cell structure and division

Question 1

What is the cell cycle?

Answer 1

A period of cell growth, cell replication and cell division.

Question 2

How do scanning electron microscopes work?

Answer 2

scan beam of electrons across specimen
knocks off electrons from the specimen, which are gathered in a cathode-ray tube to form an image
show the surface of specimen
+ 3D images
+ Used on thick specimens
- Give lower resolutions

Question 3

Name and describe the process by which prokaryotic cells reproduce?

Answer 3

BINARY FISSION
1. Circular dna and plasmids replicate
2. Cell gets bigger and the dna moves to opposite poles
3. Cytoplasm begins to divide
4. Cytoplasm divides
5. 2 daughter cells produced with one copy of the circular dna

Question 4

What is cancer?

Answer 4

Mutation in a gene that controls cell division so the cell grows at an uncontrollable rate forming a tumour

Question 5

How do transmission electron microscopes work?

Answer 5

electromagnets to focus on a beam of electrons, which is then transmitted through the specimen
denser parts of the specimen will absorb more electrons -> darker on image
+ high resolution images
- view specimen for a vacuum -> can’t view living organism
- only used on thin specimen

Question 6

What is the difference between magnification and resolution?

Answer 6

Magnification is how much bigger the actual image is than the specimen is whereas Resolution is how well a microscope can distinguish between two points that are close together.

Question 7

What happens during interphase?

Answer 7

cell dna unravelled and replicated
organelles replicated
ATP content increased

Question 8

What are the stages of mitosis called?

Answer 8

prophase
metaphase
anaphase
telophase
cytokinisis

Question 9

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical (light) microscope.

Answer 9

Obtain thin section (of plant tissue) and place on slide / float on drop of water;
Stain with / add iodine in potassium iodide.
Add drop of water to (glass) slide
Lower cover slip using mounted needle.

Question 10

What happens in anaphase?

Answer 10

centromeres divide (sister chromatids separate)
chromatids move to opposite poles

Question 11

What is the formula for calculating magnification of a microscope?

Answer 11

magnification = size of image / size of real object

Question 12

What is prophase?

Answer 12

chromosomes condense
nuclear envelope break down
chromosomes free in cytoplasm

Question 13

Where is murein used for in prokaryotic cells?

Answer 13

Cell wall

Question 14

What is mitosis needed for?

Answer 14

growth of multicellular organisms
repairing damaged tissues

Question 15

what is the structure of chromosomes?

Answer 15

PICTURE

Question 16

Eukaryotic cells produce and release proteins.
Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.
Do not include details of transcription and translation in your answer.

Answer 16

Ribosomes/rough endoplasmic reticulum produce (protein);
Mitochondria produce ATP (for protein synthesis);
Golgi apparatus package/modify;
Vesicles transport
(Vesicles) fuse with cell(-surface) membrane;

Question 17

What are the three factors that solution must have when homogenising the cell?

Answer 17

ice cold : reduce enzyme activity
isotonic : it should have the same concentration of chemicals as the cells being broken down,to prevent damage to the organelles through osmosis
buffer solution added : maintain PH

Question 18

How do viruses replicate?

Answer 18

Viruses attaches to host cell receptor proteins
Genetic material is released into the host cell
Genetic material & proteins are replicated by host cell machinery
Viral components assemble
Replicated viruses released from host cell

Question 19

what are the steps of cell fractionation?

Answer 19

1. Homogenisation
   - grinding cells in blender
   - break up plasma membranes
   - release organelles into solution
2. Filtration
   - homogenised cell solution
   filtered through a gauze to
   separate any large cell debris
3. Ultracentrifugation
   - contents put in centrifuge
   - heaviest form a pellet at
   bottom
   - lightest form a supernatant at
   top

organelles separated in order of mass (heavy to light)

nuclei, chloroplasts (plant), mitochondria, lysosomes, endoplasmic reticulum, ribosomes

Question 20

What happens in cytokinises?

Answer 20

cytoplasm divides

= two genetically identical daughter cells

Question 21

What happens in metaphase?

Answer 21

Chromosomes line up along middle of cell
Become attached to the spindle by centromere

Question 22

What is the structure of a virus?

Answer 22

PHOTO

Question 23

What happens in telephase?

Answer 23

Chromatids uncoil and become long
Become chromosomes
A nuclear envelope forms around each group of chromosomes