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Biology Module 2 > 2.6 Cell Division, Cell Diversity and Cellular Organisation > Flashcards

2.6 Cell Division, Cell Diversity and Cellular Organisation Flashcards

Cell Division and Cellular Organisation

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1
Q

what is the cell cycle

A
  • process that all body cells in multicellular organisms use to grow and divide
  • sequence of ordered events which take place in a cell, resulting in cell division
  • eukaryotic organisms
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2
Q

what are the two phases of the cell cycle

A
  • interphase (growth and DNA replication, and normal metabolic processes of cell)
  • M phase, mitotic ( mitosis and cytokinesis)
  • still a CONTINUOUS process
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3
Q

what growth phases is interphase divided into

A

G1
S1
G2

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4
Q

how is the cell cycle regulated

A

-by checkpoints
- occur at key points in the cycle to make sure it is OK for the process to continue

  • if not, sends cell into G0 = rest phase where cell leaves the cycle (e.g. once differentiated, cell DNA has become damaged
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5
Q

what does the G1 checkpoint do

A
  • checks that the chemicals needed for DNA replication are present
  • checks for any damage to DNA
    … AS before entering s phase, at the end of G1
  • cell size, nutrients, growth factors too
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6
Q

what does the G2 checkpoint do

A
  • checks whether all the DNA has been replicated without damage
  • checks cell cycle
    …AS before cell can enter mitosis, at the end of G2
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7
Q

what does the metaphase checkpoint do

A
  • cell checks that all the chromosomes are attached to the spindle
    …AS before mitosis can continue
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8
Q

what is mitosis needed for

A
  • growth of multicellular organisms
  • repairing damaged tissues
  • making genetically identical cells
  • asexual reproduction
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9
Q

what type of reproduction is mitosis

A
  • asexual reproduction
  • for some plants, animals and fungi
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10
Q

what happens in interphase

A
  • cell carries out normal functions (respiration)
  • cell’s DNA unravels and replicates (double its genetic content)
  • organelles are synthesised so increase in number
  • ATP content is increased (provides energy needed for cell division)

-G1 and G2 = cell grows and new organelles and proteins are made
-S = cell replicates its DNA

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11
Q

what are the 4 phases of mitosis

A

Prophase
Metaphase
Anaphase
Telophase

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12
Q

what do chromosomes look like at the start of mitosis vs the end

A
  • double stranded
  • because each chromosome has made an identical copy of itself during interphase
  • by the end, they end up as single-stranded chromosomes in new daughter cell
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13
Q

explain the technical shape of chromosomes at the beginning of mitosis

A
  • 2 chromosomes joined in middle by centromere (dot in middle)
  • each separate strand is called a chromatid (refer to both as sister chromatids)
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14
Q

what happens in prophase

A
  • the chromosomes condense, getting shorter and fatter
  • centrioles (tiny bundles of protein) start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle
  • the nuclear envelope breaks down
  • chromosomes lie free in the cytoplasm
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15
Q

what happens during metaphase

A
  • the chromosomes (each with two chromatids) line up in middle of the middle of the cell
  • become attached to the spindle by the centromere
  • at checkpoint, cell checks that all the chromosomes are attached to the spindle
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16
Q

what happens during anaphase

A
  • the centromeres divide
  • separates each pair of sister chromatids
  • spindle contracts, pulling chromatids to opposite ends of the cell (centromere first)
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17
Q

what happens in telophase

A
  • the chromatids reach opposite poles of the spindle
  • they uncoil and become long and thin again
    -they’re called chromosomes again
  • a nuclear envelope forms around each group of chromosomes
  • now are two nuclei
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18
Q

what happens during cytokinesis

A
  • the cytoplasm divides
    -in animal cells, the cleavage furrow forms to divide the cell membranes
  • usually begins in anaphase and ends in telophase
  • separate process to mitosis
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19
Q

what do you end up with at the end of mitosis

A
  • two daughter cells genetically identical to the original cell and to another
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20
Q

PAG: how would you be able to observe cells dividing in mitosis

A
  • stain chromosomes so that you can see them under a microscope
  • would be able to watch what happens to them during mitosis
  • e.g. use plant root cells under a light microscope
    -interphase: chromosomes spread out and not condensed
  • use a SQUASH microscope slide = squashed under a cover slip = easier to see the chromosomes
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21
Q

what happens during sexual reproduction

A

gametes (egg and sperm) join together at fertilisation to form a zygote
- zygote then divides and forms a new organism

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22
Q

where does meiosis occur

A
  • cell division that occurs in the reproductive organs to form gametes
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23
Q

why can meiosis be described as a reduction reaction

A
  • cells begin with a full number of chromosomes to start with, but the cells that are formed have half the number of normal chromosomes (called haploids)
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24
Q

what type of cells does meiosis form

A

genetically different
- because new cells end up with a different combination of chromosomes

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25
Q

what are the two divisions of meiosis, and which is the reduction one?

A

meiosis I and meiosis II
- meiosis I is the reduction one, where the cells become haploids

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26
Q

how many chromosomes are there in humans

A

46, 23 pairs
- one from mum, one from dad

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27
Q

what are homologous pairs

A
  • a pair of chromosomes which are the same size and have the same genes (though could be different versions of the gene (allele - which all have the same locus, position, on a chromosome))
  • one from your mum (maternal)
  • one from your dad (paternal)
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28
Q

what happens during prophase I

A
  • the chromosomes condense, getting fatter and shorter
  • THE CHROMOSOMES ARRANGE THEMSELVES IN HOMOLOGOUS PAIRS
  • CROSSING OVER OCCURS
  • centrioles start to move to opposite ends of the cell, forming spindle fibres
  • the nuclear envelope breaks down
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29
Q

what is crossing over

A
  • occurs during prophase I, where the homologous pairs come together and pair up ( form bivalents)
  • the chromatids twist around each other and bits of the chromatis swap over
  • chromatids stoll contain the same gene, but have different combination of alleles
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30
Q

what happens during metaphase I

A
  • the HOMOLOGOUS PAIRS line up across the centre of the cell
  • attach to the spindle fibres by their centromeres
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31
Q

what happens during anaphase I

A
  • the spindle contracts, SEPARATING THE HOMOLOGOUS PAIRS
  • one chromosome goes to each end of the cell
32
Q

what happens during telophase I

A
  • a nuclear envelope forms around each group of chromsomes
33
Q

what happens after the first phase of meiosis

A
  • cytokinesis
  • two haploid daughter cells are produced
34
Q

what happens during meiosis II

A
  • very similar to mitosis
  • in anaphase II:
  • the pair of sister chromatids separate
  • each new daughter cell inherits one chromatid from each chromosome
35
Q

what does meiosis produce

A
  • 4
  • genetically different
  • haploid daughter cells
  • called gametes
36
Q

which are the 2 main events in meiosis which form genetically different daughter cells

A
  • crossing over
  • independent assortment of chromosomes
37
Q

how does crossing over of chromatids form genetically different daughter cells

A
  • each of the 4 daughter cells formed contain chromatids with different alleles
  • increases genetic variation across offspring
  • 2 will stay same, other two will have bits of eachother mixed together
38
Q

where does the independent assortment of chromosomes occur

A
  • lining up in metaphase I
  • separated in anaphase I
39
Q

how does independent assortment of chromosomes lead to genetic variation

A
  • when the homologous pairs line up in MI and are separated in AI, is is completely random which chromosomes from each homologous pair ends up with which daughter cell
    -so the 4 cells produced have completely different combinations of maternal and paternal chromosomes
  • “shuffling” of chromosomes leads to genetic variation
40
Q

what are multicellular organisms made out of

A
  • different types of cells that are specialised for their function
  • ALL have some form of stem cells
41
Q

what are stem cells

A
  • unspecialised cells that can develop into different type of cells
42
Q

where are stem cells found in humans

A
  • early embryos (develop into any type of cell)
  • few places in adults, e.g. bone marrow (only develop into a limited range of cells)
43
Q

what is differentiation

A

process by which a cell becomes specialised
(stem cells divide into new cells -> become specialised)

44
Q

what are adult stem cells used for

A

used to replace damaged cells

45
Q

how do plants use stem cells

A
  • needed to make new roots and shoots throughout their lives, as plants are always growing
  • can differentiate into various types of cells, like phloem and xylem
46
Q

what is meant by stem cells being able to renew themselves

A
  • they’re able to divide to produce more undifferentiated, stem cells
47
Q

what are bones, and describe structure

A
  • living organs
  • contain nerve and blood vessels
  • main bones of body have marrow in the centre
48
Q

what happens in the bone marrow

A
  • adult stem cells divide and differentiate to replace worn out blood cells
    -(erythrocytes and neutrophils)
  • always multipotent
49
Q

where are stem cells found in plants

A
  • in the meristems (parts of the plant where growth takes place)
  • always pluripotent
50
Q

where do xylem vessels and phloem sieve tubes get differentiated in a plant

A
  • in the vascular cambium (meristem cells found in between x and p)
  • go on to divide and differentiate
51
Q

how would stem cells be used to treat diseases

A
  • they could replace damaged tissues in a range of diseases, as can differentiate into specialised cells
  • e.g. neurological disorders like Alzheimer’s and Parkinson’s
52
Q

what is Alzheimer’s and how would stem cells be used to treat it

A
  • nerve cells in the brain die in increasing numbers
  • results in severe memory loss
  • stem cells could be used to regrow healthy nerve cells in patients
53
Q

what is Parkinson’s and how could stem cells be used to treat it

A
  • patients suffer from tremors they can’t control
  • disease causes a loss of a particular type of nerve cell in the brain
  • these cells release a chemical called dopamine, which is needed to control movement
  • transplanted stem cells may be used to help regenerate the dopamine-producing nerve cells
54
Q

how are neutrophils adapted

A
  • a type of white blood cell that defends the body against disease
  • FLEXIBLE SHAPE allows them to engulf foreign particles and pathogens
  • have MANY LYSOSOMES in the cytoplasm, which contain digestive enzymes to break down the engulfed particles
  • have a MULTI-LOBED NUCLEUS, which makes it easier for them to squeeze through small gaps and get to site of infection
55
Q

how are erythrocytes adapted

A
  • red blood cell which carry oxygen in the blood
  • BICONCAVE DISC SHAPE provides a large surface area for gas exchange
  • NO NUCLEUS so have more room for haemoglobin (the protein that carries oxygen)
56
Q

how are epithelial cells adapted

A
  • cover the surface of organs
  • joined by interlinking cell membranes and a membrane at their base
  • CILIATED= in airways, have CILIA to move particles away
  • SQUAMOUS= in the lungs, are VERY THIN to allow for efficient diffusion of gases
57
Q

how are sperm cells adapted

A
  • male sex cells
  • have a FLAGELLUM ( tail) so they can swim to the egg
  • have lots of MITOCHONDRIA, to provide the energy to swim
  • have ACROSOME, containing digestive enzymes to be able to penetrate the surface of the egg
58
Q

how are palisade mesophyll cells adapted

A
  • in leaves, do most of photosynthesis
  • contain MANY CHLOROPLASTS, so they can absorb a lot of sunlight
  • THIN WALLS, so carbon dioxide can easily diffuse into the cell
  • LARGE VACUOLE to maintain turgor pressure
59
Q

how are root hair cells adapted

A
  • absorb water and mineral ions from the soil
  • have a LARGE SURFACE AREA, for absorption
  • have a THIN, PERMEABLE WALL, for entry of water and ions
  • cytoplasm contains EXTRA MITOCHONDRIA, to provide energy needed for active transport
60
Q

how are guard cells adapted

A
  • found in pairs, with a tiny gap in between called the STOMA , which is the TINY PORES on the surface of the leaf used for gas exchange
  • in the light, guard cells TAKE UP WATER and become TURGID
  • their THIN OUTER WALL and THICKENED INNER WALLS force them to bend outwards, opening the stomata
  • allows the leaf to exchange gases for photosynthesis
61
Q

what is a tissue

A
  • a group of cells (plus the extracellular material excreted by them) that are specialised to work together to carry out a particular function
  • contains more than one cell type
62
Q

examples of animal tissues

A
  • squamous epithelium
  • ciliated epithelium
  • muscle tissue
  • cartilage
63
Q

what is squamous epithelium

A
  • single layer of flat cells lining a surface ((on a basement membrane))
  • found in many places
  • found in the alveoli lining the lungs
64
Q

what is ciliated epithelium

A
  • layer of cells covered in cilia
  • found on surfaces where things need to be moved
  • in the trachea, where cilia waft mucus along
  • have goblet cells to trap any unwanted bacteria
65
Q

what is muscle tissue

A
  • made up of bundles of elongated cells called muscle fibres
  • 3 different types of muscle tissue:
    1) smooth , found in lining of stomach wall
    2) cardiac, found in the heart
    3) skeletal, which you move
66
Q

what is cartiliage

A
  • a type of connective tissue found in the joints
  • shapes and supports the ears, nose and windpipe
  • formed when cells called chondroblasts secrete an extracellular matrix ( jelly like substance containing protein fibres) which they become trapped inside
67
Q

what is xylem tissue

A
  • plant tissue which:
    1) transports water around the plant
    2) supports the plant
  • contain hollow, dead xylem vessel strands
  • contain living parenchyma cells
  • strengthened by lignin
68
Q

what is phloem tissue

A
  • transports sugars around the plant
  • arranged in tubes
  • made of sieve cells, companion cells, and some ordinary plant cells
  • each sieve cell has end walls with holes in them, so that sap can move easily through
  • end walls are called sieve plates
69
Q

what is an organ

A
  • a group of different tissues that work together to perform a particular function
70
Q

what are examples of organs, and state what organs tissues they contain

A
  • LUNGS:
    -contain squamous epithelial tissue in alveoli,
    -ciliated epithelial tissue in the bronchi,
  • elastic connective tissue and vascular tissue in the blood vessels

-LEAVES:
- contains palisade tissue for photosynthesis,
- epidermal tissue to prevent water loss from leaf
- xylem and phloem tissues in the veins

71
Q

what is an organ system

A
  • a group of different organs working together to perform a particular function
72
Q

what is the respiratory system and what is it made out of

A
  • involved in breathing
  • lungs
  • trachea
  • larynx
  • mouth
  • diaphragm
73
Q

what is the circulatory system and what is it made out of

A
  • involved in blood supply
  • heart
  • arteries
  • veins
  • capillaries
74
Q

what is meant by the potency of stem cells

A

a stem cells ability to differentiate into different types of cells

  • greater the potency, the more types of cells a stem cell can differentiate into
75
Q

what are the 3 levels of potency

A
  • TOTIPOTENT: stem cells that can differentiate into any type of cell, e.g. first few cells in zygote
  • PLURIPOTENT: stem cells that can form all tissue types, not whole organisms, e.g. in early embryos
  • MULTIPOTENT: can only form a range of cells within a tissue type, e.g. in bone marrow

Biology Module 2 (6 decks)

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