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A-level Biology > 8A - Stem cells > Flashcards

8A - Stem cells Flashcards

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1
Q

How many types of cells can totipotent stem cells mature into?

A

All types.

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2
Q

What are stem cells?

A

Unspecialised cells that can develop into other types of cell.

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3
Q

What do stem cells divide to become?

A

New cells, which then become specialised.

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4
Q

What are stem cells that can mature (develop) into any type of body cell called?

A

Totipotent cells.

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5
Q

Where are totipotent stem cells only present?

A

In mammals in the first few cell divisions of an embryo.

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6
Q

Why are embryonic stem cells pluripotent?

A

Because they can specialise into any cell in the body, but have lost the ability to become the cells that make up the placenta.

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7
Q

How many types of cells can pluripotent stem cells mature into?

A

Almost all types.

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8
Q

How many types of cells can multipotent stem cells mature into?

A

A few (multiple) types.

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9
Q

How many types of cells can unipotent stem cells mature into?

A

One type.

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10
Q

What are the four types of stem cells?

A

Totipotent, pluripotent, multipotent and unipotent stem cells.

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11
Q

What type of stem cells are embryonic stem cells?

A

Pluripotent.

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12
Q

Where are embryonic stem cells found?

A

In blastocyst (taken from the inner cell mass).

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13
Q

How are embryonic stem cells made fit for use?

A

Cultured in the lan to grow more cells (in a fluid of nutrients).

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14
Q

What are adult stem cells also called?

A

Tissue stem cells.

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15
Q

What are tissue stem cells?

A

Adult stem cells.

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16
Q

Where are adult stem cells found?

A

In various tissues around the boy (surface of eye, brain, breast, intestines, guts, bone marrow, testicles, muscles).

Blood stem cells found in bone marrow can only differentiate into types of blood cells (e.g. RBC, WBC platelets).

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17
Q

What types of cell can blood stem cells found in bone marrow differentiate into?

A

Types of blood cell only - WBC, RBC, platelets, etc.

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18
Q

What type of stem cells are adult stem cells?

A

Multipotent.

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19
Q

`Where are umbilical cord blood stem cells found?

A

In the umbilical cord.

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20
Q

What type of stem cells are umbilical cord blood stem cells?

A

Multipotent.

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21
Q

What type of stem cells are placental stem cells?

A

Multipotent.

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22
Q

Where are placental stem cells found?

A

In the placenta.

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23
Q

What can placental stem cells develop into?

A

Specific types of cell.

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24
Q

Where are totipotent stem cells found?

A

In early embryo (zygotes).

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25
Q

What type of stem cells are found in early embryos?

A

Totipotent.

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26
Q

What can totipotent stem cells do?

A

Mature into any cell types.

Translate only part of their DNA, resulting in cell specialisation (can also divide to form pluripotent stem cells).

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27
Q

Which stem cells can divide to form pluripotent stem cells?

A

Totipotent stem cells.

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28
Q

What maintains the stem cells pool?

A

Self-renewal (copying).

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29
Q

Potency

A

A measure of how many types of specialised cell a stem cell can make.

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30
Q

Unitpotent

A

Can make one type of cell derived for multipotent stem cells.

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31
Q

Where are unipotent stem cells derived from?

A

Multipotent stem cells.

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32
Q

Why do stem cells become specialised?

A

Because during their development, they only transcribe and translate part of their DNA.

33
Q

Explain how stem cells become specialised because they only transcribe and translate part of their DNA

A

1) Stem cells all contain the same genes - but during development not all of them are transcribed and translated (expressed).
2) Under the right conditions, some genes are expressed and others are switched off.
3) mRNA is only transcribed from specific genes.
4) The mRNA from these genes is then translated into proteins.
5) These proteins modify the cell - they determine the cell structure and control cell processes (including the expression of more genes, which produces more proteins).
6) Changes to the cell produced by these proteins cause the cell to become specialised. These changes are difficult to reverse, so once a cells has specialised it stays specialised.

34
Q

Explain how stem cells become specialised into red blood cells

A

1) RBCs are produced from a type of stem cell in the bone marrow. They contain lots of haemoglobin and have no nucleus (to make room for more haemoglobin).
2) The stem cell produces a new cell in which the genes for Hb production are expressed. Other genes, such as those involved in removing the nucleus, are expressed too. Many other genes are not expressed (switched off), resulting in a specialised RBC.

35
Q

What is transcription?

A

When DNA is copied into mRNA.

36
Q

What is translation?

A

When proteins are produced using the code in mRNA.

37
Q

What are cardiomyocytes?

A

Heart muscle cells that make up a lot of the tissue in our hearts.

38
Q

What is known about cardiomyocytes?

A
  • It is thought that, in mammals, they can’t divide to replicate themselves.
  • This meant that for ages, everyone thought that we weren’t able to regenerate our own heart cells at all. This is a major problem if the heart becomes damaged or the cells became worn out by age. Recent research however, has suggested that our hearts do have some regenerative capability.
  • Some scientists now think that old or damage cardiomyocytes can be replaced by new cardiomyocytes derived from a small supply of unipotent stem cells in the heart.
  • Some researchers think that this process could be constantly occurring, but haven’t yet agreed in how quickly it happens.
  • Some believe that it’s a really slow process and that it’s possible that some cardiomyocytes are never replaces throughout a person’s entire lifetime.
  • Others think that it’s occurring more quickly, so that every cardiomyocyte in the heart is replaced several times in a lifetime.
39
Q

What type of stem cells can cardiomyocytes be made by?

A

Unipotent stem cells.

40
Q

What do some stem cell therapies already exist for?

A

Some diseases affecting the blood and immune system.

41
Q

How do bone marrow transplants work?

A

Bone marrow transplants can be used to replace faulty bone marrow in patients that produce abnormal blood cells. The stem cells in the transplanted bone marrow divide and specialise to produce healthy blood cells.

42
Q

What have bone marrow transplants been used successfully to treat?

A

Leukemia and lymphoma.

Some genetic disorders, such as sickle-cell anaemia and severe combined immunodeficiency (SCID).

43
Q

What is leukemia?

A

A cancer of the blood or bone marrow.

44
Q

What is lymphoma?

A

A cancer of the lymphatic system.

45
Q

What is severe combined immunodeficiency (SCID)?

A

A genetic disorder that affects the immune system.

46
Q

What do people with severe combined immunodeficiency (SCID) have?

A

A poorly functioning immune system.

47
Q

Why do people with severe combined immunodeficiency (SCID) have poorly functioning immune systems?

A

Because their white blood cells (made in the bone marrow from stem cells) are defective. This means they can’t defend the body against infections by identifying and destroying microorganisms. So SCID sufferers are extremely susceptible to infections.

48
Q

What are SCID sufferers extremely susceptible to?

A

Infections.

49
Q

How can SCID be treated?

A

With a bone marrow transplant.

50
Q

How can SCID be treated with a bond marrow transplant?

A

A bone marrow transplant replaces the faulty bone marrow with donor bone marrow that contains stem cells without the faulty genes that cause SCID. These then differentiate to produce functional WBCs. These cells can identify and destroy invading pathogens so the immune system functions properly.

51
Q

Besides leukemia, lymphoma and some genetic disorders, what might stem cells be used to treat?

A
  • Spinal cord injuries.
  • Heart disease and damage caused by heart attacks.
  • Bladder conditions.
  • Respiratory diseases.
  • Organ transplants.
52
Q

How might stem cells be used to treat spinal cord injuries?

A

Used to replace damaged nerve tissue.

53
Q

How might stem cells be used to treat heart disease and damage caused by heart attacks?

A

Used to replace damaged heart tissue.

54
Q

How might stem cells be used to treat bladder conditions?

A

Used to grow whole bladders, which are them implanted in patients to replace diseased ones.

55
Q

How might stem cells be used to treat respiratory diseases?

A

Donated windpipes can be stripped down to their simple collagen structure and then covered with tissue generated by stem cells. This can the be transplanted into patients.

56
Q

How can stem cells be used in organ transplants?

A

Organs could be grown from stem cells to provide new organs for people on donor waiting lists.

57
Q

What is the issue with using stem cells for replacement organs?

A

Issues of rejection if the right type of tissue is developed - although, there is tissue typing or use of drugs to avoid rejection.

58
Q

What are the benefits to using stem cells in medicine?

A
  • Could save many lives (many people waiting for organ transplants die before a organ donor becomes available).
  • Could improve the quality of life for many people (used to replace damaged cells in the eyes of people who are blind).

Could help people suffering from diseases caused by faulty cells:

  • Parkinson’s Disease; replace faulty brain cells
  • Diabetes; replace insulin producing tissue in the pancreas.
  • Damaged nerves; replace spinal nerves so that limbs can work again.
  • Organs for transplant; replace organs that no longer work, such as livers, kidneys, hearts, etc.
59
Q

What are the 3 main sources of human stem cells?

A

1) Adult stem cells.
2) Embryonic stem cells.
3) Induced pluripotent stem cells (iPS Cells).

60
Q

Where are adult stem cells found?

A

Brain, liver, skin, bone marrow (body tissues of an adult).

61
Q

How are adult stem cells obtained?

A

In a relatively simple operation - with very little risk involved, but quite a lot of discomfort.

62
Q

What is the downside to using adult stem cells?

A

They aren’t as flexible as embryonic stem cells - they can only specialise into a limited range of cells, not all body cell types (they’re multipotent).

63
Q

What type of stem cells are adult stem cells?

A

Multipotent.

64
Q

What are some adult stem cells already used to treat?

A

Some cancers.

65
Q

Explain how embryonic stem cells obtained?

A
  • Obtained from embryos at an early stage of development.
  • Embryos are created in a laboratory using in vitro fertilisation (IVF) - egg cells are fertilised by sperm outside of the womb.
  • Once the embryos are approximately 4-5 days old (at the 8 cell stage), stem cells are removed from the inner blastocyst and the rest if the embryo is destroyed.
  • Embryonic stem cells can divide an unlimited number of times and develop into all types of body cells (they’re pluripotent).
66
Q

What are embryonic stem cells obtained from?

A

From embryos at an early stage of development.

67
Q

How many times can embryonic stem cells divide?

A

Unlimited.

68
Q

What type of stem cells are embryonic stem cells?

A

Pluripotent.

69
Q

How are induced pluripotent stem cells (iPS cells) made?

A
  • Created by scientists in the lab.
  • Process involved ‘reprogramming’ specialised adult body cells so that they become pluripotent.
  • The adult cells are made to express a series of transcription factors that are normally associated with pluripotent stem cells. The transcription factors cause the adult body cells to express genes that are associated with pluripotency.
  • One way these transcription factors can be introduced to the adult cells is by infecting them with a specially modified virus. The virus has the genes coding for the transcription factors within its DNA. When the virus infects the adult cell, these genes are passed into the adult cell’s DNA, meaning that the cell is able to produce the transcription factors.
70
Q

What is the advantage of iPS cells?

A

No need for embryos.

71
Q

What does iPS cells mean/stand for?

A

Induced pluripotent stem cells.

72
Q

How many types of cell can iPS cells differentiate into?

A

Most possible types of specialised cell.

73
Q

What stem cells do iPS cells behave like?

A

Embryonic stem cells.

74
Q

Explain the process of therapeutic cloning

A
  • Take nucleus of an ovum and replace with the nucleus of a cell from the patient.
  • The cell is administered with a small electric shock to start it dividing. Once it reaches the blastocyst stage, the stem cells could be removed and cultured to produce genetically identical tissues for the patient.
75
Q

Is therapeutic cloning research allowed?

A

This research has been allowed by the government but all embryos must be destroyed after 14 days, to avoid human cloning.

76
Q

Explain the ethical issues surrounding embryonic stem cell use

A

Obtaining stem cells from embryos from IVF results in the destruction of an embryo that could become a fetus if placed in a womb.

  • Some believe that at the moment of fertilisation an individual is formed that has the right to life - so they believe that it is wrong to destroy embryos.
  • Some have fewer objections so stem cells being obtained from egg cells that aren’t fertilised by sperm, but have been artificially activated to start dividing - as cells can’t survive past a few days and wouldn’t produce a fetus in the womb.
  • Some think only adult stem cells should be used and no embryo is destroyed but these cells can’t develop into all the specialised cells that embryonic stem cells can.
77
Q

What have proved useful in reducing the ethical issues surrounding the use of embryonic stem cells?

A

Induced pluripotent stem cells:

  • Have the potential to be as flexible as embryonic stem cells, but, as they’re obtained from adult cell tissue, there aren’t the same ethical issues surrounding their use.
  • Possible iPS cells could be made from a patient’s own cells so they would be genetically identical and could then be used to gro some new tissue or an organ that the patient’s body wouldn’t reject.
78
Q

Why is rejection of transplants caused by?

A

The patient’s immune system recognising the tissue as foreign and attacking it.

A-level Biology (42 decks)

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