Unit 1.2b(ii) Flashcards
What are the two components of the cell membrane?
Integral (permanently attached) proteins and peripheral (temporarily attached) proteins
What are peripheral proteins attached to?
Lipids or exposed integral proteins
What are the two protein components of the cell membrane involved in?
They’re involved in the the synthesis and processing of proteins and lipids
Which ER are lipids synthesised in?
Smooth ER
Where are proteins and lipids synthesised?
They’re synthesised in the ER
Once synthesised what do lipids do?
They insert themselves into the SER membrane
What are some examples of lipids?
Oil, phospholipids, steroid hormones
Where does all protein synthesis begin?
It all begins in cytosolic ribosomes found in the cytosol
Do cytosolic proteins complete translation the the ribosome?
Yes they do
After synthesis what happens to the cytosolic protein?
They are taken to the appropriate organelle where it moves through the membrane and into the organelles interior.
What are two examples of cytosolic proteins?
- enzymes of glycolysis
- enzymes that attach amino acids to tRNA molecules for protein synthesis
Are cytosolic ribosomes attached to anything?
No, they float freely in the cytosol
How do proteins locate cytosolic ribosome?
They have signal sequences that direct them to the ribosome
What is a signal sequence?
It’s a short stretch of amino acids at one end of the polypeptide
What is protein synthesis?
It’s the process of both transcription and translation.
when can the synthesis of a transmembrane protein be completed?
Once the cytosolic ribosome docks with the ER to become apart of the RER
How does the transmembrane protein halt translation so it can travel to the ER?
The signal sequence halt’s translation and directs the ribosome to the ER dock.
After the transmembrane protein docks onto the ER what happens to it?
The protein is inserted into the ERs Membrane
Does the ribosome stay on the ER?
No, once translation has been completed it is released back into the cytosol
Once in the ER what happens to the transmembrane proteins?
Vesicles transport them by budding off of the ER and fusing with the Golgi apparatus
