Cells

Question 1

whats the difference between mitosis and cytokinesis

Answer 1

mitosis- divisionj of nucleus cytokinesis0 division of cell

Question 2

What are the stages of mitosis

Answer 2

1) INTERPHASE -G1= proteins synthesises and cell grows larger
- S phase= DNA replication G2= additional growth
2) PROPHASE -chromosomes condense and become visible
- 2 chromatids connected by centromere -nuclear envelope breaks down -mitotic spindle forms
3) METAPHASE -chromosomes line at equator -spindles attach to centromere
4) ANAPHASE -sister chromatids separate at the centromere and are pulled apart to opp poles of cell by spindles
5) TELOPHASE -spindle disappears
- nuclear envelope reforms
- chromosomes decondense
- cytokinesis occurs so cell division

Question 3

what happens if mitosis goes wrong

Answer 3

-mutations can cause uncontrolled cell division so lead to formation of tumours -many cancer treatments are directed to controlling rates of cell division

Question 4

desrcribe binary fission

Answer 4

-circular DNA and plasmids replicated -cytoplasm divides -have a single copy of circular DNA and variable plasmid copy numbers

Question 5

Answer 5

• push hard so specimen is squashed so thin
• not pushing the cover slip sideways ensures that chromosomes arent broken open

Question 6

Answer 6

• yes because the chromosomes are at opposite poles of the spindle
• teh chromosomes are y shaped, showing that thesister chromatids have been pulled apart at their centromeres

Question 7

Answer 7

6/200= 0.03

16 hours= 960 minutes

0.03 x 960= 28.8

=29 hours

Question 8

Answer 8

d, c ,b, e, a

Question 9

Answer 9

reason- mitosis occurs teh most at this region

reason- to allow light through// make layer thin

Question 11

E.coli has no cholesterol in its cell surface membrane. Despite thus, the cell maintains a constant shape. Explain why?

Answer 11

cell unable to change shape because cell has cell wall which is rigid due to murein

Question 13

What is a eukaryotic cell?

Answer 13

-A cell which has membrane-bound organelles ;like plant and animals cells

Question 14

Describe the Cell surface membrane

Answer 14

• A phospholipid bilayer
• function: extracellular substances enter and waste/ secretion exit the cell
• may sometimes require Active Transport or membrane proteins

Question 15

Describe the nucleus

Answer 15

• double membrane
• contains chromosomes, consisting of protein-bound linear DNA
• one or more nucleoli (rRNA synthesis)

Question 16

Describe the mitochondria

Answer 16

• double-membrane
• folds called cristae (large SA)
• function: site of aerobic respiration (ATP production)

Question 17

Describe chloroplasts

Answer 17

• site for photosynthesis
• includes thylakoids, stroma, outer membrane, inner membrane, lamella, granum

Question 18

Describe the Golgi Apparatus

Answer 18

-modifies proteins’-role in packaging and secretion of proteins

Question 19

Describe what lysomomes are

Answer 19

• small, membraneous vesicles
• get rid of unwanted cells organelles
• contain lysozymes which destroy pathogens

Question 20

Describe ribosomes

Answer 20

• round shaped organelles that synthesise protein
• some attach to the surface of the endoplasmic reticulum

Describe the Rough Endoplasmic Reticulum (RER)

• Has a large number of ribosomes attached to the surface
• Synthesises and makes changes to proteins

Question 21

Describe the SER

Answer 21

-site for lipid synthesis, toxin modification and glycogenesis