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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
Q

Describe a ciliates epithelial cell

A

Shape: column shaped cells
Found: trachea, bronchi
Contains basement membrane

26
Q

Describe a sperm cell

A 
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
Q

How do guard cells work?

A
  • 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
Q

Define a cell

A

Basic structures, functional and biological unit of all known organisms

29
Q

Define a tissue

A

Collection of specialised cells that work together to perform a particular function
Eg: bone, skin, cartilage

30
Q

Define an organ

A

Collection of tissues working together to perform a specific function

31
Q

Define an organ system

A

Organs that work together to perform a particular function

32
Q

What is the function pf the cuticle in a leaf?

A

Barrier to water, prevents evaporation

33
Q

What is the function of upper epidermis?

A

Water conservation- prevents water loss, where light intensity and heat are the greatest

34
Q

What is the function of the palisade mesophyll layer?

A

Helps in photosynthesis

35
Q

Whats the function of the spongy mesophyll layer?

A

Gas exchange

36
Q

Whats the function of the stoma?

A

Regulate photosynthesis, transpiration, respiration etc

37
Q

Whats the function of the guard cells?

A

Regulate the rate of transpiration

38
Q

Whats the function of the vascular bundle (contains xylem and phloem)?

A

Transport water and mineral bonds to the photosynthesis tissue

39
Q

What happens in interphase of meiosis?

A
  • DNA replicates, so each chromosome consists of two chromatids
  • homologous pairs of chromosomes contain the same genes, but possibly different alleles
40
Q

What happens in early prophase 1 of meiosis?

A
  • 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
Q

What happens in late prophase 1 of meiosis?

A

-homologous chromosomes pair up forming bivalent (centromeres repel, other parts of chromatids join together)

42
Q

What happens in metaphase 1?

A
  • bivalents randomly line up at equator

- spindle fibres attach to them at the centromeres

43
Q

What happens in anaphase 1?

A
  • 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
Q

What happens in telophase 1?

A
  • 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
Q

What happens in prophase 2?

A

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
Q

What happens in metaphase 2?

A
  • chromosomes randomly line up at the equator, independent assortment of chromatids
  • attach to spindles at centromere
47
Q

What happens in anaphase 2?

A
  • chromosomes are pulled apart by spindles
  • centromeres divide to allow the chromosomes to spilt
  • chromatids are pulled to the poles
48
Q

What happens in telophase 2?

A
  • chromatids (now chromosomes) reach poles and de-condense

- buckeye envelope reforms forming four separate nuclei

49
Q

What happens in cytokinesis in meiosis?

A

May occur and the cells divide
-each cell has one set of chromosomes (half number of original parent cell)
1 diploid= 4 haploids

50
Q

What happens in interphase of meiosis?

A
  • DNA replicates, so each chromosome consists of two chromatids
  • homologous pairs of chromosomes contain the same genes, but possibly different alleles
51
Q

What happens in early prophase 1 (early) of meiosis?

A
  • 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
Q

What happens in late prophase 1 of meiosis?

A
  • 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
Q

What happens in metaphase 1?

A
  • bivalents randomly line up at equator

- spindle fibres attach to them at the centromeres

54
Q

What happens in anaphase 1?

A
  • 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
Q

What happens in telophase 1?

A
  • 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
Q

What happens in prophase 2?

A

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
Q

What happens in metaphase 2?

A
  • chromosomes randomly line up at the equator, independent assortment of chromatids
  • attach to spindles at centromere
58
Q

What happens in anaphase 2?

A
  • chromosomes are pulled apart by spindles
  • centromeres divide to allow the chromosomes to spilt
  • chromatids are pulled to the poles
59
Q

What happens in telophase 2?

A
  • chromatids (now chromosomes) reach poles and de-condense

- buckeye envelope reforms forming four separate nuclei

60
Q

What happens in cytokinesis in meiosis?

A

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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