cell membrane

Question 1

what does the plasma membrane do?

Answer 1

1. separate intracellular environment from extracellular environment
2. organisms require substances from the extracellular space for their cells to reproduce, grow, repair damage and to supply energy for their many functions and remove waste from their cells
3. allows for the exchange of material.
4. allows some materials to pass through while others cannot pass, thus it is partially-permeable.

Question 2

what is the fluid mosaic model?

Answer 2

• describes the plasma membrane as a moving sea of phospholipids with proteins floating in it.
• phospholipids have two hydrophobic lipid tails and a hydrophilic phosphate head. the bilayer forms when phospholipids are in a polar environment like water. all water-loving phosphate heads gather together to form two layers. all hydrophobic tails point towards each other, away from the contact with the water.

Question 3

what is cholesterol?

Answer 3

• type of steroid lipid molecule, present between some of the phospholipid molecules in the plasma membranes of animal cells
• stabilises the membrane and keeps it fluid

Question 4

what are proteins of the mosaic?

Answer 4

1. contains proteins
   - peripheral proteins are not actually a part of the membrane, but are loosely attached to the surface
   - integral proteins are proteins molecules that cross at least one of the phospholipid layer. proteins that cross both layers are called transmembrane proteins. most integral proteins are transmembrane proteins.
   - transport substances across the plasma membrane
   - receptor sites for signal molecules, such as hormones and neurotransmitters
   - involved in cell-to-cell recognition
   - involved in holding cells together

Question 5

what are carbohydrates of the plasma membrane

Answer 5

carbohydrate molecules help with cell-to-cell recognition, they can bind protein molecules to form glycoproteins, or to lipid molecules to form glycolipids.