studying cells Flashcards
what is the function of the ribsosomes
site of protein synthesis
what is the function of the Nucleus
contains genetic material / DNA
controls cell activity
what is the function of the mitochondria
site of aerobic respiration
ATP production
what is the function of the Smooth Endoplasmic Reticulum
site of lipid synthesis
what is the function of the Rough Endoplasmic reticulum
encrusted in Ribosomes
site of protein synthesis
transports and stores protein within the cell
what is the function of Golgi Apparatus
modifies/packages/sorts proteins
produces vesicles
What is the function of lysosomes
contains digestive enzymes
digests worn out organelles/autolysis
what is the function of Cell surface membrane
made of a Phospholipid Bi-layer
controls what enters the cell/ is selectively permeable
can be folded to increase SA
what is the function of Chloroplasts
contain thylakoids, stacked into Granum
site of photosynthesis
what is the function of Plasmid
circular DNA
contains antibiotic resistance genes
what is the function of Cell Wall
provides rigid shape / structure
stops osmotic lysis
what is the function of Flagellum
allows movement/propulsion
eukaryotic cells produce and release proteins
outline the role of organelles in the production, transport and release of proteins from eukaryotic cells
- DNA in nucleus is code (for protein)
- ribosomes/rough endoplasmic reticulum produce (protein)
- mitochondria produce ATP (for protein synthesis)
4 golgi apparatus package/modify OR carbohydrate added/glycoprotein produced by Golgi apparatus
5 vesicles transport OR Rough endoplasmic reticulum transports - (vesicles) fuse with cell(-surface) membrane
describe the differences between Eukaryotic and Prokaryotic cells
Comparisons
1. nucleotide structure is identical;
2. nucleotides joined by phosphodiester bond
OR Deoxyribose joined to phosphate (in sugar, phosphate backbone)
DNA in mitochondria / chloroplasts same / similar (structure) to DNA in prokaryotes
Contrasts
4. eukaryotic DNA is longer
5. eukaryotic DNA contain introns, prokaryotic DNA does not
6. eukaryotic DNA is linear, prokaryotic DNA is circular
7. eukaryotic DNA is associated with / bound to protein / histones, prokaryotic DNA is not
state three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell
plant v prokaryote
1. (associated with) histones/proteins v no histones/proteins
2. linear v circular
3. no plasmids v plasmids
4. introns v no introns
5. long(er) v short(er)
the structure of a cholera bacterium is different from the structure of an epithelial cell from the small intestine
describe how the structure of a cholera bacterium is different
- cholera bacterium is prokaryote
- does not have a nucleus/nuclear envelope/ has DNA free in cytoplasm/has loop of DNA
3 and 4 any two from: [no membrane-bound organelles/no mitochondria / no golgi/no endoplasmic reticulum]
5 small ribosomes only
6 and 7 any two from [capsule/flagellum/plasmid / cell wall]
give one advantage of using a TEM rather than a SEM
- higher resolution
- higher (maximum) magnification / higher detail (of image)
OR - allows internal details / structures within (cells) to be seen / cross section to be taken
give one advantage of using a SEM rather than a TEM
thin sections do not need to be prepared / shows surface of specimen / can have 3-D images
scientists use optical microscopes and transmission electron microscopes to investigate cell structure
explain the advantages and limitations of using a TEM to investigate cell structure
Advantages:
1 small objects can be seen
2 TEM has high resolution
3 electron wavelength is shorter
Limitations:
4 cannot look at living cells
5 must be in a vacuum
6 must cut section / thin specimen
7 preparation may create artefact
scientists isolated mitochondria from liver cells. They broke the cells open in an ice-cold, buffered isotonic solution
explain why the solution was
a) isotonic
b) ice cold
c) buffered
a) prevents osmosis / no (net) movement of water so organelle/named organelle does not burst/shrivel
b) reduce/prevent enzyme activity so organelles are not digested / damaged
c) maintain a constant pH so proteins do not denature
describe and explain how cell fractionation and centrifugation can be used to isolate mitochondria from a suspension of animal cells
- cell homogenisation to break open cells and release organelles
- filter to remove (large) debris/whole cells
- use isotonic solution to prevent osmotic damage to mitochondria / organelles
- keep cold to prevent/reduce damage to organelles by enzyme
- use buffer to maintain pH and prevent protein/enzyme denaturation
- use differential Centrifuge (at high speed/1000 g) to separate nuclei / cell fragments / heavy organelles
- re-spin (supernatant / after nuclei/pellet removed) at higher speed to get mitochondria in pellet/at bottom
- observe pellet with a microscope to identify mitochondria
describe the structure of a phospholipid molecule and explain how phospholipids are arranged in a plasma membrane (3 marks)
- glycerol joined to two fatty acid tails Phosphate group joined to glycerol on opposite side (joined by condensation reaction with ester bond)
- phospholipid has hydrophilic head (phosphate and glycerol) and hydrophobic tails (fatty acid chains)
- arrange to form a phospholipid bilayer; (Hydrophilic head facing out. hydrophobic fatty acid chains facing in)
What is the cell wall in algae and plants made from?
Cellulose
What is the cell wall in bacteria made from?
Murein / Peptidoglycan
What is the cell wall in Fungi made from?
Chitin
What is the function of a capsule? (2)
- Protects cell from immune systems
- Aids bacteria sticking together
Name 2 structures found within a eukaryotic cell that cannot be identified using an optical microscope (2)
- Mitochondrion
- Ribosome
- Endoplasmic reticulum
- Lysosome
- Cell - surface membrane
Describe how the student could have used an eyepiece graticule to determine the mean diameter of stomata (3)
- Measure each stomata using an eye piece graticule
- Calibrate the eyepiece graticule against a stage micrometre
- Take at least 5 measurements and calculate a mean
Explain the advantages and limitations of using a
TEM to investigate cell structure. (5)
ADVANTAGES
1. Small obiects can be seen
2. TEM has high resolution
3. Electron wavelength is shorter
LIMITATIONS
4. Cannot look at living cells
5. Must be in a vacuum
6. Thin specimen required
7. Preparation may create artefacts
Describe how you could make a temporary mount of a piece of a plant tissue to observe the position of starch grains in the cells when using an optical (light) microscope. (4)
- Add a drop of water to the microscope slide
- Get a thin section of plant tissue and float on the drop of water
- Stain with KI solution
- Lower the cover slip using a mounted needle to avoid air bubbles
