Cells Flashcards
magnification equation
magnification = image size/ actual size
name 4 types of microscopes
optical, laser scanning confocal, scanning electron microscope, transmission electron microscope
how can specimens be made more visible under a TEM?
stain the specimen with metal salts
definition of an artefact
objects under a microscope that look like real structures but are the result of preserving and staining
which microscope(s) create a 3D image
laser confocal microscopes & SEM
which microscope(s) create a 2D image
optical & TEM
optical magnification
x1500-2000
laser scanning confocal magnification
x2000
SEM magnification
x2,000,000
TEM magnification
x2,000,000
optical resolution
50-200nm
laser scanning confocal res.
high (varies)
SEM res.
3-10nm
TEM res.
0.05-10nm
where an how are mitochondria produced
they are self-replicating
name 4 organelles that aren’t membrane-bound
centriole, ribosomes, nucleolus (technically not a organelle), cytoskeleton, cellulose cell wall
what is the a-level replacement word for cell membrane
cell SURFACE membrane
what are SER & RER made of
cisternae
describe the structure of ER
fluid-filled cavities connected to the nuclear membrane (with/without ribosomes attached)
how many subunits are ribosomes made of
2
n
b
describe the nucleolus structure
concentrated genetic material within the nucleas without a membrane
briefly outline how ribosomes are made
2 subunits exit the nuclear envelope through pores and combine in the cytoplasm to form ribosome
what is the purpose of the Golgi apparatus
recieevs proteins from RER/ribosomes (1), modifies & packages proteins into vesicles (2) e.g lysosomes., (3) or for replenish plasma membrane
what is the purpose of the rough endoplasmic reticulum?
to transport proteins (to golgi apparatus) made from attached ribosomes. proteins pass through membrane into cisternae
what is the purpose of smooth endoplasmic reticulum
catalyze lipid metabolic reactions e.g synthesise lipids
name 3 examples of lipid metabolic reactions
e.g absorption, transport, synthesis
describe the formation of chromosomes in the nucleus
histone protein binds with DNA to form a complex called chromatin, just before cell division the chromatin coils & condenses to form chromosomes
where can chloroplasts be mainly found in the cross-section of a leaf
in the palisade mesophyll layer or the spongy mesophyll layer
what other ‘things’ do chloroplasts contain
ribosomes, DNA strands, starch grains
what are ribosomes made out of
rRNA & protein
why are cells stained before being viewed under a light microscope?
most cells have a low contrast when light is shone through them, staining increases contrast, hence increases visibility
differential staining definition
using 2 or more stains to color different structures (organelles or cells) to increase visibility
what is the purpose of stains
to increase contrast between organelles to increase visibility
name 2 positively charged stains
methylene blue, crystal violet
name 2 negatively charged stains
congo red, nigrosin
what is negative stain technique
staining the background rather than the structures, which then appear white
how does negative stain technique work?
negative stains are repelled by the cell’s cytosol, coloring the background & not entering the cell
why is the incompressible property of water important in nature (2)
provides turgidity to plants
provides a hydrostatic skeleton for small animals e.g earthworm
why is high surface tension important for organisms (3)
slows down rate of transpiration (& water loss)
some insects can skim across its surface
provides capillary action (helpful in roots)
what is the bacteria equivalent of organelles which do metabolic reactions e.g mitochondria
the mesosome with enzymes attached
what size are ribosomes in bacteria cells
70S
what is bacteria cell wall made out of (2 words)
murein & peptidoglycan
what is fungi cell wall made out of
chitin
describe flagella structure
whip like projection
cilia function
moves back and forth rhythmically to move substances/ to be moved
What is the nucleas-without-a-membrane equivalent in a bacteria?
nucleoid (concentrated area of DNA strands
pili’s structure
hair like projections
pili’s function
can adhere to other cells (hosts/bacteria) and form a passage for plasmid DNA to exchange between cells
What happens at the ribosomes during protein synthesis? Step 1
rRNA attaches to ribosome, where 3 bases/codon codes for 1 amino acid
What happens at the ribosomes during protein synthesis? Step 2
the ribosome moved to the next 3 bases, attaching amino acids, until the end of the rRNA, when the polypeptide detaches
Where are DNA loops located in prokaryotes
Nucleoid region
What is the cell wall in a prokarotic cell made of
Peptidoglycon/ murein
Mesosome definition
Folded region of plasma membrane (1) containing all the membrane bound proteins (2) for cellular metabolic reactions
Why do electron microscopes have a better magnification than light microscopes
Electrons have a smaller wavelength than light (1) hence has a higher resolution (2) allowing for a higher magnification
what is the object under a microscope called
object/specimen
Give an overview of cell theory (3points)
Both plant and animal tissue is composed of cells (1);
cells are the basic unit of all life (1);
cells only develop from existing cells (1)
what is a photo taken through a microscope called
photomicrograph
magnification definition
how much bigger the image is compared to the original object viewed with the naked eye
resolution definition
the ability to distinguish between two separate entities.
cell membrane definition (3 points)
a partially permeable barrier between cell contents & environment (1)
sites of chemical reactions(2)
sites of cell communication (3)
cytoplasm definiton
internal fluid of cells, composed of cytosol (water, salts & organic molecules) organelles & cytoskeleton
what is cytosol
part of cytoplams; consitst of water, salts & organic molecules
what organelles can’t be seen by a light microscope?
mitochondria’s internal structures (e.g cristae & matrix)
why does optical light microscope & LSC have a limited resolution
wavelength of light too long
what can you view with light microscope?
cell walls, vacuoles, cytoplasm, chloroplasts, nucleus and cell membrane
what can’t you view through a light microscope; only an electron microscope?
ribosomes, endoplasmic reticulum, lysosomes, centrioles, Golgi bodies, mitochondria’s internal structures (e.g cristae & matrix), nucleolus etc.
give an example of differential staining, what is it used for
gram stain technique; to distinguish between 2 types of bacteria
what does iodine do in … differential staining
fixes the dye onto the bacteria sample
which 2 dyes are used in …. differential staining and what do they work on?
crystal violet dye - gram postitive bacteria
safranin dye - gram negative bacteria
what is safranin dye in … differntial staining?
a counterstain
what type of bacteria does penicillin work on & how?
works on gram positive bacteria by inhibiting cell wall formation
True or False, endoplamis reticulums have to be connected to the nuclear envelope
false
which is smaller: ribosomes or lysosomes?
ribosomes
what is the average diameter of prokaryotes
0.5-5 micrometres
what is the average diameter of eukaryotes
20-40 micrometres
what is the technical ter, for vesicle merging with cell membrane during exocytosis
vesicle fuses with cell membrane
cell theory (3)
All living things are composed of cells.
Cells are the basic units of structure and function for living things.
All cells come from pre-existing cells. Also, organisms grow by “adding on more cells” NOT by increasing the size of their cells
nucleolus function
producing and assembling the cell’s ribosomes
what is the role of nuclear pores
allow communication between nucleus and cytoplasm
& allows, molecules / named substances, to,
enter / leave (the nucleus)
True or False golgi and ER can’t be seen under a light microscope
true
what is the average diameter of eukaryotes
20-40 micrometres
what is the average diameter of prokarotes
0.5-5 micrometres
ribosmes in eukarotes diameter
22nm
ribosomes in prokaryotes diameter
18nm
name all eukarotyotes
animal, plant, fungi, protists
are centrioles present in plants?
no, only in animal cells
give 3 reasons why cells have to be compartmentalised
Incompatible reactions / catabolic and anabolic reactions require different conditions / damage
due to hydrolytic enzymes
why are artefacts more likely to appear in electron microscopy and less in light microscropy
more sample preparation (in electron microscopy) (1) / (leads to) more damage to specimen
why can’t confocal microscopy be used for deep tissue imaging
idea of light penetration (of sample) is limited (1)
explain the difference between contrast and resolution
Contrast is difference in colour/shade between two objects (1) Resolution is the smallest distance
between two objects that can still be seen as separate
what does high absorption/low transmission on a colorimeter show?
high concentration of pigment in solution
