2.1 Cell Structure ✓

prokaryote

photograph of image seen using electron microscope

number of times larger image appears compared to size of object

photograph of image seen using optical microscope

clarity of image (higher resolution= clearer image)

linear

specimen maginfied x100 appears 100 x longer and wider than it really is

-relatively cheap
-easy to use
-portable (use in field + lab)
-can study whole living specimens

wavelength of visiblelight 400-700nm so structures closer than 200nm appear as 1 object

magnification= image size/ actual size

total mag= mag power of objective lens x mag power of eyepiece lens

1) specimen on slide + clipped in place
2) rotate nosepiece so lowest power objective lens over specimen
3) adjust coarse focus knob until image clear in focus
4) adjust iris diaphragm for optimum light
5) rotate nosepiece bringing next objective lens over specimen and use fine focus knob to focus
6) repeat step 5 using next objective lens

confocal microscope

-in medical profession to give swift diagnosis and earlier more effective treatment
-biological research

beam of electrons have smaller wavelength (0.004nm)

chemically fixed by dehydration and stain (metal salts)

-2D
-black + white
-very high mag

-3D
-relatively high mag (more than optical less than SEM)
-black + white (but colour can be added)

-placed in vaccum
-often coated with fine film of metal

-large + expensive to use
-need skill + training to use
-specimens have to be dead
-stains potentially hazardous to user

-high resolution
-high contrast
-depth selectivity so can focus on structures at different depths (whole living specimens or cells)

-light interference instead of light absorption
-dark background against which illuminated specimen shows up

stain bonds to specific cell structures staining each structure differently

-dehydrate
-embedded in wax to prevent distortion while slicing
-special instrument use to make sections (thin slices)
-stained + mounted in special chemical to preserve

measuring device placed in eyepiece and acts as ruler when viewing object

precise measuring device placed on microscope stage and used to calibrate value of eyepiece divisions at different mag

1mm long

1) insert eyepiece graticule into eyepiece
2) place stage graticule on stage + bring into focus
3) align graticules and check value of 1 eyepiece division
4) use this ratio to measure images in microscope

double membrane with pores surrounding nucleus

RNA

no

genetic material consisting of DNA wound around histone proteins

spread out/ extended

condensed/ coiled tightly into chromosomes

separate contents of nucleus and rest of cell

where outer and inner membrane fuse

-messenger RNA
-steroid hormones

nucleolus

system of membranes coated in ribosomes, containing cisternae that are continuous with nuclear membrane

-intracellular transport system: cisternae form channels used for transportation around cell
-provides large SA for ribosomes + proteins then actively pass through membrane into cisternae to be transported to golgi apparatus

system of membranes, containing cisternae that are continuous with nuclear membrane (no ribosome coating)

-contains enzymes for catalysing lipid metabolism reactions
-absorption, synthesis and transport of lipids

-synthesis of cholesterol
-synthesis of lipids/ phospholipids
-synthesis of steroid hormones

stack of membrane-bound flattened sacs

-protein modification
-proteins packaged into vesicles + pinched off

-add sugar to make glycoproteins
-add lipid molecules to make lipoproteins
-folded into their 3D shape

-stored in cell
-moved to plasma membrane to be incorporated into it or exported out cell

fluid-filled cavities used for transportation

spherical, rod-shaped or branched

-2 membranes with fluid filled space between
-inner membrane folded into cristae
-inner part is fluid-filled matrix

site of ATP production during respiration

self replicate and make more

-double membrane
-inner membrane continuous with thylakoids (stacks of flattened membrane sacs) which contains chlorophyll
-fluid filled matrix (stroma)
-contains loops of DNA and starch grains

stack/ pile of thylakoids

photosynthesis

1. light energy trapped by chlorophyll + used to make ATP (in grana), water also split for H ions
2. hydrogen reduces CO2 using energy from ATP to make carbs (in stroma)

vacuole membrane

-filled with water + solutes
-maintains stability (turgid cells support plant)

golgi apparatus

-keep powerful hydrolytic enzymes seperate from rest of cell
-engulf old cell organelles + foreign matter, digest and return components to be reused

protrusions from cell surrounded by cell surface membrane contining microtubules

centrioles

-cilia in airways
-one cilium on cells to detect signals about environment with receptors
-undulipodium on sperm enable movement

ribosomal RNA

made in nucleolous as 2 subunits, pass nuclear envelope and combine in cytoplasm

synthesising proteins that are exported out of cell

synthesise proteins used in cell

2 bundles of microtubules at right angles to each other

tubulin protein subunits

-before cell division, forms spindle of tubulin threads which chromosomes attach to and motor proteins walk along pulling chromosomes to opposite ends
-form cilia + undulipodia

network of protein structures in cytoplasm consisting of:
-rod-like microfilaments
-intermediate filaments
-straight, cylindrical microtubules
-cytoskeleton motor proteins

-support + mechanical strength
-keep cells shape stable
-allow cell movement

-shape and support to cells
-help substances + organelles move through cytoplasm by forming a track which motor proteins walk and drag organelles along
-form spindle before cell divides
-make up cilia, undulipodia + centrioles

-anchor nucleuswithin cytoplasm
-extend between cells in some tissues enabling cell-cell signalling, stabilising tissues

-prevent cells bursting
-strength+ support
-maintain cell shape
-permeable to allow solutions through

-much smaller
-less well-developed cytoskeleton with no centrioles
-no nucleus
-no membrane-bound organelles
-wall of peptidoglycan not cellulose
-smaller ribosomes
-naked DNA not wound around histone proteins but floats free in cyriplasm in loop (not linear)

-protective waxy capsule around cell wall
-small DNA loops (plasmids)
-flagella (whip like projections for movement)
-pili (small hair like projections for bacteria to adhere to host cells or eachother and allow passage for DNA transfer)

binary fission (DNA copied before division so each cells has large loop and plasmids)