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Biology > B6 - Cell division > Flashcards

B6 - Cell division Flashcards

1
Q

What are the phases of the cell cycle?

A
  • interphase
  • mitotic (division) phase
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2
Q

What takes place during interphase?

A
  • DNA replication/checked
  • protein synthesis
  • mitochondria grow/divide
  • chloroplasts grow/divide
  • metabolic processes occur
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3
Q

What are the three stages of interphase?

A
  • G1= first growth phase
    • proteins are synthesised
    • organelles replicate
    • mRNA made
    • cell increases in size
  • S = synthesis phase
    • DNA is replicated in nucleus (produces chromatids)
  • G2 = second growth phase
    • cell continues to increase in size
    • energy stores increased
    • duplicated DNA is checked for errors
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4
Q

What are the three checkpoints of the cell cycle?

A
  • G1 checkpoint = end of G1
    • cell size
    • nutrients
    • growth factors
    • DNA damage
  • if it does not meet the requirements, it enters the G0 phase (resting state)
  • G2 checkpoint = end of G2
    • cell size
    • DNA replication
    • DNA damage
  • spindle assembly = metaphase checkpoint
    • all chromosomes should be attached to spindles/aligned
    • mitosis cannot proceed until this checkpoint is passed
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5
Q

What is G0?

A
  • phase where a cell leaves the cycle (temporarily/permanently)
    • differentiation = specialised cells are unable to divide (will not enter cell cycle again)
    • damaged DNA = unable to divide and enters period of permanent arrest
    • number of (senescent) cells increases as you age, which has been linked to diseases such as cancer/arthritis
  • lymphocytes are able to go back into cell cycle in an immune response
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6
Q

What is the mitotic phase?

A
  • mitosis = the division of the nucleus
  • cytokinesis = cytoplasm divides and two cells are produced
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7
Q

Why is mitosis important?

A
  • growth
  • tissue repair
  • asexual reproduction in plants, animals, fungi
  • replacement of old cells
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8
Q

What are the main stages of mitosis?

A
  • prophase
  • metaphase
  • anaphase
  • telophase
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9
Q

What happens during prophase?

A
  • chromatins condense to form chromosomes (not visible during interphase)
  • nucleolus disappears and nuclear envelope breaks down
  • protein microtubules form spindle fibres, linking the poles of the cell
  • centrioles (protein bundle) move to opposite poles
  • spindle fibres attach to centromeres and begin to move the chromosomes
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10
Q

What happens during metaphase?

A
  • the spindle fibres move the chromosomes to the centre of the cell
  • forms a metaphase plate and is held in position
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11
Q

What happens during anaphase?

A
  • the centromeres divide, separating each pair of sister chromatids
  • the spindle fibres shorten and pull the chromatids to opposite sides of the cell
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12
Q

What happens during telophase?

A
  • the chromatids are now called chromosomes
  • nuclear envelope reforms around them
  • chromosomes uncoil and nucleolus forms
  • nuclei are genetically identical to each other
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13
Q

What is cytokinesis?

A
  • the division of the cytoplasm
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14
Q

What happens during cytokinesis in animal cells?

A
  • cleavage furrow forms around centre of cell
  • cytoskeleton pulls the cell membrane inwards to fuse around the middle
  • forms two new cells
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15
Q

What happens during cytokinesis in plant cells?

A
  • vesicles from Golgi apparatus assemble where the metaphase plate was formed (centre of cell)
  • vesicles/cell membrane fuse together and forms two new cells
  • new sections of cell wall form along new cell membrane
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16
Q

What is meiosis?

A
  • the formation of gametes (haploid)
  • a gamete contains half the chromosome of parent cell
    • fertilised egg = zygote
  • reduction division
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17
Q

Why is meiosis important?

A
  • produces genetically unique daughter cells
    • crossing over
    • independent assortment
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18
Q

What are homologous chromosomes?

A
  • matching sets of chromosomes (in nucleus)
    • diploid
  • each chromosome in the pair has the same genes at the same position
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19
Q

What are the stages of meiosis?

A
  • meiosis I (first division - reduction)
  • meiosis II (similar to mitosis
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20
Q

What happens during meiosis I?

A
  • prophase I:
    • chromosomes condense and nucleolus disappears
    • homologous pairs pair up and form bivalents
    • when moving through the cytoplasm, crossing over takes place as chromatids tangle
      ‎
  • metaphase I:
    • pairs of chromosomes assemble along metaphase plate
    • orientation of the pairs are random and independent (independent assortment)
      ‎
  • anaphase I:
    • the chromatids are still joined together when pulled to opposite poles
    • they then break off and rejoin (forms recombinant chromatids)
      ‎
  • telophase I:
    • chromosomes assemble at each pole and nuclear membrane reforms
    • cell undergoes cytokinesis and forms two cells
21
Q

What happens during meiosis II?

A
  • prophase II:
    • chromosomes condense and become visible
    • spindle formation begins
      ‎
  • metaphase II:
    • individual chromosomes assemble at metaphase plate
    • more independent assortment/genetic variation
      ‎
  • anaphase II:
    • chromatids of individual chromosomes are pulled to opposite poles
      ‎
  • telophase II:
    • chromatids assemble at each pole
    • chromosomes uncoil and nuclear envelope reforms
    • cytokinesis forms four genetically unique daughter cells
22
Q

What are specialised cells?

A
  • cells that are differentiated (adapted to carry out specific functions)
23
Q

How are erythrocytes specialised?

A
  • flattened biconcave shape = increases SA:V
  • no nuclei = increases space for haemoglobin
  • flexible = able to squeeze through capillaries
24
Q

How are neutrophils specialised?

A
  • multi-lobed nucleus = can squeeze through small gaps
  • granular cytoplasm = contains lysosomes (enzymes to attack pathogens)
25
Q

How are sperm cells specialised?

A
  • flagellum/many mitochondria = movement/swimming
  • digestive enzymes in head = digest layers around ovum
26
Q

How are palisade cells specialised?

A
  • chloroplasts (can move around) = photosynthesis
  • box shape = can be closely packed together
  • thin cell walls = increase rate of CO2 diffusion
  • large vacuole = maintains turgor pressure
27
Q

How are root hair cells specialised?

A
  • root hairs = increase SA of cell (maximises uptake of water and minerals)
28
Q

How are guard cells specialised?

A
  • lose water = closes stomata to prevent further water loss
  • thicker on one side = cell does not change shape symmetrically
29
Q

What are tissues?

A
  • collection of differentiated cells that have a specialised function
30
Q

What are the main tissues in animals?

A
  • nervous = transmission of electrical impulses
  • epithelial = cover body surfaces
  • muscle = contract
  • connective = hold other tissues/transport medium
31
Q

How is squamous epithelium specialised?

A
  • very thin = rapid diffusion
  • (forms lining of lungs)
32
Q

How is ciliated epithelium specialised?

A
  • hair-like features = sweeps away mucus from lungs
  • goblet cells = secrete mucus to trap air particles
33
Q

How is cartilage specialised?

A
  • contains fibres of elastin/collagen = firm and flexible
  • prevents ends of bones rubbing
34
Q

How is muscle specialised?

A
  • (skeletal) contain myofibrils = allow for contraction
  • help to move bones in body
35
Q

What are the main tissues in plants?

A
  • epidermis = cover plant surfaces
  • vascular = transport of water/nutrients
36
Q

How is epidermis specialised?

A
  • waxy cuticle = prevents water loss
  • stomata = allow CO2/H2O/O2 in and out
37
Q

How is xylem tissue specialised?

A
  • vessel elements = transport water/minerals
  • lignified walls = structural support
38
Q

How is phloem tissue specialised?

A
  • columns of sieve tube cells (sieve plates) = transport of organic nutrients
39
Q

What is an organ?

A
  • collection of tissues adapted to perform a particular function
40
Q

What are the organ systems in animals?

A
  • digestive = breaks down large insoluble molecules and absorbs nutrients
  • cardiovascular = moves blood around body
  • gaseous exchange = brings air into body
41
Q

What are stem cells?

A
  • undifferentiated cells that have the potential to become one of the specialised cell types
    • able to undergo cell division multiple times
    • (uncontrolled division can cause development of cancer)
42
Q

What are the different stem cell potencies?

A
  • totipotent = can differentiate into any type of cell
  • pluripotent = can form all tissue types but not whole organisms
  • multipotent = can only form a range of cells found within a certain type of tissue
43
Q

What is differentiation?

A
  • when cells become adapted to their specific role
44
Q

What are the sources of animal stem cells?

A
  • embryonic:
    • present at early stages of embryo development (totipotent)
    • blastocyst = pluripotent
  • adult:
    • present throughout life
    • can be found in bone marrow
    • multipotent
    • can also be derived from umbilical cords
45
Q

How are erythrocytes and neutrophils produced?

A
  • formed from bone marrow stem cells
  • erythrocytes = lose nucleus, builds up haemoglobin
  • neutrophils = indentations of nucleus, granules accumulate
46
Q

How are xylem vessels and phloem sieve tubes produced?

A
  • from cambium
  • xylem = lose cytoplasm, deposit lignin, lose end walls
  • phloem = lose some cytoplasm/organelles, develop sieve plates
47
Q

What are the sources of plant stem cells?

A
  • meristematic tissue (found wherever growth is occurring (roots/shoots))
  • located between phloem and xylem tissues (cambium)
  • pluripotent
48
Q

What are the uses of stem cells?

A
  • repair of damaged tissues
  • treatment of neurological conditions:
    • Parkinson’s
    • Alzheimer’s
  • developmental biology:
    • study of the changes that occur as multicellular organisms grow/develop
49
Q

What are ethical issues surrounding stem cells?

A
  • embryonic stem cells destroys ‘life’
  • lack of consent

Biology (18 decks)

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