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Biology A Level Content > 2.1.6 Cell Division, Cell Diversity and Cellular Organisation > Flashcards

2.1.6 Cell Division, Cell Diversity and Cellular Organisation Flashcards

1
Q

What are the three main phases of the cell cycle?

A
  • Interphase
  • Nuclear division
  • Cytoplasmic division (cytokinesis)
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2
Q

What happens in the G1 phase?

A
  • Growth
  • Proteins and organelles are made
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3
Q

What happens in the S phase?

A
  • Replication of DNA (synthesis)
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4
Q

What happens in the G2 phase?

A
  • Organelles made
  • Energy stores increased
  • DNA is checked for errors
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5
Q

What does a checkpoint do?

A

Verify that the previous part of the cell cycle has been completed
e.g. G1, G2, spindle assembley

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6
Q

What is the G1 checkpoint?

A
  • Between G1 and S phases
  • Checks for cell size, nutrients, growth factors and DNA damage
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7
Q

What is the G2 checkpoint?

A
  • Between G2 and nuclear division phases
  • Checks for cell size, DNA replication and DNA damage
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8
Q

What is the spindle assembly (metaphase) checkpoint?

A
  • At metaphase
  • Checks that chromosomes are aligned and attached to spindles at the centromeres
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9
Q

What is G0?

A
  • When a cell leaves the cell cycle
  • Happens when checkpoints aren’t satisfied
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10
Q

Why does a cell enter G0?

A

Differentiation:
- Cell becomes specialised
- Performs this function indefinitely

Damaged DNA:
- Can no longer replicate (senescent)

Age:
- The older you are, the more senescent cells you have
- Linked with cancer and arthritis

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11
Q

What is cancer and how is it caused?

A
  • Caused by mutation of genes that regulate the cell cycle
  • Uncontrolled growth of cells
  • Forms a tumour
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12
Q

How can cancer be treated?

A
  • Prevent DNA replicating or inhibit metaphase (interfere with spindle fibres)
  • Can be done using cisplastin or vinca alkaloids
  • Treating cancer also affects normal cells and can cause hair loss
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13
Q

What are the stages of mitosis?

A
  1. Interphase
  2. Prophase
  3. Metaphase
  4. Anaphase
  5. Telophase
  6. Cytokinesis
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14
Q

What happens in interphase?

A
  • Chromosomes are invisible prior to mitosis
  • Long and thin
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15
Q

What happens in prophase?

A
  • Chromosomes condense and become visible
  • Nuclear envelope and nucleolus disappear
  • Centrioles move to the opposite ends of the cell
  • Spindle fibres attach to centromeres and start to move chromosomes to the equator
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16
Q

What happens in metaphase?

A
  • Chromosomes arrange themselves along the equator of the cell
  • Equator is known as the metaphase plate
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17
Q

What happens in anaphase?

A
  • Each of the 2 threads of the chromosome (chromatid) migrates to an opposite pole by shorting spindle fibres
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18
Q

What happens in telophase?

A
  • Nuclear envelope reforms
  • Nucleolus reforms
  • Chromosomes uncoil and become long and thin again
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19
Q

What happens in cytokinesis?

A
  • Cell divides into 2 daughter cells that are identical to the parent cell
  • Division of the cytoplasm
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20
Q

What is the difference between a chromatid and chromosome?

A

1 chromosome is made of 2 chromatids

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21
Q

What is the process of cytokinesis in animal cells?

A
  • Cleavage furrow forms in the middle of the cell
  • Cell surface membrane is pulled inwards by the cytoskeleton and fuses
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22
Q

What is the process of cytokinesis in plant cells?

A
  • Plant cells have a cell wall which prevent a cleavage furrow
  • Vesicles from the golgi apparatus line up along the metaphase plate
  • Vesicles fuse with each other and the cell surface membrane
  • New cell wall forms
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23
Q

What is the importance of mitosis?

A
  • Growth
  • Differentiation
  • Repair
  • Asexual reproduction in plants, animals and fungi
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24
Q

Why are plant root tips a good source of cells for mitosis?

A
  • Continually growing at regions called meristems
  • Meristems are constantly dividing
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25
Q

How do you calculate mitotic index?

A

Mitotic index = number of actively dividing cells in field of view/number of cells in field of view

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26
Q

What are homologous chromosomes?

A
  • The same genes in the same positions (could be different alleles)
  • One from each parent
  • Same length and size
27
Q

What is an allele?

A

Different versions/forms of a gene

28
Q

What is a locus?

A

Where on the chromosomes the alleles are

29
Q

What is a gamete?

A

A haploid cell involved in sexual reproduction (e.g. egg and sperm or pollen and egg)

30
Q

What does haploid mean?

A

Half of the number of chromosomes

31
Q

What does diploid mean?

A

Full number of chromosomes

32
Q

How is genetic variation created?

A
  • Crossing over
  • Independent segregation of chromosomes (random assortment)
  • Random fertilisation
33
Q

What is crossing over?

A
  • When chromatids twist around each other and swap
  • Contain the same genes but different alleles
  • Only within homologous pairs
34
Q

What is the independent segregation of chromosomes?

A
  • Chromosomes align on the metaphase plate randomly during metaphase (meiosis I)
  • One from each pair passes into a daughter cell
35
Q

What is random fertilisation?

A
  • Any sperm can fertilise any egg
  • Each individual is unlike any to have existed before or any that will exist again
36
Q

What are the main stages of meiosis?

A
  1. Interphase
  2. Meiosis I
  3. Meiosis II
37
Q

What happens in interphase?

A
  • DNA duplicates during S phase
38
Q

What happens in meiosis I?

A
  • The first division
  • Each chromosome is made up of two sister chromatids
  • Genetic recombination takes place at random (chromosomes cross over and swap blocks of genes)
  • Prophase I, metaphase I, anaphase I and telophase I
  • Homologous chromosomes segregate into 2 nuclei
  • Nuclear envelope forms
39
Q

What happens in meiosis II?

A
  • The second division
  • Identical to mitosis
  • Prophase II, metaphase II, anaphase II and telophase II
  • Chromatids from individual chromosomes are pulled to opposite poles
  • Independent assortment
  • 4 haploid gametes form
  • Known as reduction division
40
Q

How are erythrocytes (RBCs) specialised?

A
  • No nucleus, mitochondria, Golgi apparatus or RER
  • Biconcave discs for a large surface area
  • Flexible so it can fit through small gaps
  • Contain haemoglobin
41
Q

How are neutrophils specialised?

A
  • Lobed nucleus which allows them to fit through small gaps
  • Flexible shape for engulfing pathogens/foreign particles
  • Lysosomes contain digestive/hydrolytic enzymes
42
Q

How are squamous epithelial cells specialised?

A
  • Flat and thin to allow for rapid diffusion
43
Q

How are ciliated epithelial cells specialised?

A
  • Have cilia (hair like structure)
  • Line the trachea and waft mucus away from the lungs
  • Work in conjunction with goblet cells which produce mucus
44
Q

How are sperm cells specialised?

A
  • Flagellum for movement
  • Acrosome contains digestive enzymes to penetrate the egg
  • Lots of mitochondria to provide energy
  • Less cytoplasm to reduce mass
45
Q

How are palisade cells specialised?

A
  • Chloroplasts to absorb light for photosynthesis
  • Elongated (tall and thin) so it’s further to travel before going through a second cell wall (maximise light absorption)
46
Q

How are root hair cells specialised?

A
  • Long projection increases surface area to absorb water and mineral ions from soil
  • Thin permeable cell wall
  • Lots of mitochondria to provide energy for active transport of mineral ions
47
Q

How are guard cells specialised?

A
  • In light, guard cells take up water into their vacuole and become turgid (stoma opens)
  • Inner wall becomes thicker and outer wall thinner so they bend
48
Q

How is squamous epithelia tissue specialised?

A
  • Single layer of flat cells
  • Thin surface allows easy exchange of substances
49
Q

How is ciliated epithelia tissue specialised?

A
  • Found on surfaces where things need to be moved
    E.g. trachea or oviduct
50
Q

How is cartilage tissue specialised?

A
  • Protects and strengthens
  • Found in connective tissue in joints, ears, nose, trachea
  • Chondrocytes produce an extracellular matrix of collagen fibres (strength) and elastin fibres (flexibility)
51
Q

How is muscle tissue specialised?

A
  • There are 3 types of muscle: skeletal, smooth, cardiac
  • Made up of bundles of elongated cells called muscle fibres
  • Contains contractile protein myofilaments called actin and myosin which form structures called myofibrils
52
Q

How is xylem tissue specialised?

A
  • Transports minerals and water up the stem
  • Supports the plant
  • Impregnated with lignin
  • Xylem cells are dead and have no cytoplasm
  • Parenchyma cells fill gaps between the other cells
  • Water transporting cells with wide lumen (vessel elements)
  • Fibres for support (made of lignin)
  • Tracheids for the transport of water and support in angiosperms (flowering plants)
53
Q

How is phloem tissue specialised?

A
  • Transports organic nutrients up and down the plant
  • Sieve tube elements: reduced cytoplasm, few organelles, end walls from sieve plates
  • Companion cells help the sieve cells with their functions using plasmodesmata which allow molecules to pass between cells
54
Q

What are the properties of stem cells?

A
  • Self renewal (make copies of themselves)
  • Differentiate (make other types of specialised cell)
55
Q

What are totipotent stem cells?

A
  • Has the potential to form any and every type of human cell
  • Found in a fertilised egg cell
56
Q

What happens when a fertilised egg cell divides?

A
  • Eventually certain genes will be turned on that a specific to a cell function
  • When becoming specialised, only the relevant gene will be translated from the DNA
57
Q

What are pluripotent stem cells?

A
  • Have the ability to differentiate into almost any type of cell
  • Can form all tissue types but not whole organisms
  • Found only in embryos
58
Q

What are multipotent stem cells?

A
  • Have the ability to differentiate into a limited number of specialised cell types
  • Can only form a range of cells within a certain type of tissue
  • Found in bone marrow (e.g.)
59
Q

What cells are
derived from a common stem cell in bone
marrow?

A
  • Erythrocytes
  • Neutrophils
60
Q

What are examples of distinct, differentiated
outcomes derived from a common stem cell in
meristems?

A
  • Xylem vessels
  • Phloem sieve tubes
61
Q

What is meristematic tissue?

A
  • Contains plant stem cells where the plant is growing
  • Found between phloem and xylem tissue and at the tips of roots and shoot
  • Contains dividing cells which can differentiate
62
Q

How can stem cells be used in medicine?

A
  • Can be transplanted into any area of the body that needs new healthy growth and they’ll adapt
  • Adaptation of stem cells and the following growth stimulates more new healthy growth which replaces or repairs damage or illness in the area
  • This can cure disease and improve quality of life
63
Q

What are the ethics associated with stem cells?

A
  • Objection to using stem cells
  • Destruction of embryo
  • Religious objections as some believe that life begins at conception
  • Embryo has rights
  • Ownership of genetic material
64
Q

Where could stem cells be gathered from?

A
  • Embryos left over from fertility treatment or abortions that were going to be discarded anyway
  • Embryos are now created to supply stem cells

Biology A Level Content (9 decks)

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