studying cells Flashcards
define eukaryotic
- true nucleus; dna enclosed in a nuclear membrane
- membrane bound organelles
eg: plants, algae, animal, protozoan and fungi
what structures are visible in an animal cell under a light microscope
nucleus
cell membrane
how are epithelial cells adapted for their function/
- cell membrane folded into structures called microvili
-microvili increase SA for absorption
what is the function of the nucleus
contains genetic material
controlls cell activity
describe the structure of the nucleus
- largest organelle
- douvle membrane/ nuclear envelope
- contains nucleolus which is where rRNA is made
- chromatin in nucleus coils around proteins called histones
mitochondria
- site of aerobic respiration
- ATP production
describe the structure of the mitochondria
outer membrane
inner membrane that folds to form cristae
cristae increase SA for atp synthase attachmemt
matrix - contains proteins, lipids, DNA and ribosomes
Rough Endoplasmic Reticulum (RER)
- encrusted in 80s ribosomes
- site of protein synthesis
- transports and stores protein within a cell
- membrane folded into flattened sacks called cisternae
smooth endoplasmic reticulum (SER)
- recombines glycerol and fatty acids to make triglycerides (site of lipid synthesis)
- pakcages triglycerides into vesicles and transports them to golgi apparatus
ribosomea
site of protein synthesis
- made of rRNA and ribosomal proteins
eukaryotic: 80s, prokaryptic: 70s
what is the function of the golgi apparatus
modifies and packages proteins and triglycerides into vesicles
what is the function of a lysosome?
- contains digestive/ hydrolytic enzymes (lysozymes)
- hydrolyses damaged or worn out organelles
cell surface membrane
- made of a phospholipid bilayer
- controls the passage of substances into and out of a cell
- can fold to increase SA
what is the function of chloroplasts
contain thylakoids
stacks of thylakoid = granum
site of photosynthesis
what is the function of the capsule
protects cells from immune systems
aids bacteria sticking together
what is the function of the plasmid
circular DNA
contains antibiotic resistant genes
what is the function of the cell wall
provides a rigid shape
stops osmotic lysis
what is the function of the flagellum
allows movement
what is the function of the centrioles
- forms a network of spindle fibres that attach to chromosomes
- pull chromosomes apart
contrast a plant cell from an animal cell
carbs in animals glycogen, plants store carbs as starch (grains)
plants have chloroplasts, cellulose cell walls and permanent vacuole
plants have plasmodemata
animals have centrioles(
chloroplast
granum = stack of thylakoid membranes
thylakoid = contains chlorophyll for PS and ATP synthase to produce ATP
STROMA - fluid
starch grains - energy storage molceule
- prokaryotic DNA, 70s ribosomes
what is the function of the chloroplast
absorbs light energy for photosynthesis
products of PS/RP allows plant to grow
cellulose cell wall
- very strong
- mnay weak hydrogen bonds between cellulose fibres
- stops osmotic lysis (bursting)
- wall is permeable unlike membrane
- plasmodemata allows cytoplasms to connect together
what are the cell walls in fungi made out of?
chitin
define prokaryotic cells
- no nucleus
- no membrane bound organelels
- circular DNA, no association with histones, no introns
what is the cell wall of a bacterial cell made out of?
murein
eukaryotic cells produce and release proteins. outline the role of organelles in the production, transport and release od proteins from eukaryotic cells.
- DNA in nucleus is code for protein
- ribosomes/ RER produce protein
- mitochondria produces ATP for protein synthesis
- golgi apparatus modifies proteins and packages them in vesicles to transport
- vesicles transport
- vesicles fuse with the cell surface membrane
compare and contrast the differences between euk and prokaryotic cells
similarities:
- nucleotide structure identical
- phosphodiester bonds
- DNA in mitochodnria and chloroplasts are similar to DNA in prokaryotes
Differences:
- euk DNA is longer
- euk DNA has introns
- euk DNA is linear, prok is circular
- euk associated with histones
state three differences between DNA in the nucleus of a plant cell and DNA in a prokjaryotuc cell
- associated with introns
- linear DNA
- plants no plasmid
- introns
- longer
the structure of a cholera bacterium is different to the structure of an epithelium cell from small intestines. describe how it is different.
- cholera bacteria is a prokaryote
- no nucleus
- no membrane bound organelles
- no mitochondria/golgi/RER
- 70s ribosomes only
- capsule/ plasmid/ flagellum
structure of a virus
- not living cells
- either ss or ds DNA/RNA
- attachment proteins
- enzymes (reverse transcriptase)
name two structures of a euk cell that can NOT be indentified with a light microscope
mitochondria
ribosome
lysosome
cell surface membrane
give one advantage of using a TEM rather than a SEM
higher resolution
higher detail of image
allows internal structures to be seen
give one advantage of a SEM rathet than a TEM
3D images
thin sections dont have t be prepared
define resolution
ability to distinguish between 2 objects that are close together
shorter wavelength = higher resolution
scientists use optical microscopes and TEM to investigate cell sturtcure. explain the advantages and limitations of using a TEM
advantage:
small objects can be seen
TEM has hgiher resolution
electron wavelength is shorter
limitATIONS:
cant look at living cells so cells dead
must be in a vacuum so cells dead
thin specimen so dead
COMPLEX staining method so preparation may cause artefacts
describe the principles of a TEM
- electrons pass through specimen
- desner parts absorb more electrons
- denser parts appear darker
- electrons short wavelength so higher resolution
a student views the impressions of stomata using an optical microscope. she measured the mean diameter of the stomata. descirb ehow the student could have used the eyepiece graticule to determine the mean number of stomata
- measure each stomata using the eyepiece graticule
- calibrate the eyepiece graticule against a stage micrometer
- take atleast 5 measurements and calculate a mean
name 2 structures within a euk cell that can be identified using a TEM
mitochondria
ribosome
lysosome
describe how you would make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical microscope
- add a drop of water to the microscope slide
- thin section of plant tissue and float it on the drop of water
- stain with KI solution
- lower cover slip using a mounted needle to avoid air bubbles
magnification equation
I/AM
Image size - magnification x actual size
- measure in mm, x1000 to get micrometres
scientists isolated mitochondria from liver cells. they broke the cells open in an ice cold, buffered, isotonic solution. explain why,
- isotonic so no osmotic lysis of organelles
- ice cold so no enzyme activity so organelles arent digested
- buffered so maintains a constant pH so proteins dont denature
order of density in centrifugation
- nucleus
- mitochondria/ chloroplast
- ER/golgi
- ribosomes
describe and explain how cell fractionation and cell centifugation can be used to isolate mitochondria from a suspension of animal cells
- cell homogenisation to break open cell walls and release organelles
- filter to remove large cellular debris
- use isotonic solution to prevent damage to mitochondria
- cold to prevent enzyme activity so no organelles are digested
- buffer maintains pH, prevents enzyme denaturation
- use differential centrifugation to separate nuclei
- respin at higher speed for longer time to get mitochondrial pellet
- observe the pellet in microscope to identify mitochondria
describe how you could use cell fractionation to isolate chloroplasts from leaf tissue
- break open cell walls in a homogeniser and filter to remove cellular debris
- place in isotonic, ice cold, buffered solution
- use differential centrifugation
- chloroplasts are second pellet
