cells

Question 1

animal cells

Answer 1

• cell membrane: regulates movement of substances in + out of cell
• nucleus: controls cell’s activities + pores allow RNA to move betw nucleus + cytoplasm
• ribosomes: site of protein synthesis
• mitochondria: site of aerobic respiration where ATP is produced
• golgi apparatus: processes + packages lipids + proteins + also makes lysosomes
• lysosomes: fuse w vesicles (phagosomes) to release lysozyme (hydrolytic enzyme) used to digest invading cells
• golgi vesicles: stores lipids + proteins made by the apparatus + transports them out the cell
• SER: synthesises + processed lipids
• RER: covered w ribosomes, folds + processes proteins made at ribosomes

Question 2

plant cells

Answer 2

• cell wall: supports cell + prevents it from changing shape
• vacuole: helps maintain pressure inside the cell + keep cell rigid
• chloroplasts: site of photosynthesis

Question 3

algal cells

Answer 3

same organelles as plant cells

Question 4

fungal cells

Answer 4

similar to plants cells BUT:
- have chitin cell wall instead of cellulose
- don’t photosynthesis so no chloroplasts

Question 5

bacteria (prokaryotic) cells

Answer 5

• cytoplasm has no membrane-bound organelles
• no nucleus - instead have free-floating circular DNA
• have plasmids - small loops of DNA
• smaller ribosomes than eukaryotic cells
• murein cell wall instead of cellulose
• capsule
• flagella - rotates to make the cell move

Question 6

how do prokaryotic
cells replicate

Answer 6

binary fission:
- circular DNA + plasmids replicate
- cell gets bigger + DNA loops move to opposite poles of the cell
- cytoplasm divides to create 2 daughter cells (each w 1 copy of circular DNA)

Question 7

viruses

Answer 7

• attachment proteins:
• capsid:
• **

Question 8

how do viruses replicate

Answer 8

• attachment proteins bind to complementary receptor proteins

Question 9

magnification

Answer 9

how many times larger the image is compared to the object

mag = size of image / size of real object

Question 10

resolution

Answer 10

how detailed the image is - how well a microscope distinguishes between 2 points close together

Question 11

optical/light vs electron microscopes

Answer 11

optical:
- beam of light condensed by glass to create image
- poorer resolution (longer wavelengths of light)
- lower magnification
- colour images
- living samples

electron:
- beam of electrons condensed by electromagnets to create image
- greater resolution (shorter wavelengths of light)
- higher magnification
- black & white images
- sample must be in a vaccum (dead)

Question 12

TEM vs SEM microscopes

Answer 12

TEM:
- beam of electrons transmitted through specimen
- denser areas absorb more electrons
- these areas appear darker in images
- high resolution
- can only be used on thin specimen

SEM:
- beam of electrons scanned across specimen
- this knocks off electrons from the specimen
- these are gathered to produce images
- images can be 3D
- lower resolution
- can be used on thick specimen

Question 13

cell fractionation

Answer 13

• homogenisation:
  ○ cell broken open to release organelles in solution which is kept:
  ☆ ice-cold - to reduce enzyme activity that may damage organelles
  ☆ isotonic - same WP so no osmosis to prevent organelles from bursting/shrivelling
  ☆ buffered - same pH to prevent damage to organelles
• filtration:
  ○ homogenised solution is filtered to remove large debris
• ultracentrifugation:
  ○ tube of filtered solution put into a centrifuge + spun at a low speed
  ○ most dense organelle form a pellet at the bottom of the tube, leaving a supernatent
  ○ supernatent is spun again at a higher speed in a separate test tube
  ○ process repeated until desired organelle is acquired

Question 14

what is mitosis and what is its importance?

Answer 14

type of cell division that produces 2 identical daughter cells, each w the same no of chromosomes as the parent cell

for growth, repair & differentiation

Question 15

stages of mitosis

Question 16

cancer