Organelles & compartmentalisation - organelles in protein synthesis Flashcards
What is the nuclear envelope?
A double membrane that separates the nucleus from the cytoplasm
Present in all eukaryotic cells, it allows for DNA functions to occur separately from the rest of the cell.
What is the function of nuclear pores?
Channels for allowing mRNA and ribosomes to travel out of the nucleus and enzymes/signalling molecules to travel in
Important for the transport of genetic material and proteins.
How does the outer membrane of the nucleus relate to the endoplasmic reticulum?
It is a continuous structure that links to the endoplasmic reticulum
Ribosomes can be attached to the outer membrane, forming rough endoplasmic reticulum.
What happens to the nuclear membrane during cellular division?
It breaks into vesicles during prophase and reforms at telophase
This allows for the separation of chromosomes.
Where are ribosomes found in cells?
In the cytoplasm (freely) or bound to the endoplasmic reticulum (forming rough ER)
Ribosomes are present in all cells but bound ribosomes are only in eukaryotic cells.
What is the role of ribosomes?
Site of protein synthesis
Comprised of a large and a small subunit made of protein and rRNA.
What are the components of ribosomes?
Large subunit, small subunit, protein, ribosomal RNA (rRNA)
rRNA facilitates binding of mRNA and tRNA.
How many binding sites do ribosomes have?
Three tRNA binding sites and one mRNA binding site
mRNA sits in a groove between the two subunits.
What is the difference between free ribosomes and membrane-bound ribosomes?
Free ribosomes synthesize proteins for use within the cell; membrane-bound ribosomes synthesize proteins for secretion or lysosomes
Free ribosomes can move within the cytoplasm.
What do proteins synthesized on free ribosomes typically do?
They are destined for use within the cytosol and large organelles such as mitochondria and chloroplasts
These are proteins that remain within the cell.
What directs free ribosomes to the endoplasmic reticulum?
Signal sequences in the growing polypeptide chain
This sequence indicates the need for the ribosome to move to the ER.
What is the Golgi apparatus?
A structure consisting of flattened sacs of membrane called cisternae
Its role is to modify proteins and lipids before packaging them into vesicles.
What does the cis side of the Golgi apparatus do?
Receives protein or lipid-filled vesicles from the endoplasmic reticulum
Indicates its function in processing incoming materials.
What happens to proteins that go through the Golgi apparatus?
They are usually exported, put into lysosomes, or delivered to membrane-bound organelles
Example: hormones like insulin are exported.
Fill in the blank: Ribosomes consist of a large and a small subunit composed of _______.
protein and ribosomal RNA (rRNA)
rRNA is essential for ribosome function.
True or False: The Golgi apparatus faces the plasma membrane on both sides.
False
One side is the cis side facing the ER, and the other is the trans side facing the plasma membrane.
