1. Introduction to Cell Transport and the Cell Membrane

2. Why do we need to move things in and out of cells (think of specific examples)?
1) We need to get necessary materials into cells
Cells need to get oxygen and glucose for cell respiration
Cells need nutrients (proteins, lipids, cholesterol) to help build/repair cell structures

3. Why do we need to move things in and out of cells (think of specific examples)?
2) We need to get wastes out of cells.
Cells produce waste products like Carbon dioxide and extra water that need to be removed from cells

4. What materials go “IN” to cells?
Water
Glucose
Salt
Ions
Lipids
Amino acids

5. What materials go “OUT” of cells?
Carbon dioxide
Waste materials
Ions
Water

6. Transport can be as simple as moving materials between a one celled organism and its environment…
O2 in
CO2 Out
Does a one-celled organism have organ systems which aid in transport ? NO

7. …or as complex as the transport systems in higher organisms such as humans.
wastes
Blood vessel

8. Which organ systems aid higher animals in transporting materials throughout the body?
Circulatory
Respiratory
Digestive
Nervous

9. What is the boundary that controls what goes in and out of cells?
Cell membrane

10. Let’s Review what we already know about cell membranes?
They surround the entire cell
They are made of phospholipids
Phospholipids have a head and two fatty acid tails

11. Polarity AGAIN? The head of a phospholipid is polar.
The tails of a phospholipid are non-polar.
Water is polar.
Which end do you think likes to mix it up with water?
That’s right, the polar head.

12. Hydrophylic or Hydrophobic
Hydro = water
Phylic = loving
Phobic = hating
Which part of the phospholipid is hydrophylic? Which part is hydrophobic?
Head = hydrophylic, Tail = Hydrophobic

13. So why do cell membranes have two layers of phospholipids?
HINT: Look at the arrangements of the phospholipids in the diagram below.
HINT 2:Look at where the water is. Think. Is water polar or non polar? What would like to be next to the polar water….hydrophylic or hydrophobic?

14. All cells live at least PARTLY in touch with WATER (in AND out)
When these lipids are mixed with water, their hydrophobic fatty acid tails cluster together while their hydrophilic heads are attracted to water.
A lipid bilayer is the result

15. Fluid Mosaic Model

16. Fluid Mosaic Model
Protein molecules are embedded and “float” among the lipids in the bilayer of most cell membranes.
Many different kinds of molecules make up the cell membrane (carbohydrates, cell communication molecules)
This is described the membrane as a fluid mosaic.

17. What are these different molecules doing?
PROTEINS
CARBOHYDRATES
Form channels/pumps to help move material across the cell membrane.
Attach directly to the cytoskeleton, enabling cells to respond to their environment by using their membranes to help move/change shape
Many act like chemical identification cards, allowing individual cells to identify one another.

18. How can we describe what can get through the cell membrane?
Cell membranes are semi-permeable or Selectively Permeable Membranes can be permeable to some things and impermeable to others.

19. Permeable… Permeable means that a substance is allowed to pass through
If a cell membrane is permeable to a substance, diffusion proceeds normally. X O X O X O O X

20. Impermeable…
Impermeable means a substance will not be allowed to pass through
If the membrane is impermeable to a substance, diffusion will not occur O X X

21. Semipermeable…
Most cell membranes are selectively permeable. Only certain substances are allowed into or out of a cell O X X X X

22. What does this all add up to?
Moving the right things in or out of a cell
in the right amounts
at the right time
For the right metabolic processes
Helps cells maintain homeostasis

23. What are the methods for moving things in and out of cells?
1) Passive transport
Movement of things across the membrane from high concentration to low concentration without the use of ATP
Special Case 1: movement of water is called Osmosis
Special Case 2: some necessary nutrient move with the gradients but are too big to slip through the phospholipids or have charges – so they use a a transport protein – called Facilitated Transport

24. What are the methods for moving things in and out of cells?
2) Active Transport – moving things AGAINST the gradient
Requires ATP
Requires Transport Proteins

25. What are the methods for moving things in and out of cells?
3) Endo/ Exocytosis – cell membrane folds around something to move it into or out of the cell.
Requires ATP
Is a form of Active Transport