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Questions and Answers
Which process involves the movement of more than one substance at a time, with substances being moved in the same direction?
What type of transport across membranes involves the ejection of substances 'out of the cell'?
Which example best illustrates 'cell drinking'?
The concentration of specific substances that bind to receptor proteins is a characteristic of which type of endocytosis?
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In which process are large or solid materials engulfed by cells?
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What type of transport moves fluid and large particles across membranes in vesicles?
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What is the function of the cell membrane in regards to transport?
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Why does passive transport not require ATP energy?
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What is the term used to describe the fluid outside of cells that contains nutrients like amino acids and sugars?
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When does diffusion occur?
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What is the primary difference between facilitated diffusion and simple diffusion?
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What is the significance of a concentration gradient in the context of membrane transport?
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Which process involves the diffusion of H2O from high to low concentration?
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Which type of proteins form passageways through the plasma membrane for specific ions or molecules?
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What is the main difference between isotonic and hypertonic solutions?
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Which type of transport requires energy and moves molecules against the concentration gradient?
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What do carrier proteins do to assist in the transport of molecules across the membrane?
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In which type of transport does ATP directly drive the process?
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Study Notes
Cell Structure
- A cell has three basic parts: the plasma membrane, the cytoplasm, and the genetic material (DNA or RNA)
- The plasma membrane regulates what enters and leaves the cell
- The cytoplasm is the jelly-like substance inside the cell where metabolic reactions occur
- The genetic material contains the cell's instructions for growth, reproduction, and response to stimuli
Phospholipids in a Watery Environment
- Phospholipids organize into a bilayer in a watery environment due to their hydrophobic tails and hydrophilic heads
- The tails face inward, away from water, and the heads face outward, interacting with water
Membrane Transport
- Membrane transport refers to the movement of substances (solutes, ions, and water) in and out of the cell
- Two factors involved: permeability and size of solutes or substances
- Interstitial fluid is the fluid outside cells, rich in nutrients, sugars, fatty acids, vitamins, hormones, salts, and wastes
Selective Permeability
- The plasma membrane allows only certain substances to enter the cell
- Nutrients enter, and wastes leave the cell through passive or active transport mechanisms
Passive Transport
- No energy (ATP) is needed
- Molecules move down their concentration gradient from high to low concentration
- Types of passive transport: diffusion, osmosis, and facilitated diffusion
Concentration Gradient
- A concentration gradient exists when the solute concentration in a solvent is greater at one point than at another
- The concentration gradient is calculated as the concentration difference between two points divided by the distance between them
Diffusion
- The movement of solutes from an area of higher concentration to an area of lower concentration
- Example: a salt crystal placed in a beaker of water, where salt ions move into the water, eventually reaching equilibrium
Facilitated Diffusion
- Transport proteins (carrier or channel proteins) assist molecules across the membrane
- Examples: glucose, amino acids, H2O, and ions
- Channel proteins form passageways through the plasma membrane, allowing specific ions or molecules to enter or exit the cell
- Carrier proteins bind to molecules, change shape, and ferry them across the membrane
Osmosis
- Refers to the diffusion of water from high to low concentration
- Aquaporins are channel proteins for water passage
- Tonicity refers to the ability of a solution to change the shape or tone of cells by changing water volume
Active Transport
- Energy (ATP) is needed to move molecules against their concentration gradient from low to high concentration
- Types of active transport: primary and secondary active transport
Primary Active Transport
- Directly uses ATP to drive transport
- Examples: Ca2+ pump, H+ pump, and Na+-K+ pump
- The sodium-potassium pump is an example of primary active transport
Secondary Active Transport
- Moves more than one substance at a time
- Types: symport (2 substances moved in the same direction) and antiport (2 substances moved in opposite directions)
- Examples: cotransport of sugars, amino acids, and ions
Vesicular Transport
- Fluid and large particles are transported across membranes in vesicles (sacs)
- Types: exocytosis (eject substances out of the cell) and endocytosis (ingest substances into the cell)
Endocytosis
- Types: phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis
- Examples: white blood cells engulfing bacteria, intestinal cells ingesting fluid with dissolved molecules, and concentration of specific substances (ligands) that bind to receptor proteins
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Description
Test your knowledge on the functions of basic parts of a cell, reasons for phospholipid bilayer organization, and mechanisms of membrane transport for substances in and out of the cell.
