2.1)Cell structure Flashcards
define magnification
the # of times an image appears, compared to the real object
define resolution
-clarity of an image
-higher resolution=clearer image
what are the advantages of optical microscopes?
-cheap
-easy to use
-portable
-can be used to study whole specimen
what is the mag. on an optical microscope?
X1500~X2000
what is an advantage of an optical microscope?
-low resolution
-small organelles are not visible
equation for total mag.
mag. of objective lens X mag. of eyepiece lens
how do laser scanning microscopes work?
-laser light
-scan the object point by point
-using a computer assemble into 1 image
-display
what are advantages of a laser scanning microscope?
-high resolution
-high contrast
-able to focus on structure at different depths
-able to observe whole specimen
-used in medical professions=effective treatment
what is another name for laser scanning microscopes?
confocal microscopes
what are electron microscopes?
-use beam of fast travelling electrons
-at a screen=creates an image
-2 types
what are the 2 types of electron microscopes?
1.transmission electron microscopes (TEM)
2.scanning electron microscopes (SEM)
how do TEM work?
1.specimen is chemically dehydrated
2.beam of e- pass through electrons
3.some e- pass through
3.focus on a screen
what type of image do TEM produce?
-2D
-black and white
what mag. can TEM achieve?
2 million
how do SEM work?
1.whole specimen
2.secondary e- bounce of the specimens surface
3.focused onto a screen
–>specimen has to be placed in vacuum
–>coated with fine metal
what type of image is produced from an SEM?
-3D
-black and white (but false colour can be added)
what is the mag. of an SEM?
X15~X200,000
what are the disadvantages of electron microscopes?
-large
-expensive
-require skill to use
what are stains used for?
-coloured chemicals
-bind to molecules in specimen
-easy to see specimen
what are the steps to preparing a specimen?
-dehydrating
-embedding in wax=prevent distortion
-very thin slice using special instrument
what is the equation for mag. factor?
M=I/A
what is a graticule?
transparent with a small ruler, to measure the specimen
what are the features of a eukaryotic cell?
-nucleus=surrounded with nuclear envelope + contains DNA
-nucleolus=area in nucleus=contains RNA=ribosomes
-cytoplasm
-cytoskeleton=network of protein filaments=transport organelles + allow contraction of muscles
-plasma membrane
-membrane bound organelles=mitochondria, golgi
-small vesicles
-ribosomes=protein assembling
what are membrane bound organelles?
-covered by a separate membrane
-separate from rest of the cell
-not found in prokaryote cells
describe the structure of the nucleus
-nucleus=surrounded by double membrane=nuclear envelope–>have pores
-nucleolus=no membrane + contain RNA
-chromatin:
>genetic material
>DNA wound around histone proteins
>cell not dividing=spread out + extended
>cell dividing=condense + coil=chromosomes
describe the function of the nuclear envelope
-separate the contents of the nucleus from the rest of the cell
-outer + inner membranes fuse=dissolved substances can pass through
describe the function of the pores on the nuclear envelope
-allow larger substances to pass through
-e.g. mRNA to leave the nucleus
what is the function of the nucleus?
-control centre
-store the organism genome
-transmits genetic info
-instructions for protein synthesis
describe the structure of the endoplasmic reticulum (RER)?
-system of membranes
-fluid filled cavities with a nuclear membrane=CISTERNAE
-coated with ribosomes
what is the RER responsible for?
intracellular transport system
what does the cisternae do?
forms channels for transporting substances to move from one area to another
what does the RER provide for ribosomes?
-large S.A
-assemble AA into proteins
-proteins actively pass through the membrane inot cisternae
-transported to golgi apparatus
describe the structure of the smooth endoplasmic reticulum (SER)?
-system of membranes
-fluid filled cavities with a nuclear membrane=CISTERNAE
-NO RIBOSOMES
what is the function of the SER?
-enzymes that catalyse reactions involved with lipid metabolism
–>synthesis of cholesterol
–>synthesis of lipids
–>synthesis of hormones
-absorption, synthesis and transport of lipids in the gut
describe the structure of the golgi apparatus
-stack of membrane-bound flattened sacs
-secretory vesicles bring materials to + from the golgi apparatus
what is the function of the golgi apparatus?
-proteins are modified:
~adding sugar = glycoprotein
~adding lipid= lipoproteins
~folded into 3d shape
-proteins packaged into vesicles and pinched off:
~stored in cell
~moved to plasma membrane= used in plasma membrane or exported out of cell
describe the structure of mitochondria
-spherical or rod shaped
-2 membranes= highly folded into cristae
what is the function of mitochondria?
-site of ATP production during aerobic respiration
-self replicating
-a lot in cells with high metabolic activity
describe the structure of chloroplast
-large
-found only in plants
-surrounded by a double membrane
-inner membrane=filled with stacks of flattened membrane sacs= THYLAKOIDS
what do chloroplast contain?
loops of DNA and starch grains
what is the function of chloroplasts?
-site of photosynthesis
-energy is trapped in the grana
-hydrogen reduces CO2 in the stoma
-many chloroplast in the leaf (palisade mesophyll layer)
describe the structure of the vacuole
surrounded by membrane containing fluid=TONOPLAST
what is the function of the vacuole?
-only plants have large permanent vacuole
-filled with water and solutes
-maintain stability=fill with water=turgid=push against the wall=support
describe the structure of lysosomes
-small bags formed from the golgi
-single membrane
-contain powerful hydrolytic (digestive) enzymes
what is the function of lysosomes?
-keep the enzymes separate from the cell
-can engulf old organelles–> return to cell for reuse
describe the structure of the cilia
-protrusions from the cell
-surrounded by cell surface membrane
-formed from centrioles
what is the functions of cilia?
-epithelial cells=line your airways=push mucus away
-cells in body=1 cilium=antenna=receptors=detect signals
what is the only human cell that has an undulipodia?
-spermatozoon= sperm
-allow it to move
describe the structure of ribosomes?
-small + spherical
-ribosomal DNA
-made in the nucleolus
-remain free in cytoplasm
what is the function of ribosomes?
-synthesising proteins on RER= exported out the cell
-free in cytoplasm= proteins used in cell
describe the structure of centrioles
-2 bundles of microtubules at right angles
-made from tubulin
-cylinder
what is the function of the centrioles?
-before cell divides=spindle forms centrioles=chromosomes attach to the middle=motor proteins walk along the tubulin=pull chromosomes
-form cilia=centrioles multiply + line up= microtubules spread out
describe the structure of the cytoskeleton
-network of proteins structures within the cytoplasm
-rod like microfilaments
-tubulin
-cytoskeleton motor proteins (also enzymes)= binding site=hydrolysis of ATP
what is the function of the cytoskeleton?
-support + mechanical strength
-microtubules=shape + support to cell
-form a track that motor proteins can walk along
-form spindle before cell divides=chromosomes attach
describe the structure of the cellulose cell wall
made from bundles of cellulose fibres
what is the function of the cellulose cell wall?
-strength + support
-maintain cells shape
-permeable + allow solutions through
-prevent cells from bursting
describe the steps of making and secreting a protein
1)gene coding for a specific protein is TRANSCRIBED onto the mRNA
2)mRNA clones + pass out through the pores of the nuclear envelopes
3) ribosomes=instructions are translated=protein is assembled
4)protein mol. pass onto the cisternae of RER
5)vesicles containing the protein are pinched off from the RER
6)vesicles move towards the golgi
7)vesicles fuse with the golgi= mol. modified for release
8)vesicles pinched of the golgi and move towards the membrane
9)vesicles and plasma membrane fuse= proteins released
what are some similarities between prokaryotic and eukaryotic cells?
-plasma membrane
- cytoplasm
-ribosomes
-DNA + RNA
how are prokaryotes different from eukaryotes?
-smaller
-less developed cytoskeleton
-no nucleus
-no membrane bound organelles
-wall made out of peptidoglycan
-naked DNA
what characteristics do some prokaryotic cells have?
-protective waxy cuticle
-small loops of DNA
-flagella
-pili–>allow bacteria to stick to host cell
how to prokaryotic cells divide?
binary fission
