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a-level biology > 2.1.6 Cell Division, Cell Diversity and Cellular Organisation > Flashcards

2.1.6 Cell Division, Cell Diversity and Cellular Organisation Flashcards

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1
Q

stages of the cell cycle

A

g1 - growth
s - synthesis
g2 - growth, preparation for cell division
mitosis or meiosis - nuclear division
cytokinesis - division of the cell

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2
Q

Gap 1 Stage of Cell Cycle

A

cell increases in volume
protein synthesis - produces enzymes used in DNA replication - produces growth factors
organelle replication

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3
Q

Synthesis Stage of Cell Cycle

A

DNA replication
ensures twice the original DNA
each daughter cell receives 1/2

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4
Q

Gap 2 Stage of Cell Cycle

A

cell increases in volume
energy stores increase
synthesising key proteins for cell division

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5
Q

Checkpoints in the Cell Cycle

A

G1/S checkpoint
G2/S checkpoint
Metaphase checkpoint

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6
Q

G1/S Checkpoint in Cell Cycle

A

checks for DNA damage
checks cell is large enough

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7
Q

G2/S Checkpoint in Cell Cycle

A

checks for correct DNA replication

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8
Q

Metaphase Checkpoint

A

spindle assembly checkpoint
checks spindle fibres are correctly attached to chromosomes

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9
Q

Cytokinesis in Cell Cycle

A

division of the cell
cell cytoplasm divides in 2

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10
Q

why is interphase not a resting phase

A

significant metabolic activity is taking place

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11
Q

which type of cells could be considered to be in a resting phase

A

cells that are not actively dividing

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12
Q

significance of mitosis in life cycles

A

production of stem cells
tissue growth and repair
asexual reproduction
clonal expansion of lymphocytes
development of body plan

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13
Q

prophase in mitosis

A

chromatin condenses - chromosomes become visible
nuclear envelope breaks down
nucleolus disappears
centrioles migrate to opposite poles of the cell
spindle fibres start to form

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14
Q

metaphase in mitosis

A

spindle fibres attach to the centromeres of each pair of sister chromatids
chromosomes line up along equator
-metaphase checkpoint-

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15
Q

anaphase in mitosis

A

spindle fibres shorten + pull sister chromatids apart and separates them to opposite poles - REQ. ATP
centromere has divided

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16
Q

telophase in mitosis

A

full set of chromosomes at each pole of the cell
nuclear membrane forms around each set of chromosomes + nucleolus reappears
chromosomes uncoil into chromatin

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17
Q

cytokinesis in an animal cell

A

cleavage furrow forms down centre of the cell
actin microfilaments contract (req. ATP) and separates 2 cells by pinching plasma membrane together - 2 genetically identically daughter cells

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18
Q

cytokinesis in a plant cell

A

vesicles containing cellulose are deposited at cell plate
cellulose molecules hydrogen bond together - microfibrils - macrofibrils
cell spilts

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19
Q

what is a stem cell

A

undifferentiated, unspecialised
self renewing
potential to become a specialised cell

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20
Q

where can stem cells be obtained

A

bone marrow
tissues
embryos

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21
Q

which types of cells can embryonic stem cells differentiate into

A

any type of specialised cell
heart, blood, brain, skin
NOT PLACENTA/UMBILICAL CORD

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22
Q

how can stem cells be used in the treatment of burns

A

use a sample of undamaged skin
put in a culture + feed it
implant onto burn

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23
Q

roles of stem cells in the body

A

repairing wounds
replacing old red blood cells

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24
Q

totipotent stem cells

A

extracted from 1-32 cells of embryo
can differentiate into ALL types of cell
has ability to form whole living organisms

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25
Q

pluripotent stem cells

A

extracted from 64-256 cells of embryo
can differentiate into most cell types
not placental/umbilical cord cells

26
Q

multipotent stem cells

A

in bone marrow - haematopoietic
can differentiate into some cell types
blood cells: phagocytes, lymphocytes, erythrocytes

27
Q

unipotent stem cells

A

only differentiate into 1 cell type

28
Q

induced pluripotent stem cells (iPSCs)

A

reprogramme differentiated cells to become embryonic/pluripotent stem cells
potential in areas like regenerative medicine

29
Q

uses of stem cells in medicine

A

developmental biology
regenerative medicine
treating neurodegenerative diseases
repair of damaged tissues

30
Q

prophase 1 of meiosis 1

A

chromatin condenses - chromosomes become visible
nuclear envelope breaks down
nucleolus disappears
spindle fibres start to form

31
Q

crossing over - variation in prophase 1 of meiosis 1

A

non-sister chromatids within the same homologous pair exchange short sections of DNA
forms new combinations of alleles

32
Q

metaphase 1 of meiosis 1

A

each homologous pair lines up along the equator
spindle fibres attach to centromeres

33
Q

independent assortment - variation in metaphase 1 of meiosis 1

A

orientation of each homologous pair along the equator is random
more possible combinations of alleles in daughter cells

34
Q

anaphase 1 of meiosis 1

A

spindle fibres shorten and separate each member of a homologous pair to opposite poles
centromere remains intact

35
Q

telophase 1 of meiosis 1

A

unpaired chromosomes at each pole
nuclear envelope reforms
nucleolus reappears
chromosomes relax for cytokinesis to occur

36
Q

before vs after meiosis 1

A

before: 1 parent cell, 46 chromosomes, 92 chromatids (after S phase)
after: 2 haploid daughter cells with 23 chromosomes, 46 chromatids

37
Q

stages before meiosis 2

A

a short cell cycle occurs but without DNA replication

38
Q

prophase 2 of meiosis 2

A

chromatin condenses
chromosomes become visible
nuclear envelope breaks down
nucleolus disappears
spindle fibres start to form

39
Q

metaphase 2 of meiosis 2

A

chromosomes line up along equator
spindle fibres attach to centromeres

40
Q

independent assortment - variation in metaphase 2 of meiosis 2

A

random orientation of chromosomes along the equator, which determines which daughter cell each sister chromatid is separated to - produces new combinations of alleles in daughter cells

41
Q

anaphase 2 of meiosis 2

A

spindle fibres shorten
centromere divides
sister chromatids are pulled to opposite poles

42
Q

telophase 2 of meiosis 2

A

nuclear membrane forms around each set of chromatids at each pole
nucleolus reappears
chromatids relax

43
Q

significance of meiosis in life cycles

A

production of haploid cells
produce genetic variation by independent assortment and crossing over

44
Q

homologous chromosomes

A

pairs of chromosomes that contain the same genetic information

45
Q

how are erythrocytes adapted to carry out their function?

A

very small = large SA:V ratio: oxygen can diffuse across membranes easily
biconcave shape: increases SA:V ratio
elastic membrane - flexible: allows cell to change shape, twist & turn through narrow capillaries
little organelles: provides more space for Hb moleucles

46
Q

function of erythrocytes

A

carry oxygen from the lungs to respiring cells

47
Q

function of neutrophils

A

destroy pathogens by phagocytosis and the secretion of enzymes

48
Q

how are neutrophils adapted to carry out their function?

A

flexible/mutilobed nucleus: allows cells to squeeze through cell junctions in the capillary wall
lots of lysosomes: digestive enzymes help to digest and destroy invading cells

49
Q

function of sperm cells

A

reproduction - to fuse with an egg, initiate the development of an embryo and pass on paternal genes

50
Q

how are sperm cells adapted to carry out their function?

A

many mitochondria: site of aerobic repiration to provide ATP for movement
acrosome contains digestive enzymes: can break down the outer layer of an egg cell
tail: propells cell forwards, allowing it to move towards the egg

51
Q

function of squamous epithelial cells

A

ensure efficient gas exchange

52
Q

how are squamous epithelial cells adapted to carry out their function?

A

thin cross-section of cells: reduces diffusion distance that substances pass through
permeable: allows easy diffusion of gases

53
Q

function of ciliated epithelial cells

A

maintains health of gas exchange system
move substances across the surface of tissues

54
Q

how are ciliated epithelial cells adapted to carry out their function?

A

cilia (hair-like structures): beat in a coordinated way - wafts material along surface of epithelium tissue
goblet cells: secrete mucus - helps to trap dust, dirt and microorganisms - preventing them from entering vital organs, causing infection

55
Q

function of palisade cells

A

carry out photosynthesis to produce glucose and oxygen

56
Q

how are palisade cells adapted to carry out their function?

A

lots of chloroplasts: maximise the absorption of light for photosynthesis
tall and thin shape: allows light to penetrate deeper, many cells can be densely packed together

57
Q

function of root hair cells

A

absorption of water and mineral ions from soil

58
Q

how are root hair cells adapted to carry out their function?

A

root hair: increases SA, so the rate of water uptake by osmosis is greater
thin walls: short diffusion distance, water can move through easily
permanent vacuole contains cell sap: more concentrated than soil water, maintains water potential gradient
mitochondria: active transport of mineral ions

59
Q

function of guard cells

A

control the opening of the stomata to regulate water loss and gas exchange

60
Q

how are guard cells adapted to carry out their function?

A

inner cell walls are thicker than outer cell walls: allows the cell to bend when turgid
high density of chloroplasts and mitochondria: play a role in the opening of the stomata

a-level biology (26 decks)

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