1 Eukaryotic Large ribosomes Mitochondria Nucleus Linear DNA Prokaryotic Small ribosomes No mitochondria No Nucleus Circular DNA Plasmid / Flagellum Nucleus Nucleolus Ribosomes Endoplasmic reticulum Golgi apparatus Lysosomes Centrioles Mitochondria Contains chromatin that makes chromosomes (DNA and protein) Makes ribosomes Makes proteins Rough processes and folds proteins Smooth processes and synthesises lipids Processes and packages proteins/lipids (e.g. add carbohydrate to make glycoprotein) Makes lysosomes Uses digestive enzymes destroy invading cells / inactive parts of cell Protein cylinders that separate chromosomes during mitosis Aerobic respiration ATP made Double membrane Inside folds to form cristae Matrix holds respiratory enzymes 1) Proteins made at rough endoplasmic reticulum 2) Transported to Golgi apparatus in vesicles 3) Proteins undergo further processing (addition of carbohydrates to form glycoproteins) 4) Proteins enter vesicles 5) Vesicles move around cell or are secreted by exocytosis Tissue group of similar cells that carry out a particular function, making up an organ Organ groups of different tissue that work together to carry out a particular function System multiple organs working together for a function Mitosis 1) Interphase DNA unravels and replicates energy increased 2) Prophase chromosomes condense- centrioles move to opposite ends spindle fibre forms nuclear membrane breaks down 3) Metaphase chromosomes line up along middle of cell and are attached by centromere to spindle 4) Anaphase centromeres divide separating pairs of sister chromatids spindles contract pulling chromatids to opposite ends of the cell 5) Telophase chromatids reach opposite poles on the spindle uncoil and become long/thin chromosomes nuclear membrane forms again - cytoplasm divides to form two identical cells Asexual reproduction produce genetically identical organisms to the original parent, through binary fission, fragmentation, sporulation and budding.
2 Root tip experiment 1) Cut root tip 2) Place in watch glass 3) Add hydrochloric acid 4) Add few drops of stain (Schiffs reagent) 5) Warm the watch glass 6) Place root tip on microscopic slide 7) Use mounted needle to break open cells 8) Add more stain 9) Warm gently to intensify stain 10) Observe mitosis through light microscope Meiosis 1) DNA replicates to produce two identical copies of each chromosome called chromatids 2) DNA condenses to form double-armed chromosomes from two sister chromatids 3) Chromosomes arrange themselves in homologous pairs (crossing over occurs chromatids twist around each other via chiasma parts break off and rejoin, so four daughter cells contain chromatids with different combinations of alleles) 4) First division homologous pairs separate halving number of chromosomes 5) Second division pairs of sister chromatids separate 6) Four new cells (gametes) that are genetically different from each other are produced (independently assorted- chromosome pairs split up in any way, so the cells produced can contain any combination of maternal and paternal chromosomes with different alleles ) Mammal fertilisation 1) Sperm swims towards egg cell in the oviduct 2) Sperm makes contact with zona pellucida the acrosome releases digestive enzyme to digest it 3) Charge changes to positive inside to prevent more sperm 4) Sperm head fuses with the cell membrane triggering the cortical reaction 5) Cortical granules release contents to the space between cell membrane and zona pellucida to make it impenetrable to other sperm. 6) Secondary oocyte becomes ovum when sperm penetrates oocyte membrane. 7) Only the sperm nucleus enters the egg cell the tail is discarded 8) The nucleus of the sperm fuses with the nucleus of the egg cell this is fertilisation
3 Flowering plant fertilisation 1) Pollen grain lands on the stigma 2) It absorbs water and then splits open 3) A pollen tube grows from the pollen grain down the style 4) The tube nucleus makes digestive enzymes that allow the pollen tube to travel 5) When the pollen tube reaches the ovary it grows through the micropyle and into the embryo sac of the ovule 6) In the embryo sac the tube nucleus disintegrates where the tip of the pollen tube releases two male nuclei 7) One male nucleus fuses with the egg nucleus to make a zygote which divides by mitosis to become the embryo. 8) The second male nucleus fuses with two other polar nuclei which produce a cell with a large nucleus that divides to become a food store for the mature seed. 9) This finishes the double fertilisation process Specialisation of cells A) Fertilised egg cell divides B) Totipotent cells produced in embryo C) Cells divide and differentiate D) Pluripotent cells produced 1) Stem cells contain the same genes but not all of them are expressed because they are not all active 2) Under certain conditions some genes are activated and others are inactivated 3) mrna is only transcribed from the active genes 4)mRNA from active genes is then translated into proteins 5) Proteins modify the cell determining the cell structure and controlling cell processes e.g. activating more genes to produce more proteins 6) Changes to the cell produced by these proteins cause the cell to become specialised (differentiate) For Save lives Improve quality of life Unfertilised not viable ok to use Against Destruction of viable embryo Fertilisation right to life (IVF) Totipotency by tissue culture experiment 1) Single cell taken from a growing area on a plant e.g. shoot or root 2) Cell is placed in growth medium that contains nutrients and growth hormones 3) Plant cell will grow and divide into a mass of unspecialised cells. 4) If the conditions are appropriate the unspecialised cells will differentiate into specialised cells 5) Over time the cells will grow and differentiate into a new plant
4 Cell wall Middle lamella Plasmodesmata Pits Chloroplast Amyloplast Vacuole and Tonoplast Plant cell Surrounds plant cells supporting them Adhesive sticking adjacent plant cells together to give the plant stability Channels in the cell walls linking cells together that allows transport of substances between cells Thin regions of the cell wall that allows transport of substances between cells Flattened structure surrounded by a double membrane containing thylakoid membranes that form grana where photosynthesis takes place (or in stroma the fluid) Stores starch granules and converts it back to glucose when the plant needs it Vacuole contains cell sap made of water, enzymes and minerals keeping the cells turgid / for isolating unwanted chemicals. The tonoplast controls what enters and leaves the vacuole. Starch Energy storage material a-glucose Amylose 20% - unbranched - coiled Amylopectin 80% - branched side branches for enzymes to get to glycosidic bonds for energy release Cellulose Major component of cell walls b-glucose 50-80 cellulose chains link together by a large number of hydrogen bonds forming Microfibrils Matrix of hemicellulose arabinose holds cellulose chains together Cellulose microfibrils net like arrangement strength of microfibrils laid densely with their arrangement at different angles to each other allows the plant fibres to be strong Secondary thickening productions of another cell wall between the normal cell wall and the cell membrane which is thicker having more lignin giving the plant fibres a lot of strength Xylem vessels Transport water and mineral ions Support Inner region of stem - centre Dead cells Thickened with lignin Hollow lumen no cytoplasm No end walls Sclerenchyma fibres Support Outer region of stem outer edge Dead cells Thickened with lignin Hollow lumen - no cytoplasm No end walls
5 Tensile strength experiment 1) Attach fibre to clamp stand and hang a weight on the other end 2) Keep adding weights until the fibre breaks 3) Record the mass required to break the fibre 4) The higher the mass the higher the tensile strength 5) Test using different fibres, all of the same length Calcium ions Magnesium ions Nitrate ions Water Calcium pectate - growth Chlorophyll pigment for photosynthesis DNA / Proteins - growth Photosynthesis / Structural rigidity / Transport minerals / Regulate temp. Mineral deficiency experiment 1) Take 30 seedlings of the same plant and place them in separate pots 2) Create 3 different nutrient broths containing all the essential minerals but vary the concentration of particular ions one low, one medium and one high concentration 3) Split the plants into three groups each group should be given only one of the three broths 4) Record the heights of the plants after a set period of time Antibacterial properties of plants 1) Take extracts from plants to be tested by drying and grinding then placing them in ethanol 2) Filter off the liquid 3) Place some bacteria on an agar plate 4) Place discs of absorbent paper in the extracts 5) Have one disc of absorbent paper in only ethanol 6) Place the paper discs on the agar plate with the bacteria on it 7) Incubate the plate (cover it) to allow the bacteria to grow 8) Where the bacteria is prevented from growing there will be a clear area called the inhibition zone 9) The larger the inhibition zone the more effective the antibacterial properties of the plant extract are William Withering Trial and error Foxgloves could treat dropsy Identified digitalis as active ingredient Testing varied concentrations of digitalis to see how much would be harmful / ineffective Drug testing Placebo double blind experiment Computer models / Tissue / Animals Phase 1 test a new drug on a small group of healthy individuals to find safe dosage / side effects / how the body reacts Phase 2 Test drug on a larger group of people who are patients to see how effective the drug is Phase 3 Compare drug to existing treatments on hundreds of patients
6 Species diversity Number of different species (species richness) Abundance of each species 1)Random sample 2)Count number of species in area 3)Repeat for different areas 4) Estimate species richness/ abundance 5) Use Simpson s index of diversity Genetic diversity Variation of alleles within a species Phenotype look at different phenotypes - larger the number of different phenotypes larger the genetic diversity Genotype DNA Sequence of base pairs Order of bases in different alleles is different Look for similarities / differences in alleles Measure the number of different alleles a species has for one characteristic is to see how genetically diverse the species is Larger the number of different alleles the greater the genetic diversity A niche describes the position of a species within its ecosystem including the habitat in which the organism lives its interactions with other living organisms and its interactions with the non-living environment. Organisms can be adapted to their niche in ways that help them to survive and reproduce, such as behavioural, physiological and anatomical adaptations. 1) Individuals within a population show variation in their phenotypes 2) Predation disease and competition create a struggle for survival. 3) Individuals with better adaptations are more likely to survive reproduce and pass on their advantageous adaptations to their offspring. 4) Over time, the number of individuals with the adaptations increases so over generations the adaptations become more common in the population through evolution. Seedbanks Seeds stored in cool dry conditions Can be stored for long time Viability tests Less cost than conserving Large numbers of plants can be stored Less likely to be damaged Testing for viability can be expensive Difficult to collect seeds from remote locations Zoo Endangered species captured Careful selection for interbreeding Work with other zoos for outbreeding Increase numbers in wild reintroduce Problems breeding outside natural habitat Less genetic diversity Bring new diseases / Behavioural dysfunctions