Cell topic 1 questions Flashcards
Which are the smallest and most numerous organelles?
Ribosomes
Which are the most extentions of the inner membrane in mitochondria?
Cristae
What organelle contain hydrolytic enzymes?
Lysosomes
What is the cell wall made of in a prokaryote?
Murein
What is the resolving power (resolution) of a microscope?
The minimum distance apart 2 objects can be seen as separate objects.
What does a centrifuge do?
Spins cell fragments at very high speed.
What is a homogenate?
Fluid containing intact organelles released from a cell
In microschopy, the actual length of an object is calculated as?
Image size/Magnification
What microscope has the highest resolving power?
Transmission Electron Microscope (TEM)
What stage takes up the most time in the cell cycle?
Interphase / S-phase
By what process do prokaryotic cells divide
Binary fission
Phosopholipids form a bilayer in cell membrane structure because they contain…
Hydrophillic heads and hydrophobic tails.
Why can’t most molecules free difuse across a cell membrane?
Not soluble in lipids.
Why is facilitated diffusion a passive process?
It does not require ATP from respiration
What are the four factors that affect rate of diffusion?
- Concentration gradient
- Temperature
- Surface area
- Thickness of exchange surface
When can facilitated diffusion occur?
Can only occur at protein channels and carrier proteins.
What is the function of the SER (Smooth endoplasmic Reticulum?
Synthesises, stores and transports lipids and carbohydrates.
Why do specimens have to be kept in a vacuum to be viewed with an electron microscope?
Because electrons are absorbed by molecules in the air and will not reach the specimen.
Describe the steps you might take to isolate mitochondria from a cell culture in the laboratory.
- Lyse the cells - The cells in the sample are broken open using a blender - this step is known as homogenisation.
The cells must be kept under very specific condtion
Ice cold: reduces the activity of the enzymes. Isotonic solution: there is no water potential for osmosis to occur, which could cause the organelles to shrink or burst. Buffered solution: this keeps the pH at a constant level to prevent damage to protein structure. - Filtration - The homogenised sample is filtered through a gauze. Filtration separates the larger components from the smaller organelles.
- Ultracentrifugation - The filtered samples are spun at a low speed in a centrifuge. It is important that each tube is
balanced with a tube directly opposite. Heavier
components are forced to the bottom of the tube. Lighter components rise to the top. - Repeat - The supernatant from the first round of centrifugation is centrifuged again. The pellet this time will be the nuclei from the cells (this is the first pellet). The process is repeated and the mitochondria will be isolated in the third pellet.
Having isolated the mitochondria, why would TEM be favourable to SEM to image the organelle and identify the double membrane structure?
Higher resolution - Transmission electron microscopy can achieve a higher resolution than scanning electrons microscopy which would be needed to identify the two separate membranes.
Can see internal structures - Electrons pass through the sample in TEM rather than being scattered off the sample in SEM. This means that TEM can visualise structures within the cell.
Greater magnification - Mitochondra are between 0.5 - 10 micrometers in size and so it requires very high magnification to visualise their internal consituents.
What are the steps involved in cell fractionation?
- The tissue sample is homogenised using a blender to break the cells.
- The tissue sample is filtered into tubes through a gauze to separate larger components from the small organelles.
- The organelles are filtered into tubes to be fractionated using ultracentrifugation.
- The samples are spun at a low speed in a centrifuge to separate the sample into fractions.
- The supernatant is poured off and centrifuged at a higher speed to separate the next heaviest organelles. This is repeated at increasingly higher speeds to separate each fraction.
What are the two types of electron microscopes?
There are two main types of electron microscopes:
- Transmission Electron Microscope (TEM)
- Scanning Electron Microscope (SEM)
What’s the differences between the SEM and TEM?
- TEMs use electromagnets to focus the electron beam. Whereas in SEMs, a beam of electrons moves back and forth across a cell’s surface, creating details of cell surface characteristics.
- TEMs are high resolution microscopes whereas in SEMsResolution is lower.
What is the approximate maximum magnification of a optical light microscope?
1,500x
What is the approximate maximum magnification of a Electron microscope?
Electron microscopes have a maximum resolution of x1,500,000.
What is the approximate maximum resolution of a optical light microscope?
0.2 micrometers
What is the approximate maximum resolution of a Electron microscope?
Electron microscopes have a maximum resolution of
0.0002 micrometres. This is around 1000 times more than light microscopes.
What is a Transmittion electron microscope (TEM)?
A microscope which the electron beam penetrates the cell and provides details of a cell’s internal structures.
What is the Scanning electron microscope (SEM)?
A microscope which a beam of electrons moves back and fourth across a cell’s surface, creating details of cell surface characteristics.
What is the maximum resolution and magnification of an optical microscope?
0.2 micrometers and x1,500
Which cell type can form multicellular organisms?
Eukaryotes
Which cell type is between 0.1 and 5.0 micrometres in diameter?
Prokaryotes.
Fungal cells are similar to plant cells, but which organelle do fungal cells lack?
Chloroplasts
What is the plant cell wall made of?
Cellulose
Which of the following cellular components does not have a double membrane?
Lysosomes
What is the name of the fluid-filled membrane sacs found within the chloroplasts?
Thylakoids
Where are ribosomes found bound to a membrane?
Rough endoplasmic reticulum (RER)
Which prokaryotic feature allows the exchange of genetic information?
Pili
“All viruses contain a nucleus.” True or false?
False
The ability to distinguish two very small structures as separate is known as what?
Resolution
During repeated ultracentrifugation, what are the first and last fractions to be separated?
Nucleus and Ribosomes.
Name three structures present in cells of plants that are NOT present in animal cells.
- Cell wall
- Vacuole
- Chloroplasts
- Starch grains
Which structure or structures allow bacteria to move about?
Flagella only.
Radioactive amino acids are fed to a cell in culture for a short amount of time. This is called a pulse. You follow the appearance of radioactive proteins in the cell compartments.
In which organelles and in what order does radioactivity appear?
Endoplasmic reticulum vesicles golgi body vesicles extracelluar region
Macrophages ingest and digest many pathogens. Which organelle plays a major role in the activity of macrophages?
Lysosomes
Why is it challenging to study the biochemistry of bacterial fossils and determine if the fossils are members of the domain archaea, rather than bacteria?
(A-A*)
Bacteria have rigid structures, but their fossil impression is scarce.
How does the structure of a plasmodesma differ from that of a gap junction?
(A-A*)
Gap junctions are found to provide attachment in animal cells and plasmodesma are essential for attachment o plant cells.
Desmosomes are regions where cells adhere to each other, providing mechanical support. In which human tissues would you find desmosomes?
(A-A*)
Muscle cells and skin cells
Inhibitors of microtubule assembly, like vinblastine, are used for cancer chemotherapy. How does an inhibitor of microtubule assembly affect cancerous cells?
(A-A*)
The inhibitors bind the microtuble to the nuclear membrane, stopping cell divison.
