38 Questions
What is the primary function of membrane receptors?
To bind to specific extracellular molecules and cause a corresponding cellular response
What is the typical composition of membrane-spanning components of membrane receptors?
Alpha helices
What is the function of ligands in cellular signaling?
To bind to receptors to produce an intercellular signal
What is the purpose of channels in cellular membranes?
To facilitate the passage of molecules through the membrane that wouldn't be able to otherwise
What is the composition of channels in cellular membranes?
Beta barrels
What is the function of the cytosol in cellular structure?
To suspend organelles in the cell
What type of amino acids would be present in the intramembranous domains of membrane receptors?
Hydrophobic/nonpolar amino acids
What type of amino acids would be present in the intra- and extracellular domains of membrane receptors?
Polar/charged amino acids
What is the unit of osmotic pressure?
atm
Which of the following increases the osmotic pressure of a solution?
Increasing the molarity of the solution
What is the role of van't Hoff factor in osmotic pressure?
It represents the number of ions formed by the solute
What is the primary purpose of the plasma membrane in a cell?
To separate the external and internal environments of the cell, allowing for homeostasis
What is the characteristic of phospholipids that allows them to form a lipid bilayer?
Their amphipathic nature, with a charged phosphate head and hydrocarbon tails
In which direction will water flow when a cell with a higher osmotic pressure is placed in a solution with a lower osmotic pressure?
Into the cell
What is the purpose of facilitated diffusion in a cell?
To allow polar molecules or charged ions to cross the plasma membrane
What is the function of cholesterol in the plasma membrane of eukaryotic cells?
To maintain consistency in membrane performance in a wide range of temperatures
What is the term for areas in the plasma membrane with high concentrations of cholesterol?
Lipid rafts
What is the driving force behind spontaneous movement of molecules?
The concentration gradient
What is the main difference between peripheral and integral proteins in the plasma membrane?
Their location in the membrane, with peripheral proteins attaching to one side and integral proteins spanning the entire membrane
Which of the following is an example of facilitated diffusion?
Passage of glucose across the plasma membrane
What will happen to a cell placed in a hypertonic solution?
Water will flow out of the cell
What is the term for proteins that span the entire plasma membrane and have both extracellular and intracellular domains?
Transmembrane proteins
Why do prokaryotes not use cholesterol in their plasma membrane?
Because they use hopanoids instead, which provide similar functionality
What is the term for the smallest unit of self-sustainable life?
Cell
What is the result of the hydrolysis of ATP?
ADP + Pi + H2O
What is the primary source of energy for biological reactions?
ATP
What is the function of Na+/K+ ATPase?
To pump 3 Na+ ions out and 2 K+ ions into the cell
What is the purpose of secondary active transport?
To utilize the gradient established by active transport
What type of amino acids would be present in the core of a Ca2+ channel?
Negatively charged or dipole amino acids
What is the process of releasing cellular contents into the extracellular environment?
Exocytosis
What is the energy yield of ATP hydrolysis?
-30 kJ/mol
What is the purpose of active transport?
To use ATP to pump ions against their gradient
What is the primary function of endocytosis in a cell?
To release extracellular molecules into the cell
What type of transport is exocytosis and endocytosis an example of?
Active transport
What is the name of the protein used to create vesicles in exocytosis and endocytosis?
Clathrin
What is the main difference between symport and antiport transportation?
The direction of molecule movement
What is the purpose of symport and antiport transportation?
To move molecules against their concentration gradient
What is the term for vesicles produced in exocytosis?
Exosomes
Study Notes
The Cell
- The cell is the smallest unit of self-sustainable life.
Plasma Membrane
- Composed of a lipid bilayer, separating external and internal environments to maintain homeostasis.
- Phospholipids have an amphipathic nature, with a charged phosphate head and hydrocarbon tails.
- Cholesterol is used by eukaryotes to maintain consistency in membrane performance at various temperatures.
- Lipid rafts are areas in the membrane with high concentrations of cholesterol, surrounding proteins or other membrane components.
Proteins
- Peripheral proteins attach to one side of the membrane, either externally or internally.
- Integral proteins, also called transmembrane proteins, span the entire membrane with both extracellular and intracellular domains.
- Membrane receptors are integral proteins that bind to specific extracellular molecules, causing a corresponding cellular response.
- Channels allow for the passage of molecules through the membrane, composed of beta barrels, and each type allows passage of a different substance.
Cytoplasm
- The entire interior of the cell, including organelles and cytosol.
- Cytosol is the gel-like portion suspending organelles, composed of water, ions, proteins, etc.
Osmotic Pressure
- The pressure needed to prevent the inward flow of water from a pure solution across a semipermeable membrane.
- Described by the equation: π = iMRT, where π is the osmotic pressure, i is van't Hoff's factor, M is the molarity of the solution, R is the ideal gas law constant, and T is the temperature in Kelvin.
Facilitated Diffusion
- Passage of polar molecules or charged ions through a protein channel or carrier.
- Molecules move from areas of high concentration (or charge) to areas of low concentration (or charge), down an electrochemical gradient.
Active Transport
- Energy is used to move solutes against their electrochemical gradient.
- ATP is the primary source of energy for biological reactions, produced by the cell.
- Na+/K+ ATPase pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell, against their chemical gradients.
Exocytosis and Endocytosis
- Exocytosis: Cellular contents are packaged in a vesicle and released into the extracellular environment.
- Endocytosis: A vesicle containing extracellular molecules fuses with the plasma membrane and releases its contents into the cell.
Symport and Antiport
- Both utilize the movement of one molecule with its gradient to transport another molecule against its respective gradient.
- Symporters move both molecules in the same direction, while antiporters move them in opposite directions.
Learn about the components of a cell and their roles in making life possible. This quiz covers the plasma membrane, its purpose, and how it maintains homeostasis.
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