2.1.1 Cell Structure

Question 1

cell ultrastructure

Answer 1

the detail revealed by the electron microscope, structures found inside the cell are called organelles

Question 2

division of labour

Answer 2

each organelle has a specific role within the cell and they work together to aid the cells survival

Question 3

how does a light microscope work

Answer 3

uses visible light to look at a small sample in colour and the sample can be living

Question 4

stain defenition

Answer 4

coloured chemicals that bind to molecules in a specimen

Question 5

uses of stains

Answer 5

• makes cells visible
• increases contrast as different organelles take up
  different amounts of the stain
• details can be seen
• organelles identified

Question 6

examples of stains

Answer 6

iodine, eosin, acidified phloroglucinol, acetic orcein, light green

Question 7

conversion rates of units

Answer 7

1m = 1000mm
1mm = 1000micrometres
1micrometre = 1000nm

Question 8

magnification

Answer 8

the number of times larger the image is compared with the actual size of an object

Question 9

resolution

Answer 9

the ability to distinguish between two separate points that are very close together giving more detail and clarity

Question 10

eyepiece graticule

Answer 10

printed scale in the microscope which is divided into 100 epu (eyepiece units)

Question 11

stage micrometer

Answer 11

a microscope slide that has a fine and accurate scale engraved on it, is usually 1mm long and divided into 100 units so each division is 10micrometres

Question 12

how to calibrate the eyepiece graticule

Answer 12

1) place the stage micrometer on the microscope and focus on low power
2) line up stage micrometer and eyepiece graticule
3) count the divisions on the eyepiece graticule that correspond to 1mm on the stage micrometer
4) calculate distance in micrometres of one division on the eyepiece graticule
5) repeat for medium and high power

Question 13

how to draw cells

Answer 13

1) no shading
2) PENCIL
3) straight label lines using pencil and ruler
4) clear annotations
5) no shading and clear lines
6) include scale bar if appropriate

Question 14

how does a laser scanning microscope work

Answer 14

a laser is pointed at the sample and scans across giving a 3D image showing depth (useful in medicine)

Question 15

how does a transmission electron microscope (TEM) work

Answer 15

sample is first dried in ethanol and coated in gold, then electron beams pass through the sample, focused by magnets giving 2D surface images showing internal structures

Question 16

how does a scanning electron microscope (SEM) work

Answer 16

electrons bounce off the surface of the sample providing a 3D surface image

Question 17

resolution of light/tem/sem

Answer 17

light - 200nm
sem - 2nm
tem - 0.2nm

Question 18

maximum magnification of light/sem/tem

Answer 18

light - x2000
sem - x200,000
tem - x2,000,000

Question 19

nucleus structure and function

Answer 19

double membrane bound nuclear envelope - encloses DNA inside of nucleus
nuclear pores - mRNA leaves via them
nucleoplasm - contains chromatin
nucleolus - manufactures ribosomes
outer membrane is continuous with rough er - allows easy transport of substances

Question 20

endoplasmic reticulum structure and function

Answer 20

a system of hollow tubes and sacs - allows trasnport within a cell
rough er has ribosomes which synthesise proteins
smooth er has no ribosomes and synthesises lipids and steroids
cisternae - gaps inside the hollow tubes and sacs

Question 21

ribosome structure and function

Answer 21

two subunits of rRNA and protein which provide binding site for mRNA and contain enzymes
22nm (80S) in eukaryotic cells
18nm (70S) in prokaryotic/chloroplasts/mitochondria
found free in the cytoplasm and attached to the rer as ribosomes can move along mRNA

Question 22

golgi apparatus structure and function

Answer 22

flattened membrane bound cavities called cisternae stacked in top of eachother which modify and packages carbs and proteins into vesicles
produce lysosomes and secretory vesicles which fuse with plasma membrane for excretion

Question 23

lysosome structure and function

Answer 23

vesicles which contain hydrolytic enzymes

isolate potentially harmful enzymes and break down material ingested by WBC, break down old and dead cells

Question 24

mitochondria structure and function

Answer 24

double membrane bound which isolates reactions in aerobic respiration for the production of ATP
inner membrane folds to form cristae to increase sa for enzymes to be attached
matrix contains:
-18nm ribosomes (for proteinsynthesis)
-DNA (codes for proteins)
-enzymes (aerobic respiration)

Question 25

chloroplasts structure and function

Answer 25

``` double membrane bound to isolate photosynthetic reactions membrane bound sacs called thylakoids stacked into grana connected by lamellae to increase sa for chlorophyll to attach stroma contains: -enzymes (photosynthetic reactions) -starch grains (carbohydrate store) - 18nm ribosomes (proteinsynthesis) -DNA (codes for proteinsynthesis) -lipid droplets (for membranes) ```

Question 26

centrioles structure and function

Answer 26

two centrioles found in all animal cells perpendicular to eachother next to the nucleus, composed of 9 sets of 3 microtubules found in: -algae -fungi -NOT plant cells form the spindle fibres during nuclear division to control the separation of chromatids and chromosomes

Question 27

cytoskeleton structure and function

Answer 27

-microtubules (fine hollow tubes) -microfilaments (small solid protein fibres) enable movement of vesicles, support cell organelle position, strengthen cells and help to maintain shape

Question 28

flagella and cilia structure and function

Answer 28

2 microtubules surrounded by 9 pairs of microtubules, brings about movement eukaryotes: undulipodia prokaryotes: flagellum

Question 29

vacuoles structure and function

Answer 29

common and large in plant cells, membrane is called the tonoplast maintain turgor for support and used for storage of cell sap/sugars/pigments etc

Question 30

plant cell walls structure and function

Answer 30

secreted by the living cell, rigid and permeable, made of cellulose, modified by lignin, contains pores which are penetrated by plasmodsmata, the middle lamella cements cells together which is composed of pectic substances - support - protection - prevents osmotic bursting

Question 31

structures always present in prokaryotes

Answer 31

- cytoskeleton (protein fibres) - plasma membrane (controls what enters/leaves the cell) - cytoplasm (site of anaerobic respiration) - ribosome (18nm) - circular DNA (naked DNA) - nucleoid (area where DNA found) - cell wall (made of murien)

Question 32

structures sometimes present in prokaryotes

Answer 32

- flagellum (movement in corkscrew motion) - infolding of plasma membrane (nitrogen fixation/form photosynthetic membrane) - mesosome (aerobic respiration) - plasmid (small circle of DNA) - pili (attachment to other cells/reproduction)