The final battle hehe :) Flashcards
why are organelles in eukaryotic cells membrane bound
- it provides a distinct environment and therefore conditions for different cellular reactions
- stops incompatable reactions
- stops damage due to hydrolytic enzymes
what is the function of the nucleus
- contains genetic material
- controls metabolic activity of cell
- where transcription and mRNA synthesised for protein synthesis
has a double membrane
what is the function of the nucleolus
- responsible for producing ribosomes in the nucleus
- produces ribosomal RNA
what is the function of the nuclear envelope
- protects the nucleus from the cytoplasm and contains nuclear pores
- nuclear pores allows only certain molecules to move in and out such as mRNA
what is the function of the RER
- ribosomes bound to the surface and are responsible for the synthesis and transport of proteins
- connected to the membrane of the nucleus it is a network of membrane containing flattened sacs called cisternae
what is the function of the smooth ER
responsible for lipid and carbohydrate synthesis and storage
which kind of cells have higher numbers of RER
secretory cells such as those that secrete hormones or enzymes eg) nerve cells
more so than those that dont release proteins
what is the function of the Golgi apparatus
modifies proteins and packages them into vesicles
eg) lysosomes which stay in cell OR secretory vesicles that leave the cell
what is the function of ribosomes
site of protein synthesis
-made from RNA molecules made in nucleolus
mitochondria and chloroplasts also contain ribosomes and so do prokaryotic cells
what is the function of mitochondria
- site of anaerobic respiration
- release energy in the form ATP
- energy is stored in complex organic molecules
how many mitochondria a cell has is a reflection of how much energy it uses
what is the function of lysosomes
they contain a hydrolytic enzyme which breaks down waste materials like old organelles
- important in the immune system as they break down pathogens ingested by phagocytic cells
- cell death and apoptsosis
why is the membrane surrounding a lysosome important
hydrolytic enzymes could damage cell structures so must be compartmentalised to stop damage
what is the function of chloroplasts
site of photosynethesis
- green pigment chlorophyll absorbs sunlight
- double membrane structures and fluid inside s called stroma
- starch produced
what is the function of the plasma membrane
phospholipid bilayer embedded with proteins
-regulates the movement of substances in and out of cell and protects cell from surroundings
what is the function of centrioles
(two form a centrosome)
its a component of the cytoskeleton in eukaryotic cells apart from flowering plants and fungi
-the centrosome is involved in the assembly and organsisation of spindle fibres
-the are composed of microtubules
what is the cellulose cell walls function
- made of cellulose a complex carbohydrate
- freely permeable so substances to pass in/out
- provide rigid structure (because contents of cell press against the wall) and give plant cell shape
- protects cell from invading pathogens
what is the function of flagella
enable cell mobility
-also a sensory organelle which detects chemical changes in environment
what is the function of cillia
- the rhythmically contract to waft substances and can be mobile or stationary
- important in sensory organs like nose
- cause substances and fluid next to cell to move
what are microfilaments
- part of cytoskeleton
- contractile fibres formed from the protein actin
- these are reposnible for : cell movement, cell contraction during cytokinesis
what are microtubules
globular tubulin proteins polymerise to scaffold the struture which determines the shape of the cell
-act as conveyer belts to move organelles around the cell including vesicles for exocytosis
what is the function of vacuoles
- membrane lined sacs in cytoplasm containing cell sap
- important in maintaining tungor pressure, contents pushed up against cell wall for rigid structures
- vacuoles in animal cells are small and not permanent
the internal network of membranes form flattened sacks in chloroplasts called….
thylakoids
granum are several thylakoids stacked but what joins them
lamellae
describe the interelationship between organelles and the production and secretion of proteins
1) Proteins are sythesised on ribosomes bound to RER
2) pass onto its cisternae and are packaged into vesicles
3) these vesicles move to Golgi apparatus by cytoskeleton like microtubules
4) vesicles fuse with cis face of Golgi apparatus and proteins enter
5) proteins are structurally modified before leaving the Golgi by the trans face
6) vesicles move towards and fuse with the cell-surface membrane and leave by exocytosis
what is the difference between magnification and resolution
magnification is how many times larger the image is than the actual object being viewed
resolution is how easy it is to distinguish between two points that are close together
differences in resolution and magnification can be achieved by a light microscope, transmission electron microscope and a SEMicroscope
for example resolution is increased using beams of electrons with wavelengths much shorter than light meaning objects smaller and closer together can be seen separately without diffraction blurring the image
what is the magnification formula
magnification= image size / object size
what is the purpose of staining
increase the constrast between structures/ organelles
specimens can be treated with multiple stains to show different structures
differential staining- used to distinguish between two types of organisms that would otherwise be hard to identify
can differentiate between different organelles of a single organism within a tissue sample
what is gram-stain technique briefly
used to separate bacteria into two groups : gram positive and gram negative.
crstal violet dye is applied and washed with alcohol on sample gram positive retains this dye
when preparing samples name 4 methods which could be used
dry mount- very thin slice of solid spec. cover slip over slide , thinness allows more light to pass through + more contrast
wet mount- cover slip placed on from an angle to minimise risk of air bubbles
squash slide- wet mount first prepped then lens tissue gently used to press down cover slip
smear slide- edge of slide used to smear sample to create thin even coating (for blood for example)
how is an eyepiece graticule used
(relative sizes of divisions increases with magnification)
how is a stage micrometer used
-very accurate scale in micrometers um
how would you calibrate an objective lens
put stage micrometer in place and eyepiece graticule in the eyepiece
- get scale on micrometer in clear focus
- align micrometer with scale in the eyepiece
what are the advantages and disadvantages of light microscopes
+easy to opperate
+cheaper
+observe living organisms
- lower resolution
- lower magnification
- harder to view internal structures
what are advantages and disadvantages of electron microscopes
+powerful magnification using electrons
+clearer image
+higher resolution
- expensive
- upkeep difficult
- sensitive to magnetic fields
what is fluoresence in terms of microscopy
absorbtion and re-radiation of light
its used as dye in Laser scanning confocal microscopy
why do lasers provide illumination in LSCM
to increase the intensity of light across the specimen
what is the purpose of the pinhole aperture
- reduces blurring/ increased resolution
- eliminates scattered light/ light from outside focal plane
how would you calibrate an eyepiece graticule and how is a calibration factor determined
-start w/ lowest power on objective lens
align scale on stage micrometer w/ scale on eyepiece graticule
take reading from both scales to find calibration factor
describe the importance of the cytoskeleton
- maintains shape and stability and provides support
- changes shape of the cell
- controls movement of vesicles
- movement of chromosomes and mRNA
- movement of flagella
microtubules, microfilaments, intermediate fibres
what is an artifact
visible structural detail caused by the processing of the specimen but isnt a feature of the specimen eg bubbles trapped under slip during preparation
why would you see more detail with an electron microscope than light microscope
electrons have shorter wavelengths than light waves.
higher magnification and better resolution
how does electron microscope work
beam of electrons used to illuminate specimen and produces a magnification up to x500,000!!!
TEM vs SEM
TEM- best resolution, see internal structure
SEM- electrons sent across surface and reflected electrons collected,
resolution not as good but 3D images can be collected
what is LSCM
moves a sigle spot of focussed light across specimen by point illumination which causes fluoresnce from component’s labelled dye
emitted light from pinhole apperture
ONLY light close to focal plane is detected
properties of water and its importance for living organsisms
-cohesive- so is able to be drawn up roots and xylem and also are more cohesive to each other than they are to air so there is a skin of surface tension
-solvent- because its polar solutes can be dissolved in it eg)cytosol in prokaryotes and eukaryotes)
- its a medium that can transport substances because its a solvent
-coolant- maintains constant temp as large amounts of energy are needed to overcome hydrogen bonding.
important as enzymes are only active in narrow temp ranges
-because ice floats it insulates water below for aquatic organisms.
how do hydrogen bonds form in water molecules
unequal share of electrons between hydrogen and oxygen in a covalent bond
positive and negative regions attractand form hydrogen bonds which have weak interactions which break and reform constantly between water molecules
this bonding gives water its properties that support life
which elements are in carbohydrates
C H O
which elements are in lipids
C H O
which elements are in proteins
C H O N S
which elements are in nucleic acids
C H O N P
what is the difference between a pentose and hexose monosaccharide
pentose is a group of monosaccahrides with 5 carbon
hexose is 6
