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AS Biology > Module 2.6 - Cell division and Cellular organisation > Flashcards

Module 2.6 - Cell division and Cellular organisation Flashcards

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1
Q

What are the 3 stages involved in interphase?

A

G1, S and G2.

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2
Q

What happens in the G1 phase of interphase?

A

Cell grows and new organelles and proteins are made.

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3
Q

What does the S stand for in interphase and what happens?

A

Synthesis - Cell replicates its DNA, ready to divide by mitosis.

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4
Q

What happens in Gap Phase 2 of interphase?

A

Cell keeps growing and proteins needed for cell division are made.

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5
Q

What happens at the G1 checkpoint?

A

The cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering S-phase.

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6
Q

What happens at the G2 checkpoint?

A

The cell checks whether all the DNA has been replicated without any damage. If it has, the cell can enter mitosis.

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7
Q

M phase is the smallest part of the cell cycle and what does it involve?

A

Mitosis and cytokinesis.

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8
Q

Why is the cell cycle regulated by checkpoints?

A

Checkpoints occur at key points during the cycle to make sure it’s okay for the process to continue.

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9
Q

Why is mitosis needed?

A

> Needed for the growth of multicellular organisms and for repairing damaged tissues.
A method of asexual production for some plants, animals and fungi.

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10
Q

When does interphase occur in the cell cycle and what is it’s overall purpose?

A

Interphase comes before mitosis in the cell cycle and it’s where cells grow and replicate their DNA ready for division.

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11
Q

Describe what happens in interphase to prepare for mitosis?

A

The cell carries out normal functions, but also to prepares to divide. The cell’s DNA is unravelled and replicated, to double it’s genetic content. The organelles are also replicated so it has spare ones, and its ATP content is increased (ATP provides the energy needed for cell division).

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12
Q

What happens at the prophase stage in mitosis?

A

> The chromosomes condense, getting shorter and fatter.
Tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle.
The nuclear envelope breaks down and chromosomes lie free in the cytoplasm.

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13
Q

What are the separate strands of chromosomes called?

A

Chromatid.

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14
Q

The chromosomes are made of 2 strands joined in the middle, what is this called?

A

A centromere.

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15
Q

What happens at metaphase in mitosis?

A

> The chromosomes line up along the middle of the cell and become attached to the spindle by their centromere.
At the metaphase checkpoint, the cell checks that all the chromosomes are attached to the spindle before mitosis can continue.

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16
Q

How many chromatids do each chromosome have?

A

2

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17
Q

What happens at anaphase in mitosis?

A

> The centromeres divide, separating each pair of sister chromatids.
The spindles contract, pulling chromatids to opposite ends of the cell, centromere first.

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18
Q

What happens at the telophase stage of mitosis?

A

> The chromatids reach the opposite poles on the spindle. They uncoil and become long and thin again. They’re now called chromosomes again.
A nuclear envelope forms around each group of chromosomes, so there are now 2 nuclei.

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19
Q

What happens in the cytokinesis stage of mitosis?

A

> The cytoplasm divides.

>In animal cells, a cleavage furrow forms to divide the cell membrane.

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20
Q

What is the end-product of mitosis?

A

There are now 2 daughter cells that are genetically identical to the original cell and to each other.

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21
Q

When does cytokinesis occur in mitosis?

A

Cytokinesis usually begins in anaphase and ends in telophase. It’s a separate process to mitosis.

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22
Q

What happens in sexual production?

A

2 gametes (an egg and a sperm) join together at fertilisation to form a zygote. The zygote then divides and develops into a new organism.

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23
Q

What are cells with half the normal number of chromosomes called?

A

Haploid cells.

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24
Q

Why are cells formed in meiosis all genetically different?

A

Each new cell ends up with a different combination of chromosomes.

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25
Q

Meiosis involves how many divisions?

A

2 - Meiosis 1 and meiosis 2.

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26
Q

Why is Meiosis 1 described as a reduction division?

A

Cells that divide by meiosis have the full number of chromosomes to start with, but the cells that are formed from meiosis have half the number.

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27
Q

Describe what happens in prophase in meiosis 1?

A

> The chromosomes condense, getting shorter and fatter.
Then the chromosomes arrange themselves into homologous pairs and crossing-over occurs.
Just like in mitosis, centrioles start moving to opposite ends of the cell, forming the spindle fibres. The nuclear envelope breaks down.

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28
Q

Describe what happens in Metaphase 1 in Meiosis 1?

A

The homologous pairs line up across the centre of the cell and attach to the spindle fibres by their centrometres.

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29
Q

Describe what happens in Anaphase 1 in Meiosis 1?

A

The spindles contract, separating the homologous pairs - one chromosome goes to each end of the cell.

30
Q

Describe what happens in Telophase 1 in Meiosis 1?

A

A nuclear envelope forms around each group of chromosomes.

31
Q

What happens after meiosis 1 and before meiosis 2?

A

Cytokinesis (division of the cytoplasm) occurs and 2 haploid daughter cells are produced.

32
Q

The stages of meiosis are a lot like those in mitosis. What happens in Prophase 2?

A

The nuclear envelope disappears.

33
Q

What happens in Metaphase 2 in meiosis 2?

A

Chromosomes line up at the equator.

34
Q

What happens at Anaphase 2 in meiosis 2?

A

The pairs of sister chromatids are separated, pulled apart by spindles.

35
Q

What happens at Telophase 2 in meiosis 2?

A

Each new daughter cell inherits 1 chromatid from each chromosome. 4 (genetically different) haploid daughter cells are produced - these are gametes. Nuclear envelope reform and cells undergo cytokinesis.

36
Q

Describe what happens in prophase 1 when the chromatids cross over?

A

Homologous pairs of chromosomes come together and pair up. The chromatids twist around each other and bits of chromatids swap over. The chromatids still contain the same genes but now have a different combination of alleles.

37
Q

What are the two main events in meiosis that lead to genetic variation?

A

Crossing over of chromatids and independent assortment of chromosomes.

38
Q

What is each homologous pair of chromosomes in your cells made up of?

A

1 chromosome from your mother (maternal) and one chromosome from your father (paternal).

39
Q

How does independent assortment of chromosomes occur?

A

> When the homologous pairs line up in metaphase 1 and are separated in anaphase 1, it’s completely random which chromosomes from each pair ends up in which daughter cell.
So the 4 daughter cells produced by meiosis have completely different combinations of those maternal and paternal chromosomes.
This ‘shuffling’ of chromosomes leads to genetic variation in any potential offspring.

40
Q

Stem cells are unspecialised cells, what does this mean?

A

They can develop into different types of cell.

41
Q

What are stem cells used for in animal cells?

A

Used to replace damaged cells such as to make new skin or blood cells.

42
Q

What are stem cells used for in plant cells?

A

Plants are always growing, so stem cells are needed to make new shoots and roots throughout their lives. Stem cells in plants can differentiate into various plant tissues including xylem and phloem.

43
Q

In the human body where can stem cells be found and what are they used for?

A

Bone marrow, adult stem cells divide and differentiate to replace worn out blood cells - erythrocytes and neutrophils.

44
Q

In a plant where can stem cells be found and what are they used for?

A

Meristems (parts of the plant where growth can take place) - in the root and stem, stem cells of the vascular cambium divide and differentiate to become xylem vessels and phloem sieve tubes.

45
Q

Since stem cells can be used to replace damaged tissue, what are 2 diseases that scientists hope to cure using stem cells and why?

A

> Alzheimers - nerve cells in the brain die in increasing numbers, results in severe memory loss. Use stem cells to regrow healthy nerve cells.
Parkinson’s - Suffer from tremors they can’t control because the loss of a nerve cell in the brain that releases dopamine, needed to control movement. Transplanted stem cells may help to regenerate the dopamine-producing cells.

46
Q

What is a neutrophil?

A

A type of white blood cell that defends the body against disease/fights infection.

47
Q

How does the structure of a neutrophil aid it’s function?

A

Their flexible shape allows them to engulf foreign particles or pathogens. The many lysosomes in their cytoplasm contain digestive enzymes to break down the engulfed particles.

48
Q

What is a erythrocyte?

A

It’s a red blood cell, carries oxygen in the blood.

49
Q

How does the structure of a erythrocyte aid it’s function?

A

The biconcave disc shape provides a large surface area for gas exchange. They have no nucleus so there’s more room for haemoglobin, the protein that carries oxygen.

50
Q

How does the structure of a sperm cell aid it’s function?

A

> Has a flagellum/undulipodium (tail) so they can swim to the egg (female sex cell).
They also have lots of mitochondria to provide the energy to swim.
The acrosome contains digestive enzymes to enable the sperm to penetrate the surface of the egg.
Small, long and thin, moves easily.
Head of the sperm contains the haploid male gamete nucleus and little cytoplasm.

51
Q

What do epithelial cells do?

A

Epithelium is lining tissue and covers the surface of organs.

52
Q

How does the structure of epithelial cells aid it’s function?

A

> The cells are joined by interlinking cell membranes. >Ciliated epithelia have cilia that beat to move particles away.
Squamous epithelia (flattened/thin in shape) are very thin and allow efficient diffusion of gases.

53
Q

What do palisade mesophyll cells do?

A

They do most of the photosynthesis.

54
Q

How does the structure of palisade cells aid it’s function?

A

> Contain many chloroplasts, so they can absorb a lot of sunlight.
The walls are thin, so carbon dioxide can easily diffuse into the cell.
Contain cytoskeleton threads and motor proteins to move the chloroplasts nearer to the upper surface of the cell.

55
Q

What do root hair cells do?

A

They absorb water and mineral ions from the soil.

56
Q

How does the structure of root hair cells aid it’s function?

A

> Large surface area for absorption.
Thin, permeable cell wall, for entry of water and ions.
The cytoplasm contains extra mitochondria to provide the energy needed for active transport.

57
Q

What do guard cells do?

A

Important for gas exchange in photosynthesis.

58
Q

How does the structure of guard cells aid it’s function?

A

> Guard cells are found in pairs, with a gap between them to form a stoma, this is one of the tiny pores in the surface of the leaf used for gas exchange.
In the light, guard cells take up water and become turgid. The thin outer walls and thickened inner walls force them to bend outwards, opening the stomata.

59
Q

What is squamous epithelium tissue?

A

A single layer of flat cells lining a surface.

60
Q

Where is squamous epithelium tissue found in the body?

A

Found in many places, including the alveoli in the lungs.

61
Q

What is ciliated epithelium tissue?

A

A layer of cells covered in cilia.

62
Q

Where is ciliated epithelium tissue found in the body?

A

Found on surfaces where things need to be moved - in the trachea for instance, where the cilia waft mucus along.

63
Q

What is muscle tissue?

A

Made up of bundles of elongated cells called muscle fibres.

64
Q

Where is muscle tissue found in the body?

A

There are 3 different types of muscle tissue:
>Smooth (e.g. found lining the stomach wall).
>Cardiac (found in the heart).
>Skeletal (which you use to move).
They’re all slightly different in structure.

65
Q

What is cartilage?

A

A type of connective tissue found in the joints.

66
Q

Where is cartilage found in the body?

A

> It also shapes and supports the ears, nose and windpipe.

>It’s formed when cells called chondroblasts secrete an extracellular matrix which they become trapped inside

67
Q

What are the two jobs of xylem tissue?

A

> Transports water around the plant.

>Supports the plant.

68
Q

Describe the structure of xylem?

A

It contains hollow xylem vessels, which are dead, and living parenchyma cells.

69
Q

What is the role of phloem?

A

Transports sugar around the plant.

70
Q

What is the structure of phloem tissue?

A

It’s arranged in tubes and is made up of sieve cells, companion cells, and some ordinary plant cells. Each sieve cell has end walls with holes in them, so that sap can move easily through them. These end walls are called sieve plates.

71
Q

What are the different types of tissue the organ, lungs are made up of?

A

They contain squamous epithelial cells (alveoli), ciliated epithelial tissue (in the bronchi). They also have elastic connective tissue and vascular tissue (in the blood vessels).

72
Q

What are the different types of tissue that leaves are made up of?

A

They contain palisade tissue for photosynthesis, as well as epidermal tissue (to prevent water loss from the leaf), and xylem and phloem tissues in the vein.

AS Biology (12 decks)

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