Episode 35 reviews graphing essentials and the relationship to energy. It's important to use the most appropriate graph for the data set.
Episode 35 reviews graphing essentials and the relationship to energy. It's important to use the most appropriate graph for the data set (1:10). Do you remember DRY MIX TAILS? (1:50) Energy can be transferred and transformed, but not created or destroyed. (3:00) Imagine yourself walking along an energy graph, over the activation energy hill, and then either up to a plateau for endergonic or down to a valley for exergonic reactions (4:20). Match each graph with a reaction you are already familiar with.
The Question of the Day asks (6:21) “What does ADP stand for?”
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Hi and welcome to the APsolute Recap: Biology Edition.
Today’s episode will recap Energy and Graphing
Lets Zoom out:
One of the most challenging parts of science is interpreting scientific models. These diagrams, charts, simulations and graphs try to demonstrate something about the natural world. It is our role to extrapolate what we can from the models, apply information and make predictions. You will not be required to create a graph on the 2020 exam - however FRQ 1 is interpreting and evaluating experimental results. You will be questioned about an authentic scenario accompanied by data in a table and or graph.
Lets Zoom in:
Graphs come in many forms, depending on the type of data being represented. Does your question talk about a range of data points or groups? You need a frequency plot, such as box & whisker, dot or histogram. Does your question need to compare two or more qualitative groups? You may also need a frequency plot or maybe a bar graph. It's common to include error bars (2x SEM for Biology) on these graph types. Does your question compare two quantitative variables? Then you’ll need a scatter plot or line graph. If your question investigates parts of a whole, you’ll use a pie chart or stacked bar chart.
Let’s assume you’re using the right graph for your data - congrats! The work is not done yet. Graphing hack - DRY MIX TAILS. DRY - The dependent variable, also known as the responding variable is graphed on the Y axis. DRY. The y axis is vertical on a graph (just like the tail of the letter y goes up and down). The dependent variable is the output of the experiment, what is being measured by the scientists as a result and typically entered in a data table. MIX - the manipulated variable, also known as the independent variable is graphed on the X axis. MIX. The x axis is horizontal on a graph. This is the variable that the scientists are changing on purpose. All graphs should also have TAILS - Title - appropriate and descriptive, axis labeled with each variable and units (because numbers without units have no meaning), intervals - the numbers are equally spaced in value and graphing distance, legend (also known as a key) and usually color coded, scaled to your data with minimum and max values. You don’t want most of the graph to be empty space. TAILS. All together? Graphs have DRY MIX TAILS.
The title of this episode is energy and graphing - so lets recap energy first and then put the two together. The first law of thermodynamics states that the energy of the universe is constant. Energy can be transferred and transformed, but it cannot be created or destroyed. This is the primary piece of information behind energy graphing as most reactions in biology participate in the transfer or energy from one form into another. We maximize our efficiency during energy transfers through sequential biological pathways where the product of one reaction step is often the reactant for the next. We also use enzymes - biological catalysts that lower the activation energy for a reaction to occur.
All molecules have energy stored in chemical bonds, with some having more energy than others. It breaks every chemist's heart when biology teachers say that energy is released when bonds are broken. Right? ATP loses a phosphate and becomes ADP, quote un quote “releasing energy.” Breaking bonds requires energy. The emphasis needs to be on the remaining energy of the products - are they at a lower or higher energy level than reactants? Reactions require an input of energy, known as activation energy to occur. Enzymes reduce how much energy is required for a chemical reaction to continue and thus, makes metabolism more efficient. Note that the difference in energy from reactants to products remains the same in a catalyzed vs uncatalyzed reaction.
OK - combining the two: energy and graphing. We are going to analyze two graphs to distinguish between energy storing and energy releasing reactions. The y axis is Gibbs free energy and the x axis is time. The line drawn on the graph shows how the energy level changes over time during a chemical reaction. Energy levels increase in both graphs at first, with the peak of each curve representing activation energy. This hill will be smaller in catalyzed reactions.
Exergonic reactions have energy exiting the system with reactants at a higher energy level than products. These reactions have a negative delta G (free energy value) and are spontaneous. Imagine yourself walking along the graphed line - You go up and over the hill, then land in a lower valley. Examples of exergonic reactions include the formation of ADP and the process of cellular respiration. Energy cannot be created or destroyed - just transferred. Cellular respiration transfers energy from glucose into ATP (with many steps in between).
Endergonic reactions require additional energy with reactants at a lower energy level than products. Energy is stored in these products. These reactions have a positive delta G and are not spontaneous. Imagine yourself walking along the graphed line - You go up and over the hill, coming down only partially before landing on a plateau. Examples of endergonic reactions include the formation of ATP and the process of photosynthesis. Where does this input of energy come from? Well for ATP - perhaps its chemiosmosis through ATP synthase. For photosynthesis? Thank you for the sunlight.
To recap….
Graphs tell the story of experiments, but it is up to you to interpret them. Don’t forget DRY MIX tails and please always include units with your numbers. Endergonic reactions land the products on a plateau whereas exergonic reactions fall into a valley.
Today’s Question of the day is about energy
Question “What does ADP stand for?”
Coming up next on the Apsolute RecAP Biology Edition: Signal Transduction and the Nervous System