a level biology > 2.1.6 Cell Division > Flashcards

2.1.6 Cell Division Flashcards

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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 happens in G1?

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

what happens in G2?

A
  • short gap before mitosis
  • growth of cells
  • growth of organelles
  • protein synthesis to make proteins needed for M
  • spindle begins to form
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17
Q

what happens in S? why?

A

DNA replication so that daughter cells have IDENTICAL and 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
• needs DNA repairing

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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

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20
Q

what happens at G2 checkpoint?

A
  • checks for any mutation of DNA
  • checks if daughter cells might not receive identical genetic information
  • checks if proteins might not function the way they should
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21
Q

why does mitosis occur/ why is it needed?

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

what happens in prophase?

A
  • nuclear envelope breaks down
  • chromosomes condense (wraps around histone proteins)
  • centrioles (a protein) move to opposite ends of the cell forming a spindle fibre (network of protein fibres)
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23
Q

what happens in metaphase?

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

what happens in anaphase?

A
  • chromatids pulled to opposite poles of the cell by spindle fibres (cytoskeleton) contracting
  • centromere breaks
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25
what happens in telophase?
- **nuclear envelope** begins to **form** - **chromosomes uncoil** (uncondense) - **spindle fibres break** down - **cell surface membrane** undergoes **cytokinesis**
26
how do you do the root 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 are homologous pair of chromosomes? (bivalent)
- **TWO X SHAPES**: one chromosome is one X shape (two sister chromatids) - one chromosome (one X) is **maternal** - one chromosome (one X) is **paternal** - **same genes** - **different alleles** - **same length** - **centromeres** in the **same place** in both chromosomes (both Xs)
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** to **form a BIVALENT** - like meiosis, centrioles move opposite ends and **spindle fibres form** - **nuclear envelope breaks down**
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** and **seperate homologous pairs** - **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 meosis II ?
**same as mitosis stages**, because **it’s the mitosis of the 2 haploid cells formed in meosis I**, to **form 2 identical haploid cells of THOSE**, **NOT PARENT**. So **in total 4 haploid cells genetically different** to **PARENT**
39
what does the nuclear envelope break down into?
small vesicles
40
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**
41
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**
42
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**
43
what are the components of the cell cycle? which of these components make up only interphase?
- G1 - S - G2 - M - **interphase = G1 + S + G2**
44
why do gametes have to be haploid?
so they can **form a diploid zygote** at **fertilisation**
45
what stage of mitosis has a checkpoint and what happens in that checkpoint?
- **metaphase** - cell **checks that all chromosomes are attached to spindles before** mitosis can **continue**
46
why is the root tip experiment done?
to **observe cell cycle and mitosis**
47
how can you tell from one of those stupid exam questions that a cell is dividing by meiosis and not mitosis?
- reduction division - **less chromosomes overtime** - **genetically different** daughter cells
48
what’s the diff between anaphase I and II?
I —> **homologous pairs** (bivalents) are **seperated** II —> **pairs of SISTER CHROMATIDS are separated** so **4 new daughter cells inherits ONE chromatid** from each chromosome (there’s **2 homologous pairs**)
49
what are the roles of epithilial cells?
cover surface of organs
50
how are ciliated epithilial cells adapted?
have **cilia that move particles in airways**
51
how are squamous epithelia adapted?
**very thin** to allow **efficient diffusion of gases in lungs**
52
what are tissues?
**same type of cell working together** for the **same function**
53
what are organs?
**groups of DIFFERENT tissues** **working together** for the **same function**
54
what are the pairs of tissues in animals and plants that work together (to form organs) that you need to know about?
1. squamous & ciliated epithelial 2. cartilage & muscle 3. xylem & phloem
55
what’s the individual roles of squamous & ciliated epithilial tissues and the role of them working together?
- squamous —> **allows for thin diffusion pathway** - ciliated —> **waft mucus** to back of throat - together —> in **lungs to aid diffusion of gases** and to **clear airways**
56
what’s the individual roles of muscle & cartilage tissues and the role of them working together?
- muscle —> **contract** to **constrict airways** - cartilage —> **supports trachea** - together —> in **lungs, controlling ventilation**
57
what’s the individual roles of xylem & phloem tissues and the role of them working together?
- xylem —> transport of **water** - phloem —> transports **assymilates** - together —> **create vascular bundle*$ in plants
58
what’s a stem cell?
**undifferentiated cells** that can **differentiate into any cell type** by **mitosis**
59
what’s a totipotent stem cell? where can it be found in humans?
**differentiate into ANY TYPE** of body cell, can be found in **embryonic cells** toti = total
60
what’s a pluripotent stem cell?
can differentiate into **any type of cell EXCEPT** extra **embryonic stem cells*
61
what’s a multipotent stem cell?
can **differentiate into more than one cell type** but **not all** cell types, eg is **adult stem cells**
62
where do xylem and phloem come from?
from **meristem cells** that are dividing, like the **vascular cambium when it divides**
63
what EXACTLY is mitosis?
**division** of **NUCLEUS**, NOT cell
64
what does telophase LOOK like?
**darkened areas at each pole** of cell
65
what’s not visible in a cell in interphase?
chromosomes
66
why is mitosis used for asexual reproduction in plants?
- makes **genetically identical** cells - **MAINTAINS (not makes) diploid** number
67
explain the role of a meristem tissue in plants
- it’s the **source of undifferentiated cells** - **differentiate** into **xylem and phloem** cells
68
name potential uses of stem cells in medicine
- replacing damaged tissues - research
69
contrast prokaryotic and eukaryotic DNA
- **prokaryotic** DNA is found in **cytoplasm** while eukaryotic is in the nucleus - **prokaryotic** has **circular DNA** - **prokaryotic is not associated** with **histone proteins**
70
describe change in DNA mass from M phase to G1?
**decrease** due to **cytokinesis**
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