Lab Results: 1. Document the initial and final egg masses. 2. Calculate the percent change

Transcription

1 Lab Results: 1. Document the initial and final egg masses. 2. Calculate the percent change 3. Draw an arrow showing which way water traveled (in or out of the egg) on your post lab.

2 CHI- SQUARE: What if we wrapped THREE eggs with saran wrap and left them out of solution? We decided to calculate the chi-square value of the data from the mass of these three eggs. WHAT COULD OUR NULL HYPOTHESIS BE?

3 The eggs in saran wrap, left out of solution, are serving as a CONTROL in our experiment This means there should be NO change in mass of the eggs! NULL HYPOTHESIS: The final mass will be the exact same as the initial mass. Mass of Eggs INITIAL MASS FINAL MASS EGG g 52.1g EGG g 62.5g EGG g 65.1g PERCENT CHANGE Loss Calculate of 2.4% 0% percent change Loss change of now! 3.3% CHI SQUARE = DO THE MATH! Chi square =0.1

4 How many degrees of freedom? TWO because there were three trials. Read the chart for the chi square value. Remember: To the left of the 0.05 p value means FAIL TO REJECT the null or anything to the right means REJECT the null. Did you reject or fail to reject the null? FAIL TO REJECT What does that mean statistically about the data?

5 WATER POTENTIAL and SOLUTE POTENTIAL: A cell is in equilibrium with its surroundings. The molarity of the surrounding solution is 0.5M. To convert molarity to solute potential in MPa, use the formula: Y S = - ( i CRT ) where: i = ionization constant (assume that is 1) C=molar concentration (given above) R = pressure constant (R= liter MPa/mole o K) T = temperature in o K (room temp is about 293 o K) 1. Calculate the solute potential of the surrounding solution. 2. Find the water potential of the surrounding solution. 3. What is the water potential of the cytoplasm of the cell?

6 1. Y S = Mpa Based on simple calculations 2. Y = Mpa Same as solute potential because we are not given any pressure potential. 3. Y = Mpa The cell is at equilibrium with the environment so it is the same! PAY CLOSE ATTENTION TO THE UNITS and CONSTANTS!

7 Unit 2: Cells, Membranes and Signaling CELL SIGNALING AND COMMUNICATION Chapter 5 Hillis Textbook

8 CELL SIGNALING ANDCOMMUNICATION Cells communicate by responding to signals if they have a specific receptor for that signal Cells are exposed to many signals and may have different responses: Three types of signals: Autocrine signals affect the same cells that release them. Paracrine signals diffuse to and affect nearby cells. Hormones travel to distant cells.

9 PARACRINE Target cells are the cells which will be receiving some sort of message! AUTOCRINE HORMONE **Only cells with the necessary receptors can respond to a signal the target cell must be able to sense it and respond to it. WHAT KIND OF CELL TRANSPORT DO YOU SEE?

10 A signal transduction pathway : sequence of molecular events and chemical reactions that lead to a cellular response, following the receptor s activation by a signal. A signal transduction pathway may produce short or long term responses. A signal transduction pathway involves three things: a signal (like autocrine, paracrine or hormone) a receptor a response

11 A common mechanism of signal transduction is allosteric regulation. This involves an alteration in a protein s shape as a result of a molecule binding to it. A signal molecule, or ligand, fits into a three-dimensional site on the receptor protein. Binding of the ligand causes the receptor to change its three-dimensional shape, which initiates a cellular response. Binding is reversible and the ligand can be released, to end stimulation. An inhibitor, or antagonist, can bind in place of the normal ligand.

12 Receptors can be classified by their location in the cell. This is determined by whether or not their ligand can diffuse through the membrane. Cytoplasmic receptors have ligands, such as estrogen, that are small or nonpolar and can diffuse across the membrane. Membrane receptors have large or polar ligands, such as insulin, that cannot diffuse and must bind to a transmembrane receptor at an extracellular site. Receptors are also classified by their activity: Ion channel receptors Protein kinase receptors G protein linked receptors

13 Ion channel receptors, or gated ion channels, change their three-dimensional shape when a ligand binds. The acetylcholine receptor, a ligand-gated sodium channel, binds acetylcholine to open the channel and allow Na + to diffuse into the cell. Protein kinase receptors change their shape when a ligand binds. The new shape exposes or activates a cytoplasmic domain that has catalytic (protein kinase) activity. Ligands binding to G protein linked receptors expose a site that can bind to a membrane protein, a G protein. The G protein is partially inserted in the lipid bilayer, and partially exposed on the cytoplasmic surface.

14 EXAMPLES: Protein kinases catalyze the following reaction: ATP + protein ADP + phosphorylated protein Each protein kinase has a specific target protein, whose activity is changed when it is phosphorylated.

15 EXAMPLES: Many G proteins have three subunits and can bind three molecules: 1. The receptor 2. GDP and GTP (used for energy transfer) 3. An effector protein to cause an effect in the cell The activated G protein linked receptor exchanges a GDP nucleotide bound to the G protein for a higher energy GTP. The activated G protein activates the effector protein, leading to signal amplification.

16 Signal activation of a specific receptor leads to a cellular response, which is mediated by a signal transduction pathway. Signaling can initiate a cascade of protein interactions the signal can then be amplified and distributed to cause different responses. A second messenger is an intermediary between the receptor and the cascade of responses.

17 In the fight-or-flight response, epinephrine (adrenaline) activates the liver enzyme glycogen phosphorylase. The enzyme catalyzes the breakdown of glycogen to provide quick energy. Researchers found that the cytoplasmic enzyme could be activated by the membrane-bound epinephrine in broken cells, as long as all parts were present. They discovered that another molecule delivered the message from the first messenger, epinephrine, to the enzyme. The second messenger was later discovered to be cyclic AMP (camp). Second messengers allow the cell to respond to a single membrane event with many events inside the cell they distribute the signal. They amplify the signal by activating more than one enzyme target.

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19 Signal transduction pathways involve multiple steps enzymes may be either activated or inhibited by other enzymes. In liver cells, a signal cascade begins when epinephrine stimulates a G protein mediated protein kinase pathway. Epinephrine binds to its receptor and activates a G protein. camp is produced and activates protein kinase A it phosphorylates two other enzymes, with opposite effects: Inhibition and Activation

20 PROTEIN KINASE A, when activated, does this: Inhibition protein kinase A inactivates glycogen synthase through phosphorylation, and prevents glucose storage. Activation Phosphorylase kinase is activated when phosphorylated and is part of a cascade that results in the liberation of glucose molecules!

21 Signal transduction ends after the cell responds enzymes convert each transducer back to its inactive precursor.

22 AP BIOLOGY: UNIT 2 MATH PRACTICE CHI SQUARE PRACTICE: Three eggs left out of solution NULL: INITIAL MASS Mass of Eggs FINAL MASS EGG g 52.1g EGG g 62.5g EGG g 65.1g PERCENT CHANGE FIND THE PERCENT CHANGES Find the Chi-square of each trial. Add them together. TOTAL CHI SQUARE:

23 How many degrees of freedom? Read the chart for the chi square value. Remember: To the left of the 0.05 p value means the null or anything to the right means the null. Did you reject or fail to reject the null? What does that mean statistically about the data?

24 WATER POTENTIAL and SOLUTE POTENTIAL: A cell is in equilibrium with its surroundings. The molarity of the surrounding solution is 0.5M. To convert molarity to solute potential in MPa, use the formula: Y S = - ( i CRT ) where: i = ionization constant (assume that is 1) C=molar concentration (given above) R = pressure constant (R= liter MPa/mole o K) T = temperature in o K (room temp is about 293 o K) 1. Calculate the solute potential of the surrounding solution. 2. Find the water potential of the surrounding solution. 3. What is the water potential of the cytoplasm of the cell?

25 CELL COMMUNICATION AND SIGNALING: Three types of signals are: Cells can only respond to a signal if they have A is a sequence of molecular events and chemical reactions that lead to a cellular response, following the receptor s activation by a signal. MUST INCLUDE:, and. What is allosteric regulation: What is a ligand? What is a CASCADE or AMPLIFICATION? What is a second messenger and list an example:

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