Biology: Cell Structure and Function

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Questions and Answers

What is the primary function of membrane receptors?

To provide structure to the cell membrane

To synthesize proteins

To bind to specific extracellular molecules and cause a corresponding cellular response (correct)

To facilitate the passage of molecules through the membrane

What is the typical composition of membrane-spanning components of membrane receptors?

Alpha helices (correct)

Cytoplasmic organelles

Beta sheets

Beta barrels

What is the function of ligands in cellular signaling?

To provide structure to the cell membrane

To facilitate the passage of molecules through the membrane

To bind to receptors to produce an intercellular signal (correct)

To synthesize proteins

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 Signup and view all the answers

What is the composition of channels in cellular membranes?

Beta barrels Signup and view all the answers

What is the function of the cytosol in cellular structure?

To suspend organelles in the cell Signup and view all the answers

What type of amino acids would be present in the intramembranous domains of membrane receptors?

Hydrophobic/nonpolar amino acids Signup and view all the answers

What type of amino acids would be present in the intra- and extracellular domains of membrane receptors?

Polar/charged amino acids Signup and view all the answers

What is the unit of osmotic pressure?

atm Signup and view all the answers

Which of the following increases the osmotic pressure of a solution?

Increasing the molarity of the solution Signup and view all the answers

What is the role of van't Hoff factor in osmotic pressure?

It represents the number of ions formed by the solute Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

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 Signup and view all the answers

What is the purpose of facilitated diffusion in a cell?

To allow polar molecules or charged ions to cross the plasma membrane Signup and view all the answers

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 Signup and view all the answers

What is the term for areas in the plasma membrane with high concentrations of cholesterol?

Lipid rafts Signup and view all the answers

What is the driving force behind spontaneous movement of molecules?

The concentration gradient Signup and view all the answers

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 Signup and view all the answers

Which of the following is an example of facilitated diffusion?

Passage of glucose across the plasma membrane Signup and view all the answers

What will happen to a cell placed in a hypertonic solution?

Water will flow out of the cell Signup and view all the answers

What is the term for proteins that span the entire plasma membrane and have both extracellular and intracellular domains?

Transmembrane proteins Signup and view all the answers

Why do prokaryotes not use cholesterol in their plasma membrane?

Because they use hopanoids instead, which provide similar functionality Signup and view all the answers

What is the term for the smallest unit of self-sustainable life?

Cell Signup and view all the answers

What is the result of the hydrolysis of ATP?

ADP + Pi + H2O Signup and view all the answers

What is the primary source of energy for biological reactions?

ATP Signup and view all the answers

What is the function of Na+/K+ ATPase?

To pump 3 Na+ ions out and 2 K+ ions into the cell Signup and view all the answers

What is the purpose of secondary active transport?

To utilize the gradient established by active transport Signup and view all the answers

What type of amino acids would be present in the core of a Ca2+ channel?

Negatively charged or dipole amino acids Signup and view all the answers

What is the process of releasing cellular contents into the extracellular environment?

Exocytosis Signup and view all the answers

What is the energy yield of ATP hydrolysis?

-30 kJ/mol Signup and view all the answers

What is the purpose of active transport?

To use ATP to pump ions against their gradient Signup and view all the answers

What is the primary function of endocytosis in a cell?

To release extracellular molecules into the cell Signup and view all the answers

What type of transport is exocytosis and endocytosis an example of?

Active transport Signup and view all the answers

What is the name of the protein used to create vesicles in exocytosis and endocytosis?

Clathrin Signup and view all the answers

What is the main difference between symport and antiport transportation?

The direction of molecule movement Signup and view all the answers

What is the purpose of symport and antiport transportation?

To move molecules against their concentration gradient Signup and view all the answers

What is the term for vesicles produced in exocytosis?

Exosomes Signup and view all the answers

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.

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Description

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.