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Biology 1&2 > cell growth, differentiation & cancer > Flashcards

cell growth, differentiation & cancer Flashcards

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1
Q

binary fission

A

process through which prokaryotes divide

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2
Q

eukaryotic chromosomes

A
  • Are linear in shape
  • Have a constriction called the centromere
  • Have a kinetochore which forms a part of the centromere
  • Have ends called telomeres.
  • Appear as a pair of strands when about to divide.
  • Each strand = chromatid.
  • Are a single stranded except when about to divide.
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3
Q

kinetochore

A

a patch of protein where the spindle attaches which forms a part of the centromere

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4
Q

centromere

A

Have a constriction called the centromere where spindle fibres attach before cell division occurs

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5
Q

cell cycle

A
  • ell division of eukaryotic cells is more complicated than in prokaryotes
  • have checking systems to make sure replication of chromosomes and construction of new cells is performed accurately
    -defective cells destroyed
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6
Q

mitosis

A

involves four phases of nuclear division and is followed immediately by division of the cytoplasm during cytokinesis.

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7
Q

G1 phase

A
  • Cell grows
  • Organelles & proteins synthesized
  • Contains the first checkpoint
  • Cell is checked to ensure that it is ready to divide.
  • Environmental conditions are assessed to ensure that they are suitable for division to take place.
    (Note: G stand for gap – a gap in the cycle of division.)
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8
Q

S phase

A
  • New chromosomes are synthesised in a process called DNA replication
  • Chromosomes become double stranded
  • Chromosomes are still loosely wound and are invisible even under a light microscope.
  • centriole is duplicated in animal cells.
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9
Q

G2 phase

A
  • At the end of the G2 phase is another checkpoint.
    Checks are for:
  • Cell size
  • DNA replication
    If DNA damage is found:
  • either repaired
  • cell is forced to undergo apoptosis
    -if fine = cell divides
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10
Q

prophase

A
  • Chromosomes condense and appear
  • Mitotic spindle begins to form
  • In animal cells the spindle attaches to the centrioles at one end.
  • Nucleolus disappears
  • Nuclear membrane breaks down
  • Some chromosomes become attached to the spindle
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11
Q

metaphase

A
  • All chromosomes attached to the spindle
  • spindle attaches to the chromosomes at kinetochore
  • Chromosomes line up across the equator
  • division check occurs to ensure that the chromosomes are attached to the spindle and lined up correctly.
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12
Q

anaphase

A
  • Sister chromatids separate to either end of the cell
  • cell starts to elongate
  • cytoskeleton and a group of proteins which can move along the cytoskeleton, facilitate these movements.
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13
Q

telophase

A
  • chromosomes start to decondense.
  • loosely wound form
  • disappear from view.
  • spindle breaks down and a nuclear membrane forms around each set of chromosomes.
  • Nucleoli become visible in each nucleus.
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14
Q

cytokinesis (not apart of mitosis)

A
  • formation of the new nuclear membranes.
  • begins during either anaphase or telophase.
  • ends after mitosis is completed.
  • In animals the plasma membrane pinches in and separates the cytoplasm
  • In plants a cell plateforms down the middle of the cell
  • The cell plate is the start of a new cell wall.
  • New plasma membranes are also present around the cells.
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15
Q

apoptosis

A
  • the process that leads to the destruction of cells through an orderly process.
  • Cells undergo apoptosis if they have finished their useful life
  • Have DNA damage
  • Have mitochondrial damage
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16
Q

necrosis

A
  • the death of cells in a disorderly manner.
  • occurs as a result of mechanical damage (eg: a cut) or as a result of infection
  • Necrosis results in inflammation and an immune response.
17
Q

capsases

A
  • an enzyme
    the breakdown of:
  • DNA into fragments
  • The membrane proteins
    = The cytoskeleton which allows the plasma membrane to protrude
  • Proteins in the cytosol
  • Organelles
  • Once apoptosis has begun, it cannot be stopped, and the cell will die.
18
Q

intrinsic pathway

A
  • Damage occurs to the mitochondria resulting in the escape of cytochrome c, a respiratory protein, into the cytosol.
  • Cytochrome c activates a caspase cascade.
19
Q

extrinsic pathway

A
  • message is received by a receptor on the outside of the cell (called a death receptor)
  • often from an immune system cell.
  • messenger triggers the activation of the caspase cascade inside the cell.
20
Q

steps of apoptosis

A
  • The cell separates from other cells
  • Cytoskeleton collapses
    The cell shrinks
  • Organelles, including the nucleus, breaks down
  • Plasma membrane forms blebs.
  • Blebs separate from the cell, taking cell contents with them.
  • Apoptotic bodies are phagocytosed by white blood cells (mostly macrophages).
21
Q

too much apoptosis

A
  • Leads to fewer cells than is required for a healthy body.
  • leads to degenerative diseases such as Alzheimer’s disease (loss of neurons due to excessive apoptosis), Parkinson’s disease and motor neuron disease (MND).
22
Q

too little apoptosis

A
  • Means that more cells occur in the body than usual.
  • This can lead to syndactyly (webbing between fingers and toes caused by cells that usually apoptose during development)
  • Also can result in cancer.
23
Q

causes of cancer

A
  • Mutations in the protein, p53 which normally initiates apoptosis at the G1 checkpoint if irreparable DNA damage is found.
  • Mutations which cause defective caspases
  • Mutations which stop the formation of apoptotic bodies
  • Mutations which stop the cell accepting external messages to undergo apoptosis
  • Mutations which cause over-production of proteins that normally keep healthy cells from apoptosis, so the unhealthy cell cannot suicide.
24
Q

tumor suppressor genes

A

Code for proteins that:
- Slow or stop cell division
- Repair DNA damage or errors
- Cause cells to undergo apoptosis
Reduced activity of these genes can result in cancer

25
Q

proto-oncogenes

A

Code for proteins that:
- Stimulate cell division
- Inhibit differentiation
- Regulate programmed cell death
Increased activity of these genes can result in cancer

26
Q

mutagens

A

Cause genetic changes
Include:
- many chemicals in cigarettes
- ionizing radiation
- X-rays
- UV light
If they result in cancer they are known as carcinogens.

27
Q

teratogens

A

Cause problems in foetal development
Include:
- some hormones
- some antibiotics
- oral anti-coagulants
- thyroid drugs
- drugs and alcohol

28
Q

stem cells

A

3 types:
- totipotent (least differentiated
- pluripotent
- multipotent (most differentiated)

  • most flexible of the cells is the zygote which is the fertilised egg.
  • newly formed zygote can become any cell type.
  • After 5 days the cell bundle is a blastocyst
  • some cells are beginning to specialise (differentiate)
29
Q

adult stem cells

A
  • Are multipotent
  • Can sometimes be induced into an earlier stage of potency
  • Less likely to be rejected by the immune system
  • Require more manipulation because they are not naturally pluripotent,
  • the more manipulation the greater the chance of something going wrong.
29
Q

embryonic stem cells

A
  • Are pluripotent so can become most cell types
  • Many people have moral objections to embryonically derived stem cells
  • Organs made of non-self cells are likely to result in an immune response & possible rejection

Biology 1&2 (3 decks)

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