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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

the cell cycle

A 
M phase (mitosis)
cytokinesis
interphase (G1, S, G2)
repeat cycle
G0
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2
Q

G0 (gap 0) phase

A

resting phase
where differentiated cells or stem cells (waiting to divide stay) (temporary/lifetime)
may differentiate, apoptosis, senescence

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3
Q

M phase

A 
cell growth stops
nuclear division (mitosis) and cytokinesis (cytoplasmic division)
checkpoint chemical triggers condensation of chromatin
metaphase checkpoint makes sure cell can complete mitosis
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4
Q

senescence definition

A

irreversible end of cell growth

helps suppress development of cancer

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5
Q

G1 (gap 1) phase

A

“growth phase”
G1 checkpoint makes sure cell is ready to enter S phase
carries out growth and normal cell functions
makes enzymes needed for DNA replication in S phase
p53 gene (tumour suppressor) helps control phase
(aerobic respiration, biosynthesis)

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6
Q

biosynthesis definition

A

production of complex molecules within living organisms or cells
e.g. protein synthesis, organelle repair in animal cells

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7
Q

S (synthesis) phase

A

committed to complete cell cycle once entering S phase
DNA replicates (most important sequences of DNA replicated first)
chromosomes consists of a pair of identical sister chromatids
rapid (reduces chances of spontaneous mutations)

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8
Q

why S phase is rapid

A

exposed DNA base pairs more susceptible to mutagenic agents

reduces likelihood of spontaneous mutations happening

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9
Q

G2 (gap 2) phase

A

copied DNA checked by proof-reading enzymes

if not copied properly, mutations arise and new cells may not work properly / be cancerous

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10
Q

what happens during cytokinesis

A

cytoplasm cleaves (divides) to form 2 distinct daughter cells ready to begin cell cycle

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11
Q

importance of mitosis in life cycle

A

asexual reproduction: produces genetically identical offspring, mostly single-called organisms
growth: produces more genetically identical cells
tissue repair: growth factor stimulates proliferation of cells for repair

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12
Q

mitosis stages

A 
just nuclear division 
prophase
metaphase
anaphase 
telophase
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13
Q

prophase method

A

sister chromatids coil and condense (visible under light microscope)
nuclear envelope breaks down
spindle fibres begin to form from centrioles

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14
Q

metaphase method

A

chromatids attach to spindle fibres (via centromeres)

line up on equator of cell

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15
Q

anaphase method

A

centromere of each pair of chromatids split

motor proteins on spindle fibres pull sister chromatids apart to opposite poles of cell

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16
Q

telophase method

A

separated chromosomes reach opposite poles
nuclear envelope reforms around each set of chromosomes
cell contains two nuclei genetically identical to each other and the parent cell from which they arose

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17
Q

cytokinesis method

A

plasma membrane folds inwards and “nips in” along “cleavage furrow” of cytoplasm (animal cell)
cell plates forms where equator of spindle was, new plasma membrane and cell wall laid down either side of end plate
bulge formed, nucleus goes into bulge and pinches off, leaving bud scars (budding, yeast)

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18
Q

importance of meiosis

A

produces haploid gametes for sexual reproduction
combines genetic material from two (usually) unrelated members of same species (fertilisation)
increases genetic variation
increases chances of survival of population (some individuals have characteristics to better adapt to environmental changes)

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19
Q

homologous chromosome definition

A

same genes but different alleles

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20
Q

allele definition

A

variant of the same gene

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21
Q

meiosis order

A

first meiotic division (prophase 1, metaphase 1, anaphase 1, telophase 1)
short interphase
second meiotic division perpendicular to first meiotic division (prophase 2, metaphase 2, anaphase 2, telophase 2)
cytokinesis

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22
Q

prophase 1

A

chromatin condenses and supercoils
nuclear envelope breaks down
spindle fibres form from centrioles
chromatids come together in homologous pairs
crossing over occurs (non-sister chromatids wrap around each other, may swap sections, shuffling alleles)

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23
Q

metaphase 1

A

crossed-over homologous pairs of chromatids up along equator of spindle
each attaches to spindle fibres by centromere
arranged randomly, members of each pair facing opposite poles of cell (independent arrangement)

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24
Q

anaphase 1

A

crossed-over homologous pulled apart by motor proteins along spindle fibres
crossed-over areas of homologous pairs separate (alleles are shuffled)

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25
telophase 1
two nuclear envelopes reform around each set of chromosomes cytokinesis then a short interphase (chromosomes uncoil) each new nucleus contains half number of original set of chromosomes each chromosomes made up of 2 chromatids in most plant cells, goes straight from anaphase 1 to prophase 2
26
prophase 2
nuclear envelopes break down if reformed previously chromosomes coil and condense (made up of 2 non-identical chromatids) spindles form
27
metaphase 2
chromosomes attach by centromeres to equator of spindle | chromatids of chromosomes randomly arranged
28
anaphase 2
centromeres divide chromatid of each chromosome pulled apart by motor proteins along tubulin threads on spindle towards opposite poles chromatids randomly segregated
29
telophase 2
nuclear envelope reforms around each of 4 haploid cells two cells divide to form 4 haploid cells (animals) tetrad of 4 haploid cells formed (plants)
30
how meiosis produces genetic variation
crossing over prophase 1 shuffles alleles independent assortment of chromosomes in metaphase 1 randomly distributes maternal and paternal chromatid pairs (either one of the homologous pair can face either end of the cell) independent assortment of chromatids in metaphase 2 further random distribution of genetic material gametes produced fuse with random gamete of another member of same species
31
important of differentiation/specialisation
direct diffusion with environment not sufficient for multicellular organisms’ innermost layer of cells also smaller SA:V ratio also more active (need more nutrients and faster waste exchange for more aerobic respiration)
32
zygote definition
when an ovum(egg cell) is fertilised by sperm cell | haploid nuclei fuse to form diploid nucleus to form totipotent stem cell
33
how cells differentiate
``` certain genes are expressed or switched off changes in: -proportion of different organelles -shape of cell -contents of the cell ```
34
totipotent definition
can differentiate into any cell
35
pluripotent definition
can differentiate into 200 different cell types
36
multipotent definition
can differentiate into a limited range of cells
37
differentiation definition
changes occurring in cells of a multicellular organism so that each different type of cell becomes specialised to perform a specific function
38
clone definition
genetically identical cells or organisms derived from one parents (e.g. asexual reproduction)
39
vegetative propagation definition
plants asexual reproduction
40
how bacteria divide
``` binary fission not mitosis (no nucleus) ```
41
how RBCs differentiate
enucleated (lose nucleus) and other organelles (maximises space for haemoglobin, adds flexibility to squeeze through capillaries) filled with haemoglobin shape becomes biconcave (larger SA for faster gas exchange)
42
how neutrophils differentiate
produce more lysosomes (why it looks grainy, more phagocytosis) nucleus becomes multi-lobed (flexibility of cell)
43
how sperm cells differentiate
``` becomes haploid (so zygote is diploid) tail (undilipodium) formed (helps sperm cell to move towards egg more mitochondria (more energy to move flagellum) shape becomes long and thin (more streamlined for ease of movement) acrosome formed (contains enzymes so sperm can penetrate egg for fertilisation) ```
44
how root hair cells differentiate
``` hair-like structure (larger SA for AT/diffusion of minerals and water) thinner cell wall (shorter diffusion distance) more mitochondria (more energy for AT) no chloroplast (no photosynthesis so not needed) ```
45
how palisade cells differentiate
``` contain more chloroplast (more photosynthesis) contain cytoskeleton threads and motor proteins (moves chloroplasts up and down depending on sunlight intensity) larger vacuole (pushes chloroplast to peripheries of cell, shorter diffusion distance of CO2) long and cylindrical (packed tight together, shorter diffusion distance for CO2 between cells) ```
46
how guard cells differentiate
thickened, more rigid inner wall than outer wall (allows closing and opening of stomata)
47
4 main tissue types in human body
``` epithelial (lining) tissue connective tissue (holds structure together and provide support) muscle tissue (cells contract and cause movement) nervous tissue (cell conduct electrical impulses) ```
48
epithelial tissue in animals features
specialised for protection, absorption,filtration excretion, secretion short cell cycles (divide 2-3 times a day) smooth but may have cilia made up of almost all cells no blood vessels (nutrients via diffusion from tissue fluid in connective tissue) cells very close together (continuous sheets)
49
connective tissue features
blood, bone, cartilage, tendons, ligaments skin | non-living extracellular matrix (proteins, polysaccharides) that separates cells, allows to withstand forces
50
cartilage features
chondroblasts: immature, divide by mitosis, secrete extracellular matrix, develop into chondrocytes that maintain matrix hyaline cartilage: forms embryonic skeleton, covers ends of long bones (adults), joins ribs to sternum, in nose, trachea and larynx (voice box) fibrous cartilage: disc between vertebrae in spine and knee joint elastic cartilage: makes up outer ear and epiglottis (flap over larynx)
51
muscle tissue features
well vascularised | muscle cells = fibres (contain myofilamentd made up of actin and myosin to allow for contraction)
52
functions of muscle
skeletal muscle: allows movement of bones cardiac muscle: makes up walls of heart to pump blood around body smooth muscle: walls of intestine, blood vessels, uterus, urinary tracts to allow substances to move
53
organ definition
collection of tissues working together to perform the same function(s)
54
tissue definition
collection of cells working together to complete the same function(s)
55
organ system definition
collection of organs working together to perform the same specific function(s)
56
epidermis tissue in plant features
flattened cells guard cells no chloroplasts form protective covering over leaves, stems roots sometimes walls impregnated with cutin to form waxy cuticle
57
vascular tissue in plants functions
xylem vessels: carry water and minerals up the plant | phloem sieve tube: transfer sucrose and other assimilated up and down the plant
58
meristematic tissue features
contains stem cells all other plant tissue derive from here then differentiate found at root tips, shoot tips, cambium of vascular bundle cells: thin cell walls with cellulose, no chloroplasts, do not have large vacuole, divide by mitosis and differentiate into other types of cells
59
how cambium cells differentiate into xylem vessels
lignin deposited into cell walls reinforced and makes it waterproof, also kills cells end walls break down forms continuous column with wide lumens to carry water and minerals better lose all organelles, less resistance for water and minerals to travel through
60
how cambium cells differentiate into phloem sieve tubes/companion cells
sieve tubes lose most of organelles, sieve plates develop between them companion cells retain organelles, continue functions to provide ATP for active loading of sugars into sieve tubes
61
plant organs functions
leaf: photosynthesis root: anchorage in soil, absorption of mineral ions and water, storage (of carbohydrates) stem: support, holds leaves up so exposed to more sunlight, transportation of water, minerals, sucrose, assimilates flower: sexual reproduction
62
organs systems in animals for movement
skeleton and skeletal muscles to contract and mod bones nervous system to instruct muscles to contract circulatory system to being glucose + oxygen to respiring tissue, carry away CO2 and waste respiratory system to transfer oxygen from atmosphere to blood digestive system to absorb glucose from food eaten excretory system to remove waste produced of metabolism from body
63
sources of stem cells
embryonic stem cells stem cells in umbilical-cord blood specific adult stem cells found around the adult body induced pluripotent stem cells reprogrammed in laboratories by switching on certain key genes to turn undifferentiate cells
64
uses of stem cells in research and medicine
bone marrow transplants to treat diseases in blood and immune system or restore blood system after treatment drug research (can test on human tissue rather than animal tissue so more accurate and humane) developmental biology, improves current medics technology with better understanding of cell types regenerative medicine (implanting cells to grow into organs in the patient so no need for immunosuppressants if own cells) repair/replacement of damaged/lost tissues
65
roel of embryonic stem cells in development of embryo
undifferentiated can differentiate into any cell type renewing source of cells
66
why embryonic stem cells seen as unethical
embryo discarded/killed embryo cannot give consent debate about when life begins
67
why foetal stem cells seen as unethical
obtained from miscarried/aborted foetuses
68
why umbilical cord stem cells more ethical
umbilical cord detached from infant at birth anyway
69
why bone marrow harvesting seen as unethical
harvesting bone marrow painful / risky | donor babies conceived specifically to provide bone marrow transplant for sibling
70
applications of adult cell cloning
recreate and save endangered species produce spare tissues/organs produce elite/best animals

A-Level Biology (24 decks)

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