2.1.1 Cell structure Flashcards
resolution definition
ability to distinguish between two points on an image, smallest distance between 2 distinguishable points
magnification definition
size of an image compared to size of object
optical microscope pros
relatively cheap
easy to use
portable (use in field)
study whole living specimens
optical microscope magnification and resolution
x1500
200 nanometers
total magnification formula
total magnification = eyepiece lens magnifying power x objective lens magnifying power
photomicrograph definition
photograph of an image seen using an optical microscope
laser scanning microscopes
confocal microscopes
laser light scans object point by point and image produced by computer
depth selective
high resolution, high contrast
used in medical professions and biological research
how transmission electron microscope works
chemically fixed (dehydrated and in vacuum) and stained (metal salts) electrons pass through specimen and focused on screen / photographic plate forms 2D black/white image
transmission electron micrograph magnification and resolution
x500,000
0.05 nanometers
scanning electron microscope magnification and resolution
x100,000
10 nanometers
how scanning electron microscope works
chemically fixed (dehydrated and in vacuum) and stained (metal salts)
electrons cause secondary electrons to bounce off specimen (focused on to screen)
produces 3D black/white image
electron microscope cons
large (not portable)
very expensive
need great deal of skill and training to use
how to observe unstained specimens
light interference
dark background behind illuminated specimen
adjusting iris diaphragm to control illumination of specimen
useful for observing living specimens
stain definition
coloured chemicals that bind to molecules / structures in / on specimen
makes specimen easier to see
methylene blue
all-purpose stain
differential staining definition
coloured chemicals binding to specific structures / molecules on specimen
acetic orcein
stains DNA and chromosomes dark red
eosin
cytoplasm
Sudan red
stains lipids
iodine in potassium iodide solution
cellulose in cell walls yellow
starch granules blue/black (purple under microscope)
how specimens prepared in laboratory
dehydrating specimen
embedding in wax (prevents distortion during slicing)
special instrument used to make thin cliches (sections)
sections stained and mounted in special chemical to preserve them
formula between image size, actual size and total magnification
image size = total magnification x actual size
longitudinal definition
lengthways
transverse definition
crossways
oblique definition
slanting
eyepiece graticule definition
measuring device
placed in eyepiece
acts as ruler
stage micrometer definition
precise measuring device
small scale placed on microscope stage
used to calibrate value of eyepiece units at different magnifications
1mm
features of eukaryotic cells
nucleus (surrounded by nuclear envelope, containing DNA organised and wound into linear chromosomes) nucleolus within nucleus cytoplasm cytoskeleton plasma membrane membrane-bound organelles smell vesicles ribosomes
organelle definition
sub-cellular structure that performs one or more specific jobs
membrane-bound meaning
covered by membrane that keeps organelle separate from rest of cell
nucleus structure and function
surrounded by nuclear envelope chromatin around nucleolus nucleolus at centre (no membrane) control centre of cell stores genome transmits genetic information provides instruction for protein synthesis
nuclear envelope structure and function
double membrane
separates contents of nuclear from rest of cell
pores allow dissolved substances (e.g. steroid hormones) ribosomes and mRNA through
nucleolus function
where ribosomes made
contains RNA
chromatin structure and function
consists of DNA wound around histone proteins
when not dividing, spread out or extended
when about to divide, chromatin condenses and coils into chromosomes
makes up nearly all organism’s genome
rough endoplasmic reticulum structure
system of membranes, continuous with nuclear membrane
contains cisternae
covered with ribosomes
made up of phospholipid bilayer
rough endoplasmic reticulum function
compartmentalisation (maintains specific conditions needed in RER)
separating proteins from cell cytoplasm
holds ribosomes in place
packaging proteins into transport vesicles
smooth endoplasmic reticulum structure
system of membranes, continuous with nuclear membrane
contains fluid-filled cavities (cisternae)
no ribosomes on its surface
smooth endoplasmic reticulum function
contains enzymes involved with lipid metabolism (synthesis of cholesterol, (phospho)lipids, steroid hormones)
involved with synthesis and transport of lipids
Golgi apparatus structure
stack of membrane-bound flattened sacs
secretory vesicles bring materials to and from Golgi apparatus
Golgi apparatus function
modifies proteins (adds sugar/lipids to make glyco/lipoproteins, folds into 3D shape) protein packaged into vesicles (pinched off then stored in cell or moved to be part of plasma membrane or exported outside of cell)
mitochondria structure
spherical, rod-shaped or branched 2-5 micrometers long surrounded by two membranes (fluid-filled space in between) inner membrane folded into cristae inner part = fluid-filled matrix
mitochondria function
site of ATP production / aerobic respiration (doesn’t produce ATP!!)
self-replicating
abundant in cells with more metabolic activity
chloroplast structure
4-10 micrometers long
only found in plant cells and some protoctists
surrounded by double membrane
inner membrane = continuous with stacks of flattened membrane sacs containing chlorophyll (thylakoids)
thylakoid stack = granum
fluid-filled matrix = stroma
contains loops of DNA and starch granes
chloroplast function
site of photosynthesis
first stage = light energy trapped by chlorophyll to make ATP (in granum)
water split to supply hydrogen ions
second stage = hydrogen reduces carbon dioxide (energy from ATP) to form carbohydrates (in stroma)
vacuole structure
surrounded by membrane (tonoplast)
contains fluid
vacuole function
only plant cells have large permanent vacuole
filled with water and solutes
maintains cell stability (pushes against cell wall, makes cell turgid)
helps support plant if all cells turgid
lysosome structure
small bags formed from Golgi apparatus surrounded by single membrane contains hydrolytic (digestive) enzymes abundant in phagocytic cells (ingest and digest invading pathogens)
lysosome function
separates hydrolyitc enzymes from rest of cell
can engulf and digest old cell organelles and foreign matter
returns digested components to cell for reuse
cilia and undulipodia structure
protrusion from cell
surrounded by cell surface membrane
contain microtubules
formed from centrioles
cilia and undulipodia function
movement of cell
movement of mucus
can contain receptors to detect signals from environment
organelles without membranes
ribosomes
centrioles cytoskeleton
cell wall
ribosome structure
small (20nm)
spherical
made of ribosomal RNA
made in nucleolus (2 separate sub units then reassemble in cytoplasm)
some free in cytoplasm, others attached to ribosome
ribosome function
protein synthesis
free in cytoplasm = protein for inside cell
bound to RER = mainly for proteins exported out of cell
centriole structure
two bundles of microtubules at right angle to each other
microtubules (tubulin protein subunits) form cylinder to create bundle
absent from cells of (higher) plants
centriole function
spindle forms from centrioles before cell division
centrioles multiply and line up beneath cell surface membrane
microtubules sprout outwards from each centriole to form cilium or undulipodium
cellulose cell wall structure
mesh of bundles of cellulose fibres
cellulose cell wall function
provide strength and support (of cell and whole plant)
maintains shape of cell
permeable (allows solutions through)
prevents plant cells from bursting when turgid
fungal cell walls made of chitin
cytoskeleton structure
network of protein structures in cytoplasm
consists of:
-rod-like microfilaments made up of subunits of actin. polymers of actin (7nm diameter)
-intermediate filaments made up of variety of proteins (10nm diameter)
-straight, cylindrical microtubules (18-30 nm diameter)
-cystoskeletal motor proteins (myosins, kinesins, dyneins) molecular motors. enzymes that can bind to and allow hydrolysis of ATP as energy source)
cytoskeleton function
microfilaments give support and mechanical strength, keeps shape stable and allows cell movement
microtubules provide shape and support, helps substances and organelles to move in cell (forms spindle fibres and track where motor proteins walk on)
intermediate filaments anchor nucleus
also extend between cells in some tissue for cell-cell signalling and adhering to basement membrane (stabilising tissues)
making and secreting protein method
gene (in chromatin) with instructions for protein is transcribed onto mRNA
mRNA copied and exits nucleus via pores to ribosomes on RER
instructions translated and protein assembled
protein molecules pass into and through cisternae and hollow sacs of RER
vesicles with protein within pinched off (by microtubules and motor proteins) and passed to Golgi apparatus
vesicles fuse with Golgi apparatus for protein modification / packaging
vesicles pinched off Golgi apparatus and go to plasma membrane
vesicles fuse to plasma membrane and protein released to outside of cell (exocytosis, requires energy)
prokaryote structures
plasma membrane cytoplasm smaller ribosomes DNA and RNA (plasmid and nucleoid) less developed cytoskeleton cell wall (peptidoglycan) waxy capsule flagella pili
