topic 2.1.6: cell division, cell diversity & cellular organisation

Question 1

outline the stages of meiosis 1

Answer 1

prophase: chromosomes line up in homologous pairs (crossing over at chiasmata)
metaphase: bivalents line up on metaphase plate (independent assortment)
anaphase: whole chromosomes pulled to poles
telophase: nuclear envelopes reform

Question 2

outline the stages of meiosis 2

Answer 2

prophase: chromosomes condense
metaphase: chromosomes line up in single file
anaphase: centromeres divide and chromatids pulled to poles
telophase: nuclear envelope reforms

Question 3

what changes occur when cambium cells differentiate into xylem cells?

Answer 3

deposition of lignin in walls, loss of cytoplasm, loss of end walls

Question 4

what changes occur when cambium cells differentiate into phloem cells?

Answer 4

reduction in cytoplasm vol, loss of some organelles, end walls into sieve plates

Question 5

what are the 3 stages of the cell cycle?

Answer 5

interphase (preparing for division)
mitosis (nucleus divides in two)
cytokinesis (cell divides)

Question 6

what are the 3 phases of interphase?

Answer 6

G1 (growth and new proteins for organelles)
S (DNA replication)
G2 (growth and DNA checks)

Question 7

what are the 3 checkpoints in the cell cycle?

Answer 7

G1 (chemicals needed and DNA damage)
G2 (DNA replication)
metaphase (chromosome attached to spindle)

Question 8

what happens during mitosis prophase?

Answer 8

chromosomes condense, centromeres join, NE breaks down, nucleolus disappears

Question 9

what happens during mitosis metaphase?

Answer 9

centrosomes reach poles, chromosomes line up, spindle fibres attach

Question 10

what happens during mitosis anaphase?

Answer 10

sister chromatids separate, spindles shorten to poles

Question 11

what happens during mitosis telophase?

Answer 11

chromatids decondense, NEs and nucleoli reform

Question 12

what is a centromere?

Answer 12

holds sister chromatids together

Question 13

what is a chiasma?

Answer 13

a point of contact between two non sister chromatids

Question 14

how are erythrocytes specialised?

Answer 14

biconcave disc (higher SA), no organelles, flexible

Question 15

how are neutrophils specialised?

Answer 15

flexible memb (engulf), many lysosomes (digest), multilobed nucleus (cell can deform to fit gaps)

Question 16

how are sperm cells specialised?

Answer 16

flagellum, lysozymes in head, many mitochondria

Question 17

how are squamous epithelial cells specialised?

Answer 17

thin (gas exchange), permeable (diffusion)

Question 18

how are ciliated epithelial cells specialised?

Answer 18

cilia

Question 19

how are palisade cells specialised?

Answer 19

chloroplasts, thin walls (CO2 diffusion), tall and thin (packed)

Question 20

how are root hair cells specialised?

Answer 20

root hair structures (SA), thin permeable wall (water and ions), mitochondria (AT)

Question 21

how are guard cells specialised?

Answer 21

pairs (stomata form between), become turgid in light (open for CO2), close when water lost, thick outer and thin inner walls (bend when turgid for gap)

Question 22

how is xylem tissue specialised?

Answer 22

made of dead cells with no end walls or organelles (cont tube), lignin in walls for structural support

Question 23

how is phloem tissue specialised?

Answer 23

columns of sieve tube elements and companion cells, STEs separated by sieve plates with holes

Question 24

how are xerophytes adapted to their environment?

Answer 24

rolled leaves to reduce sa, waxy cuticle prevents transpiration, sunken stomata, reduced number of stomata/ only open during night