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What distinguishes primary active transport from other forms of active transport?
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Primary active transport moves solutes against their gradient and consumes ATP.
How does passive transport differ from active transport in terms of energy requirement?
Passive transport requires no energy (ATP), whereas active transport requires energy.
How do phospholipids arrange themselves in the cell membrane, and why?
Phospholipids form a bilayer with hydrophobic tails inward and hydrophilic heads outward to avoid water.
What role do cholesterol molecules play in the cell membrane?
Cholesterol molecules stiffen the membrane and act as a glue without making it rigid.
What factors affect the rate of diffusion across the cell membrane?
Temperature, molecular weight, concentration gradient steepness, surface area, and permeability.
Distinguish between integral and peripheral proteins in the cell membrane.
Integral proteins penetrate the membrane and are transmembrane, while peripheral proteins adhere to one side of the membrane.
Explain the role of gated channel proteins in the cell membrane.
Gated channels open or close in response to ligands, voltage, or mechanical stress, allowing passage of substances.
What portion of the cell membrane is composed of lipids, and what specific type of lipid predominates?
98% of the cell membrane is composed of lipids, with 75% being phospholipids.
Describe the differences between hypotonic, hypertonic, and isotonic solutions in relation to cell volume.
Hypotonic solutions cause cells to swell, hypertonic cause cells to shrink, and isotonic result in no net volume change.
Discuss the role of carrier proteins in transport across the cell membrane.
Carrier proteins assist in moving solutes across the membrane, often against a concentration gradient in active transport.
What is the purpose of transcytosis in cellular activity?
Transcytosis moves substances across a cell, combining endocytosis and exocytosis functions.
Define osmosis and describe the structure that aids its process in cells.
Osmosis is the diffusion of water across a membrane, facilitated by aquaporins.
What is the significance of glycoproteins in cell membrane structures?
Glycoproteins function as cell identity markers, tagging cells for recognition.
Why is the cell membrane considered selectively permeable?
It regulates which substances can pass through, maintaining internal equilibrium while communicating with the external environment.
Explain the process and purpose of endocytosis in cells.
Endocytosis is the process of cellular uptake of materials, via engulfing solids (phagocytosis), liquids (pinocytosis), or specific substances (receptor-mediated).
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