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A Level Biology > Module 2.1.6 Cell Division, Cell Diversity & Cellular Organisms > Flashcards

Module 2.1.6 Cell Division, Cell Diversity & Cellular Organisms Flashcards

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1
Q

What is the role of mitosis & the cell cycle?

A

To produce 2 genetically identical daughter cells for growth & repair of tissues

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2
Q

Are cells produced from mitosis genetically identical or genetically different?

A

Identical

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3
Q

What are the different processes in the cell cycle?

A

Interphase
Mitosis
Cytokinesis.

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4
Q

What is interphase?

A

The stage which the chromosomes in the cells replicate & start to condense

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5
Q

What happens during interphase?

A

G1
S
G2

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6
Q

What happens during growth 1 (G1) of interphase?

A

Cell synthesises proteins for replication & the cell size doubles

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7
Q

What happens during S of interphase?

A

The DNA replicates -> the chromosomes consist of 2 sister chromatids joined at a centromere

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8
Q

What happens during growth 2 (G2) of interphase?

A

The organelles in the cell divide

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9
Q

What happens during growth 2 (G2) of interphase?

A

The organelles in the cell divide

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10
Q

What are the 4 stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

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11
Q

What happens during prophase?

A

Chromosomes condense & become visible
Centrioles move to the opposite poles of the cell in animals cells & the mitotic spindle fibres form
The nuclear envelope & nucleolus break down so the chromosomes are free in the cytoplasm

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12
Q

What happens during metaphase?

A

The sister chromatids line up at the cell equator & attach to the mitotic spindle by their centromeres

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13
Q

What happens during anaphase?

A

The spindle fibres contract & the centromeres divide
The sister chromatids separate into 2 distinct chromosomes & are pulled to opposite poles of the cell
The spindle fibres then break down

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14
Q

Does anaphase require energy or not?

A

Yes (requires ATP)

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15
Q

Does anaphase require energy or not?

A

Yes (requires ATP)

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16
Q

What happens during telophase?

A

The chromosomes decondense & become invisible again
A new nuclear envelope forms around each new set of chromosomes -> results in 2 new nuclei with 1 copy of each chromosome

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17
Q

What happens during cytokinesis?

A

A new cell membrane forms & the cytoplasm contractiley divides

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18
Q

How is the cell cycle regulated?

A

There are checkpoints that are regulated by cell-signalling proteins

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19
Q

Why must the cell cycle be regulated?

A

To ensure that damaged cells do not progress to the next stage of the cell cycle

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20
Q

What happens during the checkpoint between G1 & S of interphase?

A

The cell checks for DNA damage & after the restriction point the cell enters the cycle

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21
Q

What happens during the checkpoint between G2 & M of the cell cycle?

A

The cell checks the chromosomes have replicated properly

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22
Q

What happens during the metaphase checkpoint of the cell cycle?

A

The cell checks that the sister chromatids have attached to the spindle fibres correctly

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23
Q

What is meiosis?

A

A form of cell division which produced 4 genetically different haploid cells known as gametes

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24
Q

How many stages of meiosis are there?

A

2

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25
Q

What happens during meiosis 1?

A

Homologous chromosomes pair to form bivalents
Crossing over occurs as the chiasmata
The cell divides into 2. The homologous chromosomes separate randomly & each cell contains either the maternal or paternal copy of the chromosome

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26
Q

What are homologous chromosomes?

A

A pair of chromosomes with genes at the same locus consisting of 1 maternal & 1 paternal

27
Q

What happens during meiosis 2?

A

There is independent assortment of sister chromatids & each cell then divides again -> produces 4 haploid cells

28
Q

Is there genetic variation in the cells produced by meiosis?

A

Yes

29
Q

How does meiosis produce genetic variation?

A

Crossing over during meiosis 1 & Independent assortment of homologous chromosomes & sister chromatids during meiosis 2 -> results in new combinations of alleles

30
Q

How do cells become specialised?

A

Some genes are expressed while others are silenced due to cell differention by transcription factors

31
Q

What are transcription factors?

A

A protein that controls the transcription of genes so that only some parts of the DNA are expressed so cells can become specialised

32
Q

How do transcription factors work?

A

They move from the cytoplasm into the nucleus & bind to the promoter region upstream of the target gene. This makes it easier/more difficult for RNA polymerase to bind to the gene which increases/decreases the rate of transcription

33
Q

What is a stem cell?

A

Undifferentiated cells that can divide indefinitely & turn into other specific cells types

34
Q

What are the 4 types of stem cell?

A

Totipotent
Pluripotent
Multipotent
Unipotent

35
Q

What are totipotent stem cells?

A

Stem cells that can divide & produce any type of body cell
Occur for a limited time in early mammalian embryos
Can only translate part of their DNA during development which results in cell specialisation

36
Q

What are pluripotent stem cells?

A

Found in embryos & can become almost any type of cell
Usually used in research

37
Q

What are multipotent stem cells?

A

Stem cells that can only develop into few different types of cells e.g. bone marrow

38
Q

What are unipotent stem cells?

A

Stem cells that can only differentiate into one type of cell

39
Q

What are the different sources of stem cells in mammals?

A

Embryos up to 16 days after conception contain pluripotent cells -> can differentiate into any type of cell
Umbilical cord blood contains multipotent cells (similar to adults)
Placenta -> multipotent stem cells that can develop into a limited number of specialised cells
Adult stem cells -> can produce different cells to repair those within a particular tissue/organ

40
Q

What are some uses of stem cells?

A

Repairing damaged tissues
Drug testing on artificially grown tissues
Treating neurological diseases e.g. Alzheimer’s
Development biology research e.g. formation of organs

41
Q

What are the 2 groups of specialised cells in the blood?

A

Erythrocytes (RBC)
Leukocytes (WBC)

42
Q

What are the specialised features of erythrocytes (RBC)?

A

Biconcave, have no nucleus & have lots of haemoglobin to carry oxygen

43
Q

What are some of the different types of Leukocyte (WBC)?

A

Lymphocytes
Eosinophils
Neutrophils -> engulf foreign bacteria

44
Q

How do RBC & WBC form in the blood?

A

From multipotent stem cells in the bone marrow

45
Q

What is the lifespan of an erythrocyte?

A

Short since they cannot undergo mitosis -> no nucleus

46
Q

What is the relationship between a system & specialised cells?

A

Specialised cells -> tissues -> organs -> organ systems

47
Q

What is differentiation?

A

The process by which stem cells become specialised

48
Q

How are sperm cells specialised for sexual reproduction?

A

Tail/flagellum -> facilitates movement
Many mitochondria -> supplies energy for the sperm to swim
Acrosome on the head -> contains digestive enzymes. To digest the protective layer of ovum so the spem can penetrate it
Streamlined -> swimming

49
Q

What are some plant cells that are specialised for their function?

A

Palisade cells
Root hair cells
Guard cells

50
Q

How are palisade cells specialised for their function?

A

Contain:
Chloroplasts -> can move in the cytoplasm & contain chlorophyll (absorb more light for photosynthesis)
Rectangular shaped -> can be closely packed together -> maximises photosynthesis
Thin cell walls -> increases rate of Co2 diffusion
Large vacuole -> maintains turgor pressure (for structure & support) & stores water (photosynthesis)

51
Q

How are root hair cells specialised for their function?

A

Root hairs -> increase surface area (absorb more water & minerals) & thin cell wall (easier osmosis of water/active transport of minerals)
Large vacuole -> stores more water & minerals

52
Q

How are guard cells specialised for their function?

A

Stomata -> faster gas exchange (photosynthesis)
Thicker cells walls on one side (inside) -> stomata can form as the cell doesn’t change shape symmetrically

53
Q

What are some different animal tissues that are specialised for their function?

A

Squamous epithelial cells
Ciliated epithelial cells
Cartilage
Muscles

54
Q

How are squamous epithelial cells specialised for their function?

A

Very thin -> one cell thick to allow rapid diffusion across a surface e.g. the lungs

55
Q

How are ciliated epithelial cells specialised for their function?

A

Cilia -> move in a rhythmic manner & waft mucus to be excreted
Goblet cells -> secrete mucus to trap unwanted particles to avoid them getting into the alveoli

56
Q

How is cartilage specialised for its function?

A

Contains:
Fibres of proteins (elastin & collagen) -> firm yet flexible to prevent bones rubbing together
Chondrocyte cells -> embedded in extracellular matrix

57
Q

How are muscles specialised to their function?

A

Skeletal muscle fibres (attached to bones) -> contains myofibrils that have contractile proteins

58
Q

What are some examples of plant tissues that are specialised for their function?

A

Epidermis
Xylem & phloem tissues

59
Q

How is the plant epidermis specialised for its function?

A

Closely packed cells to cover the plant’s surface -> waxy waterproof cuticle -> reduces water vapour loss
Contains guard cells

60
Q

What is the function of the xylem vessel?

A

Transports water & minerals throughout plants

61
Q

How is xylem tissue specialised for its function?

A

Elongated vessel elements made of dead cells
Thick cell walls that are strengthened with lignin -> sustains water pressure to maintain unilateral flow & provides structure & support

62
Q

What is the function of the phloem vessel?

A

Transports assimilates (sucrose) throughout the plant

63
Q

How is phloem tissue specialised for its function?

A

Columns of sieve tube cells
Perforated cell walls with sieve plates

64
Q

What are meristems?

A

Totipotent undifferentiated plant cells that can develop into various types of plant cells (including xylem & phloem vessels)

Found at the root & shoot tips

A Level Biology (18 decks)

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