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OCR A biology Module 2 > 2.1.6 Cell Division > Flashcards

2.1.6 Cell Division Flashcards

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1
Q

cell cycle

A
  1. interphase(G1, S and G2)
  2. nuclear division- mitosis or meiosis
  3. cytokinesis
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2
Q

interphase

A
  • Longest stage in the cell cycle
  • When DNA replicates (S-phase) and organelles duplicate while cell grows (G1&G2-phase)
  • DNA replicates and appears as two sister chromatids held by centromere
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3
Q

mitosis

A
  • One round of cell division
  • Two diploid, genetically identical daughter cells
  • Growth and repair (e.g. clonal expansion)
  • Comprised of prophase, metaphase, anaphase and telophase(PMAT)
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4
Q

prophase

A
  • Chromosomes condense and become visible
  • Nuclear envelope disintegrates
  • In animals - centrioles separate & spindle fibre structure forms
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5
Q

Metaphase

A
  • Chromosomes align along equator of cell
  • Spindle fibres released from poles now attach to centromere and chromatid
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6
Q

Anaphase

A
  • Spindle fibre contracts (using ATP) to pull chromatids, centromere first, towards opposite poles of cell
  • Centromere divides in two
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7
Q

Telophase

A
  • Chromosomes at each pole become longer and thinner again
  • spindle fibres disintegrate + nucleus reforms
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8
Q

Cytokinesis

A

The division of the cytoplasm to create two new cells

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9
Q

Mitotic index

A
  • Used to determine proportion of cells undergoing mitosis
  • Calculated as a percentage OR decimal
    the number of cells in mitosis/ the total number of cells
    x100 for percentage
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10
Q

meiosis

A

Two nuclear divisions that result in four genetically different haploid daughter cells

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11
Q

haploid

A

one copy of each chromosome

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12
Q

diploid

A

two copies of each chromosome

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13
Q

Genetic differences introduced by meiosis

A
  • Independent assortment of homologous chromosomes
  • Crossing over
    mutationssss
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14
Q

crossing over

A
  • Chromosomes condense and thicken in prophase I
  • Homologous chromosomes pair to form bivalents
  • Crossing over can occur between the chromatids of bivalents
  • This results in new combinations of alleles in the resulting gamete
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15
Q

Independent assortment

A
  • Homologous pairs of chromosomes line up opposite each other on either side of the equator during metaphase I
  • It is random which side of the equator the maternal and paternal pair aligns
  • As a result, each gamete receives a different combination of maternal and paternal chromosomes
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16
Q

Erythrocyte

A
  • These are red blood cells
  • They have a biconcave shape to increase the surface area for diffusion and increase the cell flexibility for it to fit through narrow capillaries
  • These cells have no nucleus to maximise oxygen-carrying capacity
  • They are made from stem cells in the bone marrow
17
Q

Neutrophils

A
  • A type of white blood cell
  • Neutrophils have a lobed nucleus and granular cytoplasm
  • These cells are flexible to enable them to surround pathogens and engulf them
  • They contain lysosomes filled with the hydrolytic enzyme, lysozyme
18
Q

Sperm cells

A
  • The flagellum contains many mitochondria to release energy for locomotion to enable the sperm cell to move towards the egg cell
  • The acrosome in the head of the cell contains digestive enzymes to digest the wall of the egg cell so the sperm can penetrate and fertilise the egg
19
Q

Palisade cells

A
  • Located in the mesophyll tissue layer of leaves
  • Palisade cells are rectangular, tightly packed cells that contain many chloroplasts to absorb and maximise light energy for photosynthesis
  • They have thin cell walls to reduce the diffusion distance of carbon dioxide
20
Q

Root hair cells

A
  • Cells on the surface of roots
  • Long projections to increase surface area for osmosis of water and active transport of mineral ions
  • Thin cell wall to reduce the diffusion distance
21
Q

Guard cells

A

These pair of cells have flexible walls, more so on one side, which results in the cells bending when turgid to open stomata and closing when flaccid and this helps control water loss by transpiration

22
Q

Squamous epithelial cells

A
  • Usually only a single layer of flat cells in contact with the basement membrane of epithelium
  • This provides a short diffusion distance
23
Q

Ciliated epithelial cells

A
  • These cells have hair-like projections that say to move substances, such as mucus, out of the lungs, or an egg in the oviduct
  • Goblet cells are also located within the epithelium and these release mucus to trap molecules
24
Q

Cartilage

A
  • This is a connective tissue that is firm and flexible
  • It is located in the outer ear, nose and the end of bones
  • It provides structural support and it prevents the bones from rubbing together and causing damage
  • It is made up of collagen and elastin fibres, and chondrocyte cells within an extracellular matrix
25
Q

Muscle

A
  • Composed of tissues that can contract and relax to create movement
  • Muscles have multiple fibres connecting with connective tissues in between
26
Q

Xylem

A
  • The cells that make up the part of the vascular bundle in plants responsible for transporting water and mineral ions
  • The tissue is made up of elongated, hollow dead cells, with lignin in the walls to strengthen and waterproof the walls
  • Xylem tissues are made from the stem cells in the meristem
27
Q

Phloem

A
  • Form part of the vascular bundle
  • Transport organic substances made in photosynthesis
  • Made of sieve tube element cells and companion cells
28
Q

Sieve tube elements

A
  • Cells have perforated end walls
  • Lacking most organelles to make the transport of sugars easier
29
Q

Stem cells

A
  • Stem cells are undifferentiated cells that can self-renew (continually divide) and become specialised
  • Different types of stem cells have different differentiation abilities:
    Totipotent Pluripotent Multipotent Unipotent
30
Q

Totipotent cells

A
  • Totipotent cells can divide and produce any type of body cell
  • During development, totipotent cells transport only part of their DNA, resulting in cell specialisation - Totipotent cells only occur for a limited time in mammalian embryos
31
Q

Pluripotent cells

A
  • Pluripotent cells are found in embryos and can become almost any type of cell
  • They are often used in research
32
Q

Multipotent and unipotent stem cells

A
  • Found in mature mammals - Can divide to form a limited number of different cell types
33
Q

Potential uses of stem cells

A
  • Stem cells could be used in both research and medicine:
    Repairing damaged tissues Treatment of neurological conditions such as Alzheimer’s and Parkinson’s
    Research into developmental biology

OCR A biology Module 2 (6 decks)

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