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A Level Biology > 2.6 Cell Division, Cell Diversity And Cellular Organisation > Flashcards

2.6 Cell Division, Cell Diversity And Cellular Organisation Flashcards

1
Q

Three phases of cell cycle

A

Interphase, nuclear division (mitosis), cell division (cytokinesis)

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2
Q

Cyclis

A

Triggers the movement from one phase to another in the cell cycle by chemical signals

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3
Q

What happens during interphase

A

the cell increases in mass and size and carries out its normal cellular functions (eg. synthesising proteins and replicating its DNA ready for mitosis)

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4
Q

3 phases in interphase

A

G1 phase
S phase
G2 phase

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5
Q

What is the cell cycle

A

Process al body cells use to grow and divide

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6
Q

What are the functions of the cell cycle

A

Growth repair, replace and asexual reproduction

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7
Q

End products of the cell cycle

A

2 identical daughter cells

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8
Q

G1 phase

A

Growth phase of cells
Organelles replicate
Synthesis of proteins

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9
Q

S phase

A

Replication of each chromosome resulting in each chromosome consisting of two identical sister chromatids

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10
Q

G2 phase

A

The cells continues to grow and the new DNA that has been synthesised is checked

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11
Q

Mitosis phase (M phase)

A

Where cell divides (mitosis and cytokinesis)

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12
Q

4 stages of mitosis

A

Prophase, metaphase, anaphase and telephase

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13
Q

Cytokinesis

A

Once the nucleus has divided into two genetically identical nuclei, the whole cell divides and one nucleus moves into each cell to create two genetically identical daughter cells

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14
Q

Cytokinesis in animal cells

A

cytokinesis involves constriction of the cytoplasm between the two nuclei

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15
Q

Cytokinesis in plant cells

A

A new cell wall is formed

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16
Q

Checkpoints throughout the cell cycle

A

where the genetic information contained within the replicated DNA is checked for any possible errors
During, G1, S, G2, metaphase

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17
Q

How to remember stages of mitosis

A

PMAT

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18
Q

G1 checkpoint

A

chromosomes are checked for damage. If damage is detected then the cell does not advance into the S phase until repairs have been made

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19
Q

S phase checkpoint

A

chromosomes are checked to ensure they have been replicated. If all the chromosomes haven’t been successfully replicated then the cell cycle stops

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20
Q

G2 checkpoint

A

an additional check for DNA damage occurs after the DNA has been replicated. The cell cycle will be delayed until any necessary repairs are made

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21
Q

Metaphase checkpoint

A

the final check determines whether the chromosomes are correctly attached to the spindle fibres prior to anaphase

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22
Q

Prophase

A

Chromosomes condense and thicken
Consists of sister chromatids joined at the centromere
Two centrioles migrate to opposite poles of the cell
Spindle fibres attach to specific areas on the centromeres and start to move chromosomes to the equator of the cell
Nuclear envelope disappears

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23
Q

Metaphase

A

Individual sister chromatids are moved by the spindle fibres to align at the equator
Sister chromatids are attached to the spindle by the centromere

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24
Q

Anaphase

A

Centromeres holding the pairs of chromatids in each chromosome divide
Sister chromatids separate
Spindle contracts
Each chromatids is pulled by their centromere to opposite poles of the cell

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25
Q

Telophase

A

Chromatids reached pomposity poles. They uncoil now chromosomes
Spindle fibres disappear
Nuclear envelope reforms and enclose around the chromosomes at each pole

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26
Q

Where does growth in plants occur

A

Meristems

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27
Q

What can be used to study mitosis

A

The root tip meristem

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28
Q

Method to see stages of mitosis in root tip meristem

A

Remove tip of roots and place in a suitable stain the stained root tip is gently squashed on a glass slide using a blunt instrument
Cells undergoing mitosis can be seen and drawn

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29
Q

Mitosis

A

The process of nuclear division by which two genetically identical daughter nuclei are produced that are also genetically identical to the parent nucleus

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30
Q

Products of mitosis

A

Two genetically identical daughter cells

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31
Q

How to mitosis lead to growth on multicellular organisms

A

Genetically in detail daughter cells enable unicellular zygotes to grow into multicellular organisms

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32
Q

How does mitosis lead to replacement of cells and repair of tissues

A

Damaged tissues can be repaired by mitosis followed by cell division
As cells are constantly dying they need to be continually replaced by genetically identical cells

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33
Q

Asexual reproduction

A

the production of new individuals of a species by a single parent organism – the offspring are genetically identical to the parent

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34
Q

How does mitosis lead to Asexual reproduction

A

For unicellular organisms such as Amoeba, cell division results in the reproduction of a genetically identical offspring
For multicellular organisms, new individuals grow from the parent organism (by cell division) and then detach (‘bud off’) from the parent in different ways

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35
Q

Meiosis

A

The process by which gametes are made in reproductive organs. It involves the reduction division of a diploid gem line cell into four genetically distinct haploid nuclei

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36
Q

End products of meiosis

A

4 haploid daughter cells

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37
Q

Stages of meiosis

A

Interphase
Pmat 1
Interphase
Pmat 2

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38
Q

Stages of meiosis

A

Interphase
Pmat 1
Interphase
Pmat 2

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39
Q

Homologous chromosomes

A

Pairs of chromosomes that contain the same genetic information

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40
Q

Sister chromatids

A

Each chromosome is made up of two copies- each one in a chromatid
Two chromatids called sire chromatids are joined together at the centromere

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41
Q

Interphase

A

Stage of cell cycle where cell prepares for division

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42
Q

Prophase 1

A

Crossing over occurs here
Chromosomes condense, nuclear membrane dissolves, homologous chromosomes form bivalents, nuclear envelope dissolves

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43
Q

Metaphase 1

A

Homologous pairs chromosomes assemble along the membrane plate, spindle fibres from opposing centrosomes connect to bivalents and align them along the middle of the cell

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44
Q

Anaphase 1

A

Independent assortment occurs here
Spindle fibres contract and split the bivalent, homologous chromosomes moved to opposite poles of the cell

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45
Q

Telophase 1

A

Chromosomes decondense, nuclear membrane may reform, cell divides (cytokinesis) to form two haploid daughter cells

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46
Q

Prophase 11

A

Chromosomes condense, nuclear membrane dissolves, spindle fibres reform, centromeres move to opposite poles

47
Q

Metaphase 11

A

Spindle fibres form opposing centromeres attach to chromosomes and align them along the cell equator

48
Q

Anaphase 11

A

Centromere divides, pairs of sister chromatids are separated, each new daughter cell inherits one chromatid from each chromosome, Spindle fibres contract

49
Q

Telophase 11

A

Chromatids uncoil and decondense, spindle fibres break down, nuclear envelopes reform, the cell undergoes cytokinesis

50
Q

Cytokinesis

A

Cytoplasm and surface membrane divide, creating four independent haploid cells

51
Q

Crossing over

A

Process by which non-sister chromatids exchange alleles

52
Q

Crossing over process

A
  1. Homologous pairs of chromosomes associate / form a bivalent
  2. Chiasma(ta) form (the point of breakage)
  3. (Equal) lengths of (non-sister) chromatids / alleles are exchanged
  4. This produces new combinations of alleles
53
Q

Independent assortment process

A

1) Each homologous pair of chromosomes in your cells is made up of one chromosome from your mum (maternal) and one chromosome from your dad (paternal).
2) When the homologous pairs line up in metaphase I and are separated in anaphase I, it’s completely random which chromosome from each pair ends up in which daughter cell.
3) So the four daughter cells produced by meiosis have completely different combinations of those maternal and paternal chromosomes.
4) This is called independent assortment (separation) of the chromosomes.
5) This ‘shuffling’ of chromosomes leads to genetic variation in any potential offspring.

54
Q

Independent assortment

A

the production of different combinations of alleles in daughter cells due to the random alignment of homologous pairs along the equator of the spindle during metaphase I

55
Q

Erythrocytes function

A

transport oxygen around the body and carbon dioxide to the lungs

56
Q

Erythrocytes adaptations

A

They are biconcave in shape which increases the surface area over which oxygen can be absorbed
The cytoplasm contains high amounts of the pigment haemoglobin which can readily bind to oxygen
No nucleus is present which makes more space inside the cell for haemoglobin molecules for maximum oxygen-carrying capacity
Elastic membrane allows the cell to be flexible and change shape as it squeezes through narrow capillaries

57
Q

Neutrophils function

A

destroy pathogens by phagocytosis and the secretion of enzymes

58
Q

Adaptations of neutrophils

A

Neutrophils have a very flexible shape that allows them to squeeze through cell junctions in the capillary wall
Their flexibility also enables them to form pseudopodia (cytoplasmic projections) that engulf microorganisms
There is a large number of lysosomes present in the cell. These digestive enzymes help to digest and destroy invading cells
A flexible nuclear membrane further helps the cell to penetrate cell junctions. It is thought that this flexibility is what causes the characteristic lobed nucleus

59
Q

Sperm cells function

A

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

60
Q

Adaptation of sperm cells

A

The head contains a nucleus that contains half the normal number of chromosomes (haploid, no chromosome pairs)
The acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg’s nucleus
The mid-piece is packed with mitochondria to release energy (via respiration) for the tail movement
The tail rotates, propelling the sperm cell forwards and allowing it to move towards the egg

61
Q

Root hair cells function

A

absorption of water and mineral ions from soil

62
Q

Root hair cells adaptations

A

Root hair to increase surface area (SA) so the rate of water uptake by osmosis is greater (can absorb more water and ions than if SA were lower)
Thinner walls than other plant cells so that water can move through easily (due to shorter diffusion distance)
Permanent vacuole contains cell sap which is more concentrated than soil water, maintaining a water potential gradient
Mitochondria for active transport of mineral ions

63
Q

Ciliated epithelium function

A

moving substances across the surface of a tissue

64
Q

Adaptations of Ciliated epithelium

A

Have cilia (hair-like structures), which beat in a coordinated way to shift material along the surface of the epithelium tissue
Goblet cells secrete mucus which helps to trap dust, dirt and microorganisms - preventing them from entering vital organs where they may cause infection

65
Q

Function of squamous epithelium

A

provide a surface covering or outer layer. Found on a variety of organs and structures e.g. blood vessels and alveoli

66
Q

Adaptations of squamous epithelium

A

Squamous epithelium consists of a single layer of flattened cells on a basement membrane
The layer of cells forms a thin cross-section which reduces the distance that substances have to move to pass through - it shortens the diffusion pathway
It is permeable, allowing for the easy diffusion of gases

67
Q

Function of palisade cells

A

carry out photosynthesis to produce glucose and oxygen

68
Q

Adaptations of palisade cells

A

A large number of chloroplasts (the site of photosynthesis) are present in the cytoplasm to maximise the absorption of light for photosynthesis
The tall and thin shape of the cells allows light to penetrate deeper before encountering another cell wall (cell walls absorb/reflect light) and for many cells to be densely packed together

69
Q

Guard cells function

A

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

70
Q

Adaptation of guard cells

A

Inner cell walls are thicker (those facing the air outside the leaf) while the outer cell walls are thinner (those facing adjacent epidermal cells). The difference in the thickness of the cell walls allows the cell to bend when turgid
The cytoplasm has a high density of chloroplasts and mitochondria. Scientists think that these organelles may play a role in the opening of the stomata

71
Q

Tissue

A

A group of cells that work together

72
Q

Organ systems

A

Organs working together

73
Q

Xylem vessel cells function

A

transport tissue for water and dissolved ions

74
Q

Xylem vessel cells adaptations

A

No top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration
Cells are essentially dead, without organelles or cytoplasm, to allow free movement of water
Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant

75
Q

Phloem vessel cells function

A

transport of dissolved sugars and amino acids

76
Q

Phloem vessel cells function

A

transport of dissolved sugars and amino acids

77
Q

Adaptations of phloem vessel cells

A

Made of living cells (as opposed to xylem vessels which are made of dead cells) which are supported by companion cells
Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes that allow sugars and amino acids to flow easily through (by translocation)
Cells also have very few subcellular structures to aid the flow of materials

78
Q

Function of muscle cells

A

Contraction for movement

79
Q

Adaptations of muscle cells

A

There are three different types of muscle in animals: skeletal, smooth and cardiac (heart)
All muscle cells have layers of protein filaments in them, these layers can slide over each other causing muscle contraction
Muscle cells have a high density of mitochondria to provide sufficient energy (via respiration) for muscle contraction
Skeletal muscle cells fuse together during development to form multinucleated cells that contract in unison

80
Q

Ciliated epithelium function

A

moving substances across the surface of a tissue

81
Q

Adaptation of Ciliated epithelium

A

Have cilia (hair-like structures), which beat in a coordinated way to shift material along the surface of the epithelium tissue
Goblet cells secrete mucus which helps to trap dust, dirt and microorganisms - preventing them from entering vital organs where they may cause infection

82
Q

Squamous epithelium function

A

provide a surface covering or outer layer. Found on a variety of organs and structures e.g. blood vessels and alveoli

83
Q

Squamous epithelium adaptation

A

Squamous epithelium consists of a single layer of flattened cells on a basement membrane
The layer of cells forms a thin cross-section which reduces the distance that substances have to move to pass through - it shortens the diffusion pathway
It is permeable, allowing for the easy diffusion of gases

84
Q

Cartilage function

A

To provide support

85
Q

Cartilage adaptations

A

Cartilage is a strong and flexible tissue found in various places around the body
One place is in rings along the trachea, called Tracheal rings
These rings help to support the trachea and ensure it stays open while allowing it to move and flex while we breathe

86
Q

Stem cell

A

a cell that can divide (by mitosis) an unlimited number of times
A cell that has not yet become a specialised cell

87
Q

What can a stem cell do

A

Can divide many times by mitosis
Each new cell has the potential to remain a stem cell or to develop into a specialised cell such as a blood cell or muscle cell

88
Q

4 types of stem cells potency

A

Unipotent, multipotent, pluripotent, totipotent

89
Q

Unipotent

A

Can not differentiate, but are capable of self renewal

90
Q

Self renewal

A

The process by which stem cells divide to make more stem cells, perpetuating the stem cell throughout life

91
Q

Multipotent

A

Can differentiate into a number of closely related cell types within a certain type of tissue

92
Q

Pluripotent

A

Embryonic stem cells that can differentiate into any cell type found in an embryo but are not able to differentiate into extra-embryonic cells

93
Q

Totipotent

A

Able to differentiate into any type of cell in body including int extra embryonic cells such as those in the placenta eg. Zygote

94
Q

Embryonic stem cells

A

Are stem cells found in embryos and can develop into almost every cell type under the right conditions in a lab

95
Q

Adult stem cells

A

Found in adult tissue (eg bone marrow) these cells can only differentiate into the same type of liver cell as the tissue they came from

96
Q

How are adult stem cells used in animals

A

To replace damaged cells

97
Q

Things about adult stem cells

A

Present throughout life from birth
Multipotent
Could be artificially triggered to become pluripotent
Can be harvested from umbilical cords of newborn babies

98
Q

Advantages of embryonic stem cells

A

Can treat a wide variety of diseases
Can become any cell type because they are pluripotent

99
Q

Disadvantages of embryonic stem cells

A

Possible harm/death of embryo
Human rights/ ethical issues (the embryo cannot give consent)
Unreliable as this is not a well-tested method

100
Q

Advantages of adult stem cells

A

No ethical issues as adult can give consent for the stem cells to be collected
Safer, as this is a well tested method

101
Q

Disadvantages of adult stem cells

A

Possibility of infection during extraction of stem cells
Adult stem cells can only become one type of cell as they are multipotent
Can be very painful

102
Q

How do stems cells help red blood cell production

A

As red blood cells lack a nucleus, they cannot divide, meaning that new erythrocytes are constantly being formed from bone marrow stem cells in order to maintain the red blood cell count in the blood
This process is known as erythropoiesis

103
Q

What form the transport system of plants

A

Xylem vessel and phloem

104
Q

What are xylem and phloem formed form

A

Stem cells found in tissue between them (cambium)

105
Q

What type of cell is the cambium

A

is a meristem, which is the term given to any undifferentiated tissue in a plant that has the ability to give rise to new cells

106
Q

What does cambium do

A

the stem cells at the inner edge of the cambium differentiate into xylem cells and the stem cells at the outer edge of the cambium differentiate into phloem cells
Cambium cells that differentiate to form the xylem lose their cytoplasm, deposit lignin in their cell walls and lose their end cell walls
Cambium cells that differentiate to form the phloem lose some of their cytoplasm and organelles, and develop sieve plates (located at ends of the cells)

107
Q

Why do stem cells have huge potential in the therapeutic treatment of disease

A

Their ability to differentiate int multiple cell types

108
Q

Where do embryos for research come from

A

the waste (fertilised) embryos from in vitro fertilisation treatment
This means these embryos have the potential to develop into human beings
This is why many people have ethical objections to using them in research or medicine

109
Q

How many times can adult stem cells divide by mitosis

A

Adult stem cells can divide (by mitosis) an unlimited number of times but they are only able to produce a limited range of cell types

110
Q

What do adult stem cells in bone marrow produce

A

used to produce different types of blood cell

111
Q

What do adult stem cells in brain produce

A

used to produce different types of neural and glial cells

112
Q

Why is use of adult stem cell less controversial

A

Donor is able to give permission

113
Q

What needs to happen to use donated adult stem cells

A

they need to be a close match in terms of blood type and other body antigens
There is a chance that the cells used are rejected by the patient’s immune system

114
Q

Potential uses of stem cells in medicine

A

repair of damaged tissues, treatment of neurological conditions and research in developmental biology

A Level Biology (10 decks)

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