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biology > cell division, cell diversity and cellular organisation > Flashcards

cell division, cell diversity and cellular organisation Flashcards

1
Q

what is the cell cycle made up of (brief)

A

preparation for cell division (INTERPHASE)
cell division (MITOSIS AND MEIOSIS)

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2
Q

parts of the cell cycle (in order)

A

Gap 1
S
Gap 2
Mitosis/Meiosis
Cytokinesis

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3
Q

what are the parts of interphase?

A

gap 1
G1/S checkpoint
S phase
gap 2
G2/S checkpoint

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4
Q

what is interphase?

A

preparation for cell division

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5
Q

describe what takes place during Gap 1 of cell cycle

A

GROWTH
cell increases in volume
organelle replication
protein synthesis (produce growth factors and enzymes which are sued in DNA replication in S phase)

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6
Q

what does G1/S checkpoint check for?

A

checks for DNA damage
checks cell is large enough
checks cell has duplicated organelles

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7
Q

a checkpoint during G1 detects DNA damage. what could be the consequences of this?

A

DNA may be repaired, in which case cell continues to S phase
if it cannot be repaired, it enters resting phase G0 or is destroyed

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8
Q

describe what takes place during S phase of cell cycle

A

(synthesis) DNA REPLICATES
ensures twice the original DNA content (each daughter cell receives half)

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9
Q

describe what takes place during gap 2 of cell cycle

A

GROWTH/PREPARATION FOR CELL DIVISION
energy stores increase
cell increases in volume
synthesising key proteins for cell division

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10
Q

what does G2/S checkpoint check for

A

checks for correct DNA replication

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11
Q

stages of mitosis

A

prophase
metaphase
anaphase
telophase

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12
Q

what does M checkpoint check for?

A

(metaphase checkpoint)
spindle assembly checkpoint
checks that spindle fibres are correctly attached to chromosomes

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13
Q

what happens during cytokinesis (brief)

A

cell divides in 2
cytoplasm divides

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14
Q

why are checkpoints so important?

A

control cell cycle.
ensure DNA not damaged so that daughter cells produced are genetically identical to parent cell
prevent uncontrolled cell division which could lead to tumours
DNA in daughter cells contain no errors

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15
Q

when is a cell in the G0 phase?

A
  1. cell may leave cell cycle and enter G0 if it fails one of the checkpoints -> repaired and re-enters cell cycle OR destroyed by apoptosis
  2. cell may leave cell cycle if it is going to become specialised e.g. stem cell differentiates into RBC/ neurone
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16
Q

is interphase a resting phase?
why?

A

NO IT IS NOT A RESTING PHASE
in G, S, G2: significant metabolic activity is taking place
e.g. protein synthesis, DNA replication, aerobic respiration

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17
Q

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

A

cells are resting if they are not actively dividing
BUT
specialised cells e.g. neurones, liver cells carry out significant metabolic activity

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18
Q

whats the significance of mitosis in life cycles?

A

growth, development and tissue repair
clonal expansion of lymphocytes
production of new stem cells
development of body plan (balance between mitosis and apoptosis)
asexual reproduction (one parent cell divides to from 2 genetically identical daughter cells)

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19
Q

what takes place during prophase

A

chromatin condenses (chromsones 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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20
Q

what takes place during metaphase

A

spindle fibres attach to centromeres of each pair of sister chromatids
once attached, chromosomes line up along equator/metaphase plate
leads to metaphase checkpoint, which checks spindle assembly

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21
Q

what takes place during anaphase

A

spindle fibres shorten and pull sister chromatids apart and separate them to opposite poles (REQUIRES ATP)
centromere has divided

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22
Q

what takes place during telophase

A

full set of chromosomes at each pole of the cell
nuclear membrane forms around each set of chromosomes and a nucleolus reappears
chromosomes uncoil, reforming chromatin

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23
Q

is cytokinesis a stage of mitosis?

A

NO
it is distinct and separate

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24
Q

describe cytokinesis in an animal cell

A

cleavage furrow forms down centre of the cell
actin microfilaments contract (ATP required) and separate the 2 cells by pinching the plasma membrane together -> 2x genetically identical daughter cells

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25
Q

describe cytokinesis in a plant cell

A

vesicles containing cellulose are deposited at the cell plate
cellulose molecules hydrogen bond together, forming microfibrils then macrofibrils
cel splits into 2x genetically identical daughter cells

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26
Q

role of cell membrane in cytokinesis

A

cell membrane pulls inwards (cleaves) to separate cytoplasm into 2

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27
Q

plants lack centrioles. what does this indicate about the role of centrioles in mitosis?

A

spindle fibres still form in plant cells BUT they are not produced by centrioles
therefore they are not essential in all cells

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28
Q

homologous pair of chromosomes characteristics

A

a pair of matching chromosomes
1 maternal and 1 paternal
similar size
genes are located in similar positions (loci)

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29
Q

number of chromosomes/chromatids in human cell prior to and after S phase and then after mitosis/cytokinesis

A

46 chromosomes/ 46 chromatids prior to S phase
46 chromosomes/ 92 chromatids after S phase
each daughter cell contains 46 chromosomes/ 46 chromatids

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30
Q

what is a stem cell?

A

an unspecialised cell
has the potential to become a specialised cell (leave the cell cycle)
self-renewing through mitosis

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31
Q

where can scientists obtain stem cells?

A

bone marrow
embryos (donated from IVF)
tissues (e.g. skin, brain, blood, muscle, guts)

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32
Q

neural stem cells from the brain can differentiate into which types of cell?

A

the 3 types of cell which exist in the brain

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33
Q

how can stem cells be used in the treatment of burns?

A

sample of skin from unburned area taken
stem cells undergo mitosis and a layer of skin cells is grown/cultured
layer is transplanted onto patient
(can only form outer layer of skin: no sweat glands e.t.c.)

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34
Q

how can stem cells be cultured in a laboratory? i.e. which substances are required in the medium?

A

glucose
oxygen
amino acids
growth hormones

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35
Q

vague roles of stem cells in our bodies?

A

repairing wounds
replacing old blood cells

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36
Q

4 types of stem cells

A

totipotent
pluripotent
multipotent
induced pluripotent (iPSCs)

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37
Q

examples of embryonic stem cells

A

totipotent
pluripotent

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38
Q

totipotent stem cells:
extracted from?
can differentiate into?/potency?
ability?

A

extracted from first 1-32 cells of an embryo
can differentiate into ALL cell types INCLUDING extra-embryonic cells e.g. placenta and umbilical cord
therefore has ability to form whole living organisms

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39
Q

pluripotent stem cells:
extracted from?
can differentiate into?

A

extracted from first 64-256 cells of embryo
can differentiate into ALL cell types EXCEPT extra-embryonic cells e.g. placenta and umbilical cord

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40
Q

multipotent stem cells:
what kind of stem cell?
extracted from?
can differentiate into?

A

somatic/adult stem cells
extracted from bone marrow (HAEMATOPOETIC stem cells)
can differentiate into many cell types, including lymphocytes, phagocytes, erythrocytes

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41
Q

induced pluripotent stem cells:
what are they?
potential in what?

A

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

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42
Q

function of bone marrow stem cells

A

can differentiate into different types of blood cells e.g. neutrophils and RBCs, which are short-lived cells so must be replaced

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43
Q

what are meristems?

A

tissues found in plants which contain stem cells
all other cells in plant are derived from meristems by cell differentiation

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44
Q

meristematic tissue is found in plant vascular bundle. what is the purpose of this tissue?

A

found between xylem and phloem (in cambium)
can differentiate into cells that form xylem (elongated, lined with lignin) or those that form phloem (sieve tubes or companion cells)

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45
Q

3 potential uses of stem cells in medicine

A

repair of damaged tissues e.g treat burns, repair heart tissue
treat neurological conditions e.g. Alzheimers or Parkinson’s by replacing damaged nerve tissue with transplanted neurones generated from donor & patient derived iPSCs
research into developmental biology. since they can all divide and differentiate into almost any cell type, stem cells can be used to research into the development of multicellular organisms and look at potential cures for problems and how to increase longevity.

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46
Q

7 examples of specialised cells

A

erythrocytes
neutrophils
squamous and ciliated epithelial cells
palisade cells
root hair cells
sperm cells
guard cells

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47
Q

features of erythrocytes that better adapt them for their function

A

biconcave shape
thin walls
flexible shape
presence of haemoglobin
no nucleus

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48
Q

erythrocytes function?

A

carry oxygen from the lungs to the rest of the body
transportation of gases and nutrients through body

49
Q

how does biconcave shape of erythrocytes better adapt them for their function?

A

higher surface area than a flat surface, so an increased ability to absorb oxygen
increased surface area to volume ratio, which allows diffusion to happen quickly and efficiently

50
Q

how do thin walls of erythrocytes better adapt them for their function?

A

allows oxygen to diffuse through quickly due to decreased diffusion distance
flexible so can squeeze through narrow capillaries

51
Q

how does presence of haemoglobin in erythrocytes better adapt them for their function?

A

oxygen combines reversibly with haemoglobin to for oxyhaemoglobin, so increases carrying capacity of RBC

52
Q

how does lack of nucleus in erythrocytes better adapt them for their function?

A

more room for haemoglobin in the cell

53
Q

what type of stem cell differentiates to form an erythrocyte?
where are these stem cells found?

A

hematopoietic stem cells (HSCs)
found in bone marrow

54
Q

what are neutrophils an example of

A

a phagocyte (white blood cell)

55
Q

why do neutrophils have a lobed nucleus?

A

lobular arrangement makes the nucleus easier to deform and hence help the neutrophils pass through small gaps in the endothelium and extracellular metric more easily to get to the site of infection

56
Q

why are neutrophils full of lysosomes?

A

they must digest more material than most other types of cells when fighting bacteria, viruses and other pathogens

57
Q

how does a neutrophil digest an engulfed pathogen

A

pathogen= within phagocytic vacuole
neutrophil secretes digestive enzymes into the vacuole (enzymes are released from lysosomes which fuse with the vacuole)
these digestive enzymes destroy the pathogen

58
Q

how would you distinguish a lymphocyte form a neutrophil using a microscopic image?

A

neutrophil has multi lobed nucleus
lymphocyte has large round nucleus

59
Q

structure of cilia?

A

protrusions from the cell, surrounded by the cell surface membrane
9+2 microtubule arrangement
formed from centrioles

60
Q

purpose of cilia in airways?

A

propel a liquid layer of mucus that covers the airways
move microbes/debris up and out of thew airways by wafting the mucus it is stuck to
avoids infection

61
Q

how is mucus produced?

A

major macromolecular components of mucus, the mucin glycoproteins, are secreted by surface epithelial goblet cells
exocytosis of secreted mucins= final step in intracellular processing
released from goblet cells into airway lumen to interact with water and ions to form mucus

62
Q

how are squamous epithelial cells adapted for their function

A

consists of a single layer of flattened cells on a basement membrane
forms a thin cross-section with decreases distance that substances have to move to pass through (decreased diffusion pathway)
permeable for easy diffusion of gases

63
Q

structure of flagellum

A

9+2 microtubule arrangement
composed of 20 protein components
divided into 3 substructures: filament (in helix), hook and basal body

64
Q

parts of a sperm cell?

A

head (acrosome and nucleus), neck, middle piece (mitochondrion), plasma membrane, tail(flagellum)

65
Q

role of mitochondria in a sperm cell

A

site of aerobic respiration
supply energy as ATP to the sperm cell
necessary to provide tail (undulipodium) with the energy supply that is needed to allow the sperm cell to swim towards the egg

66
Q

how many chromosomes are there in the nucleus of a sperm cell?
why is there variation in the nuclei of different sperm cells?

A

23 chromosomes (gamete)
meiosis produces haploid nuclei, genetically different from each other and parent cell
new combinations of alleles in sperm cells

67
Q

why are acrosomes (full of digestive enzymes) important for sperm cells in fertilisation

A

enzymes break down outer membrane/ protective layer of ovum, allowing sperm to enter and its haploid nucleus fuse w/ haploid nucleus of ovum

68
Q

purpose of keratin in sperm cell flagella

A

provides elasticity and structural integrity to cell

69
Q

why and how do palisade mesophyll cells move chloroplasts around ?

A

migrate in response to different light intensities ( escape from strong light to avoid photodamage, gather in illuminated sea under weak light to maximise light absorption and photosynthesis rates)
move along cytoskeleton threads (chloroplast actin filaments) and motor proteins

70
Q

why do root hair cells have many mitochondria and an extensive RER?

A

mitochondria: site of aerobic respiration. produces energy as ATP for AT of mineral ions
RER: large roles in protein synthesis, so synthesis carrier proteins used in AT

71
Q

how do stomata open? step by step

A

light energy= used to produce ATP
used in AT of K+ form surrounding epidermal cells into guard cells, lowering water potential of guard cells
water enters guard cells by osmosis from neighbouring epidermal cells
guard cells swell, but at the tips of the cells the cellulose cell wall is more flexible and is more rigid where it is thicker
tips bulge, guard cells swell
gaps between cells (stoma) enlarge
CLOSE WHEN GCs LOSE WATER AND SHRINK

72
Q

what are gametes formed by?

A

meiosis

73
Q

number and nature of daughter cells produced in mitosis and meiosis

A

MITOSIS: 2 genetically identical daughter cells
MEOSIS: 4 genetically unique daughter cells

74
Q

what is meiosis known as?

A

reduction division

75
Q

number of divisions in mitosis and meiosis

A

MITOSIS: nucleus divides once
MEIOSIS: nucleus divides twice

76
Q

stages of meiosis I

A

prophase I
crossing over
metaphase I
independent assortment
anaphase I
telophase I

77
Q

prophase I in meiosis

A

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

78
Q

crossing over: what phase and description

A

variation in prophase I
non-sister chromatids within the same homologous pair exchange short sections of DNA

79
Q

use of crossing over?

A

forms new combinations of alleles

80
Q

metaphase I in meiosis

A

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

81
Q

independent assortment: what stage and description

A

variation in metaphase I
orientation of each homologous pair along the equator is random

82
Q

use of independent assortment

A

more possible combinations of alleles in daughter cells

83
Q

anaphase I in meiosis description

A

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

84
Q

telophase I in meiosis description

A

e.g. in a human cell: 23 unpaired chromosomes at each pole
nuclear envelope reforms and nucleolus reappears
chromosomes relax
cytokinesis occurs afterwards

85
Q

number of cells, chromosomes and chromatids before and after meiosis I

A

BEFORE: 1 parent cell, 46 chromosomes (DIPLOID), 92 chromatids
AFTER: 2 daughter cells, 23 chromosomes each (HAPLOID), 46 chromatids eacg

86
Q

what happens prior to meiosis II?

A

short cell cycle without DNA replication

87
Q

stages of meiosis II

A

prophase II
metaphase II
independent assortment
anaphase II
telophase II

88
Q

prophase II meiosis description

A

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

89
Q

metaphase II meiosis description

A

chromosomes line up along equator
spindle fibres attach to centromeres

90
Q

independent assortment stage and description

A

variation in metaphase II
random orientation of chromosomes along the equator which determines which daughter cell each chromatid is separated to

91
Q

use of independent assortment

A

produces new combinations of alleles in daughter cells

92
Q

anaphase II meiosis description

A

spindle fibres shorten
centromeres divide
sister chromatids pulled to opposite poles

93
Q

telophase II meiosis description

A

nuclear membrane forms around each set of chromatids at each pole
nucleolus reappears
chromatids relax to form chromatin
cytokinesis occurs afterwards

94
Q

number of cells, chromosomes and chromatids after meiosis II

A

4 daughter cells
23 chromosomes
23 chromatids

95
Q

how does independent assortment in metaphase I produce variation?

A

each member of a homologous pair could be separated to a different cell

96
Q

how does independent assortment in metaphase II produce variation?

A

each sister chromatid could be separated to a different cell

97
Q

cell definition

A

basic structural and functional unit of living organisms

98
Q

tissue defintion

A

group of differentiated cells with a specific function

99
Q

organ definition

A

collection of tissues working together to perform a particular function

100
Q

organ system defintion

A

made up of a number of organs working together to carry out major function

101
Q

examples of tissues

A

squamous epithelium
ciliated epithelium
cartilage
muscle
xylem
phloem

102
Q

function of squamous epithelium

A

forms linings
allows rapid diffusion

103
Q

ciliated epithelium function

A

co-ordinated movement of cilia allows movement of particles

104
Q

cartilage function

A

connective tissue, gives strength and protection to structures

105
Q

muscle function

A

allows movement of body (bones)

106
Q

xylem function

A

transport of water and minerals up a plant
strength and support

107
Q

phloem function

A

transport of organic nutrients up and down plants

108
Q

differences between meiosis and mitosis

A

mitosis = 2 genetically identical diploid daughter cells
meiosis= 4 genetically unique haploid daughter cells
mitosis=1 division
meiosis= 2 divisions
mitosis= used for growth, repair and asexual reproduction
meiosis= used to produce gametes for sexual reproduction

109
Q

centromere function

A

hold together sister chromatids at centre to form chromosome

110
Q

describe ways in which genetic variation is produced, including role of nuclear division

A

independent assortment of chromosomes in metaphase I and of chromatids in metaphase II. homologous chromosomes have different alleles so therefore this increases the number of allele combinations
crossing over in prophase I means chromatids have different allele combinations. amount of variation depends on distance between chiasmata
mutation= change in nucleotide sequence. DNA checks did not recognise this damage. this leads to a difference in protein synthesised
non-disjunction= homologous chromosomes not separating in metaphase I so one more/less chromosome present.
random fusion of gametes. gametes are not genetically identical so there is a large number of allele combinations

111
Q

what do all blood cells originate from?

A

multipotent stem cells in bone marrow

112
Q

why are root tips warmed in hydrochloric acid when preparing a root tip squash

A

to break the links between cellulose cell wall in plant cells
so stain can penetrate the cells and bind to chromosomes

113
Q

which stain would we use to stain chromosomes in a root tip squash?

A

toluidine blue
or acetic orcein

114
Q

3 types of muscle tissue and where they are found

A

skeletal: bicep/tricep
smooth: digestive tract/blood vessels
cardiac: heart walls

115
Q

4 features of meristematic cells that means they can differentiate easily

A

thin
very little cellulose
no chloroplasts or large vacuole
divide by mitosis

116
Q

true or false: neutrophils undergo mutation during differentiation

A

false

117
Q

true or false: erythrocytes develop large numbers of ribosomes early in their differentiation

A

true

118
Q

true or false: the majority of organelles in red blood cells are broken down by hydrolysis

A

true

biology (28 decks)

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