Phenomenon
Plants have small pores on their leaves called stomata (a single pore is a stoma). Below shows cells called guard cells that control the opening and closing of the stomata. In some plants, stomata typically open more in the nighttime, and stay closed in the daylight.
Image by Ali Zifan; https://commons.wikimedia.org/wiki/File:Opening_and_Closing_of_Stoma.svg#/media/File:Openi ng_and_Closing_of_Stoma.svg; CC BY-SA 4.0
Observations and Wonderings
Focus Questions: Give your best response prior to learning about this topic. Your initial answers may change as you explore this unit.
Bio.2.1 Macromolecules
What makes up a healthy diet?
A healthy diet includes protein, fats, and carbohydrates. Why? Because these compounds are three of the main building blocks that make up your body. You obtain these building blocks from the food that you eat, and you use these building blocks to make the organic compounds necessary for life.
The main chemical components of living organisms are known as organic compounds. Organic compounds are molecules built around the element carbon
(C). Living things are made up of very large molecules. These large molecules are called macromolecules because “macro” means large; they are made by smaller molecules bonding together. Our body gets these smaller molecules, the “building blocks” of organic molecules from the food we eat.
The four main types of macromolecules found in living organisms, shown in the table below, are:
Review the elements found in each type of macromolecule. What pattern do you see?
Carbon, hydrogen, oxygen, and nitrogen are the building blocks for the macromolecules our cells need to function. Each macromolecule has a different function.
Carbohydrates
Carbohydrates are sugars. Cells use carbohydrates for energy. Some carbohydrate molecules, such as glucose, are relatively small, and are called simple sugars. Glucose has the chemical formula C6H12O6. Other carbohydrates are made of many simple sugars connected together into a long chain. These long chains often consist of hundreds or thousands of simple sugars. Plants store sugar in large molecules called
starch. Animals store sugar in large molecules called glycogen. You get the
carbohydrates you need for energy from eating carbohydrate-rich foods, including fruits and vegetables, as well as grains, such as bread, rice, or corn.
Lipids
Have you ever tried to put oil in water? They don’t mix. Oil is a type of lipid. Lipids are molecules such as fats, oils, and waxes. The most common lipids in your diet are probably fats and oils. Animals use fats for long-term energy storage and to keep warm. Plants use oils for long-term energy storage. When preparing food, we often use animal fats, such as butter, or plant oils, such as olive oil or canola oil. There are many more types of
lipids that are important to life. One of the most important are the phospholipids that make up the protective outer membrane of all cells.These lipid membranes are impermeable to most water soluble compounds.
Phospholipids in a membrane, shown as two layers (a bilayer) of phospholipids facing each other.
Nucleic acids
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two main nucleic acids. DNA is a double-stranded nucleic acid. DNA is the molecule that stores our genetic information. DNA contains the instructions to build proteins, and is the molecule that stores genetic information and is passed from parent to offspring. The single-stranded RNA is involved in making proteins.
Proteins
Proteins are molecules that have many different functions in living things. It’s important for you and other animals to eat food with protein, because we cannot make certain amino acids on our own. You can get protein from plant sources, such as beans, and from animal sources, like milk or meat. When you eat food
with protein, your body breaks the proteins down into individual amino acids and uses them to build new proteins. You really are what you eat!
All proteins are made of smaller molecules called amino acids that connect together like beads on a necklace.
Proteins do all of the work in cells. Some proteins help move molecules into and out of the cell. Other proteins break down molecules or build molecules. Every protein has a unique function. The order of the amino acids determines the function of the protein.
Enzymes are special proteins
Most of the biochemical reactions that happen inside of living organisms require help. Why is this the case? For one thing, temperatures inside living things are usually too low for biochemical reactions to occur quickly enough to maintain life. The concentrations of reactants may also be too low for them to come together and react. Where do the biochemical reactions get the help they need to proceed? From the enzymes.
An enzyme is a protein that speeds up a biochemical reaction. It is a biological catalyst. An enzyme generally works by reducing the amount of activation energy needed to start the reaction. The graph below shows the activation energy needed for glucose to combine with oxygen. Less activation energy is needed when the correct enzyme is present than when it is not present.
Enzyme Action. This graph shows what happens when glucose combines with oxygen. An enzyme speeds up the reaction by lowering the activation energy. Compare the activation energy needed with and without the enzyme.
How Well Enzymes Work
Enzymes are involved in most biochemical reactions, and they do their jobs extremely well. A typical biochemical reaction that would take several days or even several centuries to happen without an enzyme is likely to occur in just a split second with the proper enzyme! Without enzymes to speed up biochemical reactions, most organisms could not survive.
Phenomenon
Image by Ali Zifan; https://commons.wikimedia.org/wiki/File:Opening_and_Closing_of_Stoma.svg#/media/File:Openi ng_and_Closing_of_Stoma.svg; CC BY-SA 4.0
Focus Questions
Final Project
Keep a log of your diet for three days. Using a spreadsheet or journal, record the number of grams of carbohydrates, fats, and proteins– for each packaged food item you eat. Add up your daily total grams of each of these macromolecule groups. After the project, record in your log whether you believe your diet is balanced with respect to these three macromolecules. Also record where you believe nucleic acids (such as DNA) come from, given that they are not listed on a food label.
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