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Biology A Level > Cell Division, Cell Diversity And Cell Differentation > Flashcards

Cell Division, Cell Diversity And Cell Differentation Flashcards

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1
Q

What could early researchers observing cell division under microscopes easily see?

A

Mitosis

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2
Q

What is mitosis

A

Nuclear division followed by cytokinesis/ cytoplasmic division resulting in two daughter cells

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3
Q

What’s the M phase?

A

Nuclear and cytoplasmic division.

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4
Q

What much of the cell cycle is occupied by the M phase?

A

Only a small part

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5
Q

What is between each M phase?

A

Interphase

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6
Q

What happens in interphase observed under a microscope?

A

Not much

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7
Q

What has allowed change from this belief on interphase?

A

More sophicated techniques

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8
Q

What do scientists now believe happens in interphase?

A

Elaborate preparations being made for cell division

This is carefully ordered and controlled sequence with checkpoints

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9
Q

What are the two main cell cycle checkpoints?

A

G1/ S checkpoint

G2/ M checkpoint

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10
Q

Are there other checkpoint other than these two during interphase?

A

Yes

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11
Q

Give two example of where another one is?

A

Halfway through mitosis

In early G1

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12
Q

What are the functions of checkpoints?

A

To prevent cancer

To detect and repair damage to DNA

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13
Q

How can a checkpoint prevent cancer?

A

By preventing uncontrolled cell division which would lead to a tumour

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14
Q

Give an example of where the cell may repair damage to DNA?

A

Damage caused by UV light

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15
Q

What causes the cell cycle to happen in a certain sequence?

A

Molecular events

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16
Q

What else do these molecular events control?

A

Cell can’t be reversed

DNA only duplicated once during cell cycle

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17
Q

Name the five main phases of the cell cycle?

A 
M phase 
G0 phase 
G1 phase
S phase 
G2 phase
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18
Q

In the M phase, what does A checkpoint chemical trigger?

A

Condensation of chromatin

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19
Q

What checkpoint happens halfway through the M phase?

A

The metaphase checkpoint which ensured that the cell is ready to complete mitosis

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20
Q

What events happen in the M phase within the cell?

A

Cell growth stops
Nuclear division (mitosis) consisting of four stages
Cytokinesis

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21
Q

What are the four stages if nuclear division?

A

Prophase, metaphase, anaphase and telophase

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22
Q

What is cytokinesis?

A

Cytoplasmic division

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23
Q

What is G0 really called?

A

Gap 0 phase

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24
Q

What sort of phase is gap 0?

A

A resting phase

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25
Q

What triggers Gap 0 phase?

A

A checkpoint chemical in early G1

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26
Q

Do all cells have gap 0 phase?

A

No some cell din such as epithelial cells lining the gut

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27
Q

What may cells in gap 0 go under?

A

Apoptosis, differentiation or senescence

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28
Q

What’s apoptosis?

A

Programmed cell death

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29
Q

How long will some cells stay in gap 0?

A

Very long time or indefinitely

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30
Q

What is G1 phase called?

A

Gap 1 phase

Growth phase

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31
Q

What a G1 checkpoint control mechanism does what?

A

Ensures the cell is ready to enter the S phase and begin DNA synthesis

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32
Q

What 5 events happens in gap 1 phase?

A 
Cells grow and increase in size 
Transcription of genes to make RNA occurs 
Organelles duplicate
Biosynthesis 
The p53 gene helps control this phase
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33
Q

Give a example of biosynthesis that happens?

A

Protein synthesis including making enzymes needed for DNA

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34
Q

What is the p53 gene?

A

The rumour suppressor

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35
Q

What is the S phase really called?

A

Synthesis phase

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36
Q

Why is every molecules of DNA replicated during the synthesis phase?

A

Chromosomes are unwound and DNA will diffuse

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37
Q

Is there a specific sequence to the replication of DNA in synthesis phase?

A

Yes

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38
Q

What types of cells are duplicated first in the synthesis stage?

A

Housekeeping genes

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39
Q

What do housekeeping genes do?

A

Active in all types of cells

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40
Q

What types of cells are duplicated last in the synthesis stage of interphase?

A

Genes that are normally inactive in specific types of cells

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41
Q

Once the cell has entered the synthesis phase of interphase it is?

A

Committed to completing the cell cycle

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42
Q

What events happen in synthesis phase of interphase?

A

DNA replicates

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43
Q

What happens when all chromosomes have been duplicated in the synthesis phase?

A

Each one consists of a pair of identical sister chromatids

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44
Q

What speed is synthesis phase and why?

A

Rapid because exposed DNA base pairs are more susceptible to mutagenic agents reduces chances of spontaneous mutations happening

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45
Q

What is the real name of G2?

A

Gap 2 phase

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46
Q

What do special chemicals in gap 2 phase ensure?

A

Cells are ready for mitosis by stimulating proteins that will be involved in making chromosomes condense and in formation of the spindle

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47
Q

What events happen during gap 2 phase?

A

Cells grow

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48
Q

How do cells reproduce?

A

Duplicating their contents and then splitting into two daughter cells

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49
Q

Is there an infinite amount of times cells should undergo cell division?

A

Yes there is normally only a certain number of cycles

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50
Q

What is the number of cycles cells should undergo called?

A

Hayflick constant

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51
Q

What is hayflick constant?

A

About 50

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52
Q

What happens if cell division becomes uncontrolled?

A

A tumour can form which may become malignant or cancerous

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53
Q

What do Porto-oncogenes ?

A

Help regulate cell division by coding for proteins that help regulate cell growth and differentiation.

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54
Q

What happens if these proto-oncogenes mutate?

A

They may become oncogenes and cause cells to fail to undergo apoptosis and keep dividing causing a tumour

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55
Q

Why is P53 important?

A

It triggers two major checkpoints in the regulation of the cell cycle

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56
Q

What is p53 gene also known as?

A

Tumour suppressor gene

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57
Q

Name other regulatory protein?

A

Cyclins

CDK’s

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58
Q

What are cylins?

A

Synthesised response to cell-signalling molecules such as growth factors

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59
Q

Why did the scientist call it cylin?

A

For love of cycling but title is appropriate

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60
Q

What are CDK’s?

A

Cylin-dependent kinases

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61
Q

How does the prokaryotic cell cycle occur?

A

By binary fission

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62
Q

What basically happens in binary fission?

A

Cells grow to its limit of size and then splits into two.

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63
Q

What happens in binary fission before the cell divides?

A

The DNA is replicated

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64
Q

What happens in binary fission after The DNA is replicated?

A

Two new loops of DNA are pulled to opposite ends of the cell and a cell wall forms which begin to separate the bacterial cell.

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65
Q

What does each new cell from binary fission contain?

A

Replicated plasmids and synthesised ribosomes

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66
Q

How do microchrondria and chloroplasts divide?

A

By binary fission

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67
Q

Why do living organisms need to produce genetically identical daughter cells by mitosis?

A

Assexual reproduction
Growth
Tissue repair

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68
Q

What uses asexual reproduction?

A 
Single-celled protoctists such as amoeba and paramecium 
Some plants 
Fungi 
Rarer in animals
Aphids can
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69
Q

Who uses growth via mitosis?

A

All multicellular organisms that are genetically identical to each other and to patent cells from which they arose

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70
Q

Tissue repair?

A

Wounds heal when growth factors secret platelets and macrophages and damaged cells of the blood-vessel walls stimulate proliferation of endothelial and smooth muscle cell to pair damaged blood vessels.

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71
Q

Does mitosis ever stop?

A

No its continuous

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72
Q

What are the four stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

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73
Q

What happens in prophase to the chromosomes replicated in the s phase?

A

Chromosomes replicated during the s phase of interphase and consists of 2 identical sister chromatids shortened and thickened as DNA supercoils.

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74
Q

What does the nuclear envelope do?

A

Break down

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75
Q

What do the centriole in animal cells (usually centromere) do in prophase?

A

Divides and the two new daughter centrioles move to opposite poles of the cell

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76
Q

What does the cytoskeleton do in the prophase?

A

Tumbling threads form a spindle between these centrioles. In plant cells the tublin threads are formed

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77
Q

In metaphase what happens?

A

Pairs of chromatids attach to spindle threads by their centromeres at equator region

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78
Q

What happens in anaphase (centromere)?

A

Centromeres of each pair of chromatids spilt.

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79
Q

What happens in anaphase (motor protein)?

A

Motor proteins walking along tublin threads pull each sister chromatid of a pair in the opposite direction towards the opposite pole.

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80
Q

What happens in anaphase (V shape)?

A

Chromatids (chromosomes) assume V shape

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81
Q

What happens to the chromosomes in telophase?

A

Separated chromosomes teach the poles

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82
Q

What also happens each set of chromosomes?

A

A new nuclear envelope forms

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83
Q

What does the cell now contain in telophase?

A

Two genetically identical nuclei

84
Q

What happens when mitosis is complete?

A

Cell splits in two so that each cell contains a nucleus

85
Q

What happens to the plasma membrane in animal cells in cytokinesis?

A

Folds inwards and nips in the cytoplasm

86
Q

What happens to the plasma membrane in plant cells in cytokinesis?

A

An end plate forms where the equator of the spindle was and new plasma membrane and cellulose cell- wall material are laid down on either side along this end plate

87
Q

What are formed from cytokinesis?

A

2 new daughter cells now formed which are genetically identical to each other and to the parent cell.

88
Q

How does sexual reproduction increase genetic variation?

A

It involves combining of Genetic material from two unrelated individuals of the same species by fertilisation.

89
Q

What does genetic variation within a population increase chances of?

A

Survival when the environment changes as some individuals will have characteristics enabling them to be better adapted to the change.

90
Q

What are body cells in many organisms?

A

Diploid

91
Q

What type of cell must sexual reproduction use?

A

Haploid gametes

92
Q

Why must it be haploid for sexual reproduction?

A

When two gamete nuclei fuse during fertilisation a diploid zygote is produced and the normal chromosomes number is maintained through the generation

93
Q

Where does meiosis occur?

A

In diploid germ cells in gonads to produce haploid gametes

94
Q

What are gonads?

A

Ovaries and testes

95
Q

How many chromosomes in body cell?

A

46

96
Q

How many chromosomes from each parent?

A

23 from mother egg nucleus , 23 from father sperm nucleus

97
Q

What can these chromosomes do?

A

Form matching pairs one maternal and one paternal chromosomes containing same genes at the same places on the chromosomes

98
Q

What are these matching pairs called?

A

Homologous chromosomes

99
Q

What even though they have the same genes have different?

A

Alleles

100
Q

What happens before meiosis?

A

S phase of interphase

101
Q

What happens in S phase of interphase (meiosis)?

A

Each chromosomes are duplicated as its DNA replicated after which each chromosomes consists of two sister chromatids.

102
Q

What happens in meiosis?

A

Chromosomes pair up in their homologous pairs

103
Q

How many divisions in meiosis?

A

2

104
Q

How many phases in each division of meiosis?

A

4

105
Q

What are the names of all the phases in the first and second phase of meiosis?

A

Prophase 1, metaphase 1, anaphase 1, telophase 1

Prophase 2, metaphase 2, anaphase 2, telophase 2

106
Q

What do the cells do between first and second division?

A

A short interphase

107
Q

Where does the second division happen?

A

Place in a plane at right angles to that if meiosis 1.

108
Q

What happens after the second division?

A

Cytokinesis

109
Q

In prophase 1, what does chromatin do?

A

Condense and each chromosome supercoils. In this state it can take yo stains and can be seen with light microscope

110
Q

During prophase 1, what does the nuclear envelope do?

A

The nuclear envelope breaks down and spindle threads of tublin protein form from the centriole in animal cells.

111
Q

Can the chromosomes come together in their homologous pairs in prophase 1?

A

Yes

112
Q

What does each chromosome consist of prophase 1?

A

Two chromatids

113
Q

Where does crossing over occur in prophase 1?

A

Where non-sister chromatids wrap around each other and may swap sections so that alleles are shuffled

114
Q

Metaphase 1: what do the pairs of homologous chromosomes do?

A

Attach along equator of spindle, each attach to spindle thread by its centromere,

115
Q

Metaphase 1: how are homologous pairs arranged?

A

Randomly with members of each pair factions opposite poles of the cell. Arrangement is independent assortment.

116
Q

What does the way they line up in metaphase 1 determine?

A

How they will segregate independently when pulled apart during anaphase

117
Q

What do motor proteins do in anaphase 1?

A

Pull members of each pair of homologous chromosomes apart and drag them along the tublin threads of the spindle

118
Q

What don’t the centromeres do in anaphase 1?

A

Divide and each chromosomes consists of two chromatids.

119
Q

What does the crossed-over area do in anaphase 1?

A

Separate from each other resulting in swapped areas of chromosomes and allele shuffling.

120
Q

What do animal cells do in telophase 1?

A

Have 2 new nuclear envelopes form around each set of chromosomes and the cell divides by cytokinesis. Short interphase where chromosomes uncoil follows.

121
Q

What does each new nucleus contain telophase 1?

A

Each new nucleus contains half the original number of chromosomes but each chromosome consists of 2 chromatids.

122
Q

What happens in telophase 1?

A

Cell goes straight from anaphase 1 to prophase 2

123
Q

Prophase 2 nuclear envelopes do what?

A

If they have reformed they will break died

124
Q

What do the chromosomes do in prophase 2?

A

Chromosomes coil and condense each one consisting of two chromatids. Chromatids of each chromosome no longer identical to crossing over in prophase 1.

125
Q

What do spindles do in prophase 2?

A

Form

126
Q

What do chromosomes do in metaphase 2?

A

Attach by their centromere to the equator of the spindle

127
Q

How are the chromatids arranged and what does determine?

A

Randomly arranged

the way they are arranged will determine how the chromatic separate during anaphase

128
Q

During anaphase 2 what do centromeres do?

A

Divide

129
Q

What do chromatids of each chromosome do in anaphase 2?

A

Get pulled apart by motor proteins that drag then along the tublin threads if the spindle towards the poles. Therefore they are randomly segregated.

130
Q

What does telophase 2 nuclear envelopes do?

A

Form around each of the four haploid nucleus

131
Q

In telophase what happens in animals?

A

Two cells now divide to give four haploid cells.

132
Q

In telophase what happens in plants?

A

Tetrad of four haploid cells is formed.

133
Q

How does meiosis produce genetic variation?

A

Crossing over during prophase 1 shuffles alleles
Independent assortment of chromosomes in anaphase 1 leads to random distribution of maternal and paternal chromosomes of each pair
Independent assortment of chromatids in anaphase 2 leads to further random distribution of genetic material
Haploid gametes are produce which can undergo random fusion with gametes derived from another organism of the same species

134
Q

What is the division of labour within a single-celled organism determined by?

A

Organelles which each have a specific function

135
Q

Single celled organism are small therefore:

A

They have a large surface area to volume ratio so oxygen can diffuse across plasma membrane and waste products can diffuse out via the same membrane.

136
Q

Multicellular organisms are bigger therefore:

A

Smaller surface area to volume ratio which means that most cells don’t have contact with external environment so need specialised cells to carry out particular functions.

137
Q

How do multicellular organisms start out life?

A

As a single undifferentiated cell (zygote)

138
Q

How does a zygote happen?

A

Ovum is fertilised by a spermatozoon and two haploid nuclei fuse to give a cell with a diploid nucleus

139
Q

Is a zygote specialised?

A

No

140
Q

What genes are therefore turned on in a zygote?

A

All of the ones in its genome

141
Q

What type of cell is a zygote and how can it divide?

A

Divide by mitosis

A stem cell

142
Q

What happens after several motor of divisions?

A

An embryo forms containing many undifferentiated embryonic stem cells

143
Q

When do these embryonic cells differentiate?

A

As certain genes are switched off and other genes may be expressed more

144
Q

How do the differentiated cells now differ?

A

Proportions of different organelles differs from those of other cells
Shape of cell change
Some of contents if the cell change

145
Q

What causes each cell type to specialised for a particular function?

A

Differentiation

146
Q

What do erythrocytes do?

A

Carry oxygen from lungs to respiring cells

147
Q

What do neutrophils do?

A

Ingest invading pathogens

148
Q

What do erythrocytes and neutrophils derive from?

A

Stem cells in bone marrow

149
Q

How are erythrocytes adapted to carry out their function

A

Very small
Flexible
Most of their organelles lost at differentiation
Biconcave

150
Q

What does being very small mean for erythrocytes adaptions?

A

They are about 7.5 um in diameter
Large surface area to volume ratio
Oxygen can easily diffuse across cell

151
Q

What does being flexible mean for erythrocytes adaptions?

A

Well developed cytoskeleton allows erythrocytes to change shape so can twist and turn as travel through very narrow capillaries

152
Q

What does losing most of their organelles mean for erythrocytes adaptions?

A

No nucleus, mitochondria, rough endoplasmic reticulum and very little cytoplasm
Provides more space for haemoglobin

153
Q

When is haemoglobin synthesised?

A

Immature erythrocytes while they still have nucleus, ribosomes and rough endoplasmic reticulum

154
Q

What does being concave mean for erythrocytes adaptions?

A

Increase surface area to volume ratio

155
Q

How are spermatozoa specialised?

A

Many mitchrondria
small but long and thin
When reaches ovum releases enzymes from acrosome.
Head of sperm contains haploid male gamete nucleus and very little cytoplasm

156
Q

What does many mitochondria mean for spermatozoa adaptations?

A

Carry out aerobic respiration

ATP provides energy for unduplipodium to move and propel cell towards the ovum

157
Q

What does small but long and thin mean for spermatozoa adaptations?

A

Can move easily

158
Q

What does enzymes mean for spermatozoa adaptations?

A

Enzyme digests outer protective covering of ovum allowing sperm head to enter the ovum

159
Q

Where is epithelial found?

A

On outside of body and on inside making up walls of alveoli and capillaries and lining of intestine

160
Q

Shape of epithelial cells

A

Flattened in shape

161
Q

Do many cells in epithelium have cilia?

A

Yes

162
Q

How are palisade cells adapted?

A

Long and cylindrical
Large vacuole
Many chloroplasts
Contain cytoskeleton threads and motor proteins

163
Q

What does long and cylindrical mean for palisade cells?

A

They pack together quite closely with little space between them for air to circulate carbon dioxide in these air spaces diffuses into the cells

164
Q

What does large vacuole mean for palisade cells?

A

Chloroplasts are positioned near to the periphery of the cell reducing the diffusion distance for carbon dioxide

165
Q

What does contain cytoskeleton threads and motor proteins mean for palisade cells?

A

Move chloroplasts nearer to the upper surface if the leaf when sunlight is low but further down when it is high

166
Q

What are guard cells?

A

A pair of specialised cells
Within lower epidermis
Contain chloroplast can’t photosynthesis as don’t have enzymes needed

167
Q

What is used to produce ATP in guard cells?

A

Light energy

168
Q

What lowers water potential in guard cells?

A

ATP actively transports potassium ions from surrounding epidermal cells

169
Q

What then happens due to the lowered water potential?

A

Water enters from neighbouring epidermal cells by osmosis

170
Q

Once water has entered ?

A

Guard cells swell but at tips cellulose wall is more flexible and is more rigid. Where thicker. Tips bulge and half between stoma enlarges

171
Q

Once the guard cells swell?

A

Stomata open air can enter spaces within layer of cells between palisade cells

172
Q

Once stomata open?

A

Gaseous exchanges can occur and carbon dioxide will diffuse in palisade cells used for photosynthesis maintaining steep concentration gradient.

173
Q

What happens to the oxygen produced during photosynthesis?

A

Can diffuse out of palisade cells into air species and out through open stomata

174
Q

What are root hair cells?

A

Epidermal son the outer layer of young plant root.

175
Q

What adaptations does a root hair cell have?

A

Hair-like projections
Mineral ions active transported into root hair cell
Special carrier proteins
Cell produces ATP

176
Q

What does hair-like projections mean for adaptations of root hair cells?

A

Greatly increase surface area for absorption of water and mineral ions such as nitrates from the soil into which it projects

177
Q

What does mineral ions are actively transported into root hair cell mean for adaptations of root hair cells?

A

Lowers water potential within them causing water to follow by osmosis down the water-potential gradient

178
Q

What does special carrier proteins mean for adaptations of root hair cells?

A

It’s inside the plasma membrane in order to actively transport the mineral ions in

179
Q

What does produce ATP mean for adaptations of root hair cells?

A

Needed for active transport

180
Q

Define tissue

A

A group of similar cells working together to perform a certain function

181
Q

What are the four main tissue types?

A

Epithelial/lining tissue
Connective tissue
Muscle tissue
Nervous tissue

182
Q

What does connective tissue do?

A

Holds structures together and provides support e.g. Blood, bone, cartilage

183
Q

Muscle tissue is made of?

A

Cells specialised to contract and cause movements

184
Q

Nervous tissue made of?

A

Cell specialised to conduct electrical impulses

185
Q

What’s epithelial tissue?

A

Covers and lines free surfaces in the body such as the skin, cavities of the digestive system, blood vessels, heart chambers and walks of organs

186
Q

Characteristics of epithelial tissue are:

A 
Made up almost entirely of cell 
Cells very close together 
No blood vessels 
smooth surfaces or have projections cilia/microvilli
Short cell cycles 
Specialised to carry out its function
187
Q

What does the cells being close together mean?

A

Form continuous sheet adjacent cells bound together by lateral contacts such as tight junctions and dsmosomes

188
Q

What does no blood vessels mean?

A

Cells receive nutrients by diffusion from tissue fluid in underlying connective tissue.

189
Q

What do short cell cycles mean?

A

Only lasts a day so can repair quickly

190
Q

How are epithelial specialised for their function?

A

Ciliated have cilia that beat particles away

Squamous epithelial are very thin to allow efficient diffusion of gases

191
Q

Sperm cells special adaptations?

A

Flagellum so can swim to egg
Lots of mitchrondria to provide ATP to swim
Acrosome contains digestive enzymes to enable sperm to penetrate surface of egg

192
Q

What a tissue?

A

Group of tissue specialised to work together to carry out a particular function. Tissue contains more then one cell type

193
Q

Name four types of tissue?

A

Squamous epithelium
Ciliated epithelum
Muscle tissue
Cartilage

194
Q

Squamous epithelium?

A

single layer of flat cells lining a surface. Found in many places including alveoli in lungs.

195
Q

Ciliated epithelum?

A

Layer of cells covered by cilia
Found in surface where things need to be moved
(Trachea cilia waft mucus along)

196
Q

Muscle tissue made of?

A

Made up of bundled of elongated cells (muscle fibres)

197
Q

Types of muscle tissue and are they all the same?

A

Smooth
Cardiac
Skeletal
Slightly different in structure

198
Q

Cartilage is?

A

Type of connective tissue in joints
Shaped and supports ears, nose and windpipe
Formed when cells (chrondroblasts) secrete extra cellular matrix become trapped inside

199
Q

Xylem tissue?

A

Transports water around plant
Supports plant
Contains hollow xylem vessel cells
Living parenchyma cells

200
Q

Phloem tissue?

A

Transports sugars around plant
Arranged in tubes made of sieve and companion cells and some ordinary plant cells
Sieve cells has sieve plates so sap can move easily though

201
Q

Organ?

A

Group of tissue work together to perform particular function.

202
Q

Name examples of organs?

A

Lungs contain squamous epithelial tissue, ciliated epithelial tissue, elastic connective tissue and vascular tissue
Leaves contain palisade tissue photosynthesis, epidermal tissue, xylem and pholem in veins

203
Q

What do organs work together to form?

A

Organ systems each with particular function

204
Q

Name two examples of organ system?

A

Respiratory system

Circularity system

205
Q

Respiratory system?

A

Function breathing

Made of lungs, nose, mouth, diaphragm

206
Q

Circularity system?

A

Blood supply

Heart, artery, veins and capillaries

Biology A Level (26 decks)

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