cell membranes

Question 1

where does the synthesis of lipids take place in the cell?

Answer 1

in the cytosol and the endomembrane system

Question 2

what are the phospholipid building blocks?

Answer 2

• 2 fatty acids with acyl tails
• 1 glycerol molecule
• 1 phosphate
• a polar head group

Question 3

how do cells get the fatty acid building blocks?

Answer 3

they’re made via enzymes or taken into cells from food

Question 4

where does the process of phospholipid synthesis occur?

Answer 4

at the cytosolic leaflet of the smooth endoplasmic reticulum

Question 5

how does the transfer of lipids to other membranes work?

Answer 5

lipids in the ER can diffuse laterally to nuclear envelope
they can be transported by vesicles to the Golgi, lysosomes, vacuoles or plasma membrane
by lipid exchange proteins extract lipids from one membrane for insertion in another

Question 6

where does the synthesis of transmembrane proteins occur?

Answer 6

• most are made in the endoplasmic reticulum membrane as they have a signal sequence that directs them to it. from there they are transferred via vesicles to other membranes of the cell
• the exceptions to these are proteins destined for semiautonomous organelles (mitochondria and nucleus)

Question 7

why are cellular membranes important?

Answer 7

• they are selectively permeable and control the entry and exit of substances into the cell
• they protect the cell from its surroundings
• it creates a perfectly balanced environment for cell function
• cell signalling receives and delivers messages to and from cells
• tissue structure can be made from the cell membrane from adhesion of one cell to another

Question 8

what makes up membrane structure?

Answer 8

its a phosphilipid bilayer with a hydrophobic tail and a hydrophilic head
cholesterol regulates the fluidity of the membrane, it also makes it stronger and less fluid and permeable to other water soluble substances

Question 9

what are the two types of integral/ intrinsic transmembrane protiens?

Answer 9

transmembrane proteins-regions are physically embedded in the hydrophobic part of the membrane
lipid-anchored proteins-an amino acid of the protein is covalently attached to a lipid

Question 10

where are peripheral/ extrinsic proteins found?

Answer 10

theyre found on the surface of the membrane

peripheral proteins can attach and remove themselves from the membrane