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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
What is a chiasma?
The point at which the crossing-over of two non-sister chromatids occurs.
26
What is a cleavage furrow?
When the plasma membrane pinches during cytokinesis.
27
What is independent assortment?
When maternal and paternal chromosomes move randomly to separate poles.
28
What is the function of an erythrocyte?
Transports oxygen to the body's cells
29
Give four adaptations of an erythrocyte.
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
What is the function of a neutrophil?
Destroys pathogens using phagocytosis and enzymes
31
Give three adaptations of a neutrophil.
Flexible shape 🡪 fits through narrow capillaries Flexible shape 🡪 can form pseudopodia for phagocytosis Many lysosomes 🡪 contain digestive enzymes to destroy pathogens
32
What is the function of a sperm cell?
To fertilise an ovum (egg) and provide half the DNA required for development of an embryo.
33
Give four adaptations of a sperm cell.
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
What is the function of a root hair cell?
Absorbs water and mineral ions from the soil
35
What are four adaptations of a root hair cell?
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
What is the function of a ciliated epithelial cell?
Move substances, e.g. mucus, through a tissue
37
What are two adaptations of a ciliated epithelial cell?
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
What is the function of the squamous epithelium?
Provides an outer layer for structures such as capillaries, alveoli.
39
What are three adaptations of the squamous epithelium?
A single layer of flattened cells. Thin layer 🡪 short diffusion pathway. Permeable 🡪 allows for diffusion of gases.
40
What is the function of the guard cells?
Control the opening and closing of stomata in the leaf surface Controls rate of gas exchange and transpiration (water loss)
41
What are two adaptations of the guard cells?
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
What are stem cells?
Undifferentiated / Unspecialised cells that have the potential to differentiate into a specialised cell
43
Stem cells are self-renewing. What does this mean?
Can divide by mitosis an unlimited number of times.
44
What are the three types of stem cell?
- Totipotent - Multipotent - Pluripotent
45
Which type of stem cell can differentiate into ANY cell type?
Totipotent
46
Where are totipotent stem cells usually found?
In early-stage embryos
47
Which type of stem cell can differentiate into almost any type of cell, but not the placenta?
Pluripotent
48
Which type of stem cell can differentiate into limited cell types within one specific lineage only?
Multipotent
49
Give one example of a place where multipotent stem cells are found in the body.
E.g. bone marrow, skin, brain
50
Which type of stem cells are found in the inner cell mass of a blastocyst (later stage embryo)?
Pluripotent
51
Why can't erythrocytes undergo mitosis?
They do not have a nucleus, so do not have any DNA
52
Name the process that produces erythrocytes in the bone marrow.
Erythropoiesis
53
Describe the process of erythropoiesis.
- Hematopoietic stem cells divide to form proerythrocytes - Proerythrocytes differentiate into erythrocytes
54
Describe the changes that occur when a haematopoietic stem cell differentiates into an erythrocyte.
- Nucleus is ejected - Lots of haemoglobin is produced - Organelles involved in protein synthesis (e.g. ribosomes) are ejected
55
Describe the changes that occur when a hematopoietic stem cells differentiates into a neutrophil.
- Indentations form in the nucleus, giving it a multi-lobed structure - Accumulations of granules or lysosomes (vesicles containing hydrolytic enzymes)
56
Name the tissue that differentiates into xylem cells and phloem cells.
Cambium (meristem tissue) in the roots, shoots and stems
57
Describe the changes that occur when a cambium cell differentiates into a xylem cell.
- Lose their cytoplasm - Lose their end walls - Deposit their lignin into their cell walls
58
Describe the changes that occur when a cambium cell differentiates into a phloem cell.
- Lose some of their cytoplasm - Lose some of their organelles - Develop sieve plates at their end cell walls
59
What is used as a source of embryonic stem cells in stem cell therapy?
Waste embryos from IVF
60
What are the advantages of using multipotent stem cells in stem cell therapy?
- Less ethical considerations as the donor can give consent - Could use your own stem cells, so less risk of rejection
61
What are the disadvantages of using multipotent stem cells in stem cell therapy?
- 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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