biology topic 2 unit 1 motes

8/3/2019 Biology Topic 2 Unit 1 Motes

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TOPIC 1- LIFESTYLE, HEALTH & RISK

WATERH-Bonds creates adhesive affect- high mp/bp relative to similar sized moleculesExcellent solvent- dipole allows ionic substances to be dissolved- polar substancesalso dissolveCarries non-polar substances as COLLOIDS (solute particles bigger than solvent)Insoluble particles form EMULSIONS (droplets of one liquid held in another) orSUSPENSIONS (solid + liquid particles separate out if constantly moved)High surface tension- like covered by skin- no interact between air and water itself-h bonds pull down and together.Amphoteric- acts as Ph buffer as is proton donor H+ or acceptor OH-High latent heat of evaporation- evaporation takes a lot of energy so cools as

evaporatesThermally stable due to high specific heat capacityCreates cohesion (important in plants section T4)

CIRCULATORY SYSTEM- higher metabolic rate of many mammals etc means that diffusion is too slow tomeet needs, as SA/V ratio is small- thus mass transport systems are used tomaximise efficiency. In some animals their needs are met by simple diffusion suchas amoeba with a large SA/V ratio diffusion is efficient and effective.

BLOODPlasma- main component largely water and dissolved substancesErythrocytes- red blood cells- biconcave discs no nucleus more room forhaemoglobin and O2Leukocytes- white blood cells- can squeeze and change shape, have nucleus +colourless cytoplasmPlatelets- fragments of other cells, involved in clot formation.

BLOOD VESSELSArteries- blood away from heart- to lungs = pulmonary artery to be oxygenated-

to body via aorta or head/neck via aorta and carotid arteries. Small lumen, largeamount collagen and elastic fibres to allow to return to shape when expands. Novalves, smooth endothelial lining- prevent friction.Arteries most at risk from damage due to high blood pressure and recoil.Veins- blood back towards heart- pulmonary vein from lungs (oxygenated)-inferior vena cava and superior vena cava from body. Have valves to prevent backflow as is at lower pressure than arteries. Large lumen to act as blood reservoirand some but less elastic and collagen fibres.Capillaries- network that links arteries and veins, 1 cell thick and very thin, RBCpass through, nutrients out into network and waste (CO2 etc) returned to red

blood cell. Blood pressure low through network- blood flows from arteries-arterioles to capillary network to venules and veins.


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THE HEARTSuperior Vena Cava vein-carries deoxygenated blood from the upper body toright atrium.Pulmonary Veins carries blood from the lungs to the left atrium of the heartRight Atrium blood collection chamber of the heart, it has a thin walled structureLeft Atrium this receives oxygenated blood from the left and right pulmonaryveins.Right Ventricle this receives blood from theright atrium and pumps it in to the pulmonaryartery.Inferior Vena Cava - carries de-oxygenated blood from the lower body intothe right atrium of the heart.Aorta largest artery in the body -brings

oxygenated blood to all parts of the body in thesystemic circulation.Cardiac Muscle these muscle cells push bloodfrom the atria to the ventricles to the bloodvessels of the circulatory system.Pulmonary Arteries this carries blood from the heart the lungs.When the muscles of the atria walls contract it forces the remaining blood in to theventricles. The walls of the ventricles contract as they fill with blood, the increasedblood pressure closes the atrioventricular valves preventing backflow of blood in tothe atria. As the atrioventricular valves are closed the pressure increases opening

the semi lunar valves and pushing the blood in to the pulmonary artery and aorta. Atrioventricular Valves these are located betweenthe atrium and the ventricle on both sides. They preventbackflow of blood in to the atria as the closure of thesevalves ensures that the blood will flow in to thepulmonary artery or aorta. Semi-Lunar Valves these are in the aorta andpulmonary artery , they prevent backflow of blood in to theventricles.

The sinoatrial top of the right atrium-create regular

waves of electrical activity to atria allowingcontraction- prevent spreading by insulating fibrous tissue

CARDIAC CYCLEDiastole + systole.Diastole- atria / ventricles relax- blood into atrium- atrioventricular valves open-blood into ventricles- semi lunar is closed.Systole- ventricles contract- atrioventricular closes, semi lunar opens blood toaorta or pulmonary artery

INTRINSIC RHYTHMearly embryo cells begin to rhythmically contract long before muscle forms- viaelectrical excitation at 60bpm.


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CARDIOVASCULAR CENTER IN BRAINControls heart- as nerves speed the heart or slow down- dependant on CO2 levelsin blood- nerve control provides quick reactions- hormones also affect heart ratebut generally slower.

CORONARY ARTERIESFeed myocardial (heart muscle) above aortic valve from aorta so receivedstraight away and quickly.

BLOOD PRESSUREMeasured by SPHYGMOMANOMETER (automatic one or cuff + mercury manometerand stethoscope)BP = systolic bp / diastolic bp e.g. 120/80Hypertension- high blood pressure (140/90) (can be caused by narrowed arteries)

Hypotension- low blood pressure (90/60) (can be caused by weak heart)

DRUGS FOR LOWERING BLOOD PRESSURE- ANTIHYPERTENSIVESDiuretics- increased volume of urine- lower blood volume- lower blood pressure(SE nausea)Beta blockers- block hearts response to hormones such as adrenaline that speedheart up (SE diabetes link)Sympathetic Nerve Inhibitors- block sympathetic nerves- these get arteries toconstrict, by blocking keeps arteries dilated so blood pressure is kept low (SEcough)

ACE Inhibitors- hormone angiotensin causes blood vessels to constrict soinhibitors prevent these being made thus vessels are not constricted. (SE impairedkidney function)

Treatment of CVD involved antihypertensives (lower bp), reducing of cholesterol(statins), anticoagulants- (less likely atheroma to form), and plateletinhibitors

Statins-block enzyme in liver that makes cholesterol (SE nausea, constipation orrare inflammation reactions- can encourage a not healthy diet, create attitude that

no need to eat well as statins prevent cholesterol build up)Anticoagulants- e.g. Warfarin, prevent risk of clot formation by thinning blood-(SE uncontrolled bleeding)Platelet inhibitors e.g. Aspirin- makes platelets less sticky (SE irritation tostomach lining cause stomach bleeding)

CVD- CARDIOVASCULAR DISEASEResults from coronary arteries narrowed with fatty deposits- narrowing reducesflow and can starve heart muscle of oxygen- also one blood clot (thrombosis)increases likelihood of another

Blood clotting as a process is important- prevents bleeding to death and entranceof pathogens.


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But clot in vessels is the problem-Damage to vessel- exposes collagen fibres- platelets from blood stick- the

platelets release thromboplastin- in presence of calcium ions and vitamin Kthromboplastin converts prothrombin to thrombin- this converts soluble fibrinogento insoluble fibrin that creates a mesh-like network of fibres trapping cells + debristo = a clot.

Cascade =Damage to lining- increased likelihood of clot- if clot occurs, inflammatoryresponse- cholesterol builds up = atheroma- build up of calcium, salts andplatelets = plaque formation- narrows artery- raises blood pressure- increasedlikelihood of damage.

Clot can lead to aneurysm, plaque causes blood build up behind- artery bulges,can rupture arteryArtherosclerosis- process as above but calcium plaque causes loss of elasticity inartery walls- less able to cope with recoil damage more likely.

What increases likelihood of artery damage and why-Smoking- nicotine intake results in adrenaline production- heart rate faster, BPincreases

- toxins in smoke irritate endothelial lining, greater risk of damage

Obesity- greater strain on heart, also association between obesity and raised bloodpressure/ had dietInactivity- exercise makes heart stronger so can pump more blood with each beat.High cholesterol/ fatty died- large amounts cholesterol in blood stream increasesrisk of clotFamily history- suggested genetic linksHigh Blood Pressure.Age- with ageing elasticity and width of arteries deterioratesGender- oestrogen in women offers some protection from CVD

Treatments- anticoagulants, antihypertensives, statins (see above)Risk can be reduced by changing lifestyle choices such as smoking or bad diet

Risk- can be actual, as suggested by studies, or perceived-that is altered by anindividuals personal experiences and perceptions.Risk is the probability of the occurrence of a unwanted event or outcome- butcorrelation does not imply causation. Epidemiologists conduct research to accessrisk factors;

Types of study =Cohort- many people, long time period, categorised according to who has/ doesnt

have condition- risk factors accessed e.g. Munster Heart Study (see below) incholesterol.Case-control studies- group with condition and control group- past history


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researched- important to match case/control groups in terms of age/ gender-independent variables are controlled

Good study- valid/ reliable data, representative of whole population- lack bias-variables controlled as much as possible- standardised measurement/ othertechniques- sample size- while large sample size is generally best- if only tiny %have disease small group individuals suffering best representative than largesample with one or two sufferers.

CARBOHYDRATESAll composed of Carbon, Hydrogen and Oxygen.

Three main groups- monosaccharides, disaccharides and polysaccharides

Monosaccharides- single sugar molecules containing 1 Oxygen atom and 2Hydrogen atoms for each Carbon.(C H2 O)n (n= number of sugars) e.g. Triose (n=3) C3H6O3

Disaccharides are two joined monosacs.Joined in a condensation reaction-H2O released

Link between two monosacs is covalent bond called glycosidic bond(C6 H10 O5)nGlucose+ Fructose = Sucrose (stored in plants e.g. sugar beet/cane)Glucose+ Galactose= Lactose (main carbohydrate of milk)Glucose+ Glucose= Maltose (found in germinating seeds e.g. barley)

Made of many monosacs joined with glycosidic bonds- many condensationreactions- lots H2O released.3-10 monosacs = oligosaccharides11+ monosacs= polysaccharidesNo sweet tasteCan form compact molecules, ideal for storage in cells.Glycosidic bonds broken in hydrolysis reaction.Not very water soluble- dont interfere cellular functions/ disrupt osmotic balance.

Starch important energy store in plants- sugar from photosyn. are converted tostarch- insoluble & compact- but can be rapidly broken downStarch= long chains glucose- but is mixture ofAMYLOSE andAMYLOPECTIN

AMYLOSE- unbranched polymer- spirals- more compact with length. Comprised200-5000 glucose molecules. Only released by enzymes working from each end ofamylase molecule.


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AMYLOPECTIN- Polymer of glucose molecules- but branched. Lots of terminal ends-break quickly when energy is required.

The combination of both in starch explains why starchy foods e.g. pasta are goodfor exercise. AMYLOPEC releases glucose for cellular respiration rapidly. AMYLOSEprovides longer term energy to keep going.

TYPICAL STARCH GRAIN IN PLANT CELL IS 75% AMYLOPEC- rest AMYLOSE.

Glycogen- like starch but + branches- quick breakdown.

AMYLOSE, AMYLOPECTIN AND GLYCOGEN ALL MADE GLUCOSE MOLECULES INCHAINSCarbon in glycosidic bond determines which is involved.Amylose- only glycosidic bonds carbon 1 and 4 *1,4-glycosidic bonds* = straight

Amylopectin- Some 1,4 but few 1,6-glycosidic bonds = branchingStarch = combination of straight chain amylose and branched Amylopectin.Glycogen= More 1,6 bonds than 1,4 bonds.

To be good store, bonds in carbohydrates need to be broken to release singlesugars for cells to use. Glycosidic bond between monosaccharides split byhydrolysis- opposite condensation- water required/ added to bond. Hydrolysistakes place in digestion/ in muscle and liver cells.

LIPIDS

Fatty acids + glycerol (3 fatty acids : glycerol= triglyceride)Act as energy source but also have functions such as protective around organs,also waterproofing fur/ feathers, insulating properties- the fatty sheath aroundnerves.

Lipids dissolve in organic solvents- insoluble in water so dont affect cellularosmotic balance.Fats are solid at room t, oils are liquid (if unsaturated double bonds= kinks in


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chain- weaker IM bonds)Fatty acid(s) + glycerol join by condensation reaction between carboxyl group onfatty acids and hydroxyl group on glycerol= ester bond so reaction =esterification.Lipid + protein = lipoprotein lipid + phosphate group= phospholipids (phosphateattaches to glycerol= hydrophilic head, lipid tails of fatty acids= hydrophobic)

CHOLESTEROLUsing to form cell membranes- cant dissolve in blood- found in all body cells andamong lipids- they have be transported via lipoprotein carriers;LDL (low-density lipoprotein) major cholesterol carrier, excess LDL increases riskplaque/ atheroma- reduces the cholesterol absorption from blood.HDL- (high-density lipoprotein) transports lipids/ unsaturated fats to liver to bebroken down / removed. HDL acts to reduce cholesterol- thus is considered goodcholesterol

High cholesterol- increase risk of CHD as clots ability to form increases due tolarge amount cholesterol in blood- treatment for high cholesterol = Statins (blockenzyme in liver responsible for making the cholesterol)Munster Heart Study- around 11,000 tested for between 4-14 years, agedbetween 36-65.

BMIBody mass index= mass (kg) / height(m) 2Under 21= UW 21-25=Good 26-30= OW 31+ ObeseBasic energy requirement = weight (kg) X 4 (4 is human basic energy

requirement per kg)BMR- basal metabolic rate = basic energy requirement x24

Total energy need = BMR + daily activity uses

CORE PRACTICALS FOR UNITDaphnia- affect of caffeine on heartbeatImmobilise daphnia via cotton wool strands on cavity slide-Set up microscope- include beaker of water as heat sink from light for microscopePut daphnia slide under- control- dash on piece of paper for each heart beat for 30seconds- x2 for bpm. Add caffeine sample- repeat

Vitamin C- content of fruit juicesFilter fruit juice sample- add to burette, add to 1cm3 of DCPIP until DCPIP iscolourless- greater volume of liquid less vitamin C-repeat with other juices ensurethorough cleaningProblems can occur with judging when DCPIP has decolourised and potential toread burette wrong- vitamin C containing juice added 1 drop at time- so only to 1drop accuracy.

TOPIC 2- GENES AND HEALTHPROTEINSProtein monomer is an amino acid.


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Amino acids have carboxylic group, hydrogen atom, amino group (NH2) andvariable R group.Central carbon= alpha carbonPrimary protein structure is formation of polypeptide chain= many amino acids

joined via condensation reactions to form peptide bondsSecondary Structure interactions between charged amino/ carboxylic groupsform alpha helix or beta pleated sheetTertiary structure further folding to = 3D shape due to ionic bonds of ionised Rgroups and further hydrophobic interactions = h bonds, covalent bonds, disulphidebridges and polar interactionsQuaternary structure two or more polypeptide chains held by h bonds

Globular proteins- complex tertiary + sometimes quaternary structure to formenzymes etcFibrous proteins little or no tertiary structure- parallel polypeptide chains cross

link to form fibres e.g. keratin in nails.Conjugated proteins- protein joined to a prosthetic group e.g. glycoproteins areproteins conjugated with a carbohydrate prosthetic group (holds water well-synovial fluids/ mucus function) Lipoproteins- proteins + lipid prosthetic group

CATALYSTSSpeed up reactions- enzymes are biological catalysts that work intracellular orextracellular.Enzymes are globular proteins- specific shape including a specific active site- onlycertain shaped molecules can fit into the active site- (substrate)= lock and key

hypothesis or if active site is induced to change shape by substrate= induced fittheory. Both end up with enzyme-substrate complex- charged groups attractdistorting the substrate by aiding bond breakage and formation- products releasedfrom active site- enzyme/ active site are unchanged and can accept anothersubstrate molecule.Anabolic reactions- build up new chemicalsCatabolic reactions- break downCombination= metabolismEnzymes work by lowering the activation energy neededWhen enzymes are denatured (due to heat/ pH etc) tertiary structure is lost due

breaking of H bonds etc- when this happens rate of reaction declines as enzymestops functioning

CELL MEMBRANESphospholipids bilayer- phosphate prostheticgroup attached to glycerol of lipid. Glyceroland phosphate= hydrophilic head, lipidtails are hydrophobic fatty acids. Chemicalpass through layer by carrier/channelproteins- fat-soluble organic molecules and

small molecules e.g. water can passthrough.Cholesterol regulates fluidity.


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Glycoproteins- function in cell signalling, recognition and bindingCarrier proteins- specific to molecules, transport via active transport. Channelproteins- facilitated diffusion. Receptors bind to hormones.Facilitated diffusion carrier proteins carry large water-soluble substancesDiffusion- small, lipid-soluble substances pass through down concentrationgradientFacilitated diffusion- via channel proteins- polar water soluble substances downconc. gradientActive Transport- water-soluble substances again concentration gradient needscarrier protein and ATP.Osmosis- water moves down water potential gradient.

Rate of diffusion is affected by surface area, concentration gradient, temperatureand distance

Temperature increase- permeability increases

The cell membrane is described to be fluidbecause of its hydrophobic integralcomponents such as lipids and membrane proteins that move laterally or sidewaysthroughout the membrane.

The membrane is depicted as mosaic because like a mosaic that is made up ofmany different parts the cell membrane, components such as glycoproteins arescattered throughout the membrane.

DNA STRUCTURE

Nucleic acids- information molecules of cells.DNA- deoxyribonucleic acid.RNA- ribonucleic acidDNA/RNA- polymers monomers are nucleotides/ mononucleotides.Each mononucleotide- 3 parts- pentose (5 CARBON) sugar, phosphate group and anitrogen containing base.Pentose Sug. In RNA- ribose, DNA- deoxyribose- (one less oxygen)

Nitrogen-containing bases found in nucleic acids-PURINES- 2 Nitrogen ringsADENINE, GUANINEPYRIMIDINES- 1 Nitrogen ring- CYTOSINE, THYMINEDNA- 4 base combo- 1 PURINE TO ONE PYRIMIDINES A-T G-CRNA purine base same but thymine is replaced by Uracil.

DEOXYRIBOSE has OH, off carbon on bottom left pentagon corner, and H onbottom right, RIBOSE has both OH.


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Phosphate group- makes nucleic acids acidicSugar, Base and phosphate joined by CONDENSATION REACTIONS- loss 2 H20molecules.Mononucleotides linked by condensation reaction- polynucleotide strands.Sugar from one bonds to phosphate in another= hydroxyl group at one end andphosphate at other.RNA- forms singular polynuc. Strands- folded to shapes or remain thread.DNA- two strands twisted around each other, one upside down.Sugar/phosphate= backboneInwards= bases = spiralled DNA.

Two strands DNA held Hydrogen bonds between complementary base pairs.5 strand and 3 strand- deps on which carbon of pentagon bonds are.DNA code- triplet code.3 base pairs= a codon.Same amino acid can be made of different codons e.g. Ser = AGA or AGG.

DNA REPLICATION- provide DNA for daughter cells- DNA unwinds and DNA Helicase causes strands to split ( H bonds break)- Exposed bases attract free nucleotides-- H bonds form between complementary pairs DNA polymerase and DNA ligase

join nucleotides- Two identical daughter strands formed- 4 strands from 2.

SEMI CONSERVATIVE REPLICATION-Theory of Meselson and StahlDNA cultured on heavy N15 (when centrifuged is low in test tube as is dense)

When DNA cultured on light N14- (centrifuged is high as not very dense)By moving one cultured DNA sample to lighter/ heavier base- when centrifuged isin middle= 1 heavy strand and one light strand must be semi conservative

PROTEIN SYNTHESIS- give instructions for making a certain proteinTRANSCRIPTION- makes mRNA strand.B bonds between base pairs split- DNA unwinds to = a sense and antisense strand-antisense used as template- complementary bases of ribonucleotides pair withantisense template strand but uracil replaced thymine- RNA polymerase joinsribonucleotides to form a singular mRNA.

TRANSLATION - mRNA strand leaves nucleus via nuclear pores (DNA too large)here lines up along ribosome- tRNA brings free nucleotides from cytoplasm andlines up along mRNA- these amino acids join via peptide bonds to = thepolypeptide chain

DNA MUTATIONSReplication, translation and transcription all involved reading, copying and pairingof bases- plenty of opportunities for error. Single codon changed or misread aminoacid polypeptide chain is altered- this is a mutation- can have no noticeablefunctional significance but can affect whole organism- many mutations occur

during meiosis so genetic material of gametes contains mutations. When somatic(body) cells have mutations- specific enzymes remove faulty area- acts asscissors.


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Point mutation- change in gene itself- miscopying nucleotidesChromosomal mutation- change in position of gene on chromosomeGene deletion- loss of geneDuplication- gene or gene sequence repeatedInversion- genes wrong way round

Translocation- different genes in different chromosomes swapped/ muddledWhole- chromosome mutation- entire chromosome lost- or duplicated (Downssyndrome 3 copies chromosome 21 instead of 2)Some mutations beneficial, some insignificant, some damaging.Mutagens increase rate or mutation or trigger it such as parts of Electromagneticspectrum.

CFTR MUTATION- cystic fibrosisNormal functioning CFTR protein- enables sodium channel- Na+ and CL- ions entercell- CL- via chlorine pump on Basal side via active transport. BUT when CFTR not

functioning- blocks sodium channel so ions cant leave- thus water moves viaosmosis into the cell- so it is not with mucus that as a result is salty and thick-builds up in airways- blocks air flow to alveoli- cilia cant move out of system.Pathogens get trapped in mucus- ideal conditions for infection to develop.Dehydrated cells loose anti-bacterial properties.Mucus blocks pancreatic duct- enzymes to digest food cant reach intestine-trapped in pancreas, can begin to digest pancreas thus damaging it. Mucus blockscervix in women. Sweat is salty and more concentrated- reabsorption of salts doesnot occur- salts lost.

Treatments-

Physiotherapy- means to remove mucus from airways manually by massage twicea day

Take enzymes with food so they can be digestedAntibiotic medication (usually inhalers) - prevent pathogens caught in mucuscausing infectionFertility treatments like IVF

TransplantsGene therapy

GENE THERAPY- inserting normal allele of a gene into cells to replace a faulty allele

caused by a inherited disorder. Can be done on early embryo (illegal in UKcurrently) or in the affected body part-somatic therapy

SOMATIC THERAPY-identify gene involved e.g. for CF onchromosome 7- make copies of normal allele- insertinto vector (usually viruses andliposomes)

- use the vector to insert the allele into thetarget cells.After insertion the normal allele into the


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genome the target cell can make it- make CFTR function thus allow normalchloride movement- but faulty gene still in gametes- so can be passed on.Only around 25% normal chloride function resumesEffect is temporary as cells die- and new cells have DNA with faulty geneUse of virus vectors have side effectsHard to deliver, especially with liposomes 1 in 1000 genes reached an epithelialcell.

Genetic disorders cant be cured- thus avoidance and early treatment areimportant for potential parents-

- not have child if will have condition,- treatment straight after birth- reduce impacts later- genetically screen new born to know- but sometimes false negatives occur due

to sheer variety of mutations that cause harm etc.- PIGD- pre-implantation genetic diagnosis- embryos from IVF tested before

implanted- Prenatal DNA testing can allow choice if baby has condition;

AMNIOCENTESIS- syringe through stomach- amniotic fluid taken and cultured andtested- foetus must be around 15 weeks--- termination more traumatic, riskmiscarriageCHORIONIC VILLUS SAMPLING- syringe through vagina takes sample of embryonictissue from placenta- can be done at 8-10 week foetus and results can be gainednext day- no need to culture.Factors to be considered

-risk of miscarriage- risk to foetus-abortion if positive for mutation-cost of bringing up disabled child-mental and emotional trauma of disabled child or abortion-being preparedETHICS-basic right to life- duty to provide that right-utilitarianism (maximising good)

best choice for yoursel

TOPIC 3-VOICE OF THE GENOME


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What? Functions?

Nucleus- This is the most visible structure ina non-dividing cell, and contains

most of the cells genetic material

Endoplasmic rectium- - Tubular network fused to nuclearmembrane

- Goes through cytoplasm onto cellmembrane

- Stores, separates, and serves ascell's transport system

- Smooth type: lacks ribosomes

- Rough type (pictured): ribosomesembedded in surface


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Golgi Body- - Anything made the ER istransported here in vesicles, whereit is modified and then sent on to

another destination.- Protein 'packaging plant'

- A membrane structure found nearnucleus

- Composed of numerous layersforming a sac

Ribosomes- - Each cell contains thousands- Miniature 'protein factories'

- Composes 25% of cell's mass- Stationary type: embedded inrough endoplasmic reticulum

- Mobile type: injects proteinsdirectly into cytoplasmLysosomes- - Digestive 'plant' for proteins,

lipids, and carbohydrates- Transports undigested material to

cell membrane for removal- Vary in shape depending on

process being carried out- Cell breaks down if lysosome

explodes

Nucleolus- - Spherical shape- Visible when cell is not dividing

- Contains RNA for proteinmanufacture

Nucleus membrane andpores.-

- Surrounds nucleus- Composed of two layers

- Numerous openings for nucleartraffic

Vacuoles- - Membrane-bound sacs forstorage, digestion, and waste

removal- Contains water solution

- Contractile vacuoles for waterremoval (in unicellular organisms)


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Micochondria- - Second largest organelle withunique genetic structure

- Double-layered outer membranewith inner folds called cristae- Energy-producing chemical

reactions take place on cristae- Controls level of water and other

materials in cell- Recycles and decomposes

proteins, fats, and carbohydrates,and forms urea

Centrioles- - Paired cylindrical organelles nearnucleus

- Composed of nine tubes, eachwith three tubules

- Involved in cellular division- Lie at right angles to each otherChromosomes- - Usually in the form of chromatin

- Contains genetic information- Composed of DNA

- Thicken for cellular division- Set number per species (i.e. 23

pairs for human)

Prokaryotes

Prokaryotes are unicellular organisms, found in all environments.Prokaryotes are the largest group of organisms, mostly due to the vastarray of bacteria which comprise the bulk of the prokaryote classification.

Characteristics:


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No nuclear membrane (genetic material dispersed throughoutcytoplasm)

No membrane-bound organelles

Simple internal structure

Most primitive type of cell (appeared about four billion years ago)

Examples:

Staphylococcus

E. coli

Streptococcus

MITOSIS

INTERPHASE-

-Time between divisions-Protein synthesis carried out

-Chromatin present-Nucleolus present-DNA replicated towards division time

PROPHASE-

- Chromatin thickens into chromosomes- Nuclear membrane disintegrates

- Centriole pairs move to opposite ends of the cell- Spindle fibers begin to form

METAPHASE-


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- Guided by the spindle fibers, the chromosome pairsline up along the center of the spindle structure

ANAPHASE-

- The chromosome pairs (sisters) begin to pull apart- Once separated, they are called daughter chromosomes

- Due to pull, many chromosomes bend

- Groove in plasma membrane present

TELOPHASE-

- Chromosomes return to chromatin

- Spindle disintegrates- Nuclear membrane takes shape again

- Centrioles replicate- Membrane continues to pinch inward(in plant cells a new cell wall is laid)


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MEIOSIS

PHASE 1.

INTERPHASE I

PROPHASEI

METAPHASE I

ANAPHASEI

TELOPHASE I

In Phase I, all material makes a copy of itself. Spindle fibers develop asthe membrane disintegrates. Some crossing over may occur as the

chromosomes thicken. They line up and pull apart. Once thechromosomes pairs are at opposite poles the cytoplasm material divides.

The two cells formed do not have the same genetic material, yet theyhave the normal number of chromosomes.

PHASE 2.
http://2.bp.blogspot.com/_HrsMw-at3Rs/TSddOuYIEcI/AAAAAAAAABw/uhMLVFeIewI/s1600/cellcycle2.jpg


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INTERPHASE II

PROPHASEII

METAPHASE II

ANAPHASEII

TELOPHASE II

In Phase II, no duplication of genetic material occurs. As the chromatinthicken to form chromosomes and group into pairs, the spindle forms and

the nuclear membrane disintegrates. As in mitosis, the pairs ofchromosomes line up at the centre and pull apart to opposite poles. Theythen then divide. In male organisms the four new cells are all the samesize. In females one of the four cells receives the bulk of the material.This becomes the functioning egg while the other three smaller cells

disintegrate.

INDEPENDENT ASSORTMENT & CROSSING OVER.

Independent assortment.

Independent assortment occurs during the first stage of meiosis as the

pairs line up and is a source of genetic variation. This is a randomprocess and either chromosome from each pair could be in any gamete.

An organism with six chromosomes (three homologous pairs- XX YY ZZ)could form eight combinations. This ensures that in humans with our 23chromosomes there are so many combinations that it would be rare to


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get two alike (unless its identical twins).

Crossing over.

In prophase I of meiosis,homologous chromosomes pair.

At points where they makecontact, called chiasmata, the

chromatids break and region. The

non-sister chromatids exchangecorresponding sections of DNA.This is known as crossing over. It

produces chromosomes thatcontain new combinations of

alleles from both parents.

Pollen Tube Growth

Nuclei also have to combine in plants

This takes place in the embryo sac within the ovule


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Pollen grains germinate on the style and pollen tubes grow down

the style towards ovary.

Tube grows through a microscopic pore into the embryo sac with 2

male nuclei.

5. The male nuclei enter the embryo sac

one fuses with the egg cell to form a diploid zygote - this will giverise to the embryo

the other fuses with the two polar nuclei to form a triploidendosperm nucleus - this will give rise to the endosperm that willnourish the developing embryo.

The Process is known as a double fertilization because two fusions occur.

Pollination...Pollination is the transfer of the male pollen grains to the female stigma

Depending on the species this can be:

self-pollination, where pollen is transferred to a stigma on the sameplant (this obviously reduces genetic variability)

cross-pollination where pollen is transferred to a stigma on adifferent plant

Pollination can be brought about by:

wind-pollination - where the pollen are blown around and a smallfraction land on a stigma

insect-pollination - where the pollen are attached to an insect whichthen releases them on to the stigma of another flower

Typical characteristics of wind- and insect-pollinated plants include:

Feature Wind-pollinated Insect-pollinated

position of flowers above leaves above leaves

petals

small, inconspicuous or

absent

large, conspicuous,

brightly coloured

nectaries absent present

scent not scented scented

stamenspendulous (hangoutside flower)

inside flower

anthers move freelyfixed - positioned tocome into contact withinsect

pollen large quantities, light,smooth grains

fewer produced, notsmooth to aid


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attachment to insect

stigmalarge, often feathery,hang outside flower

small, within flower,positioned to come intocontact with insect

Mechanisms for ensuring cross-pollination; protandry, protogynyand dioecious plants

Self-fertilization (as a result of self-pollination) is of value to uncommonor widely dispersed species where the chances of successful cross-fertilization (through self-pollination) are low.

However self-fertilization results in a species with limited geneticvariation which is therefore at greater risk should the environmentchange.

Cross-fertilization (or outbreeding) keeps the degree of genetic variationin a species high and there are a number of mechanisms by which cross-fertilization is favoured.

Most plants are hermaphrodite with male and female structures in thesame flower

But some plants have separate male and female flowers

Some of these type of plant are dioecious - with male flowers andfemales flowers on different individuals. Clearly inbreeding is impossiblehere.

Some are monoecious - male and female flowers are on the same plantbut there are other methods of preventing self-fertilization such as thetwo flowers being produced at different times.

Among hermaphrodite flowers self-fertilization can be prevented byhaving the smale and female structures develop at different times. Thisis known as dichogamy.

Dichogamous plants can be named according to which sexual structuredevelops first:

in protoandry the stamens ripen before the carpels are mature

in protogyny the carpels mature before the stamen.


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HUMAN FERTILIZATION

For fertilization to occur, a sperm must first make its way through twoouter layers of the egg; the cumulus and the zona pellucida.

To do this, the sperm head undergoes an acrosomal reaction in whichenzymes located in the sperms acrosome digest the cumulus and thezona pellucida layers.

The sperm then reaches the egg vitelline envelope where bindin proteinon the sperm reacts with bindin receptors on the envelope.

When these proteins recognize each other, the egg membrane swallowsthe sperm head.

This allows the sperm nucleus to enter the eggs cytoplasm and fuse withthe egg nucleus.


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EMBRYONIC DEVELOPMENT

Ovulation releases ovum/secondary oocyte

Fertilisation in the oviduct produces zygote

As zygote moves along oviduct > produces morula

- As zygote divides, cells become smaller

- Movement by cilia and peristalsis present in oviduct walls

Morula develops into a blastocyst

- Trophoblast (outer layer of blastocyst) nourishes future embryo

- Inner cell mass will become foetus

- Fluid filled cavity for protection (absorbs shocks, resistscompression, ...)

Blastocyst (?100cells) implants itself in uterus lining

- Nourished by secretion from uterus

- Microvilli provide large surface area (? gas + nutrients exchange)

Trophoblast secretes enzymes ? digest tissues and blood vesselofendometrium

Embryo uses released nutrients/products from digestion

Blastocyst becomes buried within endometrium

Microvilli are replaced by placenta

Trophoblast secretes human chorionic gonadotrophin (hCG) hormone

Stem Cells and Cell SpecialisationStem cells: undifferentiated cell that can keep dividing and give rise toother types of cell

Totipotent stem cells - Have the potential to give rise into a

individual (can give rise to all cell types)

Pluripotent stem cells - Give rise to most cell types though cant give

rise to all

Multipotent stem cells - some cells retain a certain capacity to give

rise to a variety of different cell types after the cells have become

differentiated.


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Differentiated: embryo develops into a multiceullular body and the cellsbecome differentiated ( specialised to perform a certain function )Plant cells reamin totipotent throughout the life of a plant. Manydifferentiated plans cells can undifferentiate and then develop into acompletly new plant (animals cant do this)How cells become Specialised

A stimulus is given to the unspecialised cells

Some genes are swtiched on - become active and others are

switched off

Messenger RNA is made from the active genes only

mRNA moves to the ribosomes where the correct protein is made.

this protein can alter the structure and function of cells

Demonstrating Totipotency (core practical)

A few plant cells of the same type need to be taken

Placed onto an agar which has growth hormonoes added

Cells divide by mitosis forming a cluster of cells

The clusters are divided and placed in containers with agar

Different growth hormonoes are added to the above stimulating the

plant cells to differentiate into roots, stem and leaves

Stem cells and medical therapiesSources of stem cells

Early embryo - totipotent cells

Older embryo - pluripotent cells

Differentiated cells - some multipotent but most can only make one

or few types of cell.

Embryonic stem cells - From used embryos in IVF (advantages -

Easy to extract and Grow/ Disadvantage - Ethical issues, rejection

by body, risk of infection) Adults stem cells - Source found in body (advantages - Fewer

ethical issues, rejection risk avoided/ disadvantages - Difficult to

extract, more difficult to produce different types of cell, risk of

infection)

Fused Stem cells (Nucleus taken from body cell, human egg cell

with nucleus removed. fuses then divides to form embryo

containing patients DNA) (advantages - rejection risk avoided,

potential for treating genetic disorders/disadvantages - ethical

issues, risk of infection)


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Using Stem cellsThey can be used to treat medical conditions where there is a less offunctioning of a type of cell

Parkinsons disease - Loss of nerve cells in brain used for muscle

control

Multiple scerosis (MS) - Electrical insulating layer around nerve cells

break down.

Type 1 diabetes - cells in pancrea produce low levels of insulin.

Burns - skin cells damaged

Issues of using Embryonic Stem cells

When does an embryo become a human with rights

Is it acceptable to use human embryo for research

Is it acceptable to fuse an adult human cell with a human egg cellto creat new stem cells.

Who makes the decision

People who work with stem cells - as they have an understanding or

issues and what is possible

Everyone else as they can give a range of points of view

Final decisions made by the HFEA

Cell cloning - Dolly the sheep

Transplanted the nucleus from the egg cell from the ovary into the

mammary cells.

These cells fused and grown in culture to create an early embryo

Implanted in the uterus of 3rd sheep - where embryo develops and

dolly the sheep is created. This sheep is chromosomally identical to

the mammary cell donnar.

Variation in PhenotypePhenotype : The outward expression of a cell of organisim due to aninteraction of genotype (genetic make up of a cell) and environment.E.gSiamese hair colour:

Genotype - gene codes for enzyme tyosine which helps to make fur

dark.

Environment - Enzyme only active when temp is lower than 31

degrees.

Phenotype - Ears drop below 31 so they will be dark (distinct areas)

Lung cancer and smoking


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Genotype: Presence of proto:oncogenes involved in regulating cell

cycle.

Environment: Chemical components of cigarette smoke can alter

these genes to oncogenses in lungs.

Phenotype: Cell cycle not regulated by oncogenes therefore lungcells keep dividing without a check - leading to cancerous tumers.

Polygenic inheritance and Continuous VariationPolygenic inheritance - more than one gene is involved in influencing thephenotype.

These genes will be at different locations on chromosomes ( humanheigh in age group) It gives rise to continuous variation where there arefew extremes and many in middle.

TOPIC 4- BIODIVERSITY ANDNATURAL RESOURCES.


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SPECIES

a group of organisms with similar morphology (looks the similar),

physiology (internally similar) and behaviour

which can interbreed to produce fertile offspring

and which are reproductively isolated from other species

HABITAT

a place with a distinct set of conditions where an organism lives

POPULATION

a group of individuals

of the same species

found in an area

COMMUNITY

the various populations

of different species

that share an ecosystem/ habitat

NICHE

the precise role of an organism in its environment;

the sum total of all the organisms' interactions

GENE POOL

the sum total of all alleles of all genes within a population

ADAPTATIONS and different TYPES of ADAPTATIONS. features which enable an organism to survive and reproduce
http://maps.grida.no/library/files/storage/global_development_and_biodiversity_large.jpg


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being specialised to suit an environment in which the organism

lives

BEHAVIOURAL ADAPTATIONS: any actions by organisms, which helpthem to survive and reproduce.

PHYSIOLOGICAL ADAPTATIONS: features of the internal workings of

an organism, which help them to survive and reproduce.ANATOMICAL ADAPTATIONS: physical structural features of an

organism's body, which help them to survive and reproduceCO-ADAPTATION?

two organisms become dependent of each other

and more and more closely adapted

NATURAL SELECTION

organisms change over time as they adapt to their changingenvironment

EVOLUTION

a change in the frequency of alleles over time

KEY OBSERVATIONS and CONCLUSIONS for NATURAL SELECTION?1. OBSERVATION: more offspring produced than can survive

STRUGGLE FOR EXISTENCE:

competition for survival between members of the same

species for resources such as food

limited resources between too many organisms

population size is limited by environment

2. OBSERVATION: huge amount of inherited variation between species

SURVIVAL OF THE FITTEST

organisms best adapted to the environment are more likely to

obtain resources (e.g. food)

and so more likely to survive and reproduce

How EVOLUTION occurs.

Variation exists within a species through RANDOM GENETIC

MUTATIONS, which form new alleles

Meiosis mixes up existing allele combinations

Change in environment causes a change in the selection pressure

Which causes a change in allele success Some alleles are favourable and some are harmful


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Organisms with favourable alleles survive and reproduce,

forming fertile offspring

Those who have the harmful allele do not

Inhertitance of the favourable allele occurs, increasing the

frequency of that allele in the next generationHIERARCHY in TAXONOMY (in order from largest to smallest).Kingdom

Phylum (plu. Phyla)

Class

Order

Family

Genus (plu Genera)

Species

3 domains of the DOMAIN SYSTEM.

ARCHAEA

organisms from PROKARYOTE kingdom

no nucleus

e.g. methanogens

BACTERIA

organisms from PROKARYOTE kingdom

no nucleus

e.g. all other bacteria (apart from methanogens)

EUCARYA/ EUKARYOTA

organisms from the other four kingdoms (not prokaryote)

eukaryotic


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plants/ animals/ fungi

BIODIVERSITY :SPECIES DIVERSITY:the number of different species and abundance of each species in an

area

GENETIC DIVERSITY:the variety of alleles within a species

ECOLOGICAL DIVERSITY:the variety between different habitats

'ENDEMISM'

when a species is unique to a single place

and isn't naturally found anywhere-else in the world

GENETIC DIVERSITY within a species? FIND THE NUMBER OF DIFFERENT ALLELES IN A GENE POOL.

by: DNA SEQUENCING:

to determine the bases in a DNA segment

determining the alleles present

GEL ELECTROPHORESIS:

DNA --> fragments

identify different alleles

SPECIES DIVERSITY?

1. SPECIES RICHNESS:

count the number of different types of species in a given habitat

more types of species: HIGH SPECIES RICHNESS

2. SPECIES EVENESS:

count the number ofa different types of species in a given habitat

AND the number of individuals of each species

similar abundances: HIGH SPECIES EVENESS

HIGH SPECIES RICHNESS AND HIGH SPECIES EVENESS = highlydiverse14 of 24


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PLANT CELL STRUCTUREAND FUNCTIONS.

AMYLOPLAST:

has a double

membrane

storage of starch

grains

PITS:

regions of thin

cell wall

allows transport

of substances

between cells

PLASMODESMATA:

channels in cell wall that link adjacent cells together

allows transport and communication between cells

MIDDLE LAMELLA:

is an adhesive sticking adjacent plant cells together

gives plant stability

contains pectins

VACUOLE:

contains cell sap

keeps cell turgid (stops plant wilting)

involved in the breakdown and isolation of unwanted chemicals in

cell

has a tonoplast- controls what enters and leaves the vacuole

STARCH and CELLULOSE. S: alpha-glucose monomer

C: beta-glucose monomer

S: branched amylopectin (1, 4 and 1,6 glycosidic bonds) and

unbranched amylose (1, 4 glycosidic bonds)

G: unbrached

S: chains with side branches; amylose is a helical coiled structure


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G: long straight chains

S: compact energy storage molecule in plants

C: strong structural support for cells

CELLULOSE and STRONG STRUCTURAL SUPPORT?

large number of hydrogen bonds forming bundles called

MICROFIBRILS

microfibrils:

arranged at many different angles

in layers

within matrix ofhemicelluloses and pectins

Hemicelluloses and pectins = glue that holds microfibrils together

HOW IS WATER TRANSPORTED UP XYLEM VESSELS? (DESCRIBETRANSPIRATION AND FORCES PRESENT)

TRANSPIRATION: water evaporated from the surface of spongymesophyll cells and diffuses down the diffusion gradient through stomataof leavesWater in the spongy mesophyll leaves is replaced from the xylem,lowering hydrostatic pressure at the top of the vessel, resulting in water

being drawn up from below:TRANSPIRATION STREAM.Hydrogen bonding between water molecules allows cohesion betweenwater molecules; this keeps water as a continuous column in the xylemvessel: COHESION-TENSION THEORY.Forces ofADHESION occur between water molecules and the xylem cellwalls.


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XYLEM VESSELS and SCLERENCHYMA FIBRES

.

X: transport water and minerals up the plant AND provide support

S: provide support

X: cell walls are thickened with lignin, making them strong and

waterproof S: cell walls are thickened with lignin, making them strong and

waterproof BUT contain more cellulose (microfibrils)

X and S: made of bundles of dead cells

X and S: hollow lumen

X and S: arranged in columns

X: long cylinders with no end walls

S: short structures with taperend ends (ends closed) X: has pits in walls-allows transport of water & mineral ions in and

out of xylem

S: no pits in walls

HOW DO YOU EXTRACT FIBRES FROM PLANTS?

1. Mechanically pull out fibres

2. Digest the surrounding tissues

3. RETTING:

pile stems in heaps

allows bacteria and fungi to rot plant

WHY PLANT FIBRES ARE STRONG.1. The arrangement of cellulose microfibrils in the (primary) cell wall

microfibrils are arranged in a net-like criss-cross arrangement

at many different angles

giving it strength2. The secondary thickening of cell walls


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plant cells can produce a secondary cell wall between the normal

cell wall and the cell membrane

giving more lignin

its microfibrils are arranged in sheets, running in one direction only

giving it strengthTENSILE STRENGTH OF PLANT FIBRES.1. Attach the plant fibre to a clamp stand

2. Attach a mass to the other end of the planf fibre, adding more mass insmall constant increments until the fibre snaps

3. Record the mass needed to break the fibre

4. Repeat, increase reliability of results.

5. Safety: make sure tha area where the mass stops ins clear/ has a large

container containing polysterene

6. Control: Make sure that the plant fibres are the SAME WIDTH andLENGTH.

ANTIBACTERIAL PROPERTIES OF PLANTS.1. Take extracts from 1 plant by drying and grinding each plant and soakin ethanol; control: plants must be same size so same amount ofextracts is used.3. Evenly spread a sample of bacteria onto an agar plate.4. Dip discs of absorbant paper into one of the plant extracts; control:discs must be same size so the same amount of liquid is absorbed byeach.5. Have a control disc which is ONLY soaked in ethanol.6. Place paper dics onto the agar plate (spread out evenly).7. Replace the lid and seal, but so gases cans still enter and leave.8. Incubate the the plate at about 25 degrees centigrade-allow bacteriato grow.9. Measure the clear patch around each disc: INHIBITION ZONE. Larger

the inhibition zone, the more effective the plant extract (betterantibacterial propertie

biology topic 2 unit 1 motes

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