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Biology > Cell Divison > Flashcards

Cell Divison Flashcards

1
Q

Outline the levels of organisation of a multicellular organism.

A
  1. (Atom, molecule, macromolecule)
  2. Organelle
  3. Cell
  4. Tissue
  5. Organ
  6. Organ system
  7. Organism
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2
Q

Define ‘specialised’

A

Having a specific structure to suit a specific function.

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3
Q

Define ‘differentiation’

A

The process of a cell becoming differentiated. It involves the selective expression of genes in a cell’s genome.

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4
Q

Define ‘cell’

A

The basic unit of life. It consists of cellular contents surrounded by a plasma membrane. All life is composed of these basic units whether it is unicellular or multicellular.

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5
Q

Define ‘tissue’

A

A collection of differentiated cells that work together to perform a specialised function/functions.

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6
Q

Define ‘organ’

A

A collection of tissues that work together to perform a particular function in an organism.

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7
Q

Define ‘organ system’

A

A number of organs working together to carry out a major function in the body.

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8
Q

Explain why multicellular organisms have specialised cells.

A

Cells do not have to compromise as they divid the labour and can be very efficient at a single job rather than being stretched across many roles. Cells are better at their respective jobs so the organism is more efficient.

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9
Q

Specialisation of erythrocytes

A
  • Transport oxygen around body.
  • Flattened biconcave shape increases surface area to volume ration which optimises diffusion of oxygen into cell.
  • Contain Haemoglobin to carry oxygen.
  • No nucleus or many other organelles which increases space for Haemoglobin.
  • Flexible so can squeeze through narrow capillaries.
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10
Q

Specialisation of neutrophilsp

A
  • Phagocytes
  • Multi-lobed nucleus to squeeze through small gaps and get site of infection.
  • Granular cytoplasm containing many lysosomes which contain enzymes that attack pathogens and hydrolyse the pathogen’s molecules.
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11
Q

Specialisation of sperm cells

A
  • Male gametes of animals
  • Deliver genetic information into female gamete (ovum).
  • Has a tail/flagellum for locomotion.
  • Contain many mitochondria to supply energy needed to swim.
  • Acrosome on the head of the cell contains digestive enzymes which are released to digest the protective layers around the ovum and allow the cell to fuse with the ovum.
  • Contain a haploid nucleus in order to restore the diploid number of chromosomes at fertilisation.
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12
Q

Specialisation of palisade cells

A
  • Contain chloroplasts to absorb large amounts of light for photosynthesis.
  • Rectangular box shaped so that they can be closely packed to form a continuous layer.
  • Long cells so more opportunity for light to hit a chloroplast.
  • Thin cell walls increasing rate of diffusion for CO2 for photosynthesis.
  • Larger vacuole to maintain turgid pressure.
  • Chloroplasts can move within cytoplasm to absorb more light.
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13
Q

Specialisation of root hair cells

A
  • Long extensions called root hair cells which increase the SA of the cell. This maximises the uptake of water and minerals from the soil.
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14
Q

Specialisation of guard cells

A
  • Pairs on surface of leaves from small openings called stomata — the openings are necessary for CO2 to enter plants for photosynthesis.
  • When these cells lose water and become less swollen as a result of osmotic forces, they change shape and the stomata closes to prevent further water loss from the plant.
  • The cell wall on guard cells is thicker on one side so the cell does not change shape symmetrically as its volume changes.
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15
Q

State 4 main categories of tissues in animals.

A
  1. Epithelial tissue
  2. Connective tissue
  3. Muscle tissue
  4. Nervous tissue
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16
Q

Specialisation of squamous epithelium

A
  • Very thin tissue due to the flat cells that make it up and because it’s only one cell thick.
  • It is present when rapid diffusion across a surface is essential.
  • It forms the lining of the lungs and allows rapid diffusion of oxygen into the blood.
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17
Q

Specialisation of ciliates epithelium

A
  • Made of cells with hair-like structures called cilia on one surface that move in a rhythmic manner.
  • Lines the trachea causing mucus to be swept away from the lungs.
  • Goblet cells are also present, releasing mucus to trap any unwanted particles present in the air.
  • This prevents the particles, which may be bacteria, from reaching the alveoli once inside the lungs.
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18
Q

Specialisation of cartilage

A
  • Connective tissue found in the outer ear, nose, and at the ends of/between bones.
  • Contains fibres of the proteins elastin and collagen.
  • Firm, flexible collective tissue composed of chondocyte cells embedded in an extracellular matrix. This tissue prevents the ends of bones from rubbing together and causing damage.
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19
Q

Specialisation of muslce

A
  • Can contract to move bones or perform other contractile functions.
  • The form that moves bones has long, multinucleate cells with contractile elements called myofibrils. They contain many mitochondria to supply the energy for contraction.
  • The cells appear striped due to the arrangement of the proteins, actin, and myosin — which male up the myofibrils.
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20
Q

Specialisation of plant epidermis

A
  • Single later of closely packed cells covering the surface of plants.
  • Covered in waxy, waterproof cuticle to reduce water loss.
  • Stomata, formed by guard cells, are preset in this tissue. They allow CO2 in and water vapour + oxygen out.
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21
Q

Specialisation of xylem tissue

A
  • Vascular tissue responsively for the transport of water/minerals through plants.
  • Composed of vessel elements which are elongated, hollow, dead cells.
  • The joining wall of these elements have broken down to leave continuous tubes.
  • The side walls are thickened with cellulose and strengthened with lignin to provide structural support for plants.
  • Contain tracheids — very similar to vessel elements but remain separated dead cells which are connected by small holes called pits rather than combining to form true vessels.
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22
Q

Specialisation of phloem tissue

A
  • Vascular tissue responsible for the transport of organic nutrients (particularly sucrose).
  • Transport occurs from where the sucrose is made (either from the products of photosynthesis or from the stores of carbohydrates) to where it is needed.
  • It is composed of sieve tubes cells (or sieve tube elements) which only have cytoplasm around their edges and are joined by highly perforated sieve plates into relatively hollow columns.
  • There are also companion cells which perform all of the cellular functions of the sieve tube cells.
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23
Q

State examples of organ systems in animals.

A
  • Digestive
  • Nervous
  • Gas exchange
  • Endocrine
  • Reproductive
  • Circulatory/cardiovascular
  • Skeleto muscular
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24
Q

Define ‘stem cells’

A

Undifferentiated cells with the potential to differentiate into a variety of the specialised cell types of the organism.

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25
Q

Define ‘undifferentiated’

A

An unspecialised cell originating from meiosis or mitosis.

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26
Q

Define ‘totipotent’

A

A stem cell that can differentiate into any type of cell and form a whole organism.

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27
Q

Define ‘pluripotent’

A

A stem cell that can differentiate into any type of cell, but not form a whole organism (all cell types of the indecently functioning organism — not placental cells).

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28
Q

Define ‘embryonic stem cell’

A

Stem cell found in embryos — can differentiate into anything!

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29
Q

Define ‘adult stem cells’

A

Adult stem cells are found in the bone marrow of adults and have a more limited potency. They can only develop into a limited number of cell types (i.e they are multipotent).

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30
Q

Describe the characteristic abilities of stem cells.

A
  • Not been through much differentiation.
  • Can divide again and again producing many cells.
  • Function is to produce more cells (specialised cells perform specific tasks and have entered G0 so no longer produce new cells — do not do the cell cycle).
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31
Q

Explain the importance of stem cells and why their activity must be carefully controlled.

A
  • Source of new cells necessary for growth, development, and tissue repair.
  • If they don’t divide fast enough, then they’re not efficient enough for tissue repair.
  • If they’re too fast, they then form masses which could become cancerous.
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32
Q

State 3 types of stem cells and give examples of where they occur in animals.

A
  1. Totipotent: Zygote
  2. Pluripotent: Embryos
  3. Multipotent: Bone marrow
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33
Q

State where stem cells occur in plants and state which type of potency they have.

A
  • In meristemic tissue (meristems) in the cambium between phloem and xylem, and at the tips of roots and shoots.
  • The cells are pluripotent.
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34
Q

Outline how a cell can become specialised.

A
  • The stem cell will be cycling through the cell cycle, doing mitosis.
  • It enters phase G0 and becomes committed to becoming a certain type of cell.
  • It then goes through a series of changes to become suited for the role.
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35
Q

Outline the production of erythrocytes and neutrophils and why it’s necessary for them to be constantly produces.

A
  • Produced from stem cells in the bone marrow.
  • Nucleus ejected and Haemoglobin builds up for RBC etc.
  • Nucleus becomes lobed for neutrophil etc. RBCs have very short lifespan (120 days) due to lack of organelles and nucleus so they they need constant replacement.
  • Production increases during infection.
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36
Q

Outline how phloem and xylem are produced.

A
  • Stem cells in meristem in vascular cambium, sandwiched between phloem and xylem.
  • Cells differentiate into specialised tissue cells as plant grows.
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37
Q

List 7 diseases that stem cells have the potential to treat and how they’d be useful in each case.

A
  1. Heart disease — stem cells transplanted to replace muscle that is irreparable damaged.
  2. Type 1 diabetes — own immune system destroys insulin producing cells, stem cells could replace them as alternative for injecting insulin for life.
  3. Parkinson’s disease — symptoms of shaking and rigidity caused by death of dopamine producing cells in the brain — drugs only delay process and stem cells could potentially replace the dead cells.
  4. Alzheimer’s disease — brain cells destroyed by build up of abnormal proteins — current drugs just alleviate the symptoms.
  5. Macular degeneration — causes blinders in the elderly and diabetics — promising research.
  6. Birth defects — reversing previously untreatable defects — successful in mice.
  7. Spinal injuries — stem cells implants into spinal cord of rats have recovered some movement in hinds legs after paralysis.
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38
Q

Describe how stem cells may be useful for treating burns.

A

Stem cells used to grow skin on biodegradable meshes — quicker than traditional skin graft from other body parts.

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39
Q

Describe two ways in which stem cells may be useful in research.

A
  1. Drug trials — to test new drugs on them before animals/humans.
  2. Instruments in the study of developmental biology — how cells divide to form multicellular organisms and how it sometimes goes wrong.
40
Q

Describe arguments for the use of embryonic stem cells for research/medicine.

A
  • Extra embryos from fertility treatment destroyed anyways.
  • Relives suffering if it can find treatments.
41
Q

Describe arguments against the use of embryonic stem cells for research/medicine.

A
  • Belief of life starting at conception and therefore killing embryos is murder.
  • Does the embryo have rights?
  • Who owns the genetic material used for research?
  • Risk of infection, rejection, cancer, and false hope.
42
Q

Define the term ‘induced pluripotent stem cell’ and explain why they may be useful in research and medicine.

A
  • Cells isolated from patient and grown in a dish treated with ‘reprogramming’ factors which change them into pluripotent stem cells which can then be stimulated to differentiate into a variety of cell types.
  • Genetically identical to patient so no risk of rejection and none of the ethical issues surrounding embryos.
43
Q

Describe how plant stem cells may be useful for medicine using the example of the drug ‘Paclitaxel’ from the bark of yew trees.

A
  • Paclitaxel is used to treat breast and lung cancer and cannot be chemically synthesised, but there is a limited supply of yew trees and extraction methods can be expensive.
  • Stem cells can be cultured and the used to produce Paclitaxel in sustainable quantities and more cheaply.
44
Q

Describe how the use of stem cells and gene therapy may be combined to treat SCID.

A
  • Severe combined immunodeficiency — patient does not produce T cells, without B cells cannot function either.
  • Treatemtn by bone marrow transplant relies finding donor match.
  • Aim is to remove some of the patients own bone marrow stem cells and genetically alter them so that when replaced, they produce white blood cells as they should.
  • Some success so far although in some patients, another gene was damaged causing the development of leukaemia.
45
Q

List the stages if the cell cycle in order.

A
  • G1
  • S
  • G2
  • Mitosis
  • Cytokinesis
  • G0
46
Q

Describe G1

A
  • First stage
  • Cellular contents, excluding chromosomes, are duplicated.
  • Organelles duplicated, more cytoplasm, more membrane, energy storage.
47
Q

Describe S

A
  • Second stage
  • Each of the chromosomes is duplicated.
48
Q

Describe G2

A
  • Third stage
  • The cell ‘double checks’ the duplicated chromosomes for errors, making any needed repairs.
  • Further increase in size and build up of energy store.
49
Q

Describe Mitosis

A
  • Fourth stage
  • Division of the nucleus
    —> Prophase, Metaphase, Anaphase, Telophase
    (PETER MUST ALWAYS TRY)
50
Q

Describe Cytokinesis

A
  • Fifth stage
  • Division of the cytoplasm
51
Q

Describe G0

A
  • Sixth stage
  • Cell division stops.
  • Can undergo differentiation and specialisation.
52
Q

List the 3 stages of interphase in order and describe what happens at each stage.

A
  • G1: Growth of cell, duplication of organelles etc.
  • S: Chromosomes duplicate
  • G2: Increase in size, energy store, centrosomes replicate
53
Q

List the 2 stages of the mitotic phase and outline what happens at each stage.

A
  1. Mitosis — Nuclear division (PMAT)
  2. Cytokinesis — Division of the cytoplasm
54
Q

Describe the significance of G0 as a phase that cells enter when they leave the cell cycle.

A

In G0, cells no longer divide to reproduce but can differentiate to become specialised for a specific function.

55
Q

Outline the role of checkpoints to control the cell cycle.

A

Checkpoints ensure that each division is successful in producing two genetically identical daughter cells.

They monitor and verify each stage is completed before moving cells can move on to the next stage.

56
Q

State 3 examples of checkpoints in the cell cycle, where they occur, and what it being checked at each checkpoint.

A
  1. G1 checkpoint: Cell size, nutrients, growth factors, DNA damage (end of G1).
  2. G2 checkpoint: Cell size, DNA replication, DNA damage (end of G2).
  3. Spindle assembly checkpoint: chromosome attachment to spindles (end of metaphase).
57
Q

Outline the link between cell-cycle and cancer.

A

Cancer is caused by unregulated division of cells. This occurs when the proteins that regulate the cell cycle at the checkpoints do not function properly so division is uncontrolled and tumours form.

58
Q

Define ’mitosis’

A
  • Nuclear division stage of the mitotic phase of the cell cycle.
  • Results in daughter cells each having the same number and kind of chromosomes as the parent nucleus.
59
Q

Define ’chromosomes’

A
  • Structures of condensed and coiled DNA in the form of chromatin.
  • Chromosomes become visible under a light microscope when the cell is preparing to divide.
60
Q

Define ’chromatid’

A
  • Each of the two thread-like strands into which a chromosome divides longitudinally during cell division.
61
Q

Define ’sister chromatids’

A
  • Two identical copies of DNA (a chromosome) joined at a centromere.
62
Q

Define ’centromere’

A
  • Region at which two chromatids are held together.
63
Q

Define ’centrioles’

A
  • Components of the cytoskeleton of most eukaryotic cells composed of microtubules.
64
Q

Define ’spindle fibres’

A
  • A network of filaments that collectively form a mitotic spindle (in mitosis) and meiotic spindle (in meiosis).
  • Responsible in moving/segregating the chromosomes during nuclear division.
65
Q

Define ’homologous pairs’

A
  • Matching pair of chromosomes, one inherited from each parent.
66
Q

Describe how DNA is packaged in a chromosome.

A
  • Double-stranded DNA loops around histones, forming the nucleosome.
  • DNA can be further packaged by forming coils of nucleosomes, called chromatin fibres. These fibres are condensed into chromosomes during mitosis, or the process of cell division.
67
Q

List the stages of mitosis in order.

A
  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
68
Q

Describe prophase

A
  • First in mitosis
  • Duplicated chromosomes condense.
  • Spindle fibres extending/being formed towards centromeres.
  • Nuclear envelope fragmenting.
69
Q

Describe metaphase

A
  • Second in mitosis
  • Chromosomes line up in centre of cell (equator of cell/mitotic plate).
  • Spindle fibres attach to centromeres of each chromosome.
70
Q

Describe anaphase

A
  • Third in mitosis
  • Each chromatid is separated into its sister chromatids.
  • Spindle fibres shorted, pulling chromatids to each side of the cell.
71
Q

Describe telophase

A
  • Fourth in mitosis
  • Nuclear envelope reforming.
  • Chromosomes less condensed, unravelling.
72
Q

Explain the role of the centrioles and spindle fibres in mitosis.

A
  • Spindle fibres form from the centrioles.
  • They attach to centromeres to separate the chromatids and draw them to each side of the cell to form the two nuclei.
73
Q

Describe the process of cytokinesis in animal cells and plant cells — compare the two.

A

Animal cells:
- Cleavage furrow forms around the centre of the cell.
- Cytoskeleton draws membrane in until it is close enough to fuse to form two separate cells.

Plant cells:
- Vesicles from Golgi apparatus line up along the centre of the cell and fuse together, forming the new cell membranes.
- New sections of wall then from along the new surface membranes.

74
Q

Describe the purpose of mitotic cell division.

A

To create more identical cells.

75
Q

List 4 roles of mitotic cell division.

A
  1. Growth
  2. Repair
  3. Replace
  4. Asexual Reproduction
76
Q

Define ‘diploid’

A
  • A cell with 2n chromosomes — two copies of each chromosome, one from each parent.
77
Q

Define ‘haploid’

A
  • A cell with n chromosomes — one copy of each chromosome.
78
Q

Define ‘gamete’

A
  • A haploid sex cell — sperm or egg cell in animals.
  • They fuse at fertilisation to produce a gamete.
79
Q

Define ‘zygote’

A
  • The cell produced from fertilisation of a haploid egg cell by a haploid sperm cell.
80
Q

Define ‘meiosis’

A
  • The form of nuclear division that results in the pro union of haploid nuclei from a diploid nucleus.
81
Q

Define ‘reduction division’

A
  • Any form of nuclear division in which the chromosome number is reduced.
82
Q

Explain the role of meiosis in life cycles.

A
  • Meiosis is needed for sexual reproduction.
  • It halves the number of chromosomes so that the diploid number of chromosomes is restored at fertilisation.
  • It produces genetic variation in offspring.
83
Q

State two ways in which meiosis produces variation.

A
  1. Independant assortment
  2. Crossing over
84
Q

Suggest the importance of the creation of different allele combinations in populations.

A
  • Genetic variation is important in populations.
  • It makes them less vulnerable to disease or change in conditions as some will be more suited to a new environment.
85
Q

Define ‘homologous chromosomes’

A
  • Matching pairs of chromosomes, one inherited from each parent.
86
Q

Define ‘bivalent’

A
  • The name for two homologous chromosomes that have paired up in prophase I of meiosis (the pair of chromosomes join by synapsids and an alternative name for the structure of a tetrad).
87
Q

Define ‘crossing over’

A
  • The exchange of part of a chromosome between chromatids of homologous pairs.
  • Occurs at chisamata.
88
Q

Define ‘chiasmata ’

A
  • Sections of DNA which became entangled during crossing over, break and rejoin during anaphase I of meiosis — sometimes, this results in an exchange of DNA between bivalent chromosomes, forming recombinant chromosomes and producing genetic variation.
89
Q

Define ‘recombinant chromatid’

A
  • Chromatids with a combination of DNA from both homologous chromosomes, formed by crossing over and chiasmata in meiosis.
90
Q

Define ‘Random independent assortment’

A
  • The fact that which daughter cell a chromosome ends up in after Meiosis I or a chromatid ends up in after Meiosis II is a random and independent of the fate of chromosomes from other homologous pairs.
91
Q

Describe the stages of meiosis.

A
  • Meiosis I: Chromosomes paired up — bivalent line up along centre of cell. It is the whole chromosomes that are pulled to each side of the cell still in duplicated form (2n to n).
  • Meiosis II: Same mechanism as mitosis but with fewer chromosomes — chromatids are separated into each side of the cell.
92
Q

State the stages of meiosis in order.

A
  • Prophase I
  • Metaphase I
  • Anaphase I
  • Telophase I
  • Cytokinesis I
  • Prophase II
  • Metaphase II
  • Anaphase II
  • Telophase II
  • Cytokinesis II
93
Q

Describe the process of crossing over and explains how it produces genetic variation.

A
  • Chromatids become entangled at chiasmata, sections of DNA break off and are exchanged so that the chromatids no longer contain solely maternal or paternal DNA.
  • This means that each of the 4 daughter cells are different and there are an infinite possibilities for different combinations of DNA producing genetic variation in offspring.
94
Q

Describe the process of random independent assortment and how it produces genetic variation.

A
  • When bivalent line up in Meiosis I or chromosomes line up in Meiosis II, they have an equal chance of lining up in a way that would make a particular chromosome go to one pole of the cell or the other.
  • This means that each group of chromosomes at either pole will have some that originally came from the mother and some that came from the father.
95
Q

Explain (given the chromosome number of the species) how to calculate the total number of possible genetically different gametes that could be produced through independent assortment only.

A

No. of chromosomes squared.

Biology (25 decks)

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