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A Level Biology OCR B > 8. The Developing Cell > Flashcards

8. The Developing Cell Flashcards

1
Q

What is Cell Cycle?

A

Cycle of cell growth, maturity and division

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2
Q

Length of Cell Cycle for Embryo Cells? (in minutes)

A

~8-60 minutes

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3
Q

Length of Cell Cycle for Yeast Cells? (in hours)

A

~1.5 – 3 hours

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4
Q

Length of cell cycle for intestinal cells? (in hours)

A

~12 hours

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5
Q

Length of Cell Cycle for Bone Marrow Cells? (in hours)

A

~18 hours

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6
Q

Length of Cell Cycle for Stomach Epithelial Cells? (in hours)

A

~24 hours

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7
Q

Length of Cell Cycle for Liver Cells? (in years)

A

~1 year

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8
Q

3 Main Stages of Cell Cycle?

A

Interphase
Mitosis
Cytokinesis

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9
Q

Stages of Interphase ?

A 
G1  (Growth 1)
G1 Checkpoint
S (Synthesis)
G2 (Growth 2)
G2 Checkpoint
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10
Q

Stages of Mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

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11
Q

What happens during G1 phase of interphase?

A

Cell increases in size and mass
All metabolic processes remain active
Organelles replicated (except chloroplasts and mitochondria)
Increased Protein Synthesis Occurs

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12
Q

What happens during G1 checkpoint of interphase?

A

Cells check :
Chemicals needed for replication are present

For damage in DNA before entering S phase

Cell is suitable size

Cell has sufficient nutrients

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13
Q

What happens during Synthesis of interphase?

A

DNA is replicated

Using semi-conservative replication

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14
Q

What happens during G2 phase of interphase?

A

Chloroplasts & mitochondria increase in size and divide

Cell continues to increase in size and mass

Energy stores are increased

Spindle fibres start to form

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15
Q

What happens during G2 checkpoint of interphase?

A

Cell checks
All DNA has been replicated without damage
Cell is of correct size

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16
Q

What happens during mitosis?

A

Nuclear division

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17
Q

What happens during cytokinesis?

A

Equal division of cytosol and organelles (equal division of cytoplasm)
Forming 2 genetically identical daughter cells

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18
Q

Which proteins control the timing and sequence of the cell cycle?

A

Cyclins

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19
Q

What enzymes do cyclins activate?

A

Cyclin-dependent kinase (CDK)

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20
Q

What do CDKs catalyse?

A

the addition of a phosphate group onto the protein

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21
Q

What is the phosphorylation of proteins?

A

the addition of a phosphate group onto a protein, catalysed by CDKs

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22
Q

What does the phosphorylation of proteins change?

A

Tertiary structure of cyclins

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23
Q

What can mutations to cyclin genes or CDK genes lead to?

A

Failure to repair DNA

which could cause cancer

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24
Q

Importance of mitosis?

A

growth of multicellular organisms
repair of damaged tissues
replacement of cells
asexual reproduction

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25
Q

What is a chromosome?

A

linear structures found in pairs

one molecule of DNA

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26
Q

What are chromatids?

A

Part of a chromosome after it has undergone semi-conservative replication (SCR)
Sister chromatids are genetically identical to each other

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27
Q

What 5 features are the same in homologous chromosomes?

A 
Biochemical Structure (DNA)
Physical Shape and Size
Sequence of Genes
Gene loci (position of genes)
Centromere position
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28
Q

What features are different in homologous chromosomes?

A

Origins (one maternal, one paternal)

Alleles (variants of a gene)

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29
Q

Human diploid number?

A

2n = 46

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30
Q

What happens during Prophase?

A 
Chromosomes shorten and thicken
Centrioles move towards poles
Microtubules form
Nucleolus breaks down
Nuclear envelope breaks down
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31
Q

What happens during Metaphase?

A

Chromosomes line up on equator

Spindle fibres attach to centromere

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32
Q

What happens during Anaphase?

A

Spindle fibres contract, exerting a pulling force on centromeres
Centromere splits
Daughter chromosomes pulled to opposite poles

33
Q

What happens during Telophase?

A 
Daughter Chromosomes reach poles
Chromosomes uncoil and lengthen
Spindle fibres disintegrate
Centrioles replicate
Nuclear envelope reforms around chromosomes at each pole
Nucleolus reforms
34
Q

What happens during cytokinesis in animals?

A

Cell surface membrane invaginates
Cleavage furrow forms in the middle of cell
Cell surface membrane pinches until to two sides of cell surface membrane meet
Cytoplasm divides equally in two
Organelles divided equally into 2 new daughter cells

35
Q

Where does cytokinesis happen in plants?

A

Only in meristematic tissue e.g. root tip and shoot tip

36
Q

What happens during cytokinesis in plants?

A

Vesicles from golgi apparatus assemble on equator forming cell plate
Vesicles fuse with each other and the csm
Cell wall formed along middle lamella
Cytoplasm divides equally into two
Organelles divided equally into 2 new daughter cells

37
Q

Why is it important that the cell wall is formed along the middle lamella before daughter cells are separated? (during cytokinesis in plants)

A

to prevent osmotic lysis form surround aqueous environment

38
Q

What is a telomere?

A

region of repetitive DNA sequence at each end of eukaryotic chromosomes in most eukaryotes.

39
Q

What do telomeres prevent?

A

DNA damage

Fusion of chromosomes with neighbouring chromosomes

40
Q

How do telomeres prevent DNA damage?

A

By forming caps at end of each strand of DNA that protect chromosomes

41
Q

What happens to the telomere each time a cell divides?

A

Some of the telomere is lost

42
Q

What happens if a telomere becomes too short?

A

Chromosome reaches ‘critical length’ and can no longer replicate
This results in apoptosis

43
Q

What is telomerase?

A

an enzyme that elongates chromosomes by adding TTAGGG sequences to end of existing chromosomes

44
Q

Where is telomerase found?

A

Fetal tissues
Adult Germ Cells
Tumour Cells

45
Q

Why do somatic cells age?

A

Because they don’t use telomerase regularly

46
Q

5 lifestyle factors that can shorten telomeres?

A 
Stress
Obesity
Smoking
Lack of exercise
Poor diet
47
Q

What is Apoptosis?

A

programmed cell death in multicellular organisms

48
Q

What type of process is apoptosis?

A

active process

49
Q

What is Necrosis?

A

unregulated cell death after trauma

50
Q

What type of process is necrosis?

A

passive process

51
Q

What is necrosis caused by?

A

Cell Surface Membrane rupturing

Release of hydrolytic enzymes

52
Q

5 Signals that control apoptosis

A 
p53
Cytokines
Hormones
Growth Factors
Nitrous Oxide
53
Q

What is pyknosis?

A

cell shrinking and chromatin in nucleus condensing

54
Q

What is karyorrhexis?

A

breaking down of the nuclear envelope

55
Q

What are apoptopic bodies?

A

cell fragments

56
Q

Sequence of events during apoptosis?

A

Cell shrinks, chromatin in nucleus condenses
Enzymes break down cytoskeleton and cell contents
Cytosol becomes denser - organelles become more tightly packed
CSM changes and blebs form
Nuclear envelope breaks down
DNA fragments
Apoptopic bodies formed (cell fragments)
Phosphatidylserine binds to receptors on macrophages
Macrophages engulf apoptopic bodies
Cell debris removed by phagocytes

57
Q

At the end of apoptosis, why is cell debris removed by phagocytes?

A

To prevent damage to other cells and tissues

58
Q

What is apoptosis essential for?

A 
Developing fetus
Puberty
Formation of connections between neurones in brain
Development of immune system
Production of xylem tissue in plants
59
Q

Apoptosis is essential in organisms undergoing ……….?

A

metamorphosis

60
Q

What are stem cells?

A

undifferentiated cells

61
Q

Properties of stem cells

A

Self-renewal

Potency

62
Q

What is meant by self-renewal?

A

ability to divide many times while maintaining an unspecialised state

63
Q

What is meant by potency?

A

ability to differentiate into specialised cells

64
Q

What is the nuclear: cytoplasmic ratio like of stem cells?

A

Large nuclear:cytoplasmic ratio

65
Q

3 types of stem cells

A

Totipotent
Pluripotent
Multipotent

66
Q

Define: totipotent cells

A

embryonic stem cells that can differentiate into all types of cell within an organism

67
Q

Source of totipotent cells

A

very early embryos

meristematic tissue in plants

68
Q

Define: pluripotent cells

A

embryonic stem cells that can give rise to any cells of the organisms except extra-embryonic cells such as placenta and chorion

69
Q

Source of pluripotent cells

A

inner cell mass of blastocyst

i.e embryos ~5 days old

70
Q

Uses of pluripotent cells

A

Can be grown in vitro
Cell replacement therapies (e.g. to treat Parkinson’s disease or produce pancreatic-beta cells to treat Type 1 diabetes or produce cardiac muscle cells to treat heart disease)
Drug testing in vitro
Studying development of diseases in vitro

71
Q

Define: multipotent cells

A

adult stem cells that can give rise to limited number of cell types

72
Q

Source of multipotent cells

A

Haemocytoblasts (bone marrow stem cells)
Epithelial stem cells
Bone stem cells
Umbilical cord blood

73
Q

Uses of multipotent cells

A

Treatment of leukaemia and other blood/bone cancers

Possible future use for nervous system diseases (Parkinson’s/Alzheimer’s)

74
Q

Define: multipotency

A

ability of stem cell to differentiate into discrete cell types

75
Q

Problems with potential stem cell therapies

A

Reproductive cloning
Destruction of human embryo (destruction of human lifer)
No viable long-term treatment with embryonic stem cells
Stem cell transplants may produce tumours

76
Q

What are induced pluripotent stem cells (iPSCs)

A

technique developed to reprogramme differentiated adult cells back into pluripotent stem cells

77
Q

Problem with iPSCs

A

May cause tumours called teratomas

78
Q

Cell Specialisation process?

A

3-5 days: blastocyst ball contains ~30 cells

19 days: cells differentiate (some genes switched off)

A Level Biology OCR B (3 decks)

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