exam 2 module 5 cell membrane

Question 1

A membrane separates each cell from its surroundings.

Answer 1

All cells have a cell membrane.
a) homeostasis-regulating substances help the cell maintain homeostasis

Question 2

The cell membrane is composed of phospholipids.

Answer 2

a) hydrophilic head- the head
b) hydrophobic tails: bonded to two fatty acid tails,
(pic online)

Question 3

Phospholipid bilayer is selectively permeable

Answer 3

a) Identify molecules that can and cannot pass across the cell membrane.
- can freely pass into and out of the cell(Lipids and small, nonpolar molecules, such as O2 (oxygen) and CO2 (carbon dioxide)
- cannot pass through the hydrophobic region( Ions and polar molecules, such as glucose)

Question 4

Cell membrane is a fluid mosaic.(many of the molecules in the membrane the pieces of the mosaic drift throughout the bilayer)

Answer 4

a) steroids
i) cholesterol (animal cell)- In animal cells, cholesterol is the steroid that maintains the membrane’s fluidity.

Question 5

Cell membrane is a fluid mosaic. part 2

Answer 5

B) membrane proteins

i) transport proteins-move substances into and out of cells

ii) enzymes-facilitate chemical reactions

iii) recognition proteins-cell surfaces allow the body to recognize its own cells. Carbohydrates attached to cell-surface proteins serve as “name tags” that help the body’s immune system recognize its cells.

iv) adhesion proteins-Allow cells to stick together.

v) receptor proteins-Bind to molecules outside the cell and trigger chemical reactions inside the cell.