2.1.6 Cell division, cell diversity and cellular organisation

Question 1

what is the cell cycle

Answer 1

• the cell cycle is when cells divide in order to make new cells

Question 2

what are parts of the cell cycle

Answer 2

• Interphase (G1 phase, S phase, G2 phase)
• mitosis
• cytokinesis

Question 3

what occurs during G1 phase

Answer 3

• the cell is growing and carrying out its normal functions ( eg producing energy)

Question 4

what is the main goal in G1 phase

Answer 4

• to increase the size of the cell and make sure it has all the resources needed for DNA replication

Question 5

What does the cell check before entering S phase

Answer 5

• the cell checks whether the cell is large enough, has enough nutrients and is in good condition to replicate DNA

Question 6

what occurs in S phase

Answer 6

• cell makes an exact copy of its DNA every chromosome is replicated, so the cell now has two sets of chromosomes
  ( one for each daughter cell)

Question 7

what is the main goal of S phase

Answer 7

• the DNA is synthesised to ensure that when the cell divides the daughter cell will have identical genetic material

Question 8

What occurs during G2 phase

Answer 8

• the cell continues growing and and the new DNA which was synthesised ( during s phase) is checked for any errors.
• other preparations are made for cell division such as production of tubulin protein.

Question 9

what are the 4 stages of mitosis

Answer 9

• prophase
• metaphase
• anaphase
• telophase

Question 10

what is the centromere

Answer 10

a region of a chromosome where the spindle fibres attach during cell division

Question 11

what does each chromosome consist of

Answer 11

• two sister chromatids joined at the centromere

Question 12

what occurs during prophase

Answer 12

• chromosomes condenses (visible when stained)
• the nuclear envelope break down
• nucleolus disappears
• the centrioles go to opposite side of the cell and proteins form spindle fibres attached to the centromeres of each chromosome
• the spindle fibres move the chromosomes to the equator (center) of the cell

Question 13

what occurs during metaphase

Answer 13

• the spindle fibre is fully formed
• the chromosomes are now lined up at the equator of the cell

Question 14

what occurs during anaphase

Answer 14

• chromatids are pulled to opposite sides of the cell
• the centromeres divide into two and the spindle fibres shorten
• this pulls the sister chromatids towards opposite poles of the cell.

Question 15

what occurs during telophase

Answer 15

• the chromatids( now called chromosomes) have reached the poles of the cell.
• the spindle apparatus breaks down and the nuclear membrane reforms
• the chromosomes uncoil back to a chromatid
• the nucleolus reappears in each cell.
• the nuclear membrane surrounds the chromatids to form a nucleus

Question 16

what occurs during cytokinese

Answer 16

• the central cell membrane is pulled inwards by the cytoskeleton.
• this creates a groove which deepens.
• eventually the membranes fuse to form two independent cells

Question 17

the significance of mitosis in life cycles

Answer 17

• important for growth
• tissue repair
• asexual reproduction in plants, animals and fungi

Question 18

what is meiosis

Answer 18

a type of cell division to produce gametes that produce four genetically different haploid daughter cells from one parent cell.

Question 19

what is the significance of meiosis in life cycles

Answer 19

• it produces 4 haploid gametes.
• there cells are genetical different by independent assortment and crossing over

Question 20

what are the mainstages of meiosis

Answer 20

• interphase
• prophase 1
• metaphase 1
• anaphase 1
• telophase 1
• prophase 2
• metaphase 2
• anaphase 2
• telophase 2

Question 21

define homologous chromosomes

Answer 21

two chromosomes with similar genes but different alleles, one inherited from each parent

Question 22

what occurs during prophase 1

Answer 22

• chromatin condenses
• nuclear envelope breaks down and spindle fibres made from centrioles
• chromosomes pair in homologous pairs
• crossing over between non-sister chromatids occur where alleles are exchanges

Question 23

what occurs during metaphase 1

Answer 23

• homologous chromosomes line at chromosomes line at equator to spindle the centromeres at the sides of the cell
• pairs are arranged randomly

Question 24

what occurs during anaphase 1

Answer 24

• Homologous chromosomes pulls apart by motor proteins
  (independent assortment)
• each chromosome still has two chromatids

Question 25

what occurs during telophase 1

Answer 25

• nuclear envelop forms around chromosomes and cytokinesis may occur
• cells go into short interphase

Question 26

what occurs during prophase 2

Answer 26

• chromatin condenses
• nuclear envelope breaks down and spindle fibres made from centrioles
• chromatids are different due to crossing over in prophase 1

Question 27

what occurs during metaphase 2

Answer 27

• chromosomes line at equator to spindle by centromeres
• chromatids randomly arranged

Question 28

what occurs during anaphase 2

Answer 28

• centromere divides and chromatids pulled apart by motor proteins
• chromatids randomly segregated ( independent assortment)

Question 29

what occurs during telophase 2

Answer 29

• nuclear envelope forms around chromosomes and cytokinesis occurs
• 4 cells made in total as each cell from meiosis 1 divides.

Question 30

when is genetic variation achieved in meiosis

Answer 30

• crossing over of chromatids ( pairs of chromosomes line up and exchange some of there genetic material)
  occurs in prophase 1

Question 31

how are erythrocytes specialised for its function

Answer 31

• red blood cells - used to carry oxygen around the body
  specialised - no nucleus, mitochondria or golgi, for more space
  function - allows for more space for oxygen
  specialised - packed with lots of haemoglobin
  function - to store more oxygen
  specialised - bioconcave shape
  function - increases surface area to volume ratio, which makes gas exchange more efficient

Question 32

how are neutrophils specialised for its function

Answer 32

white blood cells - specialised to engulf and destroy pathogens
specialised - contains lots of lysosome which is a digestive enzyme
function - the digestive enzyme is able to break down the engulfed particle
specialised - flexible
function - easier to engulf larger particles

Question 33

how are squamous epithelial cells specialised for its function

Answer 33

a cell which is specialised for rapid diffusion
specialised - thin, flat smooth surface
function - this increases the rate of diffusion due to a short diffusion distance

Question 34

how are ciliated epithelial cells specialised for its function

Answer 34

a cell used to sweep dirt and debris out of the body
specialised - has a lot of cilia
function - lots of cilia make it easier to sweep the dirt and debris out of the body

Question 35

How are sperm cells specialised for its function

Answer 35

specialised - contains lots of mitochondria
function - to provide energy/ATP for movement
specialised - specialised lysosome in the acrosome of the sperm
function - the digestive enzyme is able to break down/digest the protective jelly coat of the egg cell.
specialised - stream lined body and flagellum
function - to move more quickly towards the egg cells

Question 36

how are palisade cells specialised for its function

Answer 36

a cell used to carry out photosynthesis
specialised - contains lots of chloroplast
function - chloroplast contains chlorophyll which changes light into energy

Question 37

how are root hairs cell specialised for its function

Answer 37

a cell which is used for the uptake of ions and water from the soil.
specialised - a large surface area
function - to increase the rate of absorption

Question 38

How are guard cells specialised for its function

Answer 38

used for the control of opening and closing of the stomata
specialised - it uses pressure to open and close the stomata
function - the guard cell is able to control the amount of water and solutes within them