B2.2: Organelles and Compartmentalization Flashcards
What is an organelle
A discrete structure within a cell that’s adapted to perform a specific function
Is the plasma membrane itself considered an organelle
Yes
3 examples of solid organelles (no membrane)
- Ribosomes
- Centrioles
- Nucleolus
What is meant by single membrane
Single Phospholipid Bilayer
What is meant by double membrane
Double phospholipid bilyaer
4 examples of single membrane bound organelles
- Vesicles and Vacuoles
- rER & sER
- Golgi apparatus
- Lysosomes
3 examples of double membrane bound organelles
- Nucleus
- Chloroplasts
- Mitochondria
Why is the cell wall not considered to be an organelle
- Outside of the cell membrane hence, meaning it’s extracellular - it’s not in the cell so the cell wall isn’t an organelle
Why is the cytoplasm not considered to be an organelle
- Not specialised to perform a specific function
Why is the cytoskeleton not considered to be an organelle
- It’s not a discrete structure as it’s composed of many different types of filaments and tubules
Why do some membrane-bound organelles need double membranes
Prevents cells with interacting with one another
What is compartmentalisation
separation from organelles via their membranes to provide them an area for itnernal chemistry
- kinda like rooms in a house
What are the benefits of DNA in the nucleus being compartmentalised from the cytoplasm
- Allows for specialised and compartmentalisation control of major DNA functions like Transcription and Translation, Replication and repair of damaged DNA
Compare the location and timing of initiation of transcription and translation between prokaryotic and eukaryotic cells
Eukaryotic cells:
- Transcription first occurs in the nucleus and translation occurs in the cytoplasm
Prokaryotic cells:
- Both transcription and translation occur in the cytoplasm
Outline why post-transcriptional modification of RNA isn’t possible in prokaryotic cells
- Eukaryotic cells:
Post transcriptional modification is a common occurrence. Compartmentalising the nucleus and cytoplasm allows the post-transcriptional changes to occur before translation - Prokaryotic cells
Transcription and Translation occur in the cytoplasm at the same time and a separation is not possible due to the lack of a nucleus
Why are the cytoplasm and nucleus separated in eukaryotic cells
- To prevent proteins synthesis before post-transcriptional modification of mRNA
Define compartmentalisation within cells
- The membrane around an organelle creates a compartment with controlled conditions inside
List advantages of compartmentalisation within cells
- Enzymes & Metabolites can be concentrated in a small space which increases chances for collisions between active site and substrate
- Substances that can damage cells can be isolated within a membrane which can protect remaining structure from degradation
- Conditions can be maintained at optimal value for reactions
- Large areas of membranes can become dense with proteins for a specific process
What’s a possible disadvantage of compartmentalisation in cells?
It can delay a cell’s ability to respond to the environment
Outline the benefit of compartmentalisation of lysosomes and phagocytic vacuoles in cells
Lysosomes:
- Hydrolyses (breaks down) and recycle waste materials within the cell
Phagocytic vacuoles in cells:
- Break down pathogens into parts to develop an immune response
What type of process occurs in phagocytosis
endocytosis
How does phagocytosis work in lysosomes
- The hydrolytic enzymes from the lysosome digest the object
- The engulfed object is enclosed within a membrane bound vacuole called phagosome
- The phagosome fuses with the lysosome to become a phagolysome
Why does the outside of the Lysosome have a lower pH than the inside
- Prevents hydrolytic enzyme leakage therefore causing the enzymes to denature
- The hydrolytic enzymes function optimally at a lower, acidic pH
Describe how outer membranes of mitochondria are adapted to their function:
Separates contents of mitochondria from the rest of the cell