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Simple Passive or Active? 7 form
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B1.4 Passive or Active Voice present simple PASSIVE TRANSPORT Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells. Some substances can cross the cell membrane without any input of energy by the cell in a process known as passive transport. DIFFUSION The simplest type of passive transport is diffusion. Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. This difference in the concentration of molecules across a distance is called a concentration gradient. Consider what happens when you add a sugar cube to a beaker of water. As shown in Figure 5-1, the sugar cube sinks to the bottom of the beaker. This sinking makes the concentration of sugar mole- cules greater at the bottom of the beaker than at the top. As the cube dissolves, the sugar molecules begin to diffuse slowly through the water, moving towards the lower concentration at the top. Diffusion is driven entirely by the molecules’ kinetic energy. Molecules are in constant motion because they have kinetic energy. Molecules move randomly, traveling in a straight line until they hit an object, such as another molecule. When they hit some- thing, they bounce off and move in a new direction, traveling in another straight line. If no object blocks their movement, they con- tinue on their path. Thus, molecules tend to move from areas where they are more concentrated to areas where they are less concentrated, or “down” their concentration gradient. In the absence of other influences, diffusion will eventually cause the molecules to be in equilibrium—the concentration of molecules will be the same throughout the space the molecules occupy. Returning to the example in Figure 5-1, if the beaker of water is left undisturbed, at some point the concentration of sugar molecules will be the same throughout the beaker. The sugar concentration will then be at equilibrium. SECTION 1 OBJECTIVES ● Explain how an equilibrium is established as a result of diffusion. ● Distinguish between diffusion and osmosis. ● Explain how substances cross the cell membrane through facilitated diffusion. ● Explain how ion channels assist the diffusion of ions across the cell membrane. VOCABULARY passive transport diffusion concentration gradient equilibrium osmosis hypotonic hypertonic isotonic contractile vacuole turgor pressure plasmolysis cytolysis facilitated diffusion carrier protein ion channel Sugar Water 1 2 3 FIGURE 5-1 Sugar molecules, initially in a high concentration at the bottom of a beaker, , will move about randomly through diffusion, , and eventually reach equilibrium, . At equilibrium the sugar concentration will be the same throughout the beaker. Diffusion occurs naturally because of the kinetic energy the molecules possess. 3 2 1 Copyright © by Holt, Rinehart and Winston. All rights reserved. 98 CHAPTER 5 It is important to understand that even at equilibrium the ran- dom movement of molecules continues. But because there is an equal concentration of molecules everywhere, molecules are just as likely to move in one direction as in any other. The random movements of many molecules in many directions balance one another, and equilibrium is maintained. Diffusion Across Membranes Cell membranes allow some molecules to pass through, but not others. If a molecule can pass through a cell membrane, it will diffuse from an area of higher concentration on one side of the membrane to an area of lower concentration on the other side. Diffusion across a membrane is also called simple diffusion, and only allows certain molecules to pass through the membrane. The simple diffusion of a molecule across a cell membrane depends on the size and type of molecule and on the chemical nature of the membrane. A membrane can be made, in part, of a phospho- lipid bilayer, and certain proteins can form pores in the membrane. Molecules that can dissolve in lipids may pass directly through the membrane by diffusion. For example, because of their nonpolar nature, both carbon dioxide and oxygen dissolve in lipids. Molecules that are very small but not soluble in lipids may diffuse across the membrane by moving through the pores in the membrane. 1. Yield Farming Yield Farming is like a way to "farm" rewards using your cryptocurrency. Here’s how it works: What It Is: Yield farming involves lending or staking your cryptocurrency assets in a DeFi platform to earn rewards, usually in the form of additional cryptocurrency. How It Works: You deposit your crypto into a DeFi platform, such as a liquidity pool. These platforms often use your assets to provide liquidity for other users who want to trade or borrow cryptocurrencies. In return, you earn rewards—often paid in the platform's native token. The more you contribute, the more you can earn. Why People Do It: Yield farming can provide high returns, sometimes much higher than traditional savings accounts or investments. However, it also comes with higher risks, including the volatility of cryptocurrencies and the potential for losses. 2. Staking Staking is a bit simpler and often less risky than yield farming. Here’s the breakdown: What It Is: Staking is the process of participating in the operation of a blockchain network by locking up a certain amount of cryptocurrency. How It Works: You hold (or "stake") your cryptocurrency in a blockchain network that uses a Proof of Stake (PoS) consensus mechanism. By staking your crypto, you help maintain the network's security and operations, like validating transactions. In return, you earn rewards, typically paid in the form of the same cryptocurrency you staked. Why People Do It: Staking is generally seen as a way to earn passive income with crypto. It’s often considered less risky than yield farming because you’re supporting the network rather than providing liquidity for trading. Key Differences: Complexity: Yield farming is usually more complex and involves moving assets across different platforms, whereas staking is typically more straightforward. Risk: Yield farming can be riskier due to market fluctuations, smart contract vulnerabilities, and the complexity of the strategies involved. Staking tends to be less risky but still carries the risk associated with the cryptocurrency itself. Rewards: Yield farming often offers higher potential returns but with greater risk. Staking usually provides more stable and predictable rewards. Summary: Yield Farming: Earn rewards by lending or staking your crypto in liquidity pools. Higher potential rewards, higher risk. Staking: Earn rewards by locking up your crypto to support a blockchain network. More straightforward, generally lower risk. Both methods offer ways to grow your crypto holdings, but it’s important to understand the risks and do your own research before getting involvedSimple passive voice present simple passivePast simple passive voicePresent simple passive and past simple passivePast Simple Passive