1. NOTE SHEET 7 – The Cell Membrane

2. All Cells Have a Cell Membrane
Cells are the basic units of structure and function in living things, which means, they have all the characteristics of life (R.O.A.D.)
The cell membrane allows the cell to adjust to its environment by using energy to control what comes in and what goes out
By doing this the cell maintains homeostasis, or a stable internal environment, which it needs to survive

3. What are the parts of a cell made of?
Proteins (C,H,O,N,S) – building materials, messengers, speed things up
Lipids (C,H,O) – store energy, form membranes, insulation
Carbohydrates (C,H,O) – energy source for cells, building material
Nucleic Acids (C,H,O) – store and carry information
Water (H2O)
97% of an organism’s body weight is the elements C,H,O,N
Organic Molecules

4. Why does the cell need to control what comes in and what goes out?
The cell needs to keep a certain amount of substances in its cytoplasm
The cell has to take in what it needs and let out what it doesn’t need

7. Cell Membrane Structure

8. Cell Membrane Structure

9. What is the structure of the cell membrane?
The cell membrane is a bilayer (double layer) made of 2 layers of lipids with some proteins in between

10. The cell membrane is made of the following 3 parts:
Lipids – make up the flexible inner and outer layer of the cell membrane
ID protein/carbohydrate – identifies the cell so it is recognized by the organism’s body and by other cells
Gateway protein – acts as a door that lets substances in and out

11. Selective Permeability
The cell membrane is selectively permeable, which means it allows some substances to pass through while holding other substances back

12. What are solutions and how do they affect cells?
Cells are filled with solution and surrounded by solution
A solution is a mixture of solvent (water) and a solute (salt, sugar, calcium, etc.)
Cytoplasm is a solution of water and many different solutes (amino acids, oxygen, carbon dioxide, sugars, proteins, organelles, etc.)

14. Concentration is the amount of solute in a certain amount of solvent
High concentration means there is a lot of solute compared to the amount of solvent (Ex. Strong Kool Aid – 4 Tsp sugar to 8 oz water)
Low concentration means there is a little solute compared to the amount of solvent (Ex. Weak Kool Aid – 1 Tsp sugar to 8 oz water)

16. What are the three types of solutions
What are the three types of solutions? When you compare the solution outside of a cell to the inside of the cell (cytoplasm), there are 3 possibilities:
Hypotonic Solution – has a lower concentration of substance than the cytoplasm of the cell

17. What are the three types of solutions
What are the three types of solutions? When you compare the solution outside of a cell to the inside of the cell (cytoplasm), there are 3 possibilities:
Isotonic Solution – has an equal concentration of substance to the cytoplasm of the cell

18. What are the three types of solutions
What are the three types of solutions? When you compare the solution outside of a cell to the inside of the cell (cytoplasm), there are 3 possibilities:
Hypertonic Solution – has a higher concentration of substance than the cytoplasm of the cell

19. Comparing Concentration of the Cytoplasm to the Concentration of the Solution Outside of the Cell
The outside has a lower concentration than Cell A (hypotonic)
The outside has a higher concentration than Cell B (hypertonic)
The outside has an equal concentration to Cell C (isotonic)

20. Where will substances move?
If nothing prevents them from doing so, substances will always move from areas of high concentration to areas of low concentration