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A-level Biology > 2.1.6 - Cell division, cell diversity and cellular organisation > Flashcards

2.1.6 - Cell division, cell diversity and cellular organisation Flashcards

1
Q

Define the term ‘ cell cycle’?

A

Cell cycle : Highly ordered sequence of events resulting in division of the cell and formation of two genetically identical daughter cells

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2
Q

What are the main key stages in the cell cycle ?

A
  • Interphase
  • Mitosis
  • Cytokinesis
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3
Q

What are the stages that occur during interphase ?

A
  • G1/ first growth phase
  • S/ synthesis phase
  • G2 / second growth phase
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4
Q

What happens during G1/ First growth phase ?

A
  • Proteins that synthesise organelles are produced
  • Organelles replicas
  • Cells increase in size
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5
Q

What happens during S/ synthesis phase ?

A

DNA is replicated in the nucleus

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6
Q

What happens in the G2/ Second growth phase ?

A
  • The cell continues to increase in size
  • Energy stores increase
  • Duplicated DNA is checked for errors
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7
Q

What are checkpoints ?

A

Checkpoints are control mechanisms of the cell cycle

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8
Q

What are the functions of checkpoints ?

A

They monitor/ verify whether the processes of each phase of the cell cycle has been accurately completed before the cell is allowed to progress to the next phase

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9
Q

What are the different checkpoints ?

A
  • G1 checkpoint ( G1 to S )
  • G2 checkpoint ( G2 to mitosis )
  • Spindle assembly/ metaphase checkpoint
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10
Q

What does the G1 checkpoint do ?

A
  • If cell satisfies requirement, cell is triggered to begin DNA replication
  • Otherwise it remains in resting state / Go
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11
Q

What does the G2 checkpoint do ?

A
  • Replicated DNA is checked for any errors
  • Then, if there are no errors found, cell initiates molecular-processes that begin mitosis
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12
Q

What does the spindle assembly/ metaphase checkpoint do ?

A
  • Once all chromosomes are attached to spindles and have aligned, mitosis can proceed
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13
Q

What is the Go phase ?

A

It is the phase when the cell temporarily or permanently leaves the cycle

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14
Q

When does the Go phase occur ?

A
  • When the cell becomes differentiated/ specialised and can no longer divide
  • Cell has irreplaceable DNA damage so no longer viable for cell division and goes under permanent Go arrest ( senescent )
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15
Q

Fine the term ‘Mitosis’ ?

A

Mitosis : The production of two new genetically identical cells from an original cell

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16
Q

What are the main stages of mitosis ?

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
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17
Q

What happens during the Interphase ?

A
  • All DNA is replicated
  • Each DNA molecule/ chromosome is converted into two identical DNA molecules called chromatids
  • Two chromatids are joined together at a region called the centromere
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18
Q

Why is it important that chromatids are kept together during mitosis ?

A

This allows them to be accurately moved and segregated into two new cells

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19
Q

What is a centromere ?

A

A region at which two chromatids are joined together

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20
Q

What happens during the prophase ?

A
  • Chromatin fibres being to coil and condense to for chromosomes, nuclear membrane beings to break down and the nucleus disappears
  • Protein microtubules form spindle-shaped structures linking poles of the cell-fibres forming spindles
  • Spindles are needed to move chromosomes into correct position before division
  • Two centrioles migrate to opposite poles of the cell
  • Spindle fibres attach to specific areas n the centimetres and start to move chromosomes to the centre of the cell
  • Nuclear envelope disappears
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21
Q

What are centrioles ?

A

Cylindrical bundles of proteins that help in formation of spindle

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22
Q

What happens during metaphase ?

A
  • Chromosomes are moved by spindle dribs to form a plane in the centre of the cell called the metaphase plate
  • they are then held in position
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23
Q

what happens during the anaphase ?

A
  • Centromeres holding together the pairs of chromatids in each chromosomes divide
  • Chromatids are separated and pulled to opposite poles of the cell by spindle fibres
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24
Q

What happens during the Telophase ?

A
  • Chromatids reach the poles and are now called chromosomes
  • New sets of chromosomes assemble at each pole and the nuclear envelope reforms around them
  • Chromosomes start to uncoil and nucleus is formed
  • Cytokenesis/ cell division begins
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25
Q

Why is mitosis important ?

A
  • Growth ( when a multicellular organism increases in size )
  • Replacement and repair of tissues in multicellular organisms ( plants, animal and fungi )
  • Asexual reproduction ( production of genetically identical offspring from one parent in multicellular organisms like plants, animals and fungi )
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26
Q

Define the term ‘Meiosis’ ?

A

Meiosis : A form of cell division which produces four genetically different haploid cells from a diploid cell achieving genetic variation

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27
Q

Why is meiosis important ?

A
  • Production of haploid cells
  • Achieves genetic variation by independent assortment and crossing over
28
Q

What is each characteristic of an organism coded for by ?

A

By two copies of each gene, one from each parent

29
Q

What is an allele?

A

Different versions of the same gene

30
Q

Explain the term ‘homologous chromosomes’ ?

A
  • Each nucleus of a cell contains two full sets of genes, a pair of genes for each characteristic
  • therefor, each nucleus contains matching sets of chromosomes called homologues chromosomes and is called a diploid cell
  • Homologous chromosomes will have the same genes in the same position
31
Q

What are the main stages of meiosis ?

A
  • Meiosis 1/ First division
  • Meiosis 2/ Second division
32
Q

What happens during Meiosis 1/ first division ?

A
  • Reduction divison occurs
  • Pairs of homologues chromosomes are operated unto two cells resulting in two haploid cells
33
Q

What happens during meiosis 2/ Second division ?

A
  • Pairs of chromatids present in each daughter cell are separated
  • This forms four haploid daughter cells overall
34
Q

What are the stages of meiosis 1 and meiosis 2 ?

A

Meiosis 1 :
- Prophase 1
- Metaphase 1
- Anaphase 1
- Telophase 1

Meiosis 2 :
- Prophase 2
- Metaphase 2
- Anaphase 2
- Telophase 2

35
Q

What happens during Prophase 1 ?

A
  • Chromosomes condense, nuclear envelope disintegrates, nucleus disappears and spindle formation begins
  • Homologous chromosomes pair up forming bivalents
  • When chromosomes are moved through the cytoplasm and brought together, the chromatids end up entangling and crossing over
36
Q

What happens during Metaphase1 ?

A
  • Same as mitosis except that homologous pairs of chromosomes assemble along the metaphase plants, not individual chromosomes
  • The orientation of each homologue pair on the metaphase plate is random ( eg. maternal or paternal chromosomes can end up facing either plate ) which is called independent assortment
  • This can result in many different combination of allies facing h poles leading to genetic variation
37
Q

What happens during Anaphase 1 ?

A
  • Homologous chromosomes are pulled to opposite poles and the chromatids stayed joined together
38
Q

What happens during Telophase 1 ?

A
  • The chromosomes assemble at each pole and the nuclear membrane reforms and chromosomes uncoil
  • Cell undergoes cytogenesis and divides into two haploid cells
39
Q

What happens during Prophase 2 ?

A
  • Chromosomes, still containing two chromes, condense
  • The nuclear envelope breaks down and spindle formation begins
40
Q

What happens during Metaphase 2 ?

A
  • Individual chromosomes assemble on the metaphase plate
  • Due to crossing over, chromatids are no longer identical so there is independent assortment again and more genetic variation produces
41
Q

What happens during Anaphase 2 ?

A
  • Chromatids of the individual chromosomes are pulled to opposite poles after division of the centromeres
42
Q

What happens during Telophase 2 ?

A
  • Chromatids assemble at the poles
  • Chromosomes uncoil and from chromatin again
  • Nuclear envelope reforms and nucleus becomes visible
  • Cytokeneiss results in division forming four haploid daughter cells
43
Q

What are the levels of organisation in multicellular organisms ?

A

Specialised cells –> Tissues –> Organs –> Organ system –> Whole Organism

44
Q

Define the term ‘specialised cells’ ?

A

Specialised cells : Differentiated cells with a specific structure/ sub-cellular structures that help them to perform a specific function

45
Q

Name maples of specialised cells ?

A
  • Erythrocytes/ Red blood cells
  • Neutrophils / A type of white blood cell
  • Squamous and ciliated epithelial cells
  • Sperm cells
  • Palisade cells
  • Root hair cells
  • Guard cells
46
Q

Explain how Erythrocytes are adapted to their role ?

A
  • Red blood cells transport oxygen around the body
  • They have a flattened biconcave shape : increases their surface area : volume ratio allowing them to take up more oxygen
  • No nuclei : Increases space for haemoglobin
  • Flexible : Enables them to squeeze through narrow capillaries
47
Q

Explain how Neutrophils are adapted to their role ?

A
  • They identify and destroy pathogens
  • They contain a multi-lobed nucleus : Makes it easier to squeeze through small gaps to reach site of infection
  • Their granular cytoplasm contains lysosomes : These contains enzymes used to attack pathogens
48
Q

How are sperm cell adapted to their role ?

A
  • Contain flagellum : Enables them to move through liquids
  • Contains lot of mitochondria : Enables them to have a lot of energy to swim and reach the egg cell
  • Acrosome contains digestive enzymes : Enables cell to digest protective layer around the egg cell and penetrate it leading to fertilisation
49
Q

How are palisade cells adapted to their role ?

A
  • Contains chloroplasts : To absorb large amounts of light for photosynthesis
  • Rectangular/ box-shaped : Enables cells to be closely packed to form continuous layer
  • Thin cell wall : Increases rate of diffusion of COv2
  • Large vacuole = Enables maintenance of turgor pressure
  • Chloroplasts ca move : To maximise light absorption
50
Q

How are root hair cells adapted to their role ?

A
  • Contains extensions/ root hairs : Increases surface area of cell and maximises uptake of water and minerals from soil
51
Q

How are guard cells adapted to their role ?

A
  • cell wall is thicker on one side and thiner on the other : enables cell to not change shape symmetrically as its volume changes
52
Q

Define the term ‘Tissue’?

A

Tissue : collection of differentiated/ specialised cells that work together to perform a specific function

53
Q

Name examples of tissue ?

A
  • Squamous and ciliated epithelia
  • Cartilage
  • Muscle
  • Xylem
  • Phloem
54
Q

How are squamous epithelia tissue adapted to their role ?

A
  • Made up of flat/ squat cells
  • Only one cell thick

= Allows for rapid diffusion ( eg. lining of lungs for gas exchange )

55
Q

How are ciliated epithelia tissue adapted to their role ?

A
  • Made up of ciliated epithelial cells canting hair-like structures called cilia : sweep mucus away from lungs in trachea
  • Goblet cells present : Release mucus to trap unwanted particles/ pathogens preventing them from reaching alveoli in lungs
56
Q

How is cartilage tissue adapted to its role ?

A
  • Contains fibres of proteins elastic and collagen
  • Made up of chondrocyte cells embedded in extracellular matrix
57
Q

Were is cartilage tissue found ?

A

Found in the outer ear, nose, trachea and in between bones

58
Q

How is muscle tissue adapted to its role ?

A
  • Skeletal/ Smoot and cardiac muscle contain myafibrils
59
Q

What is the role of muscle tissue ?

A

Tissue that shortens in length to move bones and therefore different parts of the body

60
Q

How is xylem tissue adapted to its role ?

A
  • Composed of vessel elements/ elongated dead cells : Allowing for flow of water and mineral ions from the roots to shoots of plant
  • Walls of vessel elements strengthened by lignin : provides structural support for plant
61
Q

How is phloem tissue adapted to its role ?

A
  • Made up of columns of sieve tube cells speerated by sieve plates : Allows tissue to transport organic nutrients ( sucrose ) to where they are required / from sources to sinks
62
Q

Define the term ‘Differentiation’ ?

A

Differentiation : The process by which an unspecialised cell becomes specialised

63
Q

Define the term ‘Stem cells’?

A

Stem cells : Undifferentiated cells not adapted to any particular function and have potential to differentiate into a range of specialised cell types

64
Q

What are features of stem cells ?

A
  • The can differentiate into a range of specialised cell types
  • They can undergo cell division repetitively for growth, development and tissue repair until they become specialised at which point they lose their ability to divide
65
Q

Name examples of specialised cells derived from stem cells in bone marrow and meristem tissue ?

A

Bone marrow :

  • Erythrocytes
  • Neutrophils

Meristem Tissue :
- Xylem vessels
- Phloem Sieve Tubes

66
Q

What are the potential used of stem cells in research and medicine ?

A
  • Repair of damaged tissue ( burns )
  • The treatment of neurological conditions
  • Research into developmental biology ( study of the changes that occur as multicellular organisms grow and develop )

A-level Biology (31 decks)

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