week 2

Question 1

doctrine of cell theory

Answer 1

all organisms are composed of one or more cells
cells are the smallest units of life and basis of organisation of all living organisms
cells arise only by division of a pre-existing cell

Question 2

diversity of cells

Answer 2

structure and biology of cells varies according to function and nature of organism through evolution
therefore can understand why different types of cell exist

Question 3

bright field

Answer 3

‘classic’ light microscopy
poor contrast
staining of cells often causes cell death
so cannot be used on live cells

Question 4

phase contrast

Answer 4

uses differences in refractive index of cell components to improve contrast
good for live cells

Question 5

differential interference contrast

Answer 5

utilises rate of change in refractive index
produces apparent 3D images

Question 6

fluorescence microscopy

Answer 6

specimen stained with fluorescent dye/ protein and excited with UV light
produces high contrast against dark background
use of green fluorescent protein (GFP) from jellyfish

Question 7

section

Answer 7

often necessary to prepare when examining tissues
thin slices (approx up to 10micrometres depth) prepared by fixation, embedding, sectioning and staining

Question 8

confocal scanning light microscopy

Answer 8

modern method
allows examination of thicker specimens up to approx 300 micrometres depth
uses laser beam to scan successive single points in planes of specimen which is treated with fluorescent stain
each section image pooled to reconstruct 3D image
good for living cells

Question 9

transmission electron microscopy

Answer 9

electrons pass through very thin specimens
mag up to 1,000,000 x
specimens fixed, sectioned, dehydrated and stained with heavy metals

Question 10

TEM prep alt

Answer 10

specimen cryofixed and used in ‘freeze-fracture’ with heavy metal covering to reveal internal cell surfaces

Question 11

scanning electron microscopy

Answer 11

electron beam scanned over specimen and back scatter strikes a detector
produces 3D image
res= 10nm
mag up to 150,000 x
conventional samples fixed, dehydrated and coated with thin layer of metal, usually gold

Question 12

cryo-electron microscopy

Answer 12

less harsh method
uses deep frozen molecules in solution and more gentle electron beams to determine structure of biomolecules

Question 13

super- resolution microscopy

Answer 13

fluorescence based microscopy techniques overcoming traditional light resolution limit
allows resolution to 100nm

Question 14

atomic force microscopy

Answer 14

method to visualise surface at molecular scale
uses fine pointed tip linked to cantilever arm
can move up and down as it moves across surface
detects fine movement by reflected laser beam

Question 15

essential features of cells

Answer 15

exterior plasma membrane which separates cell from external medium
nuclear region with DNA genetic material
interior semifluid cytoplasm

Question 16

prokaryotic cell

Answer 16

bacteria
no nucleus
little internal organisation
0.5-2 microm diameter
too broad term- incl eubacteria and archaea

Question 17

eukaryotic cell

Answer 17

distinct nucleus
specialised internal organelles
unicellular or multicellular
5-20 microm diameter

Question 18

structural features of prokaryotes

Answer 18

plasma membrane at edge of cyto
rigid peptidoglycan cell wall
- gram pos have only exterior cell wall, GN have extra outer membrane with perioplasmic space
relatively simple undifferentiated cytoplasm
genomic DNA in nucleoid region- not separate from surrounding cytoplasm
plasmids contain DNA as well

Question 19

eukaryote cell features

Answer 19

plasma membrane at edge of cyt
dna contained in nucleus - separated from cytoplasm by membrane
cytoplasm compartmentalised with membrane-bound organelles
complex cytoskeleton maintains cell integrity

Question 20

animal cell constituents

Answer 20

nucleus
organelles (mitochondria, golgi, peroxisomes, RER, SER, small vacuoles,) ribosomes,
centrioles,
cytoskeleton

Question 21

plant cell constituents

Answer 21

nucleus
organelles (mitochondria, golgi, peroxisomes, RER/ SER, chloroplasts)
ribosomes
cytoskeleton
single, large vacuole
rigid cellulose cell wall

Question 22

movement in eukaryotes

Answer 22

flagella and cilia projections on surface allow propulsion in protists/ fungi
roles in vertebrates (airways/ ears)

Question 23

photosynthesis specialisation

Answer 23

high concentration of chloroplasts in plant cells exposed to light

Question 24

metabolism specialisation

Answer 24

adipose cells for fat storage
large lipid droplet
brown fat cells for hear production with mitochondria

Question 25

signalling specialisation

Answer 25

nerve cells have terminal dendrites and a long axon for electrical signals

Question 26

transport specialisation

Answer 26

RBC specialised for gas transport - no nucleus or organelles when mature, instead they are full of haemoglobin small and flexible

Question 27

reproduction specialisation

Answer 27

sperm have flagellum mushroom spores produced on gills from specialised 'basidia'

Question 28

cell boundaries

Answer 28

allows formation of semi-fluid cytoplasm, formation of specialised microenvironments with particular solutes/ cell process, segregation of harmful activities principle boundary= external plasma membrane

Question 29

structure of membranes

Answer 29

sheet like composed of lipids, proteins, carbohydrates in varying ratios common structure= 5-8nm lipid bilayer membrane lipids have hydrophilic head and hydrophobic tail, amphipathic

Question 30

key structural features of fluid mosaic model

Answer 30

self assembling lipid bilayer lipid molecules are fluid, allowing movement - proteins have more restricted movement asymmetry- different inner and outer lipid monolayers - flippase enzymes can switch lipids between layers integral proteins pass through bilayer

Question 31

membrane functions

Answer 31

semi- permeabile barrier- allows movement of small, non-polar molecules- allows maintenance of interior and compartmentalisation transporting solutes- integral proteins provide passage/ AT and can act as transport channels flexibility for cell movement/ division response to external signals via receptors in membranes intercellular communication via surface carbs conferring cell identity

Question 32

cell walls

Answer 32

bacteria have peptidoglycan CW for rigidity fungi have chitin plant cells have cellulose cell walls cell walls for strength/ support CW must have means to be permeable

Question 33

cell cortex

Answer 33

animal cells have protein network 'cell cortex' under plasma membrane RBC- spectrin meshwork attached to plasma membrane via anchor proteins provides support/ cell shape/ elasticity

Question 34

extracellular matrix

Answer 34

some cells have 'glycocalyx' exterior coating based on sugar molecules others have complex extracellular matrix

Question 35

extracellular matrix example

Answer 35

collagen fibres protecting cell surface from mechanical/ chemical damage provides cell identity 'clothing' for recognition