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

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

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…

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

#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

#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

#2-3 Passive Transport Passive transport is a method cells use to move materials across a cell membrane, in order to achieve homeostasis. QuestionAnswer Energy required? Why does it occur? Movement of molecules? AKA: When does it stop? 3 Examples

#2-3 Passive Transport Passive transport is a method cells use to move materials across a cell membrane, in order to achieve homeostasis. QuestionAnswer Energy required? no Why does it occur? A difference in concentration (concentration gradient) exists between two sides of a membrane Movement of molecules? From high concentration to low concentration AKA: Moving “down the concentration gradient” When does it stop? When equilibrium is reached 3 Examples Diffusion, facilitated diffusion, and osmosis

#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.

#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

#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.

#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: 1. Hypotonic 2. Isotonic 3. Hypertonic

#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.

#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.

#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.

#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.

#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.

#2-4 Osmotic Effect of Solutions When given a problem concerning diffusion or osmosis, be able to answer the following questions. 1. Does a concentration gradient exist? 2. Identify the solute within this problem. 3. Identify the solvent within this problem. 4. How would you classify the solution within the container (cell’s outside environment)? 5. How would you classify the solution in the cell? 6. 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.)

#2-5 Active Transport QuestionAnswer Energy required? Yes Why does it occur? Cell is trying to reach homeostasis Movement of molecules? From low concentration to high concentration AKA: Moving up the concentration gradient When does it stop? When cell reaches homeostasis (NOT when molecules are in equilibrium) 3 Examples Endocytosis, Exocytosis, and the Sodium Potassium Pump Active transport is a method cells use to move materials across a cell membrane, in order to achieve homeostasis.

#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.

#2-5 Active Transport ExocytosisSodium 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

#2-6 Factors That Affect Cellular Activities Characteristic of a CellRelationship to Cell Processes Cell Size _______________ proportional to rate of diffusion Temperature _______________ proportional to cell processes Concentration The concentration of a substance will alter the rate or a reaction. It may speed it up or slow it down. Amount of Enzymes Present _______________ proportional to the rate of a reaction pH level Certain compounds have an optimal pH range.

#2-6 Factors That Affect Cellular Activities Characteristic of a CellRelationship to Cell Processes Cell Size _Inversely _ proportional to rate of diffusion Temperature __Directly__ proportional to cell processes Concentration The concentration of a substance will alter the rate or a reaction. It may speed it up or slow it down. Amount of Enzymes Present __Directly__ proportional to the rate of a reaction pH level Certain compounds have an optimal pH range.

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

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

#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 pH level below 7 are considered acidic. pH levels around 7 are considered neutral. pH levels above 7 are considered basic/alkaline.

#2-8 pH AcidsBases 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

#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

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

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

#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: 1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic Acids

#2-10 Organic Compounds CarbohydratesLipids 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

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