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OCR BIOLOGY (MODULE 2) > CELL DIVISION, CELL DIVERSITY AND CELLULAR ORGANISATION > Flashcards

CELL DIVISION, CELL DIVERSITY AND CELLULAR ORGANISATION Flashcards

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1
Q

What is a homologous pair?

A

One of each pair came from the mother and one from the father (same gene, different allele)

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2
Q

What is it called when cytoplasm divides in mitosis?

A

Cytokinesis

-cytoplasm divides into two

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3
Q

What happens on interphase?

A
  • DNA uncoils, not visible
  • DNA replication occurs, checks for errors
  • centrioles replicate (animals only)
  • cell size increases (more cytoplasm)
  • new organelles produced (eg: mitochondria, chloroplasts)
  • cell active, ATP required
  • PROTEIN SYNTHESIS OCCURS
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4
Q

What happens in prophase?

A

CHROMOSOMES BECOME VISIBLE AS THEY SHORTEN AND THICKEN

  • centrioles move to opposite ends (poles) of the cells
  • microtubules develop from pole to pole forming spindle fibres
  • nucleolus disappears (forms part of chromosomes)
  • nuclear envelope breaks down
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5
Q

What happens in metaphase?

A

CHROMOSOMES LINE UP AT THE EQUATOR OF THE CELL

  • centrioles reach the two poles
  • spindle fibres attach to centromere on each chromosomes to arrange them along the equator of the cell
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6
Q

What happens in anaphase?

A

CHROMATIDS PULLED APART TO OPPOSITE ENDS OF THE CELL

  • centromeres divide
  • spindle fibres contract and shorten, pulling chromatids apart, centromere leading, towards opposite ends of the cells
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7
Q

What happens in telophase?

A

A NUCLEUR ENVELOPE REFORMS ARROUND CHROMOSMES

  • the chromatids have now reached the poles and can be regarded as distinct chromosomes
  • the nucleolus reappears
  • chromosomes uncoil to form chromatin
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8
Q

What happens in cytokinesis in animal cells?

A
  • cell division involves furrowing and cleavage of cytoplasm
  • cytokinesis starts at the edge of the cell
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9
Q

What happens in cytokinesis in plant cells?

A
  • cell division involves the formation of a cell plate

- cytokinesis starts from the middle of the cell

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10
Q

What is the importance of mitosis?

A
  1. Asexual reproduction
    - eg: runners in spider and strawberry plants
  2. Growth in multicellular organisms
    - eg: animals and plants
  3. Repair of tissues/organs
    - eg: forming a scar after you have cut yourself
  4. Replacement of cells (when they are old or damaged)
    - eg: blood cells (produced in bone marrow)
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11
Q

What are the purposes of checkpoints in the cell cycle?

A
  • prevent uncontrolled division, leading to tumours
  • detect and repair damage to DNA (eg: from UV lights)
  • ensure cycle is not reversed
  • DNA is only copied once during each cell cycle
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12
Q

Where does mitosis take place in animal cells?

A
  • many are capable of mitosis (not all as some are specialised- eg: nerve cells, skin cells, etc)
  • stem cells divide
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13
Q

Where does mitosis take place in plant cells?

A 
-only special regions undergo mitosis 
>meristems- have a thin cell wall to stretch and enlarge 
Examples:
-just behind root shots and tips
-cambium (between xylem and phloem)
-buds
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14
Q

Compare mitosis in plants and animals

A
  • (P)no centriole present, (A)centrioles present
  • (P)cell division involves the formation of a cell plate, (A)involves furrowing and cleavage of cytoplasm
  • (P)cytokinesis starts from middle of cell, (A)starts at the edge of a cell
  • (P)occurs in meristem, (A)throughout body
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15
Q

What’s a stem cell?

A

Undifferentiated cell

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16
Q

What does totipotent mean?

A

Having the potential for developing in various specialised ways in response to external or internal stimuli

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17
Q

Define pluripotent

A

Capable of developing into any type of cell or tissue except those that form a placenta or embryo

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18
Q

Define multi potent

A

Having power to produce or influence several affects or results

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19
Q

What are sources of animal stem cells?

A
  • adult stem cells: umbilical core, blood

- human embryonic stem cells: donated human embryos

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20
Q

What’s the source of plant stem cells?

A

-meristem fell

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21
Q

Define differentiation

A
  • cells become specialised to perform a particular function

- shape and content of cells can vary, including having different numbers of organelles

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22
Q

What is an erythrocytes cell?

A

RBC
Produced in bone marrow from stem cells
The cell loses nucleus, mitochondria, golgi and rough ER
Contains haemoglobin (protein)
Biconcave disc which aids oxygen transport

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23
Q

What is a neutrophil cell?

A

WBC
Produced in bone marrow from stem cells
Contains lysosomes which gives a granular appearance
Engulfs microbes

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24
Q

Describe a squamous epithelial cell

A

Shape: flat, thin cell
Found: lining inside blood vessels (gives low friction)
Has a basement membrane which attaches cells to tissues

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25
Describe a ciliates epithelial cell
Shape: column shaped cells Found: trachea, bronchi Contains basement membrane
26
Describe a sperm cell
``` Small ling thin shape FLAGELLUM- microtubules for movement NUCLEUS- 1 set of chromosomes MITOCHONDRIA- ATP for swimming ACROSOME- specialised lysosome to digest outside of egg ```
27
How do guard cells work?
- guards are the only epidermal cells with chloroplasts - daylight= stomata opens= CO2 enters leaf 1. Chloroplasts make sugars (photosynthesis) 2. Guard cells actively pump potassium ions
28
Define a cell
Basic structures, functional and biological unit of all known organisms
29
Define a tissue
Collection of specialised cells that work together to perform a particular function Eg: bone, skin, cartilage
30
Define an organ
Collection of tissues working together to perform a specific function
31
Define an organ system
Organs that work together to perform a particular function
32
What is the function pf the cuticle in a leaf?
Barrier to water, prevents evaporation
33
What is the function of upper epidermis?
Water conservation- prevents water loss, where light intensity and heat are the greatest
34
What is the function of the palisade mesophyll layer?
Helps in photosynthesis
35
Whats the function of the spongy mesophyll layer?
Gas exchange
36
Whats the function of the stoma?
Regulate photosynthesis, transpiration, respiration etc
37
Whats the function of the guard cells?
Regulate the rate of transpiration
38
Whats the function of the vascular bundle (contains xylem and phloem)?
Transport water and mineral bonds to the photosynthesis tissue
39
What happens in interphase of meiosis?
- DNA replicates, so each chromosome consists of two chromatids - homologous pairs of chromosomes contain the same genes, but possibly different alleles
40
What happens in early prophase 1 of meiosis?
- chromosomes condense, super coil and become visible - nucleolus disappears and nuclear envelope breaks down - centrioles migrate to poles and form spindles which are made of microtubules
41
What happens in late prophase 1 of meiosis?
-homologous chromosomes pair up forming bivalent (centromeres repel, other parts of chromatids join together)
42
What happens in metaphase 1?
- bivalents randomly line up at equator | - spindle fibres attach to them at the centromeres
43
What happens in anaphase 1?
- homologous chromosomes of each bivalent are pulled apart by spindles, towards poles (from centromere) - centromeres don’t divide, each chromosome consists of two chromatids
44
What happens in telophase 1?
- in animal cells the nucleus envelope will reform, may be a short interphase where the chromosome uncoils a little - cytokinesis may occur and the cell will spilt
45
What happens in prophase 2?
Everything happens in two nuclei - chromosomes re-condense, each consists of two chromatids - nuclear envelope disintergrates - centrioles replicate and spindles start to develop perpendicular to the previous division
46
What happens in metaphase 2?
- chromosomes randomly line up at the equator, independent assortment of chromatids - attach to spindles at centromere
47
What happens in anaphase 2?
- chromosomes are pulled apart by spindles - centromeres divide to allow the chromosomes to spilt - chromatids are pulled to the poles
48
What happens in telophase 2?
- chromatids (now chromosomes) reach poles and de-condense | - buckeye envelope reforms forming four separate nuclei
49
What happens in cytokinesis in meiosis?
May occur and the cells divide -each cell has one set of chromosomes (half number of original parent cell) 1 diploid= 4 haploids
50
What happens in interphase of meiosis?
- DNA replicates, so each chromosome consists of two chromatids - homologous pairs of chromosomes contain the same genes, but possibly different alleles
51
What happens in early prophase 1 (early) of meiosis?
- chromosomes condense, super coil and become visible - nucleolus disappears and nuclear envelope breaks down - centrioles migrate to poles and form spindles which are made of microtubules
52
What happens in late prophase 1 of meiosis?
- homologous chromosomes pair up forming bivalent (centromeres repel, other parts of chromatids join together) - crossing over of chromatids (genetic variation), recombination- chiasmata (cross over point)
53
What happens in metaphase 1?
- bivalents randomly line up at equator | - spindle fibres attach to them at the centromeres
54
What happens in anaphase 1?
- homologous chromosomes of each bivalent are pulled apart by spindles, towards poles (from centromere) - centromeres don’t divide, each chromosome consists of two chromatids
55
What happens in telophase 1?
- in animal cells the nucleus envelope will reform, may be a short interphase where the chromosome uncoils a little - cytokinesis may occur and the cell will spilt
56
What happens in prophase 2?
Everything happens in two nuclei - chromosomes re-condense, each consists of two chromatids - nuclear envelope disinterested - centrioles replicate and spindles start to develop perpendicular to the previous division
57
What happens in metaphase 2?
- chromosomes randomly line up at the equator, independent assortment of chromatids - attach to spindles at centromere
58
What happens in anaphase 2?
- chromosomes are pulled apart by spindles - centromeres divide to allow the chromosomes to spilt - chromatids are pulled to the poles
59
What happens in telophase 2?
- chromatids (now chromosomes) reach poles and de-condense | - buckeye envelope reforms forming four separate nuclei
60
What happens in cytokinesis in meiosis?
May occur and the cells divide -each cell has one set of chromosomes (half number of original parent cell) 1 diploid= 4 haploids

OCR BIOLOGY (MODULE 2) (6 decks)

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