Biology Notes

1. Biology Notes Topic: Cell Processes / Achieving Homeostasis AL Biology COS #2 Glencoe High School Mrs. Barkley

2. Alabama Biology Course of Study Objective #2 Describe cell processes necessary for achieving homeostasis, including active and passive transport, osmosis, diffusion, exocytosis, and endocytosis. • Identifying functions of carbohydrates, lipids, proteins, and nucleic acids in cellular activities • Comparing the reaction of plant and animal cells in isotonic, hypotonic, and hypertonic solutions • Explaining how surface area, cell size, temperature, light, and pH affect cellular activities • Applying the concept of fluid pressure to biological systems Examples: blood pressure, turgor pressure, bends, strokes

3. Essential Questions (Cell Processes / Achieving Homeostasis) • Explain why the cell membrane is the site of much biological activity. • Homeostasis is the maintenance of a stable internal environment… What factors does your body work to maintain and keep a constant check on??? • Explain the consequences that could occur if a patient was given pure water instead of saline fluid within an IV. • Explain why you should not drink ocean water, even if appears to be your only source of water…

4. Key Concepts (Cell Processes) #2-1 Word Parts #2-2 Achieving Homeostasis #2-3 Passive Transport #2-4 Osmotic Effect of Solutions #2-5 Active Transport #2-6 Factors That Affect Cellular Activities #2-7 Endothermic vs. Exothermic Reactions #2-8 pH #2-9 Enzyme Action #2-10 Organic Compounds

5. #2-1 Word Parts • homo- / homeo- same • cyt- cell • endo- inside • exo- outside • hyper- above, greater than • hypo- below, less than • iso- equal • therm- temperature

6. #2-2 Achieving Homeostasis Homeostasis • maintenance of a stable internal environment • Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells • What items must enter/exit the cell for it to survive? • What factors does your body keep a constant check on?? 2 Methods of Maintaining Homeostasis 1. Passive Transport 2. Active Transport

7. #2-3 Passive Transport • Passive transport is a method cells use to move materials across a cell membrane, in order to achieve homeostasis.

8. #2-3 Passive Transport • Passive transport is a method cells use to move materials across a cell membrane, in order to achieve homeostasis.

9. #2-3 Passive Transport Example: Diffusion Movement of substances across a cell membrane from a region of high concentration to a region of low concentration Driven by kinetic energy Occurs because a concentration gradient exists (meaning there is a difference in concentration) Water, Oxygen, and Carbon Dioxide easily diffuse through the membrane.

10. #2-3 Passive Transport Example: Fascilitated Diffusion occurs when substances cross membranes from regions of high concentration to regions of low concentration with the assistance of special transport proteins

11. #2-3 Passive Transport Example: Osmosis Diffusion of water across the cell membrane (through aquaporin) Osmosis occurs as cells are exposed to various solutions/fluids within the body. Check out the next slide to see the osmotic effect various solutions have on cells.

12. #2-4 Osmotic Effect of Solutions • Solutions that cells are exposed to can have a dramatic effect on the movement of water (osmosis) through cell membranes. • Use the following terms to (ONLY) describe solutions, based on the concentration level of solutes inside: • Hypotonic • Isotonic • Hypertonic

13. #2-4 Osmotic Effect of Solutions Hypotonic Solutions A hypotonic solution has a lower concentration of solutes than its surrounding environment. This is also the area that the highest water concentration will be found. Therefore, water potential is high. (Solute concentration and water potential are inversely proportional to one another!) A cell placed in a hypotonic solution will have a net gain of water.

14. #2-4 Osmotic Effect of Solutions Isotonic Solutions Isotonic Solutions have a water potential equal to that of its surrounding environment. Water will move into and out of this solution, but in equal amounts. Therefore, a cell placed in an isotonic solution will not experience a net loss or gain of water.

15. #2-4 Osmotic Effect of Solutions Hypertonic Solutions A hypertonic solution has a greater concentration of solutes than its surrounding environment. This is also the area that the lowest water concentration will be found. Therefore, water potential is low. (Solute concentration and water potential are inversely proportional to one another!) A cell placed in a hypertonic solution will have a net loss of water.

16. #2-4 Osmotic Effect of Solutions

17. #2-4 Osmotic Effect of Solutions Because plant cells have a cell wall not present within animal cells, you will notice a couple of differences that plant cells experience during extreme water gain and loss. • Notice that an animal cell may burst (lyse) if too much water enters. However, a plant cell has a cell wall that helps keep it from bursting when placed in a similar solution. The pressure that builds up within the plant cell during this process is called turgor pressure, and the cell is said to be turgid. • Notice than when a plant cell looses too much water, that its cytoplasm will shrink away from its cell wall. This process is known as plasmolysis. Animal cells do not have a cell wall and do not undergo this process.

18. #2-4 Osmotic Effect of Solutions These pictures illustrate red blood cells (RBC) exposed to various solutions. Salt concentration within blood is 0.9% or 9 grams salt per liter blood.

19. #2-4 Osmotic Effect of Solutions When given a problem concerning diffusion or osmosis, be able to answer the following questions. • Does a concentration gradient exist? • Identify the solute within this problem. • Identify the solvent within this problem. • How would you classify the solution within the container (cell’s outside environment)? • How would you classify the solution in the cell? • What direction will water molecules move / What is the “NET” movement of water? (Be able to explain and draw an arrow to indicate your answer.)

20. #2-5 Active Transport Active transport is a method cells use to move materials across a cell membrane, in order to achieve homeostasis.

21. #2-5 Active Transport Endocytosis Particles too large to enter a cell by other methods are transported within a vesicle into the cell through endocytosis.

22. #2-5 Active Transport Exocytosis Sodium Potassium Pumps A substance is secreted from a vesicle out of the cell Removes 3 sodium ion out of a cell while bring 2 potassium ion within a cell

23. #2-6 Factors That Affect Cellular Activities

24. #2-6 Factors That Affect Cellular Activities

25. #2-7 Endothermic vs. Exothermic Reactions Endothermic Reactions absorbs energy in order to proceed environmental temperature drops examples: cold pack, vinegar + baking soda

26. #2-7 Endothermic vs. Exothermic Reactions Exothermic Reactions release energy in the form of heat or light environmental temperature increases examples: hot-hands

27. #2-8 pH • pH is a measurement of percent of hydrogen ions within a solution • pH can be measured with an indicator (something that changes color in the presence of various pH values) such as a dip stick, litmus paper, cabbage juice, and even some flower colors. • Scale ranges from 0-14. • pH level below 7 are considered acidic. • pH levels around 7 are considered neutral. • pH levels above 7 are considered basic/alkaline.

28. #2-8 pH Acids Bases Electrolytes that release hydrogen ions (H+) in water Strong acids can be corrosive Edible acids are often sour Turns litmus paper red Reacts with bases to form water and a salt Below 7 on the pH scale Electrolytes that release hydroxide ions (OH-) in water Strong bases can be corrosive Edible bases are often bitter May be slippery Reacts with acids to form water and a salt Above 7 on the pH scale

29. #2-9 Enzyme Action Enzymes • special proteins • often end in –ase • act on a certain substrate • attach at an active site • speed up chemical reactions • examples: amylase, catalase

30. #2-9 Enzyme Action • Enzyme and Substrate “Induced Fit” Theory Illustrated Below

31. #2-9 Enzyme Action Catalyzed Reaction is represented by dotted line. Un-catalyzed reaction is represented by solid line.

32. #2-10 Organic Compounds • Organic compounds contain carbon and hydrogen. • Organic compounds are generally referred to as non-electrolytes. • 4 Main Types of Organic Compounds: • Carbohydrates • Lipids • Proteins • Nucleic Acids

33. #2-10 Organic Compounds Carbohydrates Lipids Chains of sugars Major sources of energy Have C, H, and O in proportions 1:2:1 Example: glucose “fats” Found within cell membranes Store energy for cellular activities Do not mix with water (insoluble in water) Example: fats, oils

34. #2-10 Organic Compounds Proteins Nucleic Acids Made up of amino acids Enzymes are specialized proteins. Contain genetic information Example: DNA and RNA