Biology, Module 2: Cells complete Question and Answers

Biology, Module 2: Cells complete Question and Answers How to calculate magnification magnification = image size/actual size two stages of cell fractionation Homogenation , ultracentrifugation why is the tissue placed in a cold, buffered solution for cell fractionation? cold to reduce enzyme activity that might break down organelles, buffered as pH can alter structure of organelles, or function of enzymes why is the tissue placed in a solution of the same water potential for cell fractionation? to prevent organelles shrinking or bursting due to osmotic gain/loss of water conditions of solution the tissue is placed in for cell fractionation cold, buffered, same water potential as tissue describe homogenation - how and why -cells broken up in homogeniser, to release organelles from cell -homogenate (resultant fluid) then filtered to remove complete cells and large bits of debris describe ultracentrifugation filtrate put into a centrifuge on a low speed so the heaviest organelles go to the bottom and form a pellet, the organelles stay above as the supernatent. This gets removed and put into a new tube. process is repeated on higher speeds until all organelles are separated order heaviest to lightest: mitochondria, nuclei, lysosomes nuclei, mitochondria, lysosomes label the light microscope eyepiece lens, objective lens, stage, stage clips, coarse focus, fine focus, light how does an optical microscope work? light has long wavelengths, low resolution advantages of an optical microscope live specimens, cheap, easy to transport disadvantages of optical microscope limited magnification and resolution how does an electron microscope work? It uses a beam of electrons, short wavelength, high resolution advantages of an electron microscope higher resolving power, greater magnification disadvantages of an electron microscope dead specimens because of vacuum, cannot observe in color, very expensive. TEM vs SEM TEM can see internal organelles as electrons transmit through the cells SEM can only see the surface as electron deflect TEM in 2D whereas SEM in 3D TEM has to be extremely thin and has the highest resolution however SEM has to be very thin and has a lower resolution but still higher than optical 5 structures in the nucleus nuclear envelope, nuclear pores, nucleoplasm, chromosomes, nucleolus function of the nuclear envelope controls entry and exit of materials in and out of the nucleus, contains the reactions taking place within it function of nuclear pores allow the passage of large molecules like mRNA out of the nucleus, 40-100 nm in diametre function of the nucleoplasm main site of chemical reactions in nucleus funchromosomes Protein bound linear DNA function of nucleolus manufactures ribosomal RNA (rRNA), assembles ribosomes function of the nucleus retains the genetic info of the cell in the form of DNA and chromosomes, manufactures rRNA and ribosomes, acts as control centre of the cell (produces mRNA and tRNA; protein synthesis) structures in mitochondria outer membrane, intermembrane space, inner membrane, matrix, cristae, ATP synthase function of cristae Increases surface area for enzyme activity what does the matrix consist of? proteins(like enxymes for respiration), lipids, ribosomes, DNA function of mitochondr site of aerobic respiration, where ATP is produced, found in metabolically active cells structures in a chloroplast chloroplast envelope, grana, thylakoids,strom