Campbell Biology ch 7 Membrane Structure and Function

Hydrophobic reactions primarily hold the plasma membrane together.

Phospholipids can rapidly change position, switching places up to $10^7$ times per second.

Cholesterol decreases fluidity at human body temperature while preventing phospholipids from packing closely together.

<p>Membranes stay fluid at low temperatures if rich in unsaturated hydrocarbon tails, while cold temperatures can solidify membranes.</p> Signup and view all the answers

<p>Integral proteins penetrate the hydrophobic layer, while peripheral proteins are loosely bound to the surface.</p> Signup and view all the answers

<p>Fish in cold environments have more unsaturated tails to keep their membranes fluid despite low temperatures.</p> Signup and view all the answers

<p>Membrane proteins determine the functions of the membrane, providing various roles like transport and signaling.</p> Signup and view all the answers

<p>Certain individuals have genes coding for CCR5, a co-receptor HIV must bind to, offering resistance to infection.</p> Signup and view all the answers

<p>They include unusual lipids in their membranes to prevent excessive fluidity in extreme heat.</p> Signup and view all the answers

<p>Winter wheat increases its unsaturated phospholipids in autumn to adapt to colder winter temperatures.</p> Signup and view all the answers

<p>Amphipathic molecules have both hydrophilic and hydrophobic regions, which allows them to form the bilayer structure of cell membranes.</p> Signup and view all the answers

<p>The Fluid Mosaic Model depicts the plasma membrane as a fluid structure with proteins embedded in it, allowing for movement and various functions.</p> Signup and view all the answers

<p>Lipid rafts are patches within the plasma membrane enriched with specific lipids and proteins that facilitate particular cellular functions.</p> Signup and view all the answers

<p>Cholesterol reduces fluidity at human body temperature by restraining phospholipid movement while preventing solidification at lower temperatures.</p> Signup and view all the answers

<p>Phospholipids can rapidly change positions, swapping places with adjacent phospholipids up to $10^7$ times per second.</p> Signup and view all the answers

<p>Unsaturated hydrocarbon tails prevent tight packing of lipids, allowing the membrane to remain fluid even at lower temperatures.</p> Signup and view all the answers

<p>Membrane proteins attached to the cytoskeleton are typically immobile, limiting their movement within the membrane.</p> Signup and view all the answers

<p>Weaker hydrophobic interactions allow for flexibility and fluidity in the membrane structure, essential for cellular functions.</p> Signup and view all the answers

<p>Cholesterol helps maintain membrane fluidity by preventing it from becoming too rigid in cold temperatures and too fluid in warm temperatures.</p> Signup and view all the answers

<p>Unsaturated hydrocarbon tails keep membranes fluid in cold temperatures by preventing solidification due to double bonds.</p> Signup and view all the answers

<p>Integral proteins penetrate the hydrophobic layer of membranes and often span the entire membrane, facilitating various functions.</p> Signup and view all the answers

<p>Peripheral proteins are loosely bound to the membrane surface and are not embedded, unlike integral proteins that penetrate the membrane.</p> Signup and view all the answers

<p>Carbohydrates on the extracellular surface facilitate cell recognition by binding to molecules, often forming glycoproteins and glycolipids.</p> Signup and view all the answers

<p>Glycoproteins vary in structure and composition among different blood types, affecting blood type compatibility in transfusions.</p> Signup and view all the answers

<p>The Fluid Mosaic Model depicts membranes as fluid structures with various proteins embedded, allowing for flexibility and movement.</p> Signup and view all the answers

<p>Amphipathic refers to phospholipids having both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts.</p> Signup and view all the answers

<p>Lipid rafts are patches within the membrane that contain concentrated lipids and proteins associated with specific functions.</p> Signup and view all the answers

<p>The binding of HIV to CD4 and the co-receptor CCR5 demonstrates how specific proteins on cell membranes can facilitate viral entry.</p> Signup and view all the answers

<p>The absence of CCR5 allows patients to be resistant to HIV by preventing the virus from entering their cells.</p> Signup and view all the answers

<p>Glycolipids are carbohydrates covalently bonded to lipids, while glycoproteins are carbohydrates bonded to proteins.</p> Signup and view all the answers

<p>Selective permeability limits the movement of hydrophilic molecules, making it harder for them to pass through the hydrophobic lipid bilayer.</p> Signup and view all the answers

<p>Aquaporins are channel proteins that facilitate the rapid movement of water molecules across the cell membrane.</p> Signup and view all the answers

<p>Passive transport is the movement of substances across a membrane without the use of energy, such as the diffusion of oxygen into cells.</p> Signup and view all the answers

<p>A concentration gradient is a difference in the concentration of a substance across a space, driving the movement from high to low concentration.</p> Signup and view all the answers

<p>Osmosis occurs when water molecules pass through a semi-permeable membrane, moving towards areas of higher solute concentration.</p> Signup and view all the answers

<p>Nonpolar molecules can easily pass through the cell membrane because they dissolve in the hydrophobic lipid bilayer.</p> Signup and view all the answers

<p>Carrier proteins are specific because they bind to particular molecules, changing shape to transport them across the membrane.</p> Signup and view all the answers

<p>Glycoproteins determine blood type by varying in structure between individuals, which impacts blood compatibility.</p> Signup and view all the answers

<p>Hydration shells make it difficult for polar ions to penetrate the lipid bilayer, as the water molecules surrounding them hinder their movement.</p> Signup and view all the answers

<p>Glucose transport proteins facilitate the rapid transport of glucose by binding to it and then changing shape to move it across the membrane.</p> Signup and view all the answers

<p>Thermal energy causes particles to move randomly, driving the process of diffusion until equilibrium is reached.</p> Signup and view all the answers

<p>Osmosis is the diffusion of free water across a selectively permeable membrane, occurring from a higher concentration of free water to a lower concentration, until equilibrium is reached.</p> Signup and view all the answers

<p>Tonicity is the ability of a solution to cause a cell to gain or lose water, significantly affecting the cell's shape and function depending on solute concentration.</p> Signup and view all the answers

<p>In a hypertonic environment, a cell loses water, causing it to shrivel and potentially die due to the high concentration of non-penetrating solutes outside the cell.</p> Signup and view all the answers

<p>Isotonic refers to an environment where the solute concentration is equal inside and outside the cell, resulting in no net movement of water and a stable cell volume.</p> Signup and view all the answers

<p>Aquaporins are specialized transport proteins that facilitate the rapid diffusion of water across cell membranes, essential for maintaining water balance in cells.</p> Signup and view all the answers

<p>Plasmolysis occurs when plant cells lose water to a hypertonic environment, causing the plasma membrane to pull away from the cell wall, leading to cell shrinkage.</p> Signup and view all the answers

<p>Osmoregulation involves the adaptations organisms make to deal with osmotic pressure changes, such as maintaining solute concentrations and water balance despite external conditions.</p> Signup and view all the answers

<p>Gated ion channels open and close in response to stimuli, allowing specific ions to flow across the membrane, which is vital for processes like nerve signal transmission.</p> Signup and view all the answers

<p>Passive transport occurs without energy input as substances move down their concentration gradient, while active transport requires energy to move substances against their gradient.</p> Signup and view all the answers

<p>In a hypotonic solution, water enters both animal and plant cells, which may cause animal cells to burst while plant cells become turgid, a healthy state.</p> Signup and view all the answers

<p>Diffusion allows oxygen to move into cells and carbon dioxide to exit, facilitating the process of cellular respiration by maintaining the necessary gas concentrations.</p> Signup and view all the answers

<p>The concentration gradient represents potential energy that drives passive transport, allowing substances to diffuse from areas of high concentration to low concentration without energy expenditure.</p> Signup and view all the answers

<p>Contractile vacuoles in protists like paramecium pump out excess water that enters the cell through osmosis, helping to maintain osmotic balance.</p> Signup and view all the answers

<p>Osmosis is the diffusion of free water across a selectively permeable membrane, while diffusion refers to the movement of solutes from higher to lower concentration without involving a membrane.</p> Signup and view all the answers

<p>Tonicity refers to the ability of a surrounding solution to cause a cell to gain or lose water, critically influencing whether a cell swells, shrinks, or remains stable.</p> Signup and view all the answers

<p>In a hypertonic solution, a cell will lose water, causing it to shrivel and potentially die.</p> Signup and view all the answers

<p>Plasmolysis occurs when water leaves a plant cell in a hypertonic environment, causing the plasma membrane to pull away from the cell wall.</p> Signup and view all the answers

<p>Aquaporins are specialized proteins that facilitate the rapid diffusion of water across cell membranes.</p> Signup and view all the answers

<p>Facilitated diffusion occurs passively and relies on concentration gradients, whereas active transport requires energy to move substances against their concentration gradients.</p> Signup and view all the answers

<p>The sodium-potassium pump is essential for maintaining high potassium (K+) and low sodium (Na+) concentrations inside animal cells, crucial for cellular function.</p> Signup and view all the answers

<p>Turgor pressure is the pressure exerted by water inside the plant cell against the cell wall, which helps maintain the cell's shape and structural integrity.</p> Signup and view all the answers

<p>In a hypotonic solution, cells without walls can swell rapidly and possibly burst due to excess water intake.</p> Signup and view all the answers

<p>A gated channel opens or closes in response to a specific stimulus, such as a voltage change or the binding of a chemical signal.</p> Signup and view all the answers

<p>In an isotonic environment, there is no net movement of water, and the plant cell remains flaccid.</p> Signup and view all the answers

<p>Unicellular organisms, like paramecium, have a contractile vacuole that helps pump excess water out of the cell to maintain homeostasis.</p> Signup and view all the answers

<p>Organisms without cell walls, such as animals, actively regulate water and solute levels, while those with cell walls, like plants, mainly rely on cell walls for structural support during osmotic changes.</p> Signup and view all the answers

<p>Facilitated diffusion relies on concentration gradients to allow materials to move passively through specific channels or transport proteins.</p> Signup and view all the answers

<p>The proton pump transports hydrogen ions (H+) outside the cell, generating voltage and storing energy for cellular functions.</p> Signup and view all the answers

<p>Cotransport proteins allow H+ ions to enter the cell only when combined with a sucrose molecule, utilizing the H+ gradient created by proton pumps.</p> Signup and view all the answers

<p>Exocytosis is the process where a cell secretes molecules by fusing vesicles with the plasma membrane, releasing their contents outside the cell.</p> Signup and view all the answers

<p>Receptor-mediated endocytosis involves specific receptors on the plasma membrane binding to solutes, clustering in coated pits, and forming vesicles to bring substances into the cell.</p> Signup and view all the answers

<p>Phagocytosis involves the engulfing of large particles by the cell, while pinocytosis is the process of taking in extracellular fluid in small vesicles.</p> Signup and view all the answers

<p>Sodium-glucose cotransport allows for the absorption of sodium and glucose in the intestines, which helps replenish lost electrolytes during diarrhea.</p> Signup and view all the answers

<p>Vesicles from the Golgi apparatus transport molecules to the plasma membrane for secretion or integration into the membrane during exocytosis.</p> Signup and view all the answers

<p>Cells commonly take up large molecules, like proteins and polysaccharides, and various nutrients through endocytosis.</p> Signup and view all the answers

<p>LDL particles transport cholesterol to cells, where they bind to LDL receptors and are taken up via receptor-mediated endocytosis.</p> Signup and view all the answers

<p>Coated pits are specialized regions of the plasma membrane lined with coat proteins that form vesicles during pinocytosis to engulf extracellular fluid.</p> Signup and view all the answers

<p>The potassium-sodium pump creates a net negative charge inside the cell by moving 3 sodium ions out while bringing 2 potassium ions in, maintaining the membrane potential.</p> Signup and view all the answers

<p>After the vesicle is formed and the substances are taken in, the receptors are recycled back to the plasma membrane for further use.</p> Signup and view all the answers

<p>The proton pump establishes a proton gradient across the membrane, which can be used to drive various cellular processes requiring energy.</p> Signup and view all the answers

<p>Endocytosis involves the formation of vesicles to take in substances, while exocytosis entails the fusion of vesicles with the membrane to release contents outside the cell.</p> Signup and view all the answers

<p>ATP provides the energy necessary for the sodium-potassium pump to transport Na+ out of the cell and K+ into the cell by transferring a phosphate group to the pump, causing it to change shape.</p> Signup and view all the answers

<p>Membrane potential is the voltage across a cell's plasma membrane, typically ranging from -50 to -200 millivolts, with the inside of the cell being more negative relative to the outside.</p> Signup and view all the answers

<p>The electrochemical gradient combines chemical forces (concentration differences) and electrical forces (charge differences), influencing ions to move down their gradient, not just their concentration gradient.</p> Signup and view all the answers

<p>The sodium-potassium pump is electrogenic because it exports more positively charged Na+ ions than it imports K+ ions, creating a net negative charge inside the cell.</p> Signup and view all the answers

<p>Proton pumps transport hydrogen ions (H+) out of the cell, generating a voltage across membranes that facilitates energy storage for cellular functions.</p> Signup and view all the answers

<p>Cotransporters utilize the gradient of one ion (like H+ or Na+) to facilitate the transport of another solute (like sucrose or glucose) across the plasma membrane.</p> Signup and view all the answers

<p>The unequal distribution of charged ions, particularly the higher concentration of K+ inside the cell relative to Na+ outside, creates a negative charge on the cytoplasmic side of the plasma membrane.</p> Signup and view all the answers

<p>Facilitated diffusion allows substances to cross membranes passively via protein channels, enhancing the efficiency of transport without needing energy.</p> Signup and view all the answers

<p>Carrier proteins are essential for active transport because they can change shape to move substances against their concentration gradient, a process that requires energy.</p> Signup and view all the answers

<p>During diarrhea, rapid expulsion of waste prevents the reabsorption of sodium, potentially leading to dangerously low sodium levels in the body.</p> Signup and view all the answers

<p>When a nerve cell is stimulated, protein channels open, allowing sodium ions (Na+) to rapidly enter the cell, driven both by the concentration gradient and electrical forces.</p> Signup and view all the answers

<p>Sodium-potassium pumps help maintain the resting membrane potential by constantly exchanging Na+ for K+ across the plasma membrane, preserving the negative internal charge.</p> Signup and view all the answers

<p>A primary characteristic of facilitated diffusion is that it does not require energy, whereas active transport relies on ATP to move substances against their concentration gradient.</p> Signup and view all the answers

<p>Carrier membrane proteins regulate the entry and exit of ions, directly influencing the ion distribution that establishes the membrane potential.</p> Signup and view all the answers