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

2.1.6 Cell division, cell diversity and cellular organisation Flashcards

1
Q

What happens during interphase in the cell cycle?

A

Cell growth and DNA replication

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2
Q

What happens during G1 of interphase in the cell cycle?

A

Cell increases in size and mass

RNA, enzymes and proteins required for
growth are made.

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3
Q

What happens in the ‘S’ stage of interphase in the cell cycle?

A

DNA replicates in the nucleus.

Each chromosome contains two identical
sister chromatids.

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4
Q

What happens during G2 of interphase in the cell cycle?

A

Cell further increases in size and mass.

New DNA is checked for errors and repaired.

Tubulin proteins are made (involved in forming the mitotic spindle).

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5
Q

Name the process by which the cytoplasm divides following mitosis.

A

Cytokinesis

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6
Q

Name three stages in the cell cycle where a checkpoint occurs.

A
  • G1
  • G2
  • Metaphase (in mitosis)
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7
Q

Name the stages of mitosis in the correct order.

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
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8
Q

What is a centromere?

A

A section of DNA that holds together two sister chromatids following DNA replication

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9
Q

What is a centrosome?

A

An organelle near the nucleus that produces spindle fibres

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10
Q

What is the role of the spindle fibres in mitosis?

A

Attaches to the centromeres and pulls apart chromosomes during mitosis.

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11
Q

Describe what happens during prophase in mitosis.

A
  • Chromosomes condense
  • Centromeres move to opposite poles
  • Spindle fibres form
  • Nuclear envelope breaks down
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12
Q

Describe what happens during metaphase in mitosis.

A
  • Chromosomes line up along equator of cell
  • Spindle fibres attach to centromeres
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13
Q

Describe what happens during anaphase in mitosis.

A
  • Spindle fibres shorten
  • Sister chromatids separate at the centromere
  • Chromosomes (separated chromatids) move to opposite poles of the cell
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14
Q

Describe what happens during telophase in mitosis.

A
  • Chromatids elongate (decondense)
  • Nuclear envelope forms around each new set of chromosomes
  • The spindle fibres break down
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15
Q

Which step of mitosis is being shown in this picture?

A

Anaphase

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16
Q

Which step of mitosis is being shown in this picture?

A

Telophase

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17
Q

Which step of mitosis is being shown in this picture?

A

Prophase

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18
Q

Which step of mitosis is being shown in this picture?

A

Metaphase

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19
Q

How many daughter cells are formed in meiosis?

A

Four

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20
Q

What happens during prophase 1 in meiosis?

A
  • DNA condenses
  • Crossing-over of non-sister chromatids may occur at point known as the chiasma
  • Centrosomes move to opposite poles
  • Spindle fibres form
  • Nuclear envelope breaks down
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21
Q

What happens in metaphase 1 in meiosis?

A

Bivalents (pairs of homologous chromosomes) line up along spindle equator

Independent assortment of maternal and paternal chromosomes occurs

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22
Q

What happens during anaphase 1 in meiosis?

A

Spindle fibres pull whole chromosomes to opposite poles

Centromeres do not divide

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23
Q

What happens during telophase 1 in meiosis?

A

Spindle fibres break down

Nuclear envelope forms around each group of whole chromosomes

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24
Q

What is a bivalent?

A

A pair of homologous chromosomes

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25
Q

What is a chiasma?

A

The point at which the crossing-over of two non-sister chromatids occurs.

26
Q

What is a cleavage furrow?

A

When the plasma membrane pinches during cytokinesis.

27
Q

What is independent assortment?

A

When maternal and paternal chromosomes move randomly to separate poles.

28
Q

What is the function of an erythrocyte?

A

Transports oxygen to the body’s cells

29
Q

Give four adaptations of an erythrocyte.

A

Biconcave 🡪 increases surface area for oxygen absorption

Lots of haemoglobin 🡪 to readily bind oxygen

No nucleus 🡪 more space for haemoglobin

Elastic membrane 🡪 can fit through narrow capillaries

30
Q

What is the function of a neutrophil?

A

Destroys pathogens using phagocytosis and enzymes

31
Q

Give three adaptations of a neutrophil.

A

Flexible shape 🡪 fits through narrow capillaries

Flexible shape 🡪 can form pseudopodia for phagocytosis

Many lysosomes 🡪 contain digestive enzymes to destroy pathogens

32
Q

What is the function of a sperm cell?

A

To fertilise an ovum (egg) and provide half the DNA required for development of an embryo.

33
Q

Give four adaptations of a sperm cell.

A

Haploid nucleus 🡪 half the normal number of chromosomes

Acrosome in head 🡪 contains enzymes to digest egg

Mitochondria in midpiece 🡪 release energy for tail movement

Rotating tail 🡪 allows sperm to swim to ovum in the oviduct

34
Q

What is the function of a root hair cell?

A

Absorbs water and mineral ions from the soil

35
Q

What are four adaptations of a root hair cell?

A

Root hair 🡪 large surface area for osmosis

Thin walls 🡪 shorter diffusion distance for water

Contains mitochondria 🡪 allows active transport of mineral ions

Concentrated cell sap 🡪 maintains water potential gradient

36
Q

What is the function of a ciliated epithelial cell?

A

Move substances, e.g. mucus, through a tissue

37
Q

What are two adaptations of a ciliated epithelial cell?

A

Beating cilia 🡪 move materials across surface of epithelial tissue

Surrounded by goblet cells 🡪 secrete mucus to trap dust, dirt and pathogens (to prevent infections).

38
Q

What is the function of the squamous epithelium?

A

Provides an outer layer for structures such as capillaries, alveoli.

39
Q

What are three adaptations of the squamous epithelium?

A

A single layer of flattened cells.

Thin layer 🡪 short diffusion pathway.

Permeable 🡪 allows for diffusion of gases.

40
Q

What is the function of the guard cells?

A

Control the opening and closing of stomata in the leaf surface

Controls rate of gas exchange and transpiration (water loss)

41
Q

What are two adaptations of the guard cells?

A

Thick inner cell walls, thin outer cell walls 🡪 difference allows cells to bend.

Many chloroplasts and mitochondria 🡪 release energy required to open/close stomata.

42
Q

What are stem cells?

A

Undifferentiated / Unspecialised cells that have the potential to differentiate into a specialised cell

43
Q

Stem cells are self-renewing.
What does this mean?

A

Can divide by mitosis an unlimited number of times.

44
Q

What are the three types of stem cell?

A
  • Totipotent
  • Multipotent
  • Pluripotent
45
Q

Which type of stem cell can differentiate into ANY cell type?

A

Totipotent

46
Q

Where are totipotent stem cells usually found?

A

In early-stage embryos

47
Q

Which type of stem cell can differentiate into almost any type of cell, but not the placenta?

A

Pluripotent

48
Q

Which type of stem cell can differentiate into limited cell types within one specific lineage only?

A

Multipotent

49
Q

Give one example of a place where multipotent stem cells are found in the body.

A

E.g. bone marrow, skin, brain

50
Q

Which type of stem cells are found in the inner cell mass of a blastocyst (later stage embryo)?

A

Pluripotent

51
Q

Why can’t erythrocytes undergo mitosis?

A

They do not have a nucleus, so do not have any DNA

52
Q

Name the process that produces erythrocytes in the bone marrow.

A

Erythropoiesis

53
Q

Describe the process of erythropoiesis.

A
  • Hematopoietic stem cells divide to form proerythrocytes
  • Proerythrocytes differentiate into erythrocytes
54
Q

Describe the changes that occur when a haematopoietic stem cell differentiates into an erythrocyte.

A
  • Nucleus is ejected
  • Lots of haemoglobin is produced
  • Organelles involved in protein synthesis (e.g. ribosomes) are ejected
55
Q

Describe the changes that occur when a hematopoietic stem cells differentiates into a neutrophil.

A
  • Indentations form in the nucleus, giving it a multi-lobed structure
  • Accumulations of granules or lysosomes (vesicles containing hydrolytic enzymes)
56
Q

Name the tissue that differentiates into xylem cells and phloem cells.

A

Cambium (meristem tissue) in the roots, shoots and stems

57
Q

Describe the changes that occur when a cambium cell differentiates into a xylem cell.

A
  • Lose their cytoplasm
  • Lose their end walls
  • Deposit their lignin into their cell walls
58
Q

Describe the changes that occur when a cambium cell differentiates into a phloem cell.

A
  • Lose some of their cytoplasm
  • Lose some of their organelles
  • Develop sieve plates at their end cell walls
59
Q

What is used as a source of embryonic stem cells in stem cell therapy?

A

Waste embryos from IVF

60
Q

What are the advantages of using multipotent stem cells in stem cell therapy?

A
  • Less ethical considerations as the donor can give consent
  • Could use your own stem cells, so less risk of rejection
61
Q

What are the disadvantages of using multipotent stem cells in stem cell therapy?

A
  • Donated cells must be a close match to avoid rejection
  • Lack of donors due to painful procedures
  • Limited cell types can be produced, so a limited range of conditions can be treated

A Level Biology - OCR Biology A (13 decks)

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