1. How the cell membrane helps to maintain homeostasis

2. HOMEOSTASIS Definition: The maintenance of a stable environment.
In cells this happens by monitoring what goes in and out of the cell.

3. Cell Membrane

4. Cell Membrane

5. PROTEINS IN THE MEMBRANE
Proteins - are involved in the passage of molecules through the membrane.
A. Channel proteins - a protein that allows a particular molecule or ion to freely cross the membrane as it enters or leaves the cell. B. Carrier proteins (Transport)- a protein that selectively interacts with a specific molecule or ion so that it can cross the cell membrane to enter or exit the cell.  C. Receptor proteins - A protein that has a specific shape so that specific molecules can bind to them. The binding of a molecule, such as a hormone, can influence the metabolism of the cell.  D. Enzyme proteins - An enzyme that catalyzes  a specific reaction. E. Cell-recognition proteins (Cell surface marker) - Glycoprotein's that identify the cell. They make up the cellular fingerprint by which cells can recognize each other.

6. How Cells Maintain Homeostasis
Passive Transport 1) Movement of any substance across a membrane without the use of chemical energy (ATP). 2) Movement of molecules will go with the concentration gradient (High to Low) 3) Kinetic Energy
Active Transport 1) Movement of any substance across the membrane using chemical energy – ATP 2) Movement of the molecule will go across/against the concentration gradient (opposite-low to high)

7. PASSIVE DIFFUSION FOUR TYPES Diffusion Osmosis Facilitated Diffusion
Diffusion with Ion Channels

8. DEFINITION OF DIFFUSION
The process that molecules or ions spread from an area of high concentration to an area of low concentration
Examples: Air freshener, food coloring in water, sugar cube dissolving
Diffusion

9. What causes Diffusion? The KINETIC ENERGY of the molecules
Diffusion is driven by the molecules’ kinetic energy.
Kinetic Energy – the energy of motion.
Molecules are in constant motion because they have kinetic energy, they will move in a random motion.
If they are concentrated in a small area they will keep rebounding until they spread out

10. Which way will the molecules move?
Particles will move down(go with) the CONCENTRATION GRADIENT
Definition: Difference in concentration of molecules across a distance

11. What do the particles want to reach?
EQUILIBRIUM Definition: When all the molecules are spread out equally in a given area Note: This can be reached in the absence of other influences

12. Diffusion across the Cell Membrane
Cell Membrane is Semi-permeable- It will let some molecules through
Diffusion of a molecule across a membrane depends on the size of the molecule and the solubility (polar, nonpolar)
Small molecules like water are small enough to get through the pores in the membrane and will pass through by Osmosis

13. Molecules that can diffuse through the membrane by Simple Diffusion
Yes! Oxygen (nonpolar) Carbon Dioxide (nonpolar) Water (Osmosis, small enough)
No! Large Particles Starch Ions (Charged Particles) Glucose(Hydrophilic)

14. OSMOSIS
The process by which WATER molecules diffuse through a cell membrane from an area of high concentration to an area of lesser concentration

15. Direction of OSMOSIS
Depends on relative concentration of solute molecules on both sides of the cell membrane
Water will either enter the cell or exit the cell

16. CHEMISTRY REVIEW- What is a solution?
Solute - Item that is dissolved
Ex: Sugar
Solvent - Item that does the dissolving
Ex: Water
In a cell, Water is the solvent and Organic and Inorganic molecules are the solutes.
Give examples of solutes in the cell?

17. Direction of water if cell is placed in a Hypotonic Solution
Hypotonic Solution –When the concentration of solute molecules outside the cell is lower than the concentration of the solute molecules inside the cytosol of the cell.
The outside solution is said to be hypotonic compared to the cytosol inside the cell
Direction of Water: Into the cell
Condition: Cytolysis

18. Direction of the water if a cell is placed in a Hypertonic Solution
Hypertonic Solution- When the concentration of solute molecules outside the cell is Higher than the concentration of the solute molecules inside the cytosol of the cell.
The outside solution is said to be hypertonic compared to the cytosol inside of the cell
Direction of Water: Out of the cell
Condition: Plasmolysis

19. Water moves from the hypotonic solution to the hypertonic solution
REMEMBER
Water moves from the hypotonic solution to the hypertonic solution

20. VOCAB WORDS
Osmotic Pressure – The ability of osmosis to generate enough pressure to increase a volume of water
Turgor Pressure - Water pressure within a cell
Plasmolysis- When water leaves the cell and turgor pressure is lost and the cell shrinks
Cytolysis – When the cell takes in so much water it bursts caused by an increase in turgor pressure
Contractile Vacuoles – Organelles that remove water

21. QUESTIONS?
What type of solutions would a cell have to be in for cytolysis to occur? Plasmolysis to occur?
If you were to place celery into a glass of water, would you have cytolysis, plasmolysis or neither?

22. Plant vs. Animal Cell

23. FACILITATED DIFFUSION
Used when molecules are too large to pass through membrane or are not soluble in the membrane
These molecules moves with the concentration gradient
Do not use cellular energy-Passive Transport

24. Carrier Proteins (Transport)
Carrier Proteins transport solute molecules through the membrane without expending energy. Transport molecules that can’t get through the membrane by simple diffusion Are specific to one Molecule ! Like a Key.

25. FOUR STEPS
Molecule will bind with a carrier protein on the surface of the cell membrane
The carrier protein will change shape shielding the molecule from the interior of the cell membrane
The Molecule is released on the other side of the membrane
The carrier protein then returns to its original shape WATCH!

26. FACILITATED DIFFUSION

27. Glucose
Glucose is an excellent example of facilitated diffusion. Cells depend on Glucose to create energy for the cell Glucose is to large of a molecule to pass through the cell membrane and it is not soluble in the lipid bilayer When glucose is low in concentration on the inside it will enter the cell by facilitated diffusion, same if concentration is high on the inside of the cell

28. Ion Channels (Gated/Non Gated)
Proteins in the membrane form an Ion channel across the lipid membrane.
Ions that cannot diffuse through the membrane can move through these channels
Move molecules from high concentration to low w/o use of energy (Passive Transport)
Moves ions such as sodium, potassium, calcium and chloride.
They are specific to one ion. ION CHANNELS

29. Gated Channels Vs. Non Gated
Gated Channels: Open according to external stimuli such as stretching of the cell membrane, electrical signals, and chemicals. Non Gated Channels: Always Open

30. ION CHANNELS

31. ACTIVE TRANSPORT
Moves solutes against the concentration gradient (from low to high)
Particles are moved from areas of LOW concentration to areas of HIGH concentration
Uses energy in the form of ATP
May use a Carrier Protein - Cell Membrane “Pump”

32. PASSIVE VS ACTIVE TRANSPORT

33. EXAMPLES:
Examples of substances that are transported this way: Sugar, amino acids, Sodium, Potassium, Calcium, and Hydrogen ion

34. TYPES:
1. Endocytosis 2. Exocytosis 3. Cell Membrane “Pumps”

35. MOVEMENT IN VESICLES
ENDOCYTOSIS AND EXOCYTOSIS Large Macromolecules can’t get through the membrane with the use of pumps so they need an alternate method These methods require the cell to expend energy

36. ENDOCYTOSIS
The process by which cells engulf substances that are too large to enter the cell by passing through the membrane (using ATP) Items Engulfed: External Fluids, Macromolecules, Large Particle and Cells

37. Process
1. The particle is enclosed by a portion of the cell, called a Vesicle 2. This vesicle then pinches off from the cell membrane and enters the cytoplasm 3. The contents of the vesicle fuse with a Lysosome and are digested by lysosomal enzymes or it can fuse with another membrane-bound organelle WATCH

39. TWO TYPES OF ENDOCYTOSIS
BASED ON MATERIAL TAKEN IN:
Examples: Food Particles, waste materials, proteins
1. Pinocytosis – the movements of solutes or fluids into the cell
2. Phagocytosis – the movement of large food particles or whole microorganisms into the cell
Example:
1. White blood cells engulf and digest bacteria and viruses- PHAGOCYTES
2. Unicellular organisms also feed by endocytosis

40. EXOCYTOSIS (TO EXIT) The passage of large molecules outside the cell
Process is the same as endocytosis but moves the molecules out of the cell (uses ATP) WATCH
Example:
The Golgi Bodies put the proteins in vesicles to be transported out of the cell.
Cells also use this to remove waste from the cell

41. PHAGOCYTOSIS

42. PINOCYTOSIS

43. Sodium-Potassium Pump