Uploaded June 2015 | Updated September 2026, 2 weeks ago

This is an introduction to the concept of ATP, a key molecule in many areas of biology. Here, we liken ATP to a rechargeable energy currency. ATP is the currency used by cells, but it is not the energy we get from food. Food energy cannot be directly used to power cells; instead it is broken down and that energy is harnessed to recharge "spent" ATP molecules.

ATP is recharged in a cycle. It's high energy form is called ATP and stores energy within its bonds. After the molecule has had some of the bonds broken, it releases energy and becomes its low energy form called ADP. ADP can be "recharged" through the process of cellular respiration for later use.

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[BOGObiology]. (2015, June 19). Photosynthesis 1 ATP Introduction. [Video File]. Retrieved from youtube.com/watch?v=bSycFsWyxbM

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$Properties of Water This video examines waters structure and polarity, its tendency to form hydrogen bonds, and the high specific heat, cohesion, adhesion, surface tension and capillary action that all result from these hydrogen bonds. Water is such a common molecule that we often don’t think about it, but it has many properties that make it crucial for many biological processes. Water Structure: The water molecule is shaped like the letter V, with an oxygen in the center and two hydrogens joined to it by single covalent bonds. Both atoms contribute electrons to the covalent bonds, but the distribution is not equal. Overall the electrons spend more time close to oxygen than they do to hydrogen. This is because oxygen has a higher tendency to attract electrons, a property that we call “electronegativity” . Water Polarity: Why is water polar? Since electrons have a negative charge and they spend a larger part of their time near oxygen, it gives the oxygen a partial negative charge, and the hydrogens a partial positive charge. When a molecule has more positive and more negative regions, we say it is “polar”. Hydrogen Bonds: Why does water form hydrogen bonds? Oppositely charged parts of water molecules are attracted to one another (negative oxygen and positive hydrogen) in what we call hydrogen bonds. It’s very important to remember that water REALLY likes to form hydrogen bonds. One water molecule can form up to four at a time. In liquid water, the hydrogen bonds are weak and last just a fraction of a second before they reform in another configuration. This constant breaking, rearranging and reforming of hydrogen bonds causes many of water’s unique properties, including its heat capacity, cohesion, adhesion, surface tension and capillary action. Specific Heat Capacity: Why does water have high specific heat capacity? Thanks to its hydrogen bonds, water can absorb a very large amount of heat energy without changing into a gas. Water has a high specific heat capacity, which means it needs a lot of heat in order to raise the temperature of 1 gram of water by 1 degree celsius. In short, because water really loves to form hydrogen bonds, it takes a LOT of heat energy to overcome this tendency, break the bonds and make water warm up. Cohesion: Water has a tendency to stick to itself because it easily forms these hydrogen bonds. At any point, a large percentage of water molecules hydrogen bonding with several neighbors. We call this tendency of water to stick to itself “cohesion”. Surface Tension: Usually, each water molecule is bonded to four other water molecules most of the time, and the force is the same in all directions. However, at the surface of the water, the outer molecules have fewer adjacent water molecules to bond to. So, instead they reinforce the bonds with the molecules next to them. Because there are forces pulling the outermost molecules down and to the side, but not up, it creates a stronger layer on the surface, and a net force that pulls molecules inwards. Because water really loves to form hydrogen bonds, the top layer is reinforced, creating surface tension. Adhesion: Water also has a tendency to stick to other polar objects. We call this behavior “adhesion”. Because water really loves to form hydrogen bonds, the water adheres weakly to a waxy surface, but strongly to itself, forming a rounded water bead instead of a puddle. Capillary Action: The combination of cohesion, adhesion and surface tension creates capillary action. This is when a liquid flows through a narrow space without any external forces like gravity. In capillary action, adhesion to the walls of a vessel is stronger than the cohesion between the water molecules. The liquid sticks to the walls then pulls other molecules up behind it, then climb higher, like a rock climber. If the diameter of the tube is too big, the molecules cannot climb the walls. Instead, they go as high as they can before gravity overpowers the adhesive and cohesive forces and stops the liquid moving up. This results in a “dip” called a “meniscus”. Chapters: 0:00-0:25 Introduction 0:25-0:39 Structure 0:39-1:04 Covalent Bonds 1:04-1:32 Electronegativity 1:32-1:56 Polarity 1:56-3:05 Hydrogen Bonds 3:05-4:11 Specific Heat 4:11-4:38 Cohesion 4:38-5:24 Surface Tension 5:24-5:55 Adhesion 5:55-7:30 Capillary Action 7:30-7:47 Conclusion Sources: https://openstax.org/books/biology-2e/pages/2-2-water https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Physical_Properties_of_Matter/Atomic_and_Molecular_Properties/Dipole_Moments https://openstax.org/books/college-physics/pages/11-8-cohesion-and-adhesion-in-liquids-surface-tension-and-capillary-action Avoid plagiarism! Cite BOGObiology! Copy and Paste the Following APA Citation: [BOGObiology]. (2021, December 1). Properties of Water. [Video File]. Retrieved from https://youtu.be/qcePiG28Mkc #water #hydrogenbonds #chemistry$

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