3: Cell Structure Flashcards
microscopes, eukaryotic, prokaryotic, virus, mitosis, cell cycle
magnification equation
image = actual size x magnification
What is resolution
minimum distance apart two objects can be in order to be distinguished
cell fractionation importance
to obtain large number of isolated organelles for studying structure and function of cells
Why put cell tissue into a cold buffered solution of the same water potential?
cold: to reduce enzyme activity that might break down organelles
buffered: so pH doesn’t fluctuate and alter organelle structure
same water pot: to prevent organelles bursting or shrinking as result of osmotic water loss/gain
Homogenation
cells broken up in homogeniser to release organelles from cells, filtered to remove complete cells and large debris
ultracentrifugation
cell fragments of homogenate seperated in a centrifuge. spins at high speed to produce centrifugal force, heaviest organelles forced to bottom of test tube, form pellet. Process repeated with leftover supernant at higher speeds.
Transmission Electron Microscope (TEM)
Electron beam onto thin specimen, absorbed or pass through, produce photomicrograph, 0.1nm resolution.
TEM limitations
- vacuum so not living specimen
- complex staining process and image not in colour
- extremely thin specimen
- image may be obstructed by artefacts
Scanning Electron Microscope
same as TEM, but specimens do not need to be extremely thin. electron beam passed back and forth in regular pattern, building up 3D image.
Calibrating eye piece graticule
line up graticule and stage micrometer scale.
Calculate length of divisions on graticule and therefore ratio
Eukaryotic cell structures
Nucleus
Mitochondria
Chloroplasts
Endoplasmic reticulum
Golgi apparatus
Lysosomes
80S Ribosomes
Cell wall
Vacuoles
functions of the nucleus
acts as control centre through manufacture of mRNA tRNA and therefore protein synthesis
retains genetic material of cell in form of DNA and chromosomes
manufactures rRNA and ribosomes
Mitochondria structure
double membrane, controls entry/exit
cristae, extension of inner memb, attachment of resp enzymes and proteins
matrix, contains proteins, lipids, ribosomes, DNA that control own protein production. contains most resp enzymes.
Mitochondria function
Site of aerobic resp (krebs and oxidative phosphorylation)
produce ATP
Chloroplast structure
Envelope- double plasma membrane
grana- light absorption stage, large surface area
thylakoids (chlorophyll)
stroma- 2nd stage of photosynthesis, contains starch grains, enzymes
contains DNA, ribosomes to manufacture proteins for PS
Rough endoplasmic reticulum
ribosomes on surface, provides large SA for protein/glycoprotein synthesis
path for transport of materials throughout cell (e.g proteins)
Smooth endoplasmic reticulum
tubular appearance, synthesise, store, transport lipids and carbs
Golgi apparatus structure & function
formed of stacks of cisternae & vesicles. transports, stores, modifies proteins and lipids (e.g adds carb to form glycoprotein, produces secretory enzymes, forms lysosomes)
Lysosomes function
hydrolyse material in phagocytic cells
release enzymes out cell by exocytosis
digest worn out organelles to be reused
break down dead cells, AUTOLYSIS
Ribosomes
80S eukaryotic
70S prokaryotic
site of protein synthesis
2 subunits rRNA and protein
Cell wall
microfibrils of cellulose, provides mechanical strength so cells don’t burst from pressure of osmosis, and to plant as a whole, allows water to pass along
Vacuole
single membrane, tonoplast. Keeps cell turgid. contains minerals, salts & AAs (temp food store), waste, pigment
