Cell membranes

Question 1

Chloride ions (Cl-) need to pass through the cell surf membrane to get inside the cell. How might they move across membrane

Answer 1

Using carrier or channel proteins in the membrane

Question 2

The protein content of a typical cell membrane is around 50%.
In energy-releasing organelles, such as mitochondria, the amount rises to around 75%. Suggest a reason for this difference.

Answer 2

energy-releasing organelles require lots of substances (e.g. nutrients, enzymes, ATP) to travel across their membranes. Some of these substances will require help from proteins to get across the membrane, so these membranes will have a higher protein content.

Question 3

A person removes some raspberries from the freezer that have frozen solid and leaves them on a plate to defrost. When he returns, there’s a red puddle on the plate around the fruit. Use your knowledge of cell membranes to explain what has happened.

Answer 3

Freezing the raspberries will have caused ice crystals to form and pierce the cell-surface membranes, making the membranes highly permeable when they thawed. This will have caused the red pigment to leak out of the raspberry cells as they defrosted.

Question 4

What are the functions of cell membrane

Answer 4

Surround cells.
Boundaries cell and environment. Control what enter and leave to enable signalling (Pp)
divide cell component eg enzymes for respiration in the mitochondria makes more efficient.