BSC2085 Final Exam Study Guide “You Should Be Able To” Cumulative Portion 1 Lesson 2: The Cell and the Plasma Membrane Explain the cell theory and who was crucial to its development Cell Theory • Cells are the building blocks of all plants & animals • All cells form from the division of preexisting cells • Cells are the smallest units that perform all vital physiological functions • Each cell maintains homeostasis at the cellular level Cell theory was developed from Robert Hooke’s research – he viewed slices of cork under a light microscope & coined the term “cell” Explain the difference between somatic and germ cells Sex cells are the cells used in reproduction (sperm of males & oocytes of females) Somatic cells include all the other cells in the human body Describe the plasma membrane and explain its general functions Plasma Membrane: The outer boundary of the cell • Four (4) General Functions of the Plasma Membrane: o 1. Physical isolation Physical barrier separating the inside of the cell from the outside environment o 2. Regulation of exchange with environment Can regulate: • Entry of ions & nutrients • Release of wastes & cellular products (by exocytosis) o 3. Sensitivity to the environment Extracellular fluid composition can alter plasma membrane Can detect chemical signals through plasma receptors (proteins) o 4. Structural support Anchors cells and tissues to each other or to the extracellular matrix Provides stability to cells Describe the composition of the plasma membrane. What are the different types of molecules that are found on it? What are their functions? The plasma membrane is composed of membrane lipids & membrane proteins o Membrane Lipids (largest component) Phospholipid Bilayer: Two layers of phospholipids • Hydrophilic heads – toward watery environments on both sides • Hydrophobic fatty-acid tails – inside membrane, away from waterBSC2085 Final Exam Study Guide “You Should Be Able To” Cumulative Portion 2 • Bilayer forms a barrier to ions & water-soluble compounds o Can’t move past the hydrophobic lipid tails o Allows for interior of cell to have a different composition than the extracellular environment o Membrane Proteins (2nd largest component & 55% of the weight of the membrane) Integral Membrane Proteins: Embedded within the membrane • More numerous • Transmembrane Proteins: Traverse the width of the plasma membrane Peripheral Membrane Proteins: Bound to inner or outer surface of the plasma membrane Receptor Proteins: Bind and respond to ligands (ions, hormones) • Binding of the ligand can cause a change within the cell Carrier Proteins: Transport specific solutes through membrane • May/may not require energy (ATP) • Ex) Glucose transport doesn't require energy, but Na+ and Ca2+ transport does Channels: Integral proteins with a central pore • Regulate water flow & solutes through membrane • Many channels are highly specific for a certain ion o Important in nerve impulse conduction & muscle contraction Anchoring Proteins: Stabilize the cell • Attach to inside (cytoskeletal) or outside (extracellular protein fibers or other cells) structures Recognition Proteins: Label cells as normal or abnormal • Prevents immune system from reacting to the cell • Many recognition proteins = glycoproteins Enzymes: Catalyze reactions inside or outside the cell • May be integral or peripheral proteins • Catalyze reactions inside or outside the cell Explain why the plasma membrane is a selectively permeable membrane The plasma membrane is selectively permeable so it can have control over what enters and leaves the cell. To survive, nutrients must be able to get in, while wastes & products must be able to get out. It also allows the cell to bar unwanted chemicals from entering. Describe the different types of transport • Diffusion: The net movement of a substance from an area of higher concentration to an area of lower concentration o Simple Diffusion: Materials diffuse through the phospholipid bilayer (plasma membrane) Alcohol, fatty acids, lipid soluble drugs, dissolved gases (O2 & CO2)BSC2085 Final Exam Study Guide “You Should Be Able To” Cumulative Portion 3 o Channel-Mediated Diffusion: Diffusion through a channel in a transmembrane protein Ions & water soluble compounds Leak/Passive Channels: Always open; allow passage of ions in either direction (in or out) o Osmosis: Diffusion of water across a cell membrane that is freely permeable to water & selectively permeable to solutes from an area of higher H2O/lower solute concentration to an area of lower H2O/higher solute concentration • Carrier-Mediated Transport: Integral proteins bind specific ions or organic substrates and carry them across the plasma membrane o Cotransport/Symport: Carrier transports two substances in the same direction simultaneously, in or out of the cell o Countertransport: One substance moves into the cell and the other moves out o Facilitated Diffusion: Molecule being transported binds to a receptor site on the carrier protein; protein changes shape, moving the molecule across the plasma membrane Glucose & amino acids o Active Transport: A high-energy bond provides the energy needed to move ions or molecules across the membrane Ion Pumps: Carrier proteins that actively transport ions across the plasma membrane Exchange Pumps: Carrier proteins that move more than one kind of ion at the same time by countertransport (in & out of the cell) o Secondary Active Transport: Moves a specific substrate down its concentration gradient and can also move another substrate at the same time against its concentration gradient; ATP needed later to preserve homeostasis What are the factors that affect the transport of substances? Factors that affect the transport of substances include: • Size of the material/molecule • Electrical charge • Molecular shape • Lipid solubility • Temperature • Concentration gradient • Interaction with channel Which types of transport utilize energy? Energy (Active) Active or Passive No Energy (Passive) - Active transport - Ion pumps - Exchange pumps - Secondary active transport - Carrier-mediated transport - Diffusion - Simple diffusion - Channel-mediated diffusion -
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