Textbook Notes (363,178)
Canada (158,245)
BIOL 201 (1)

Cumulative Biology 201 Notes

48 Pages
Unlock Document

McGill University
Biology (Sci)
BIOL 201
Judy Garner

Chapter 2 Notes Chemical Bonding: Atoms with incomplete valance shells can interact with certain other atoms in a way that each one completes its valance shell by either sharing or transferring electrons Covalent Bonds: Sharing of a pair of valance electrons by two atoms Electronegativity: The attraction of a particular kind of atom for the electrons of a covalent bond - The more electronegative an atom, the more strongly it pulls shared electrons towards itself Non-polar covalent bonds: electrons are shared equally, “tug-of-war” e.g. H2 or double bond O2 Polar covalent bonds: One atom is bonded to a more electronegative atom, the electrons of the bond are not shared equally e.g. H2O (O is more (-) therefore, shared electrons are pulled towards O) Ionic Bonds: Two atoms are so unequal in their attraction for valance electrons that the more electronegative atoms strips an electron completely away from its partner e.g. Sodium Chloride, NaCl; Na 11e- and Cl 7e-, Na loses 1 e- and has 2 valance shells w/ 10e- and Cl gains 1 to complete its 3 valance shell w/ 8e- Hydrogen Bonds: Forms when a H atom covalently bonded to one electronegative atom is attracted to another electronegative atom e.g. H2O and NH3: a hydrogen bond results from the attraction between the partial (+) charged on the H atom of H2O and the partial (-) charged on the N atom of NH3 Chapter 3 Notes Cohesion: - H2O molecules stay close to each other as a result of H bonding - Many of the molecules are linked by multiple H-bonds which makes H2O more structured - Collectively, the H bonds hold the substance together - Cohesion due to H bonding contributes to the transport of H2O and dissolved nutrients against gravity in plants - Results in surface tension Adhesion: - the clinging of one substance to another - H2O to cell walls by H bonds to counter the downward pull of gravity - Important for movement of water through the xylem of plants H2O’s high specific heat: - Heat must be absorbed in order to break H bonds - H2O resists changing its temperature when it absorbs or released heat - When it does change, it absorbs or loses a relatively large quantity of heat for each degree of change Evaporation: - Molecules moving fast enough to overcome the attraction to stay close to one another, can depart the liquid and enter the air as gas - hydrogen bonds must be BROKEN before molecules can exit the liquid - a high amount of energy is required to vaporized H2O - it helps moderate Earth’s climate - severity of steam burns caused by heat energy released when stem condenses into liquid on the skin - As a liquid evaporates, the surface of the liquid that remains behind cools down- (evaporative cooling) Hydrophilic: - Any substance that has an affinity for water -Can be hydrophilic without dissolving (some molecules in cells are so large that they do not dissolve(colloid) and remain suspended in the aqueous solution) e.g. cotton Hydrophobic: - Substances that are non-ionic or nonpolar, or cannot form hydrogen bonds – repel water e.g. vegetable oil, neutral fats, phospholipids, steroids, and waxes pH Scale: measures acidity in a solution - Acid: substance that increases the H ion concentration, proton donors HCl  H(+) + Cl(-) - Base: Substance that reduces the conc. of H ions, proton acceptors NaOH  Na(+) + OH(-) - Buffers: They accept H ions from the solution when they are in excess and donate H ions to the solution when they are depleting (minimize concentration of H+ and OH- in a solution Chapter 5 Notes Polymers: a long molecule consisting of many similar or identical building blocks linked by covalent bonds Monomers: are smaller molecules, the repeating units that serve as the building blocks of a polymer The Synthesis & Breakdown of Polymers - Carbohydrates, proteins and nucleic acids are polymers (chains on monomers). The components of lipids vary - Monomers form longer molecules by dehydration reactions in which water molecules are released - Polymers can disassemble by the reverse process of hydrolysis Carbohydrates: - Monosaccharide(glucose & fructose) & Disaccharide (lactose & sucrose) o Fuel, carbon sources that can be converted to other molecules or combined into polymers - Polysaccharide o Cellulose (plants)  strengthens plant cell walls o Starch (plants)  stores glucose for energy o Glycogen (animals)  stores glucose for energy o Chitin (animals & fungi)  strengthens exoskeleton and fungal cell walls Lipids: - Hydrophobic – they mix partly with water - fat is constructed from 2 kinds of smaller molecules: - Glycerol, an alcohol with 3 carbons - Fatty acid: long carbon skeleton (16-18C in length) - triacylglycerol: important energy source, insulation and cushions organs Saturated Fats: at room temperature, the molecules of fat are packed closely together, forming a solid e.g. animal fats or butter Unsaturated Fats: at room temp, the molecules of fat cannot packed closely enough to solidify because of kinks in some of their fatty acids, hydrocarbon chains e.g. plants or olive oil Phospholipids: The hydrocarbon tails are hydrophobic; however, the phosphate group & its attachment form a hydrophilic head - When added to water, they self-assemble into double-layered aggregates bi- layers that protect the hydrophobic tail and forms a boundary between the cell and its external environment Levels of Protein Structure (Page 82-83) - Primary: the sequence of amino acids in a polypeptide chain o least affected by a disruption in Hydrogen bonding - Secondary: Kinking and coiling of sections of the polypeptide chain o Results of Hydrogen bonds between the repeating constituents - Tertiary: One polypeptide chain’s 3D shape - Quaternary: Bonds between different polypeptide chains Nucleic Acids: Genetic Material DNA: Deoxyribonucleic Acid RNA: Ribonucleic Acid - Structure: Polymers made up of nucleotides - Function: o 1) Make up our genes, important for reproduction o 2) Contain instruction that run cellular activity o 3) Contain instruction for protein synthesis DNA: Double Helix nucleotide polymer strand - a gene is a segment of the nucleotide strand that codes for the making of one protein - Arranges itself into chromosomes - Chromosomes are housed in the cell’s nucleus (Eukaryotes) or in a mass center of the cell, nucleoid (Prokaryotes) - Function: o 1) Contain genes, that give instruction for making proteins o 2) Replication and division of DNA occurs to make new copies of a cell (Mitosis) o 3) Transmits genes to offspring (Meiosis)  making sperm and eggs - Structure: 2 strands of DNA nucleotides(polymers) connected to one another by chemical bonds Nucleotide Structure: made up of - Phosphate group - A sugar: deoxyribose backbone of nucleotide strand  - One of 4 nitrogenous bases o 1) Adenine (A) o 2) Thymine (T) o 3) Guanine (G) o 4) Cytosine (C)  Reach out & bond to the 2 strange of DNA, forming the ladder rungs of the double helix   A pairs with T   C pairs with G  RNA: Ribonucleic Acid: single strand of nucleotides, sugar in the backbone of ribose  Functions: transports genetic instruction from DNA in the nucleus into the cytoplasm  Translates genetic instructions to proteins  Uracil (U) replaces Thymine (T) in nitrogenous bases DNA vs. RNA DNA RNA Sugar Deoxyribose Ribose Nitrogenous Base Thymine (T) Uracil (U) Structure Double stranded Single stranded Protein Synthesis: - The genetic code for a protein is copied (transcription) in the nucleus into a strand of RNA (messenger RNA, mRNA) which is used in the cytoplasm. - The mRNA strand (nucleotide sequence) will be translated into the amino acids sequence of protein Step One: Transcription: - DNA double helix separates at the site of the gene exposing the nucleotides on a single strand of DNA - RNA nucleotides come in and form an mRNA strand with complimentary bases Step Two: Translation: - The mRNA strand is sandwiched between 2 halves of a ribosome starting at one end of its strand - Each triplet of nitrogenous base on the mRNA strand is called a codon - tRNA come in and have anticodon sequences each o each codes for 1 particular amino acid o tRNA with the complimentary anticodon to the mRNA strand adds the corresponding amino acid to the protein chain being formed Types of RNA: - mRNA: an RNA copy of a gene. The instructions followed in the cytoplasm to build the correct polypeptide sequence of a protein - rRNA: Ribosomal RNA, RNA molecule + protein molecule = ribosomes site of protein synthesis in the cytoplasm - tRNA: transfer RNA, RNA molecule that translates nucleotide sequences of mRNA into amino acid sequences of proteins Chapter 6 Notes Prokaryotic Cells: DNA concentrated in the center of the cell but not bound by a membrane=nucleoid and cytoplasm fills the cells and no membrane bound organelles Eukaryotic Cells: DNA contained within a double membrane= nucleus and cytoplasm fills the cell except for in the nucleus and many membrane bound organelles Animal Cells Plant Cells Lysosomes Chloroplasts Centrosomes Central Vacuole Flagella Cell Wall & Plasmodsmata Plasma Membrane: - A semi-permeable membrane separating the intracellular environment from the extracellular environment - Phospholipids self orient into a double layer as the hydrophobic tails attract one another - Membrane protein are dispersed amongst the lipid bilayer - Fluid mosaic model: makes plasma membrane pliable, important so that cells don’t break when we move Proteins: a) Aid in the transport of substances in and out of the cell b) Functions as enzymes, catalyzing chemical reactions c) Receptors for chemical messengers d) Act as ID tags for cell recognition e) Helps cell stay tightly together f) Helps cell maintain their shape Nucleus: - Large organelle housing the DNA of a cell (chromatin) covered with a double membrane (nuclear envelope) - Nuclear envelope is studded with nuclear pores for exchange of substances between the nucleus and cytoplasm of the cell - Nucelolous darker region of the nucleus which produces ribosomes Ribosomes: - Exit the nucleus through the nuclear pores and enter the cytoplasm after production - Some become embedded in an organelle called Endoplasmic Reticulum (ROUGH) and others remain free - Function: protein synthesis (translation phase) Endomembrane System: - Consists Of: Endoplasmic Reticulum (Rough & smooth) Golgi Apparatus, Lysosomes, and Vacuoles - Functions: Regulates protein traffic in the cell, performs metabolic functions Golgi Apparatus: - high folded membrane organelle - Receives protein from teh rough ER via transport vesicles (T.V) - Proteins are modified and stored until required - Proteins then packaged in T.V. to be secreted out of the cell - Also makes some polysaccharides Lysosomes: - Ball shaped organelles that contain digestive enzymes for breaking down macromolecules within a cell and act in two ways: o Phagocytosis: engulfing the macromolecule outside the cell forming a food vacuole which then merges with a lysosome for digestion o Autophagy: Lysosomes merge with a vesicle in the cell containing old or damaged organelles and digest them freeing their building blocks into the cytoplasm to be reused Vacuoles: - Food: formed by phagocytosis - Plant: Storage of proteins, poisons or pigaments - Contractile: pumps excess water out of cell - Central: in mature plant cells, holds water and ions, aids in plant growth Endomembrane System: - The nuclear envelope is connected to the rough ER which is continuous with the smooth ER - Proteins and plasma membrane components produced by rough ER travel to the Golgi apparatus in T.V.s - They are processed in the Golgi and repackaged in T.V.s - T.V.s travel to the plasma membrane where contents will be incorporated into the plasma membrane or secreted from the cell Mitochondrion: Bounded by a double membrane and its function is cellular respiration, the metabolic process that generates ATP by attracting energy from sugars, fats and other fuels with the help of oxygen sugars + oxygen  ATP (energy) Chloroplast: - Sites of photosynthesis - They convert solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from CO2 and O2 - 3 membranes (4 in algae), contains the pigment chlorophyll - Sunlight + CO2 + H2O  sugars The Cytoskeleton: - Microtubles: Tubuiln Polymers Hollow Tubes, function is to maintain the cell shape, cell motility (cilia or flagella), Chromosome movement in cell division, and organelle movements o Microfilaments: two intertwined strands of actin  Function: maintenance of cell shape  Changes in cell shape, muscle contraction  Cytoplasmic streaming, cell motility & division (cleavage furrow) o Intermediate Filaments: fibrous proteins supercollider into thicker cables  Function: maintenance of cell shape  Anchorage of nucleus and certain other organells  Formation of nuclear lamina - Centrosomes: the anchor point for the cytoskeleton that is made up of a pair of centrioles (concentration of microtubules) and involved in cell division - Cilia and Flagella: Extensions of the cytoskeleton outside the cell’s surface o The Cilia and is short& thin protrusions of the cytoskeleton and the flagella is longer and whip like. Functions for both include: motility of the cell and of substances along tissue surfaces  Motion of the flagella: a flagellum usually undulates, its snakelike motion driving a cell in the same direction as the axis of the flagellum. Propulsion of a human sperm cells is an example of a flagellate locomotion  Motion of Cilia: back and forth. The rapid power stroke moves the cell in a direction perpendicular to the axis of the cilium. During the slower recovery stroke, the cilium bends and sweeps sideways closer to the surface Chapter 7 Notes Movement of phospholipids: lipids move laterally in a membrane (∼10^7 times/second) flip- flopping happens rarely (once a month) Membrane Fluidity: unsaturated hydrocarbon tails of phospholipids have kinks in them that keep the molecules from packing together, enhancing membrane fluidity Cholesterol within the animal cell membrane: reduces membrane fluidity at moderate temps by reducing phospholipids movement but at low temps it hinders solidification by disrupting the regular packing of phospholipids The permeability of the lipid bi-layers: - Non-polar molecules (hydrocarbons, CO2, O2) are hydrophobic and can therefore dissolve in the lipid bi-layer of the membrane and cross it easily without the aid of membrane proteins - The hydrophobic core of the membrane impedes the direct passage of ions and polar molecules such as glucose and other sugars pass very slowly even when H2O (small polar molecules) does not pass rapidly Transport Proteins: Hydrophobic substances can avoid contact with the lipid bi-layer by passing through transport proteins (or channel proteins) - Function: having hydrophilic channel that certain molecules or atomic ions use as a tunnel through the membrane - Aquaporins: Allows the passage of H2O molecules through the membrane in certain cells to be facilitated. Allows entry of up to 3 billion H2O molecules/second, passing single file through its central channel which fits 10 @ a time - Carrier Proteins: hold onto their passengers and change shape in a way that shuttle them across the membrane Transport protein is a specific for the substance it translocates (moves) allowing only certain substances to cross the membrane. e.g. Glucose enters the red blood cells rapidly via specific carrier proteins in the plasma membrane and passes through 50, 000 times faster than diffusion through on its own Diffusion: the movement of molecules of any substance so that they spread out evenly into the available space. RULE: in the absence of other forces, a substance will diffuse from where it’s more concentrated to where it is less concentrated (down a concentration gradient) Passive Transport: The diffusion of a substance across a biological membrane is called P.T. because teh cell does not have to expend energy to make it happen Osmosis: H2O diffuses across the membrane from the region of lower solute concentration to that of higher solute concentrations until the solute concentrations on both sides of the membrane are equal Tonicity: - The ability of a solution to cause a cell to gain or lose water - Depends in part on its concentration of solutes that cannot cross the membrane, relative to that inside the cell - If there is a higher concentration of non penetrating solutes in the surrounding solution, H2O will tend to leave the cell and vice versa Tonicity (cont’d) o Isotonic: H2O flows across the membrane but at the same rate in both directions  E.g. volume of an animal cell is stable o Hypertonic: More non-penetrable solutes, cells will lose H2O to its environment, shrivel and probably die  This is a way that an increase in the salinity(saltiness) of a lake can kill animals o Hypotonic: less non-penetrable solutes, H2O will enter the cell faster than it leaves, and the cell will swell and lyses (burst) Facilitated Diffusion: Many polar molecules and ions impeded by the lipid bi-layer of the membrane diffuse passively with the help of transport proteins that span the membrane - Ion channels: function mostly as gated channels which open or close in response to stimulus that may be electrical or chemical o Chemical: the stimulus is a substance other than the one to be transported - Active Transport: specific membrane proteins use energy in the form of ATP to do the work o The transport protein that move solutes against a concentration gradient are all carrier proteins over channel proteins o Enables a cell to maintain internal concentration of small solutes that differ from concentration in its environment o ATP can power active transport by transferring its terminal phosphate group directly to the transport protein  Induces the protein to change its shaper in a manner that translocates a solute bound to a protein across the membrane • Sodium-Potassium pump which exchanges Na+ for K+ across the plasma membrane of animal cells - Co-transport: coupled transport by a membrane protein  one solute’s “downhill” diffusion drives the other’s “uphill” transport. Active transport driving by a concentration gradient o A carrier protein such as sucrose, H+ co-transporter is able to use the diffusion of H+ down its electrochemical gradient into the cell to drive the uptake of sucrose o The H+ gradient is maintained by an ATP driven proton pump that concentrates H+ outside the cell storing potential energy that can be used for Active Transport like sucrose. ATP is necessary because its indirectly providing the energy for co- transport - Bulk Transport: o Exocytosis: The cell secretes certain biological molecules by the fusion of vesicles with the plasma memebrane  A transport vesicle that has budded from the Golgi apparatus moves along microtubules of the cytoskeleton to the plasma membrane  When the vesicles & membrane come into contact the lipid molecule of the two bi-layers rearrange themselves so that the two membranes fuse  The contents of the vesicles then spill to the outside of the cell and the vesicle membrane becomes part of the plasma membrane • Example: pancreas makes insulin, neuron uses exocytosis to release neurotransmitters o Endocytosis: 3 types  Phagocytosis (cellular eating): a cell engulfs a particle by wrapping pseudopodia around it and packaging it within a membrane enclosed sac that can be large enough to be called a vacuole. The particle is digested after vacuole fuses with a lysosome  Pinocytosis (cellular drinking): the cell “gulps” droplets of extracellular fluid into tiny vesicles. The molecules in the droplets are what is needed; non-specific in the substances it transports.  Receptor-Mediated: Allows the cell to acquire bulk amounts of specific substances even through the are not very concentrated. The substances bind to the receptor  coated pit is formed  vesicle. • After this ingested material is liberated from the vesicle, the receptors are recycled to the plasma membrane by the same vesicle Chapter 12 Notes Genome: A cell’s endowment of DNA, it’s genetic info - Before the cell can divide to form genetically, identical daughter cells, all this DNA must be copied and then the 2 copies separate so that each daughter cell ends up with a complete genome Chromosome: - Replication and Distribution of so much DNA is manageable because the DNA molecules are stored in chromosomes - Made up of chromatin, a complex of DNA and associated with protein molecules - Contains a very long, linear DNA molecule that carries hundreds of thousands of genes - After duplication, they condense, each chromatin fibre becomes densely coiled and folded making the chromosomes much shorter Sister Chromatids: - Each duplicated chromosome has 2 of these, containing identical DNA molecules - Has a narrow waist  centromere where the two chromatids are most closely attached - Mechanical process separate the sister chromatids into two chromosomes and distribute them to the daughter cells Interphase: longest stage, the cell grows and copies its chromosomes in prep for cell division – 3 sub phases in which the cell grows by producing proteins and cytoplasmic organelles such as mitochondria and endoplasmic reticulum - The cell grows (Gap 1/G1: 5-6hrs) continues to grow as it copies its chromosomes (Synthesis/S: 10-12hrs) grows more as it completes prep for cell division (Gap 2/G2: 4- 6hrs) and divides (Mitotic/M: >1hr) Mitotic Spindle: Apparatus of microtubules that controls chromosomes movement during mitosis. Assembly of the spindle microtubules stars at the centrosome - Interphase: a single centromere replicates forming two centrosomes which remain together near the nucleus - Prophase & Prometaphase: The two centrosomes move apart as spindle microtubules grow out from them o End of prometaphase the two cetrosomes one at each pole of the spindle, are at opposing ends of the cell - Aster: radical array of short microtubules extends from each centrosome - Kineochore (K): each sister chromatids of a replicated chromosome has a K, a structure of proteins associated with specific sections of chromosomal DNA at the centromere. The two chromosome K face in opposite directions Cytokinesis: - Division of cytoplasm happening in late telophase so the two daughter cells appear shortly after the end of mitosis - Animal cells involve the formation of a cleavage furrow which pinches the cell in two Binary Fission: in bacteria, the chromosomes replicates and the 2 daughter chromosomes actively move apart Cancer cells: Divide out of control forming tumours Chapter 13 Notes Homologous Chromosomes: Two chromosomes composing a pair have the same length, centromere position and staining pattern. Both carry genes controlling the same inherited characters Diploid Cell: Any cell with two chromosome sets - For humans, the diploid # = 46 (2n=46) The # of chromosomes in our somatic cell (an cell other than those involved in gamete formation) Haploid cell: Gametes (sperm and eggs) contain a single chromosome set (Humans haploid #= 23) Fertilization: Haploid sperm fuses with haploid egg resulting in a zygote (diploid because it contains two haploid sets of chromosomes) Stages of Meiosis: Interphase: Chromosomes are replicated  homologous pairs of replicated chromosomes Meiosis I – seperates homologous chromosomes - Prophase: replicated chromosomes pair and exchange segments o Crossing over: the exchange of corresponding segments of DNA molecules by non-sister chromatids is completed while homologous are in synapses  held tightly together by proteins along their lengths o Chiasmata: point where crossing over has occurred - Metaphase: chromosomes line up by homologous pairs. Both chromatids of one homologous are attached to the kinetochore microtubules and line up along metaphase plate - Anaphase: each pair of homologous chromosome separates - Telophase and Cytokinesis: two haploid cells form and each chromosome still consists of two sister chromatids Meiosis II – seperates sister chromatids - Prophase: spindle apparatus forms and each chromosome still has two sister chromatids - Metaphase: Chromosomes positioned along the metaphase plate o Because of crossing over, the 2 sister chromatids are not genetically identical o The kinetochores are attached to microtubules extending from opposite poles - Anaphase: Breakdown of proteins holding the sister chromatids together at the centromere allowing them to separate and move towards opposite ends as individual chromosomes - Telophase and Cytokinesis: Nuclei form o One parent cell produces 4 daughter cell each with a haploid set (unreplicated) of chromosomes o Each 4 genetically distinct from each other as well as the parent cell Comparing Mitosis and Meiosis: Both: - DNA replication occurs during interphase before mitosis/meiosis I - Number of Division: o Mitosis has one (prophase, metaphase, anaphase, telophase, and cytokinesis) o Meiosis has two, each including the above Unique to Meiosis: - Prophase I: Each homologous pair undergoes synapse and crossing over between non- sister chromatids - Metaphase I: Chromosomes line up as homologous pairs on the metaphase place - Anaphase I: Homologous pairs separate from each other; sister chromatids remain joined at the centromere Number of daughter cells: - Mitosis: two, each diploid (2n) and genetically identical to the parent cell o Function: enables multicellular adult to arise from zygote; produces cells for growth, repair and asexual reproduction (in some species) - Meiosis: four, each haploid (n) containing ½ as many chromosomes as the parent cell, genetically different from each other and from the parent cell o Function: produces gametes, reduces the number of chromosomes by ½ and introduces genetic variability among the gametes o Crossing over: recombinant chromosomes individual chromosomes that carry genes (DNA) derived from two different parents Chapter 14 Notes Alleles: Alternative versions of genes account for variations in inherited characters - Dominant allele: determines the organisms appearance (only need 1 to expressed) - Recessive allele: has no noticeable effect (needs 2 to be expressed) Homozygous: An organism that has a pair of identical alleles for a character (2 alleles the same for a gene) aa Heterozygous: An organism that has two different alleles for a character (Bb) Phenotype: An organism’ appearance of observable traits e.g. purple flowers Genotype: Genetic make-up e.g. PP and Pp have the same phenotype (purple) Testcross: Breeding an organism of unknown genotype with a recessive homozygote because it can reveal the genotype of that organism Monohybrids: True breeding parents, meaning that they were heterozygous for one character Dihybrids: crossing two different alleles Mendel’s Law of Segregation: - The 2 alleles for a heritable character segregate during gamete formation and end up in different gametes - When sperm and egg unite, each contributes its allele, restoring the paired condition in the offspring Law of Independent Assortment: Alleles from different heritable characters separate independently of each other during gamete formation Multiple Alleles for One Gene: Most genes have more than 2 alleles; e.g. ABO blood types Chapter 15 Notes Chromosomal Disease: having the wrong # of chromosomes present or damaged chromosomes - Causes: Physical or chemical disturbances during meiosis - Kinds: o Aneuploidy (wrong # of chromosomes) o Polyploidy (more than 2 complete sets of chromosomes) o Alterations to chromosome structure - Aneuploidy – two main kinds o Monosomic: missing a chromosome 2n-1 o Trisomic: 1 extra chromosome 2n+1 (down’s syndrome) o 4 Possibilites:  Male with extra X (XXY) Klinefelter syndrome, Sterile and breast enhancement  Male with extra Y (XYY) normal sexual development, tall  Female with extra X (XXX) Trisomy X, normal sexual development, tall  Female missing X (X) Turners syndrome, sterility Microevolution: change in allele frequencies for a gene trait in a population over generations Population: a group of individual of the same species, living in the same area and interbreeding producing fertile offspring Gene Pool: A population’s genetic make-up - All copies of every type of allele at every gene locus in all members of the population - For evolution to occur, pressure must be exerted on the population Causes of Microevolution: - Minor: o Mutation rare & even more rarely produced a variation that is advantageous o Non-Random mating: sexual selection, can alter genotype frequencies but rarely affect allele frequencies in the population - Major: o Natural Selection: Results in alleles being passed to the next generation in different proportions from the current generation. If one allele variation proves to be advantageous for survival over another o Genetic Drift: Random fluctuations in allele frequencies from one generation to the next  Larger populations is more likely to get alleles in the next generation that is closes to the parent generation  Smaller population have a higher chance of getting different alleles in the future just by chance some individuals don’t pass their genes  The Founder Effect: When a few individuals become isolated from a larger population and they start their own population. Their gene pool differs from the original population because there are so few of them. Some alleles will be over represented and vice versa  Bottle Neck Effect: When a population’s #s are drastically reduced due to a disaster (flood or fire) who survived is random. Alleles may be over/under represented in the survivors o Gene Flow: Transfer of alleles into or out of a population due to immigration of emigration of fertile individuals or their gametes Sex Chromosomes: - 22 pairs (autosomes) carry genes necessary for general development - 1 pair of sex chromosomes (2 kinds X & Y) - Contains genes that determine the individual’s sex and for other characteristics o 22 pairs of Male autosomes + XY chromosomes o 22 pairs of Female autosomes + XX chromosomes Determination of Sex: - Daughters receive an X chromosome from both parents - Sons receive an X from mom and an Y from dad Sex-linked Characteristics: Characteristics other than gender related ones inherited an X chromosome Part 2 Chapter 9 Notes Stages of Glycolysis: - Means sugar splitting - Glucose is a six-carbon sugar, it is split into 2 three-carbon sugars - These smaller sugars are then oxidized and their remaining atoms rearrange to form 2 molecules of pyruvate (ionized form of pyruvic acid) - Consists of 2 phases: o Energy investment: the cell actually spends ATP o Energy payoff: this investment is repaid with interest when ATP is produced by substrate-level phophorylation and NAD+ is reduced to NADH by electrons released from the oxidation of glucose - The net energy yield from glycolysis per glucose molecules is 2 ATP + 2 NADH - In the end, all of the carbon originally present in glucose is accounted for in the 2 molecules of pyruvate  NO CO2 is released during glycolysis - Glycolysis occurs whether or not Oxygen is present o When oxygen IS present, the chemical energy stored in the private and NADH can be extracted by the citric acid cycle and oxidative phsophorylation Citric Acid Cycle - Glycolysis released > ¼ of the chemical energy stored in glucose, most of the energy remains stockpiled in two molecules of pyruvate - If molecular oxygen is present, the pyruvate enters a mitochondrion (in eukaryote cells) where the enzymes of the citric acid cycle completes the oxidation of glucose o In prokaryotic cells, this process occurs in the cytosol - Upon entering the mitochondrion via active transport, pyruvate is first converted to a compound called acetyle coenzyme A (CoA) o A complex of several enzymes (the pyruvate dehydrogenase complex) catalyzes 3 steps:  1) Pyruvate’s carboxy group (-- COO-) is fully oxidized and has little chemical energy • The group is removed and given off as a molecule of CO2  2) The remaining two-carbon fragment is oxidized forming a compound named acetate (ionized form of acetic acid) • An enzyme transfers the extracted electrons to NAD+, storing energy in the form of NADH  CoA is attached to the acetate by an unstable bond that makes the acetyl group very reactive • Acetyl CoA has a high potential energy therefore, the reaction of CoA to yield lower-energy products is highly exergonic - Function: a metabolic furnace that oxidizes fuel derived from pyruvate - Pyruvate is broken down into 2 CO2 molecules o Cycle generates 1 ATP/turn by substrate-level  Most of the chemical energy is transferred to NAD+ and related electron carrier , the coenzyme FAD(flavin adenine dinucleotide) during the redox reaction o The reduced coenzymes, NADH and FADH2 send their cargo of high energy electrons to the electro transport chain (ETC) - To Calculate the inputs and outputs on a per-glucose basis, x2 because each glucose is split during glycolysis into 2 pyruvate molecules - Stages: o 1) Acetyl CoA adds its two-carbon cetyl group to oxaloacetate  Citrate o 2) Citrate is converted to its isomer, isocitrate, by removal of one water molecule and addition of another o 3) Isocitrate is oxidized reducing NAD+  NADH  Resulting compound loses a CO2 molecule o 4) Another Co2 is lose  compound oxidized NAD+  NADH  Remaining molecule is then attached to CoA by an unstable bond o 5) CoA is displaced by a phosphate group, which is transferred to GDP (Guanosine diphosphate) forming GTP (guanosine triphophaste) similar to ATP, and sometimes used to generate ATP o 6) Two hydrogen are transferred to FAD  FADH2 and oxidizing succinate o 7) Addition of H2O molecule rearranges bonds in the substrate o 8) the substrate is oxidized reducing NAD+  NADH and regenerating oxaloacetate - IN eukaryotic cells, the CCE are located in the mitochondrial matrix except for the enzyme that catalyzes step 6, which resides in the inner mitochondrial membrane Electron Transport Chain (ETC) - Electron carriers in the ETC alternate between reduced and oxidized states as they accept and donate electrons o Each component of the chain becomes reduced when it accepts electrons from its “uphill” neighbour, which has a low affinity for electrons (less electronegative) o It then returns to its oxidized form as it passes electrons “downhill” more electronegative neighbour - Electrons removed from glucose by NAD+ during glycolysis and Citric Acid Cycle are transferred from NADH to the 1 molecule of the ETC in complex I o This molecule is flavoprotein (FP) - Next, redox reaction, the FP returns to its oxidized form as it passes electrons to an iron- sulfur protein  passes e- to a compound called ubiquinone - This e- carrier is a small hydrophobic molecule, only one that’s not a protein - Most of the remaining e- carriers between ubiquinon and oxygen are proteins called cytochromes o Several types, each a different protein with a slightly different e- carrying heme group o The last cytochrome; cyt a3, passes its e- to O2 which is very electronegative  Each O2 atom also picks up a pair of hydrogen ions from the aqueous solution, forming H2O - Another source of e- is FADH2 (other reduced product of the citric acid cycle) o FADH2 adds its e- to the chain @ complex II @ a lower energy level than NADH o The ETC provides 1/3 less energy for ATP synthesis when the e- donor is FADH2 rather than NADH  FAHD2 and NADH each donate and equal number of e- (2) for O2 reduction - The ETC makes no ATP directly. It eases the fall of e- from food to O2, breaking a large free-energy drop into a serious of smaller steps that release energy in manageable amounts - How does the mitochondrion couple this e- transport and energy release to ATP synthesis? o The answer is a mechanism called chemiosmosis Chemiosmosis - ATP synthase uses the energy of an existing ion gradient to power ATP synthesis o Power source for the ATP synthase is a difference in the concentration of H+ ion on opposite sides of the inner mitochondrion memebrane - Energy is stored in the form of an H+ ion gradient across a membrane and is used to drive cellular work such as the synthesis of ATP - ATP Synthase Stages o 1) H+ ions flow down their gradient and enter a ½ channel in a stator, which is anchored in the membrane o 2) H+ ions enter binding sites within a rotor changing the shape of each subunit so that the rotor spins within the membrane o 3) Each H+ ion makes one complete turn before leaving the rotor and passing nd through a 2 ½ channel in the stator into the mitochondrial matrix o 4) Spinning of the rotor causes an internal rod to spin as well. This rod extends like a stalk into a knob below it, which is held stationary by part of the stator o 5) Turning of the rod activates catalytic sits in the knob that produce ATP from ADP and Pi - ATP synthase are the only sites that provide a route through the membrane for H+ - Their passage through ATP synthase uses the exergonic flow of H+ to drive the phoporylation of ADP o Energy stored in H+ gradient across a membrane couples the redox reactions of the ETC  ATP synthesis - Certain members of the ETC accept and release protons (H+) and electrons (e-) - e- transfers cause H+ to be taken up and released into the surround solution o Eukaryotic cells: e- carries are spatially arranged in the membrane in a way that H+ is accepted from the mitochondrial matrix and deposited in the intermembrane space  H+ gradient that results = proton motive force  The force drives H+ back across the membrane through H+ channesl provided by ATP synthase  In mitochondria, the energy for gradient formation comes from exergonic redox reations and ATP synthesis is the work performed o Chloroplasts use chemiosmosis to generate ATP during photosynthesis. Light drives both e- flow down an ETC  H+ gradient formation o Prokaryotes: generate H+ gradients across their plasma membrane. They then tap the proton motive force not only to make ATP inside the cell but to rotate their flagella and pump nutrients and waste products across the membrane Number of ATP’s formed per glucose - During respiration most energy flows in this sequence: Glucose  NADH  ETC  proton-motive force  ATP - ATP profit when cellular respiration oxidizes a molecule of glucose to six molecules of CO2 - 3 main depts. Glycolysis, citric acid cycle, and ETC which drives oxidative phosphorylation - 4 ATP produced directly by substrate level during glycolysis and CaC to the many more molecules of ATP generated by oxidative phosphorylation o Each NADH that transfers a pair of e- from glucose to the ETC contributes enough to the proton motive force to generate a max of 3 ATP - 3 Reasons why we cannot state an exact # of ATP molecules o 1) Phosphorylation and redox reactions are not directly coupled to each other, therefore the ratio of # of NADH molecules : # of ATP is not a whole # o 2) The ATP yield varies depending on the type of shuttle used to transport e- from the cytosol into the mitochondrion  The mitochondrial inner membrane is impermeable to NADH, therefore NADH in teh cytosol is separated from the oxidative phosphorylation  If e- are passed to FAD (brain cells) = 2 ATP from each cytosolic NADH NAD+ (liver/heart cells)= 3 ATP o 3) Use of the proton motive force (PMF) generated by the redox reaction reduces the yield of ATP  E.g. the PMF powers the mitochondria’s uptake of pyruvate from the cytosol. However, if all the PMF generated by teh ETC were used to drive ATP synthesis then: • 1 glucose molecule could generate a max of 34 ATP(oxidative) + 4 ATP(substrate) = 38 ATP Fermentation: a way of harvesting chemical energy without using O2 or ETC Anaerobic Respiration: an ETC is present with a final e- acceptor other than O2 Fermentation: the e- from NADH are passed to pyruvate (or derivative of) regenerating the NAD+ re
More Less

Related notes for BIOL 201

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.