of old organelles or phagocytosed materials
Produced from the Golgi Apparatus Not present in plant cells
Peroxisomes Involved in the breakdown (involving hydrogen peroxide) of many substances including,fatty acids, amino acids, and various toxins
Carry out the glyoxalate cycle in germinating plant seeds
Centrioles Source of the spindle apparatus used for cell division (acts as a microtubule organizingcenter a.k.a. MTOC)
Not present in plant cells
Vacuoles Fluid-filled membrane-bound vesicles used for transport, storage of nutrients and other
substances, pumping excess water out of a cell, and cell rigidity (in plants)
Chloroplasts Site of photosynthesis in plant cells
Animal cells have lysosomes and centrioles (not present in plant cells).
Plant cells have cell walls, chloroplasts and a central vacuole (not present in animal cells).
Cell Walls
Bacteria Made of peptidoglycans
Archaebacteria Polysaccharides (not peptidoglycans though)
Fungi Made of chitin
Plant cells Made of cellulose
Animal cells None
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Plasma MembraneFluid Mosaic Model – Components free to move in 2D throughout the membrane
Composed of phoshpolipids, glycolipids and cholesterol
Cholesterol adds rigidity to the membraneUnsaturated fatty acids increase membrane fluidity
Hydrophobic molecules and small polar molecules (uncharged) can cross the membrane
(ex. CO2, O2, lipids (including certain hormones), some drugs)
peripheral
membrane
protein
transmembrane
protein
integral membrane proteinpolysaccharides
Membrane Proteins
Peripheral membrane proteins – adhere to membrane surface via electrostatic interactions
Integral membrane proteins – anchored to and embedded in the membrane
Transmembrane proteins – Spans the membrane and includes channel proteins, carrier proteins, porins
Cell Receptors - recognition glycoproteins on the cell surface that interact with hormones or other molecules
and relay signals into the cell
Adhesion proteins
Gap Junctions – allow exchange of nutrients and cell-to-cell communication (ex. cardiac muscle cells)
Tight Junctions – completely encircles cells and seals the space between them to prevent leakage-(ex. intestinal cells)
Desmosomes – ‘spot welds’ between cells that adhere them to one another and give mechanical strength
-anchored to the cytoskeletons of each cell (ex. skin cells)Plasmodesmata – narrow channels allowing the exchange of nutrients in plant cells
Glycocalyx – carbohydrate coating on the cell wall of some bacteria and the plasma membrane of some animalcells; functions in adhesion, barrier to infection, or cell-cell recognition
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Membrane TransportPassive Transport
1)Simple Diffusion (ex. CO2, O2, lipids, some drugs)
2) Facilitated Diffusion – diffusion of ions/polar solutes via a carrier protein (channel protein) (ex. glucose)
Active Transport - works against the concentration gradient and requires energy (ATP hydrolysis)
1) Primary (ex. Na/K pump—3Na+ pumped out and 2K
+ pumped into cell fueled by ATP hydrolysis)
2) Secondary – uses one solutes gradient (established by ATP hydrolysis) to accomplish the transport of
another (Na+/glucose cotransport)
Cell Signaling and Second Messengers (G-Proteins)1) Ligand binds G-protein receptor
2) G-protein receptor activates G-protein which binds GTP (exchanges GTP for GDP)
3) G-protein activates Adenylate Cyclase (ATP cAMP)
4) cAMP acts as a ‘2nd
messenger’ activating a series of proteins and transcription factors
Osmosis and plasmolysis vs. cytolysis
Hypertonic, hypotonic, isotonic
Exocytosis vs. endocytosis
Phagocytosis and pinocytosis
Receptor-mediated endocytosis
Cytoskeleton
Microtubules – made from tubulin in a 9+2 arrangement-functions as a ‘railroad’ for intracellular transport
-found in the spindle apparatus of mitosis (MTOCs/centrioles) and in flagella and cilia
Intermediate filaments – support and maintain the shape of the cell
Microfilaments – made from actin and involved in cellular motility, muscle contraction, and cytokinesis
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Mitosis
Cell Cycle
G1
G2
S
Inter
M i t o s i s
p r o p
h a s e
m e t a p h
a s e
a n a p h
a s e
t e l o
p h a s
e
hase
Summary of Mitosis
Interphase
G1S
G2
Protein and nucleic acid synthesis to prepare for replication; production of organellesDNA Replication
Continued growth in preparation for mitosis
Prophase Chromosomes condense
Nuclear envelope disappears
Polarization of the centrioles (MTOCs)
Metaphase Chromosomes line up on metaphase plate
Spindle fibers attach at centromeres
Anaphase Spindle fibers pull sister chromatids apart towards the centriolesCleavage furrow begins forming
Telophase Nuclear membranes reform
Completion of cytokinesis
*
*
*
*prophase metaphase
anaphase
telophase
d