Biology Lecture 12 - Exam 3
Biology Lecture 12 - Exam 3 BIO 121 A
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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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