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Biology > AOS 1.4: the cell cycle > Flashcards

AOS 1.4: the cell cycle Flashcards

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1
Q

Why is cell replication needed?

A
  • maintenance and repair
  • reproduction
  • growth and development
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2
Q

Why is cell replication needed for maintenance and repair?

A

cells are constantly dying as they age or become damaged. Cell replication allows these cells to be replaced, ensuring the proper functioning of an organism

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3
Q

Why is cell replication needed for growth and development?

A

as we grow larger our cells don’t become larger. We are simply made of more cells. Therefore in order to grow we need cell replication

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4
Q

Why is cell replication needed for reproduction?

A

prokaryotic and eukaryotic cells replicate to reproduce. When they replicate, they are enlarging their population

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4
Q

What is prophase?

A

chromatin condenses around histones into distinct chromosomes (can be seen w a microscope). Simultaneously the centrioles move to opposite ends of the cell and spindle fibres begin to form. The nuclear membrane breaks down and the nucleolus disappears.

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5
Q

What is metaphase?

A

The spindle fibres fully form and attach to the centromere of each chromosome. This allows the spindle fibres to guide the chromosomes towards the equator of the cell where they line up.

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6
Q

What is anaphase?

A

The spindle fibres contract, splitting the centromere and pulling sister chromatids (become identical chromosomes) to opposite sides of the cell.

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7
Q

What is telophase?

A

The chromosomes densely pack together at either end of the cell, and new nuclear membranes form, producing two genetically identical nuclei. The spindle fibres disintegrate and the chromosomes decondense. Telophase is very similar to the reverse of prophase.

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8
Q

What is cytokinesis?

A

The cytoplasm divides and the organelles evenly distribute themselves before separating into two daughter cells

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9
Q

What is cell cycle regulation?

A

Cell cycle checkpoints are used to regulate the progression of a typical cell cycle. If errors are detected the cell can pause for repairs. However if damage is irreparable then the cell undergoes programmed cell death.
Some cells can enter a quiescent phase

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10
Q

What are the checkpoints in cell replication?

A

G1
G2
Metaphase

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11
Q

What is cytokinesis in animals?

A

cleavage furrow develops and pinches the plasma membrane into two cells

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12
Q

What is cytokinesis in plants?

A

because they have a cell wall, a cell plate first forms at the equator before separating into two cells

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13
Q

What is a centriole?

A

a cylindrical structure composed of protein which form the spindle fibres during mitosis and meiosis

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14
Q

What is chromosome condensation?

A

the shortening and thickening of chromosomes, as DNA is tightly wrapped around histone proteins

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15
Q

What is the G1 checkpoint?

A

ensures the cell is prepared for the replication of DNA

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16
Q

What is the G2 checkpoint?

A

controls mechanisms to ensure the cell is prepared for mitosis

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17
Q

What is the metaphase checkpoint?

A

cell checks the formation of the spindle fibres. If the chromosomes are lined up correctly the cell proceeds to anaphase

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18
Q

What is G0?

A

cells that are not required to replicate rest in the G0 phase. Cells in G0 are either quiescent or terminally differentiated. While quiescent cells are dormant and have the ability to re-enter the cell cycle, terminally differentiated cells remain in G0 indefinitely.

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19
Q

What is G1?

A

In the G1 phase, the cell grows by:
- increasing the volume of it’s cytosol
- synthesising proteins for DNA replication
- replicating its organelles
At the end of the G1 phase, the cell either proceeds to the S phase or exits the cell cycle and enters the G0 phase

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20
Q

What is G2?

A

The G2 phase is the final stage of interphase where the cell continues to grow and prepare itself for mitosis. The G2 phase is similar to the G1 phase in that it involves:
- increasing the volume of cytosol
- synthesising proteins in preparation for mitosis

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21
Q

What is S phase?

A

During the S phase, the cell replicates its DNA turning one chromosome into two genetically identical sister chromatids. In humans, our somatic cells are diploid meaning they contain two sets of paired chromosomes.

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22
Q

What is interphase?

A

The first and longest stage of the cell cycle. During interphase the cell synthesises the necessary DNA, proteins and organelles required for cell growth and replication. At this time the DNA exists as long chromatin threads instead of discrete chromosomes
The three substages are G1 S and G2 if further cell replication isn’t needed the cell can exit the cell cycle during the G1 phase and enter the G0 (resting) phase

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23
Q

What is mitosis?

A

The second stage of the eukaryotic cell cycle
Involves the separation of the newly replicated chromosomes into two new nuclei
PMAT

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24
Q

What does terminally differentiated mean?

A

cells that have fully specialised and no longer replicate

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25
Q

How are chromosomes regarded in cell replication?

A

While sister chromatids are held together by a centromere, the pair is regarded as a single chromosome. When the sister chromatids separate in mitosis, each chromatid is considered a single chromosome

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26
Q

What does diploid mean?

A

cells or organisms that have two sets of chromosomes (2n)

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27
Q

how many chromosomes are in humans?

A

There are 23 chromosome pairs in humans
2 x 23 = 46 chromosomes

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28
Q

What does the G1 checkpoint do?

A

verifies that the cell has grown to the correct size, has synthesised enough protein for DNA replication, checks if the DNA has been damaged during mitosis and cell growth, and checks if there are enough nutrients and oxygen (favourable conditions for mitosis)
-inspects for DNA damage

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29
Q

What does the G2 checkpoint do?

A

Confirms that DNA has correctly replicated in the S phase and the cell has enough resources for mitosis

30
Q

What does the Metaphase checkpoint do?

A

Confirms that spindle fibres have correctly attached to the centromeres of chromosomes

31
Q

What is apoptosis?

A

The natural and controlled death of cells within our body which plays an important role in our development and day to day lives. Programmed cell death

32
Q

What are the two pathways for apoptosis?

A

the mitochondrial pathway
the death receptor pathway

33
Q

What happens in the mitochondrial pathway?

A

When internal components of the cell (such as DNA) are damaged mitochondria detect this damage and release cytochrome c into the cytosol. Cytochrome c binds with cytosolic proteins to form an apoptosome, which activates caspase enzymes, initiating apoptosis.

34
Q

What happens in the death receptor pathway?

A

Death signalling molecules can be recognised by death receptor proteins on the surface of cells, and are often released by immune cells. When these molecules bind to a death receptor surface protein, caspase enzymes are activated, initiating apoptosis.

35
Q

What happens after caspase enzymes are activated?

A

Digestion of cell contents - caspases cleave intracellular proteins, which leads to the breakdown of organelles
Cell shrinks - the cell and nucleus shrink as intracellular material is broken down.
Membrane blebbing and breakage - as the cytoskeleton is digested, the structural integrity of the cell is weakened. The membrane warps and detaches from the cell in membrane enclosed vesicles known as apoptotic bodies which contain the broken down intracellular material

36
Q

What happens after apoptosis?

A

Phagocytes engulf and digest the free-floating apoptotic bodies by phagocytosis

37
Q

What is blebbing?

A

the bulging of the plasma membrane to form apoptotic bodies

38
Q

What are apoptotic bodies?

A

vesicles containing cell contents that are released from a dying cell during apoptosis and englufed by phagocytes

39
Q

How can apoptosis lead to cancer?

A

If the cell cycle is disrupted or insufficient, damaged cells can replicate exponentially, leading to the development of tumors and cancers.

40
Q

Why does apoptosis lead to tumours/cancer?

A

When the rate of apoptosis decreases too much, cell growth can increase exponentially, resulting in the formation of tumors

41
Q

How can apoptosis ‘fail’?

A

If there are any errors in the checkpoints for cell replication, the cell should repair itself or undergo apoptosis. Failure to initiate apoptosis is not always a result of errors occurring at the checkpoints (e.g. dysfunctional death receptor proteins -> inability for death signalling molecules to initiate apoptosis -> reduced rate of apoptosis)

42
Q

What are the two categories of tumours?

A

Benign
Malignant

43
Q

What is a benign tumour?

A

relatively slow growing masses of cells that are generally enclosed within a capsule which prevents the abnormal cells from separating and invading other parts of the body

44
Q

What is a malignant tumour?

A

the cells of some benign tumours can mutate futher and become malignant when they gain the ability to invade nearby tissues and/or enter the bloodstream or lymphatic system. From here they can travel to other parts of the body and grow.

45
Q

What is a tumour?

A

a mass of abnormal cells

46
Q

What tumours give cancer?

A

only malignant cells are considered to be cancerous due to their ability to migrate and invade other tissues.

47
Q

What are the characteristics of tumours?

A
  • self-sufficiency
  • antigrowth deactivation
  • increased survival
  • blood supply formation
  • tissue invasion and metastasis (only malignant)
48
Q

What is self-sufficiency?

A

Typically, cells require chemical growth signals to initiate cell replication. Tumour cells can replicate without these signals by either producing their own chemical signals, or by permanently activating cell growth and replication pathways

49
Q

What is antigrowth deactivation?

A

there are many different mechanisms present in cells to prevent cell replication when it is not needed. In tumour cells, these mechanisms can be disabled, allowing cell replication to initiate

50
Q

What is increased survival?

A

Due to mutations in the regulation of the cell cycle apoptosis no longer functions correctly in tumour cells. They are also capable of replicative immortality (theoretically allows them to divide forever) - enhancing their survival. However in practice they can still die due to limitations (e.g inability for blood vessels to form in the centre of tumours and provide necessary nutrients)

51
Q

What is blood supply formation?

A

Tumour cells can form new blood vessels when growing to maintain adequate nutrient and oxygen supply

52
Q

What is tissue invasion and metastasis?

A

Only in malignant tumours - capability to invade nearby layers of tissue and migrating to other parts of the body away from the primary tumour site, typically via the blood stream or lymphatic system (metastasis).

53
Q

What is metastasis?

A

the migration of tumour cells from the primary tumour site to distant parts of the body.

54
Q

What is exponential growth?

A

After each round of replication the number of cells present doubles.

55
Q

What is binary fission?

A

Prokaryotic replication
produces two identical copies of a cell
asexual reproduction

56
Q

What is the process of binary fission?

A
  1. The circular chromosome is uncoiled and the DNA is replicated. Plasmids also replicate.
  2. The cell elongates as it prepares to separate into two new cells and the duplicated circular chromosomes migrate to opposite ends.
  3. The cell begins to undergo cytokinesis by pinching inwards and creating a septum. because plasmids replicate independently of the circular chromosome, these will not always be evenly distributed between the two cells
  4. A new cell wall and membrane are formed down the centre of the cell
  5. Finally two new genetically identical cells are formed
57
Q

How can you remember binary fission?

A

D - DNA replication
E - elongation
S - septum formation
C - cell division

58
Q

What is a septum?

A

a dividing wall formed during binary fission

59
Q

What is a stem cell?

A

undifferentiated cells with the capability of differentiating into specialised cells

60
Q

What is a plasmid?

A

small, circular loop of DNA that is separate from a chromosome, typically found in bacteria

61
Q

what are the 3 stages in the eukaryotic cell cycle?

A

interphase — cellular growth and duplication of chromosomes
mitosis — separation of sister chromatids and the formation of two new nuclei
cytokinesis — division of the cytoplasm and formation of two daughter cells.

62
Q

What is interphase?

A

The first stage of the eukaryotic cell cycle which involves cellular growth and duplication of chromosomes. Composed of three phases: G1, S, and G2

63
Q

What is cytokinesis?

A

the division of the cytoplasm and formation of two daughter cells

64
Q

What does quiescent mean?

A

dormant cells which can re-enter the cell cycle

65
Q

What does terminally differentiated mean?

A

cells that have fully specialised and no longer replicate

66
Q

When are sister chromatids considered one chromosome?

A

While sister chromatids are held together by a centromere, the pair is regarded as a single chromosome. When the sister chromatids separate in mitosis, each chromatid is considered a single chromosome.

67
Q

What is a stem cell?

A

undifferentiated cells with the capability of differentiating into specialised (serve a unique, particular function) cells

68
Q

What does differentiation refer to?

A

the development of a stem cell into a specialised cell with a particular function

69
Q

What are the properties of stem cells?

A

Self-renewal: Stem cells have the capacity to replicate without disrupting their ability to differentiate by producing both a differentiated cell and a copy of themselves when they replicate.
Potency: Stem cells are undifferentiated cells which can give rise to differentiated cells with a specialised function.

70
Q

what does totipotent mean?

A

Stem cells that can differentiate into any cell type.

71
Q

what does pluripotent mean?

A

Stem cells that can differentiate into multiple cell types.

72
Q

what does multipotent mean?

A

Stem cells that can differentiate into a limited number of specialised cell types belonging to a specific tissue or organ.

Biology (8 decks)

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