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Alevel Biology OCR A > 2.1.6 Cell division, cell diversity and cellular organisation COMPLETE > Flashcards

2.1.6 Cell division, cell diversity and cellular organisation COMPLETE Flashcards

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1
Q

Structure of a chromosome

A
  • Tips are the Telomere
  • Centre held together by a centromere
  • Protein is wound around histones
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2
Q

The cell cycle order

A
  1. Interphase
  2. Prophase
  3. Metaphase
  4. Anaphase
  5. Telophase
    Proper meteors always telephone
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3
Q

Interphase

Mitosis

A

DNA is uncoiled and not visible
DNA replication occurs
Cell size increases so more cytoplasm, organelles and chloroplast

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4
Q

Prophase

Mitosis

A

Chromosomes becomes visible as they shorten and thicken.
Centrioles move towards the opposite poles
Microtubules develop
Nuclear envelope breakdown

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5
Q

Metaphase

Mitosis

A

Chromosomes line up at the equator
centrioles reach the two poles
Spindle fibres attach to the centromeres and pulls to arrange them

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6
Q

Anaphase

Mitosis

A

Chromatids pull apart to opposite ends of the cell
The centromeres divide and spindle fibres contract and shorten to pull them apart
Centromere leads

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7
Q

Telophase

Mitosis

A

Nuclear envelope reforms around chromosomes as the chromatids have now reached the poles.
The nucleus reappears and the chromosomes uncoil to form chromatin

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8
Q

Cytokinesis

A

Cytoplasm divides into two each containing a full set of chromosomes
ANIMALS: Furrows a cleavage by starting at the edge
PLANT: Forms a cell plate and starts from the middle

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9
Q

Importance of Mitosis

A
  • Asexual reproduction
  • Growth of multicellular organisms
  • Repair to replace damaged cells
  • Replace the blood cells broken down in the liver
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10
Q

Purpose of Checkpoints

A
  • Prevent uncontrolled division
  • Detect and repair damage to DNA
  • Ensure cycle doesn’t reverse
  • DNA only copied once
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11
Q

G2 Checkpoint

A

Checks cell size, DNA replication and that theres no damage

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12
Q

G1 Checkpoint

A

Checks cell size, Nutrients, Growth factors, DNA damage

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13
Q

G0 Checkpoint

A

Resting phase where cells leave permanently or temporarily
Cell differentiation to specialise them
Check for DNA damage
Lymphocytes can start dividing again and re enter cycle

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14
Q

Mitosis in Plants

A

Takes place in the meristem regions, just behind the root tips and shoot tips, the cambium and in the buds.
No centrioles present just the cell plate

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15
Q

Mitosis in Yeast Cells

A

Known as Budding
The nucleus divides by mitosis and the cell swells on one side creating an uneven distribution of cytoplasm.
The cell wall forms and so do two genetically identical cells

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16
Q

Mitosis in Prokaryote Cells

A

Known as binary fission
The cell grows to its limit then DNA begins to replicate
The two loops of DNA are pulled to opposite ends of the cell
This divides into two cells and a new wall forms

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17
Q

Stem Cells

A

Undifferentiated Cells that can differentiate into specialised ones

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18
Q

Totipotent Cell

A

Has the potential to develop into any type of cell found in the human body

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19
Q

Pluripotent Cell

A

Stem cells that develop the 3 primary germ layers

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20
Q

Multipotent cells

A

Thy can develop into more than one cell type, limited to adult stem cells and cord blood cells

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21
Q

Sources of animal stem cells

A

Embryonic Stem Cells

Adult Stem Cells

22
Q

Uses of Stem Cells

A
  • Cellular Medicines such as diabetes treatment
  • To understand how our bodies work
  • Test drug efficiency
  • Therapies to replace damaged cells
23
Q

Differentiation

A

Cells become specialised to perform a particular function.

24
Q

Erythrocytes

A

Produced in the bone marrow
Only contain haemoglobin
Have a biconcave disk shape

25
Q

Neutrophils

A

Destroy bacteria and other foreign materials by phagocytosis.
Produced in bone marrow
Contain lots of lysosomes

26
Q

Squamous Epithelial Cells

A

Thin flat cells that lie inside blood vessels to reduce friction

27
Q

Ciliated Epithelium Cells

A

Column Shaped with lots of cilia and mitochondria

Found in the trachea, bronchi, bronchioles

28
Q

Sperm Cells

A

Small long thin shape with a flagellum containing microtubules for movement
Mitochondria for energy
Acrosome on the tip specialised to breakdown the outside of an egg.

29
Q

Palisade Cells

A

Long thin walls

Contains lots chloroplasts for photosynthesis

30
Q

Root hair cells

A

Hair line projection with thin cell walls
Found near the tips of roots
Increases the SA
Aids the absorption of water and minerals

31
Q

Guard Cells

A

Contain chloroplasts and open during the day to let CO2 into the leaves

32
Q

DEFINITION- Tissues

A

Collection of Cells specialised to work together to perform a particular function

33
Q

DEFINITION- Organs

A

Collection of tissues working together to perform a particular function

34
Q

DEFINITION- Organ System

A

Organs working together to perform a life function

35
Q

Examples of Tissues

A

Cartilage
Muscle
Xylem
Phloem

36
Q

Leaf Structure

A
  • Cuticle
  • Upper Epidermis
  • Palisade Mesophyll layer
  • Spongy Mesophyll Layer
  • Stroma
  • Guard Cells
  • Vascular bundle
37
Q

Prophase I Early

Meiosis

A

Chromosomes condense, supercoil and become visible
The nucleus disappears and the envelope breakdown
Centrioles migrate to the poles and form spindle fibres

38
Q

Prophase I Late

Meiosis

A

Homologous chromosome pairs form bivalent pairs

Recombination occurs and chromosomes are crossed over at points called the chiasmata

39
Q

Metaphase I

Meiosis

A

The bivalents randomly line up at the equator
Independent Assortment takes place
Spindle fibres attach onto the centromeres

40
Q

Anaphase I

Meiosis

A

The homologous chromosomes are pulled apart by spindle fibres.
The chiasmata are pulled apart as they separate
Centromeres do not divide

41
Q

Telophase I

Meiosis

A

In animal cells the nuclear envelope reforms

Cytokinesis may occur and the cell might split

42
Q

Prophase II

Meiosis

A

Chromosomes re condense, each consisting of two nucleotides
Nuclear envelope goes
Centrioles replicate and spindle fibres develop perpendicular to the last ones

43
Q

Metaphase II

Meiosis

A

Chromosomes randomly line up at the equator and theres independent assortment of the chromatids
Spindle fibres attach to the centromere

44
Q

Anaphase II

Meiosis

A

Chromosomes are pulled apart by spindle fibres
Centromere divides to allow chromosome to split
Pulled to the poles

45
Q

Telophase II

Meiosis

A

Chromatids reach the poles and re condenses

The nuclear envelope reforms forming a separate nuclei

46
Q

Cytokinesis

Meiosis

A

Cytoplasm splits forming four non identical daughter cells with half of each parent cell
1 diploid -> 1 Haploid

47
Q

Causes of Variation

A

Crossing Over
Independent Assortment
Random Fertilisation
Mutation

48
Q

Crossing over

A

Occurs in prophase 1

Alleles are switched at the chiasmata producing q different combination for each chromatid

49
Q

Independent Assortment

A

Metaphase 1
Bivalents randomly line up so paternal and maternal are jumbled. This means a combination of both chromosomes could be in the gamete produced,
Metaphase 2
Chromatids orientate randomly so after crossing over they’re not identical

50
Q

Random Fertilisation

A

Any one of the 300 million of the genetically different sperm could fertilise the egg

51
Q

Mutation

A

During Interphase when DNA is replicated, mutation may occur

Alevel Biology OCR A (26 decks)

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