Topic 3 Flashcards
Explain Nucleus - Eukaryote
-Controls cell activity by controlling transcription of DNA
-Large, surrounded by nuclear envelope
-Envelope contains pores for mRNA to move in and out
-Contains nucleolus (makes ribosomes)
-Contains chromatin (made of DNA and proteins)
Explain lysosome - Eukaryote
-Round organelle, no clear internal structure
-Contains digestive enzymes, kept seperate from cytoplasm
-Used to digest invading cells or break down work out components of cells
Explain ribosome - Eukaryote
-Small organelle, free floating or attached to RER
-Made of proteins and RNA
-Site where proteins are made
Explain RER and SER - Eukaryote
-System of membranes enclosing fluid filled space
-SIte where folding and processing of proteins made at ribosomes
-Similar to RER, no ribosomes
-Synthesies and processes LIPIDS
Explain golgi apparatus - Eukaryote
-Group of fluid filled, membrane-bound, flattened sacs
-Processes and packages new lipids and proteins
-Synthesises lysosomes
Explain mitrochondrion - Eukaryote
-Oval shaped, double membrane
-Inner membrane folded, forms structure named cristae
-Inside is named the matrix, houses enzymes involved in respiration
-Site of aerobic respiratiom
-Where ATP is producd
-Found in large numbers
Explain protein production
-Proteins are made at ribosomes
-Proteins produced on RER are folded and processed, e.g sugar chains added
-Vesicled and transported to golgi apparatus for more processing
-Vesicled once more to be transported around cell
-Extracellular enzymes move to cell surface to be secreted
Recall prokaryote structure (9x)
-Cytoplasm, has no membrane-bound organelles & smaller ribosomes
-Fragellum, long, hair-like, rotates for cell movement
-Circular DNA, long and coiled up
-Plasmids, small loops of DNA, contains genes for antibiotic resistance
-Mesosomes, inward folds in plasma membrane
-Capsule, made of secreted slime to protect bacteria from immune systems
-Pili, short, hair-like, helps stick to other cells, used to transfer genetic material between cells
-Cell wall, support, made from murein, which is a glycoprotein
-Plasma membrane, mainly made of lipids and proteins, control ins and outs of substances
Explain Mitosis
-Parent cell divides to produce 2 genetically identical daughter cells
-Mitosis is needed for growth and repair of tissues, and for asexual reproduction
-Mitosis -> Gap Phase 1 -> Interphase -> Gap Phase 2 -> Mitosis
Explain stages of mitosis: interphase and prophase
-DNA unravels and replicates (doubling genetic content)
-Organelles replicate, ATP content increases
-Chromosomes condense, shorter and fatter
-Bundles of centrioles move to opposite poles of cell
-Network of spindle (protein) fibres form
-Nuclear envelope breaks down and chromomoses lie free in cytoplasm
Explain stages of mitosis: metaphase and anaphase
-Chromosomes line up along at middle of cell
-Chromosomes attach to spindle fibres by their centromere
-Centromere divides, seperation of each pair of sister chromatids
-Spindle contracts, pulls chromatids to opposite poles of spindle by their centromere
Explain stages of mitsosis: telophase and cytokinesis
-Chromatids uncoil, becomes long and thin, now named chromsomes
-Nuclear envelope forms around each set of chromosomes, now there are 2 nuclei
-Cytoplasms divides
-Now there are 2 daughter cells which are gentically identical to original and eachother
Core Pratical: Root Tips
-Cut 1cm from tip of growing root e.g onion (tip is where growth occurs)
-Prepare boiling tube of 1M HCl, into a water bath of 60deg
-Place root tip into boiling tube, incubate for 5mins
-Pipette to rinse root tip withcold water, leave to dry on paper towel
-Mounted needle to break tip open and spread cells thinly
-Small drop of stain, leave for 2mins (makes chromosomes more visible)
-Cover slip over cells and push firmly to squash and thinen tissue, makes light easy to pass through too
-Use light microscope
-Mitotic index = number of cels w visible chromo / total num cells observed
Recall structure of egg cell
-Cell plasma membrane
-Follicle cells, protective coating
-Zona pellucida, protective glycoprotein layer which perm must penetrate
-Nucleus
Explain fertilisation
-Occurs in oviduct
-Sperm swims to egg cell
-When sperm contacts zona pellucida, acrosomal reaction occurs
-Digestive enzymes in the sperm head is released, digestion of zona pellucida occurs
-Sperm head fuses with cell membrane, cortical reaction occurs
-Egg releases contents of vesicles (from cytoplasm) into the C.M, Z.P space
-Cortical granules released there release chemicals which harden/thicken the Z.P
-Ensures one sperm penetrates, protects egg cell from multiple fertilisations
-Nucleus of sperm fuses with nucleus of egg (fertilisation)
Explain stages of meiosis
-DNA replicates, 2 identical copies of each chromosome (chromatids)
-DNA condenses, forms double-armed chromosomes made from 2 sis chromatids
-Chromosomes arranged into homologous pairs e.g num 1 and num 1 pair, crossing over can occur
-1st division, homologous pairs seperate, halving chromosome number
-2nd division: pairs of sister chromatids seperate
-Four new daughter cells produced, genetically differ.
Explain crossing over
-Before 1st division, homologous pairs pair up
-Two chromatids in each pair, twist around one another
-Twisted bits break off their original and join onto their new chromatid
-Chromatids have same number of genes. just differing combos of alleles
-4 new cells formed from meiosis contain chromatids with differing alleles
Explain independant assortment of chromosomes
-4 daughter cells formed from meiosis have different combinations of chromosomes
-When gametes are produced, you have half genes from mum and dad
-When gametes produced, different combos of said maternal and paternal genes go into each cell
Define totipotency and pluripotency
-Ability to produce all cell types in an organism including extraembryonic cells (placenta and umbillical cord cells)
-Ability for a stem cell to produce all specialised cells in an organism not including extraembryonic ones
Explain transcription factors
-Controls gene expression by altering rate of transcription
-Proteins that bind to DNA to activate or deactivate genes by increasing or decreasing rate of transcription
-In prokaryotes, T.F binds to operons to control gene expressions
Explain lac operon in E.Coli
-Ecoli is bacterium that respires glucose, it uses lactose if glucose is unavailable
-Genes producing enzymes needed to respire lactose is found on lac operon
-Lac operon has 3 structural genes, LacZ, Y and A, which produce proteins that aid bacteria digesting lactose
Explain lactose not present in E.Coli
-Regulatory gene lacll produces lac repressor, a T.F that binds to operator site out of presence of lactose
-This blocks transcription as RNA polymerase cannot bind to the promoter region
-Structural genes are not transcribed
Explain lactose present in E.Coli
-Lactose binds to repressor changing its shape so it cannot bind to operator site
-RNA polymerase can bind to the promoter region and begin its transcription of structural genes (lacz, y and A)
Explain where stem cells can come from
-From adult tissues: stem cells found in bone marrow, limited differentiation
-Simple operation, very little risk however much discomfort
-From embroyos: created in IVF where egg cells are fertilised by sperm outside the womb, totipotent stem cell.
-Embroyos must be 4-5 days old, their stem cells to be removed resulting in embryo destroyed
-Ethical issue: killing of potential fetus
