PET3322 Exam 1 Review Fall 2014 Chapter 3 Cell Biology and Genetics Basic structure of the cell nucleus cytoplasm containing organelles and a plasma membrane Functions of the cell include cell metabolism and energy use synthesis of molecules communication reproduction and inheritance The plasma membrane separates intracellular and extracellular materials This results in different ion concentrations inside and outside of the cell creating a membrane potential charge difference Glycocalyx combinations of lipids proteins and carbohydrates on outer surface The plasma membrane is made up of a phospholipid bilayer The polar hydrophilic heads of the phospholipids face water in the interior and exterior of the cell while the nonpolar hydrophobic tails face each other on the interior of the membrane Cholesterol is dispersed among the phospholipids and the amount present can determine the fluid nature of the membrane The fluid nature of the membrane allows distribution of molecules throughout the membrane repair of damaged membrane and fusion of membranes Membrane protein types 1 Integral v Extrinsic a Integral intrinsic proteins extend deeply into the membrane often extending from one surface to the other can form channels through the membrane b Extrinsic peripheral proteins attach to integral proteins at either the inner or outer surfaces of the lipid bilayer 2 Can also have specific functions based on 3D shape and chemical characteristics a Marker molecules allow cells to identify one another or other molecules b Attachment proteins i Cadherins attach cells to other cells ii Integrins integral proteins that attach cell to extracellular molecule i Hydrophilic region faces inward charge determines molecules that can pass c Transport proteins through d Channel proteins ii Channel proteins carrier proteins ATP powered pumps i Nongated always open ii Gated can be opened or closed by certain stimuli 1 Ligand gated open in response to small molecules that bind to proteins or glycoproteins 2 Voltage gated open where there is a change in charge across the plasma membrane e Carrier proteins i Integral proteins move ions from one side of the membrane to the other 1 Have specific binding sites 2 Protein changes shape to transport ions or molecules 3 Resumes original shape after transport ii Uniporters iii Symporters iv Antiporters f Receptor proteins i Can attach to specific chemical signal molecules and act as an intercellular communication system ii Ligand can only attach to cells with that specific receptor iii Attachment of receptor specific chemical signals to receptors causes change in shape of channel protein 1 Cystic fibrosis defect in genes causes defects in channel proteins ATP Powered Transport rate of transport depends on concentration of substrate and on concentration of ATP 1 ATP and ion bind to ATP powered pump 2 ATP breaks down into ADP and a phosphate and releases energy which powers the shape change in the ATP powered pump As a result the ion moves across the membrane 3 The ion and phosphate are released from the ATP powered pump The pump resumes its original shape Receptors linked to G protein complexes 1 A G protein complex will only associate with a receptor that has a chemical signal bound to it In its unassociated state the subunit of the G protein complex has GDP attached to it 2 When a chemical signal binds to the receptor the receptor becomes associated with the G protein complex GDP is released from the subunit and a GTP is attached to it 3 The G protein complex separates from the receptor and the subunit separates from the other subunits The subunit stimulates a cell response Enzymes some act to catalyze reactions at outer inner surface of plasma membrane Surface cells of small intestine produce enzymes that digest dipeptides Movement of the membrane occurs through 1 Diffusion a Movement of solutes from high low concentration 2 Osmosis a Diffusion of water solvent across a membrane b Moves from area of low concentration of solute to a high concentration of solute c Osmotic pressure force required to prevent water from moving across a membrane by osmosis Isosmotic solutions with the same concentrations of solute particles i ii Hyperosmotic greater concentration of solute iii Hyposmotic lesser concentration of solute d Large volume changes caused by water movement disrupt normal cell function i e shrinking or swelling Isotonic doesn t shrink or swell i ii Hypertonic cell shrinks crenation iii Hypotonic cell swells lysis 3 Mediated Transport involve carrier proteins or channels in the cell membrane a Characteristics specificity of a single molecule competition among molecules of similar shape saturation rate of transport limited to the number of available carrier proteins b Facilitated diffusion i Passive transport ii Move large water soluble molecules or electrically charged molecules across the plasma membrane 1 Ex amino acids and glucose in manufactured proteins out c Active transport i ATP transport 1 Rate of transport depends on concentration of substrate and concentration of ATP 2 Ex Na K pump a 3 Na ions and ATP bind to the Na K pump b The ATP breaks down to ADP and a phosphate and releases energy That energy is used to power the shape change in the Na K pump c The Na K pump changes shape and the Na are transported across the membrane and into the extracellular fluid d Two K ions bind to the Na K pump e The phosphate is released from the Na K pump binding site The Na K pump changes shape transporting K across the f membrane and into the cytoplasm The Na K pump can again bind to Na and ATP d Secondary active transport Ions move in the same or opposite directions i ii Ex cotransport of Na and glucose Internalization of substances by formation of a vesicle Types are phagocytosis pinocytosis and receptor mediated endocytosis Receptor mediated endocytosis receptors on cell surface bind to molecules to be taken into the cell Receptors and the bound molecules are taken into the cell as the vesicle forms Vesicle fuses and separates from plasma membrane Exocytosis secretory vesicle moves toward the plasma membrane Secretory vesicle fuses with the plasma membrane Secretory vesicle s contents are released into extracellular fluid Cytoplasm composed of cytosol cytoskeleton cytoplasmic inclusions and organelles Cytosol fluid portion Dissolved molecules and colloid Cytoskeleton supports the cell but still allows for movement Microtubules used for internal scaffold transport and
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