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| Questão | Responda |
| What are the functions of the cell membrane? | 1. protection, 2. controls access, 3. communication, 4.shape |
| How does the cell membrane protect the cell | It protects the biochemical organization from the conditions in the external environment that would change or destroy that organization |
| How does the cell membrane control access | 1. Its porous phospholipid bilayer “provide(s)… for the controlled exchange of materials between the external environment and the cell” by allowing “small molecules such as minerals, amino acids, and sugars” to pass while “ the majority of the soluble molecules such as salt, amino acids, and sugars cannot.” 2. cell membranes have transport proteins, such as channel proteins and carrier proteins and carrier proteins that regulate the flow of most water soluble molecules through the cellular membrane” 3. receptor proteins which “act as gatekeepers for the channel proteins.” |
| What role does the cell membrane play in communication? | it identifies cells as well as the and moving and exchanging of the substances between the external environment and the cytoplasm |
| How does the cell membrane affect the shape of the cell? | it plays a role in anchoring the cytoskeleton to provide shape to the cell |
| Where is the cell wall? | it is a strong supporting layer found outside and around the membrane |
| What is the cell wall made of? | The material in the cell wall varies between species. In the primary (growing) plant cell wall, the major carbohydrates are cellulose, hemicellulose and pectin. |
| How does the cell wall affect the shape of the cell? | The wall gives cells rigidity and strength, offering protection against mechanical stress. In multicellular organisms, it permits the organism to build and hold its shape |
| Which organisms have cell walls? | They are limited to mostly plant cells |
| What is the Fluid Mosaic Model of the cell membrane? | Because cells reside in a watery solution (extracellular fluid), and they contain a watery solution inside of them (cytoplasm), the plasma membrane forms a circle around each cell so that the water-loving heads are in contact with the fluid, and the water-fearing tails are protected on the inside.Proteins and substances such as cholesterol become embedded in the bilayer, giving the membrane the look of a mosaic. Because the plasma membrane has the consistency of vegetable oil at body temperature, the proteins and other substances are able to move across it. That’s why the plasma membrane is described using the fluid-mosaic mod |
| draw a model of the fluid mosaic model of the cell membrane | draw picture |
| What are the two ways in which proteins are attached or embedded in the cell membrane | 1. Chemical reactions 2. anchored |
| What is the difference between proteins being attached by chemical reactions vs. being anchored to the cell membrane? | 1. Some proteins are held into the phospholipid bilayer by chemical reactions between the amino acids of which they are composed and the tails of the phospholipids 2. others are anchored in place by a network of protein strands connected to the cytolskelton |
| What are the different types of proteins found on the cell membrane? | 1. transport 2. receptor 3. recognition |
| What do transport proteins do on the cell membrane? | Transport proteins regulate the flow of most water soluble molecules through the cellular membrane. There are two types: 1. channel proteins form channels or pores that allow water soluble molecules to penetrate the membrane 2. carrier proteins have binding sites and carry the molecule across the cellular membrane by changing shape or other means |
| How do receptor proteins work on the cell membrane? | 1. they trigger cellular responses (e.g., increase in metabolic rate, cell division, secretion of hormones) in the extracellular fluid 2. they act as a gatekeeper for channel proteins |
| What is the function of recognition proteins in the cell membrane? | they serve as identification tags and attachments sites for other molecules |
| What are the different types of passage across the cell membrane? | 1. diffusion 2. osmosis |
| How does diffusion across the cell membrane work? | The movement of molecules from areas of high concentration to low concentration which results in the equal distribution of molecules throughout the fluid if the process is allowed to go to its natural conclusion. It can be either active or passive. |
| What is the difference between active and passive diffusion across the cell membrane? | It is referred to as passive transport if it requires no energy from the cell in order to carry the substance across the membrane. |
| How does osmosis work? | It is the diffusion of water through selectively permeable membrane. Since water can pass in both directions and the other molecules cannot, there is a net movement of water from the area of high concentration (hypertonic) to the area of low concentration (hypotonic) until equilibrium is reached (isotonic). |
| What is the difference between diffusion and osmosis? | Diffusion and osmosis are related concepts—both involve the movement of materials from a highly concentrated area to areas of low concentration. Diffusion refers to the movement of any chemical from one place to another, whereas osmosis exclusively refers to the movement of water across a membrane. Osmosis occurs across a semi-permeable cell membrane in plant and animal cells. For example, a plant absorbs water from surrounding soil via its root system—the surrounding soil has a higher concentration of water than the cell adjacent to the soil, therefore, the water moves from the highly concentrated soil into the cell, which is a place of lower concentration. The process will continue until both sides reach equilibrium, at which point osmosis is no longer necessary. |
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