2.1.1 Cell structure

Question 1

What is a light microscope?

Answer 1

-uses light that passes through thin specimen to reflect an image in the objective lens
- to look at whole cells and tissues

Question 2

What is the magnification and resolution of a light microscope?

Answer 2

magnification: 1500x
resolution: 200nm (0/2micromtr)

Question 3

What is the magnification and resolution of a transmission electron microscope?

Answer 3

magnification: 500,000x
resolution: 0.05nm

Question 4

What is the magnification and resolution of a scanning electron microscope?

Answer 4

magnification: 100,000x
resolution: 0.20nm

Question 4

How does an TEM work?

Answer 4

• passes beam of electrons through specimen
• specimen must be thin to prevent deflection of electrons
• denser parts of specimen absorb more electrons = appear darker = produces contrast

Question 4

Why are TEM used?

Answer 4

to look at organelle detail

Question 5

Why do TEM images appear different from each other?

Answer 5

The images have been cut along different planes/angles

Question 5

How do SEM work?

Answer 5

• the beam of electrons scan the surface of specimen
• the beam is bounced off the surface and the electrons are detected
• forming a 3D image = surface of specimens

Question 6

Why are SEM used?

Answer 6

to look at cell surface

Question 7

What are laser scanning confocal microscopes?

Answer 7

• specimen needs to be treated with fluorescent dye
• laser beam is reflected by the fluorescent dyes

Question 8

Why are laser scanning confocal microscopes used?

Answer 8

to look at an object at a certain depth within the cell

Question 9

What are the advantages of TEM?

Answer 9

high resolution images = more detail
internal structures to be seen e.g vesicles

Question 10

What are the disadvantages for TEM?

Answer 10

-only be viewed with very thin specimens
-cannot be used to observe live specimens (vacuum)
- length treatment to prepare = artefacts
- doesnt produced coloured image

Question 11

What are the advantages of light microscopes?

Answer 11

• see whole cells and tissues
• use live specimen
• view coloured image

Question 12

What are the disadvantages of light microscopes?

Answer 12

• low magnification
• low resolution

Question 13

What are the strengths of SEM?

Answer 13

• produce 3D image
• used on thick specimens

Question 14

What are the disadvantages of SEM?

Answer 14

• lower resolution than TEM
• cannot observe live specimens
• no colour image

Question 15

What are the advantages of light microscopes?

Answer 15

• used on thick specimens
• high resolution = observe cytoskeleton

Question 16

What are the disadvantages of laser scanning confocal microscope?

Answer 16

• slow process; takes a long time to obtain image
• laser has potential to cause photodamage to cells

Question 17

How do you prepare for light microscopes?

Answer 17

staining;
specimen becomes more visible e.g to see certain (named) organelles;
to improve contrast

Question 18

What does acetic orcein stain?

Answer 18

DNA - dark red

Question 19

What does Eosin stain?

Answer 19

cytoplasm - pink

Question 20

What does Sudan black stain?

Answer 20

membranes and other lipids - black

Question 21

What type of specimen needs to be prepared for a light microscope?

Answer 21

thin specimen,
thin sections allow light to pass through;
artefacts may occur

Question 22

What is magnification?

Answer 22

the number of times larger the image is in in comparison to the object

Question 23

What is resolution?

Answer 23

the ability to distinguish between very small structures that are close together; in detail;

Question 24

Draw the units diagram?

Answer 24

cm /10 mm x10 /1000 µm x 1000 /1000 nm x 1000

Question 25

What is found in the eyepeice?

Answer 25

eye piece graticule; used in calibration

Question 26

What is used to calibrate the eye piece graticule?

Answer 26

a stage micrometer

Question 27

What is the formula for magnification?

Answer 27

I/AM

Question 28

What is the function of the nucleus?

Answer 28

contains the cells DNA (chromatin)

Question 29

What is the function of nuclear pores?

Answer 29

- allows mRNA and ribosomes to travel out - allowing enzymes e.g DNA polymerase and signalling molecules to travel in

Question 30

What is the nucleolus?

Answer 30

dense part of nucleus = site of ribosome production

Question 31

What is the function of the nuclear envelope?

Answer 31

separates the nucleus from the cytoplasm

Question 32

What is the function of the rough endoplasmic reticulum?

Answer 32

flattened sacs of cisternae continuous from the nuclear envelope surface covered in ribosomes where protein synthesis occurs

Question 33

What is the function of the smooth endoplasmic reticulum?

Answer 33

dont have ribosomes on its surface lipid and hormone production occurs here

Question 34

What is the function of the golgi apparatus?

Answer 34

- stack of membrane bound flattened sacs - modifies, packages proteins into vesicles

Question 35

What is the function of a ribosome?

Answer 35

site of protein synthesis

Question 36

What is the function of the mitochondria?

Answer 36

produces ATP; made during aerobic respiration

Question 37

What is the function of lysosomes?

Answer 37

contain powerful digestive enzymes which are used to break down materials

Question 38

What is the function of a chloroplast?

Answer 38

site of photosynthesis

Question 39

What is the function of the cell surface membrane?

Answer 39

made out of phospholipid bilayer controls what enters and leaves the cells

Question 40

What is the function of centrioles?

Answer 40

take part in mitosis to form spindle fibres

Question 41

Where are centrioles not found?

Answer 41

in flowering plants and fungi

Question 42

What is the function of a cell wall?

Answer 42

provides structural support to cell

Question 43

What is the cell wall made of in plants?

Answer 43

celluose

Question 44

What is the cell wall made of in bacteria?

Answer 44

peptidoglycon

Question 45

What is the function of the flagella?

Answer 45

whole cell movement made of long microtubules; they contract

Question 46

What is the function of cillia?

Answer 46

hair like projections made from microtubules allow movement of substances over the cell surface

Question 47

How do organelles work together to produce proteins?

Answer 47

- nucleus produces mRNA - mRNA leaves nucleus via nuclear pores - mRNA attaches to ribosome in the cytoplasm/RER - once protein has been made by proteinsynthesis - proteins travels in vesicle and transported to golgi apparatus - protein is modified and packaged in vesicle (addition of carbohydrate) - moved towards cells surface membrane - released via exocytosis also; other organelle - mitochondria: provides ATP = needed for the cytoskeleton to contract and move vesicle

Question 48

What is the importance of the cytoskeleton?

Answer 48

whole cell support; movement of cilia and flagella; changing cell shape; moving organelles; movement of chromosomes;

Question 49

What type of ribosomes are found in prokaryotes?

Answer 49

70s

Question 50

What is the function of plasmids?

Answer 50

circular DNA; can be passed to bacteria to exchange genetic info - through pili to surrounding bacteria

Question 51

What type of DNA is found in prokaryotes?

Answer 51

circular

Question 52

What is the role of the flagella in prokaryotes?

Answer 52

used in movement of cell requires ATP

Question 53

What is the role of the mesosome?

Answer 53

ATP is produces at the infolded regions of cells membrane