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Alevel Biology OCR > 2.1.6 - Cell Division and Cellular Organisation > Flashcards

2.1.6 - Cell Division and Cellular Organisation Flashcards

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1
Q

What is the cell cycle?

A

the sequence of events that takes place in a cell for its growth and division

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2
Q

What are the stages of the cell cycle?

A 
Interphase 
-G1
-Synthesis
-G2
Mitotic phase 
-mitosis
-cytokinesis
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3
Q

What happens during the first growth phase (G1) of the cell cycle?

A
  • proteins are produced
  • organelles are replicated
  • cell size increases
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4
Q

What happens during synthesis in the cell cycle?

A

the DNA is replicated in the nucleus

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5
Q

What does the G1 checkpoint check for?

A
  • cell damage

- cell size

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6
Q

What happens during the second growth phase (G2) of the cell cycle?

A

cell continues to increase in size

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7
Q

What does the G2 checkpoint check for?

A

errors in replicated DNA

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8
Q

What happens in cytokinesis in the cell cycle?

A

cytoplasm divides in two (to produce two cells)

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9
Q

What is G0?

A

the phase where a cell leaves the cell cycle

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10
Q

Why might a cell leave the cell cycle (G0)?

A
  • differentiation (cell becomes specialised so no longer needs to divide)
  • DNA may be damaged (no longer viable)
  • aging
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11
Q

What is mitosis?

A

nuclear division to produce two genetically identical daughter cells

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12
Q

What is mitosis needed for?

A
  • growth
  • tissue repair
  • asexual reproduction
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13
Q

What are the stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

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14
Q

What happens during prophase in mitosis?

A
  • chromosomes coil and condense
  • nucleus disappears (nuclear envelope disintegrates and nucleolus becomes less prominent)
  • centrioles move to opposite sides of the cell and start to produce spindle fibres
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15
Q

What happens during metaphase in mitosis?

A

-spindle fibres continue to grow and attach to the centromeres of the chromosomes
-chromosomes are moved to line up on the metaphase plate (equator of the cell)
CHECKPOINT -> checks all chromosomes are attached to the spindle

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16
Q

What happens during anaphase in mitosis?

A
  • centromeres divide, causing sister chromatids to separate

- spindle fibres contract (shorten), pulling chromatids to opposite poles of the cell

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17
Q

What happens during telophase in mitosis?

A
  • chromatids reach the poles of the cell
  • chromatids uncoil (become longer and thinner)
  • nuclear envelope reforms around each group of chromosomes (forming two nuclei)
  • nucleolus form
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18
Q

What is meiosis?

A

cell division where the nucleus divides twice, to produce 4 haploid daughter cells

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19
Q

What is a haploid cell?

A

a cell containing only a single set of chromosomes (half the normal amount)
-23 chromosomes in humans

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20
Q

What is a somatic cell?

A

a normal human cell containing 46 chromosomes (23 homologous chromosomes)
-diploid

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21
Q

What is a zygote?

A

a fertilised egg cell

-two gametes fused

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22
Q

What is a gamete?

A

a sex cell

  • is haploid (has 23 chromosomes)
    eg. egg, sperm cell
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23
Q

What is meiosis needed for?

A
  • to produce gametes
  • to half the number of chromosomes
  • to create variation
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24
Q

How does meiosis create genetic variation?

A
  • crossing over (homologous pairs of chromosomes swap) during prophase 1
  • independent assortment (chromosomes from each pair are randomly allotted to daughter cells) in metaphase 1 and 2
25
Q

What happens during prophase 1 in meiosis?

A
  • chromosomes coil and condense
  • nucleus disappears (nuclear envelope disintegrates and nucleolus becomes less prominent)
  • homologous chromosomes pair up (forming bivalents)
  • centrioles move to opposite sides of the cell and start to produce spindle fibres
  • crossing over occurs
26
Q

What happens during metaphase 1 in meiosis?

A
  • spindle fibres continue to grow and attach to the centromeres of the chromosomes
  • homologous pairs are lined up at metaphase plate (equator of the cell)
  • independent assortment occurs
27
Q

What happens during anaphase 1 in meiosis?

A
  • spindle fibres contract

- chromosomes are pulled to poles (not pulled apart -unlike in mitosis)

28
Q

What happens during telophase 1 in meiosis?

A
  • chromosomes reach the poles of the cell
  • chromosomes uncoil (become longer and thinner)
  • nuclear envelope reforms around each group of chromosomes (forming two nuclei)
  • nucleolus forms
29
Q

What happens during prophase 2 in meiosis?

A
  • chromosomes re-condense
  • nucleus disappears (nuclear envelope disintegrates and nucleolus becomes less prominent)
  • spindle fibres reform
  • no crossing over occurs (unlike prophase 1)
30
Q

What happens during metaphase 2 in meiosis?

A
  • spindle fibres continue to grow and attach to the centromeres of the chromosomes
  • chromosomes are lined up at metaphase plate (equator of the cell)
  • independent assortment occurs again
31
Q

What happens during anaphase 2 in meiosis?

A
  • centromeres divide, causing sister chromatids to separate (like anaphase in mitosis)
  • spindle fibres contract (shorten), pulling chromatids to opposite poles of the cell
32
Q

What happens during telophase 2 in meiosis?

A
  • chromatids reach the poles of the cell
  • chromatids uncoil (become longer and thinner)
  • nuclear envelope reforms around each group of chromosomes (forming two nuclei)
  • nucleolus forms
33
Q

What is crossing over?

A

when homologous pairs of chromosomes swap parts of genetic material

  • chromatids twist around eachother and break
  • same genes/different alleles get swapped
  • occurs during prophase 1 in meiosis
34
Q

What is independent assortment?

A

the fact that the position of each bivalent is independent to all the other chromosomes

  • maternal/paternal chromosomes can be on either side of the equator
  • occurs during metaphase 1 and 2 in meiosis
35
Q

What is a homologous chromosome?

A

a matching pair of chromosomes (one from each parent)

36
Q

What is a bivalent?

A

a pair of homologous chromosomes

37
Q

How does cytokinesis happen in animal cells?

A
  • constriction from edges of cell

- cytoskeleton pulls membrane inwards

38
Q

How does cytokinesis happen in plant cells?

A

-vesicles line up along centre and fuse to develop a cell plate, which becomes a cell wall

39
Q

What are erythrocytes, their role and their adaptions?

A

red blood cells

  • transport oxygen around the body
  • flattened biconcave shape (increases SA:V)
  • no nuclei + few organelles (more space for haemoglobin)
  • flexible (can squeeze through narrow capillaries)
40
Q

What are neutrophils, their role and their adaptions?

A

type of phagocyte (type of white blood cells)

  • engulf and destroy pathogens
  • multi-lobed nucleus (can squeeze through gaps to get to infection sites)
  • granular cytoplasm containing lysosomes (have enzymes that attack pathogens)
41
Q

What are sperm cells, their role and their adaptions?

A

male gametes

  • tail/flagellum (used for movement -energy for movement is provided by lots of mitochondria)
  • acrosome (on sperm’s head) contains digestive enzymes (used to digest protective layers around the egg to allow fertilisation)
42
Q

What are palisade cells, their role and their adaptions?

A

plant cells present in the mesophyll

  • chloroplasts (absorb lots of sunlight for photosynthesis)
  • regular shape (pack closely together in rows)
  • large vacuole (maintains turgor pressure)
43
Q

What are root hair cells, their role and their adaptions?

A

cells present on surfaces of roots, near the tips

-long extensions/hairs (increase SA to maximise uptake of minerals and water from the soil

44
Q

What are guard cells, their role and their adaptions?

A

found on the surfaces of leaves in pairs, which form small holes called stomata (which allow carbon dioxide to enter plant)

  • when they loose water, they become less swollen and change shape (causes stomata to close to prevent water loss)
  • cell wall is thicker on one side (cell doesn’t change shape symmetrically when volume changes)
45
Q

What is the squamous epithelium, its role and its adaptions?

A

tissue present where rapid diffusion across a surface is essential (eg. lung linings)

  • made up of specialised squamous epithelial cells
  • very thin (made up of single layer of flat cells -increases rate of diffusion)
46
Q

What is the ciliated epithelium, its role and its adaptions?

A
  • made up of ciliated epithelial cells which have cilia (hair like structures which move in a rhythmic way)
  • goblet cells are also present (release mucus to trap unwanted particles -eg. pathogens, dust, etc)
47
Q

What is cartilage, its role and its adaptions?

A

connective tissue found in outer ear, nose, between bones

  • prevents bones from rubbing and causing damage
  • contains elastin and collagen fibres
  • firm and flexible
  • made up of chondrocyte cells embedded in a matrix
48
Q

What is muscle, its role and its adaptions?

A

tissue that contracts in order to move body parts

-different types of muscle fibres (eg. skeletal fibres -contain myofibrils containing contractile proteins)

49
Q

What is the epidermis, its role and its adaptions?

A

tissue covering surfaces of plants made up of closely packed cells

  • covered by waxy cuticle (reduces water loss)
  • stomata (gaseous exchange)
50
Q

What is the xylem, its role and its adaptions?

A

vascular tissue responsible for transporting water and minerals through plants

  • made up of vessel elements (elongated dead cells)
  • lignin (strengthens walls of dead cells to provide support)
51
Q

What is the phloem, its role and its adaptions?

A

vascular tissue responsible for transporting assimilates (organic substances eg. sucrose) throughout a plant
-composed of sieve tube elements separated by sieve plates

52
Q

What are stem cells?

A

undifferentiated cells which can differentiate into any specialised cell

53
Q

What is potency?

A

the ability that stem cells have to differentiate into different cells

54
Q

What does totipotent mean?

A

can differentiate into any cell

55
Q

What does pluripotent mean?

A

can differentiate all tissue types (but not a whole organism)

56
Q

What does multipotent mean?

A

can only differentiate into a range of cells (within a certain type of tissues)

57
Q

What sources are there for stem cells?

A
  • embryotic stem cells (toti/pluripotent)
  • adult tissue stem cells (multipotent)
  • meristem tissue (pluripotent)
58
Q

What potential uses are there for stem cells?

A
  • repair of damaged tissues
  • treatment of neurological conditions (eg. Alzheimer’s and Parkinson’s)
  • research into developmental biology.
59
Q

What are the benefits of being a multicellular organism?

A
  • can make use of resources more efficiently

- cells are adapted to different roles (different shapes/sizes + different organelles)

Alevel Biology OCR (26 decks)

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