1. Homeostasis

2. Homeostasis Keeping an organism’s internal environment stable Examples
Blood pressure
60% H2O
Water balance
Temperature pH

3. homeostasis
“the tendency of an organism or cell to regulate its internal environment and maintain equilibrium, usually by a system of feedback controls, so as to stabilize health and functioning”

4. Feedback Mechanisms
Help the organism respond to stimuli and maintain homeostasis on a large scale (whole body)
Negative Feedback
Positive Feedback

5. shiver, blood vessels constrict and lower blood flow to the skin
Negative Feedback
When a situation causes a response that reverses the first condition
Most common in the body
COLD
skin cells detect cold
brain gets message
normal body temp
home thermostat (heating system). The thermostat contains the receptor (thermometer) and control center. If the heating system is set at 70 degrees Fahrenheit, the heat (effector) is turned on if the temperature drops below 70 degrees Fahrenheit. After the heater heats the house to 70 degrees Fahrenheit, it shuts off effectively maintaining the ideal temperature.
response
shiver, blood vessels constrict and lower blood flow to the skin

6. normal blood glucose level normal blood glucose level
Pancreas secretes insulin
Liver coverts glucose to glycogen
Too High
Blood glucose level falls
Soon after a meal
normal blood glucose level
normal blood glucose level
Too Low
Pancreas secretes less insulin
Blood glucose level rises
Long after a meal
The control of blood sugar (glucose) by insulin is another good example of a negative feedback mechanism. When blood sugar rises, receptors in the body sense a change . In turn, the control center (pancreas) secretes insulin into the blood effectively lowering blood sugar levels. Once blood sugar levels reach homeostasis, the pancreas stops releasing insulin.
Liver converts glycogen to glucose

7. Positive Feedback
When a situation causes a response that amplifies (increases) the initial (1st) condition
Ex. Milk production, labor pains, blood clots
A positive feedback mechanism is the exact opposite of a negative feedback mechanism. With negative feedback, the output reduces the original effect of the stimulus. In a positive feedback system, the output enhances the original stimulus. A good example of a positive feedback system is child birth. During labor, a hormone called oxytocin is released that intensifies and speeds up contractions. The increase in contractions causes more oxytocin to be released and the cycle goes on until the baby is born. The birth ends the release of oxytocin and ends the positive feedback mechanism.
Another good example of a positive feedback mechanism is blood clotting. Once a vessel is damaged, platelets start to cling to the injured site and release chemicals that attract more platelets. The platelets continue to pile up and release chemicals until a clot is formed.

8. On a small scale, individual cells maintain homeostasis by controlling what gets into and out of a cell.

9. Cell transport Cells move molecules in and out 2 ways:
PASSIVE TRANSPORT: does not use energy, moves from high to low concentration.
ACTIVE TRANSPORT: uses energy, moves from low to high concentration.

10. How do materials move in & out of the cell?
Materials like glucose, water, solutes, and oxygen can move through the cell membrane in one of two ways:
Between the phospholipids
Through a carrier protein

11. Moving between phospholipids
There is a small amount of space between the round heads of the phospholipids that make up a majority of the cell membrane.

12. Moving through carrier proteins
Carrier (enzyme) proteins allow larger molecules to pass through
Sugars, amino acids, small proteins
Molecules “too big” to fit between phospholipids

13. Solutions Solutions are mixtures of different substances:
Solvent: the medium in which a substance is dissolved
Solute: the substance dissolved in the solvent
Solution: the uniform mixture of the solute and solvent
Example – Kool-Aid (solution) = Solvent is water and powder is the solute
Medium = an intervening substance (water)
Solvent > Solute

14. Solutions
Molecules move to equalize concentration

15. Concentrations Anything that is dissolved in water is called a SOLUTE
E.g. In sugar water, the solute is sugar. In salt water the solute is salt
90% water concentration = 10% solute concentration
40% water concentration = 60% solute concentration

16. PASSIVE TRANSPORT
Molecules move with the flow, from high to low concentrations.
No Energy Required!
This will continue until they are evenly spread out or reached equilibrium
3 Types:
Diffusion
Facilitated Diffusion
Osmosis

17. PASSIVE TRANSPORT - Diffusion
Diffusion: the movement of molecules from areas of high concentration to areas of low concentration

18. Diffusion

20. Gas spreads out by diffusion!

21. Diffusion

22. PASSIVE TRANSPORT – Facilitated diffusion
Facilitated Diffusion: Movement of molecules from high to low concentration.
A protein in the membrane helps make bigger spaces in the membrane.

23. Facilitated Diffusion
3. Movement of larger molecules (ex. glucose) from high concentration to low concentration with the help of a carrier protein
inside cell
outside cell

24. PASSIVE TRANSPORT - Osmosis
Greek, osmos “to push”
Osmosis: movement of water from high to low concentration across a membrane.
Specific type of Diffusion – Water
The movement of water across a membrane from an area of high concentration of water to an area of lower water concentration
Remember what a solution is and the parts of a solution?

25. Osmosis

26. PASSIVE TRANSPORT - Osmosis
Need to understand the concentrations of solvents & solutes on either side of the membrane.

28. 90% Water
70% Water
80% Water
80% Water

29. Water moves from high concentration of water
to lower concentration of water
15% Sugar
(85% H2O)
H2O
H2O
30% Sugar
(70% H2O)
Cell
H2O
H2O
Environment

30. Diffusion / osmosis and cells
Solutions are classified in 3 ways based on their concentrations of water in relation to the inside of cells
Hypertonic: Higher H2O concentration inside the cell
Hypotonic: Higher H2O concentration outside the cell
Isotonic: Equal concentrations of H2O inside and outside the cell

32. Isotonic solution When the cell is at equilibrium with
its environment, equal amounts of
water move into and out of the cell
In isotonic solutions, animal cells will have no net change because the water inside is equal to the concentration outside.
60% H2O

33. Hypertonic solution
When there is more water in a cell than outside of a cell, water will leave the cell.
This can cause a cell to shrink
2% H2O
75% H2O
In hypertonic solutions, animal cells will loose water because The water inside is a higher concentration outside. The rules of diffusion/osmosis say that water will move from the area of high concentration to low concentration

34. Hypotonic solution
When there is more water outside a cell than inside of a cell
Water will enter the cell
This can be bad, if too much water enters then the cell may lyse (burst)  Cytolysis
80% H2O
60% H2O
In hypotonic solutions, animal cells will gain water because The water inside is a lower concentration than outside. The rules of diffusion/osmosis say that water will move from the area of high concentration to low concentration

39. The effects of diffusion & osmosis on living cells
Both diffusion and osmosis will result in changes to living cells
The movement of water & other solutes back and forth across the membrane will change the volume and pressure inside of the cell
Since plant cells are surrounded by a rigid outer layer, the overall shape will NOT change, but the pressure inside will

40. PLASMOLYSIS
Plant cells respond differently to osmosis because of their cell wall
When water leaves a plant cell, the cell wall’s shape does not change, but the cell membrane pulls away and creates an air pocket between the two. This causes the plant to WILT.
85% H2O
5% H2O

41. Turgor Pressure
When water enters a plant cell, the cell membrane pushes against the cell wall and creates pressure.
85% H2O
98% H2O

43. Active transport
Move molecules against the flow, from low to high concentration.
Uses ENERGY!
Its like pushing something up hill instead of letting it roll downhill

44. ENERGY!

45. Active transport For Multicellular Organisms:
Uses a carrier protein, to carry them across the membrane

46. Active transport For Unicellular Organisms
VESICLE --> organelle that transports materials through, into, or out of a cell
ENDOCYTOSIS --> into the cell
vesicle
Pinocytosis --> fluids
Phagocytosis --> foods

47. Active transport
EXOCYTOSIS --> out of the cell

48. Process of Endocytosis
Plasma membrane surrounds material
Edges of membrane meet
Membranes fuse to form vesicle

49. Exocytosis
Reverse of endocytosis
Cell discharges material

50. Exocytosis Vesicle moves to cell surface Membrane of vesicle fuses
Materials expelled