Topic 2: Cell Structure Flashcards
How do you calculate magnification?
Image size / Actual size
What is cell fractionation?
The process where cells are brocken up and the different organelles they contain are separated out.
Why is the tissue put in a cold solution before cell fractionation?
To reduce enzyme activity that might break down the organelles
Why does the solution have the same water potential as the tissue used in cell fractionation (isotonic)?
To prevent organelles from bursting or shrinking due to the osmotic gain or loss of water.
Why is the solution used before cell fractionation buffered?
So that the pH doesn’t fluctuate.
- Change in pH could alter the structure of the organelles, affecting the functioning of enzymes.
What are the stages of cell fractionation?
- Homogenation
- Filtration
- Ultracentrifugation
What happens in Homogenation?
Cells are broken up by a homogeniser, releasing the organelles from the cell. The homogenate is then filtered
Why is the homogenate filtered?
To remove any complete cells and large pieces of debris
What is ultracentrifugation?
The process by which the fragments in the filtered homogenate are separated in a centrifuge.
Describe the process of ultracentrifugation.
-Tube of filtrate is placed in the centrifuge and spun at a slow speed.
-Heaviest organelles (nuclei) forced to the bottom forming a pellet
-Supernatant is removed and transferred to another tube
- it’s then spun in the centrifuge at a higher speed
- next heaviest organelles (mitochondria) forced to the bottom of the tube
-process continued until desired product is produced.
What is the rough endoplasmic reticulum?
System of membranes that’s continuous with the nucleus, with ribosomes on the outer surface.
Where proteins are processed and packaged into vesicles.
What is a Lysosome?
A membrane bound organelle that releases hydrolytic enzymes (lysozymes)
What is the function of the mitochondria?
Site or aerobic respiration and production of ATP
Describe the structure of the nucleus and its role.
Contains DNA which controls the activities of the cell by containing the base sequence which codes for proteins.
What’s the nucleolus?
The region within the nucleus where ribosomes are made
Describe the structure and role of the nuclear envelope.
-Double membrane: surrounds the nucleus
-Pores: allowing small molecules to pass through
What does the SER do? and how is it different to the RER?
synthesises lipids and carbohydrates.
has no ribosomes on its surface.
Describe the structure of the golgi apparatus.
Fluid-filled
Membrane-bound
Flattened sacs
Surrounded by vesicles
What’s the role of the golgi apparatus?
-processes lipids and proteins and packages them into vesicles
-site of lysosome synthesis
Where can ribosomes be found in the cell?
Float freely in the cytoplasm or stuck on the RER
What’s the role of ribosomes and what is it made of?
Responsible for the translation of RNA into proteins.
RNA and Proteins
Describe the structure of the mitochondria.
Double membrane - inner membrane is folded to form cristae (provides a large S.A for respiration) .
Inside is the matrix which contains enzymes involved in respiration.
Describe the structure of chloroplasts and its role.
Flattened sac surrounded by a double membrane.
Site of photosynthesis.
Describe the function of the cell wall.
Provides rigidity to the cell as it prevents the cell from bursting when water enters via osmosis. Makes the cell become turgid
