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a level biology > 2.1.6 Cell Division > Flashcards

2.1.6 Cell Division Flashcards

1
Q

what is the function of a guard cell?

A

to open and close the stomata

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2
Q

what are the adaptations of guard cells?

A
  1. pores
    —> enables gas exchange
  2. thin outer walls and thick inner walls
    —> force guard cells to bend outwards, opening stomata
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3
Q

what is the function of root hair cells?

A

absorb water and mineral ions from the soil

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4
Q

what are the adaptations of root hair cells?

A
  1. large SA
    —> more water absorbed
  2. permeable cell wall
    —> entry of water and ions
  3. extra mitochondria
    —> provide energy for active transport
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5
Q

what is the function of palisade cells?

A

do most of photosynthesis

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6
Q

what are the adaptations of palisade cells?

A
  1. many chloroplasts
    —> so a lot of sunlight is absorbed
  2. thin walls
    —> faster rate of diffusion for co2
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7
Q

what is the function of erythrocytes?

A

carries oxygen in the blood

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8
Q

what are the adaptations of erythrocytes?

A
  1. biconcave disk shape
    —> provides large SA for gas exchange
  2. no nucleus
    —> more room for more haemoglobin
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9
Q

what is the function of a neutrophil?

A

defends body against diseases

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10
Q

what are the adaptations of neutrophils?

A
  1. flexible
    —> allows engulfing of pathogens
  2. many lysosomes
    —> digestive enzymes to break down pathogens
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11
Q

what are the adaptations of sperm cells?

A
  1. flagellum
    —> to swim
  2. lots of mitochondria
    —> energy provided to swim
  3. acrosome
    —> contains digestive enzymes which enables egg penetration
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12
Q

which processes must occur in a cell during interphase before mitosis can take place?

A
  • protein synthesis
  • dna replication
  • centrioles replication
  • synthesis of organelles
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13
Q

what are two ways cell division in plants differs from cell division in animals ?

A
  • no centrioles in plant
  • cell wall forms in plant
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14
Q

where are two parts in a plant where meristematic tissue can be found

A
  • tip of root
  • tip of shoot
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15
Q

what is G1 in interphase?

A
  • growth of cells
  • growth of organelles
  • protein synthesis
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16
Q

what’s G2 phase?

A
  • growth of cells
  • growth of organelles
  • protein synthesis
  • spindle begins to form
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17
Q

what is the S phase?

A
  • DNA replication
  • full copy of DNA
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18
Q

what does the G0 checkpoint do?

A

cell leaves cycle either permanently or temporarily because:

  • it has fully differentiated
  • DNA repairing
19
Q

what happens at G1 checkpoint?

A

cell checks if chemicals needed for DNA replication are present and checks if DNA is damaged before entering S

20
Q

what happens at G2 checkpoint?

A
  • checks for a mutation in the DNA
  • daughter cells might not receive identical genetic information
  • proteins might not function
21
Q

why does mitosis occur?

A
  • asexual reproduction
  • repair of damaged tissues
  • growth of an organism
22
Q

what happens in prophase?

A
  • nuclear envelope breaks down
  • chromosomes condense
  • centrioles move to opposite ends of the cell forming a spindle fibre
23
Q

what happens in metaphase?

A
  • spindle fibres attach to centromeres on chromosome
  • chromosomes line up along the equator of the cell
24
Q

what happens in anaphase?

A
  • centromeres divide, separating each pairs of sister chromatids
  • spindle contracts, pulling chromatids to opposite ends of the cell
25
what happens in telophase?
- **nuclear envelope** begins to **form** - **chromosomes uncoil** - **spindle fibres break** down - **cell surface membrane** undergoes **cytokinesis**
26
how do you do the tip squash experiment?
1. **heat plant sample** in **acid** —> **breaks down cell wall** 2. **stain** sample —> **contrast** provided —> **chromosomes more visible** 3. **squash** the sample —> make **single layer of tissue** —> so **light can pass through** the sample
27
what does multipotent mean?
cells that can **produce a limited range of cell types**
28
how do cells differentiate?
- **lose cytoplasm and organelles** - **end cells between cells disappear**
29
what features are not in mature xylem cells?
- nucleus - cytoplasm
30
why are onion root tips used to view cells and undergoing mitosis?
- is a **meristem** - **no chlorophyll** present
31
what are characteristics of stem cells that are useful?
- can **differentiate** into **other cell types** - can **divide an unlimited amount of times** - can **replace unhealthy cells**
32
what does homologous pair of chromosomes mean?
- one is **maternal** - one is **paternal** - **same genes** - **different alleles** - **same length** - **centromeres** in the **same place**
33
what does meiosis produce?
- 4 haploid - genetically different - gametes
34
what happens during prophase l ?
- **chromosomes condense** - homologous pairs **cross over** and **pair up** (bivalents)
35
what happens in metaphase l ?
- **independent assortment** - **spindle fibres** attach to **centromeres** - bivalents **line up across centre** of cell
36
what happens in anaphase I ?
- **spindle fibres contract** - ++chromosomes pulled to opposite ends** of cell
37
what happens in telophase I ?
- **nuclear envelope** reformed - chromosomes **uncoil** - **cytokineses** occurs —> **membrane pinches off** and **2 daughter cells** produced
38
what happens in prophase to telophase II ?
**same as meiosis I** however **no crossing over in prophase II**
39
what does the nuclear envelope break down into?
small vesicles
40
what does pluripotent mean?
can differentiate into **almost any cell type** and found in the **embryo**
41
what does totipotent mean?
can differentiate into **any cell type**
42
why’s it important that one chromosome from each homologous pair each ends up in a new cell?
- so that **all cells** produced are **haploid** - when **fertilisation** takes place the cell produced is **diploid**
43
why is the possible diff combinations of chromosomes produced by mitosis not the actual number?
- **doesn’t** take into account **crossing over** - resulting in **different combo of alleles** - **only** takes into account **independent selection**
44
how do the processes in meiosis lead to genetic variation?
- **homologous chromosomes pair up** - forms **chiasma** and **crossing over** occurs - **new combo** of **alleles** - **independent assortment** - produces **varying combo of alleles**

a level biology (12 decks)

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