M2: ch 2 - basic components of living systems

Question 1

what are the types of sample preparation

Answer 1

• dry mount
• wet mount
• squash slides
• smear slides

Question 2

how is a dry mount sample prepared + examples

Answer 2

• solid specimens viewed whole or cut into very thin slices with a sharp blade –> sectioning
• specimen placed on centre of slide + cover slip placed over sample
• hair, pollen, dust, muscle tissue, plants, insect parts

Question 3

how is a wet mount sample prepared + examples

Answer 3

• specimens are suspended in a liquid, such as water or an immersion oil
• cover slip is placed at an angle
• aquatic samples, other living organisms

Question 4

how is a squash slide sample prepared + examples

Answer 4

• wet mount first prepared
• lens tissue used to gently press down the cover slip
• potential damage to cover slip can be avoided by squashing the sample between two microscopic slides
• squash slides is a good technique for soft samples
• care needs to be taken that the cover slip isn’t broken when being pressed
• root tip squashes - to look at cell division

Question 5

how are smear slides prepared + examples

Answer 5

• edge of a slide used to smear the sample –> creating a thin, even coating, on another slide
• cover slip then placed over sample
• blood - to view blood cells

Question 6

why is staining used

Answer 6

• to make components of sample more visible + easier to distinguish the different components, as many specimens such as cells + tissue sections are relatively colourless

Question 7

what is magnification

Answer 7

how many times larger the image is than the actual size of the specimen (object)

Question 8

what is resolution

Answer 8

the ability to distinguish between two objects closely together
- the minimum distance at which 2 points can be distinguished, from the other

Question 9

what is the calculation for magnification

Answer 9

magnification = image size/actual size

Question 10

what is the calculation for actual size

Answer 10

actual size = image size/magnification

Question 11

what is the calculation for image size

Answer 11

image size = magnification x actual size

Question 12

what are the two types of electron microscope

Answer 12

• transmission electron microscope (TEM)
• scanning electron microscope (SEM)

Question 13

what are features of a TEM

Answer 13

• electron passes through + around the specimen, giving some contrast
• image is 2D
• magnification of x500,000
• looks within the cell

Question 14

what are features of a SEM

Answer 14

• electron doesn’t go through or pass around the sample but reflects off
• image is 3D
• magnification of x100,000
• looks on surface of cell

Question 15

compare a light microscope + an electron microscope

Answer 15

• L = inexpensive to buy + operate
  E = expensive to buy + operate
• L = small + portable
  E = large + needs to be installed
• L = simple sample preparation
  E = complex sample preparation
• L = sample preparation doesn’t usually lead to distortion
  E = sample preparation often distorts material + produces artefacts
• L = vacuum isn’t required
  E = vacuum is required
• L = natural colour of sample seen (or stains used)
  E = black + white images produced (can be coloured digitally)
• L = up to x1,500 - x2,000 magnification
  E = up to x500,000 magnification
• L = specimens can be living or dead
  E = specimens are dead
• L = resolution is very poor
  E = resolution is 1,000 times more

Question 16

what are the advantages of electron microscopes

Answer 16

• resolution is 0.2nm, 1,000 times more than light microscope
• we can see structured detailed images of organelles inside the cells
• SEM produces 3D images, that can uncover details of contorts + cellular tissue arrangement, can’t do with light microscope

Question 17

what are the disadvantages of electron microscopes

Answer 17

• sample has to be dead
• very expensive
• preparing slides + samples requires high levels of training + skill

Question 18

what is a eukaryote cell + examples

Answer 18

• DNA in a membrane bound nucleus, separate from the cytoplasm
• contain a large number of specialized, membrane-bound organelles
• animals, plants, fungi, protists

Question 19

what is the structure of a nucleus

Answer 19

• nucleus
• chromatin
• nucleolus
• nuclear envelope

Question 20

what is the function of the nucleus

Answer 20

• contains cells DNA
• site of DNA replication/transciption

Question 21

what is the function of chromatin

Answer 21

• consists of DNA + proteins, some of the proteins regulate the cell’s activity

Question 22

what is the function of the nucleolus

Answer 22

• site of ribosome synthesis (RNA synthesis)
• makes RNA which is made into ribosomes

Question 23

what is the function of the nuclear envelope

Answer 23

• double membrane bound organelle
• compartmentalizes DNA from the rest of the cells
• has nuclear pores which allow the exchange of substances in + out of the nucleus, + lets relatively large molecules pass through

Question 24

what is the function of mitochondria

Answer 24

site of aerobic respiration, to produce ATP

Question 25

what are the features of mitochondria

Answer 25

• double membrane bound
• inner layer folds inwards to form the cristae, which project into a liquid called the matrix
• larger SA of matrix means more reactions, so more ATP can be produced
• inner membrane coated in enzymes, which catalyses aerobic respiration - to produce ATP
• contains DNA + ribosomes
• may have started from the endosymbiotic theory