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Biology > 3.2.1.4 All Cells Arise From Other Cells > Flashcards

3.2.1.4 All Cells Arise From Other Cells Flashcards

1
Q

What is the cell cycle?

A

The cell cycle is the regulated sequence of events that occurs between one cell division and the next.

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2
Q

What are the three stages of the cell cycle?

A

Stage 1 - interphase
Stage 2 - mitosis
Stage 3 - cytokinesis

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3
Q

What are cyclins?

A

Chemical signals that trigger the movement from one stage of the cell cycle to another.

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4
Q

What are the three phases in the interphase?

A

G1 phase
S phase
G2 phase

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5
Q

What happens in the G1 phase?

A

Organelles are replicated
The size and mass of the cell increases
The cell continues to carry out its usual functions
Synthesis of proteins that produce organelles

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6
Q

What happens in the s phase?

A

The DNA in the nucleus replicates
Each chromosome consists of two identical sister chromatids
The DNA replicates by semi-conservative replication

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7
Q

What is a chromatid?

A

The name for each individual unit in a paired chromosome

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8
Q

What is a centromere?

A

The centre point which joins two chromatids to form a chromosome.

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9
Q

What happens in the G2 phase?

A

The cell increases energy stores needed for mitosis
The size of the cell continues to increase
The newly synthesised DNA is checked for errors and repaired

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10
Q

What is mitosis?

A

The process of nuclear division by which two genetically identical daughter nuclei are produced, that are also genetically identical to the parent cell nucleus.

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11
Q

Why does mitosis occur?

A

For the growth of new cells
For the repair of damaged tissues
For asexual reproduction

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12
Q

What are the four stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

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13
Q

What happens in the prophase?

A

Chromosomes condense and become visible
The centrioles separate and move to opposite poles of the cell
The nucleolus and nuclear envelope dissapears

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14
Q

What happens in the metaphase?

A

The chromosomes line up along the equator of the cell
The spindle fibres are released from centrioles attached to the centromeres of the chromosomes

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15
Q

What happens in the anaphase?

A

Spindle fibres pull on chromosomes, and they separate into chromatids at the centromere
Sister chromatids are pulled to opposite poles of the nucleus
They form v shapes as the separation occurs at the centromere, so the ends drag behind.

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16
Q

What happens in the telophase?

A

The chromosomes reach the poles and become indistinct
The nucleolus and nuclear envelope starts to reform
The spindle fibres disintegrate

17
Q

What happens in cytokinesis?

A

The cytoplasm and cell membrane divide
They form two genetically identical daughter cells
Both cells have a nucleus and sub-cellular structures.

18
Q

How do you calculate the length of stages of mitosis?

A

(Number of cells in the stage / number of cells in all stages) x length of the cell cycle in minutes

19
Q

What is the mitotic index?

A

The proportion of cells in a tissue sample that are undergoing mitosis

20
Q

How do you calculate the mitotic index?

A

Number of cells with visible chromosomes / total number of cells observed

21
Q

What is cancer?

A

A disease caused by the mutation of the genes that regulate mitosis, therefore cells divide uncontrollably. This uncontrolled cell division leads to the formation of a tumour.

22
Q

What are the characteristics of a benign tumour?

A

Enclosed in a membrane
Slow growing
Does not invade other tissues by metastasis
Non-cancerous
Impact is localised

23
Q

What are the characteristics of a malignant tumour?

A

Grow rapidly
Unspecialised cells
Invade surrounding tissues and organs
Forms secondary tumours by metastasis
Can develop its own blood supply

24
Q

Define metastasis

A

When a malignant tumour spreads to form a secondary tumour

25
Q

How does cancer form?

A

Due to a gene mutation in either the tumour suppressor gene or the oncogene.

26
Q

How can tumour suppressor genes cause cancer?

A

They can mutate to become non-functional so cell division continues to occur.

27
Q

How can oncogenes cause cancer?

A

Oncogenes are the mutated version of proto-oncogenes which results in permanent cell division.

28
Q

What is a carcinogen and what are examples?

A

Any factor that may cause the development of cancer:
Uv light
Tobacco smoke
Genetic disorders
Alcohol
Obesity

29
Q

Describe the process of cancer forming and spreading?

A

A mutation occurs which leads to an abnormal group of cells forming within a tissue due to uncontrolled cell division.
Enlarging tumour develops its own blood and lymphatic vessels.
Tumour cells squeeze into the body’s own blood and lymphatic vessels.
Tumour cells either:
Form secondary tumours in lymph nodes throughout the body.
Circulate in the blood and adhere to blood vessel walls, squeezing through to new tissues to form secondary tumours.

30
Q

What is the purpose of cancer treatments?

A

To control the rate of cell division to stop the tumour from developing.
Eg. By stopping DNA replication or mitosis.

31
Q

What is the process by which prokaryotic cells divide?

A

Binary fission

32
Q

Describe the process of binary fission?

A

The circular DNA unwinds and duplicates. The plasmids also replicate.
The cytoplasm elongates to separate the two sets of DNA.
The cell membrane and cytoplasm begin to split into two.
A new cell wall forms between the two DNA molecules which splits the cytoplasm into two.
Two genetically identical daughter cells are produced, with one copy each of the circular DNA, and a variable number of plasmids.

33
Q

What is the equation to calculate bacterial numbers?

A

Number of cells in generation n = initial number of cells x 2^number of generations

This is because bacterial cells multiply exponentially

34
Q

How do viruses reproduce?

A

Viruses are non-living so they cannot reproduce alone.
Therefore, they invade host cells and use them to replicate themselves to produce new viral proteins.

35
Q

Describe the process by which viral cells reproduce

A

Attachment proteins on the surface of a virus bind to complementary receptor proteins on the surface of the host cell. (Viruses have different attachment proteins so target many different types of cell).
The virus injects its nucleic acids into the host cell.
The host cell then uses its ribosomes and replicates the nucleic acids from the virus to produce many viral particles.
The many viral particles are released from the host cell by a process called lytic release.
Once they burst through the cell, the host cell dies due to a hole in its cell membrane.

Biology (17 decks)

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