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BSC 215 Notes Week of 2/1

by: Regan Dougherty

BSC 215 Notes Week of 2/1 BSC 215

Regan Dougherty
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Notes for the week of 2/1
Human Anatomy & Physiology 1
Jason Pienaar
Class Notes




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This 9 page Class Notes was uploaded by Regan Dougherty on Tuesday February 2, 2016. The Class Notes belongs to BSC 215 at University of Alabama - Tuscaloosa taught by Jason Pienaar in Spring 2016. Since its upload, it has received 19 views. For similar materials see Human Anatomy & Physiology 1 in Biology at University of Alabama - Tuscaloosa.

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Date Created: 02/02/16
Tuesday, February 2, 2016 BSC 215 Lecture 6 The Cell Membrane - Cell Theory • 1. All living organism are composed of cells. • 2. The cell is the most basic unit of life. • 3. All cells come from pre-existing cells. - Morphology - shape and size • Cells come in a huge variety of shapes. • Cells vary in size. • Human egg cell = 100 micrometers in diameter • Some nerve cells > 1 meter long - still very thin (need a microscope to see them) • Most human cells are 10-15 micrometers in diameter. • Cell size is limited because of their surface to volume ratio. - The ratio is surface/volume. - Larger surface to volume ratio is more likely. - If the surface to volume ratio is not big enough, the surface may not be able to support the volume of the cell. • transport across membranes • enzymes • greater distance from nucleus to cell membrane (molecules to be exported) - All cells are made of 3 basic components: • Plasma membrane - surrounded by extracellular space/fluid on the outside of the cell • Cytoplasm (intracellular space) 1 Tuesday, February 2, 2016 - Cytosol - liquid part - Organelles are dissolved in the cytosol. • Nucleus - contains double stranded DNA - surrounded by nuclear envelope (double membrane) - Cell Membrane composed of: • - Lipids • phospholipid - fatty acid tails are hydrophobic (not charged) and the phosphate group is hydrophilic (charged) - amphipathic - some parts are hydrophobic and some are hydrophilic - forms a phospholipid bilayer - The fatty acids will be on the inside of the bilayer and the phosphate groups will be on the outside of the bilayer. • cholesterol - Cholesterol molecules are stiffer molecules than phospholipids, so their job is to stiffen the plasma membrane. - More cholesterol = stiffer membrane • 98% of membrane molecules are lipids. - 75% phospholipids. - 20% cholesterol - 5% glycolipids (combination or a sugar-like substance and a lipid-like substance) • carbohydrate covalently liked to a lipid • form part of the glycocalyx (sugar coating) - Proteins • peripheral 2 Tuesday, February 2, 2016 • integrated • Some amino acids are hydrophilic and come are hydrophobic, so proteins are able to interact with both the hydrophilic and hydrophobic parts of the membrane. 2% of membrane molecules are protein (but they make up about 50% of mass) • • Roles of proteins in the cell membrane: - Receptor - bind specific chemical messengers and transmit the signal to the cytoplasm - Enzyme - catalyze reactions • Enzymes require a surface to work on (keeps the enzyme in place). - Channel - allow hydrophilic molecules and water to pass through the membrane - Gated channel - ligand (chemical), voltage, or mechanically gated channel • The channel is closed until it is opened by some sort of stimulus. - Identity marker - glycoproteins distinguish “self” from “non-self” • glycoprotein - carbohydrate and protein that are covalently linked - Cell adhesion molecule (CAM) - cell-cell binding and mechanical connections to extracellular matrix (ECM) - Carbohydrates • Glycocalyx - Glycolipids - Glycoproteins • Unique identifier for cells - immune functions (distinguishing “self” from “non-self” - adhesive functions (allows cells to stick to various things) - Passive Transport - movement across a membrane down a concentration gradient (DOES NOT require energy) • Diffusion - movement of solute down a concentration gradient 3 Tuesday, February 2, 2016 - high concentration to low concentration - Why? kinetic energy of random motion - Diffusion across a membrane • Cell membranes are selectively permeable. - Selectivity is based on: • size charge (Hydrophobic molecules travel through the membrane more easily • than hydrophilic molecules.) • membrane protein specificity • Osmosis - movement of solvent down a concentration gradient 4 Thursday, February 4, 2016 BSC 215 Lecture 6 (continued) The Cell Membrane - Diffusion: Simple vs. Facilitated Simple diffusion - diffusion across the phospholipid part of the membrane • - small molecules • Facilitated diffusion - diffusion through a protein - Still down a concentration gradient (so no energy is required) - Carrier-mediated - protein carrier specific for one chemical; protein changes shape to transport the chemical across the membrane - Channel-mediated - protein channel allows lipid-insoluble small molecules to pass through Factors Affecting Membrane Diffusion Rate • - Temperature - higher temperature means that the particles are moving faster, so they will flow more quickly across the membrane - Molecular mass - larger molecules will diffuse more slowly - Concentration gradient - the bigger the difference in concentration, the faster the molecules will diffuse - Membrane surface area - the larger the membrane surface area, the more space there is for solutes to move into/out of the cell - Membrane permeability - the more permeable the membrane, the faster the rate of diffusion - Osmosis - diffusion of solvent (water) molecules down a concentration gradient • passive transport • Dissolved solutes determine the water concentrations. - Tonicity • Hypertonic - solution with a higher concentration of solute • Hypotonic - solution with a lower concentration of solute 1 Thursday, February 4, 2016 • Isotonic - solutions with equal solute concentrations • **These are relative terms. • Tonicity is important for red blood cells. - RBCs want to be in an isotonic solution. - If the RBC is in a hypotonic solution, it will swell (water will flow into the cell) and the cell will eventually burst. - If the RBC is in a hypertonic solution, it will shrink (water will flow out of the cell). - Aquaporins - channel proteins that allow water to diffuse through • Some water can diffuse across the plasma membrane because it is a small molecule. - But osmosis across a membrane is slightly hindered because water molecules are charged. • You can control osmotic rate by varying the number of aquaporins in the membrane. - Active Transport - transport against a concentration gradient; requires energy • Primary Active Transport - membrane protein uses ATP energy directly to pump against a concentration gradient - ATP has high energy bonds. When you break bonds of ATP, energy is transferred to the protein. The protein changes its shape and transports a substance across the membrane. • Secondary Active Transport - membrane protein uses concentration gradient energy created by a different ATP dependent pump • Vesicular Transport - membrane vesicles bud off of the membrane to transport a large number of molecules • 3 Classes of Protein Pumps - Uniport - transports one thing at a time - Symport - transports 2 or more things in the same direction - Antiport - transports 2 or more things in the opposite direction • Syport and antiport fall under the category of cotransport. 2 Thursday, February 4, 2016 - Sodium Potassium Pump - maintains a high sodium concentration outside the cell; maintains a high potassium concentration inside the cell • found in all animals • Some Roles: - nerve cell signaling - skeletal muscle contraction - heart beat - osmotic balance • antiporter-like activity • ATPase - breaks down ATP to get energy Up to 30% of cellular energy is used for Na/K pumps. • • Sequence of Events - 1. 3 Na+ bind to pump. This stimulates phosphorylation by ATP. - 2. Phosphorylation changes the shape of the pump. This shape change expels the Na+. - 3. 2 K+ bind on the outside of the cell. - 4. K+ triggers phosphate release (dephosphorylation). This causes the protein to revert to its original shape. - 5. The original shape causes K+ release. - 6. Step 1 begins again (it is a cycle). • The sodium potassium pump is an example of primary active transport. - Glucose Symporter • The sodium potassium pump creates an ion gradient. The energy associated with the sodium gradient is used to transport glucose across its concentration gradient. • This is an example of secondary active transport. - Vesicular Transport • Endocytosis - vesicular transport into cell 3 Thursday, February 4, 2016 - Phagocytosis - “cell eating” • ex. white blood cells - Pinocytosis - “cell drinking” - Receptor mediated endocytosis - protein receptors recognize specific molecules that are transported into the cell • ex. intake of LDL cholesterol • Exocytosis - vesicular discharge out of cell 4 Thursday, February 4, 2016 BSC 215 Lecture 7 Cytoskeleton and Organelles - Mitochondria • Power plant of the cell (it makes ATP) • Double membrane - The inner membrane forms cristae (folds). • The function of folds is to increase surface area. - A mitochondrion contains its own genome and its own ribosomes. • This supports the endosymbiotic theory. - Ribosomes • Responsible for protein synthesis • Composed of large and small protein subunits • Every living organism has ribosomes because every living organism needs to make proteins. • Location: - free in cytosol - bound to rough ER or nuclear membranes - Endoplasmic Reticulum - network of cisternae (tubules) continuous with the nuclear membrane • The rough ER is studded with ribosomes. - main jobs: fold proteins, embed proteins into phospholipids (creates prefabricated cell membrane sections). • The smooth ER does not have ribosomes. - main jobs: calcium ion storage (especially in muscle cells), detoxification reactions (especially in the liver), lipid synthesis (phospholipids, cholesterol) 1


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