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Biology Lecture 12 - Exam 3

by: Devin Mart

Biology Lecture 12 - Exam 3 BIO 121 A

Marketplace > Missouri State University > Biology > BIO 121 A > Biology Lecture 12 Exam 3
Devin Mart
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The Membrane Structure and Function
General Biology
Dr. Durham
Class Notes
Biology 120 - General Biology
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This 2 page Class Notes was uploaded by Devin Mart on Friday March 25, 2016. The Class Notes belongs to BIO 121 A at Missouri State University taught by Dr. Durham in Spring 2016. Since its upload, it has received 10 views. For similar materials see General Biology in Biology at Missouri State University.


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Date Created: 03/25/16
  Mart 1  Lecture 12: The Membrane Structure and Function    ● The ​ plasma membrane ​ separates and controls traffic into and out of the cell.  ○ The membrane is selectively permeable, consisting of: phospholipids and  amphipathic molecules​ , having both hydrophilic and hydrophobic parts.  ○ The ​ fluid mosaic model ​demonstrates a fluid structure with proteins embedded or  attached to a double layer of phospholipids.  ○ Membrane fluidity is influenced by temperature and by its constituents.  ■ Warm temperature restrains movement and reduces fluidity while cool  temperatures maintain fluidity by preventing tight packing.  ○ Proteins determine most of the membrane’s specific functions, unique proteins are  used for each type of membrane.  ■ Peripheral proteins ​ are loosely bounded to the surface.  ■ Integral proteins ​penetrate the hydrophobic core of the lipid bilayer.  ○ The role of membrane proteins include:  ■ Reinforce the shape of the cell and provide framework.  ■ Connect to the cytoskeleton.  ■ Attach to the extracellular matrix.  ○ Membrane carbohydrates are important for cell to cell recognition, the formation  of tissues and organs, and are the basis for rejection of foreign cells by the  immune system.  ■ These carbohydrates vary from cell to cell within the same individual.  ○ Transport proteins ​ are a protein that serves the function of moving other materials  within an organism.  ● Diffusion ​is the tendency of molecules of any substance to spread out in available space.  ○ A substance will diffuse from where it is more concentrated to where it is less  concentrated, down its concentration gradient.  ○ Passive transport ​ is the diffusion across a biological membrane.  ■ Interactions of molecules with the membrane play a role in the diffusion  rate.  ○ Differences in the relative concentration of dissolved materials in two solutions  can lead to the movement of ions from one to the other.  ■ Hypertonic ​ is a solution having a higher concentration of solutes.  ■ Hypotonic ​ is a solution having a lower concentration of solutes.  ■ Isotonic ​is a solution that has an equal solute concentration.  ○ Osmosis ​ is the diffusion of water across a selectively permeable membrane.  ■ The direction of diffusion is determined by the difference in total solute  concentration, the kinds of solutes don’t matter.  ○ The survival of cells depend on the balancing of water uptake and loss.    Mart 2  ○ Facilitated diffusion​ is a passive movement of molecules down its concentration  gradient via a transport protein.  ● Active transport ​is the movement of ions or molecules across a cell membrane into a  region of higher concentration, assisted by enzymes and requiring energy.  ○ This is critical for cells to maintain its concentrations of small molecules, ATP is  the most common energy for active transport.  ○ A ​ sodium­potassium pump​  is a membrane­bound transporter found in nearly all  mammalian cells that transports potassium ions into the cytoplasm from the  extracellular fluid while simultaneously transporting sodium ions out of the  cytoplasm to the extracellular fluid.  ○ All cells maintain voltage across their plasma membranes: cytoplasm = negative  voltage,membrane potential ​ = ranges from ­50 to ­200 millivolts  ○ An ​ electrochemical gradient​ for an ion that can move across a membrane:  ■ A chemical force based in an ion’s concentration gradient.  ■ An electrical force based on effect of membrane potential on the ion’s  movement.  ○ A p ​roton pump ​ actively transports H out of the cell.  ○ Exocytosis ​ is the release of substances from the cell.  ○ Endocytosis ​ is the taking in of matter by a living cell by invagination of its  membrane to form a vacuole.  ■ Phagocytosis ­ cellular eating  ■ Pinocytosis ­ cellular drinking  ■ Receptor ­ mediated             


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