Cell Homeostasis

Acids and Bases pH: A number that measures how acidic or basic a solution is. Scale from 0-14; 7 = neutral. Ex. Top of p. 43 pH is very important to living systems

Acids and Bases Acid: Any substance that forms hydrogen ions (H+) when mixed with water. Ex. Hydrochloric acid (HCl) pH below 7, turns litmus paper red Properties: corrosive, sour http://www.lamainverte.be/catalog/product_info.php?products_id=335&language=en

Acids and Bases Base: Any substance that forms hydroxide ions (OH-) when mixed with water. Ex. Sodium Hydroxide (NaOH) pH above 7; turns litmus paper blue Properties: bitter, slippery

pH Scale pH is controlled via buffers. Weak solutions (acids or bases) that prevent drastic changes in pH by reacting with strong acids or bases.

pH Scale Map 0-14 Basic Acidic Neutral

Solutions Solution: when something is dissolved in something else; ex. saltwater Solute: the thing being dissolved Solvent: the thing dissolving it (usually water) Concentration: solute/solvent; the amount of solute per amount of solvent Your body is a solution and cells must maintain proper concentrations!

Transport across the plasma membrane

Diffusion Diffusion : movement of particles from an area of high to low concentration (no energy required) continues until there is no more concentration gradient.

Passive Transport Passive Transport: the process of particles moving through a membrane with NO ENERGY (high to low concentration) Water, lipids, and some lipid soluble substances can move by passive transport. Molecules can move through proteins or the membrane itself. http://www.bmb.psu.edu/courses/bisci004a/cells/faciltat.jpg

Cellular Transport Osmosis: The diffusion of water across a selectively permeable membrane. Review: Plasma Membrane- Phospholipid Bilayer Concentration Gradient Homeostasis Fig. 8.1 p. 202

3 Types of Solutions Isotonic Solution: Concentration of solutes is the same inside and outside the cell. No osmosis occurs dynamic equilibrium: molecules are moving across membrane but no concentration gradient created. Dynamic: Movement or change Equilibrium: An equality or balance

Types of Solutions Hypotonic Solution: The concentration of solutes is less outside the cell than inside the cell. See p. 186, Fig. 7.16 Water moves by osmosis into the cell! The cell tends to swell.

Types of Solutions Hypertonic Solution: The concentration of solutes is more outside the cell than inside the cell. See p. 186 Fig. 7.16 Osmosis causes water to flow out of the cell. Cells will shrink or shrivel

Comparison of Hypo, Iso, and Hypertonic Solutions

Solutions Practice

Sample EOC Question1 A freshwater plant is placed in a container of saltwater. What will most likely happen to the cells of the plant? A They will swell because water will move into them. B They will swell because salt will move into them. C They will shrink because water will move out of them. D They will shrink because salt will move out of them.

Turgor Pressure: The pressure in a plant cell that results from water flowing into the cell. Occurs with a hypotonic solution. Gives plants their shape and ability to stand up. Without it they wilt!

Plasmolysis: Loss of pressure within a cell causing it to shrivel Occurs with a hypertonic solution In plants turgor pressure is lost (wilting occurs), animal cells just shrivel http://www.apsnet.org/online/feature/xmasflower/images/figure22sm.jpg http://www.biology.arizona.edu/cell_bio/problem_sets/membranes/graphics/hypertonic_plt.gif

Facilitated Diffusion: proteins helping large molecules across the plasma membrane. No energy is used by the cell or its parts! (passive) Movement is powered by the concentration gradient. (hi to lo) See p. 187 Fig. 7.17 http://www.mhhe.com/biosci/genbio/enger/student/olc/art_quizzes/genbiomedia/0086.jpg

Cell Membrane Proteins* Carrier Proteins: Span through plasma membrane (transport proteins) and change shape to help molecules get from one side to the other. Their exposed ends open and close like a gate. Channel Proteins: Span through plasma membrane (transport proteins) and create an opening where molecules can pass through. They do not change shape. Carrier Channel http://images.google.com/imgres?imgurl=io.uwinnipeg.ca/~simmons/cm1503/Image132.gif&imgrefurl=http://io.uwinnipeg.ca/~simmons/cm1503/membranefunction.htm&h=311&w=800&sz=42&tbnid=CfM5o08rCDgJ:&tbnh=55&tbnw=141&prev=/images%3Fq%3Dcarrier%2Bproteins%26start%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26sa%3DN

Active Transport Active Transport: cell uses energy to move molecules across plasma membrane against the concentration gradient. These molecules are moving the opposite way they would naturally move due to diffusion. (low-high) http://www.bmb.psu.edu/courses/bisci004a/cells/active.jpg

Active Transport Endo- and Exocytosis Phagocytosis and Pinocytosis is a form of endocytosis Phagocytosis: one cell engulfing another. Pinocytosis: tiny pockets form along the cell membrane fill with liquid and pinch off to form vacuoles within the cell.

Cell specialization

Specialization When a cell or part of a cell has a specific job or function Specialization often arises from some type of survival need Often these are highly developed adaptations

Examples of Specialization in Humans Red Blood Cells Specialized to transport oxygen; contain hemoglobin (protein) and move oxygen from lungs throughout body Sperm Cells Have specialized flagella for propulsion; contain lots of mitochondria for energy production for movement

Examples of Specialization in Plants Vascular Tissue: specialized tissue that transports water and nutrients in certain types of plants 2 TYPES: Xylem: Vascular tissue that carries water from roots to the rest of the plant Phloem: Vascular tissue that carries solutions of nutrients and glucose throughout plants

Examples of Specialization in Unicellular Organisms Eyespots: Group of cells that detect changes in amount of light; helps organism find light for photosynthesis Found in Euglenas (plantlike protists) Contractile Vacuole: Contracts and removes excess water Found in protists Pseudopods: “false foot” Temporary projection of cytoplasm used for feeding or movement Found in protists; ex. amoeba

Examples of Specialization in Unicellular Organisms Left – Euglena Above - Amoeba

Resources Some of the information included in these slides and some slides themselves are either adapted or directly used from powerpoints created by E. Terzian.