Analysis Of Cell Components

Question 1

Why is magnification?

Answer 1

It’s how much bigger the image is than the specimen

Question 2

What is resolution?

Answer 2

• it’s how detailed the image is
• it’s also how well a microscope distinguishes between two points that are close together
• if a microscope can’t separate two objects increasing magnification won’t help

Question 3

What is an optical light microscope?

Answer 3

• they use light to form an image

- they have a maximum resolution of 0.2 micrometers

Question 4

What is an electron microscope?

Answer 4

• electrons are used to form images
• they have a higher resolution than optical microscopes so are more detailed
• they have a maximum resolution of 0.0002 micrometers
• maximum magnification is x1,500,000

Question 5

What is a transmutation electron microscope?

Answer 5

• TEM uses electromagnets to foci ur beams of electrons which is transmitted through a specimen
• denser parts of specimen absorb more electrons which make them look darker on the end image
• TEM have high resolutions

Question 6

How does a scanning electron microscope work?

Answer 6

• SEM scans a beam of electrons across a specimen
• the beam of electrons knocks off electrons from the specimen which see gathered in the cathode ray tube to form an image

Question 7

What is the first stage of preparing a temporary mount of a specimen on a slide?

Answer 7

• Pipette a small drop of water onto the slide

- use tweezers to place a thin section of your specimen on top of the water drop

Question 8

What is Homogenisation?

Answer 8

vibrate the cells or grind the cells up in a blender to break up the plasma membrane and release organelles into the solution

Question 9

What is filtration?

Answer 9

• the homogenised cell solution is filtered through a gauze to separate any large cell debris or tissue debris like connective tissue from the organelles
• the organelles are smaller than the debris so pass through the gauze

Question 10

What is ultracentrifugation?

Answer 10

• After filtration you are left with a solution with a mixture of organelles
• use ultracentrifugation to separate a particular organelle from the others

Question 11

What is the first stage of ultracentrifugation?

Answer 11

• The cell fragments are poured into a tube which is put into a centrifuge and spun at a low speed
• the heaviest organelles (nuclei) get flung to the bottom by the centrifuge
• they form a thick sediment at the bottom called a pellet the other organelle stay suspended in the fluid above called the supernatant

Question 12

What is the second stage of ultracentrifugation?

Answer 12

• The supernatant is drained off, poured into another tube and spun in the centrifuge at a higher speed
• the heaviest organelles (mitochondria) forms a pellet at the bottom of the tube
• the supernatant is drained off and spun in the centrifuge at an even higher speed

Question 13

What is the third stage of ultracentrifugation?

Answer 13

• This process is repeated at higher and higher speeds until all the organelles are separated out
• each time the pellet is made up of lighter and lighter organelles

Question 14

What can you see with an optical microscope?

Answer 14

• you can barely make out mitochondria

- you can see the nucleus

Question 15

What can’t you see with an optical microscope?

Answer 15

• ribosomes
• lysosomes
• endoplasmic reticulum

Question 16

What can you see with TEM microscopes?

Answer 16

• The internal structure of organelles like chloroplasts

- they can only be used on thin specimens

Question 17

What is the second stage of preparing a temporary mount of a specimen on a slide?

Answer 17

-add a drop of stain which highlights objects in the cell

Question 18

What stains are used in preparing a slide?

Answer 18

• eosin is used to make cytoplasm show up

- iodine in potassium iodine is used to stain starch grains in plant cells

Question 19

What is the third stage of preparing a temporary mount of a specimen on a slide?

Answer 19

• add a cover slip
• stand the slip upright on the slide next to the water droplet
• carefully tilt and lower it onto the specimen
• don’t let any air bubbles in

Question 20

What is a coverslip?

Answer 20

A small square of plastic that protects the specimen

Question 21

How should the solution be kept for homogenisation?

Answer 21

• The solution much be kept ice cold to reduce the activity of enzymes which break down organelles
• the solution should be kept isotonic to prevent damage to the organelles through osmosis
• a buffer solution should be added to maintain pH

Question 22

What does isotonic mean?

Answer 22

A solution with the same concentration of chemicals as the cells being broken down