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Biology > Cell Division and Cellular Organisation > Flashcards

Cell Division and Cellular Organisation Flashcards

1
Q

What is the cell cycle?

A

The cell cycle is a highly ordered sequence of events that takes place in a cell, resulting in its division and the formation of two genetically identical daughter cells.

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2
Q

What are the two main phases of the cell cycle?

A

Interphase and mitotic (M) phase.

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3
Q

What happens during interphase?

A

DNA is replicated and checked for errors in the nucleus.
Protein synthesis occurs in the cytoplasm.
Mitochondria grow and divide, increasing in number.
Chloroplasts grow and divide in plants.
Normal metabolic processes occur.

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4
Q

What are the three stages of interphase?

A

G₁ (first growth phase): Proteins are synthesized, organelles grow, and the cell increases in size.
S (synthesis phase): DNA is replicated in the nucleus.
G₂ (second growth phase): Energy stores increase, and DNA is checked for errors.

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5
Q

What are the two stages of the mitotic phase?

A

Mitosis: The nucleus divides.
Cytokinesis: The cytoplasm divides, forming two cells.

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6
Q

What is G₀?

A

G₀ is a phase where the cell leaves the cycle either temporarily or permanently.

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7
Q

What are the reasons a cell might enter G₀?

A

Differentiation.
DNA damage.
Senescence (ageing).
Stimulus to re-enter the cell cycle, such as immune response activation

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8
Q

Why is control of the cell cycle important?

A

To ensure cell division occurs only when DNA is error-free and chromosomes are positioned correctly, preventing uncontrolled division that could cause tumours.

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9
Q

What are the two checkpoints in the cell cycle?

A

G₁ checkpoint: Ensures DNA integrity before S phase.
G₂ checkpoint: Ensures DNA is correctly replicated before mitosis.

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10
Q

What roles do checkpoints play in the cell cycle?

A

They monitor cell processes and allow the repair of damage, ensuring division only occurs in a properly functioning cell.

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11
Q

What triggers the passing of a cell cycle checkpoint?

A

The passing of a checkpoint is triggered by enzymes called kinases, which catalyse the addition of a phosphate group to proteins (phosphorylation), changing their structure and activating them at critical points in the cell cycle.

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12
Q

How are kinases involved in cell cycle regulation?

A

Kinases are activated by binding to proteins called cyclins to form cyclin-dependent kinases (CDK) complexes, which ensure the cell progresses to the next phase of the cell cycle.

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13
Q

What is the role of CDK complexes in the cell cycle?

A

CDK complexes phosphorylate target proteins, activating key cell cycle processes such as DNA replication or chromosome alignment during mitosis.

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14
Q

How is the activity of cyclins and CDKs regulated?

A

The levels of cyclins fluctuate during the cell cycle, with specific cyclins degraded when they are no longer needed. This signals a cell to progress to the next phase.

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15
Q

What is cancer in terms of the cell cycle?

A

Cancer is a group of diseases caused by uncontrolled cell division due to mutations in genes that regulate the cell cycle. This results in the formation of tumours.

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16
Q

What are benign and malignant tumours?

A

Benign tumours: Grow slowly and are usually enclosed, not spreading.
Malignant tumours: Grow rapidly and invade other tissues, leading to metastasis.

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17
Q

What causes tumours to develop?

A

Tumours develop due to mutations in genes that regulate cell division, such as proto-oncogenes (stimulate cell division) and tumour suppressor genes (inhibit cell division).

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18
Q

What happens if a checkpoint is skipped or ignored in the cell cycle?

A

If a checkpoint is skipped, the cell can divide uncontrollably, leading to the formation of tumours and possibly cancer.

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19
Q

What is the metaphase checkpoint?

A

This checkpoint ensures that all chromosomes are attached to spindle fibres and aligned at the metaphase plate. Mitosis cannot proceed without passing this checkpoint.

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20
Q

Why is the regulation of the cell cycle crucial?

A

Proper regulation ensures cells divide only when needed, preventing errors that can lead to cancer or uncontrolled cell growth.

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21
Q

What is mitosis?

A

Mitosis is the process of nuclear division that produces two genetically identical daughter cells, each with the same DNA as the parent cell.

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22
Q

Why is mitosis important?

A

Ensures genetic consistency in cells.
Facilitates growth, repair, and replacement of tissues in multicellular organisms.
Necessary for asexual reproduction in some organisms.

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23
Q

What happens to chromosomes during mitosis?

A

Chromosomes, replicated during interphase, are separated into two identical chromatids. Each chromatid is distributed equally into the two new daughter cells.

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24
Q

What are the four main stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

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25
Q

What happens during prophase?

A

Chromatin condenses into chromosomes.
The nuclear envelope breaks down.
Spindle fibers attach to chromosomes at their centromeres.
Centrioles (in animal cells) migrate to opposite poles.
Chromosomes start moving to the cell’s centre.

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26
Q

What happens during metaphase?

A

Chromosomes align at the metaphase plate (cell centre), with spindle fibres attaching to their centromeres to ensure proper separation.

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27
Q

How do prokaryotic organisms divide?

A

Prokaryotes divide by binary fission, a simpler form of reproduction as they lack a nucleus.

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28
Q

How is chromosomal DNA prepared for division?

A

Each chromosome is replicated during interphase to form two identical sister chromatids connected by a centromere.

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29
Q

What is the metaphase plate?

A

The metaphase plate is the central region of the cell where chromosomes align during metaphase for equal distribution.

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30
Q

What is the role of spindle fibres in mitosis?

A

Spindle fibres connect to centromeres and guide the movement of chromosomes during cell division.

31
Q

What happens during anaphase in cell division?

A

The centromeres holding the chromatids together divide, and sister chromatids are pulled to opposite poles by shortening spindle fibres.

32
Q

What characteristic shape is formed by chromatids during anaphase?

A

A “V” shape, caused by chromatids being dragged by their centromeres.

33
Q

What marks the beginning of telophase in cell division?

A

Chromatids reach the poles, chromosomes decondense, the nuclear envelope reforms, and cytokinesis begins.

34
Q

What is cytokinesis?

A

The actual division of the cell into two separate cells following mitosis.

35
Q

How does cytokinesis occur in animal cells?

A

A cleavage furrow forms and the cell membrane is pulled inward by the cytoskeleton until it fuses, dividing the cell into two.

36
Q

Why is a cleavage furrow not possible in plant cells?

A

Plant cells have rigid walls that prevent inward pinching during cytokinesis.

37
Q

How do plant cells undergo cytokinesis?

A

Vesicles from the Golgi apparatus assemble at the cell equator, forming a cell plate that develops into a new cell wall and membrane.

38
Q

What are spindle fibres, and what role do they play in cell division?

A

Spindle fibres are structures that pull chromatids to opposite poles during anaphase.

39
Q

Summarise the main difference between cytokinesis in animal and plant cells.

A

Animal cells divide by forming a cleavage furrow, while plant cells divide by forming a cell plate.

40
Q

Why are plant root tips often used for studying mitosis?

A

They are regions of rapid cell division, making them ideal for observing mitosis.

41
Q

What is the function of vesicles during cytokinesis in plant cells?

A

Vesicles carry materials to form the new cell wall and membrane between dividing cells.

42
Q

What role does the cytoskeleton play during cytokinesis in animal cells?

A

It pulls the membrane inward to create the cleavage furrow.

43
Q

What is the main purpose of meiosis?

A

To produce gametes with half the chromosome number (haploid), ensuring genetic variation through reduction division.

44
Q

How do homologous chromosomes contribute to meiosis?

A

Each pair of homologous chromosomes contains one chromosome from each parent, and they pair up during meiosis for crossing over and independent assortment.

45
Q

What happens during Prophase I of meiosis?

A

Chromosomes condense, the nuclear envelope disintegrates, homologous chromosomes pair up, and crossing over occurs.

46
Q

What is crossing over?

A

The exchange of genetic material between homologous chromosomes, resulting in genetic variation.

47
Q

Describe the process of independent assortment.

A

Homologous chromosome pairs align randomly at the metaphase plate in Metaphase I, leading to different combinations of alleles in gametes.

48
Q

What occurs during Metaphase I?

A

Homologous chromosome pairs align randomly along the equator, facilitating independent assortment.

49
Q

How does Anaphase I differ from mitosis?

A

In Anaphase I, homologous chromosomes are pulled to opposite poles, while in mitosis, sister chromatids are separated.

50
Q

What happens in Telophase I?

A

The cell divides into two haploid cells, each containing half the chromosome number of the original diploid cell.

51
Q

What distinguishes Meiosis II from Meiosis I?

A

Meiosis II separates sister chromatids, similar to mitosis, producing four haploid cells.

52
Q

What is the result of meiosis?

A

Four genetically varied haploid daughter cells.

53
Q

What is the role of crossing over and independent assortment in meiosis?

A

They generate genetic variation by producing new combinations of alleles.

54
Q

What are the levels of organisation in multicellular organisms?

A

Cells → Tissues → Organs → Organ systems → Organism.

55
Q

What does it mean for a cell to be specialised?

A

Specialised cells have specific structures and functions to perform particular roles in the organism.

56
Q

Give an example of a specialised cell and its function.

A

Red blood cells transport oxygen using haemoglobin and have a biconcave shape to increase surface area for gas exchange.

57
Q

Why is cell differentiation important in multicellular organisms?

A

It allows cells to become specialised to carry out specific functions efficiently.

58
Q

What are neutrophils, and what is their role?

A

Neutrophils are a type of white blood cell with a multilobed nucleus that engulfs and destroys pathogens during the immune response.

59
Q

What is the function of sperm cells?

A

To deliver genetic information to the female gamete for fertilisation.

60
Q

What adaptations do sperm cells have?

A

A tail for movement, mitochondria for energy, an acrosome with enzymes to penetrate the egg, and a haploid nucleus.

61
Q

What is the role of palisade cells in plants?

A

They contain chloroplasts for photosynthesis, absorbing large amounts of light.

62
Q

How are root hair cells adapted to their function?

A

They have long extensions to increase surface area for water and mineral uptake.

63
Q

What are guard cells, and what is their role?

A

They control the opening and closing of stomata, regulating water loss and gas exchange in plants.

64
Q

Name the four main categories of animal tissues.

A

Nervous tissue, epithelial tissue, muscle tissue, and connective tissue.

65
Q

What is squamous epithelium?

A

A single layer of flat cells adapted for rapid diffusion, found in the lungs and blood vessels.

66
Q

Where is ciliated epithelium found, and what is its function?

A

Found in the trachea and oviducts; it helps move mucus and eggs with its cilia.

67
Q

What is the function of cartilage tissue?

A

Provides flexible support and reduces friction in joints.

68
Q

What is the function of muscle tissue?

A

Allows movement by contracting and relaxing.

69
Q

What are the two main types of plant tissues?

A

Epidermis tissue and vascular tissue.

70
Q

What is the role of xylem tissue?

A

Transports water and minerals throughout the plant.

71
Q

What is the role of phloem tissue?

A

Transports organic nutrients, like sugars, from sources to sinks in plants.

72
Q

What is an organ and Give an example of an organ system in animals?

A

A collection of tissues adapted to perform a specific function.
The digestive system, which processes food, absorbs nutrients, and eliminates waste.

73
Q

Describe the relationship between tissues and organs.

A

Tissues form organs, and organs work together in systems to perform functions.

Biology (8 decks)

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