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

8. The Developing Cell Flashcards

(78 cards)

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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
What is a chromosome?
linear structures found in pairs | one molecule of DNA
26
What are chromatids?
Part of a chromosome after it has undergone semi-conservative replication (SCR) Sister chromatids are genetically identical to each other
27
What 5 features are the same in homologous chromosomes?
``` Biochemical Structure (DNA) Physical Shape and Size Sequence of Genes Gene loci (position of genes) Centromere position ```
28
What features are different in homologous chromosomes?
Origins (one maternal, one paternal) | Alleles (variants of a gene)
29
Human diploid number?
2n = 46
30
What happens during Prophase?
``` Chromosomes shorten and thicken Centrioles move towards poles Microtubules form Nucleolus breaks down Nuclear envelope breaks down ```
31
What happens during Metaphase?
Chromosomes line up on equator | Spindle fibres attach to centromere
32
What happens during Anaphase?
Spindle fibres contract, exerting a pulling force on centromeres Centromere splits Daughter chromosomes pulled to opposite poles
33
What happens during Telophase?
``` Daughter Chromosomes reach poles Chromosomes uncoil and lengthen Spindle fibres disintegrate Centrioles replicate Nuclear envelope reforms around chromosomes at each pole Nucleolus reforms ```
34
What happens during cytokinesis in animals?
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
Where does cytokinesis happen in plants?
Only in meristematic tissue e.g. root tip and shoot tip
36
What happens during cytokinesis in plants?
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
Why is it important that the cell wall is formed along the middle lamella before daughter cells are separated? (during cytokinesis in plants)
to prevent osmotic lysis form surround aqueous environment
38
What is a telomere?
region of repetitive DNA sequence at each end of eukaryotic chromosomes in most eukaryotes.
39
What do telomeres prevent?
DNA damage | Fusion of chromosomes with neighbouring chromosomes
40
How do telomeres prevent DNA damage?
By forming caps at end of each strand of DNA that protect chromosomes
41
What happens to the telomere each time a cell divides?
Some of the telomere is lost
42
What happens if a telomere becomes too short?
Chromosome reaches 'critical length' and can no longer replicate This results in apoptosis
43
What is telomerase?
an enzyme that elongates chromosomes by adding TTAGGG sequences to end of existing chromosomes
44
Where is telomerase found?
Fetal tissues Adult Germ Cells Tumour Cells
45
Why do somatic cells age?
Because they don't use telomerase regularly
46
5 lifestyle factors that can shorten telomeres?
``` Stress Obesity Smoking Lack of exercise Poor diet ```
47
What is Apoptosis?
programmed cell death in multicellular organisms
48
What type of process is apoptosis?
active process
49
What is Necrosis?
unregulated cell death after trauma
50
What type of process is necrosis?
passive process
51
What is necrosis caused by?
Cell Surface Membrane rupturing | Release of hydrolytic enzymes
52
5 Signals that control apoptosis
``` p53 Cytokines Hormones Growth Factors Nitrous Oxide ```
53
What is pyknosis?
cell shrinking and chromatin in nucleus condensing
54
What is karyorrhexis?
breaking down of the nuclear envelope
55
What are apoptopic bodies?
cell fragments
56
Sequence of events during apoptosis?
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
At the end of apoptosis, why is cell debris removed by phagocytes?
To prevent damage to other cells and tissues
58
What is apoptosis essential for?
``` Developing fetus Puberty Formation of connections between neurones in brain Development of immune system Production of xylem tissue in plants ```
59
Apoptosis is essential in organisms undergoing ..........?
metamorphosis
60
What are stem cells?
undifferentiated cells
61
Properties of stem cells
Self-renewal | Potency
62
What is meant by self-renewal?
ability to divide many times while maintaining an unspecialised state
63
What is meant by potency?
ability to differentiate into specialised cells
64
What is the nuclear: cytoplasmic ratio like of stem cells?
Large nuclear:cytoplasmic ratio
65
3 types of stem cells
Totipotent Pluripotent Multipotent
66
Define: totipotent cells
embryonic stem cells that can differentiate into all types of cell within an organism
67
Source of totipotent cells
very early embryos | meristematic tissue in plants
68
Define: pluripotent cells
embryonic stem cells that can give rise to any cells of the organisms except extra-embryonic cells such as placenta and chorion
69
Source of pluripotent cells
inner cell mass of blastocyst | i.e embryos ~5 days old
70
Uses of pluripotent cells
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
Define: multipotent cells
adult stem cells that can give rise to limited number of cell types
72
Source of multipotent cells
Haemocytoblasts (bone marrow stem cells) Epithelial stem cells Bone stem cells Umbilical cord blood
73
Uses of multipotent cells
Treatment of leukaemia and other blood/bone cancers | Possible future use for nervous system diseases (Parkinson's/Alzheimer's)
74
Define: multipotency
ability of stem cell to differentiate into discrete cell types
75
Problems with potential stem cell therapies
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
What are induced pluripotent stem cells (iPSCs)
technique developed to reprogramme differentiated adult cells back into pluripotent stem cells
77
Problem with iPSCs
May cause tumours called teratomas
78
Cell Specialisation process?
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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