1. Some organisms have a CELL WALL
Plants (cellulose)
Algae (polysaccharide)
Fungi (chitin)
Prokaryotes(peptidoglycan)

2. What does the cell wall do?
Scaffolding - mechanical support and structure
Protection
Involved in Cell-cell communication
Maintenance of structure
(turgor)

3. Movement across the cell membrane

4. Where is the water in your body?

6. Where are membranes located?
Cell membrane (double membrane)
Organelles (membrane-bound) can be single or double membrane)
Secret Universe
Introduction to cell membrane

7. What do membranes do?
All cells live in an aqueous environment (surrounded by water, ions and molecules)
…they must control what gets in (nutrients) and out ( waste products and signalling molecules)
they need to communicate with each other…
How is this achieved?....

8. What do membranes do? Protective barrier Cell-Cell signalling
Transport of nutrients, products and waste products
Localisation of function within organelles
Cell membrane function

9. Membranes are: Semi-permeable: controls entry and exit of substances
Self-sealing
Flexible, mobile fluid mosaics

10. Let’s meet the components of the cell membrane

11. Phospholipid bilayer polar hydrophilic heads nonpolar hydrophobic
tails
polar
hydrophilic
heads

12. Substances can be hydrophilic or hydrophobic

15. Membrane Proteins Each membrane has its own unique set of proteins
Proteins act as:
CHANNELS to get substances in or out of the cell or organelle
PUMPS to get substances in or out of the cell or organelle
RECEPTORS to allow the cell or organelle to respond to a stimulus

16. 3.4.2 Explain the importance of the membrane proteins to transport across the membrane

17. Protein channels move substances from one side of membrane to the other

18. Protein pumps move substances from one side of membrane to the other

19. Protein receptors

20. Membranes have sugars (carbohydrates) attached to their surfaces
‘Chemical identification cards’
Used for cell communication
Used by the immune system to identify self or ‘non-self’ (invaders)
The four human blood groups (A, B, AB, and O) differ in the external carbohydrates on red blood cells.

21. Blood cells have glycoproteins (blood type)

22. Let’s Review…
Let's build a membrane from scratch… And now…let’s make a membrane!

24. Movement across the Cell Membrane

25. How do things get into and out of our cells?
PASSIVE MECHANISMS
These don’t require energy
Simple diffusion
Facilitated diffusion
Osmosis
ACTIVE MECHANISMS
These require energy to transport substances (often against their concentration gradient)
Protein pumps
Endocytosis/ exocytosis

26. 3.5.4 State that the energy for diffusion comes from the kinetic energy of random movement of molecules and ions
Particle theory states that all matter consists of many, very small particles, which are constantly moving, or in a continual state of motion. The degree to which the particles move is determined by the amount of energy they have and their relationship to other particles

27. 3.4.2 Explain the importance of the membrane proteins to transport across the membrane

29. 3.5.1: Diffusion: Definition
Diffusion is the net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement
Works for small particles

30. Simple Diffusion
2nd Law of Thermodynamics governs biological systems: the universe tends towards disorder (entropy)
Movement from high concentration of that substance to low concentration of that substance.
Diffusion: movement of small, soluble particles from high  low concentration

31. Diffusion Movement is from HIGH to LOW concentration movement of water
“passive transport”
no energy needed
movement of water
diffusion
osmosis

32. 3.5.3 substances move into and out of cells by diffusion through the cell membrane; this is a dynamic process (always happening)
Gas exchange in the lungs
Gas exchange in plants

33. Gas exchange between lungs and blood is via diffusion

34. Gas exchange in plants is via diffusion

35. 3.4.2 Explain the importance of the membrane proteins to transport across the membrane

36. Facilitated Diffusion
Facilitated diffusion is diffusion of specific molecules through protein channels in the cell membrane
no energy is required
facilitated = with help
open channel = fast transport
high
low
Donuts!
Each transport protein is specific as to the substances that it will translocate (move).
For example, the glucose transport protein in the liver will carry glucose from the blood to the cytoplasm, but not fructose, its structural isomer.
Some transport proteins have a hydrophilic channel that certain molecules or ions can use as a tunnel through the membrane -- simply provide corridors allowing a specific molecule or ion to cross the membrane.
These channel proteins allow fast transport.
For example, water channel proteins, aquaporins, facilitate massive amounts of diffusion.

37. Factors affecting diffusion
Concentration gradient
Temperature
Surface area for diffusion
Distance for diffusion
(size of particle)
(charged or uncharged)

38. Concentration gradient Temperature Surface area for diffusion
Factors affecting the rate of facilitated diffusion are the same as for simple diffusion
Concentration gradient
Temperature
Surface area for diffusion
Distance for diffusion

39. Osmosis
water diffuses through partially permeable membranes from higher to lower concentrations by osmosis
water moves in and out of cells by osmosis through the cell membrane

40. Osmosis: Definition
Osmosis is the net movement of water molecules from a region of higher water concentration [potential] (dilute solution) to a region of lower water concentration [potential] (concentrated solution), through a partially permeable membrane
Like other types of diffusion, osmosis is a dynamic process [achieves balance (equilibrium) but never stops]

41. Movement of water across membranes involves BOTH simple AND facilitated diffusion

42. Factors affecting osmosis
Concentration gradient
Temperature
Surface area for diffusion
Distance for diffusion

43. Comparing ‘water concentration’ of different solutions
Direction of osmosis is determined by comparing total solute concentrations on either side of the membrane:
Hypertonic - more solute, less water
Hypotonic - less solute, more water
Isotonic - equal solute, equal water
hypotonic
hypertonic
water
net movement of water

44. freshwater
balanced
saltwater

45. Osmosis is the diffusion of water across a semi-permeable membrane
Facilitated diffusion of water from high concentration of water to low concentration of water across a semi-permeable membrane

46. Examples of Osmosis in Biology
Absorption of water by plant roots.
Re-absorption of water in the kidney.
Re-absorption of tissue fluid into blood capillaries.
Absorption of water in the GI tract

47. Water moves across a membrane from the hypotonic solution to the hypertonic solution
Animation of osmosis 1
Animation of osmosis 2: why water balance matters

49. How do things get into and out of our cells?
PASSIVE MECHANISMS
These don’t require energy
Simple diffusion
Facilitated diffusion
Osmosis
ACTIVE MECHANISMS
These require energy to transport substances (often against their concentration gradient)
Protein pumps
Endocytosis/ exocytosis

50. Active transport 1: Protein pumps
Active transport uses energy (ATP) to transport substances AGAINST a concentration gradient into/out of the cell
The energy is used to change the shape of the ‘protein pump’ and thus import/export specific molecule
Animation
protein pumps in plants
low
high
ATP

51. 3.6.2 Discuss the importance of active transport as a process for movement across membranes: e.g. ion uptake by root hairs and uptake of glucose by epithelial cells of villi and kidney tubules

52. 3.6.3 Explain how protein molecules move particles across a membrane during active transport

54. Transport summary simple diffusion facilitated diffusion
ATP
active transport

55. Active Mechanisms: Endocytosis and Exocytosis
A simple one...
Animation
Animation 2
Endocytosis/ exocytosis are import/export of materials by infolding/outfolding of the cell membrane

56. Cell responses 3.7
3.7.1 Explain the effects on plant tissues of immersing them in solutions of different concentrations by using the terms turgid, turgor pressure, plasmolysis and flaccid

58. 3.7.3 Explain the importance of osmosis on animal cells and tissues

59. 3.7.4 Explain how plants are supported by the turgor pressure within cells, in terms of water pressure acting against an inelastic cell wall