Biology #1 Cell biology

  • Created by: MBid89
  • Created on: 23-04-18 10:53
What are the 2 main phases of cell cycles?
Interphase and cell division (including mitosis & cytokinesis)
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What happens during interphase? (3)
Number of mitochondria & chloroplasts (in plants) increases as they grow & divide. Growth. Protein synthesis.
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What happens during each stage of interphase?
G1: growth of cell (increase in size), new proteins & organelles made. S: DNA synthesis (replicates all genetic material). G2: Double checks for errors in copying, prepares for cell division
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What is the role of cyclins in cells?
They are proteins that ensure that taste are performed at the correct time. Cell does not progress into a new phase/ stage until the corresponding cyclin (4 main types in humans) has reached a threshold concentration.
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How do cyclins work?
Bind to enzymes called 'cyclin-dependent kinases'. These become active & attach phosphate groups to other proteins in the cell. This attachment triggers other proteins to become active & carry out tasks specific to that phase in the cell cycle.
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Who discovered cyclins?
Tim Hunt, by accident (serendipity), while doing research into protein synthesis in sea urchins.
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State cell theory (4)
All living things are made of cells. Cells are the unit of life. New cells come from old cells. Cells contain inherited information.
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What are 3 atypical cells & why?
Aseptate fungal hyphae: 1 long undivided tube, polynucleated (despite being surrounded by single plasma membrane). Striated muscle cells: cells fuse to form v long fibres (300m+), polynucleated. Giant algae cell: can be up to 7cm, complex form
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How did 19th cent scientists believe cells could be formed?
via 'spontaneous generation' (out of non-living material i.e. air?)
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Outline the origin of eukaryotic cells according to endosymbiotic theory
Mitochondria & chloroplasts are similar to prok. Host cell injested another. Symbiotic relationship (supplied ATP or carbon compounds to both itself & host). Division/ binary fission of mito/chloro. Host develop into either heterotroph or autotroph.
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What was the aim of Pasteur's experiments?
To falsify spontaneous generation & to support that new cells come from old cells.
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Outline Pasteur's experiment
2 groups of swan-necked flasks (prevented organisms in air from entering): 1 with broth, boiled to kill any organisms present, others unboiled. Fungi & other organisms soon appeared in unboiled but not in boiled ones.
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What is meant by 'unicellular organisms'?
Organisms that carry out all functions of life in 1 cell i.e. bacterium
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Give examples of 2 unicellular organisms
Paramecium (lives in ponds, 0.25mm or less). Chlamydomonas (lives in freshwater habitats, 10-30um)
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Give details of nutrition and response (i.e. movement) of paramecium & chlamydomonas. State whether they respire or photosynthesise.
Paramecium: nutrition: ingests & digests smaller organisms (heterotroph), response: reacts to stimuli (moves using cilia). Respires. Chlamydomonas: nutrition: photosynthetic autotroph, response: positive phototropism (using eye spot) Photosynthesises
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What is meant by 'multicellular organisms'?
Specialised groups of cells have different functions , allowing for cell size (SA to volume ratio) to stay the same while increasing complexity of organism.
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What are emergent properties?
Properties that arise from the interaction of the component parts of a complex structure (i.e. memory).
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State how differentiation occurs.
Each cell initially has the full genome, so could potentially specialise into any cell. When a cell differentiates only certain genes are expressed, & once this pathway has begun, it mostly cannot change (except in some plants).
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What are benefits of unicellular (2) vs multicellular (3) organisms?
Uni: can exist in hazardous areas due to simplistic form. Quick asexual reproduction. Multi: longer life span. Specialised cells (division of labour) that results in emergent properties. Communication between cells.
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What are stem cells?
Cells that have the capacity to divide & differentiate along different pathways (pluripotent)
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What are pros & cons of embryonic stem cells?
Pros: pluripotent & unlimited growth potential. Cons: could be argued that it is a potential human life being killed; immoral.
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What are pros & cons of adult stem cells?
Pros: compatible with adult donor's own tissues, meaning less chance of a tumour/ rejection by body. Cons: Only a limited capacity to differentiate, less growth potential & difficult to obtain (bone marrow, skin & liver)
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What are pros & cons of umbilical cord blood stem cells?
Pros: umbilical cord is normally discarded whether or not cells are taken. Cons: newborn babies cannot give informed consent for cells to be taken from umbilical cord (although parents can).
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What are the 2 textbook therapeutic uses of stem cells (SCs)?
Stargardt's disease (muscular dystrophy) genetic disease in children, loss of vision. Embryonic SCs injected into eyes & develop into retina cells. Leukaemia: cancer cells cause excess of WBCs. Adult SCs from pelvis marrow, give them chemo, reinject
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Define 'resolution'
the smallest distance between 2 objects at which they can still be distinguished
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Define 'magnification'
the increase in size of an image until the point above which the image can no longer be focused sharply
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What is a micrograph?
A photograph taken down the microscope
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What is the formula for calculating magnification?
Magnification= size of Image/ size of Actual specimen (MIA)
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How many mm in a um?
1000 (e.g. 1mm=1000um & 1um=0.001)
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Why do electron micrographs have a better resolution than light micrographs?
Because electrons have a much shorter wavelength.
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Outline features (i.e. things about it) of prokaryotic cells (3)
Simple cell structure "before nucleus" (not compartmentalised); no membrane bound organelles (free DNA called 'nucleoid'; replicates by binary fission
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What are structures of a prokaryote that a eukaryote doesn't have? (4)
Flagellum, 70S ribosomes, naked DNA, pili
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Outline how prokaryotes replicate
Binary fission (splitting in two). DNA & organelles are replicated & move to opposite poles of cell. Cell wall & plasma membrane are pulled inwards so the cell pinches apart to form 2 identical cells.
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What is the advantage of compartmentalisation in eukaryotes?
Biochemical reactions (using enzymes & substrates) can be concentrated in a small area & separated from each other.
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