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BIOLOGY OCR > Cell Division and Cell Differentiation > Flashcards

Cell Division and Cell Differentiation Flashcards

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1
Q

What are the stages of the Eukaryotic cell cycle?

A

Gap phase 1 (sometimes gap phase 0)
Synthesis
Gap phase 2
Meitosis

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2
Q

What happens during Gap phase 1?

A

Cell growth/increase size
Transcribe RNA
Duplicate organelles
Biosynthesis

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3
Q

What happens during synthesis?

A

DNA replication

commits the cell to completing the cell cycle

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4
Q

Why must synthesis occur very fast?

A

As DNA is replicate, bases get exposed which are susceptible to mutagenic agents

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5
Q

What happens during Gap phase 2?

A

Cell growth

Preparation for mitosis

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6
Q

Is it possible to exit the cell cycle if so, how?

A

Yes
This can happen through a resting phase called Gap phase 0 this is where:
Apoptosis (programmed cell death) can occur
Differentiation - stops dividing
Can stay there indefinitely

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7
Q

What are sister chromatids

A

Replicated chromosomes

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8
Q

How is the cell cycle regulated

A

Using checkpoints

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9
Q

Why does the cell cycle need to be replicated?

A

To prevent uncontrolled division of cells

Detect DNA damage

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10
Q

What happens if checkpoints fail?

A

Cancer can arise - which is the result of uncontrolled cell division/defects

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11
Q

When do the check points occur

A

Before synthesis and meitosis

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12
Q

What are the 2 checkpoints

A

G1/S (Gap phase 1 /Synthesis)

G2/M (Gap phase 2/Meitosis)

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13
Q

Can the cell cycle be reversed?Why?

A

No - because of the check points

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14
Q

What is the role of the G1/S checkpoint

A

The cell checks for any damage to the DNA and that the cell is ready to enter S phase- that the cell is the correct size and nutrients/growth factors are present .

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15
Q

What is the role of the G2/M checkpoint?

A

The cell checks whether the DNA has been replicated without damage and that the cell is the correct size

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16
Q

How many times can DNA be replicated during the cell cycle?

A

Once

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17
Q

What is G1 S and G2 together known as?

A

Interphase

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18
Q

What is meitosis?

A

The division of the cell into 2 genetically identical (diploid) daughter cells

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19
Q

What is meitosis used for?

A

Growth
Tissue repair
Asexual reproduction

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20
Q

What are the stages of meitosis?

A 
Prophase
Metaphase
Anaphase 
Telophase 
(Cytokinesis)
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21
Q

What happens during Prophase?

A 
Chromosomes condense and supercoil
Nuclear envelope divides
Centriole divides
New centrioles move to opposite poles
Spindle forms
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22
Q

What happens during Metaphase?

A

Sister chromatids attach to the spindle by their centromeres and line up on the equator

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23
Q

What happens during Anaphase?

A

Centromeres of the sister chromatids split

Motor proteins drag the chromatids towards the poles of the cell

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24
Q

What happens during Telophase?

A

New nuclear envelopes form around the chromosomes

Cell contains 2 nuclei

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25
What happens during cytokinesis in plant cells?
End plate forms at the equator New bits of plasma membrane form on either side of the end plate Forms 2 cells
26
What happens during cytokinesis in animal cells?
Cell inches off in the middle | Cytoplasm splits
27
What is meiosis important for?
Sexual reproduction | increases genetic variation by random fertilisation
28
What are diploid cells
cells containing 2 sets of chromosomes
29
What are haploid cells
cells containing 1 set of chromosomes
30
What is random feritlisation
random fusion of nuclei of gametes
31
Give an example of haploid cell
Gametes (egg cell)
32
What are homologous chromosomes
one chromosome comes from the mother and one comes from the father containing genes that code for the same thing - can contain different alleles
33
How many cells produced in meiosis?
4 non-identical haploid cells
34
What are the stages in meiosis?
``` Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II Telophase II ```
35
What happens during Prophase I?
``` Chromosomes condense and supercoil Centrioles divide and move to cell poles Spindle forms Nuclear envelope breaks down Crossing over occurs ```
36
What is crossing over in meiosis?
Sister chromatids wrap around eachother, joining at the chiasmata and exchange sections to shuffle alleles
37
What happens during Metaphase I?
Homologous chromosomes align on the equator and attach to spindle at their centromere
38
What happens during Anaphase I?
Homologous chromosomes are pulled apart, centromeres don't divide
39
What happens during Telophase I?
Two nuclear envelopes form, cytokinesis occurs and brief interphase
40
Do plants undergo Telophase I
No, they go straight from Anaphase I to Prophase II
41
What happens during Prophase II?
Newly formed nuclear envelopes break down (animals only) Chromosomes condense and supercoil Centrioles divide and move to cell poles Spindle forms
42
What happens during Metaphase II?
Sister chromosomes align on the equator and attach to the spindles
43
What happens during Anaphase II?
Centromeres divide, chromatids are pulled apart
44
What happens during Telophase II?
Nuclear envelope forms around the 4 haploid nuclei In animals - 2 cells divide to from 4 In plants - tetrad structure of 4 haploid cells form
45
What are the ways in which genetic diversity is created in meiosis?
Crossing over of chromosomes creates different allele combinations Mutations (in meitosis too) Dividing the chromosomes and sister chromatids in Anaphase I and II ensures that each of the four daughter cells has a different combination of alleles
46
Define differentiation
the process by which cells, tissue, and organs get specialised features, especially during embryonic development. (switching genes on and off)
47
Define specialisation
The adaptation of an organ or part to serve a special function.
48
How can cells differentiate?
Change proportions of organelles in a cell Vary shape of cell Vary the cellular contents (e.g. protein content)
49
What are tissues?
group of cells that work together to perform a common function
50
What are organs?
group of tissues that work together to perform a common function
51
What cells make up the cross section of the leaf
``` Waxy cuticle Upper epidermis Palisade mesophyll Spongy mesophyll Lower epidermis + guard cell Waxy cuticle ```
52
How does the specialisation of palisade cells allow it to complete its function?
Long cylindrical shape, packed vertically in a leaf - maximising light absorption. Large vacuole which pushes the chloroplast to the edges of the cell - short diffusion distance of CO2. It has lots of chloroplast which can be moved up or down by motor proteins on cytoskeletal threads depending on the amount of light available
53
How does the specialisation of guard cells allow it to complete its function?
Contains chloroplasts to turn light energy into ATP which move potassium ions into the guard cell so water enters by a change in water potential Cell wall is thicker in the middle of the cells than at the end so when turgid the cells bend due to the differences in thickness opening stomata, allowing gases to diffuse through
54
How does the specialisation of root hair cells allow it complete its function?
Hair like projections increase surface area to absorb more water and minerals from the soil Many carrier proteins on plasma membrane actively transport mineral ions into the cells Many mitochondria provide ATP for active transport
55
Where can stem cells be found in plants?
In meristem tissue at the root, shoot and cambium of vascular bundles
56
What are the features/structure of meristem tissue
Thin cell wall no chloroplast no large vacuole
57
Are meristem cells capable of undergoing meitosis
yes
58
How is the xylem specialised for its function
Contains lignin which strengthens the cell and makes it waterproof Lignin deposited, causes cells in the xylem tissue to die Cell walls at the ends break down allowing the xylem vessel to become a continuous column Contains no organelles for greater water flow
59
How is the phloem specilised for its function
Contains live cells Sieve tubes lose most of their organelles and develop sieve plates to allow sugar through Has companion cells because the cells are still alive but lose its organelles Companion cells have many mitochondria and provide ATP for loading sugars into sieve tubes
60
What are pluripotent cells
Cells has the potential to differentiate and specialise into any cell type that that organism can produce.
61
What are the main plant organs and what are their roles
Flower - reproduction Stem - support plant and transport things Leaf - photosynthesis Root - anchor plant in the ground, storage, absorption of water
62
Erythrocytes and neutrophils come from stem cells found where
bone marrow
63
What is the function of Erythrocytes?
Carry oxygen from lungs to respiring cells | Carry carbon dioxide from cells to the lungs
64
How are erythrocytes specialised for its function
Small - has large surface area to volume ratio Contains no organelles to maximise space for hb Has biconcave shape - allows flexibility, to fit through tiny capillaries
65
What is the function of neutrophils
Ingest invading pathogens
66
How are neutrophils specialised for its function?
large - 2x RBC contains many lysosomes enzymes in lysosomes are specialised to kill microorganisms
67
How are spematozoa (sperm cell) specialised for its function
Many mitochondria that generate ATP for movement Sperm head contain (acrosome) specialised lysosomes to break down wall of egg Small, long and thin to ease movement Tail helps to propel/move the sperm Haploid to fulfil role as gamete
68
What are the function of epithelial cells
lining of airways and intestines
69
How are epithelial cells specialised for its function
Squamous cells – flattened in shape to maximise surface area | Ciliated cells – have many cilia on cell surface - wafts mucus up the throat
70
What are the 4 main types of tissue in animals
Muscle epithelial Connective Nervous
71
What are the 2 types of epithilial tissue
Squamous | Ciliated
72
How are squamous epithelial tissue specialised for their function
Made almost entirely of closely packed cells with short cell cycles Line other tissues, vessels and surfaces Mainly for secretion and protection
73
How are ciliated epithelial tissue specialised for their function
Made of closely packed cells with short cell cycles Contain many small projections (cilia or microvilli) at the surface to increase surface area Mainly for secretion and absorption

BIOLOGY OCR (12 decks)

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