Cell Transport and Surface Area Practice Quiz (31 questions)

Explanation

A cell is the smallest structural and functional unit of life capable of carrying out all processes necessary for life. A specialized structure describes an organelle, a group of similar structures is larger than a cell, and a one-process structure does not meet the definition.

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Living cells are open systems because they exchange both matter and energy with their surroundings. A closed system exchanges energy but not matter, and an isolated system exchanges neither.

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The nuclear envelope surrounds the nucleus and controls movement through nuclear pores. The nucleus contains DNA and regulates many cell activities, while ribosomes build proteins and the Golgi modifies, sorts, and packages materials.

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Rough ER has ribosomes and helps process proteins for transport or membranes, including folding and initial processing. Smooth ER lacks ribosomes and makes lipids, free ribosomes build proteins, and the Golgi modifies, sorts, and packages them.

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The Golgi apparatus modifies, sorts, and packages proteins and lipids. Rough ER processes proteins, smooth ER makes lipids, and ribosomes build proteins.

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After the Golgi modifies, sorts, and packages the protein, a secretory vesicle carries it to the cell membrane, where fusion releases it by exocytosis. Transport vesicles bring proteins to the Golgi, while ribosomes and the rough ER act earlier in the pathway.

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CHON stands for carbon, hydrogen, oxygen, and nitrogen. Phosphorus and sulfur are also important in living things, but they do not replace oxygen or nitrogen in this four-element set.

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Carbohydrates include simple sugars such as glucose and structural molecules such as cellulose. Lipids are associated with long-term energy storage and membranes; proteins are built from amino acids; nucleic acids are built from nucleotides.

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Lipids often include glycerol and fatty acids and function in long-term energy storage and membranes. Carbohydrates are associated with energy and some structural support, while proteins and nucleic acids have different building blocks and primary roles.

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Proteins are built from amino acids and include enzymes, antibodies, and hemoglobin. Carbohydrates are built from simple sugars, lipids often include glycerol and fatty acids, and nucleic acids are built from nucleotides.

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Selective permeability means that some substances pass through a membrane more easily than others, helping maintain homeostasis. The fluid mosaic model describes membrane organization and movement, while the bilayer is its main structural arrangement.

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A phospholipid bilayer consists of two phospholipid layers, and each phospholipid has a phosphate-containing head and two hydrophobic fatty acid tails. The fluid mosaic model describes the flexible arrangement of the bilayer and its components.

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Hydrophilic phosphate-containing heads interact favourably with water, so they face the fluids inside and outside the cell; hydrophobic tails point inward, away from water. Reversing or aligning both parts in the same direction ignores their different interactions with water.

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Large polar molecules such as glucose generally need transport proteins, whereas small nonpolar molecules such as oxygen usually cross directly through the phospholipid bilayer. The other routes reverse or erase this distinction.

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Apoptosis is controlled programmed cell death that helps development and removes unnecessary cells. Necrosis refers to cell death caused by damage or injury; mitosis is cell division, and inflammation is a tissue response.

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Particle theory states that particles of a pure substance share identical basic properties and that heating usually makes particles move faster. Heating does not change their identity, eliminate attraction, or make their movement slower.

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Active transport requires energy directly or indirectly and often moves substances against a gradient. Passive transport moves down a gradient without direct ATP expenditure; simple diffusion and osmosis are passive, and facilitated diffusion also moves down a gradient.

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Movement down a concentration gradient is from higher to lower concentration, so the substance moves from outside to inside. Movement from inside to outside would be against the stated gradient, and equilibrium with no net movement is not specified.

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Simple diffusion is net movement of particles from higher to lower concentration due to random motion, and direct passage through the bilayer requires no membrane protein or direct ATP. Osmosis concerns water, facilitated diffusion uses a protein, and active transport requires energy.

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Facilitated diffusion moves a substance down its gradient through a membrane protein without direct ATP expenditure. Simple diffusion passes directly through the bilayer, osmosis is water movement, and active transport requires energy.

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Equal effective solute concentrations produce no net water movement, so an animal cell stays about the same size. Swelling and bursting reflect water entering in a hypotonic solution, while shrinking reflects water leaving in a hypertonic solution.

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A higher external effective solute concentration makes the solution hypertonic, so water leaves the plant cell and plasmolysis may occur. Water gain and firmness describe a hypotonic response; no net movement describes an isotonic response.

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A lower external effective solute concentration is hypotonic, so water moves into the plant cell and makes it turgid and firm. Water loss and shrinking indicate a hypertonic response, while bursting is a possible animal-cell outcome.

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Plasmolysis is the shrinking of a plant cell’s membrane and cytoplasm away from the cell wall after water loss. Turgor pressure and turgidity involve water entering and firming the cell, while hypertonicity names a surrounding solution condition.

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A protein pump uses energy to move specific substances across a membrane, often against a concentration or electrochemical gradient. Channels support movement down a gradient, while endocytosis and exocytosis move material using vesicles.

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The sodium-potassium pump uses ATP to move sodium ions out of many animal cells and potassium ions into them. Reversing these directions, moving both ions the same way, or replacing potassium with another ion does not describe this pump.

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Endocytosis brings material into a cell by membrane enclosure and inward folding to form an energy-requiring vesicle. Exocytosis releases vesicle contents outside; protein pumps and facilitated diffusion do not form such vesicles.

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Exocytosis releases material outside a cell when a vesicle fuses with the cell membrane. Endocytosis brings material inward, while pumps and facilitated diffusion move substances across membranes without vesicle fusion.

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The surface area is $2(5\times3)+2(5\times2)+2(3\times2)=30+20+12=62$ cm². The value 30 cm² comes from multiplying the dimensions, 31 cm² omits the factor of 2, and 52 cm² miscalculates the face areas.

Explanation

Volume is the product of the three dimensions: $8\times4\times3=96$ mm³. The value 15 mm³ comes from adding the dimensions, 136 mm³ is the surface area, and 32 mm³ omits the height.

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The ratio is calculated by dividing surface area by volume: $72\div24=3$, so SA:V is 3:1. The ratio 1:3 inverts the division, while 2:1 and 4:1 result from using subtraction or addition rather than the specified quotient.