Notes on Homeostasis Homeostasis biological balance cells keeping

Notes on Homeostasis

Homeostasis – “biological balance” cell(s) keeping a steady state with or in spite of the environment • homeo - same • stat - steady

Homeostasis Regulation of the internal environment to maintain constant, favorable conditions Every cell, tissue & organ in the human body contributes toward total body homeostasis

Ex: Body is cold (low temp), you begin to shiver to raise body temperature Ex: Your blood oxygen level is low**, your respiratory rate increases to meet this O 2 need (raise blood O 2) **generalization

Ex: Blood collects & carries wastes from all tissues toward kidneys, which then filter blood & send waste materials toward excretory system

Ex: Enzymes used in producing sperm function best at 2 -3° lower than regular body temperature.

What determines a cell’s set of homeostatic conditions? The metabolic needs of the cell.

Homeostasis • In the human body, these are the conditions • of homeostasis: –p. H of human blood is: 7. 4 –Normal body temp is: 98. 6 ºF (or 37 ºC) –Saline concentration in blood is: 9 g salt per liter –Regular blood glucose level is: 100 -150 mg/d. L Clearly, homeostasis does NOT mean conditions are equal to the conditions of the environment

Write down the key ideas from the following video clip dealing with metabolism and homeostasis; use these for your Frayer Model in comp book!.

The BIG idea: Because the cell membrane is the interface between the cell and the external environment, the cell membrane plays a MAJOR role in governing homeostasis for the cell.

Review…. Solute: Any substance that is dissolved in water is a solute. Example: salt Solvent: The liquid in which a solute is dissolved Example: water (of the saltwater ) Solution: A liquid that contains one or more solutes Example: Water with sugar and/or salt Concentration: The mass of solute in a given volume of solution. Concentration, then, just means how “salty” the water is. What are two methods for changing a solution’s concentration?

New idea: Concentration Gradient • A concentration gradient is a difference between two solutions that are separated by space or a barrier. Notice these two “salt” solutions: One solution is saltier than the other. What do you think will happen to the salt particles over time?

Definition K A separation of two different concentrations of a solution. K Na Na K K l e K si de t u O th l ce K K K th e K K K id s K In K K K l ce l concentration gradient Na Na Na ll ce e Na de th ll Na e i c Na uts e th O e Na id Na s In Na Na Na Equilibrium / Equal on both sides

In cells, concentration gradients occur at the cell membrane— between the intracellular and extracellular environments. Interacting with the concentration gradient is how the cell membrane helps to maintain homeostasis.

Cell membrane – regulates what enters and leaves the cell Semipermeable membrane – keeps out some molecules but allows others to enter

Structure of the Cell membrane • composed of a bilayer of phospholipids and proteins

Structure of Nonpolar

• regulates what enters and leaves the cell – selectively permeable (semipermeable) • Keeps out some molecules but allows others to enter

Movement across the cell membrane: 2 types: 1. passive transport 2. active transport

1. Passive transport – does not require cellular energy A. Diffusion – movement of molecules from areas of greater concentration to areas of lesser concentration Particles move WITH the concentration gradient.

Diffusion with no membrane: Diffusion across a membrane:

Once the concentration of the molecules is the same, dynamic equilibrium has been reached… There is no NET change of concentration Molecule of dye Membrane Equilibrium

Human body examples of Diffusion: • Oxygen diffusing from lungs to blood • Carbon dioxide diffusing from blood to lungs • Nitrogenous waste diffusing from blood in the kidneys into urine • Food particles absorbed in the small intestine from the digestive tract. What is the homeostatic role of the cell membrane in processes of diffusion?

B. Facilitated diffusion – molecules that can not cross the cell membrane’s lipid bilayer directly are guided through the protein channels • example: glucose

Solute Cell Membrane Protein Channel What is the homeostatic role of the cell membrane in processes of facilitated diffusion?

C. Osmosis – diffusion of water across a membrane In osmosis, solute isn’t moving, but the solute is the reason for water movement Hypotonic – concentration of solute molecules in the environment is lower than in the cell HYPO could make a cell POP

• “hypo” means lower • water comes in and the cell swells

Hypertonic – concentration of solute molecules in the environment is greater than in the cell • “hyper” means higher • water leaves and the cell shrinks HYPER will make a cell SHRINK

Isotonic – concentration of solute molecules in the environment is equal to the inside of the cell • “iso” means equal • cells neither gain nor lose water

Examples: Salty water will be hypertonic to a cell Distilled water will be hypotonic to a cell

Plant cells swell until they are restricted by the cell wall • this sets up turgor pressure and result in the cell becoming rigid

Water leaves (loss of turgor pressure) the plant cell wilts • This condition is known as plasmolysis

If too much water enters an animal cell, the cell will burst - this is called cytolysis What is the homeostatic role of the cell membrane in processes of osmosis?

ISOTONIC SOLUTION HYPERTONIC SOLUTION (1) Normal (2) Lysing (3) Shriveled ANIMAL CELL Plasma membrane PLANT CELL (4) Flaccid (5) Turgid (6) Shriveled

Animal Type of cell - ______ hypertonic Type of solution - _______ 8. 5% Na. Cl 91. 5% H 2 O out How will water move? _____ 45% Na. Cl 55% H 2 O osmosis By what process? _______ in How will salt move? ______ diffusion By what process? ________ shrink in size What will happen to the cell? _______ plasmolysis Biological term - _________

Plant Type of cell - ______ hypotonic Type of solution - _______ in How will water move? _____ 8. 5% Na. Cl 91. 5% H 2 O 0% Na. Cl Distilled water osmosis By what process? _______ 100% H 2 O out How will salt move? ______ diffusion By what process? ________ swell and become rigid What will happen to the cell? _______ turgor pressure Biological term - _________

Passive Transport high low

2. Active transport – requires cellular energy • materials move from an area of lesser concentration to an area of greater concentration

• In active transport, materials are moved against the concentration gradient. • Types of active transport are found in: – protein pumps – endocytosis – exocytosis

Types of Active Transport A. A Protein Pump pushes substances against their concentration gradient in order to keep the amounts that the cell prefers. Example: Nerve cells use a sodium-potassium pump to keep desirable concentrations inside the cell. During a nerve impulse, protein channels OPEN, all solutes diffuse with the concentration gradients, but away from the desired levels…oh no!!! That’s where the sodium-potassium pump comes in…see next slide…--pumping things back so that there IS the desired concentration gradient.

• example: the sodium-potassium pump • sodium (out) and potassium (in)

Proton Pump Link to online video

Active Transport Endocytosis vs. Exocytosis Online link to video clip

B. Endocytosis – passage of large molecules into the cell through the cell membrane

• The material is enclosed in a vesicle which pinches off from the cell membrane

• 2. Phagocytosis is the process of large particles being taken into the cell by means of extensions of cytoplasm that go out and engulf the large particles. • This is a leukocyte (white blood cell) in • your blood that is shooting out extensions • to get the large particles that you see.

a. pinocytosis – movement of solutes or fluids • pino = to drink

b. phagocytosis – movement of large food particles or whole organisms • phago = to eat • example: WBCs, amoeba

C. Exocytosis – passage of unwanted and/or large molecules through the cell membrane to the outside

• excretions and secretions; Golgi body

• Excess water; contractile vacuole of some protists. What is the homeostatic role of the cell membrane in processes of active transport?

Active Transport high ENERGY low

True/False Discussion “The cell membrane maintains homeostasis by allowing solutes to reach equilibrium. ” “The cell membrane maintains homeostasis by preventing solutes from reaching equilibrium. ” “The cell membrane maintains homeostasis by preventing the diffusion of large molecules. ”

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